1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 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-inferiors}} 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-inferiors
2502 @item remove-inferiors @var{infno}@dots{}
2503 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2504 possible to remove an inferior that is running with this command. For
2505 those, use the @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 inferiors}} command:
2515 @kindex detach inferiors @var{infno}@dots{}
2516 @item detach inferior @var{infno}@dots{}
2517 Detach from the inferior or inferiors identified by @value{GDBN}
2518 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2519 still stays on the list of inferiors shown by @code{info inferiors},
2520 but its Description will show @samp{<null>}.
2522 @kindex kill inferiors @var{infno}@dots{}
2523 @item kill inferiors @var{infno}@dots{}
2524 Kill the inferior or inferiors identified by @value{GDBN} inferior
2525 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2526 stays on the list of inferiors shown by @code{info inferiors}, but its
2527 Description will show @samp{<null>}.
2530 After the successful completion of a command such as @code{detach},
2531 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, 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 0x41e02940 (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
2709 @item info threads @r{[}@var{id}@dots{}@r{]}
2710 Display a summary of all threads currently in your program. Optional
2711 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2712 means to print information only about the specified thread or threads.
2713 @value{GDBN} displays for each thread (in this order):
2717 the thread number assigned by @value{GDBN}
2720 the target system's thread identifier (@var{systag})
2723 the thread's name, if one is known. A thread can either be named by
2724 the user (see @code{thread name}, below), or, in some cases, by the
2728 the current stack frame summary for that thread
2732 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2733 indicates the current thread.
2737 @c end table here to get a little more width for example
2740 (@value{GDBP}) info threads
2742 3 process 35 thread 27 0x34e5 in sigpause ()
2743 2 process 35 thread 23 0x34e5 in sigpause ()
2744 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2748 On Solaris, you can display more information about user threads with a
2749 Solaris-specific command:
2752 @item maint info sol-threads
2753 @kindex maint info sol-threads
2754 @cindex thread info (Solaris)
2755 Display info on Solaris user threads.
2759 @kindex thread @var{threadno}
2760 @item thread @var{threadno}
2761 Make thread number @var{threadno} the current thread. The command
2762 argument @var{threadno} is the internal @value{GDBN} thread number, as
2763 shown in the first field of the @samp{info threads} display.
2764 @value{GDBN} responds by displaying the system identifier of the thread
2765 you selected, and its current stack frame summary:
2768 (@value{GDBP}) thread 2
2769 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2770 #0 some_function (ignore=0x0) at example.c:8
2771 8 printf ("hello\n");
2775 As with the @samp{[New @dots{}]} message, the form of the text after
2776 @samp{Switching to} depends on your system's conventions for identifying
2779 @vindex $_thread@r{, convenience variable}
2780 The debugger convenience variable @samp{$_thread} contains the number
2781 of the current thread. You may find this useful in writing breakpoint
2782 conditional expressions, command scripts, and so forth. See
2783 @xref{Convenience Vars,, Convenience Variables}, for general
2784 information on convenience variables.
2786 @kindex thread apply
2787 @cindex apply command to several threads
2788 @item thread apply [@var{threadno} | all] @var{command}
2789 The @code{thread apply} command allows you to apply the named
2790 @var{command} to one or more threads. Specify the numbers of the
2791 threads that you want affected with the command argument
2792 @var{threadno}. It can be a single thread number, one of the numbers
2793 shown in the first field of the @samp{info threads} display; or it
2794 could be a range of thread numbers, as in @code{2-4}. To apply a
2795 command to all threads, type @kbd{thread apply all @var{command}}.
2798 @cindex name a thread
2799 @item thread name [@var{name}]
2800 This command assigns a name to the current thread. If no argument is
2801 given, any existing user-specified name is removed. The thread name
2802 appears in the @samp{info threads} display.
2804 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2805 determine the name of the thread as given by the OS. On these
2806 systems, a name specified with @samp{thread name} will override the
2807 system-give name, and removing the user-specified name will cause
2808 @value{GDBN} to once again display the system-specified name.
2811 @cindex search for a thread
2812 @item thread find [@var{regexp}]
2813 Search for and display thread ids whose name or @var{systag}
2814 matches the supplied regular expression.
2816 As well as being the complement to the @samp{thread name} command,
2817 this command also allows you to identify a thread by its target
2818 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2822 (@value{GDBN}) thread find 26688
2823 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2824 (@value{GDBN}) info thread 4
2826 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2829 @kindex set print thread-events
2830 @cindex print messages on thread start and exit
2831 @item set print thread-events
2832 @itemx set print thread-events on
2833 @itemx set print thread-events off
2834 The @code{set print thread-events} command allows you to enable or
2835 disable printing of messages when @value{GDBN} notices that new threads have
2836 started or that threads have exited. By default, these messages will
2837 be printed if detection of these events is supported by the target.
2838 Note that these messages cannot be disabled on all targets.
2840 @kindex show print thread-events
2841 @item show print thread-events
2842 Show whether messages will be printed when @value{GDBN} detects that threads
2843 have started and exited.
2846 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2847 more information about how @value{GDBN} behaves when you stop and start
2848 programs with multiple threads.
2850 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2851 watchpoints in programs with multiple threads.
2854 @kindex set libthread-db-search-path
2855 @cindex search path for @code{libthread_db}
2856 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2857 If this variable is set, @var{path} is a colon-separated list of
2858 directories @value{GDBN} will use to search for @code{libthread_db}.
2859 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2862 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2863 @code{libthread_db} library to obtain information about threads in the
2864 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2865 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2866 with default system shared library directories, and finally the directory
2867 from which @code{libpthread} was loaded in the inferior process.
2869 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2870 @value{GDBN} attempts to initialize it with the current inferior process.
2871 If this initialization fails (which could happen because of a version
2872 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2873 will unload @code{libthread_db}, and continue with the next directory.
2874 If none of @code{libthread_db} libraries initialize successfully,
2875 @value{GDBN} will issue a warning and thread debugging will be disabled.
2877 Setting @code{libthread-db-search-path} is currently implemented
2878 only on some platforms.
2880 @kindex show libthread-db-search-path
2881 @item show libthread-db-search-path
2882 Display current libthread_db search path.
2884 @kindex set debug libthread-db
2885 @kindex show debug libthread-db
2886 @cindex debugging @code{libthread_db}
2887 @item set debug libthread-db
2888 @itemx show debug libthread-db
2889 Turns on or off display of @code{libthread_db}-related events.
2890 Use @code{1} to enable, @code{0} to disable.
2894 @section Debugging Forks
2896 @cindex fork, debugging programs which call
2897 @cindex multiple processes
2898 @cindex processes, multiple
2899 On most systems, @value{GDBN} has no special support for debugging
2900 programs which create additional processes using the @code{fork}
2901 function. When a program forks, @value{GDBN} will continue to debug the
2902 parent process and the child process will run unimpeded. If you have
2903 set a breakpoint in any code which the child then executes, the child
2904 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2905 will cause it to terminate.
2907 However, if you want to debug the child process there is a workaround
2908 which isn't too painful. Put a call to @code{sleep} in the code which
2909 the child process executes after the fork. It may be useful to sleep
2910 only if a certain environment variable is set, or a certain file exists,
2911 so that the delay need not occur when you don't want to run @value{GDBN}
2912 on the child. While the child is sleeping, use the @code{ps} program to
2913 get its process ID. Then tell @value{GDBN} (a new invocation of
2914 @value{GDBN} if you are also debugging the parent process) to attach to
2915 the child process (@pxref{Attach}). From that point on you can debug
2916 the child process just like any other process which you attached to.
2918 On some systems, @value{GDBN} provides support for debugging programs that
2919 create additional processes using the @code{fork} or @code{vfork} functions.
2920 Currently, the only platforms with this feature are HP-UX (11.x and later
2921 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2923 By default, when a program forks, @value{GDBN} will continue to debug
2924 the parent process and the child process will run unimpeded.
2926 If you want to follow the child process instead of the parent process,
2927 use the command @w{@code{set follow-fork-mode}}.
2930 @kindex set follow-fork-mode
2931 @item set follow-fork-mode @var{mode}
2932 Set the debugger response to a program call of @code{fork} or
2933 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2934 process. The @var{mode} argument can be:
2938 The original process is debugged after a fork. The child process runs
2939 unimpeded. This is the default.
2942 The new process is debugged after a fork. The parent process runs
2947 @kindex show follow-fork-mode
2948 @item show follow-fork-mode
2949 Display the current debugger response to a @code{fork} or @code{vfork} call.
2952 @cindex debugging multiple processes
2953 On Linux, if you want to debug both the parent and child processes, use the
2954 command @w{@code{set detach-on-fork}}.
2957 @kindex set detach-on-fork
2958 @item set detach-on-fork @var{mode}
2959 Tells gdb whether to detach one of the processes after a fork, or
2960 retain debugger control over them both.
2964 The child process (or parent process, depending on the value of
2965 @code{follow-fork-mode}) will be detached and allowed to run
2966 independently. This is the default.
2969 Both processes will be held under the control of @value{GDBN}.
2970 One process (child or parent, depending on the value of
2971 @code{follow-fork-mode}) is debugged as usual, while the other
2976 @kindex show detach-on-fork
2977 @item show detach-on-fork
2978 Show whether detach-on-fork mode is on/off.
2981 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2982 will retain control of all forked processes (including nested forks).
2983 You can list the forked processes under the control of @value{GDBN} by
2984 using the @w{@code{info inferiors}} command, and switch from one fork
2985 to another by using the @code{inferior} command (@pxref{Inferiors and
2986 Programs, ,Debugging Multiple Inferiors and Programs}).
2988 To quit debugging one of the forked processes, you can either detach
2989 from it by using the @w{@code{detach inferiors}} command (allowing it
2990 to run independently), or kill it using the @w{@code{kill inferiors}}
2991 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2994 If you ask to debug a child process and a @code{vfork} is followed by an
2995 @code{exec}, @value{GDBN} executes the new target up to the first
2996 breakpoint in the new target. If you have a breakpoint set on
2997 @code{main} in your original program, the breakpoint will also be set on
2998 the child process's @code{main}.
3000 On some systems, when a child process is spawned by @code{vfork}, you
3001 cannot debug the child or parent until an @code{exec} call completes.
3003 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3004 call executes, the new target restarts. To restart the parent
3005 process, use the @code{file} command with the parent executable name
3006 as its argument. By default, after an @code{exec} call executes,
3007 @value{GDBN} discards the symbols of the previous executable image.
3008 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3012 @kindex set follow-exec-mode
3013 @item set follow-exec-mode @var{mode}
3015 Set debugger response to a program call of @code{exec}. An
3016 @code{exec} call replaces the program image of a process.
3018 @code{follow-exec-mode} can be:
3022 @value{GDBN} creates a new inferior and rebinds the process to this
3023 new inferior. The program the process was running before the
3024 @code{exec} call can be restarted afterwards by restarting the
3030 (@value{GDBP}) info inferiors
3032 Id Description Executable
3035 process 12020 is executing new program: prog2
3036 Program exited normally.
3037 (@value{GDBP}) info inferiors
3038 Id Description Executable
3044 @value{GDBN} keeps the process bound to the same inferior. The new
3045 executable image replaces the previous executable loaded in the
3046 inferior. Restarting the inferior after the @code{exec} call, with
3047 e.g., the @code{run} command, restarts the executable the process was
3048 running after the @code{exec} call. This is the default mode.
3053 (@value{GDBP}) info inferiors
3054 Id Description Executable
3057 process 12020 is executing new program: prog2
3058 Program exited normally.
3059 (@value{GDBP}) info inferiors
3060 Id Description Executable
3067 You can use the @code{catch} command to make @value{GDBN} stop whenever
3068 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3069 Catchpoints, ,Setting Catchpoints}.
3071 @node Checkpoint/Restart
3072 @section Setting a @emph{Bookmark} to Return to Later
3077 @cindex snapshot of a process
3078 @cindex rewind program state
3080 On certain operating systems@footnote{Currently, only
3081 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3082 program's state, called a @dfn{checkpoint}, and come back to it
3085 Returning to a checkpoint effectively undoes everything that has
3086 happened in the program since the @code{checkpoint} was saved. This
3087 includes changes in memory, registers, and even (within some limits)
3088 system state. Effectively, it is like going back in time to the
3089 moment when the checkpoint was saved.
3091 Thus, if you're stepping thru a program and you think you're
3092 getting close to the point where things go wrong, you can save
3093 a checkpoint. Then, if you accidentally go too far and miss
3094 the critical statement, instead of having to restart your program
3095 from the beginning, you can just go back to the checkpoint and
3096 start again from there.
3098 This can be especially useful if it takes a lot of time or
3099 steps to reach the point where you think the bug occurs.
3101 To use the @code{checkpoint}/@code{restart} method of debugging:
3106 Save a snapshot of the debugged program's current execution state.
3107 The @code{checkpoint} command takes no arguments, but each checkpoint
3108 is assigned a small integer id, similar to a breakpoint id.
3110 @kindex info checkpoints
3111 @item info checkpoints
3112 List the checkpoints that have been saved in the current debugging
3113 session. For each checkpoint, the following information will be
3120 @item Source line, or label
3123 @kindex restart @var{checkpoint-id}
3124 @item restart @var{checkpoint-id}
3125 Restore the program state that was saved as checkpoint number
3126 @var{checkpoint-id}. All program variables, registers, stack frames
3127 etc.@: will be returned to the values that they had when the checkpoint
3128 was saved. In essence, gdb will ``wind back the clock'' to the point
3129 in time when the checkpoint was saved.
3131 Note that breakpoints, @value{GDBN} variables, command history etc.
3132 are not affected by restoring a checkpoint. In general, a checkpoint
3133 only restores things that reside in the program being debugged, not in
3136 @kindex delete checkpoint @var{checkpoint-id}
3137 @item delete checkpoint @var{checkpoint-id}
3138 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3142 Returning to a previously saved checkpoint will restore the user state
3143 of the program being debugged, plus a significant subset of the system
3144 (OS) state, including file pointers. It won't ``un-write'' data from
3145 a file, but it will rewind the file pointer to the previous location,
3146 so that the previously written data can be overwritten. For files
3147 opened in read mode, the pointer will also be restored so that the
3148 previously read data can be read again.
3150 Of course, characters that have been sent to a printer (or other
3151 external device) cannot be ``snatched back'', and characters received
3152 from eg.@: a serial device can be removed from internal program buffers,
3153 but they cannot be ``pushed back'' into the serial pipeline, ready to
3154 be received again. Similarly, the actual contents of files that have
3155 been changed cannot be restored (at this time).
3157 However, within those constraints, you actually can ``rewind'' your
3158 program to a previously saved point in time, and begin debugging it
3159 again --- and you can change the course of events so as to debug a
3160 different execution path this time.
3162 @cindex checkpoints and process id
3163 Finally, there is one bit of internal program state that will be
3164 different when you return to a checkpoint --- the program's process
3165 id. Each checkpoint will have a unique process id (or @var{pid}),
3166 and each will be different from the program's original @var{pid}.
3167 If your program has saved a local copy of its process id, this could
3168 potentially pose a problem.
3170 @subsection A Non-obvious Benefit of Using Checkpoints
3172 On some systems such as @sc{gnu}/Linux, address space randomization
3173 is performed on new processes for security reasons. This makes it
3174 difficult or impossible to set a breakpoint, or watchpoint, on an
3175 absolute address if you have to restart the program, since the
3176 absolute location of a symbol will change from one execution to the
3179 A checkpoint, however, is an @emph{identical} copy of a process.
3180 Therefore if you create a checkpoint at (eg.@:) the start of main,
3181 and simply return to that checkpoint instead of restarting the
3182 process, you can avoid the effects of address randomization and
3183 your symbols will all stay in the same place.
3186 @chapter Stopping and Continuing
3188 The principal purposes of using a debugger are so that you can stop your
3189 program before it terminates; or so that, if your program runs into
3190 trouble, you can investigate and find out why.
3192 Inside @value{GDBN}, your program may stop for any of several reasons,
3193 such as a signal, a breakpoint, or reaching a new line after a
3194 @value{GDBN} command such as @code{step}. You may then examine and
3195 change variables, set new breakpoints or remove old ones, and then
3196 continue execution. Usually, the messages shown by @value{GDBN} provide
3197 ample explanation of the status of your program---but you can also
3198 explicitly request this information at any time.
3201 @kindex info program
3203 Display information about the status of your program: whether it is
3204 running or not, what process it is, and why it stopped.
3208 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3209 * Continuing and Stepping:: Resuming execution
3211 * Thread Stops:: Stopping and starting multi-thread programs
3215 @section Breakpoints, Watchpoints, and Catchpoints
3218 A @dfn{breakpoint} makes your program stop whenever a certain point in
3219 the program is reached. For each breakpoint, you can add conditions to
3220 control in finer detail whether your program stops. You can set
3221 breakpoints with the @code{break} command and its variants (@pxref{Set
3222 Breaks, ,Setting Breakpoints}), to specify the place where your program
3223 should stop by line number, function name or exact address in the
3226 On some systems, you can set breakpoints in shared libraries before
3227 the executable is run. There is a minor limitation on HP-UX systems:
3228 you must wait until the executable is run in order to set breakpoints
3229 in shared library routines that are not called directly by the program
3230 (for example, routines that are arguments in a @code{pthread_create}
3234 @cindex data breakpoints
3235 @cindex memory tracing
3236 @cindex breakpoint on memory address
3237 @cindex breakpoint on variable modification
3238 A @dfn{watchpoint} is a special breakpoint that stops your program
3239 when the value of an expression changes. The expression may be a value
3240 of a variable, or it could involve values of one or more variables
3241 combined by operators, such as @samp{a + b}. This is sometimes called
3242 @dfn{data breakpoints}. You must use a different command to set
3243 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3244 from that, you can manage a watchpoint like any other breakpoint: you
3245 enable, disable, and delete both breakpoints and watchpoints using the
3248 You can arrange to have values from your program displayed automatically
3249 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3253 @cindex breakpoint on events
3254 A @dfn{catchpoint} is another special breakpoint that stops your program
3255 when a certain kind of event occurs, such as the throwing of a C@t{++}
3256 exception or the loading of a library. As with watchpoints, you use a
3257 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3258 Catchpoints}), but aside from that, you can manage a catchpoint like any
3259 other breakpoint. (To stop when your program receives a signal, use the
3260 @code{handle} command; see @ref{Signals, ,Signals}.)
3262 @cindex breakpoint numbers
3263 @cindex numbers for breakpoints
3264 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3265 catchpoint when you create it; these numbers are successive integers
3266 starting with one. In many of the commands for controlling various
3267 features of breakpoints you use the breakpoint number to say which
3268 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3269 @dfn{disabled}; if disabled, it has no effect on your program until you
3272 @cindex breakpoint ranges
3273 @cindex ranges of breakpoints
3274 Some @value{GDBN} commands accept a range of breakpoints on which to
3275 operate. A breakpoint range is either a single breakpoint number, like
3276 @samp{5}, or two such numbers, in increasing order, separated by a
3277 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3278 all breakpoints in that range are operated on.
3281 * Set Breaks:: Setting breakpoints
3282 * Set Watchpoints:: Setting watchpoints
3283 * Set Catchpoints:: Setting catchpoints
3284 * Delete Breaks:: Deleting breakpoints
3285 * Disabling:: Disabling breakpoints
3286 * Conditions:: Break conditions
3287 * Break Commands:: Breakpoint command lists
3288 * Save Breakpoints:: How to save breakpoints in a file
3289 * Error in Breakpoints:: ``Cannot insert breakpoints''
3290 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3294 @subsection Setting Breakpoints
3296 @c FIXME LMB what does GDB do if no code on line of breakpt?
3297 @c consider in particular declaration with/without initialization.
3299 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3302 @kindex b @r{(@code{break})}
3303 @vindex $bpnum@r{, convenience variable}
3304 @cindex latest breakpoint
3305 Breakpoints are set with the @code{break} command (abbreviated
3306 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3307 number of the breakpoint you've set most recently; see @ref{Convenience
3308 Vars,, Convenience Variables}, for a discussion of what you can do with
3309 convenience variables.
3312 @item break @var{location}
3313 Set a breakpoint at the given @var{location}, which can specify a
3314 function name, a line number, or an address of an instruction.
3315 (@xref{Specify Location}, for a list of all the possible ways to
3316 specify a @var{location}.) The breakpoint will stop your program just
3317 before it executes any of the code in the specified @var{location}.
3319 When using source languages that permit overloading of symbols, such as
3320 C@t{++}, a function name may refer to more than one possible place to break.
3321 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3324 It is also possible to insert a breakpoint that will stop the program
3325 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3326 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3329 When called without any arguments, @code{break} sets a breakpoint at
3330 the next instruction to be executed in the selected stack frame
3331 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3332 innermost, this makes your program stop as soon as control
3333 returns to that frame. This is similar to the effect of a
3334 @code{finish} command in the frame inside the selected frame---except
3335 that @code{finish} does not leave an active breakpoint. If you use
3336 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3337 the next time it reaches the current location; this may be useful
3340 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3341 least one instruction has been executed. If it did not do this, you
3342 would be unable to proceed past a breakpoint without first disabling the
3343 breakpoint. This rule applies whether or not the breakpoint already
3344 existed when your program stopped.
3346 @item break @dots{} if @var{cond}
3347 Set a breakpoint with condition @var{cond}; evaluate the expression
3348 @var{cond} each time the breakpoint is reached, and stop only if the
3349 value is nonzero---that is, if @var{cond} evaluates as true.
3350 @samp{@dots{}} stands for one of the possible arguments described
3351 above (or no argument) specifying where to break. @xref{Conditions,
3352 ,Break Conditions}, for more information on breakpoint conditions.
3355 @item tbreak @var{args}
3356 Set a breakpoint enabled only for one stop. @var{args} are the
3357 same as for the @code{break} command, and the breakpoint is set in the same
3358 way, but the breakpoint is automatically deleted after the first time your
3359 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3362 @cindex hardware breakpoints
3363 @item hbreak @var{args}
3364 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3365 @code{break} command and the breakpoint is set in the same way, but the
3366 breakpoint requires hardware support and some target hardware may not
3367 have this support. The main purpose of this is EPROM/ROM code
3368 debugging, so you can set a breakpoint at an instruction without
3369 changing the instruction. This can be used with the new trap-generation
3370 provided by SPARClite DSU and most x86-based targets. These targets
3371 will generate traps when a program accesses some data or instruction
3372 address that is assigned to the debug registers. However the hardware
3373 breakpoint registers can take a limited number of breakpoints. For
3374 example, on the DSU, only two data breakpoints can be set at a time, and
3375 @value{GDBN} will reject this command if more than two are used. Delete
3376 or disable unused hardware breakpoints before setting new ones
3377 (@pxref{Disabling, ,Disabling Breakpoints}).
3378 @xref{Conditions, ,Break Conditions}.
3379 For remote targets, you can restrict the number of hardware
3380 breakpoints @value{GDBN} will use, see @ref{set remote
3381 hardware-breakpoint-limit}.
3384 @item thbreak @var{args}
3385 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3386 are the same as for the @code{hbreak} command and the breakpoint is set in
3387 the same way. However, like the @code{tbreak} command,
3388 the breakpoint is automatically deleted after the
3389 first time your program stops there. Also, like the @code{hbreak}
3390 command, the breakpoint requires hardware support and some target hardware
3391 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3392 See also @ref{Conditions, ,Break Conditions}.
3395 @cindex regular expression
3396 @cindex breakpoints at functions matching a regexp
3397 @cindex set breakpoints in many functions
3398 @item rbreak @var{regex}
3399 Set breakpoints on all functions matching the regular expression
3400 @var{regex}. This command sets an unconditional breakpoint on all
3401 matches, printing a list of all breakpoints it set. Once these
3402 breakpoints are set, they are treated just like the breakpoints set with
3403 the @code{break} command. You can delete them, disable them, or make
3404 them conditional the same way as any other breakpoint.
3406 The syntax of the regular expression is the standard one used with tools
3407 like @file{grep}. Note that this is different from the syntax used by
3408 shells, so for instance @code{foo*} matches all functions that include
3409 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3410 @code{.*} leading and trailing the regular expression you supply, so to
3411 match only functions that begin with @code{foo}, use @code{^foo}.
3413 @cindex non-member C@t{++} functions, set breakpoint in
3414 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3415 breakpoints on overloaded functions that are not members of any special
3418 @cindex set breakpoints on all functions
3419 The @code{rbreak} command can be used to set breakpoints in
3420 @strong{all} the functions in a program, like this:
3423 (@value{GDBP}) rbreak .
3426 @item rbreak @var{file}:@var{regex}
3427 If @code{rbreak} is called with a filename qualification, it limits
3428 the search for functions matching the given regular expression to the
3429 specified @var{file}. This can be used, for example, to set breakpoints on
3430 every function in a given file:
3433 (@value{GDBP}) rbreak file.c:.
3436 The colon separating the filename qualifier from the regex may
3437 optionally be surrounded by spaces.
3439 @kindex info breakpoints
3440 @cindex @code{$_} and @code{info breakpoints}
3441 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3442 @itemx info break @r{[}@var{n}@dots{}@r{]}
3443 Print a table of all breakpoints, watchpoints, and catchpoints set and
3444 not deleted. Optional argument @var{n} means print information only
3445 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3446 For each breakpoint, following columns are printed:
3449 @item Breakpoint Numbers
3451 Breakpoint, watchpoint, or catchpoint.
3453 Whether the breakpoint is marked to be disabled or deleted when hit.
3454 @item Enabled or Disabled
3455 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3456 that are not enabled.
3458 Where the breakpoint is in your program, as a memory address. For a
3459 pending breakpoint whose address is not yet known, this field will
3460 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3461 library that has the symbol or line referred by breakpoint is loaded.
3462 See below for details. A breakpoint with several locations will
3463 have @samp{<MULTIPLE>} in this field---see below for details.
3465 Where the breakpoint is in the source for your program, as a file and
3466 line number. For a pending breakpoint, the original string passed to
3467 the breakpoint command will be listed as it cannot be resolved until
3468 the appropriate shared library is loaded in the future.
3472 If a breakpoint is conditional, @code{info break} shows the condition on
3473 the line following the affected breakpoint; breakpoint commands, if any,
3474 are listed after that. A pending breakpoint is allowed to have a condition
3475 specified for it. The condition is not parsed for validity until a shared
3476 library is loaded that allows the pending breakpoint to resolve to a
3480 @code{info break} with a breakpoint
3481 number @var{n} as argument lists only that breakpoint. The
3482 convenience variable @code{$_} and the default examining-address for
3483 the @code{x} command are set to the address of the last breakpoint
3484 listed (@pxref{Memory, ,Examining Memory}).
3487 @code{info break} displays a count of the number of times the breakpoint
3488 has been hit. This is especially useful in conjunction with the
3489 @code{ignore} command. You can ignore a large number of breakpoint
3490 hits, look at the breakpoint info to see how many times the breakpoint
3491 was hit, and then run again, ignoring one less than that number. This
3492 will get you quickly to the last hit of that breakpoint.
3495 @value{GDBN} allows you to set any number of breakpoints at the same place in
3496 your program. There is nothing silly or meaningless about this. When
3497 the breakpoints are conditional, this is even useful
3498 (@pxref{Conditions, ,Break Conditions}).
3500 @cindex multiple locations, breakpoints
3501 @cindex breakpoints, multiple locations
3502 It is possible that a breakpoint corresponds to several locations
3503 in your program. Examples of this situation are:
3507 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3508 instances of the function body, used in different cases.
3511 For a C@t{++} template function, a given line in the function can
3512 correspond to any number of instantiations.
3515 For an inlined function, a given source line can correspond to
3516 several places where that function is inlined.
3519 In all those cases, @value{GDBN} will insert a breakpoint at all
3520 the relevant locations@footnote{
3521 As of this writing, multiple-location breakpoints work only if there's
3522 line number information for all the locations. This means that they
3523 will generally not work in system libraries, unless you have debug
3524 info with line numbers for them.}.
3526 A breakpoint with multiple locations is displayed in the breakpoint
3527 table using several rows---one header row, followed by one row for
3528 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3529 address column. The rows for individual locations contain the actual
3530 addresses for locations, and show the functions to which those
3531 locations belong. The number column for a location is of the form
3532 @var{breakpoint-number}.@var{location-number}.
3537 Num Type Disp Enb Address What
3538 1 breakpoint keep y <MULTIPLE>
3540 breakpoint already hit 1 time
3541 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3542 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3545 Each location can be individually enabled or disabled by passing
3546 @var{breakpoint-number}.@var{location-number} as argument to the
3547 @code{enable} and @code{disable} commands. Note that you cannot
3548 delete the individual locations from the list, you can only delete the
3549 entire list of locations that belong to their parent breakpoint (with
3550 the @kbd{delete @var{num}} command, where @var{num} is the number of
3551 the parent breakpoint, 1 in the above example). Disabling or enabling
3552 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3553 that belong to that breakpoint.
3555 @cindex pending breakpoints
3556 It's quite common to have a breakpoint inside a shared library.
3557 Shared libraries can be loaded and unloaded explicitly,
3558 and possibly repeatedly, as the program is executed. To support
3559 this use case, @value{GDBN} updates breakpoint locations whenever
3560 any shared library is loaded or unloaded. Typically, you would
3561 set a breakpoint in a shared library at the beginning of your
3562 debugging session, when the library is not loaded, and when the
3563 symbols from the library are not available. When you try to set
3564 breakpoint, @value{GDBN} will ask you if you want to set
3565 a so called @dfn{pending breakpoint}---breakpoint whose address
3566 is not yet resolved.
3568 After the program is run, whenever a new shared library is loaded,
3569 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3570 shared library contains the symbol or line referred to by some
3571 pending breakpoint, that breakpoint is resolved and becomes an
3572 ordinary breakpoint. When a library is unloaded, all breakpoints
3573 that refer to its symbols or source lines become pending again.
3575 This logic works for breakpoints with multiple locations, too. For
3576 example, if you have a breakpoint in a C@t{++} template function, and
3577 a newly loaded shared library has an instantiation of that template,
3578 a new location is added to the list of locations for the breakpoint.
3580 Except for having unresolved address, pending breakpoints do not
3581 differ from regular breakpoints. You can set conditions or commands,
3582 enable and disable them and perform other breakpoint operations.
3584 @value{GDBN} provides some additional commands for controlling what
3585 happens when the @samp{break} command cannot resolve breakpoint
3586 address specification to an address:
3588 @kindex set breakpoint pending
3589 @kindex show breakpoint pending
3591 @item set breakpoint pending auto
3592 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3593 location, it queries you whether a pending breakpoint should be created.
3595 @item set breakpoint pending on
3596 This indicates that an unrecognized breakpoint location should automatically
3597 result in a pending breakpoint being created.
3599 @item set breakpoint pending off
3600 This indicates that pending breakpoints are not to be created. Any
3601 unrecognized breakpoint location results in an error. This setting does
3602 not affect any pending breakpoints previously created.
3604 @item show breakpoint pending
3605 Show the current behavior setting for creating pending breakpoints.
3608 The settings above only affect the @code{break} command and its
3609 variants. Once breakpoint is set, it will be automatically updated
3610 as shared libraries are loaded and unloaded.
3612 @cindex automatic hardware breakpoints
3613 For some targets, @value{GDBN} can automatically decide if hardware or
3614 software breakpoints should be used, depending on whether the
3615 breakpoint address is read-only or read-write. This applies to
3616 breakpoints set with the @code{break} command as well as to internal
3617 breakpoints set by commands like @code{next} and @code{finish}. For
3618 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3621 You can control this automatic behaviour with the following commands::
3623 @kindex set breakpoint auto-hw
3624 @kindex show breakpoint auto-hw
3626 @item set breakpoint auto-hw on
3627 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3628 will try to use the target memory map to decide if software or hardware
3629 breakpoint must be used.
3631 @item set breakpoint auto-hw off
3632 This indicates @value{GDBN} should not automatically select breakpoint
3633 type. If the target provides a memory map, @value{GDBN} will warn when
3634 trying to set software breakpoint at a read-only address.
3637 @value{GDBN} normally implements breakpoints by replacing the program code
3638 at the breakpoint address with a special instruction, which, when
3639 executed, given control to the debugger. By default, the program
3640 code is so modified only when the program is resumed. As soon as
3641 the program stops, @value{GDBN} restores the original instructions. This
3642 behaviour guards against leaving breakpoints inserted in the
3643 target should gdb abrubptly disconnect. However, with slow remote
3644 targets, inserting and removing breakpoint can reduce the performance.
3645 This behavior can be controlled with the following commands::
3647 @kindex set breakpoint always-inserted
3648 @kindex show breakpoint always-inserted
3650 @item set breakpoint always-inserted off
3651 All breakpoints, including newly added by the user, are inserted in
3652 the target only when the target is resumed. All breakpoints are
3653 removed from the target when it stops.
3655 @item set breakpoint always-inserted on
3656 Causes all breakpoints to be inserted in the target at all times. If
3657 the user adds a new breakpoint, or changes an existing breakpoint, the
3658 breakpoints in the target are updated immediately. A breakpoint is
3659 removed from the target only when breakpoint itself is removed.
3661 @cindex non-stop mode, and @code{breakpoint always-inserted}
3662 @item set breakpoint always-inserted auto
3663 This is the default mode. If @value{GDBN} is controlling the inferior
3664 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3665 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3666 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3667 @code{breakpoint always-inserted} mode is off.
3670 @cindex negative breakpoint numbers
3671 @cindex internal @value{GDBN} breakpoints
3672 @value{GDBN} itself sometimes sets breakpoints in your program for
3673 special purposes, such as proper handling of @code{longjmp} (in C
3674 programs). These internal breakpoints are assigned negative numbers,
3675 starting with @code{-1}; @samp{info breakpoints} does not display them.
3676 You can see these breakpoints with the @value{GDBN} maintenance command
3677 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3680 @node Set Watchpoints
3681 @subsection Setting Watchpoints
3683 @cindex setting watchpoints
3684 You can use a watchpoint to stop execution whenever the value of an
3685 expression changes, without having to predict a particular place where
3686 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3687 The expression may be as simple as the value of a single variable, or
3688 as complex as many variables combined by operators. Examples include:
3692 A reference to the value of a single variable.
3695 An address cast to an appropriate data type. For example,
3696 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3697 address (assuming an @code{int} occupies 4 bytes).
3700 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3701 expression can use any operators valid in the program's native
3702 language (@pxref{Languages}).
3705 You can set a watchpoint on an expression even if the expression can
3706 not be evaluated yet. For instance, you can set a watchpoint on
3707 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3708 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3709 the expression produces a valid value. If the expression becomes
3710 valid in some other way than changing a variable (e.g.@: if the memory
3711 pointed to by @samp{*global_ptr} becomes readable as the result of a
3712 @code{malloc} call), @value{GDBN} may not stop until the next time
3713 the expression changes.
3715 @cindex software watchpoints
3716 @cindex hardware watchpoints
3717 Depending on your system, watchpoints may be implemented in software or
3718 hardware. @value{GDBN} does software watchpointing by single-stepping your
3719 program and testing the variable's value each time, which is hundreds of
3720 times slower than normal execution. (But this may still be worth it, to
3721 catch errors where you have no clue what part of your program is the
3724 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3725 x86-based targets, @value{GDBN} includes support for hardware
3726 watchpoints, which do not slow down the running of your program.
3730 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3731 Set a watchpoint for an expression. @value{GDBN} will break when the
3732 expression @var{expr} is written into by the program and its value
3733 changes. The simplest (and the most popular) use of this command is
3734 to watch the value of a single variable:
3737 (@value{GDBP}) watch foo
3740 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3741 clause, @value{GDBN} breaks only when the thread identified by
3742 @var{threadnum} changes the value of @var{expr}. If any other threads
3743 change the value of @var{expr}, @value{GDBN} will not break. Note
3744 that watchpoints restricted to a single thread in this way only work
3745 with Hardware Watchpoints.
3747 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3748 (see below). The @code{-location} argument tells @value{GDBN} to
3749 instead watch the memory referred to by @var{expr}. In this case,
3750 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3751 and watch the memory at that address. The type of the result is used
3752 to determine the size of the watched memory. If the expression's
3753 result does not have an address, then @value{GDBN} will print an
3757 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3758 Set a watchpoint that will break when the value of @var{expr} is read
3762 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3763 Set a watchpoint that will break when @var{expr} is either read from
3764 or written into by the program.
3766 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3767 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3768 This command prints a list of watchpoints, using the same format as
3769 @code{info break} (@pxref{Set Breaks}).
3772 If you watch for a change in a numerically entered address you need to
3773 dereference it, as the address itself is just a constant number which will
3774 never change. @value{GDBN} refuses to create a watchpoint that watches
3775 a never-changing value:
3778 (@value{GDBP}) watch 0x600850
3779 Cannot watch constant value 0x600850.
3780 (@value{GDBP}) watch *(int *) 0x600850
3781 Watchpoint 1: *(int *) 6293584
3784 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3785 watchpoints execute very quickly, and the debugger reports a change in
3786 value at the exact instruction where the change occurs. If @value{GDBN}
3787 cannot set a hardware watchpoint, it sets a software watchpoint, which
3788 executes more slowly and reports the change in value at the next
3789 @emph{statement}, not the instruction, after the change occurs.
3791 @cindex use only software watchpoints
3792 You can force @value{GDBN} to use only software watchpoints with the
3793 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3794 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3795 the underlying system supports them. (Note that hardware-assisted
3796 watchpoints that were set @emph{before} setting
3797 @code{can-use-hw-watchpoints} to zero will still use the hardware
3798 mechanism of watching expression values.)
3801 @item set can-use-hw-watchpoints
3802 @kindex set can-use-hw-watchpoints
3803 Set whether or not to use hardware watchpoints.
3805 @item show can-use-hw-watchpoints
3806 @kindex show can-use-hw-watchpoints
3807 Show the current mode of using hardware watchpoints.
3810 For remote targets, you can restrict the number of hardware
3811 watchpoints @value{GDBN} will use, see @ref{set remote
3812 hardware-breakpoint-limit}.
3814 When you issue the @code{watch} command, @value{GDBN} reports
3817 Hardware watchpoint @var{num}: @var{expr}
3821 if it was able to set a hardware watchpoint.
3823 Currently, the @code{awatch} and @code{rwatch} commands can only set
3824 hardware watchpoints, because accesses to data that don't change the
3825 value of the watched expression cannot be detected without examining
3826 every instruction as it is being executed, and @value{GDBN} does not do
3827 that currently. If @value{GDBN} finds that it is unable to set a
3828 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3829 will print a message like this:
3832 Expression cannot be implemented with read/access watchpoint.
3835 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3836 data type of the watched expression is wider than what a hardware
3837 watchpoint on the target machine can handle. For example, some systems
3838 can only watch regions that are up to 4 bytes wide; on such systems you
3839 cannot set hardware watchpoints for an expression that yields a
3840 double-precision floating-point number (which is typically 8 bytes
3841 wide). As a work-around, it might be possible to break the large region
3842 into a series of smaller ones and watch them with separate watchpoints.
3844 If you set too many hardware watchpoints, @value{GDBN} might be unable
3845 to insert all of them when you resume the execution of your program.
3846 Since the precise number of active watchpoints is unknown until such
3847 time as the program is about to be resumed, @value{GDBN} might not be
3848 able to warn you about this when you set the watchpoints, and the
3849 warning will be printed only when the program is resumed:
3852 Hardware watchpoint @var{num}: Could not insert watchpoint
3856 If this happens, delete or disable some of the watchpoints.
3858 Watching complex expressions that reference many variables can also
3859 exhaust the resources available for hardware-assisted watchpoints.
3860 That's because @value{GDBN} needs to watch every variable in the
3861 expression with separately allocated resources.
3863 If you call a function interactively using @code{print} or @code{call},
3864 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3865 kind of breakpoint or the call completes.
3867 @value{GDBN} automatically deletes watchpoints that watch local
3868 (automatic) variables, or expressions that involve such variables, when
3869 they go out of scope, that is, when the execution leaves the block in
3870 which these variables were defined. In particular, when the program
3871 being debugged terminates, @emph{all} local variables go out of scope,
3872 and so only watchpoints that watch global variables remain set. If you
3873 rerun the program, you will need to set all such watchpoints again. One
3874 way of doing that would be to set a code breakpoint at the entry to the
3875 @code{main} function and when it breaks, set all the watchpoints.
3877 @cindex watchpoints and threads
3878 @cindex threads and watchpoints
3879 In multi-threaded programs, watchpoints will detect changes to the
3880 watched expression from every thread.
3883 @emph{Warning:} In multi-threaded programs, software watchpoints
3884 have only limited usefulness. If @value{GDBN} creates a software
3885 watchpoint, it can only watch the value of an expression @emph{in a
3886 single thread}. If you are confident that the expression can only
3887 change due to the current thread's activity (and if you are also
3888 confident that no other thread can become current), then you can use
3889 software watchpoints as usual. However, @value{GDBN} may not notice
3890 when a non-current thread's activity changes the expression. (Hardware
3891 watchpoints, in contrast, watch an expression in all threads.)
3894 @xref{set remote hardware-watchpoint-limit}.
3896 @node Set Catchpoints
3897 @subsection Setting Catchpoints
3898 @cindex catchpoints, setting
3899 @cindex exception handlers
3900 @cindex event handling
3902 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3903 kinds of program events, such as C@t{++} exceptions or the loading of a
3904 shared library. Use the @code{catch} command to set a catchpoint.
3908 @item catch @var{event}
3909 Stop when @var{event} occurs. @var{event} can be any of the following:
3912 @cindex stop on C@t{++} exceptions
3913 The throwing of a C@t{++} exception.
3916 The catching of a C@t{++} exception.
3919 @cindex Ada exception catching
3920 @cindex catch Ada exceptions
3921 An Ada exception being raised. If an exception name is specified
3922 at the end of the command (eg @code{catch exception Program_Error}),
3923 the debugger will stop only when this specific exception is raised.
3924 Otherwise, the debugger stops execution when any Ada exception is raised.
3926 When inserting an exception catchpoint on a user-defined exception whose
3927 name is identical to one of the exceptions defined by the language, the
3928 fully qualified name must be used as the exception name. Otherwise,
3929 @value{GDBN} will assume that it should stop on the pre-defined exception
3930 rather than the user-defined one. For instance, assuming an exception
3931 called @code{Constraint_Error} is defined in package @code{Pck}, then
3932 the command to use to catch such exceptions is @kbd{catch exception
3933 Pck.Constraint_Error}.
3935 @item exception unhandled
3936 An exception that was raised but is not handled by the program.
3939 A failed Ada assertion.
3942 @cindex break on fork/exec
3943 A call to @code{exec}. This is currently only available for HP-UX
3947 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3948 @cindex break on a system call.
3949 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3950 syscall is a mechanism for application programs to request a service
3951 from the operating system (OS) or one of the OS system services.
3952 @value{GDBN} can catch some or all of the syscalls issued by the
3953 debuggee, and show the related information for each syscall. If no
3954 argument is specified, calls to and returns from all system calls
3957 @var{name} can be any system call name that is valid for the
3958 underlying OS. Just what syscalls are valid depends on the OS. On
3959 GNU and Unix systems, you can find the full list of valid syscall
3960 names on @file{/usr/include/asm/unistd.h}.
3962 @c For MS-Windows, the syscall names and the corresponding numbers
3963 @c can be found, e.g., on this URL:
3964 @c http://www.metasploit.com/users/opcode/syscalls.html
3965 @c but we don't support Windows syscalls yet.
3967 Normally, @value{GDBN} knows in advance which syscalls are valid for
3968 each OS, so you can use the @value{GDBN} command-line completion
3969 facilities (@pxref{Completion,, command completion}) to list the
3972 You may also specify the system call numerically. A syscall's
3973 number is the value passed to the OS's syscall dispatcher to
3974 identify the requested service. When you specify the syscall by its
3975 name, @value{GDBN} uses its database of syscalls to convert the name
3976 into the corresponding numeric code, but using the number directly
3977 may be useful if @value{GDBN}'s database does not have the complete
3978 list of syscalls on your system (e.g., because @value{GDBN} lags
3979 behind the OS upgrades).
3981 The example below illustrates how this command works if you don't provide
3985 (@value{GDBP}) catch syscall
3986 Catchpoint 1 (syscall)
3988 Starting program: /tmp/catch-syscall
3990 Catchpoint 1 (call to syscall 'close'), \
3991 0xffffe424 in __kernel_vsyscall ()
3995 Catchpoint 1 (returned from syscall 'close'), \
3996 0xffffe424 in __kernel_vsyscall ()
4000 Here is an example of catching a system call by name:
4003 (@value{GDBP}) catch syscall chroot
4004 Catchpoint 1 (syscall 'chroot' [61])
4006 Starting program: /tmp/catch-syscall
4008 Catchpoint 1 (call to syscall 'chroot'), \
4009 0xffffe424 in __kernel_vsyscall ()
4013 Catchpoint 1 (returned from syscall 'chroot'), \
4014 0xffffe424 in __kernel_vsyscall ()
4018 An example of specifying a system call numerically. In the case
4019 below, the syscall number has a corresponding entry in the XML
4020 file, so @value{GDBN} finds its name and prints it:
4023 (@value{GDBP}) catch syscall 252
4024 Catchpoint 1 (syscall(s) 'exit_group')
4026 Starting program: /tmp/catch-syscall
4028 Catchpoint 1 (call to syscall 'exit_group'), \
4029 0xffffe424 in __kernel_vsyscall ()
4033 Program exited normally.
4037 However, there can be situations when there is no corresponding name
4038 in XML file for that syscall number. In this case, @value{GDBN} prints
4039 a warning message saying that it was not able to find the syscall name,
4040 but the catchpoint will be set anyway. See the example below:
4043 (@value{GDBP}) catch syscall 764
4044 warning: The number '764' does not represent a known syscall.
4045 Catchpoint 2 (syscall 764)
4049 If you configure @value{GDBN} using the @samp{--without-expat} option,
4050 it will not be able to display syscall names. Also, if your
4051 architecture does not have an XML file describing its system calls,
4052 you will not be able to see the syscall names. It is important to
4053 notice that these two features are used for accessing the syscall
4054 name database. In either case, you will see a warning like this:
4057 (@value{GDBP}) catch syscall
4058 warning: Could not open "syscalls/i386-linux.xml"
4059 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4060 GDB will not be able to display syscall names.
4061 Catchpoint 1 (syscall)
4065 Of course, the file name will change depending on your architecture and system.
4067 Still using the example above, you can also try to catch a syscall by its
4068 number. In this case, you would see something like:
4071 (@value{GDBP}) catch syscall 252
4072 Catchpoint 1 (syscall(s) 252)
4075 Again, in this case @value{GDBN} would not be able to display syscall's names.
4078 A call to @code{fork}. This is currently only available for HP-UX
4082 A call to @code{vfork}. This is currently only available for HP-UX
4087 @item tcatch @var{event}
4088 Set a catchpoint that is enabled only for one stop. The catchpoint is
4089 automatically deleted after the first time the event is caught.
4093 Use the @code{info break} command to list the current catchpoints.
4095 There are currently some limitations to C@t{++} exception handling
4096 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4100 If you call a function interactively, @value{GDBN} normally returns
4101 control to you when the function has finished executing. If the call
4102 raises an exception, however, the call may bypass the mechanism that
4103 returns control to you and cause your program either to abort or to
4104 simply continue running until it hits a breakpoint, catches a signal
4105 that @value{GDBN} is listening for, or exits. This is the case even if
4106 you set a catchpoint for the exception; catchpoints on exceptions are
4107 disabled within interactive calls.
4110 You cannot raise an exception interactively.
4113 You cannot install an exception handler interactively.
4116 @cindex raise exceptions
4117 Sometimes @code{catch} is not the best way to debug exception handling:
4118 if you need to know exactly where an exception is raised, it is better to
4119 stop @emph{before} the exception handler is called, since that way you
4120 can see the stack before any unwinding takes place. If you set a
4121 breakpoint in an exception handler instead, it may not be easy to find
4122 out where the exception was raised.
4124 To stop just before an exception handler is called, you need some
4125 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4126 raised by calling a library function named @code{__raise_exception}
4127 which has the following ANSI C interface:
4130 /* @var{addr} is where the exception identifier is stored.
4131 @var{id} is the exception identifier. */
4132 void __raise_exception (void **addr, void *id);
4136 To make the debugger catch all exceptions before any stack
4137 unwinding takes place, set a breakpoint on @code{__raise_exception}
4138 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4140 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4141 that depends on the value of @var{id}, you can stop your program when
4142 a specific exception is raised. You can use multiple conditional
4143 breakpoints to stop your program when any of a number of exceptions are
4148 @subsection Deleting Breakpoints
4150 @cindex clearing breakpoints, watchpoints, catchpoints
4151 @cindex deleting breakpoints, watchpoints, catchpoints
4152 It is often necessary to eliminate a breakpoint, watchpoint, or
4153 catchpoint once it has done its job and you no longer want your program
4154 to stop there. This is called @dfn{deleting} the breakpoint. A
4155 breakpoint that has been deleted no longer exists; it is forgotten.
4157 With the @code{clear} command you can delete breakpoints according to
4158 where they are in your program. With the @code{delete} command you can
4159 delete individual breakpoints, watchpoints, or catchpoints by specifying
4160 their breakpoint numbers.
4162 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4163 automatically ignores breakpoints on the first instruction to be executed
4164 when you continue execution without changing the execution address.
4169 Delete any breakpoints at the next instruction to be executed in the
4170 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4171 the innermost frame is selected, this is a good way to delete a
4172 breakpoint where your program just stopped.
4174 @item clear @var{location}
4175 Delete any breakpoints set at the specified @var{location}.
4176 @xref{Specify Location}, for the various forms of @var{location}; the
4177 most useful ones are listed below:
4180 @item clear @var{function}
4181 @itemx clear @var{filename}:@var{function}
4182 Delete any breakpoints set at entry to the named @var{function}.
4184 @item clear @var{linenum}
4185 @itemx clear @var{filename}:@var{linenum}
4186 Delete any breakpoints set at or within the code of the specified
4187 @var{linenum} of the specified @var{filename}.
4190 @cindex delete breakpoints
4192 @kindex d @r{(@code{delete})}
4193 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4194 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4195 ranges specified as arguments. If no argument is specified, delete all
4196 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4197 confirm off}). You can abbreviate this command as @code{d}.
4201 @subsection Disabling Breakpoints
4203 @cindex enable/disable a breakpoint
4204 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4205 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4206 it had been deleted, but remembers the information on the breakpoint so
4207 that you can @dfn{enable} it again later.
4209 You disable and enable breakpoints, watchpoints, and catchpoints with
4210 the @code{enable} and @code{disable} commands, optionally specifying
4211 one or more breakpoint numbers as arguments. Use @code{info break} to
4212 print a list of all breakpoints, watchpoints, and catchpoints if you
4213 do not know which numbers to use.
4215 Disabling and enabling a breakpoint that has multiple locations
4216 affects all of its locations.
4218 A breakpoint, watchpoint, or catchpoint can have any of four different
4219 states of enablement:
4223 Enabled. The breakpoint stops your program. A breakpoint set
4224 with the @code{break} command starts out in this state.
4226 Disabled. The breakpoint has no effect on your program.
4228 Enabled once. The breakpoint stops your program, but then becomes
4231 Enabled for deletion. The breakpoint stops your program, but
4232 immediately after it does so it is deleted permanently. A breakpoint
4233 set with the @code{tbreak} command starts out in this state.
4236 You can use the following commands to enable or disable breakpoints,
4237 watchpoints, and catchpoints:
4241 @kindex dis @r{(@code{disable})}
4242 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4243 Disable the specified breakpoints---or all breakpoints, if none are
4244 listed. A disabled breakpoint has no effect but is not forgotten. All
4245 options such as ignore-counts, conditions and commands are remembered in
4246 case the breakpoint is enabled again later. You may abbreviate
4247 @code{disable} as @code{dis}.
4250 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4251 Enable the specified breakpoints (or all defined breakpoints). They
4252 become effective once again in stopping your program.
4254 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4255 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4256 of these breakpoints immediately after stopping your program.
4258 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4259 Enable the specified breakpoints to work once, then die. @value{GDBN}
4260 deletes any of these breakpoints as soon as your program stops there.
4261 Breakpoints set by the @code{tbreak} command start out in this state.
4264 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4265 @c confusing: tbreak is also initially enabled.
4266 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4267 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4268 subsequently, they become disabled or enabled only when you use one of
4269 the commands above. (The command @code{until} can set and delete a
4270 breakpoint of its own, but it does not change the state of your other
4271 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4275 @subsection Break Conditions
4276 @cindex conditional breakpoints
4277 @cindex breakpoint conditions
4279 @c FIXME what is scope of break condition expr? Context where wanted?
4280 @c in particular for a watchpoint?
4281 The simplest sort of breakpoint breaks every time your program reaches a
4282 specified place. You can also specify a @dfn{condition} for a
4283 breakpoint. A condition is just a Boolean expression in your
4284 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4285 a condition evaluates the expression each time your program reaches it,
4286 and your program stops only if the condition is @emph{true}.
4288 This is the converse of using assertions for program validation; in that
4289 situation, you want to stop when the assertion is violated---that is,
4290 when the condition is false. In C, if you want to test an assertion expressed
4291 by the condition @var{assert}, you should set the condition
4292 @samp{! @var{assert}} on the appropriate breakpoint.
4294 Conditions are also accepted for watchpoints; you may not need them,
4295 since a watchpoint is inspecting the value of an expression anyhow---but
4296 it might be simpler, say, to just set a watchpoint on a variable name,
4297 and specify a condition that tests whether the new value is an interesting
4300 Break conditions can have side effects, and may even call functions in
4301 your program. This can be useful, for example, to activate functions
4302 that log program progress, or to use your own print functions to
4303 format special data structures. The effects are completely predictable
4304 unless there is another enabled breakpoint at the same address. (In
4305 that case, @value{GDBN} might see the other breakpoint first and stop your
4306 program without checking the condition of this one.) Note that
4307 breakpoint commands are usually more convenient and flexible than break
4309 purpose of performing side effects when a breakpoint is reached
4310 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4312 Break conditions can be specified when a breakpoint is set, by using
4313 @samp{if} in the arguments to the @code{break} command. @xref{Set
4314 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4315 with the @code{condition} command.
4317 You can also use the @code{if} keyword with the @code{watch} command.
4318 The @code{catch} command does not recognize the @code{if} keyword;
4319 @code{condition} is the only way to impose a further condition on a
4324 @item condition @var{bnum} @var{expression}
4325 Specify @var{expression} as the break condition for breakpoint,
4326 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4327 breakpoint @var{bnum} stops your program only if the value of
4328 @var{expression} is true (nonzero, in C). When you use
4329 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4330 syntactic correctness, and to determine whether symbols in it have
4331 referents in the context of your breakpoint. If @var{expression} uses
4332 symbols not referenced in the context of the breakpoint, @value{GDBN}
4333 prints an error message:
4336 No symbol "foo" in current context.
4341 not actually evaluate @var{expression} at the time the @code{condition}
4342 command (or a command that sets a breakpoint with a condition, like
4343 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4345 @item condition @var{bnum}
4346 Remove the condition from breakpoint number @var{bnum}. It becomes
4347 an ordinary unconditional breakpoint.
4350 @cindex ignore count (of breakpoint)
4351 A special case of a breakpoint condition is to stop only when the
4352 breakpoint has been reached a certain number of times. This is so
4353 useful that there is a special way to do it, using the @dfn{ignore
4354 count} of the breakpoint. Every breakpoint has an ignore count, which
4355 is an integer. Most of the time, the ignore count is zero, and
4356 therefore has no effect. But if your program reaches a breakpoint whose
4357 ignore count is positive, then instead of stopping, it just decrements
4358 the ignore count by one and continues. As a result, if the ignore count
4359 value is @var{n}, the breakpoint does not stop the next @var{n} times
4360 your program reaches it.
4364 @item ignore @var{bnum} @var{count}
4365 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4366 The next @var{count} times the breakpoint is reached, your program's
4367 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4370 To make the breakpoint stop the next time it is reached, specify
4373 When you use @code{continue} to resume execution of your program from a
4374 breakpoint, you can specify an ignore count directly as an argument to
4375 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4376 Stepping,,Continuing and Stepping}.
4378 If a breakpoint has a positive ignore count and a condition, the
4379 condition is not checked. Once the ignore count reaches zero,
4380 @value{GDBN} resumes checking the condition.
4382 You could achieve the effect of the ignore count with a condition such
4383 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4384 is decremented each time. @xref{Convenience Vars, ,Convenience
4388 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4391 @node Break Commands
4392 @subsection Breakpoint Command Lists
4394 @cindex breakpoint commands
4395 You can give any breakpoint (or watchpoint or catchpoint) a series of
4396 commands to execute when your program stops due to that breakpoint. For
4397 example, you might want to print the values of certain expressions, or
4398 enable other breakpoints.
4402 @kindex end@r{ (breakpoint commands)}
4403 @item commands @r{[}@var{range}@dots{}@r{]}
4404 @itemx @dots{} @var{command-list} @dots{}
4406 Specify a list of commands for the given breakpoints. The commands
4407 themselves appear on the following lines. Type a line containing just
4408 @code{end} to terminate the commands.
4410 To remove all commands from a breakpoint, type @code{commands} and
4411 follow it immediately with @code{end}; that is, give no commands.
4413 With no argument, @code{commands} refers to the last breakpoint,
4414 watchpoint, or catchpoint set (not to the breakpoint most recently
4415 encountered). If the most recent breakpoints were set with a single
4416 command, then the @code{commands} will apply to all the breakpoints
4417 set by that command. This applies to breakpoints set by
4418 @code{rbreak}, and also applies when a single @code{break} command
4419 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4423 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4424 disabled within a @var{command-list}.
4426 You can use breakpoint commands to start your program up again. Simply
4427 use the @code{continue} command, or @code{step}, or any other command
4428 that resumes execution.
4430 Any other commands in the command list, after a command that resumes
4431 execution, are ignored. This is because any time you resume execution
4432 (even with a simple @code{next} or @code{step}), you may encounter
4433 another breakpoint---which could have its own command list, leading to
4434 ambiguities about which list to execute.
4437 If the first command you specify in a command list is @code{silent}, the
4438 usual message about stopping at a breakpoint is not printed. This may
4439 be desirable for breakpoints that are to print a specific message and
4440 then continue. If none of the remaining commands print anything, you
4441 see no sign that the breakpoint was reached. @code{silent} is
4442 meaningful only at the beginning of a breakpoint command list.
4444 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4445 print precisely controlled output, and are often useful in silent
4446 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4448 For example, here is how you could use breakpoint commands to print the
4449 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4455 printf "x is %d\n",x
4460 One application for breakpoint commands is to compensate for one bug so
4461 you can test for another. Put a breakpoint just after the erroneous line
4462 of code, give it a condition to detect the case in which something
4463 erroneous has been done, and give it commands to assign correct values
4464 to any variables that need them. End with the @code{continue} command
4465 so that your program does not stop, and start with the @code{silent}
4466 command so that no output is produced. Here is an example:
4477 @node Save Breakpoints
4478 @subsection How to save breakpoints to a file
4480 To save breakpoint definitions to a file use the @w{@code{save
4481 breakpoints}} command.
4484 @kindex save breakpoints
4485 @cindex save breakpoints to a file for future sessions
4486 @item save breakpoints [@var{filename}]
4487 This command saves all current breakpoint definitions together with
4488 their commands and ignore counts, into a file @file{@var{filename}}
4489 suitable for use in a later debugging session. This includes all
4490 types of breakpoints (breakpoints, watchpoints, catchpoints,
4491 tracepoints). To read the saved breakpoint definitions, use the
4492 @code{source} command (@pxref{Command Files}). Note that watchpoints
4493 with expressions involving local variables may fail to be recreated
4494 because it may not be possible to access the context where the
4495 watchpoint is valid anymore. Because the saved breakpoint definitions
4496 are simply a sequence of @value{GDBN} commands that recreate the
4497 breakpoints, you can edit the file in your favorite editing program,
4498 and remove the breakpoint definitions you're not interested in, or
4499 that can no longer be recreated.
4502 @c @ifclear BARETARGET
4503 @node Error in Breakpoints
4504 @subsection ``Cannot insert breakpoints''
4506 If you request too many active hardware-assisted breakpoints and
4507 watchpoints, you will see this error message:
4509 @c FIXME: the precise wording of this message may change; the relevant
4510 @c source change is not committed yet (Sep 3, 1999).
4512 Stopped; cannot insert breakpoints.
4513 You may have requested too many hardware breakpoints and watchpoints.
4517 This message is printed when you attempt to resume the program, since
4518 only then @value{GDBN} knows exactly how many hardware breakpoints and
4519 watchpoints it needs to insert.
4521 When this message is printed, you need to disable or remove some of the
4522 hardware-assisted breakpoints and watchpoints, and then continue.
4524 @node Breakpoint-related Warnings
4525 @subsection ``Breakpoint address adjusted...''
4526 @cindex breakpoint address adjusted
4528 Some processor architectures place constraints on the addresses at
4529 which breakpoints may be placed. For architectures thus constrained,
4530 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4531 with the constraints dictated by the architecture.
4533 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4534 a VLIW architecture in which a number of RISC-like instructions may be
4535 bundled together for parallel execution. The FR-V architecture
4536 constrains the location of a breakpoint instruction within such a
4537 bundle to the instruction with the lowest address. @value{GDBN}
4538 honors this constraint by adjusting a breakpoint's address to the
4539 first in the bundle.
4541 It is not uncommon for optimized code to have bundles which contain
4542 instructions from different source statements, thus it may happen that
4543 a breakpoint's address will be adjusted from one source statement to
4544 another. Since this adjustment may significantly alter @value{GDBN}'s
4545 breakpoint related behavior from what the user expects, a warning is
4546 printed when the breakpoint is first set and also when the breakpoint
4549 A warning like the one below is printed when setting a breakpoint
4550 that's been subject to address adjustment:
4553 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4556 Such warnings are printed both for user settable and @value{GDBN}'s
4557 internal breakpoints. If you see one of these warnings, you should
4558 verify that a breakpoint set at the adjusted address will have the
4559 desired affect. If not, the breakpoint in question may be removed and
4560 other breakpoints may be set which will have the desired behavior.
4561 E.g., it may be sufficient to place the breakpoint at a later
4562 instruction. A conditional breakpoint may also be useful in some
4563 cases to prevent the breakpoint from triggering too often.
4565 @value{GDBN} will also issue a warning when stopping at one of these
4566 adjusted breakpoints:
4569 warning: Breakpoint 1 address previously adjusted from 0x00010414
4573 When this warning is encountered, it may be too late to take remedial
4574 action except in cases where the breakpoint is hit earlier or more
4575 frequently than expected.
4577 @node Continuing and Stepping
4578 @section Continuing and Stepping
4582 @cindex resuming execution
4583 @dfn{Continuing} means resuming program execution until your program
4584 completes normally. In contrast, @dfn{stepping} means executing just
4585 one more ``step'' of your program, where ``step'' may mean either one
4586 line of source code, or one machine instruction (depending on what
4587 particular command you use). Either when continuing or when stepping,
4588 your program may stop even sooner, due to a breakpoint or a signal. (If
4589 it stops due to a signal, you may want to use @code{handle}, or use
4590 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4594 @kindex c @r{(@code{continue})}
4595 @kindex fg @r{(resume foreground execution)}
4596 @item continue @r{[}@var{ignore-count}@r{]}
4597 @itemx c @r{[}@var{ignore-count}@r{]}
4598 @itemx fg @r{[}@var{ignore-count}@r{]}
4599 Resume program execution, at the address where your program last stopped;
4600 any breakpoints set at that address are bypassed. The optional argument
4601 @var{ignore-count} allows you to specify a further number of times to
4602 ignore a breakpoint at this location; its effect is like that of
4603 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4605 The argument @var{ignore-count} is meaningful only when your program
4606 stopped due to a breakpoint. At other times, the argument to
4607 @code{continue} is ignored.
4609 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4610 debugged program is deemed to be the foreground program) are provided
4611 purely for convenience, and have exactly the same behavior as
4615 To resume execution at a different place, you can use @code{return}
4616 (@pxref{Returning, ,Returning from a Function}) to go back to the
4617 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4618 Different Address}) to go to an arbitrary location in your program.
4620 A typical technique for using stepping is to set a breakpoint
4621 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4622 beginning of the function or the section of your program where a problem
4623 is believed to lie, run your program until it stops at that breakpoint,
4624 and then step through the suspect area, examining the variables that are
4625 interesting, until you see the problem happen.
4629 @kindex s @r{(@code{step})}
4631 Continue running your program until control reaches a different source
4632 line, then stop it and return control to @value{GDBN}. This command is
4633 abbreviated @code{s}.
4636 @c "without debugging information" is imprecise; actually "without line
4637 @c numbers in the debugging information". (gcc -g1 has debugging info but
4638 @c not line numbers). But it seems complex to try to make that
4639 @c distinction here.
4640 @emph{Warning:} If you use the @code{step} command while control is
4641 within a function that was compiled without debugging information,
4642 execution proceeds until control reaches a function that does have
4643 debugging information. Likewise, it will not step into a function which
4644 is compiled without debugging information. To step through functions
4645 without debugging information, use the @code{stepi} command, described
4649 The @code{step} command only stops at the first instruction of a source
4650 line. This prevents the multiple stops that could otherwise occur in
4651 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4652 to stop if a function that has debugging information is called within
4653 the line. In other words, @code{step} @emph{steps inside} any functions
4654 called within the line.
4656 Also, the @code{step} command only enters a function if there is line
4657 number information for the function. Otherwise it acts like the
4658 @code{next} command. This avoids problems when using @code{cc -gl}
4659 on MIPS machines. Previously, @code{step} entered subroutines if there
4660 was any debugging information about the routine.
4662 @item step @var{count}
4663 Continue running as in @code{step}, but do so @var{count} times. If a
4664 breakpoint is reached, or a signal not related to stepping occurs before
4665 @var{count} steps, stepping stops right away.
4668 @kindex n @r{(@code{next})}
4669 @item next @r{[}@var{count}@r{]}
4670 Continue to the next source line in the current (innermost) stack frame.
4671 This is similar to @code{step}, but function calls that appear within
4672 the line of code are executed without stopping. Execution stops when
4673 control reaches a different line of code at the original stack level
4674 that was executing when you gave the @code{next} command. This command
4675 is abbreviated @code{n}.
4677 An argument @var{count} is a repeat count, as for @code{step}.
4680 @c FIX ME!! Do we delete this, or is there a way it fits in with
4681 @c the following paragraph? --- Vctoria
4683 @c @code{next} within a function that lacks debugging information acts like
4684 @c @code{step}, but any function calls appearing within the code of the
4685 @c function are executed without stopping.
4687 The @code{next} command only stops at the first instruction of a
4688 source line. This prevents multiple stops that could otherwise occur in
4689 @code{switch} statements, @code{for} loops, etc.
4691 @kindex set step-mode
4693 @cindex functions without line info, and stepping
4694 @cindex stepping into functions with no line info
4695 @itemx set step-mode on
4696 The @code{set step-mode on} command causes the @code{step} command to
4697 stop at the first instruction of a function which contains no debug line
4698 information rather than stepping over it.
4700 This is useful in cases where you may be interested in inspecting the
4701 machine instructions of a function which has no symbolic info and do not
4702 want @value{GDBN} to automatically skip over this function.
4704 @item set step-mode off
4705 Causes the @code{step} command to step over any functions which contains no
4706 debug information. This is the default.
4708 @item show step-mode
4709 Show whether @value{GDBN} will stop in or step over functions without
4710 source line debug information.
4713 @kindex fin @r{(@code{finish})}
4715 Continue running until just after function in the selected stack frame
4716 returns. Print the returned value (if any). This command can be
4717 abbreviated as @code{fin}.
4719 Contrast this with the @code{return} command (@pxref{Returning,
4720 ,Returning from a Function}).
4723 @kindex u @r{(@code{until})}
4724 @cindex run until specified location
4727 Continue running until a source line past the current line, in the
4728 current stack frame, is reached. This command is used to avoid single
4729 stepping through a loop more than once. It is like the @code{next}
4730 command, except that when @code{until} encounters a jump, it
4731 automatically continues execution until the program counter is greater
4732 than the address of the jump.
4734 This means that when you reach the end of a loop after single stepping
4735 though it, @code{until} makes your program continue execution until it
4736 exits the loop. In contrast, a @code{next} command at the end of a loop
4737 simply steps back to the beginning of the loop, which forces you to step
4738 through the next iteration.
4740 @code{until} always stops your program if it attempts to exit the current
4743 @code{until} may produce somewhat counterintuitive results if the order
4744 of machine code does not match the order of the source lines. For
4745 example, in the following excerpt from a debugging session, the @code{f}
4746 (@code{frame}) command shows that execution is stopped at line
4747 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4751 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4753 (@value{GDBP}) until
4754 195 for ( ; argc > 0; NEXTARG) @{
4757 This happened because, for execution efficiency, the compiler had
4758 generated code for the loop closure test at the end, rather than the
4759 start, of the loop---even though the test in a C @code{for}-loop is
4760 written before the body of the loop. The @code{until} command appeared
4761 to step back to the beginning of the loop when it advanced to this
4762 expression; however, it has not really gone to an earlier
4763 statement---not in terms of the actual machine code.
4765 @code{until} with no argument works by means of single
4766 instruction stepping, and hence is slower than @code{until} with an
4769 @item until @var{location}
4770 @itemx u @var{location}
4771 Continue running your program until either the specified location is
4772 reached, or the current stack frame returns. @var{location} is any of
4773 the forms described in @ref{Specify Location}.
4774 This form of the command uses temporary breakpoints, and
4775 hence is quicker than @code{until} without an argument. The specified
4776 location is actually reached only if it is in the current frame. This
4777 implies that @code{until} can be used to skip over recursive function
4778 invocations. For instance in the code below, if the current location is
4779 line @code{96}, issuing @code{until 99} will execute the program up to
4780 line @code{99} in the same invocation of factorial, i.e., after the inner
4781 invocations have returned.
4784 94 int factorial (int value)
4786 96 if (value > 1) @{
4787 97 value *= factorial (value - 1);
4794 @kindex advance @var{location}
4795 @itemx advance @var{location}
4796 Continue running the program up to the given @var{location}. An argument is
4797 required, which should be of one of the forms described in
4798 @ref{Specify Location}.
4799 Execution will also stop upon exit from the current stack
4800 frame. This command is similar to @code{until}, but @code{advance} will
4801 not skip over recursive function calls, and the target location doesn't
4802 have to be in the same frame as the current one.
4806 @kindex si @r{(@code{stepi})}
4808 @itemx stepi @var{arg}
4810 Execute one machine instruction, then stop and return to the debugger.
4812 It is often useful to do @samp{display/i $pc} when stepping by machine
4813 instructions. This makes @value{GDBN} automatically display the next
4814 instruction to be executed, each time your program stops. @xref{Auto
4815 Display,, Automatic Display}.
4817 An argument is a repeat count, as in @code{step}.
4821 @kindex ni @r{(@code{nexti})}
4823 @itemx nexti @var{arg}
4825 Execute one machine instruction, but if it is a function call,
4826 proceed until the function returns.
4828 An argument is a repeat count, as in @code{next}.
4835 A signal is an asynchronous event that can happen in a program. The
4836 operating system defines the possible kinds of signals, and gives each
4837 kind a name and a number. For example, in Unix @code{SIGINT} is the
4838 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4839 @code{SIGSEGV} is the signal a program gets from referencing a place in
4840 memory far away from all the areas in use; @code{SIGALRM} occurs when
4841 the alarm clock timer goes off (which happens only if your program has
4842 requested an alarm).
4844 @cindex fatal signals
4845 Some signals, including @code{SIGALRM}, are a normal part of the
4846 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4847 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4848 program has not specified in advance some other way to handle the signal.
4849 @code{SIGINT} does not indicate an error in your program, but it is normally
4850 fatal so it can carry out the purpose of the interrupt: to kill the program.
4852 @value{GDBN} has the ability to detect any occurrence of a signal in your
4853 program. You can tell @value{GDBN} in advance what to do for each kind of
4856 @cindex handling signals
4857 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4858 @code{SIGALRM} be silently passed to your program
4859 (so as not to interfere with their role in the program's functioning)
4860 but to stop your program immediately whenever an error signal happens.
4861 You can change these settings with the @code{handle} command.
4864 @kindex info signals
4868 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4869 handle each one. You can use this to see the signal numbers of all
4870 the defined types of signals.
4872 @item info signals @var{sig}
4873 Similar, but print information only about the specified signal number.
4875 @code{info handle} is an alias for @code{info signals}.
4878 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4879 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4880 can be the number of a signal or its name (with or without the
4881 @samp{SIG} at the beginning); a list of signal numbers of the form
4882 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4883 known signals. Optional arguments @var{keywords}, described below,
4884 say what change to make.
4888 The keywords allowed by the @code{handle} command can be abbreviated.
4889 Their full names are:
4893 @value{GDBN} should not stop your program when this signal happens. It may
4894 still print a message telling you that the signal has come in.
4897 @value{GDBN} should stop your program when this signal happens. This implies
4898 the @code{print} keyword as well.
4901 @value{GDBN} should print a message when this signal happens.
4904 @value{GDBN} should not mention the occurrence of the signal at all. This
4905 implies the @code{nostop} keyword as well.
4909 @value{GDBN} should allow your program to see this signal; your program
4910 can handle the signal, or else it may terminate if the signal is fatal
4911 and not handled. @code{pass} and @code{noignore} are synonyms.
4915 @value{GDBN} should not allow your program to see this signal.
4916 @code{nopass} and @code{ignore} are synonyms.
4920 When a signal stops your program, the signal is not visible to the
4922 continue. Your program sees the signal then, if @code{pass} is in
4923 effect for the signal in question @emph{at that time}. In other words,
4924 after @value{GDBN} reports a signal, you can use the @code{handle}
4925 command with @code{pass} or @code{nopass} to control whether your
4926 program sees that signal when you continue.
4928 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4929 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4930 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4933 You can also use the @code{signal} command to prevent your program from
4934 seeing a signal, or cause it to see a signal it normally would not see,
4935 or to give it any signal at any time. For example, if your program stopped
4936 due to some sort of memory reference error, you might store correct
4937 values into the erroneous variables and continue, hoping to see more
4938 execution; but your program would probably terminate immediately as
4939 a result of the fatal signal once it saw the signal. To prevent this,
4940 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4943 @cindex extra signal information
4944 @anchor{extra signal information}
4946 On some targets, @value{GDBN} can inspect extra signal information
4947 associated with the intercepted signal, before it is actually
4948 delivered to the program being debugged. This information is exported
4949 by the convenience variable @code{$_siginfo}, and consists of data
4950 that is passed by the kernel to the signal handler at the time of the
4951 receipt of a signal. The data type of the information itself is
4952 target dependent. You can see the data type using the @code{ptype
4953 $_siginfo} command. On Unix systems, it typically corresponds to the
4954 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4957 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4958 referenced address that raised a segmentation fault.
4962 (@value{GDBP}) continue
4963 Program received signal SIGSEGV, Segmentation fault.
4964 0x0000000000400766 in main ()
4966 (@value{GDBP}) ptype $_siginfo
4973 struct @{...@} _kill;
4974 struct @{...@} _timer;
4976 struct @{...@} _sigchld;
4977 struct @{...@} _sigfault;
4978 struct @{...@} _sigpoll;
4981 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4985 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4986 $1 = (void *) 0x7ffff7ff7000
4990 Depending on target support, @code{$_siginfo} may also be writable.
4993 @section Stopping and Starting Multi-thread Programs
4995 @cindex stopped threads
4996 @cindex threads, stopped
4998 @cindex continuing threads
4999 @cindex threads, continuing
5001 @value{GDBN} supports debugging programs with multiple threads
5002 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5003 are two modes of controlling execution of your program within the
5004 debugger. In the default mode, referred to as @dfn{all-stop mode},
5005 when any thread in your program stops (for example, at a breakpoint
5006 or while being stepped), all other threads in the program are also stopped by
5007 @value{GDBN}. On some targets, @value{GDBN} also supports
5008 @dfn{non-stop mode}, in which other threads can continue to run freely while
5009 you examine the stopped thread in the debugger.
5012 * All-Stop Mode:: All threads stop when GDB takes control
5013 * Non-Stop Mode:: Other threads continue to execute
5014 * Background Execution:: Running your program asynchronously
5015 * Thread-Specific Breakpoints:: Controlling breakpoints
5016 * Interrupted System Calls:: GDB may interfere with system calls
5017 * Observer Mode:: GDB does not alter program behavior
5021 @subsection All-Stop Mode
5023 @cindex all-stop mode
5025 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5026 @emph{all} threads of execution stop, not just the current thread. This
5027 allows you to examine the overall state of the program, including
5028 switching between threads, without worrying that things may change
5031 Conversely, whenever you restart the program, @emph{all} threads start
5032 executing. @emph{This is true even when single-stepping} with commands
5033 like @code{step} or @code{next}.
5035 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5036 Since thread scheduling is up to your debugging target's operating
5037 system (not controlled by @value{GDBN}), other threads may
5038 execute more than one statement while the current thread completes a
5039 single step. Moreover, in general other threads stop in the middle of a
5040 statement, rather than at a clean statement boundary, when the program
5043 You might even find your program stopped in another thread after
5044 continuing or even single-stepping. This happens whenever some other
5045 thread runs into a breakpoint, a signal, or an exception before the
5046 first thread completes whatever you requested.
5048 @cindex automatic thread selection
5049 @cindex switching threads automatically
5050 @cindex threads, automatic switching
5051 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5052 signal, it automatically selects the thread where that breakpoint or
5053 signal happened. @value{GDBN} alerts you to the context switch with a
5054 message such as @samp{[Switching to Thread @var{n}]} to identify the
5057 On some OSes, you can modify @value{GDBN}'s default behavior by
5058 locking the OS scheduler to allow only a single thread to run.
5061 @item set scheduler-locking @var{mode}
5062 @cindex scheduler locking mode
5063 @cindex lock scheduler
5064 Set the scheduler locking mode. If it is @code{off}, then there is no
5065 locking and any thread may run at any time. If @code{on}, then only the
5066 current thread may run when the inferior is resumed. The @code{step}
5067 mode optimizes for single-stepping; it prevents other threads
5068 from preempting the current thread while you are stepping, so that
5069 the focus of debugging does not change unexpectedly.
5070 Other threads only rarely (or never) get a chance to run
5071 when you step. They are more likely to run when you @samp{next} over a
5072 function call, and they are completely free to run when you use commands
5073 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5074 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5075 the current thread away from the thread that you are debugging.
5077 @item show scheduler-locking
5078 Display the current scheduler locking mode.
5081 @cindex resume threads of multiple processes simultaneously
5082 By default, when you issue one of the execution commands such as
5083 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5084 threads of the current inferior to run. For example, if @value{GDBN}
5085 is attached to two inferiors, each with two threads, the
5086 @code{continue} command resumes only the two threads of the current
5087 inferior. This is useful, for example, when you debug a program that
5088 forks and you want to hold the parent stopped (so that, for instance,
5089 it doesn't run to exit), while you debug the child. In other
5090 situations, you may not be interested in inspecting the current state
5091 of any of the processes @value{GDBN} is attached to, and you may want
5092 to resume them all until some breakpoint is hit. In the latter case,
5093 you can instruct @value{GDBN} to allow all threads of all the
5094 inferiors to run with the @w{@code{set schedule-multiple}} command.
5097 @kindex set schedule-multiple
5098 @item set schedule-multiple
5099 Set the mode for allowing threads of multiple processes to be resumed
5100 when an execution command is issued. When @code{on}, all threads of
5101 all processes are allowed to run. When @code{off}, only the threads
5102 of the current process are resumed. The default is @code{off}. The
5103 @code{scheduler-locking} mode takes precedence when set to @code{on},
5104 or while you are stepping and set to @code{step}.
5106 @item show schedule-multiple
5107 Display the current mode for resuming the execution of threads of
5112 @subsection Non-Stop Mode
5114 @cindex non-stop mode
5116 @c This section is really only a place-holder, and needs to be expanded
5117 @c with more details.
5119 For some multi-threaded targets, @value{GDBN} supports an optional
5120 mode of operation in which you can examine stopped program threads in
5121 the debugger while other threads continue to execute freely. This
5122 minimizes intrusion when debugging live systems, such as programs
5123 where some threads have real-time constraints or must continue to
5124 respond to external events. This is referred to as @dfn{non-stop} mode.
5126 In non-stop mode, when a thread stops to report a debugging event,
5127 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5128 threads as well, in contrast to the all-stop mode behavior. Additionally,
5129 execution commands such as @code{continue} and @code{step} apply by default
5130 only to the current thread in non-stop mode, rather than all threads as
5131 in all-stop mode. This allows you to control threads explicitly in
5132 ways that are not possible in all-stop mode --- for example, stepping
5133 one thread while allowing others to run freely, stepping
5134 one thread while holding all others stopped, or stepping several threads
5135 independently and simultaneously.
5137 To enter non-stop mode, use this sequence of commands before you run
5138 or attach to your program:
5141 # Enable the async interface.
5144 # If using the CLI, pagination breaks non-stop.
5147 # Finally, turn it on!
5151 You can use these commands to manipulate the non-stop mode setting:
5154 @kindex set non-stop
5155 @item set non-stop on
5156 Enable selection of non-stop mode.
5157 @item set non-stop off
5158 Disable selection of non-stop mode.
5159 @kindex show non-stop
5161 Show the current non-stop enablement setting.
5164 Note these commands only reflect whether non-stop mode is enabled,
5165 not whether the currently-executing program is being run in non-stop mode.
5166 In particular, the @code{set non-stop} preference is only consulted when
5167 @value{GDBN} starts or connects to the target program, and it is generally
5168 not possible to switch modes once debugging has started. Furthermore,
5169 since not all targets support non-stop mode, even when you have enabled
5170 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5173 In non-stop mode, all execution commands apply only to the current thread
5174 by default. That is, @code{continue} only continues one thread.
5175 To continue all threads, issue @code{continue -a} or @code{c -a}.
5177 You can use @value{GDBN}'s background execution commands
5178 (@pxref{Background Execution}) to run some threads in the background
5179 while you continue to examine or step others from @value{GDBN}.
5180 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5181 always executed asynchronously in non-stop mode.
5183 Suspending execution is done with the @code{interrupt} command when
5184 running in the background, or @kbd{Ctrl-c} during foreground execution.
5185 In all-stop mode, this stops the whole process;
5186 but in non-stop mode the interrupt applies only to the current thread.
5187 To stop the whole program, use @code{interrupt -a}.
5189 Other execution commands do not currently support the @code{-a} option.
5191 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5192 that thread current, as it does in all-stop mode. This is because the
5193 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5194 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5195 changed to a different thread just as you entered a command to operate on the
5196 previously current thread.
5198 @node Background Execution
5199 @subsection Background Execution
5201 @cindex foreground execution
5202 @cindex background execution
5203 @cindex asynchronous execution
5204 @cindex execution, foreground, background and asynchronous
5206 @value{GDBN}'s execution commands have two variants: the normal
5207 foreground (synchronous) behavior, and a background
5208 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5209 the program to report that some thread has stopped before prompting for
5210 another command. In background execution, @value{GDBN} immediately gives
5211 a command prompt so that you can issue other commands while your program runs.
5213 You need to explicitly enable asynchronous mode before you can use
5214 background execution commands. You can use these commands to
5215 manipulate the asynchronous mode setting:
5218 @kindex set target-async
5219 @item set target-async on
5220 Enable asynchronous mode.
5221 @item set target-async off
5222 Disable asynchronous mode.
5223 @kindex show target-async
5224 @item show target-async
5225 Show the current target-async setting.
5228 If the target doesn't support async mode, @value{GDBN} issues an error
5229 message if you attempt to use the background execution commands.
5231 To specify background execution, add a @code{&} to the command. For example,
5232 the background form of the @code{continue} command is @code{continue&}, or
5233 just @code{c&}. The execution commands that accept background execution
5239 @xref{Starting, , Starting your Program}.
5243 @xref{Attach, , Debugging an Already-running Process}.
5247 @xref{Continuing and Stepping, step}.
5251 @xref{Continuing and Stepping, stepi}.
5255 @xref{Continuing and Stepping, next}.
5259 @xref{Continuing and Stepping, nexti}.
5263 @xref{Continuing and Stepping, continue}.
5267 @xref{Continuing and Stepping, finish}.
5271 @xref{Continuing and Stepping, until}.
5275 Background execution is especially useful in conjunction with non-stop
5276 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5277 However, you can also use these commands in the normal all-stop mode with
5278 the restriction that you cannot issue another execution command until the
5279 previous one finishes. Examples of commands that are valid in all-stop
5280 mode while the program is running include @code{help} and @code{info break}.
5282 You can interrupt your program while it is running in the background by
5283 using the @code{interrupt} command.
5290 Suspend execution of the running program. In all-stop mode,
5291 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5292 only the current thread. To stop the whole program in non-stop mode,
5293 use @code{interrupt -a}.
5296 @node Thread-Specific Breakpoints
5297 @subsection Thread-Specific Breakpoints
5299 When your program has multiple threads (@pxref{Threads,, Debugging
5300 Programs with Multiple Threads}), you can choose whether to set
5301 breakpoints on all threads, or on a particular thread.
5304 @cindex breakpoints and threads
5305 @cindex thread breakpoints
5306 @kindex break @dots{} thread @var{threadno}
5307 @item break @var{linespec} thread @var{threadno}
5308 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5309 @var{linespec} specifies source lines; there are several ways of
5310 writing them (@pxref{Specify Location}), but the effect is always to
5311 specify some source line.
5313 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5314 to specify that you only want @value{GDBN} to stop the program when a
5315 particular thread reaches this breakpoint. @var{threadno} is one of the
5316 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5317 column of the @samp{info threads} display.
5319 If you do not specify @samp{thread @var{threadno}} when you set a
5320 breakpoint, the breakpoint applies to @emph{all} threads of your
5323 You can use the @code{thread} qualifier on conditional breakpoints as
5324 well; in this case, place @samp{thread @var{threadno}} before or
5325 after the breakpoint condition, like this:
5328 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5333 @node Interrupted System Calls
5334 @subsection Interrupted System Calls
5336 @cindex thread breakpoints and system calls
5337 @cindex system calls and thread breakpoints
5338 @cindex premature return from system calls
5339 There is an unfortunate side effect when using @value{GDBN} to debug
5340 multi-threaded programs. If one thread stops for a
5341 breakpoint, or for some other reason, and another thread is blocked in a
5342 system call, then the system call may return prematurely. This is a
5343 consequence of the interaction between multiple threads and the signals
5344 that @value{GDBN} uses to implement breakpoints and other events that
5347 To handle this problem, your program should check the return value of
5348 each system call and react appropriately. This is good programming
5351 For example, do not write code like this:
5357 The call to @code{sleep} will return early if a different thread stops
5358 at a breakpoint or for some other reason.
5360 Instead, write this:
5365 unslept = sleep (unslept);
5368 A system call is allowed to return early, so the system is still
5369 conforming to its specification. But @value{GDBN} does cause your
5370 multi-threaded program to behave differently than it would without
5373 Also, @value{GDBN} uses internal breakpoints in the thread library to
5374 monitor certain events such as thread creation and thread destruction.
5375 When such an event happens, a system call in another thread may return
5376 prematurely, even though your program does not appear to stop.
5379 @subsection Observer Mode
5381 If you want to build on non-stop mode and observe program behavior
5382 without any chance of disruption by @value{GDBN}, you can set
5383 variables to disable all of the debugger's attempts to modify state,
5384 whether by writing memory, inserting breakpoints, etc. These operate
5385 at a low level, intercepting operations from all commands.
5387 When all of these are set to @code{off}, then @value{GDBN} is said to
5388 be @dfn{observer mode}. As a convenience, the variable
5389 @code{observer} can be set to disable these, plus enable non-stop
5392 Note that @value{GDBN} will not prevent you from making nonsensical
5393 combinations of these settings. For instance, if you have enabled
5394 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5395 then breakpoints that work by writing trap instructions into the code
5396 stream will still not be able to be placed.
5401 @item set observer on
5402 @itemx set observer off
5403 When set to @code{on}, this disables all the permission variables
5404 below (except for @code{insert-fast-tracepoints}), plus enables
5405 non-stop debugging. Setting this to @code{off} switches back to
5406 normal debugging, though remaining in non-stop mode.
5409 Show whether observer mode is on or off.
5411 @kindex may-write-registers
5412 @item set may-write-registers on
5413 @itemx set may-write-registers off
5414 This controls whether @value{GDBN} will attempt to alter the values of
5415 registers, such as with assignment expressions in @code{print}, or the
5416 @code{jump} command. It defaults to @code{on}.
5418 @item show may-write-registers
5419 Show the current permission to write registers.
5421 @kindex may-write-memory
5422 @item set may-write-memory on
5423 @itemx set may-write-memory off
5424 This controls whether @value{GDBN} will attempt to alter the contents
5425 of memory, such as with assignment expressions in @code{print}. It
5426 defaults to @code{on}.
5428 @item show may-write-memory
5429 Show the current permission to write memory.
5431 @kindex may-insert-breakpoints
5432 @item set may-insert-breakpoints on
5433 @itemx set may-insert-breakpoints off
5434 This controls whether @value{GDBN} will attempt to insert breakpoints.
5435 This affects all breakpoints, including internal breakpoints defined
5436 by @value{GDBN}. It defaults to @code{on}.
5438 @item show may-insert-breakpoints
5439 Show the current permission to insert breakpoints.
5441 @kindex may-insert-tracepoints
5442 @item set may-insert-tracepoints on
5443 @itemx set may-insert-tracepoints off
5444 This controls whether @value{GDBN} will attempt to insert (regular)
5445 tracepoints at the beginning of a tracing experiment. It affects only
5446 non-fast tracepoints, fast tracepoints being under the control of
5447 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5449 @item show may-insert-tracepoints
5450 Show the current permission to insert tracepoints.
5452 @kindex may-insert-fast-tracepoints
5453 @item set may-insert-fast-tracepoints on
5454 @itemx set may-insert-fast-tracepoints off
5455 This controls whether @value{GDBN} will attempt to insert fast
5456 tracepoints at the beginning of a tracing experiment. It affects only
5457 fast tracepoints, regular (non-fast) tracepoints being under the
5458 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5460 @item show may-insert-fast-tracepoints
5461 Show the current permission to insert fast tracepoints.
5463 @kindex may-interrupt
5464 @item set may-interrupt on
5465 @itemx set may-interrupt off
5466 This controls whether @value{GDBN} will attempt to interrupt or stop
5467 program execution. When this variable is @code{off}, the
5468 @code{interrupt} command will have no effect, nor will
5469 @kbd{Ctrl-c}. It defaults to @code{on}.
5471 @item show may-interrupt
5472 Show the current permission to interrupt or stop the program.
5476 @node Reverse Execution
5477 @chapter Running programs backward
5478 @cindex reverse execution
5479 @cindex running programs backward
5481 When you are debugging a program, it is not unusual to realize that
5482 you have gone too far, and some event of interest has already happened.
5483 If the target environment supports it, @value{GDBN} can allow you to
5484 ``rewind'' the program by running it backward.
5486 A target environment that supports reverse execution should be able
5487 to ``undo'' the changes in machine state that have taken place as the
5488 program was executing normally. Variables, registers etc.@: should
5489 revert to their previous values. Obviously this requires a great
5490 deal of sophistication on the part of the target environment; not
5491 all target environments can support reverse execution.
5493 When a program is executed in reverse, the instructions that
5494 have most recently been executed are ``un-executed'', in reverse
5495 order. The program counter runs backward, following the previous
5496 thread of execution in reverse. As each instruction is ``un-executed'',
5497 the values of memory and/or registers that were changed by that
5498 instruction are reverted to their previous states. After executing
5499 a piece of source code in reverse, all side effects of that code
5500 should be ``undone'', and all variables should be returned to their
5501 prior values@footnote{
5502 Note that some side effects are easier to undo than others. For instance,
5503 memory and registers are relatively easy, but device I/O is hard. Some
5504 targets may be able undo things like device I/O, and some may not.
5506 The contract between @value{GDBN} and the reverse executing target
5507 requires only that the target do something reasonable when
5508 @value{GDBN} tells it to execute backwards, and then report the
5509 results back to @value{GDBN}. Whatever the target reports back to
5510 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5511 assumes that the memory and registers that the target reports are in a
5512 consistant state, but @value{GDBN} accepts whatever it is given.
5515 If you are debugging in a target environment that supports
5516 reverse execution, @value{GDBN} provides the following commands.
5519 @kindex reverse-continue
5520 @kindex rc @r{(@code{reverse-continue})}
5521 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5522 @itemx rc @r{[}@var{ignore-count}@r{]}
5523 Beginning at the point where your program last stopped, start executing
5524 in reverse. Reverse execution will stop for breakpoints and synchronous
5525 exceptions (signals), just like normal execution. Behavior of
5526 asynchronous signals depends on the target environment.
5528 @kindex reverse-step
5529 @kindex rs @r{(@code{step})}
5530 @item reverse-step @r{[}@var{count}@r{]}
5531 Run the program backward until control reaches the start of a
5532 different source line; then stop it, and return control to @value{GDBN}.
5534 Like the @code{step} command, @code{reverse-step} will only stop
5535 at the beginning of a source line. It ``un-executes'' the previously
5536 executed source line. If the previous source line included calls to
5537 debuggable functions, @code{reverse-step} will step (backward) into
5538 the called function, stopping at the beginning of the @emph{last}
5539 statement in the called function (typically a return statement).
5541 Also, as with the @code{step} command, if non-debuggable functions are
5542 called, @code{reverse-step} will run thru them backward without stopping.
5544 @kindex reverse-stepi
5545 @kindex rsi @r{(@code{reverse-stepi})}
5546 @item reverse-stepi @r{[}@var{count}@r{]}
5547 Reverse-execute one machine instruction. Note that the instruction
5548 to be reverse-executed is @emph{not} the one pointed to by the program
5549 counter, but the instruction executed prior to that one. For instance,
5550 if the last instruction was a jump, @code{reverse-stepi} will take you
5551 back from the destination of the jump to the jump instruction itself.
5553 @kindex reverse-next
5554 @kindex rn @r{(@code{reverse-next})}
5555 @item reverse-next @r{[}@var{count}@r{]}
5556 Run backward to the beginning of the previous line executed in
5557 the current (innermost) stack frame. If the line contains function
5558 calls, they will be ``un-executed'' without stopping. Starting from
5559 the first line of a function, @code{reverse-next} will take you back
5560 to the caller of that function, @emph{before} the function was called,
5561 just as the normal @code{next} command would take you from the last
5562 line of a function back to its return to its caller
5563 @footnote{Unless the code is too heavily optimized.}.
5565 @kindex reverse-nexti
5566 @kindex rni @r{(@code{reverse-nexti})}
5567 @item reverse-nexti @r{[}@var{count}@r{]}
5568 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5569 in reverse, except that called functions are ``un-executed'' atomically.
5570 That is, if the previously executed instruction was a return from
5571 another function, @code{reverse-nexti} will continue to execute
5572 in reverse until the call to that function (from the current stack
5575 @kindex reverse-finish
5576 @item reverse-finish
5577 Just as the @code{finish} command takes you to the point where the
5578 current function returns, @code{reverse-finish} takes you to the point
5579 where it was called. Instead of ending up at the end of the current
5580 function invocation, you end up at the beginning.
5582 @kindex set exec-direction
5583 @item set exec-direction
5584 Set the direction of target execution.
5585 @itemx set exec-direction reverse
5586 @cindex execute forward or backward in time
5587 @value{GDBN} will perform all execution commands in reverse, until the
5588 exec-direction mode is changed to ``forward''. Affected commands include
5589 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5590 command cannot be used in reverse mode.
5591 @item set exec-direction forward
5592 @value{GDBN} will perform all execution commands in the normal fashion.
5593 This is the default.
5597 @node Process Record and Replay
5598 @chapter Recording Inferior's Execution and Replaying It
5599 @cindex process record and replay
5600 @cindex recording inferior's execution and replaying it
5602 On some platforms, @value{GDBN} provides a special @dfn{process record
5603 and replay} target that can record a log of the process execution, and
5604 replay it later with both forward and reverse execution commands.
5607 When this target is in use, if the execution log includes the record
5608 for the next instruction, @value{GDBN} will debug in @dfn{replay
5609 mode}. In the replay mode, the inferior does not really execute code
5610 instructions. Instead, all the events that normally happen during
5611 code execution are taken from the execution log. While code is not
5612 really executed in replay mode, the values of registers (including the
5613 program counter register) and the memory of the inferior are still
5614 changed as they normally would. Their contents are taken from the
5618 If the record for the next instruction is not in the execution log,
5619 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5620 inferior executes normally, and @value{GDBN} records the execution log
5623 The process record and replay target supports reverse execution
5624 (@pxref{Reverse Execution}), even if the platform on which the
5625 inferior runs does not. However, the reverse execution is limited in
5626 this case by the range of the instructions recorded in the execution
5627 log. In other words, reverse execution on platforms that don't
5628 support it directly can only be done in the replay mode.
5630 When debugging in the reverse direction, @value{GDBN} will work in
5631 replay mode as long as the execution log includes the record for the
5632 previous instruction; otherwise, it will work in record mode, if the
5633 platform supports reverse execution, or stop if not.
5635 For architecture environments that support process record and replay,
5636 @value{GDBN} provides the following commands:
5639 @kindex target record
5643 This command starts the process record and replay target. The process
5644 record and replay target can only debug a process that is already
5645 running. Therefore, you need first to start the process with the
5646 @kbd{run} or @kbd{start} commands, and then start the recording with
5647 the @kbd{target record} command.
5649 Both @code{record} and @code{rec} are aliases of @code{target record}.
5651 @cindex displaced stepping, and process record and replay
5652 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5653 will be automatically disabled when process record and replay target
5654 is started. That's because the process record and replay target
5655 doesn't support displaced stepping.
5657 @cindex non-stop mode, and process record and replay
5658 @cindex asynchronous execution, and process record and replay
5659 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5660 the asynchronous execution mode (@pxref{Background Execution}), the
5661 process record and replay target cannot be started because it doesn't
5662 support these two modes.
5667 Stop the process record and replay target. When process record and
5668 replay target stops, the entire execution log will be deleted and the
5669 inferior will either be terminated, or will remain in its final state.
5671 When you stop the process record and replay target in record mode (at
5672 the end of the execution log), the inferior will be stopped at the
5673 next instruction that would have been recorded. In other words, if
5674 you record for a while and then stop recording, the inferior process
5675 will be left in the same state as if the recording never happened.
5677 On the other hand, if the process record and replay target is stopped
5678 while in replay mode (that is, not at the end of the execution log,
5679 but at some earlier point), the inferior process will become ``live''
5680 at that earlier state, and it will then be possible to continue the
5681 usual ``live'' debugging of the process from that state.
5683 When the inferior process exits, or @value{GDBN} detaches from it,
5684 process record and replay target will automatically stop itself.
5687 @item record save @var{filename}
5688 Save the execution log to a file @file{@var{filename}}.
5689 Default filename is @file{gdb_record.@var{process_id}}, where
5690 @var{process_id} is the process ID of the inferior.
5692 @kindex record restore
5693 @item record restore @var{filename}
5694 Restore the execution log from a file @file{@var{filename}}.
5695 File must have been created with @code{record save}.
5697 @kindex set record insn-number-max
5698 @item set record insn-number-max @var{limit}
5699 Set the limit of instructions to be recorded. Default value is 200000.
5701 If @var{limit} is a positive number, then @value{GDBN} will start
5702 deleting instructions from the log once the number of the record
5703 instructions becomes greater than @var{limit}. For every new recorded
5704 instruction, @value{GDBN} will delete the earliest recorded
5705 instruction to keep the number of recorded instructions at the limit.
5706 (Since deleting recorded instructions loses information, @value{GDBN}
5707 lets you control what happens when the limit is reached, by means of
5708 the @code{stop-at-limit} option, described below.)
5710 If @var{limit} is zero, @value{GDBN} will never delete recorded
5711 instructions from the execution log. The number of recorded
5712 instructions is unlimited in this case.
5714 @kindex show record insn-number-max
5715 @item show record insn-number-max
5716 Show the limit of instructions to be recorded.
5718 @kindex set record stop-at-limit
5719 @item set record stop-at-limit
5720 Control the behavior when the number of recorded instructions reaches
5721 the limit. If ON (the default), @value{GDBN} will stop when the limit
5722 is reached for the first time and ask you whether you want to stop the
5723 inferior or continue running it and recording the execution log. If
5724 you decide to continue recording, each new recorded instruction will
5725 cause the oldest one to be deleted.
5727 If this option is OFF, @value{GDBN} will automatically delete the
5728 oldest record to make room for each new one, without asking.
5730 @kindex show record stop-at-limit
5731 @item show record stop-at-limit
5732 Show the current setting of @code{stop-at-limit}.
5734 @kindex set record memory-query
5735 @item set record memory-query
5736 Control the behavior when @value{GDBN} is unable to record memory
5737 changes caused by an instruction. If ON, @value{GDBN} will query
5738 whether to stop the inferior in that case.
5740 If this option is OFF (the default), @value{GDBN} will automatically
5741 ignore the effect of such instructions on memory. Later, when
5742 @value{GDBN} replays this execution log, it will mark the log of this
5743 instruction as not accessible, and it will not affect the replay
5746 @kindex show record memory-query
5747 @item show record memory-query
5748 Show the current setting of @code{memory-query}.
5752 Show various statistics about the state of process record and its
5753 in-memory execution log buffer, including:
5757 Whether in record mode or replay mode.
5759 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5761 Highest recorded instruction number.
5763 Current instruction about to be replayed (if in replay mode).
5765 Number of instructions contained in the execution log.
5767 Maximum number of instructions that may be contained in the execution log.
5770 @kindex record delete
5773 When record target runs in replay mode (``in the past''), delete the
5774 subsequent execution log and begin to record a new execution log starting
5775 from the current address. This means you will abandon the previously
5776 recorded ``future'' and begin recording a new ``future''.
5781 @chapter Examining the Stack
5783 When your program has stopped, the first thing you need to know is where it
5784 stopped and how it got there.
5787 Each time your program performs a function call, information about the call
5789 That information includes the location of the call in your program,
5790 the arguments of the call,
5791 and the local variables of the function being called.
5792 The information is saved in a block of data called a @dfn{stack frame}.
5793 The stack frames are allocated in a region of memory called the @dfn{call
5796 When your program stops, the @value{GDBN} commands for examining the
5797 stack allow you to see all of this information.
5799 @cindex selected frame
5800 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5801 @value{GDBN} commands refer implicitly to the selected frame. In
5802 particular, whenever you ask @value{GDBN} for the value of a variable in
5803 your program, the value is found in the selected frame. There are
5804 special @value{GDBN} commands to select whichever frame you are
5805 interested in. @xref{Selection, ,Selecting a Frame}.
5807 When your program stops, @value{GDBN} automatically selects the
5808 currently executing frame and describes it briefly, similar to the
5809 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5812 * Frames:: Stack frames
5813 * Backtrace:: Backtraces
5814 * Selection:: Selecting a frame
5815 * Frame Info:: Information on a frame
5820 @section Stack Frames
5822 @cindex frame, definition
5824 The call stack is divided up into contiguous pieces called @dfn{stack
5825 frames}, or @dfn{frames} for short; each frame is the data associated
5826 with one call to one function. The frame contains the arguments given
5827 to the function, the function's local variables, and the address at
5828 which the function is executing.
5830 @cindex initial frame
5831 @cindex outermost frame
5832 @cindex innermost frame
5833 When your program is started, the stack has only one frame, that of the
5834 function @code{main}. This is called the @dfn{initial} frame or the
5835 @dfn{outermost} frame. Each time a function is called, a new frame is
5836 made. Each time a function returns, the frame for that function invocation
5837 is eliminated. If a function is recursive, there can be many frames for
5838 the same function. The frame for the function in which execution is
5839 actually occurring is called the @dfn{innermost} frame. This is the most
5840 recently created of all the stack frames that still exist.
5842 @cindex frame pointer
5843 Inside your program, stack frames are identified by their addresses. A
5844 stack frame consists of many bytes, each of which has its own address; each
5845 kind of computer has a convention for choosing one byte whose
5846 address serves as the address of the frame. Usually this address is kept
5847 in a register called the @dfn{frame pointer register}
5848 (@pxref{Registers, $fp}) while execution is going on in that frame.
5850 @cindex frame number
5851 @value{GDBN} assigns numbers to all existing stack frames, starting with
5852 zero for the innermost frame, one for the frame that called it,
5853 and so on upward. These numbers do not really exist in your program;
5854 they are assigned by @value{GDBN} to give you a way of designating stack
5855 frames in @value{GDBN} commands.
5857 @c The -fomit-frame-pointer below perennially causes hbox overflow
5858 @c underflow problems.
5859 @cindex frameless execution
5860 Some compilers provide a way to compile functions so that they operate
5861 without stack frames. (For example, the @value{NGCC} option
5863 @samp{-fomit-frame-pointer}
5865 generates functions without a frame.)
5866 This is occasionally done with heavily used library functions to save
5867 the frame setup time. @value{GDBN} has limited facilities for dealing
5868 with these function invocations. If the innermost function invocation
5869 has no stack frame, @value{GDBN} nevertheless regards it as though
5870 it had a separate frame, which is numbered zero as usual, allowing
5871 correct tracing of the function call chain. However, @value{GDBN} has
5872 no provision for frameless functions elsewhere in the stack.
5875 @kindex frame@r{, command}
5876 @cindex current stack frame
5877 @item frame @var{args}
5878 The @code{frame} command allows you to move from one stack frame to another,
5879 and to print the stack frame you select. @var{args} may be either the
5880 address of the frame or the stack frame number. Without an argument,
5881 @code{frame} prints the current stack frame.
5883 @kindex select-frame
5884 @cindex selecting frame silently
5886 The @code{select-frame} command allows you to move from one stack frame
5887 to another without printing the frame. This is the silent version of
5895 @cindex call stack traces
5896 A backtrace is a summary of how your program got where it is. It shows one
5897 line per frame, for many frames, starting with the currently executing
5898 frame (frame zero), followed by its caller (frame one), and on up the
5903 @kindex bt @r{(@code{backtrace})}
5906 Print a backtrace of the entire stack: one line per frame for all
5907 frames in the stack.
5909 You can stop the backtrace at any time by typing the system interrupt
5910 character, normally @kbd{Ctrl-c}.
5912 @item backtrace @var{n}
5914 Similar, but print only the innermost @var{n} frames.
5916 @item backtrace -@var{n}
5918 Similar, but print only the outermost @var{n} frames.
5920 @item backtrace full
5922 @itemx bt full @var{n}
5923 @itemx bt full -@var{n}
5924 Print the values of the local variables also. @var{n} specifies the
5925 number of frames to print, as described above.
5930 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5931 are additional aliases for @code{backtrace}.
5933 @cindex multiple threads, backtrace
5934 In a multi-threaded program, @value{GDBN} by default shows the
5935 backtrace only for the current thread. To display the backtrace for
5936 several or all of the threads, use the command @code{thread apply}
5937 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5938 apply all backtrace}, @value{GDBN} will display the backtrace for all
5939 the threads; this is handy when you debug a core dump of a
5940 multi-threaded program.
5942 Each line in the backtrace shows the frame number and the function name.
5943 The program counter value is also shown---unless you use @code{set
5944 print address off}. The backtrace also shows the source file name and
5945 line number, as well as the arguments to the function. The program
5946 counter value is omitted if it is at the beginning of the code for that
5949 Here is an example of a backtrace. It was made with the command
5950 @samp{bt 3}, so it shows the innermost three frames.
5954 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5956 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5957 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5959 (More stack frames follow...)
5964 The display for frame zero does not begin with a program counter
5965 value, indicating that your program has stopped at the beginning of the
5966 code for line @code{993} of @code{builtin.c}.
5969 The value of parameter @code{data} in frame 1 has been replaced by
5970 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5971 only if it is a scalar (integer, pointer, enumeration, etc). See command
5972 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5973 on how to configure the way function parameter values are printed.
5975 @cindex optimized out, in backtrace
5976 @cindex function call arguments, optimized out
5977 If your program was compiled with optimizations, some compilers will
5978 optimize away arguments passed to functions if those arguments are
5979 never used after the call. Such optimizations generate code that
5980 passes arguments through registers, but doesn't store those arguments
5981 in the stack frame. @value{GDBN} has no way of displaying such
5982 arguments in stack frames other than the innermost one. Here's what
5983 such a backtrace might look like:
5987 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5989 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
5990 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
5992 (More stack frames follow...)
5997 The values of arguments that were not saved in their stack frames are
5998 shown as @samp{<optimized out>}.
6000 If you need to display the values of such optimized-out arguments,
6001 either deduce that from other variables whose values depend on the one
6002 you are interested in, or recompile without optimizations.
6004 @cindex backtrace beyond @code{main} function
6005 @cindex program entry point
6006 @cindex startup code, and backtrace
6007 Most programs have a standard user entry point---a place where system
6008 libraries and startup code transition into user code. For C this is
6009 @code{main}@footnote{
6010 Note that embedded programs (the so-called ``free-standing''
6011 environment) are not required to have a @code{main} function as the
6012 entry point. They could even have multiple entry points.}.
6013 When @value{GDBN} finds the entry function in a backtrace
6014 it will terminate the backtrace, to avoid tracing into highly
6015 system-specific (and generally uninteresting) code.
6017 If you need to examine the startup code, or limit the number of levels
6018 in a backtrace, you can change this behavior:
6021 @item set backtrace past-main
6022 @itemx set backtrace past-main on
6023 @kindex set backtrace
6024 Backtraces will continue past the user entry point.
6026 @item set backtrace past-main off
6027 Backtraces will stop when they encounter the user entry point. This is the
6030 @item show backtrace past-main
6031 @kindex show backtrace
6032 Display the current user entry point backtrace policy.
6034 @item set backtrace past-entry
6035 @itemx set backtrace past-entry on
6036 Backtraces will continue past the internal entry point of an application.
6037 This entry point is encoded by the linker when the application is built,
6038 and is likely before the user entry point @code{main} (or equivalent) is called.
6040 @item set backtrace past-entry off
6041 Backtraces will stop when they encounter the internal entry point of an
6042 application. This is the default.
6044 @item show backtrace past-entry
6045 Display the current internal entry point backtrace policy.
6047 @item set backtrace limit @var{n}
6048 @itemx set backtrace limit 0
6049 @cindex backtrace limit
6050 Limit the backtrace to @var{n} levels. A value of zero means
6053 @item show backtrace limit
6054 Display the current limit on backtrace levels.
6058 @section Selecting a Frame
6060 Most commands for examining the stack and other data in your program work on
6061 whichever stack frame is selected at the moment. Here are the commands for
6062 selecting a stack frame; all of them finish by printing a brief description
6063 of the stack frame just selected.
6066 @kindex frame@r{, selecting}
6067 @kindex f @r{(@code{frame})}
6070 Select frame number @var{n}. Recall that frame zero is the innermost
6071 (currently executing) frame, frame one is the frame that called the
6072 innermost one, and so on. The highest-numbered frame is the one for
6075 @item frame @var{addr}
6077 Select the frame at address @var{addr}. This is useful mainly if the
6078 chaining of stack frames has been damaged by a bug, making it
6079 impossible for @value{GDBN} to assign numbers properly to all frames. In
6080 addition, this can be useful when your program has multiple stacks and
6081 switches between them.
6083 On the SPARC architecture, @code{frame} needs two addresses to
6084 select an arbitrary frame: a frame pointer and a stack pointer.
6086 On the MIPS and Alpha architecture, it needs two addresses: a stack
6087 pointer and a program counter.
6089 On the 29k architecture, it needs three addresses: a register stack
6090 pointer, a program counter, and a memory stack pointer.
6094 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6095 advances toward the outermost frame, to higher frame numbers, to frames
6096 that have existed longer. @var{n} defaults to one.
6099 @kindex do @r{(@code{down})}
6101 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6102 advances toward the innermost frame, to lower frame numbers, to frames
6103 that were created more recently. @var{n} defaults to one. You may
6104 abbreviate @code{down} as @code{do}.
6107 All of these commands end by printing two lines of output describing the
6108 frame. The first line shows the frame number, the function name, the
6109 arguments, and the source file and line number of execution in that
6110 frame. The second line shows the text of that source line.
6118 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6120 10 read_input_file (argv[i]);
6124 After such a printout, the @code{list} command with no arguments
6125 prints ten lines centered on the point of execution in the frame.
6126 You can also edit the program at the point of execution with your favorite
6127 editing program by typing @code{edit}.
6128 @xref{List, ,Printing Source Lines},
6132 @kindex down-silently
6134 @item up-silently @var{n}
6135 @itemx down-silently @var{n}
6136 These two commands are variants of @code{up} and @code{down},
6137 respectively; they differ in that they do their work silently, without
6138 causing display of the new frame. They are intended primarily for use
6139 in @value{GDBN} command scripts, where the output might be unnecessary and
6144 @section Information About a Frame
6146 There are several other commands to print information about the selected
6152 When used without any argument, this command does not change which
6153 frame is selected, but prints a brief description of the currently
6154 selected stack frame. It can be abbreviated @code{f}. With an
6155 argument, this command is used to select a stack frame.
6156 @xref{Selection, ,Selecting a Frame}.
6159 @kindex info f @r{(@code{info frame})}
6162 This command prints a verbose description of the selected stack frame,
6167 the address of the frame
6169 the address of the next frame down (called by this frame)
6171 the address of the next frame up (caller of this frame)
6173 the language in which the source code corresponding to this frame is written
6175 the address of the frame's arguments
6177 the address of the frame's local variables
6179 the program counter saved in it (the address of execution in the caller frame)
6181 which registers were saved in the frame
6184 @noindent The verbose description is useful when
6185 something has gone wrong that has made the stack format fail to fit
6186 the usual conventions.
6188 @item info frame @var{addr}
6189 @itemx info f @var{addr}
6190 Print a verbose description of the frame at address @var{addr}, without
6191 selecting that frame. The selected frame remains unchanged by this
6192 command. This requires the same kind of address (more than one for some
6193 architectures) that you specify in the @code{frame} command.
6194 @xref{Selection, ,Selecting a Frame}.
6198 Print the arguments of the selected frame, each on a separate line.
6202 Print the local variables of the selected frame, each on a separate
6203 line. These are all variables (declared either static or automatic)
6204 accessible at the point of execution of the selected frame.
6207 @cindex catch exceptions, list active handlers
6208 @cindex exception handlers, how to list
6210 Print a list of all the exception handlers that are active in the
6211 current stack frame at the current point of execution. To see other
6212 exception handlers, visit the associated frame (using the @code{up},
6213 @code{down}, or @code{frame} commands); then type @code{info catch}.
6214 @xref{Set Catchpoints, , Setting Catchpoints}.
6220 @chapter Examining Source Files
6222 @value{GDBN} can print parts of your program's source, since the debugging
6223 information recorded in the program tells @value{GDBN} what source files were
6224 used to build it. When your program stops, @value{GDBN} spontaneously prints
6225 the line where it stopped. Likewise, when you select a stack frame
6226 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6227 execution in that frame has stopped. You can print other portions of
6228 source files by explicit command.
6230 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6231 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6232 @value{GDBN} under @sc{gnu} Emacs}.
6235 * List:: Printing source lines
6236 * Specify Location:: How to specify code locations
6237 * Edit:: Editing source files
6238 * Search:: Searching source files
6239 * Source Path:: Specifying source directories
6240 * Machine Code:: Source and machine code
6244 @section Printing Source Lines
6247 @kindex l @r{(@code{list})}
6248 To print lines from a source file, use the @code{list} command
6249 (abbreviated @code{l}). By default, ten lines are printed.
6250 There are several ways to specify what part of the file you want to
6251 print; see @ref{Specify Location}, for the full list.
6253 Here are the forms of the @code{list} command most commonly used:
6256 @item list @var{linenum}
6257 Print lines centered around line number @var{linenum} in the
6258 current source file.
6260 @item list @var{function}
6261 Print lines centered around the beginning of function
6265 Print more lines. If the last lines printed were printed with a
6266 @code{list} command, this prints lines following the last lines
6267 printed; however, if the last line printed was a solitary line printed
6268 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6269 Stack}), this prints lines centered around that line.
6272 Print lines just before the lines last printed.
6275 @cindex @code{list}, how many lines to display
6276 By default, @value{GDBN} prints ten source lines with any of these forms of
6277 the @code{list} command. You can change this using @code{set listsize}:
6280 @kindex set listsize
6281 @item set listsize @var{count}
6282 Make the @code{list} command display @var{count} source lines (unless
6283 the @code{list} argument explicitly specifies some other number).
6285 @kindex show listsize
6287 Display the number of lines that @code{list} prints.
6290 Repeating a @code{list} command with @key{RET} discards the argument,
6291 so it is equivalent to typing just @code{list}. This is more useful
6292 than listing the same lines again. An exception is made for an
6293 argument of @samp{-}; that argument is preserved in repetition so that
6294 each repetition moves up in the source file.
6296 In general, the @code{list} command expects you to supply zero, one or two
6297 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6298 of writing them (@pxref{Specify Location}), but the effect is always
6299 to specify some source line.
6301 Here is a complete description of the possible arguments for @code{list}:
6304 @item list @var{linespec}
6305 Print lines centered around the line specified by @var{linespec}.
6307 @item list @var{first},@var{last}
6308 Print lines from @var{first} to @var{last}. Both arguments are
6309 linespecs. When a @code{list} command has two linespecs, and the
6310 source file of the second linespec is omitted, this refers to
6311 the same source file as the first linespec.
6313 @item list ,@var{last}
6314 Print lines ending with @var{last}.
6316 @item list @var{first},
6317 Print lines starting with @var{first}.
6320 Print lines just after the lines last printed.
6323 Print lines just before the lines last printed.
6326 As described in the preceding table.
6329 @node Specify Location
6330 @section Specifying a Location
6331 @cindex specifying location
6334 Several @value{GDBN} commands accept arguments that specify a location
6335 of your program's code. Since @value{GDBN} is a source-level
6336 debugger, a location usually specifies some line in the source code;
6337 for that reason, locations are also known as @dfn{linespecs}.
6339 Here are all the different ways of specifying a code location that
6340 @value{GDBN} understands:
6344 Specifies the line number @var{linenum} of the current source file.
6347 @itemx +@var{offset}
6348 Specifies the line @var{offset} lines before or after the @dfn{current
6349 line}. For the @code{list} command, the current line is the last one
6350 printed; for the breakpoint commands, this is the line at which
6351 execution stopped in the currently selected @dfn{stack frame}
6352 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6353 used as the second of the two linespecs in a @code{list} command,
6354 this specifies the line @var{offset} lines up or down from the first
6357 @item @var{filename}:@var{linenum}
6358 Specifies the line @var{linenum} in the source file @var{filename}.
6360 @item @var{function}
6361 Specifies the line that begins the body of the function @var{function}.
6362 For example, in C, this is the line with the open brace.
6364 @item @var{function}:@var{label}
6365 Specifies the line where @var{label} appears in @var{function}.
6367 @item @var{filename}:@var{function}
6368 Specifies the line that begins the body of the function @var{function}
6369 in the file @var{filename}. You only need the file name with a
6370 function name to avoid ambiguity when there are identically named
6371 functions in different source files.
6374 Specifies the line at which the label named @var{label} appears.
6375 @value{GDBN} searches for the label in the function corresponding to
6376 the currently selected stack frame. If there is no current selected
6377 stack frame (for instance, if the inferior is not running), then
6378 @value{GDBN} will not search for a label.
6380 @item *@var{address}
6381 Specifies the program address @var{address}. For line-oriented
6382 commands, such as @code{list} and @code{edit}, this specifies a source
6383 line that contains @var{address}. For @code{break} and other
6384 breakpoint oriented commands, this can be used to set breakpoints in
6385 parts of your program which do not have debugging information or
6388 Here @var{address} may be any expression valid in the current working
6389 language (@pxref{Languages, working language}) that specifies a code
6390 address. In addition, as a convenience, @value{GDBN} extends the
6391 semantics of expressions used in locations to cover the situations
6392 that frequently happen during debugging. Here are the various forms
6396 @item @var{expression}
6397 Any expression valid in the current working language.
6399 @item @var{funcaddr}
6400 An address of a function or procedure derived from its name. In C,
6401 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6402 simply the function's name @var{function} (and actually a special case
6403 of a valid expression). In Pascal and Modula-2, this is
6404 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6405 (although the Pascal form also works).
6407 This form specifies the address of the function's first instruction,
6408 before the stack frame and arguments have been set up.
6410 @item '@var{filename}'::@var{funcaddr}
6411 Like @var{funcaddr} above, but also specifies the name of the source
6412 file explicitly. This is useful if the name of the function does not
6413 specify the function unambiguously, e.g., if there are several
6414 functions with identical names in different source files.
6421 @section Editing Source Files
6422 @cindex editing source files
6425 @kindex e @r{(@code{edit})}
6426 To edit the lines in a source file, use the @code{edit} command.
6427 The editing program of your choice
6428 is invoked with the current line set to
6429 the active line in the program.
6430 Alternatively, there are several ways to specify what part of the file you
6431 want to print if you want to see other parts of the program:
6434 @item edit @var{location}
6435 Edit the source file specified by @code{location}. Editing starts at
6436 that @var{location}, e.g., at the specified source line of the
6437 specified file. @xref{Specify Location}, for all the possible forms
6438 of the @var{location} argument; here are the forms of the @code{edit}
6439 command most commonly used:
6442 @item edit @var{number}
6443 Edit the current source file with @var{number} as the active line number.
6445 @item edit @var{function}
6446 Edit the file containing @var{function} at the beginning of its definition.
6451 @subsection Choosing your Editor
6452 You can customize @value{GDBN} to use any editor you want
6454 The only restriction is that your editor (say @code{ex}), recognizes the
6455 following command-line syntax:
6457 ex +@var{number} file
6459 The optional numeric value +@var{number} specifies the number of the line in
6460 the file where to start editing.}.
6461 By default, it is @file{@value{EDITOR}}, but you can change this
6462 by setting the environment variable @code{EDITOR} before using
6463 @value{GDBN}. For example, to configure @value{GDBN} to use the
6464 @code{vi} editor, you could use these commands with the @code{sh} shell:
6470 or in the @code{csh} shell,
6472 setenv EDITOR /usr/bin/vi
6477 @section Searching Source Files
6478 @cindex searching source files
6480 There are two commands for searching through the current source file for a
6485 @kindex forward-search
6486 @item forward-search @var{regexp}
6487 @itemx search @var{regexp}
6488 The command @samp{forward-search @var{regexp}} checks each line,
6489 starting with the one following the last line listed, for a match for
6490 @var{regexp}. It lists the line that is found. You can use the
6491 synonym @samp{search @var{regexp}} or abbreviate the command name as
6494 @kindex reverse-search
6495 @item reverse-search @var{regexp}
6496 The command @samp{reverse-search @var{regexp}} checks each line, starting
6497 with the one before the last line listed and going backward, for a match
6498 for @var{regexp}. It lists the line that is found. You can abbreviate
6499 this command as @code{rev}.
6503 @section Specifying Source Directories
6506 @cindex directories for source files
6507 Executable programs sometimes do not record the directories of the source
6508 files from which they were compiled, just the names. Even when they do,
6509 the directories could be moved between the compilation and your debugging
6510 session. @value{GDBN} has a list of directories to search for source files;
6511 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6512 it tries all the directories in the list, in the order they are present
6513 in the list, until it finds a file with the desired name.
6515 For example, suppose an executable references the file
6516 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6517 @file{/mnt/cross}. The file is first looked up literally; if this
6518 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6519 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6520 message is printed. @value{GDBN} does not look up the parts of the
6521 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6522 Likewise, the subdirectories of the source path are not searched: if
6523 the source path is @file{/mnt/cross}, and the binary refers to
6524 @file{foo.c}, @value{GDBN} would not find it under
6525 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6527 Plain file names, relative file names with leading directories, file
6528 names containing dots, etc.@: are all treated as described above; for
6529 instance, if the source path is @file{/mnt/cross}, and the source file
6530 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6531 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6532 that---@file{/mnt/cross/foo.c}.
6534 Note that the executable search path is @emph{not} used to locate the
6537 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6538 any information it has cached about where source files are found and where
6539 each line is in the file.
6543 When you start @value{GDBN}, its source path includes only @samp{cdir}
6544 and @samp{cwd}, in that order.
6545 To add other directories, use the @code{directory} command.
6547 The search path is used to find both program source files and @value{GDBN}
6548 script files (read using the @samp{-command} option and @samp{source} command).
6550 In addition to the source path, @value{GDBN} provides a set of commands
6551 that manage a list of source path substitution rules. A @dfn{substitution
6552 rule} specifies how to rewrite source directories stored in the program's
6553 debug information in case the sources were moved to a different
6554 directory between compilation and debugging. A rule is made of
6555 two strings, the first specifying what needs to be rewritten in
6556 the path, and the second specifying how it should be rewritten.
6557 In @ref{set substitute-path}, we name these two parts @var{from} and
6558 @var{to} respectively. @value{GDBN} does a simple string replacement
6559 of @var{from} with @var{to} at the start of the directory part of the
6560 source file name, and uses that result instead of the original file
6561 name to look up the sources.
6563 Using the previous example, suppose the @file{foo-1.0} tree has been
6564 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6565 @value{GDBN} to replace @file{/usr/src} in all source path names with
6566 @file{/mnt/cross}. The first lookup will then be
6567 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6568 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6569 substitution rule, use the @code{set substitute-path} command
6570 (@pxref{set substitute-path}).
6572 To avoid unexpected substitution results, a rule is applied only if the
6573 @var{from} part of the directory name ends at a directory separator.
6574 For instance, a rule substituting @file{/usr/source} into
6575 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6576 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6577 is applied only at the beginning of the directory name, this rule will
6578 not be applied to @file{/root/usr/source/baz.c} either.
6580 In many cases, you can achieve the same result using the @code{directory}
6581 command. However, @code{set substitute-path} can be more efficient in
6582 the case where the sources are organized in a complex tree with multiple
6583 subdirectories. With the @code{directory} command, you need to add each
6584 subdirectory of your project. If you moved the entire tree while
6585 preserving its internal organization, then @code{set substitute-path}
6586 allows you to direct the debugger to all the sources with one single
6589 @code{set substitute-path} is also more than just a shortcut command.
6590 The source path is only used if the file at the original location no
6591 longer exists. On the other hand, @code{set substitute-path} modifies
6592 the debugger behavior to look at the rewritten location instead. So, if
6593 for any reason a source file that is not relevant to your executable is
6594 located at the original location, a substitution rule is the only
6595 method available to point @value{GDBN} at the new location.
6597 @cindex @samp{--with-relocated-sources}
6598 @cindex default source path substitution
6599 You can configure a default source path substitution rule by
6600 configuring @value{GDBN} with the
6601 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6602 should be the name of a directory under @value{GDBN}'s configured
6603 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6604 directory names in debug information under @var{dir} will be adjusted
6605 automatically if the installed @value{GDBN} is moved to a new
6606 location. This is useful if @value{GDBN}, libraries or executables
6607 with debug information and corresponding source code are being moved
6611 @item directory @var{dirname} @dots{}
6612 @item dir @var{dirname} @dots{}
6613 Add directory @var{dirname} to the front of the source path. Several
6614 directory names may be given to this command, separated by @samp{:}
6615 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6616 part of absolute file names) or
6617 whitespace. You may specify a directory that is already in the source
6618 path; this moves it forward, so @value{GDBN} searches it sooner.
6622 @vindex $cdir@r{, convenience variable}
6623 @vindex $cwd@r{, convenience variable}
6624 @cindex compilation directory
6625 @cindex current directory
6626 @cindex working directory
6627 @cindex directory, current
6628 @cindex directory, compilation
6629 You can use the string @samp{$cdir} to refer to the compilation
6630 directory (if one is recorded), and @samp{$cwd} to refer to the current
6631 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6632 tracks the current working directory as it changes during your @value{GDBN}
6633 session, while the latter is immediately expanded to the current
6634 directory at the time you add an entry to the source path.
6637 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6639 @c RET-repeat for @code{directory} is explicitly disabled, but since
6640 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6642 @item set directories @var{path-list}
6643 @kindex set directories
6644 Set the source path to @var{path-list}.
6645 @samp{$cdir:$cwd} are added if missing.
6647 @item show directories
6648 @kindex show directories
6649 Print the source path: show which directories it contains.
6651 @anchor{set substitute-path}
6652 @item set substitute-path @var{from} @var{to}
6653 @kindex set substitute-path
6654 Define a source path substitution rule, and add it at the end of the
6655 current list of existing substitution rules. If a rule with the same
6656 @var{from} was already defined, then the old rule is also deleted.
6658 For example, if the file @file{/foo/bar/baz.c} was moved to
6659 @file{/mnt/cross/baz.c}, then the command
6662 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6666 will tell @value{GDBN} to replace @samp{/usr/src} with
6667 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6668 @file{baz.c} even though it was moved.
6670 In the case when more than one substitution rule have been defined,
6671 the rules are evaluated one by one in the order where they have been
6672 defined. The first one matching, if any, is selected to perform
6675 For instance, if we had entered the following commands:
6678 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6679 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6683 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6684 @file{/mnt/include/defs.h} by using the first rule. However, it would
6685 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6686 @file{/mnt/src/lib/foo.c}.
6689 @item unset substitute-path [path]
6690 @kindex unset substitute-path
6691 If a path is specified, search the current list of substitution rules
6692 for a rule that would rewrite that path. Delete that rule if found.
6693 A warning is emitted by the debugger if no rule could be found.
6695 If no path is specified, then all substitution rules are deleted.
6697 @item show substitute-path [path]
6698 @kindex show substitute-path
6699 If a path is specified, then print the source path substitution rule
6700 which would rewrite that path, if any.
6702 If no path is specified, then print all existing source path substitution
6707 If your source path is cluttered with directories that are no longer of
6708 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6709 versions of source. You can correct the situation as follows:
6713 Use @code{directory} with no argument to reset the source path to its default value.
6716 Use @code{directory} with suitable arguments to reinstall the
6717 directories you want in the source path. You can add all the
6718 directories in one command.
6722 @section Source and Machine Code
6723 @cindex source line and its code address
6725 You can use the command @code{info line} to map source lines to program
6726 addresses (and vice versa), and the command @code{disassemble} to display
6727 a range of addresses as machine instructions. You can use the command
6728 @code{set disassemble-next-line} to set whether to disassemble next
6729 source line when execution stops. When run under @sc{gnu} Emacs
6730 mode, the @code{info line} command causes the arrow to point to the
6731 line specified. Also, @code{info line} prints addresses in symbolic form as
6736 @item info line @var{linespec}
6737 Print the starting and ending addresses of the compiled code for
6738 source line @var{linespec}. You can specify source lines in any of
6739 the ways documented in @ref{Specify Location}.
6742 For example, we can use @code{info line} to discover the location of
6743 the object code for the first line of function
6744 @code{m4_changequote}:
6746 @c FIXME: I think this example should also show the addresses in
6747 @c symbolic form, as they usually would be displayed.
6749 (@value{GDBP}) info line m4_changequote
6750 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6754 @cindex code address and its source line
6755 We can also inquire (using @code{*@var{addr}} as the form for
6756 @var{linespec}) what source line covers a particular address:
6758 (@value{GDBP}) info line *0x63ff
6759 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6762 @cindex @code{$_} and @code{info line}
6763 @cindex @code{x} command, default address
6764 @kindex x@r{(examine), and} info line
6765 After @code{info line}, the default address for the @code{x} command
6766 is changed to the starting address of the line, so that @samp{x/i} is
6767 sufficient to begin examining the machine code (@pxref{Memory,
6768 ,Examining Memory}). Also, this address is saved as the value of the
6769 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6774 @cindex assembly instructions
6775 @cindex instructions, assembly
6776 @cindex machine instructions
6777 @cindex listing machine instructions
6779 @itemx disassemble /m
6780 @itemx disassemble /r
6781 This specialized command dumps a range of memory as machine
6782 instructions. It can also print mixed source+disassembly by specifying
6783 the @code{/m} modifier and print the raw instructions in hex as well as
6784 in symbolic form by specifying the @code{/r}.
6785 The default memory range is the function surrounding the
6786 program counter of the selected frame. A single argument to this
6787 command is a program counter value; @value{GDBN} dumps the function
6788 surrounding this value. When two arguments are given, they should
6789 be separated by a comma, possibly surrounded by whitespace. The
6790 arguments specify a range of addresses to dump, in one of two forms:
6793 @item @var{start},@var{end}
6794 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6795 @item @var{start},+@var{length}
6796 the addresses from @var{start} (inclusive) to
6797 @code{@var{start}+@var{length}} (exclusive).
6801 When 2 arguments are specified, the name of the function is also
6802 printed (since there could be several functions in the given range).
6804 The argument(s) can be any expression yielding a numeric value, such as
6805 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6807 If the range of memory being disassembled contains current program counter,
6808 the instruction at that location is shown with a @code{=>} marker.
6811 The following example shows the disassembly of a range of addresses of
6812 HP PA-RISC 2.0 code:
6815 (@value{GDBP}) disas 0x32c4, 0x32e4
6816 Dump of assembler code from 0x32c4 to 0x32e4:
6817 0x32c4 <main+204>: addil 0,dp
6818 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6819 0x32cc <main+212>: ldil 0x3000,r31
6820 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6821 0x32d4 <main+220>: ldo 0(r31),rp
6822 0x32d8 <main+224>: addil -0x800,dp
6823 0x32dc <main+228>: ldo 0x588(r1),r26
6824 0x32e0 <main+232>: ldil 0x3000,r31
6825 End of assembler dump.
6828 Here is an example showing mixed source+assembly for Intel x86, when the
6829 program is stopped just after function prologue:
6832 (@value{GDBP}) disas /m main
6833 Dump of assembler code for function main:
6835 0x08048330 <+0>: push %ebp
6836 0x08048331 <+1>: mov %esp,%ebp
6837 0x08048333 <+3>: sub $0x8,%esp
6838 0x08048336 <+6>: and $0xfffffff0,%esp
6839 0x08048339 <+9>: sub $0x10,%esp
6841 6 printf ("Hello.\n");
6842 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6843 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6847 0x08048348 <+24>: mov $0x0,%eax
6848 0x0804834d <+29>: leave
6849 0x0804834e <+30>: ret
6851 End of assembler dump.
6854 Here is another example showing raw instructions in hex for AMD x86-64,
6857 (gdb) disas /r 0x400281,+10
6858 Dump of assembler code from 0x400281 to 0x40028b:
6859 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6860 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6861 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6862 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6863 End of assembler dump.
6866 Some architectures have more than one commonly-used set of instruction
6867 mnemonics or other syntax.
6869 For programs that were dynamically linked and use shared libraries,
6870 instructions that call functions or branch to locations in the shared
6871 libraries might show a seemingly bogus location---it's actually a
6872 location of the relocation table. On some architectures, @value{GDBN}
6873 might be able to resolve these to actual function names.
6876 @kindex set disassembly-flavor
6877 @cindex Intel disassembly flavor
6878 @cindex AT&T disassembly flavor
6879 @item set disassembly-flavor @var{instruction-set}
6880 Select the instruction set to use when disassembling the
6881 program via the @code{disassemble} or @code{x/i} commands.
6883 Currently this command is only defined for the Intel x86 family. You
6884 can set @var{instruction-set} to either @code{intel} or @code{att}.
6885 The default is @code{att}, the AT&T flavor used by default by Unix
6886 assemblers for x86-based targets.
6888 @kindex show disassembly-flavor
6889 @item show disassembly-flavor
6890 Show the current setting of the disassembly flavor.
6894 @kindex set disassemble-next-line
6895 @kindex show disassemble-next-line
6896 @item set disassemble-next-line
6897 @itemx show disassemble-next-line
6898 Control whether or not @value{GDBN} will disassemble the next source
6899 line or instruction when execution stops. If ON, @value{GDBN} will
6900 display disassembly of the next source line when execution of the
6901 program being debugged stops. This is @emph{in addition} to
6902 displaying the source line itself, which @value{GDBN} always does if
6903 possible. If the next source line cannot be displayed for some reason
6904 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6905 info in the debug info), @value{GDBN} will display disassembly of the
6906 next @emph{instruction} instead of showing the next source line. If
6907 AUTO, @value{GDBN} will display disassembly of next instruction only
6908 if the source line cannot be displayed. This setting causes
6909 @value{GDBN} to display some feedback when you step through a function
6910 with no line info or whose source file is unavailable. The default is
6911 OFF, which means never display the disassembly of the next line or
6917 @chapter Examining Data
6919 @cindex printing data
6920 @cindex examining data
6923 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6924 @c document because it is nonstandard... Under Epoch it displays in a
6925 @c different window or something like that.
6926 The usual way to examine data in your program is with the @code{print}
6927 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6928 evaluates and prints the value of an expression of the language your
6929 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6930 Different Languages}). It may also print the expression using a
6931 Python-based pretty-printer (@pxref{Pretty Printing}).
6934 @item print @var{expr}
6935 @itemx print /@var{f} @var{expr}
6936 @var{expr} is an expression (in the source language). By default the
6937 value of @var{expr} is printed in a format appropriate to its data type;
6938 you can choose a different format by specifying @samp{/@var{f}}, where
6939 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6943 @itemx print /@var{f}
6944 @cindex reprint the last value
6945 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6946 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6947 conveniently inspect the same value in an alternative format.
6950 A more low-level way of examining data is with the @code{x} command.
6951 It examines data in memory at a specified address and prints it in a
6952 specified format. @xref{Memory, ,Examining Memory}.
6954 If you are interested in information about types, or about how the
6955 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6956 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6960 * Expressions:: Expressions
6961 * Ambiguous Expressions:: Ambiguous Expressions
6962 * Variables:: Program variables
6963 * Arrays:: Artificial arrays
6964 * Output Formats:: Output formats
6965 * Memory:: Examining memory
6966 * Auto Display:: Automatic display
6967 * Print Settings:: Print settings
6968 * Pretty Printing:: Python pretty printing
6969 * Value History:: Value history
6970 * Convenience Vars:: Convenience variables
6971 * Registers:: Registers
6972 * Floating Point Hardware:: Floating point hardware
6973 * Vector Unit:: Vector Unit
6974 * OS Information:: Auxiliary data provided by operating system
6975 * Memory Region Attributes:: Memory region attributes
6976 * Dump/Restore Files:: Copy between memory and a file
6977 * Core File Generation:: Cause a program dump its core
6978 * Character Sets:: Debugging programs that use a different
6979 character set than GDB does
6980 * Caching Remote Data:: Data caching for remote targets
6981 * Searching Memory:: Searching memory for a sequence of bytes
6985 @section Expressions
6988 @code{print} and many other @value{GDBN} commands accept an expression and
6989 compute its value. Any kind of constant, variable or operator defined
6990 by the programming language you are using is valid in an expression in
6991 @value{GDBN}. This includes conditional expressions, function calls,
6992 casts, and string constants. It also includes preprocessor macros, if
6993 you compiled your program to include this information; see
6996 @cindex arrays in expressions
6997 @value{GDBN} supports array constants in expressions input by
6998 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6999 you can use the command @code{print @{1, 2, 3@}} to create an array
7000 of three integers. If you pass an array to a function or assign it
7001 to a program variable, @value{GDBN} copies the array to memory that
7002 is @code{malloc}ed in the target program.
7004 Because C is so widespread, most of the expressions shown in examples in
7005 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7006 Languages}, for information on how to use expressions in other
7009 In this section, we discuss operators that you can use in @value{GDBN}
7010 expressions regardless of your programming language.
7012 @cindex casts, in expressions
7013 Casts are supported in all languages, not just in C, because it is so
7014 useful to cast a number into a pointer in order to examine a structure
7015 at that address in memory.
7016 @c FIXME: casts supported---Mod2 true?
7018 @value{GDBN} supports these operators, in addition to those common
7019 to programming languages:
7023 @samp{@@} is a binary operator for treating parts of memory as arrays.
7024 @xref{Arrays, ,Artificial Arrays}, for more information.
7027 @samp{::} allows you to specify a variable in terms of the file or
7028 function where it is defined. @xref{Variables, ,Program Variables}.
7030 @cindex @{@var{type}@}
7031 @cindex type casting memory
7032 @cindex memory, viewing as typed object
7033 @cindex casts, to view memory
7034 @item @{@var{type}@} @var{addr}
7035 Refers to an object of type @var{type} stored at address @var{addr} in
7036 memory. @var{addr} may be any expression whose value is an integer or
7037 pointer (but parentheses are required around binary operators, just as in
7038 a cast). This construct is allowed regardless of what kind of data is
7039 normally supposed to reside at @var{addr}.
7042 @node Ambiguous Expressions
7043 @section Ambiguous Expressions
7044 @cindex ambiguous expressions
7046 Expressions can sometimes contain some ambiguous elements. For instance,
7047 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7048 a single function name to be defined several times, for application in
7049 different contexts. This is called @dfn{overloading}. Another example
7050 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7051 templates and is typically instantiated several times, resulting in
7052 the same function name being defined in different contexts.
7054 In some cases and depending on the language, it is possible to adjust
7055 the expression to remove the ambiguity. For instance in C@t{++}, you
7056 can specify the signature of the function you want to break on, as in
7057 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7058 qualified name of your function often makes the expression unambiguous
7061 When an ambiguity that needs to be resolved is detected, the debugger
7062 has the capability to display a menu of numbered choices for each
7063 possibility, and then waits for the selection with the prompt @samp{>}.
7064 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7065 aborts the current command. If the command in which the expression was
7066 used allows more than one choice to be selected, the next option in the
7067 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7070 For example, the following session excerpt shows an attempt to set a
7071 breakpoint at the overloaded symbol @code{String::after}.
7072 We choose three particular definitions of that function name:
7074 @c FIXME! This is likely to change to show arg type lists, at least
7077 (@value{GDBP}) b String::after
7080 [2] file:String.cc; line number:867
7081 [3] file:String.cc; line number:860
7082 [4] file:String.cc; line number:875
7083 [5] file:String.cc; line number:853
7084 [6] file:String.cc; line number:846
7085 [7] file:String.cc; line number:735
7087 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7088 Breakpoint 2 at 0xb344: file String.cc, line 875.
7089 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7090 Multiple breakpoints were set.
7091 Use the "delete" command to delete unwanted
7098 @kindex set multiple-symbols
7099 @item set multiple-symbols @var{mode}
7100 @cindex multiple-symbols menu
7102 This option allows you to adjust the debugger behavior when an expression
7105 By default, @var{mode} is set to @code{all}. If the command with which
7106 the expression is used allows more than one choice, then @value{GDBN}
7107 automatically selects all possible choices. For instance, inserting
7108 a breakpoint on a function using an ambiguous name results in a breakpoint
7109 inserted on each possible match. However, if a unique choice must be made,
7110 then @value{GDBN} uses the menu to help you disambiguate the expression.
7111 For instance, printing the address of an overloaded function will result
7112 in the use of the menu.
7114 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7115 when an ambiguity is detected.
7117 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7118 an error due to the ambiguity and the command is aborted.
7120 @kindex show multiple-symbols
7121 @item show multiple-symbols
7122 Show the current value of the @code{multiple-symbols} setting.
7126 @section Program Variables
7128 The most common kind of expression to use is the name of a variable
7131 Variables in expressions are understood in the selected stack frame
7132 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7136 global (or file-static)
7143 visible according to the scope rules of the
7144 programming language from the point of execution in that frame
7147 @noindent This means that in the function
7162 you can examine and use the variable @code{a} whenever your program is
7163 executing within the function @code{foo}, but you can only use or
7164 examine the variable @code{b} while your program is executing inside
7165 the block where @code{b} is declared.
7167 @cindex variable name conflict
7168 There is an exception: you can refer to a variable or function whose
7169 scope is a single source file even if the current execution point is not
7170 in this file. But it is possible to have more than one such variable or
7171 function with the same name (in different source files). If that
7172 happens, referring to that name has unpredictable effects. If you wish,
7173 you can specify a static variable in a particular function or file,
7174 using the colon-colon (@code{::}) notation:
7176 @cindex colon-colon, context for variables/functions
7178 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7179 @cindex @code{::}, context for variables/functions
7182 @var{file}::@var{variable}
7183 @var{function}::@var{variable}
7187 Here @var{file} or @var{function} is the name of the context for the
7188 static @var{variable}. In the case of file names, you can use quotes to
7189 make sure @value{GDBN} parses the file name as a single word---for example,
7190 to print a global value of @code{x} defined in @file{f2.c}:
7193 (@value{GDBP}) p 'f2.c'::x
7196 @cindex C@t{++} scope resolution
7197 This use of @samp{::} is very rarely in conflict with the very similar
7198 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7199 scope resolution operator in @value{GDBN} expressions.
7200 @c FIXME: Um, so what happens in one of those rare cases where it's in
7203 @cindex wrong values
7204 @cindex variable values, wrong
7205 @cindex function entry/exit, wrong values of variables
7206 @cindex optimized code, wrong values of variables
7208 @emph{Warning:} Occasionally, a local variable may appear to have the
7209 wrong value at certain points in a function---just after entry to a new
7210 scope, and just before exit.
7212 You may see this problem when you are stepping by machine instructions.
7213 This is because, on most machines, it takes more than one instruction to
7214 set up a stack frame (including local variable definitions); if you are
7215 stepping by machine instructions, variables may appear to have the wrong
7216 values until the stack frame is completely built. On exit, it usually
7217 also takes more than one machine instruction to destroy a stack frame;
7218 after you begin stepping through that group of instructions, local
7219 variable definitions may be gone.
7221 This may also happen when the compiler does significant optimizations.
7222 To be sure of always seeing accurate values, turn off all optimization
7225 @cindex ``No symbol "foo" in current context''
7226 Another possible effect of compiler optimizations is to optimize
7227 unused variables out of existence, or assign variables to registers (as
7228 opposed to memory addresses). Depending on the support for such cases
7229 offered by the debug info format used by the compiler, @value{GDBN}
7230 might not be able to display values for such local variables. If that
7231 happens, @value{GDBN} will print a message like this:
7234 No symbol "foo" in current context.
7237 To solve such problems, either recompile without optimizations, or use a
7238 different debug info format, if the compiler supports several such
7239 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7240 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7241 produces debug info in a format that is superior to formats such as
7242 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7243 an effective form for debug info. @xref{Debugging Options,,Options
7244 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7245 Compiler Collection (GCC)}.
7246 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7247 that are best suited to C@t{++} programs.
7249 If you ask to print an object whose contents are unknown to
7250 @value{GDBN}, e.g., because its data type is not completely specified
7251 by the debug information, @value{GDBN} will say @samp{<incomplete
7252 type>}. @xref{Symbols, incomplete type}, for more about this.
7254 Strings are identified as arrays of @code{char} values without specified
7255 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7256 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7257 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7258 defines literal string type @code{"char"} as @code{char} without a sign.
7263 signed char var1[] = "A";
7266 You get during debugging
7271 $2 = @{65 'A', 0 '\0'@}
7275 @section Artificial Arrays
7277 @cindex artificial array
7279 @kindex @@@r{, referencing memory as an array}
7280 It is often useful to print out several successive objects of the
7281 same type in memory; a section of an array, or an array of
7282 dynamically determined size for which only a pointer exists in the
7285 You can do this by referring to a contiguous span of memory as an
7286 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7287 operand of @samp{@@} should be the first element of the desired array
7288 and be an individual object. The right operand should be the desired length
7289 of the array. The result is an array value whose elements are all of
7290 the type of the left argument. The first element is actually the left
7291 argument; the second element comes from bytes of memory immediately
7292 following those that hold the first element, and so on. Here is an
7293 example. If a program says
7296 int *array = (int *) malloc (len * sizeof (int));
7300 you can print the contents of @code{array} with
7306 The left operand of @samp{@@} must reside in memory. Array values made
7307 with @samp{@@} in this way behave just like other arrays in terms of
7308 subscripting, and are coerced to pointers when used in expressions.
7309 Artificial arrays most often appear in expressions via the value history
7310 (@pxref{Value History, ,Value History}), after printing one out.
7312 Another way to create an artificial array is to use a cast.
7313 This re-interprets a value as if it were an array.
7314 The value need not be in memory:
7316 (@value{GDBP}) p/x (short[2])0x12345678
7317 $1 = @{0x1234, 0x5678@}
7320 As a convenience, if you leave the array length out (as in
7321 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7322 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7324 (@value{GDBP}) p/x (short[])0x12345678
7325 $2 = @{0x1234, 0x5678@}
7328 Sometimes the artificial array mechanism is not quite enough; in
7329 moderately complex data structures, the elements of interest may not
7330 actually be adjacent---for example, if you are interested in the values
7331 of pointers in an array. One useful work-around in this situation is
7332 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7333 Variables}) as a counter in an expression that prints the first
7334 interesting value, and then repeat that expression via @key{RET}. For
7335 instance, suppose you have an array @code{dtab} of pointers to
7336 structures, and you are interested in the values of a field @code{fv}
7337 in each structure. Here is an example of what you might type:
7347 @node Output Formats
7348 @section Output Formats
7350 @cindex formatted output
7351 @cindex output formats
7352 By default, @value{GDBN} prints a value according to its data type. Sometimes
7353 this is not what you want. For example, you might want to print a number
7354 in hex, or a pointer in decimal. Or you might want to view data in memory
7355 at a certain address as a character string or as an instruction. To do
7356 these things, specify an @dfn{output format} when you print a value.
7358 The simplest use of output formats is to say how to print a value
7359 already computed. This is done by starting the arguments of the
7360 @code{print} command with a slash and a format letter. The format
7361 letters supported are:
7365 Regard the bits of the value as an integer, and print the integer in
7369 Print as integer in signed decimal.
7372 Print as integer in unsigned decimal.
7375 Print as integer in octal.
7378 Print as integer in binary. The letter @samp{t} stands for ``two''.
7379 @footnote{@samp{b} cannot be used because these format letters are also
7380 used with the @code{x} command, where @samp{b} stands for ``byte'';
7381 see @ref{Memory,,Examining Memory}.}
7384 @cindex unknown address, locating
7385 @cindex locate address
7386 Print as an address, both absolute in hexadecimal and as an offset from
7387 the nearest preceding symbol. You can use this format used to discover
7388 where (in what function) an unknown address is located:
7391 (@value{GDBP}) p/a 0x54320
7392 $3 = 0x54320 <_initialize_vx+396>
7396 The command @code{info symbol 0x54320} yields similar results.
7397 @xref{Symbols, info symbol}.
7400 Regard as an integer and print it as a character constant. This
7401 prints both the numerical value and its character representation. The
7402 character representation is replaced with the octal escape @samp{\nnn}
7403 for characters outside the 7-bit @sc{ascii} range.
7405 Without this format, @value{GDBN} displays @code{char},
7406 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7407 constants. Single-byte members of vectors are displayed as integer
7411 Regard the bits of the value as a floating point number and print
7412 using typical floating point syntax.
7415 @cindex printing strings
7416 @cindex printing byte arrays
7417 Regard as a string, if possible. With this format, pointers to single-byte
7418 data are displayed as null-terminated strings and arrays of single-byte data
7419 are displayed as fixed-length strings. Other values are displayed in their
7422 Without this format, @value{GDBN} displays pointers to and arrays of
7423 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7424 strings. Single-byte members of a vector are displayed as an integer
7428 @cindex raw printing
7429 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7430 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7431 Printing}). This typically results in a higher-level display of the
7432 value's contents. The @samp{r} format bypasses any Python
7433 pretty-printer which might exist.
7436 For example, to print the program counter in hex (@pxref{Registers}), type
7443 Note that no space is required before the slash; this is because command
7444 names in @value{GDBN} cannot contain a slash.
7446 To reprint the last value in the value history with a different format,
7447 you can use the @code{print} command with just a format and no
7448 expression. For example, @samp{p/x} reprints the last value in hex.
7451 @section Examining Memory
7453 You can use the command @code{x} (for ``examine'') to examine memory in
7454 any of several formats, independently of your program's data types.
7456 @cindex examining memory
7458 @kindex x @r{(examine memory)}
7459 @item x/@var{nfu} @var{addr}
7462 Use the @code{x} command to examine memory.
7465 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7466 much memory to display and how to format it; @var{addr} is an
7467 expression giving the address where you want to start displaying memory.
7468 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7469 Several commands set convenient defaults for @var{addr}.
7472 @item @var{n}, the repeat count
7473 The repeat count is a decimal integer; the default is 1. It specifies
7474 how much memory (counting by units @var{u}) to display.
7475 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7478 @item @var{f}, the display format
7479 The display format is one of the formats used by @code{print}
7480 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7481 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7482 The default is @samp{x} (hexadecimal) initially. The default changes
7483 each time you use either @code{x} or @code{print}.
7485 @item @var{u}, the unit size
7486 The unit size is any of
7492 Halfwords (two bytes).
7494 Words (four bytes). This is the initial default.
7496 Giant words (eight bytes).
7499 Each time you specify a unit size with @code{x}, that size becomes the
7500 default unit the next time you use @code{x}. For the @samp{i} format,
7501 the unit size is ignored and is normally not written. For the @samp{s} format,
7502 the unit size defaults to @samp{b}, unless it is explicitly given.
7503 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7504 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7505 Note that the results depend on the programming language of the
7506 current compilation unit. If the language is C, the @samp{s}
7507 modifier will use the UTF-16 encoding while @samp{w} will use
7508 UTF-32. The encoding is set by the programming language and cannot
7511 @item @var{addr}, starting display address
7512 @var{addr} is the address where you want @value{GDBN} to begin displaying
7513 memory. The expression need not have a pointer value (though it may);
7514 it is always interpreted as an integer address of a byte of memory.
7515 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7516 @var{addr} is usually just after the last address examined---but several
7517 other commands also set the default address: @code{info breakpoints} (to
7518 the address of the last breakpoint listed), @code{info line} (to the
7519 starting address of a line), and @code{print} (if you use it to display
7520 a value from memory).
7523 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7524 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7525 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7526 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7527 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7529 Since the letters indicating unit sizes are all distinct from the
7530 letters specifying output formats, you do not have to remember whether
7531 unit size or format comes first; either order works. The output
7532 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7533 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7535 Even though the unit size @var{u} is ignored for the formats @samp{s}
7536 and @samp{i}, you might still want to use a count @var{n}; for example,
7537 @samp{3i} specifies that you want to see three machine instructions,
7538 including any operands. For convenience, especially when used with
7539 the @code{display} command, the @samp{i} format also prints branch delay
7540 slot instructions, if any, beyond the count specified, which immediately
7541 follow the last instruction that is within the count. The command
7542 @code{disassemble} gives an alternative way of inspecting machine
7543 instructions; see @ref{Machine Code,,Source and Machine Code}.
7545 All the defaults for the arguments to @code{x} are designed to make it
7546 easy to continue scanning memory with minimal specifications each time
7547 you use @code{x}. For example, after you have inspected three machine
7548 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7549 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7550 the repeat count @var{n} is used again; the other arguments default as
7551 for successive uses of @code{x}.
7553 When examining machine instructions, the instruction at current program
7554 counter is shown with a @code{=>} marker. For example:
7557 (@value{GDBP}) x/5i $pc-6
7558 0x804837f <main+11>: mov %esp,%ebp
7559 0x8048381 <main+13>: push %ecx
7560 0x8048382 <main+14>: sub $0x4,%esp
7561 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7562 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7565 @cindex @code{$_}, @code{$__}, and value history
7566 The addresses and contents printed by the @code{x} command are not saved
7567 in the value history because there is often too much of them and they
7568 would get in the way. Instead, @value{GDBN} makes these values available for
7569 subsequent use in expressions as values of the convenience variables
7570 @code{$_} and @code{$__}. After an @code{x} command, the last address
7571 examined is available for use in expressions in the convenience variable
7572 @code{$_}. The contents of that address, as examined, are available in
7573 the convenience variable @code{$__}.
7575 If the @code{x} command has a repeat count, the address and contents saved
7576 are from the last memory unit printed; this is not the same as the last
7577 address printed if several units were printed on the last line of output.
7579 @cindex remote memory comparison
7580 @cindex verify remote memory image
7581 When you are debugging a program running on a remote target machine
7582 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7583 remote machine's memory against the executable file you downloaded to
7584 the target. The @code{compare-sections} command is provided for such
7588 @kindex compare-sections
7589 @item compare-sections @r{[}@var{section-name}@r{]}
7590 Compare the data of a loadable section @var{section-name} in the
7591 executable file of the program being debugged with the same section in
7592 the remote machine's memory, and report any mismatches. With no
7593 arguments, compares all loadable sections. This command's
7594 availability depends on the target's support for the @code{"qCRC"}
7599 @section Automatic Display
7600 @cindex automatic display
7601 @cindex display of expressions
7603 If you find that you want to print the value of an expression frequently
7604 (to see how it changes), you might want to add it to the @dfn{automatic
7605 display list} so that @value{GDBN} prints its value each time your program stops.
7606 Each expression added to the list is given a number to identify it;
7607 to remove an expression from the list, you specify that number.
7608 The automatic display looks like this:
7612 3: bar[5] = (struct hack *) 0x3804
7616 This display shows item numbers, expressions and their current values. As with
7617 displays you request manually using @code{x} or @code{print}, you can
7618 specify the output format you prefer; in fact, @code{display} decides
7619 whether to use @code{print} or @code{x} depending your format
7620 specification---it uses @code{x} if you specify either the @samp{i}
7621 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7625 @item display @var{expr}
7626 Add the expression @var{expr} to the list of expressions to display
7627 each time your program stops. @xref{Expressions, ,Expressions}.
7629 @code{display} does not repeat if you press @key{RET} again after using it.
7631 @item display/@var{fmt} @var{expr}
7632 For @var{fmt} specifying only a display format and not a size or
7633 count, add the expression @var{expr} to the auto-display list but
7634 arrange to display it each time in the specified format @var{fmt}.
7635 @xref{Output Formats,,Output Formats}.
7637 @item display/@var{fmt} @var{addr}
7638 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7639 number of units, add the expression @var{addr} as a memory address to
7640 be examined each time your program stops. Examining means in effect
7641 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7644 For example, @samp{display/i $pc} can be helpful, to see the machine
7645 instruction about to be executed each time execution stops (@samp{$pc}
7646 is a common name for the program counter; @pxref{Registers, ,Registers}).
7649 @kindex delete display
7651 @item undisplay @var{dnums}@dots{}
7652 @itemx delete display @var{dnums}@dots{}
7653 Remove items from the list of expressions to display. Specify the
7654 numbers of the displays that you want affected with the command
7655 argument @var{dnums}. It can be a single display number, one of the
7656 numbers shown in the first field of the @samp{info display} display;
7657 or it could be a range of display numbers, as in @code{2-4}.
7659 @code{undisplay} does not repeat if you press @key{RET} after using it.
7660 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7662 @kindex disable display
7663 @item disable display @var{dnums}@dots{}
7664 Disable the display of item numbers @var{dnums}. A disabled display
7665 item is not printed automatically, but is not forgotten. It may be
7666 enabled again later. Specify the numbers of the displays that you
7667 want affected with the command argument @var{dnums}. It can be a
7668 single display number, one of the numbers shown in the first field of
7669 the @samp{info display} display; or it could be a range of display
7670 numbers, as in @code{2-4}.
7672 @kindex enable display
7673 @item enable display @var{dnums}@dots{}
7674 Enable display of item numbers @var{dnums}. It becomes effective once
7675 again in auto display of its expression, until you specify otherwise.
7676 Specify the numbers of the displays that you want affected with the
7677 command argument @var{dnums}. It can be a single display number, one
7678 of the numbers shown in the first field of the @samp{info display}
7679 display; or it could be a range of display numbers, as in @code{2-4}.
7682 Display the current values of the expressions on the list, just as is
7683 done when your program stops.
7685 @kindex info display
7687 Print the list of expressions previously set up to display
7688 automatically, each one with its item number, but without showing the
7689 values. This includes disabled expressions, which are marked as such.
7690 It also includes expressions which would not be displayed right now
7691 because they refer to automatic variables not currently available.
7694 @cindex display disabled out of scope
7695 If a display expression refers to local variables, then it does not make
7696 sense outside the lexical context for which it was set up. Such an
7697 expression is disabled when execution enters a context where one of its
7698 variables is not defined. For example, if you give the command
7699 @code{display last_char} while inside a function with an argument
7700 @code{last_char}, @value{GDBN} displays this argument while your program
7701 continues to stop inside that function. When it stops elsewhere---where
7702 there is no variable @code{last_char}---the display is disabled
7703 automatically. The next time your program stops where @code{last_char}
7704 is meaningful, you can enable the display expression once again.
7706 @node Print Settings
7707 @section Print Settings
7709 @cindex format options
7710 @cindex print settings
7711 @value{GDBN} provides the following ways to control how arrays, structures,
7712 and symbols are printed.
7715 These settings are useful for debugging programs in any language:
7719 @item set print address
7720 @itemx set print address on
7721 @cindex print/don't print memory addresses
7722 @value{GDBN} prints memory addresses showing the location of stack
7723 traces, structure values, pointer values, breakpoints, and so forth,
7724 even when it also displays the contents of those addresses. The default
7725 is @code{on}. For example, this is what a stack frame display looks like with
7726 @code{set print address on}:
7731 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7733 530 if (lquote != def_lquote)
7737 @item set print address off
7738 Do not print addresses when displaying their contents. For example,
7739 this is the same stack frame displayed with @code{set print address off}:
7743 (@value{GDBP}) set print addr off
7745 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7746 530 if (lquote != def_lquote)
7750 You can use @samp{set print address off} to eliminate all machine
7751 dependent displays from the @value{GDBN} interface. For example, with
7752 @code{print address off}, you should get the same text for backtraces on
7753 all machines---whether or not they involve pointer arguments.
7756 @item show print address
7757 Show whether or not addresses are to be printed.
7760 When @value{GDBN} prints a symbolic address, it normally prints the
7761 closest earlier symbol plus an offset. If that symbol does not uniquely
7762 identify the address (for example, it is a name whose scope is a single
7763 source file), you may need to clarify. One way to do this is with
7764 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7765 you can set @value{GDBN} to print the source file and line number when
7766 it prints a symbolic address:
7769 @item set print symbol-filename on
7770 @cindex source file and line of a symbol
7771 @cindex symbol, source file and line
7772 Tell @value{GDBN} to print the source file name and line number of a
7773 symbol in the symbolic form of an address.
7775 @item set print symbol-filename off
7776 Do not print source file name and line number of a symbol. This is the
7779 @item show print symbol-filename
7780 Show whether or not @value{GDBN} will print the source file name and
7781 line number of a symbol in the symbolic form of an address.
7784 Another situation where it is helpful to show symbol filenames and line
7785 numbers is when disassembling code; @value{GDBN} shows you the line
7786 number and source file that corresponds to each instruction.
7788 Also, you may wish to see the symbolic form only if the address being
7789 printed is reasonably close to the closest earlier symbol:
7792 @item set print max-symbolic-offset @var{max-offset}
7793 @cindex maximum value for offset of closest symbol
7794 Tell @value{GDBN} to only display the symbolic form of an address if the
7795 offset between the closest earlier symbol and the address is less than
7796 @var{max-offset}. The default is 0, which tells @value{GDBN}
7797 to always print the symbolic form of an address if any symbol precedes it.
7799 @item show print max-symbolic-offset
7800 Ask how large the maximum offset is that @value{GDBN} prints in a
7804 @cindex wild pointer, interpreting
7805 @cindex pointer, finding referent
7806 If you have a pointer and you are not sure where it points, try
7807 @samp{set print symbol-filename on}. Then you can determine the name
7808 and source file location of the variable where it points, using
7809 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7810 For example, here @value{GDBN} shows that a variable @code{ptt} points
7811 at another variable @code{t}, defined in @file{hi2.c}:
7814 (@value{GDBP}) set print symbol-filename on
7815 (@value{GDBP}) p/a ptt
7816 $4 = 0xe008 <t in hi2.c>
7820 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7821 does not show the symbol name and filename of the referent, even with
7822 the appropriate @code{set print} options turned on.
7825 Other settings control how different kinds of objects are printed:
7828 @item set print array
7829 @itemx set print array on
7830 @cindex pretty print arrays
7831 Pretty print arrays. This format is more convenient to read,
7832 but uses more space. The default is off.
7834 @item set print array off
7835 Return to compressed format for arrays.
7837 @item show print array
7838 Show whether compressed or pretty format is selected for displaying
7841 @cindex print array indexes
7842 @item set print array-indexes
7843 @itemx set print array-indexes on
7844 Print the index of each element when displaying arrays. May be more
7845 convenient to locate a given element in the array or quickly find the
7846 index of a given element in that printed array. The default is off.
7848 @item set print array-indexes off
7849 Stop printing element indexes when displaying arrays.
7851 @item show print array-indexes
7852 Show whether the index of each element is printed when displaying
7855 @item set print elements @var{number-of-elements}
7856 @cindex number of array elements to print
7857 @cindex limit on number of printed array elements
7858 Set a limit on how many elements of an array @value{GDBN} will print.
7859 If @value{GDBN} is printing a large array, it stops printing after it has
7860 printed the number of elements set by the @code{set print elements} command.
7861 This limit also applies to the display of strings.
7862 When @value{GDBN} starts, this limit is set to 200.
7863 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7865 @item show print elements
7866 Display the number of elements of a large array that @value{GDBN} will print.
7867 If the number is 0, then the printing is unlimited.
7869 @item set print frame-arguments @var{value}
7870 @kindex set print frame-arguments
7871 @cindex printing frame argument values
7872 @cindex print all frame argument values
7873 @cindex print frame argument values for scalars only
7874 @cindex do not print frame argument values
7875 This command allows to control how the values of arguments are printed
7876 when the debugger prints a frame (@pxref{Frames}). The possible
7881 The values of all arguments are printed.
7884 Print the value of an argument only if it is a scalar. The value of more
7885 complex arguments such as arrays, structures, unions, etc, is replaced
7886 by @code{@dots{}}. This is the default. Here is an example where
7887 only scalar arguments are shown:
7890 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7895 None of the argument values are printed. Instead, the value of each argument
7896 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7899 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7904 By default, only scalar arguments are printed. This command can be used
7905 to configure the debugger to print the value of all arguments, regardless
7906 of their type. However, it is often advantageous to not print the value
7907 of more complex parameters. For instance, it reduces the amount of
7908 information printed in each frame, making the backtrace more readable.
7909 Also, it improves performance when displaying Ada frames, because
7910 the computation of large arguments can sometimes be CPU-intensive,
7911 especially in large applications. Setting @code{print frame-arguments}
7912 to @code{scalars} (the default) or @code{none} avoids this computation,
7913 thus speeding up the display of each Ada frame.
7915 @item show print frame-arguments
7916 Show how the value of arguments should be displayed when printing a frame.
7918 @item set print repeats
7919 @cindex repeated array elements
7920 Set the threshold for suppressing display of repeated array
7921 elements. When the number of consecutive identical elements of an
7922 array exceeds the threshold, @value{GDBN} prints the string
7923 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7924 identical repetitions, instead of displaying the identical elements
7925 themselves. Setting the threshold to zero will cause all elements to
7926 be individually printed. The default threshold is 10.
7928 @item show print repeats
7929 Display the current threshold for printing repeated identical
7932 @item set print null-stop
7933 @cindex @sc{null} elements in arrays
7934 Cause @value{GDBN} to stop printing the characters of an array when the first
7935 @sc{null} is encountered. This is useful when large arrays actually
7936 contain only short strings.
7939 @item show print null-stop
7940 Show whether @value{GDBN} stops printing an array on the first
7941 @sc{null} character.
7943 @item set print pretty on
7944 @cindex print structures in indented form
7945 @cindex indentation in structure display
7946 Cause @value{GDBN} to print structures in an indented format with one member
7947 per line, like this:
7962 @item set print pretty off
7963 Cause @value{GDBN} to print structures in a compact format, like this:
7967 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7968 meat = 0x54 "Pork"@}
7973 This is the default format.
7975 @item show print pretty
7976 Show which format @value{GDBN} is using to print structures.
7978 @item set print sevenbit-strings on
7979 @cindex eight-bit characters in strings
7980 @cindex octal escapes in strings
7981 Print using only seven-bit characters; if this option is set,
7982 @value{GDBN} displays any eight-bit characters (in strings or
7983 character values) using the notation @code{\}@var{nnn}. This setting is
7984 best if you are working in English (@sc{ascii}) and you use the
7985 high-order bit of characters as a marker or ``meta'' bit.
7987 @item set print sevenbit-strings off
7988 Print full eight-bit characters. This allows the use of more
7989 international character sets, and is the default.
7991 @item show print sevenbit-strings
7992 Show whether or not @value{GDBN} is printing only seven-bit characters.
7994 @item set print union on
7995 @cindex unions in structures, printing
7996 Tell @value{GDBN} to print unions which are contained in structures
7997 and other unions. This is the default setting.
7999 @item set print union off
8000 Tell @value{GDBN} not to print unions which are contained in
8001 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8004 @item show print union
8005 Ask @value{GDBN} whether or not it will print unions which are contained in
8006 structures and other unions.
8008 For example, given the declarations
8011 typedef enum @{Tree, Bug@} Species;
8012 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8013 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8024 struct thing foo = @{Tree, @{Acorn@}@};
8028 with @code{set print union on} in effect @samp{p foo} would print
8031 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8035 and with @code{set print union off} in effect it would print
8038 $1 = @{it = Tree, form = @{...@}@}
8042 @code{set print union} affects programs written in C-like languages
8048 These settings are of interest when debugging C@t{++} programs:
8051 @cindex demangling C@t{++} names
8052 @item set print demangle
8053 @itemx set print demangle on
8054 Print C@t{++} names in their source form rather than in the encoded
8055 (``mangled'') form passed to the assembler and linker for type-safe
8056 linkage. The default is on.
8058 @item show print demangle
8059 Show whether C@t{++} names are printed in mangled or demangled form.
8061 @item set print asm-demangle
8062 @itemx set print asm-demangle on
8063 Print C@t{++} names in their source form rather than their mangled form, even
8064 in assembler code printouts such as instruction disassemblies.
8067 @item show print asm-demangle
8068 Show whether C@t{++} names in assembly listings are printed in mangled
8071 @cindex C@t{++} symbol decoding style
8072 @cindex symbol decoding style, C@t{++}
8073 @kindex set demangle-style
8074 @item set demangle-style @var{style}
8075 Choose among several encoding schemes used by different compilers to
8076 represent C@t{++} names. The choices for @var{style} are currently:
8080 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8083 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8084 This is the default.
8087 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8090 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8093 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8094 @strong{Warning:} this setting alone is not sufficient to allow
8095 debugging @code{cfront}-generated executables. @value{GDBN} would
8096 require further enhancement to permit that.
8099 If you omit @var{style}, you will see a list of possible formats.
8101 @item show demangle-style
8102 Display the encoding style currently in use for decoding C@t{++} symbols.
8104 @item set print object
8105 @itemx set print object on
8106 @cindex derived type of an object, printing
8107 @cindex display derived types
8108 When displaying a pointer to an object, identify the @emph{actual}
8109 (derived) type of the object rather than the @emph{declared} type, using
8110 the virtual function table.
8112 @item set print object off
8113 Display only the declared type of objects, without reference to the
8114 virtual function table. This is the default setting.
8116 @item show print object
8117 Show whether actual, or declared, object types are displayed.
8119 @item set print static-members
8120 @itemx set print static-members on
8121 @cindex static members of C@t{++} objects
8122 Print static members when displaying a C@t{++} object. The default is on.
8124 @item set print static-members off
8125 Do not print static members when displaying a C@t{++} object.
8127 @item show print static-members
8128 Show whether C@t{++} static members are printed or not.
8130 @item set print pascal_static-members
8131 @itemx set print pascal_static-members on
8132 @cindex static members of Pascal objects
8133 @cindex Pascal objects, static members display
8134 Print static members when displaying a Pascal object. The default is on.
8136 @item set print pascal_static-members off
8137 Do not print static members when displaying a Pascal object.
8139 @item show print pascal_static-members
8140 Show whether Pascal static members are printed or not.
8142 @c These don't work with HP ANSI C++ yet.
8143 @item set print vtbl
8144 @itemx set print vtbl on
8145 @cindex pretty print C@t{++} virtual function tables
8146 @cindex virtual functions (C@t{++}) display
8147 @cindex VTBL display
8148 Pretty print C@t{++} virtual function tables. The default is off.
8149 (The @code{vtbl} commands do not work on programs compiled with the HP
8150 ANSI C@t{++} compiler (@code{aCC}).)
8152 @item set print vtbl off
8153 Do not pretty print C@t{++} virtual function tables.
8155 @item show print vtbl
8156 Show whether C@t{++} virtual function tables are pretty printed, or not.
8159 @node Pretty Printing
8160 @section Pretty Printing
8162 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8163 Python code. It greatly simplifies the display of complex objects. This
8164 mechanism works for both MI and the CLI.
8167 * Pretty-Printer Introduction:: Introduction to pretty-printers
8168 * Pretty-Printer Example:: An example pretty-printer
8169 * Pretty-Printer Commands:: Pretty-printer commands
8172 @node Pretty-Printer Introduction
8173 @subsection Pretty-Printer Introduction
8175 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8176 registered for the value. If there is then @value{GDBN} invokes the
8177 pretty-printer to print the value. Otherwise the value is printed normally.
8179 Pretty-printers are normally named. This makes them easy to manage.
8180 The @samp{info pretty-printer} command will list all the installed
8181 pretty-printers with their names.
8182 If a pretty-printer can handle multiple data types, then its
8183 @dfn{subprinters} are the printers for the individual data types.
8184 Each such subprinter has its own name.
8185 The format of the name is @var{printer-name};@var{subprinter-name}.
8187 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8188 Typically they are automatically loaded and registered when the corresponding
8189 debug information is loaded, thus making them available without having to
8190 do anything special.
8192 There are three places where a pretty-printer can be registered.
8196 Pretty-printers registered globally are available when debugging
8200 Pretty-printers registered with a program space are available only
8201 when debugging that program.
8202 @xref{Progspaces In Python}, for more details on program spaces in Python.
8205 Pretty-printers registered with an objfile are loaded and unloaded
8206 with the corresponding objfile (e.g., shared library).
8207 @xref{Objfiles In Python}, for more details on objfiles in Python.
8210 @xref{Selecting Pretty-Printers}, for further information on how
8211 pretty-printers are selected,
8213 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8216 @node Pretty-Printer Example
8217 @subsection Pretty-Printer Example
8219 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8222 (@value{GDBP}) print s
8224 static npos = 4294967295,
8226 <std::allocator<char>> = @{
8227 <__gnu_cxx::new_allocator<char>> = @{
8228 <No data fields>@}, <No data fields>
8230 members of std::basic_string<char, std::char_traits<char>,
8231 std::allocator<char> >::_Alloc_hider:
8232 _M_p = 0x804a014 "abcd"
8237 With a pretty-printer for @code{std::string} only the contents are printed:
8240 (@value{GDBP}) print s
8244 @node Pretty-Printer Commands
8245 @subsection Pretty-Printer Commands
8246 @cindex pretty-printer commands
8249 @kindex info pretty-printer
8250 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8251 Print the list of installed pretty-printers.
8252 This includes disabled pretty-printers, which are marked as such.
8254 @var{object-regexp} is a regular expression matching the objects
8255 whose pretty-printers to list.
8256 Objects can be @code{global}, the program space's file
8257 (@pxref{Progspaces In Python}),
8258 and the object files within that program space (@pxref{Objfiles In Python}).
8259 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8260 looks up a printer from these three objects.
8262 @var{name-regexp} is a regular expression matching the name of the printers
8265 @kindex disable pretty-printer
8266 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8267 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8268 A disabled pretty-printer is not forgotten, it may be enabled again later.
8270 @kindex enable pretty-printer
8271 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8272 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8277 Suppose we have three pretty-printers installed: one from library1.so
8278 named @code{foo} that prints objects of type @code{foo}, and
8279 another from library2.so named @code{bar} that prints two types of objects,
8280 @code{bar1} and @code{bar2}.
8283 (gdb) info pretty-printer
8290 (gdb) info pretty-printer library2
8295 (gdb) disable pretty-printer library1
8297 2 of 3 printers enabled
8298 (gdb) info pretty-printer
8305 (gdb) disable pretty-printer library2 bar:bar1
8307 1 of 3 printers enabled
8308 (gdb) info pretty-printer library2
8315 (gdb) disable pretty-printer library2 bar
8317 0 of 3 printers enabled
8318 (gdb) info pretty-printer library2
8327 Note that for @code{bar} the entire printer can be disabled,
8328 as can each individual subprinter.
8331 @section Value History
8333 @cindex value history
8334 @cindex history of values printed by @value{GDBN}
8335 Values printed by the @code{print} command are saved in the @value{GDBN}
8336 @dfn{value history}. This allows you to refer to them in other expressions.
8337 Values are kept until the symbol table is re-read or discarded
8338 (for example with the @code{file} or @code{symbol-file} commands).
8339 When the symbol table changes, the value history is discarded,
8340 since the values may contain pointers back to the types defined in the
8345 @cindex history number
8346 The values printed are given @dfn{history numbers} by which you can
8347 refer to them. These are successive integers starting with one.
8348 @code{print} shows you the history number assigned to a value by
8349 printing @samp{$@var{num} = } before the value; here @var{num} is the
8352 To refer to any previous value, use @samp{$} followed by the value's
8353 history number. The way @code{print} labels its output is designed to
8354 remind you of this. Just @code{$} refers to the most recent value in
8355 the history, and @code{$$} refers to the value before that.
8356 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8357 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8358 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8360 For example, suppose you have just printed a pointer to a structure and
8361 want to see the contents of the structure. It suffices to type
8367 If you have a chain of structures where the component @code{next} points
8368 to the next one, you can print the contents of the next one with this:
8375 You can print successive links in the chain by repeating this
8376 command---which you can do by just typing @key{RET}.
8378 Note that the history records values, not expressions. If the value of
8379 @code{x} is 4 and you type these commands:
8387 then the value recorded in the value history by the @code{print} command
8388 remains 4 even though the value of @code{x} has changed.
8393 Print the last ten values in the value history, with their item numbers.
8394 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8395 values} does not change the history.
8397 @item show values @var{n}
8398 Print ten history values centered on history item number @var{n}.
8401 Print ten history values just after the values last printed. If no more
8402 values are available, @code{show values +} produces no display.
8405 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8406 same effect as @samp{show values +}.
8408 @node Convenience Vars
8409 @section Convenience Variables
8411 @cindex convenience variables
8412 @cindex user-defined variables
8413 @value{GDBN} provides @dfn{convenience variables} that you can use within
8414 @value{GDBN} to hold on to a value and refer to it later. These variables
8415 exist entirely within @value{GDBN}; they are not part of your program, and
8416 setting a convenience variable has no direct effect on further execution
8417 of your program. That is why you can use them freely.
8419 Convenience variables are prefixed with @samp{$}. Any name preceded by
8420 @samp{$} can be used for a convenience variable, unless it is one of
8421 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8422 (Value history references, in contrast, are @emph{numbers} preceded
8423 by @samp{$}. @xref{Value History, ,Value History}.)
8425 You can save a value in a convenience variable with an assignment
8426 expression, just as you would set a variable in your program.
8430 set $foo = *object_ptr
8434 would save in @code{$foo} the value contained in the object pointed to by
8437 Using a convenience variable for the first time creates it, but its
8438 value is @code{void} until you assign a new value. You can alter the
8439 value with another assignment at any time.
8441 Convenience variables have no fixed types. You can assign a convenience
8442 variable any type of value, including structures and arrays, even if
8443 that variable already has a value of a different type. The convenience
8444 variable, when used as an expression, has the type of its current value.
8447 @kindex show convenience
8448 @cindex show all user variables
8449 @item show convenience
8450 Print a list of convenience variables used so far, and their values.
8451 Abbreviated @code{show conv}.
8453 @kindex init-if-undefined
8454 @cindex convenience variables, initializing
8455 @item init-if-undefined $@var{variable} = @var{expression}
8456 Set a convenience variable if it has not already been set. This is useful
8457 for user-defined commands that keep some state. It is similar, in concept,
8458 to using local static variables with initializers in C (except that
8459 convenience variables are global). It can also be used to allow users to
8460 override default values used in a command script.
8462 If the variable is already defined then the expression is not evaluated so
8463 any side-effects do not occur.
8466 One of the ways to use a convenience variable is as a counter to be
8467 incremented or a pointer to be advanced. For example, to print
8468 a field from successive elements of an array of structures:
8472 print bar[$i++]->contents
8476 Repeat that command by typing @key{RET}.
8478 Some convenience variables are created automatically by @value{GDBN} and given
8479 values likely to be useful.
8482 @vindex $_@r{, convenience variable}
8484 The variable @code{$_} is automatically set by the @code{x} command to
8485 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8486 commands which provide a default address for @code{x} to examine also
8487 set @code{$_} to that address; these commands include @code{info line}
8488 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8489 except when set by the @code{x} command, in which case it is a pointer
8490 to the type of @code{$__}.
8492 @vindex $__@r{, convenience variable}
8494 The variable @code{$__} is automatically set by the @code{x} command
8495 to the value found in the last address examined. Its type is chosen
8496 to match the format in which the data was printed.
8499 @vindex $_exitcode@r{, convenience variable}
8500 The variable @code{$_exitcode} is automatically set to the exit code when
8501 the program being debugged terminates.
8504 @vindex $_sdata@r{, inspect, convenience variable}
8505 The variable @code{$_sdata} contains extra collected static tracepoint
8506 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8507 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8508 if extra static tracepoint data has not been collected.
8511 @vindex $_siginfo@r{, convenience variable}
8512 The variable @code{$_siginfo} contains extra signal information
8513 (@pxref{extra signal information}). Note that @code{$_siginfo}
8514 could be empty, if the application has not yet received any signals.
8515 For example, it will be empty before you execute the @code{run} command.
8518 @vindex $_tlb@r{, convenience variable}
8519 The variable @code{$_tlb} is automatically set when debugging
8520 applications running on MS-Windows in native mode or connected to
8521 gdbserver that supports the @code{qGetTIBAddr} request.
8522 @xref{General Query Packets}.
8523 This variable contains the address of the thread information block.
8527 On HP-UX systems, if you refer to a function or variable name that
8528 begins with a dollar sign, @value{GDBN} searches for a user or system
8529 name first, before it searches for a convenience variable.
8531 @cindex convenience functions
8532 @value{GDBN} also supplies some @dfn{convenience functions}. These
8533 have a syntax similar to convenience variables. A convenience
8534 function can be used in an expression just like an ordinary function;
8535 however, a convenience function is implemented internally to
8540 @kindex help function
8541 @cindex show all convenience functions
8542 Print a list of all convenience functions.
8549 You can refer to machine register contents, in expressions, as variables
8550 with names starting with @samp{$}. The names of registers are different
8551 for each machine; use @code{info registers} to see the names used on
8555 @kindex info registers
8556 @item info registers
8557 Print the names and values of all registers except floating-point
8558 and vector registers (in the selected stack frame).
8560 @kindex info all-registers
8561 @cindex floating point registers
8562 @item info all-registers
8563 Print the names and values of all registers, including floating-point
8564 and vector registers (in the selected stack frame).
8566 @item info registers @var{regname} @dots{}
8567 Print the @dfn{relativized} value of each specified register @var{regname}.
8568 As discussed in detail below, register values are normally relative to
8569 the selected stack frame. @var{regname} may be any register name valid on
8570 the machine you are using, with or without the initial @samp{$}.
8573 @cindex stack pointer register
8574 @cindex program counter register
8575 @cindex process status register
8576 @cindex frame pointer register
8577 @cindex standard registers
8578 @value{GDBN} has four ``standard'' register names that are available (in
8579 expressions) on most machines---whenever they do not conflict with an
8580 architecture's canonical mnemonics for registers. The register names
8581 @code{$pc} and @code{$sp} are used for the program counter register and
8582 the stack pointer. @code{$fp} is used for a register that contains a
8583 pointer to the current stack frame, and @code{$ps} is used for a
8584 register that contains the processor status. For example,
8585 you could print the program counter in hex with
8592 or print the instruction to be executed next with
8599 or add four to the stack pointer@footnote{This is a way of removing
8600 one word from the stack, on machines where stacks grow downward in
8601 memory (most machines, nowadays). This assumes that the innermost
8602 stack frame is selected; setting @code{$sp} is not allowed when other
8603 stack frames are selected. To pop entire frames off the stack,
8604 regardless of machine architecture, use @code{return};
8605 see @ref{Returning, ,Returning from a Function}.} with
8611 Whenever possible, these four standard register names are available on
8612 your machine even though the machine has different canonical mnemonics,
8613 so long as there is no conflict. The @code{info registers} command
8614 shows the canonical names. For example, on the SPARC, @code{info
8615 registers} displays the processor status register as @code{$psr} but you
8616 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8617 is an alias for the @sc{eflags} register.
8619 @value{GDBN} always considers the contents of an ordinary register as an
8620 integer when the register is examined in this way. Some machines have
8621 special registers which can hold nothing but floating point; these
8622 registers are considered to have floating point values. There is no way
8623 to refer to the contents of an ordinary register as floating point value
8624 (although you can @emph{print} it as a floating point value with
8625 @samp{print/f $@var{regname}}).
8627 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8628 means that the data format in which the register contents are saved by
8629 the operating system is not the same one that your program normally
8630 sees. For example, the registers of the 68881 floating point
8631 coprocessor are always saved in ``extended'' (raw) format, but all C
8632 programs expect to work with ``double'' (virtual) format. In such
8633 cases, @value{GDBN} normally works with the virtual format only (the format
8634 that makes sense for your program), but the @code{info registers} command
8635 prints the data in both formats.
8637 @cindex SSE registers (x86)
8638 @cindex MMX registers (x86)
8639 Some machines have special registers whose contents can be interpreted
8640 in several different ways. For example, modern x86-based machines
8641 have SSE and MMX registers that can hold several values packed
8642 together in several different formats. @value{GDBN} refers to such
8643 registers in @code{struct} notation:
8646 (@value{GDBP}) print $xmm1
8648 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8649 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8650 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8651 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8652 v4_int32 = @{0, 20657912, 11, 13@},
8653 v2_int64 = @{88725056443645952, 55834574859@},
8654 uint128 = 0x0000000d0000000b013b36f800000000
8659 To set values of such registers, you need to tell @value{GDBN} which
8660 view of the register you wish to change, as if you were assigning
8661 value to a @code{struct} member:
8664 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8667 Normally, register values are relative to the selected stack frame
8668 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8669 value that the register would contain if all stack frames farther in
8670 were exited and their saved registers restored. In order to see the
8671 true contents of hardware registers, you must select the innermost
8672 frame (with @samp{frame 0}).
8674 However, @value{GDBN} must deduce where registers are saved, from the machine
8675 code generated by your compiler. If some registers are not saved, or if
8676 @value{GDBN} is unable to locate the saved registers, the selected stack
8677 frame makes no difference.
8679 @node Floating Point Hardware
8680 @section Floating Point Hardware
8681 @cindex floating point
8683 Depending on the configuration, @value{GDBN} may be able to give
8684 you more information about the status of the floating point hardware.
8689 Display hardware-dependent information about the floating
8690 point unit. The exact contents and layout vary depending on the
8691 floating point chip. Currently, @samp{info float} is supported on
8692 the ARM and x86 machines.
8696 @section Vector Unit
8699 Depending on the configuration, @value{GDBN} may be able to give you
8700 more information about the status of the vector unit.
8705 Display information about the vector unit. The exact contents and
8706 layout vary depending on the hardware.
8709 @node OS Information
8710 @section Operating System Auxiliary Information
8711 @cindex OS information
8713 @value{GDBN} provides interfaces to useful OS facilities that can help
8714 you debug your program.
8716 @cindex @code{ptrace} system call
8717 @cindex @code{struct user} contents
8718 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8719 machines), it interfaces with the inferior via the @code{ptrace}
8720 system call. The operating system creates a special sata structure,
8721 called @code{struct user}, for this interface. You can use the
8722 command @code{info udot} to display the contents of this data
8728 Display the contents of the @code{struct user} maintained by the OS
8729 kernel for the program being debugged. @value{GDBN} displays the
8730 contents of @code{struct user} as a list of hex numbers, similar to
8731 the @code{examine} command.
8734 @cindex auxiliary vector
8735 @cindex vector, auxiliary
8736 Some operating systems supply an @dfn{auxiliary vector} to programs at
8737 startup. This is akin to the arguments and environment that you
8738 specify for a program, but contains a system-dependent variety of
8739 binary values that tell system libraries important details about the
8740 hardware, operating system, and process. Each value's purpose is
8741 identified by an integer tag; the meanings are well-known but system-specific.
8742 Depending on the configuration and operating system facilities,
8743 @value{GDBN} may be able to show you this information. For remote
8744 targets, this functionality may further depend on the remote stub's
8745 support of the @samp{qXfer:auxv:read} packet, see
8746 @ref{qXfer auxiliary vector read}.
8751 Display the auxiliary vector of the inferior, which can be either a
8752 live process or a core dump file. @value{GDBN} prints each tag value
8753 numerically, and also shows names and text descriptions for recognized
8754 tags. Some values in the vector are numbers, some bit masks, and some
8755 pointers to strings or other data. @value{GDBN} displays each value in the
8756 most appropriate form for a recognized tag, and in hexadecimal for
8757 an unrecognized tag.
8760 On some targets, @value{GDBN} can access operating-system-specific information
8761 and display it to user, without interpretation. For remote targets,
8762 this functionality depends on the remote stub's support of the
8763 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8768 List the types of OS information available for the target. If the
8769 target does not return a list of possible types, this command will
8772 @kindex info os processes
8773 @item info os processes
8774 Display the list of processes on the target. For each process,
8775 @value{GDBN} prints the process identifier, the name of the user, and
8776 the command corresponding to the process.
8779 @node Memory Region Attributes
8780 @section Memory Region Attributes
8781 @cindex memory region attributes
8783 @dfn{Memory region attributes} allow you to describe special handling
8784 required by regions of your target's memory. @value{GDBN} uses
8785 attributes to determine whether to allow certain types of memory
8786 accesses; whether to use specific width accesses; and whether to cache
8787 target memory. By default the description of memory regions is
8788 fetched from the target (if the current target supports this), but the
8789 user can override the fetched regions.
8791 Defined memory regions can be individually enabled and disabled. When a
8792 memory region is disabled, @value{GDBN} uses the default attributes when
8793 accessing memory in that region. Similarly, if no memory regions have
8794 been defined, @value{GDBN} uses the default attributes when accessing
8797 When a memory region is defined, it is given a number to identify it;
8798 to enable, disable, or remove a memory region, you specify that number.
8802 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8803 Define a memory region bounded by @var{lower} and @var{upper} with
8804 attributes @var{attributes}@dots{}, and add it to the list of regions
8805 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8806 case: it is treated as the target's maximum memory address.
8807 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8810 Discard any user changes to the memory regions and use target-supplied
8811 regions, if available, or no regions if the target does not support.
8814 @item delete mem @var{nums}@dots{}
8815 Remove memory regions @var{nums}@dots{} from the list of regions
8816 monitored by @value{GDBN}.
8819 @item disable mem @var{nums}@dots{}
8820 Disable monitoring of memory regions @var{nums}@dots{}.
8821 A disabled memory region is not forgotten.
8822 It may be enabled again later.
8825 @item enable mem @var{nums}@dots{}
8826 Enable monitoring of memory regions @var{nums}@dots{}.
8830 Print a table of all defined memory regions, with the following columns
8834 @item Memory Region Number
8835 @item Enabled or Disabled.
8836 Enabled memory regions are marked with @samp{y}.
8837 Disabled memory regions are marked with @samp{n}.
8840 The address defining the inclusive lower bound of the memory region.
8843 The address defining the exclusive upper bound of the memory region.
8846 The list of attributes set for this memory region.
8851 @subsection Attributes
8853 @subsubsection Memory Access Mode
8854 The access mode attributes set whether @value{GDBN} may make read or
8855 write accesses to a memory region.
8857 While these attributes prevent @value{GDBN} from performing invalid
8858 memory accesses, they do nothing to prevent the target system, I/O DMA,
8859 etc.@: from accessing memory.
8863 Memory is read only.
8865 Memory is write only.
8867 Memory is read/write. This is the default.
8870 @subsubsection Memory Access Size
8871 The access size attribute tells @value{GDBN} to use specific sized
8872 accesses in the memory region. Often memory mapped device registers
8873 require specific sized accesses. If no access size attribute is
8874 specified, @value{GDBN} may use accesses of any size.
8878 Use 8 bit memory accesses.
8880 Use 16 bit memory accesses.
8882 Use 32 bit memory accesses.
8884 Use 64 bit memory accesses.
8887 @c @subsubsection Hardware/Software Breakpoints
8888 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8889 @c will use hardware or software breakpoints for the internal breakpoints
8890 @c used by the step, next, finish, until, etc. commands.
8894 @c Always use hardware breakpoints
8895 @c @item swbreak (default)
8898 @subsubsection Data Cache
8899 The data cache attributes set whether @value{GDBN} will cache target
8900 memory. While this generally improves performance by reducing debug
8901 protocol overhead, it can lead to incorrect results because @value{GDBN}
8902 does not know about volatile variables or memory mapped device
8907 Enable @value{GDBN} to cache target memory.
8909 Disable @value{GDBN} from caching target memory. This is the default.
8912 @subsection Memory Access Checking
8913 @value{GDBN} can be instructed to refuse accesses to memory that is
8914 not explicitly described. This can be useful if accessing such
8915 regions has undesired effects for a specific target, or to provide
8916 better error checking. The following commands control this behaviour.
8919 @kindex set mem inaccessible-by-default
8920 @item set mem inaccessible-by-default [on|off]
8921 If @code{on} is specified, make @value{GDBN} treat memory not
8922 explicitly described by the memory ranges as non-existent and refuse accesses
8923 to such memory. The checks are only performed if there's at least one
8924 memory range defined. If @code{off} is specified, make @value{GDBN}
8925 treat the memory not explicitly described by the memory ranges as RAM.
8926 The default value is @code{on}.
8927 @kindex show mem inaccessible-by-default
8928 @item show mem inaccessible-by-default
8929 Show the current handling of accesses to unknown memory.
8933 @c @subsubsection Memory Write Verification
8934 @c The memory write verification attributes set whether @value{GDBN}
8935 @c will re-reads data after each write to verify the write was successful.
8939 @c @item noverify (default)
8942 @node Dump/Restore Files
8943 @section Copy Between Memory and a File
8944 @cindex dump/restore files
8945 @cindex append data to a file
8946 @cindex dump data to a file
8947 @cindex restore data from a file
8949 You can use the commands @code{dump}, @code{append}, and
8950 @code{restore} to copy data between target memory and a file. The
8951 @code{dump} and @code{append} commands write data to a file, and the
8952 @code{restore} command reads data from a file back into the inferior's
8953 memory. Files may be in binary, Motorola S-record, Intel hex, or
8954 Tektronix Hex format; however, @value{GDBN} can only append to binary
8960 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8961 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8962 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8963 or the value of @var{expr}, to @var{filename} in the given format.
8965 The @var{format} parameter may be any one of:
8972 Motorola S-record format.
8974 Tektronix Hex format.
8977 @value{GDBN} uses the same definitions of these formats as the
8978 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8979 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8983 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8984 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8985 Append the contents of memory from @var{start_addr} to @var{end_addr},
8986 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8987 (@value{GDBN} can only append data to files in raw binary form.)
8990 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8991 Restore the contents of file @var{filename} into memory. The
8992 @code{restore} command can automatically recognize any known @sc{bfd}
8993 file format, except for raw binary. To restore a raw binary file you
8994 must specify the optional keyword @code{binary} after the filename.
8996 If @var{bias} is non-zero, its value will be added to the addresses
8997 contained in the file. Binary files always start at address zero, so
8998 they will be restored at address @var{bias}. Other bfd files have
8999 a built-in location; they will be restored at offset @var{bias}
9002 If @var{start} and/or @var{end} are non-zero, then only data between
9003 file offset @var{start} and file offset @var{end} will be restored.
9004 These offsets are relative to the addresses in the file, before
9005 the @var{bias} argument is applied.
9009 @node Core File Generation
9010 @section How to Produce a Core File from Your Program
9011 @cindex dump core from inferior
9013 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9014 image of a running process and its process status (register values
9015 etc.). Its primary use is post-mortem debugging of a program that
9016 crashed while it ran outside a debugger. A program that crashes
9017 automatically produces a core file, unless this feature is disabled by
9018 the user. @xref{Files}, for information on invoking @value{GDBN} in
9019 the post-mortem debugging mode.
9021 Occasionally, you may wish to produce a core file of the program you
9022 are debugging in order to preserve a snapshot of its state.
9023 @value{GDBN} has a special command for that.
9027 @kindex generate-core-file
9028 @item generate-core-file [@var{file}]
9029 @itemx gcore [@var{file}]
9030 Produce a core dump of the inferior process. The optional argument
9031 @var{file} specifies the file name where to put the core dump. If not
9032 specified, the file name defaults to @file{core.@var{pid}}, where
9033 @var{pid} is the inferior process ID.
9035 Note that this command is implemented only for some systems (as of
9036 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9039 @node Character Sets
9040 @section Character Sets
9041 @cindex character sets
9043 @cindex translating between character sets
9044 @cindex host character set
9045 @cindex target character set
9047 If the program you are debugging uses a different character set to
9048 represent characters and strings than the one @value{GDBN} uses itself,
9049 @value{GDBN} can automatically translate between the character sets for
9050 you. The character set @value{GDBN} uses we call the @dfn{host
9051 character set}; the one the inferior program uses we call the
9052 @dfn{target character set}.
9054 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9055 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9056 remote protocol (@pxref{Remote Debugging}) to debug a program
9057 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9058 then the host character set is Latin-1, and the target character set is
9059 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9060 target-charset EBCDIC-US}, then @value{GDBN} translates between
9061 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9062 character and string literals in expressions.
9064 @value{GDBN} has no way to automatically recognize which character set
9065 the inferior program uses; you must tell it, using the @code{set
9066 target-charset} command, described below.
9068 Here are the commands for controlling @value{GDBN}'s character set
9072 @item set target-charset @var{charset}
9073 @kindex set target-charset
9074 Set the current target character set to @var{charset}. To display the
9075 list of supported target character sets, type
9076 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9078 @item set host-charset @var{charset}
9079 @kindex set host-charset
9080 Set the current host character set to @var{charset}.
9082 By default, @value{GDBN} uses a host character set appropriate to the
9083 system it is running on; you can override that default using the
9084 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9085 automatically determine the appropriate host character set. In this
9086 case, @value{GDBN} uses @samp{UTF-8}.
9088 @value{GDBN} can only use certain character sets as its host character
9089 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9090 @value{GDBN} will list the host character sets it supports.
9092 @item set charset @var{charset}
9094 Set the current host and target character sets to @var{charset}. As
9095 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9096 @value{GDBN} will list the names of the character sets that can be used
9097 for both host and target.
9100 @kindex show charset
9101 Show the names of the current host and target character sets.
9103 @item show host-charset
9104 @kindex show host-charset
9105 Show the name of the current host character set.
9107 @item show target-charset
9108 @kindex show target-charset
9109 Show the name of the current target character set.
9111 @item set target-wide-charset @var{charset}
9112 @kindex set target-wide-charset
9113 Set the current target's wide character set to @var{charset}. This is
9114 the character set used by the target's @code{wchar_t} type. To
9115 display the list of supported wide character sets, type
9116 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9118 @item show target-wide-charset
9119 @kindex show target-wide-charset
9120 Show the name of the current target's wide character set.
9123 Here is an example of @value{GDBN}'s character set support in action.
9124 Assume that the following source code has been placed in the file
9125 @file{charset-test.c}:
9131 = @{72, 101, 108, 108, 111, 44, 32, 119,
9132 111, 114, 108, 100, 33, 10, 0@};
9133 char ibm1047_hello[]
9134 = @{200, 133, 147, 147, 150, 107, 64, 166,
9135 150, 153, 147, 132, 90, 37, 0@};
9139 printf ("Hello, world!\n");
9143 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9144 containing the string @samp{Hello, world!} followed by a newline,
9145 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9147 We compile the program, and invoke the debugger on it:
9150 $ gcc -g charset-test.c -o charset-test
9151 $ gdb -nw charset-test
9152 GNU gdb 2001-12-19-cvs
9153 Copyright 2001 Free Software Foundation, Inc.
9158 We can use the @code{show charset} command to see what character sets
9159 @value{GDBN} is currently using to interpret and display characters and
9163 (@value{GDBP}) show charset
9164 The current host and target character set is `ISO-8859-1'.
9168 For the sake of printing this manual, let's use @sc{ascii} as our
9169 initial character set:
9171 (@value{GDBP}) set charset ASCII
9172 (@value{GDBP}) show charset
9173 The current host and target character set is `ASCII'.
9177 Let's assume that @sc{ascii} is indeed the correct character set for our
9178 host system --- in other words, let's assume that if @value{GDBN} prints
9179 characters using the @sc{ascii} character set, our terminal will display
9180 them properly. Since our current target character set is also
9181 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9184 (@value{GDBP}) print ascii_hello
9185 $1 = 0x401698 "Hello, world!\n"
9186 (@value{GDBP}) print ascii_hello[0]
9191 @value{GDBN} uses the target character set for character and string
9192 literals you use in expressions:
9195 (@value{GDBP}) print '+'
9200 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9203 @value{GDBN} relies on the user to tell it which character set the
9204 target program uses. If we print @code{ibm1047_hello} while our target
9205 character set is still @sc{ascii}, we get jibberish:
9208 (@value{GDBP}) print ibm1047_hello
9209 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9210 (@value{GDBP}) print ibm1047_hello[0]
9215 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9216 @value{GDBN} tells us the character sets it supports:
9219 (@value{GDBP}) set target-charset
9220 ASCII EBCDIC-US IBM1047 ISO-8859-1
9221 (@value{GDBP}) set target-charset
9224 We can select @sc{ibm1047} as our target character set, and examine the
9225 program's strings again. Now the @sc{ascii} string is wrong, but
9226 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9227 target character set, @sc{ibm1047}, to the host character set,
9228 @sc{ascii}, and they display correctly:
9231 (@value{GDBP}) set target-charset IBM1047
9232 (@value{GDBP}) show charset
9233 The current host character set is `ASCII'.
9234 The current target character set is `IBM1047'.
9235 (@value{GDBP}) print ascii_hello
9236 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9237 (@value{GDBP}) print ascii_hello[0]
9239 (@value{GDBP}) print ibm1047_hello
9240 $8 = 0x4016a8 "Hello, world!\n"
9241 (@value{GDBP}) print ibm1047_hello[0]
9246 As above, @value{GDBN} uses the target character set for character and
9247 string literals you use in expressions:
9250 (@value{GDBP}) print '+'
9255 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9258 @node Caching Remote Data
9259 @section Caching Data of Remote Targets
9260 @cindex caching data of remote targets
9262 @value{GDBN} caches data exchanged between the debugger and a
9263 remote target (@pxref{Remote Debugging}). Such caching generally improves
9264 performance, because it reduces the overhead of the remote protocol by
9265 bundling memory reads and writes into large chunks. Unfortunately, simply
9266 caching everything would lead to incorrect results, since @value{GDBN}
9267 does not necessarily know anything about volatile values, memory-mapped I/O
9268 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9269 memory can be changed @emph{while} a gdb command is executing.
9270 Therefore, by default, @value{GDBN} only caches data
9271 known to be on the stack@footnote{In non-stop mode, it is moderately
9272 rare for a running thread to modify the stack of a stopped thread
9273 in a way that would interfere with a backtrace, and caching of
9274 stack reads provides a significant speed up of remote backtraces.}.
9275 Other regions of memory can be explicitly marked as
9276 cacheable; see @pxref{Memory Region Attributes}.
9279 @kindex set remotecache
9280 @item set remotecache on
9281 @itemx set remotecache off
9282 This option no longer does anything; it exists for compatibility
9285 @kindex show remotecache
9286 @item show remotecache
9287 Show the current state of the obsolete remotecache flag.
9289 @kindex set stack-cache
9290 @item set stack-cache on
9291 @itemx set stack-cache off
9292 Enable or disable caching of stack accesses. When @code{ON}, use
9293 caching. By default, this option is @code{ON}.
9295 @kindex show stack-cache
9296 @item show stack-cache
9297 Show the current state of data caching for memory accesses.
9300 @item info dcache @r{[}line@r{]}
9301 Print the information about the data cache performance. The
9302 information displayed includes the dcache width and depth, and for
9303 each cache line, its number, address, and how many times it was
9304 referenced. This command is useful for debugging the data cache
9307 If a line number is specified, the contents of that line will be
9311 @node Searching Memory
9312 @section Search Memory
9313 @cindex searching memory
9315 Memory can be searched for a particular sequence of bytes with the
9316 @code{find} command.
9320 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9321 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9322 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9323 etc. The search begins at address @var{start_addr} and continues for either
9324 @var{len} bytes or through to @var{end_addr} inclusive.
9327 @var{s} and @var{n} are optional parameters.
9328 They may be specified in either order, apart or together.
9331 @item @var{s}, search query size
9332 The size of each search query value.
9338 halfwords (two bytes)
9342 giant words (eight bytes)
9345 All values are interpreted in the current language.
9346 This means, for example, that if the current source language is C/C@t{++}
9347 then searching for the string ``hello'' includes the trailing '\0'.
9349 If the value size is not specified, it is taken from the
9350 value's type in the current language.
9351 This is useful when one wants to specify the search
9352 pattern as a mixture of types.
9353 Note that this means, for example, that in the case of C-like languages
9354 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9355 which is typically four bytes.
9357 @item @var{n}, maximum number of finds
9358 The maximum number of matches to print. The default is to print all finds.
9361 You can use strings as search values. Quote them with double-quotes
9363 The string value is copied into the search pattern byte by byte,
9364 regardless of the endianness of the target and the size specification.
9366 The address of each match found is printed as well as a count of the
9367 number of matches found.
9369 The address of the last value found is stored in convenience variable
9371 A count of the number of matches is stored in @samp{$numfound}.
9373 For example, if stopped at the @code{printf} in this function:
9379 static char hello[] = "hello-hello";
9380 static struct @{ char c; short s; int i; @}
9381 __attribute__ ((packed)) mixed
9382 = @{ 'c', 0x1234, 0x87654321 @};
9383 printf ("%s\n", hello);
9388 you get during debugging:
9391 (gdb) find &hello[0], +sizeof(hello), "hello"
9392 0x804956d <hello.1620+6>
9394 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9395 0x8049567 <hello.1620>
9396 0x804956d <hello.1620+6>
9398 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9399 0x8049567 <hello.1620>
9401 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9402 0x8049560 <mixed.1625>
9404 (gdb) print $numfound
9407 $2 = (void *) 0x8049560
9410 @node Optimized Code
9411 @chapter Debugging Optimized Code
9412 @cindex optimized code, debugging
9413 @cindex debugging optimized code
9415 Almost all compilers support optimization. With optimization
9416 disabled, the compiler generates assembly code that corresponds
9417 directly to your source code, in a simplistic way. As the compiler
9418 applies more powerful optimizations, the generated assembly code
9419 diverges from your original source code. With help from debugging
9420 information generated by the compiler, @value{GDBN} can map from
9421 the running program back to constructs from your original source.
9423 @value{GDBN} is more accurate with optimization disabled. If you
9424 can recompile without optimization, it is easier to follow the
9425 progress of your program during debugging. But, there are many cases
9426 where you may need to debug an optimized version.
9428 When you debug a program compiled with @samp{-g -O}, remember that the
9429 optimizer has rearranged your code; the debugger shows you what is
9430 really there. Do not be too surprised when the execution path does not
9431 exactly match your source file! An extreme example: if you define a
9432 variable, but never use it, @value{GDBN} never sees that
9433 variable---because the compiler optimizes it out of existence.
9435 Some things do not work as well with @samp{-g -O} as with just
9436 @samp{-g}, particularly on machines with instruction scheduling. If in
9437 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9438 please report it to us as a bug (including a test case!).
9439 @xref{Variables}, for more information about debugging optimized code.
9442 * Inline Functions:: How @value{GDBN} presents inlining
9445 @node Inline Functions
9446 @section Inline Functions
9447 @cindex inline functions, debugging
9449 @dfn{Inlining} is an optimization that inserts a copy of the function
9450 body directly at each call site, instead of jumping to a shared
9451 routine. @value{GDBN} displays inlined functions just like
9452 non-inlined functions. They appear in backtraces. You can view their
9453 arguments and local variables, step into them with @code{step}, skip
9454 them with @code{next}, and escape from them with @code{finish}.
9455 You can check whether a function was inlined by using the
9456 @code{info frame} command.
9458 For @value{GDBN} to support inlined functions, the compiler must
9459 record information about inlining in the debug information ---
9460 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9461 other compilers do also. @value{GDBN} only supports inlined functions
9462 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9463 do not emit two required attributes (@samp{DW_AT_call_file} and
9464 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9465 function calls with earlier versions of @value{NGCC}. It instead
9466 displays the arguments and local variables of inlined functions as
9467 local variables in the caller.
9469 The body of an inlined function is directly included at its call site;
9470 unlike a non-inlined function, there are no instructions devoted to
9471 the call. @value{GDBN} still pretends that the call site and the
9472 start of the inlined function are different instructions. Stepping to
9473 the call site shows the call site, and then stepping again shows
9474 the first line of the inlined function, even though no additional
9475 instructions are executed.
9477 This makes source-level debugging much clearer; you can see both the
9478 context of the call and then the effect of the call. Only stepping by
9479 a single instruction using @code{stepi} or @code{nexti} does not do
9480 this; single instruction steps always show the inlined body.
9482 There are some ways that @value{GDBN} does not pretend that inlined
9483 function calls are the same as normal calls:
9487 You cannot set breakpoints on inlined functions. @value{GDBN}
9488 either reports that there is no symbol with that name, or else sets the
9489 breakpoint only on non-inlined copies of the function. This limitation
9490 will be removed in a future version of @value{GDBN}; until then,
9491 set a breakpoint by line number on the first line of the inlined
9495 Setting breakpoints at the call site of an inlined function may not
9496 work, because the call site does not contain any code. @value{GDBN}
9497 may incorrectly move the breakpoint to the next line of the enclosing
9498 function, after the call. This limitation will be removed in a future
9499 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9500 or inside the inlined function instead.
9503 @value{GDBN} cannot locate the return value of inlined calls after
9504 using the @code{finish} command. This is a limitation of compiler-generated
9505 debugging information; after @code{finish}, you can step to the next line
9506 and print a variable where your program stored the return value.
9512 @chapter C Preprocessor Macros
9514 Some languages, such as C and C@t{++}, provide a way to define and invoke
9515 ``preprocessor macros'' which expand into strings of tokens.
9516 @value{GDBN} can evaluate expressions containing macro invocations, show
9517 the result of macro expansion, and show a macro's definition, including
9518 where it was defined.
9520 You may need to compile your program specially to provide @value{GDBN}
9521 with information about preprocessor macros. Most compilers do not
9522 include macros in their debugging information, even when you compile
9523 with the @option{-g} flag. @xref{Compilation}.
9525 A program may define a macro at one point, remove that definition later,
9526 and then provide a different definition after that. Thus, at different
9527 points in the program, a macro may have different definitions, or have
9528 no definition at all. If there is a current stack frame, @value{GDBN}
9529 uses the macros in scope at that frame's source code line. Otherwise,
9530 @value{GDBN} uses the macros in scope at the current listing location;
9533 Whenever @value{GDBN} evaluates an expression, it always expands any
9534 macro invocations present in the expression. @value{GDBN} also provides
9535 the following commands for working with macros explicitly.
9539 @kindex macro expand
9540 @cindex macro expansion, showing the results of preprocessor
9541 @cindex preprocessor macro expansion, showing the results of
9542 @cindex expanding preprocessor macros
9543 @item macro expand @var{expression}
9544 @itemx macro exp @var{expression}
9545 Show the results of expanding all preprocessor macro invocations in
9546 @var{expression}. Since @value{GDBN} simply expands macros, but does
9547 not parse the result, @var{expression} need not be a valid expression;
9548 it can be any string of tokens.
9551 @item macro expand-once @var{expression}
9552 @itemx macro exp1 @var{expression}
9553 @cindex expand macro once
9554 @i{(This command is not yet implemented.)} Show the results of
9555 expanding those preprocessor macro invocations that appear explicitly in
9556 @var{expression}. Macro invocations appearing in that expansion are
9557 left unchanged. This command allows you to see the effect of a
9558 particular macro more clearly, without being confused by further
9559 expansions. Since @value{GDBN} simply expands macros, but does not
9560 parse the result, @var{expression} need not be a valid expression; it
9561 can be any string of tokens.
9564 @cindex macro definition, showing
9565 @cindex definition, showing a macro's
9566 @item info macro @var{macro}
9567 Show the definition of the macro named @var{macro}, and describe the
9568 source location or compiler command-line where that definition was established.
9570 @kindex macro define
9571 @cindex user-defined macros
9572 @cindex defining macros interactively
9573 @cindex macros, user-defined
9574 @item macro define @var{macro} @var{replacement-list}
9575 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9576 Introduce a definition for a preprocessor macro named @var{macro},
9577 invocations of which are replaced by the tokens given in
9578 @var{replacement-list}. The first form of this command defines an
9579 ``object-like'' macro, which takes no arguments; the second form
9580 defines a ``function-like'' macro, which takes the arguments given in
9583 A definition introduced by this command is in scope in every
9584 expression evaluated in @value{GDBN}, until it is removed with the
9585 @code{macro undef} command, described below. The definition overrides
9586 all definitions for @var{macro} present in the program being debugged,
9587 as well as any previous user-supplied definition.
9590 @item macro undef @var{macro}
9591 Remove any user-supplied definition for the macro named @var{macro}.
9592 This command only affects definitions provided with the @code{macro
9593 define} command, described above; it cannot remove definitions present
9594 in the program being debugged.
9598 List all the macros defined using the @code{macro define} command.
9601 @cindex macros, example of debugging with
9602 Here is a transcript showing the above commands in action. First, we
9603 show our source files:
9611 #define ADD(x) (M + x)
9616 printf ("Hello, world!\n");
9618 printf ("We're so creative.\n");
9620 printf ("Goodbye, world!\n");
9627 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9628 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9629 compiler includes information about preprocessor macros in the debugging
9633 $ gcc -gdwarf-2 -g3 sample.c -o sample
9637 Now, we start @value{GDBN} on our sample program:
9641 GNU gdb 2002-05-06-cvs
9642 Copyright 2002 Free Software Foundation, Inc.
9643 GDB is free software, @dots{}
9647 We can expand macros and examine their definitions, even when the
9648 program is not running. @value{GDBN} uses the current listing position
9649 to decide which macro definitions are in scope:
9652 (@value{GDBP}) list main
9655 5 #define ADD(x) (M + x)
9660 10 printf ("Hello, world!\n");
9662 12 printf ("We're so creative.\n");
9663 (@value{GDBP}) info macro ADD
9664 Defined at /home/jimb/gdb/macros/play/sample.c:5
9665 #define ADD(x) (M + x)
9666 (@value{GDBP}) info macro Q
9667 Defined at /home/jimb/gdb/macros/play/sample.h:1
9668 included at /home/jimb/gdb/macros/play/sample.c:2
9670 (@value{GDBP}) macro expand ADD(1)
9671 expands to: (42 + 1)
9672 (@value{GDBP}) macro expand-once ADD(1)
9673 expands to: once (M + 1)
9677 In the example above, note that @code{macro expand-once} expands only
9678 the macro invocation explicit in the original text --- the invocation of
9679 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9680 which was introduced by @code{ADD}.
9682 Once the program is running, @value{GDBN} uses the macro definitions in
9683 force at the source line of the current stack frame:
9686 (@value{GDBP}) break main
9687 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9689 Starting program: /home/jimb/gdb/macros/play/sample
9691 Breakpoint 1, main () at sample.c:10
9692 10 printf ("Hello, world!\n");
9696 At line 10, the definition of the macro @code{N} at line 9 is in force:
9699 (@value{GDBP}) info macro N
9700 Defined at /home/jimb/gdb/macros/play/sample.c:9
9702 (@value{GDBP}) macro expand N Q M
9704 (@value{GDBP}) print N Q M
9709 As we step over directives that remove @code{N}'s definition, and then
9710 give it a new definition, @value{GDBN} finds the definition (or lack
9711 thereof) in force at each point:
9716 12 printf ("We're so creative.\n");
9717 (@value{GDBP}) info macro N
9718 The symbol `N' has no definition as a C/C++ preprocessor macro
9719 at /home/jimb/gdb/macros/play/sample.c:12
9722 14 printf ("Goodbye, world!\n");
9723 (@value{GDBP}) info macro N
9724 Defined at /home/jimb/gdb/macros/play/sample.c:13
9726 (@value{GDBP}) macro expand N Q M
9727 expands to: 1729 < 42
9728 (@value{GDBP}) print N Q M
9733 In addition to source files, macros can be defined on the compilation command
9734 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9735 such a way, @value{GDBN} displays the location of their definition as line zero
9736 of the source file submitted to the compiler.
9739 (@value{GDBP}) info macro __STDC__
9740 Defined at /home/jimb/gdb/macros/play/sample.c:0
9747 @chapter Tracepoints
9748 @c This chapter is based on the documentation written by Michael
9749 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9752 In some applications, it is not feasible for the debugger to interrupt
9753 the program's execution long enough for the developer to learn
9754 anything helpful about its behavior. If the program's correctness
9755 depends on its real-time behavior, delays introduced by a debugger
9756 might cause the program to change its behavior drastically, or perhaps
9757 fail, even when the code itself is correct. It is useful to be able
9758 to observe the program's behavior without interrupting it.
9760 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9761 specify locations in the program, called @dfn{tracepoints}, and
9762 arbitrary expressions to evaluate when those tracepoints are reached.
9763 Later, using the @code{tfind} command, you can examine the values
9764 those expressions had when the program hit the tracepoints. The
9765 expressions may also denote objects in memory---structures or arrays,
9766 for example---whose values @value{GDBN} should record; while visiting
9767 a particular tracepoint, you may inspect those objects as if they were
9768 in memory at that moment. However, because @value{GDBN} records these
9769 values without interacting with you, it can do so quickly and
9770 unobtrusively, hopefully not disturbing the program's behavior.
9772 The tracepoint facility is currently available only for remote
9773 targets. @xref{Targets}. In addition, your remote target must know
9774 how to collect trace data. This functionality is implemented in the
9775 remote stub; however, none of the stubs distributed with @value{GDBN}
9776 support tracepoints as of this writing. The format of the remote
9777 packets used to implement tracepoints are described in @ref{Tracepoint
9780 It is also possible to get trace data from a file, in a manner reminiscent
9781 of corefiles; you specify the filename, and use @code{tfind} to search
9782 through the file. @xref{Trace Files}, for more details.
9784 This chapter describes the tracepoint commands and features.
9788 * Analyze Collected Data::
9789 * Tracepoint Variables::
9793 @node Set Tracepoints
9794 @section Commands to Set Tracepoints
9796 Before running such a @dfn{trace experiment}, an arbitrary number of
9797 tracepoints can be set. A tracepoint is actually a special type of
9798 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9799 standard breakpoint commands. For instance, as with breakpoints,
9800 tracepoint numbers are successive integers starting from one, and many
9801 of the commands associated with tracepoints take the tracepoint number
9802 as their argument, to identify which tracepoint to work on.
9804 For each tracepoint, you can specify, in advance, some arbitrary set
9805 of data that you want the target to collect in the trace buffer when
9806 it hits that tracepoint. The collected data can include registers,
9807 local variables, or global data. Later, you can use @value{GDBN}
9808 commands to examine the values these data had at the time the
9811 Tracepoints do not support every breakpoint feature. Ignore counts on
9812 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9813 commands when they are hit. Tracepoints may not be thread-specific
9816 @cindex fast tracepoints
9817 Some targets may support @dfn{fast tracepoints}, which are inserted in
9818 a different way (such as with a jump instead of a trap), that is
9819 faster but possibly restricted in where they may be installed.
9821 @cindex static tracepoints
9822 @cindex markers, static tracepoints
9823 @cindex probing markers, static tracepoints
9824 Regular and fast tracepoints are dynamic tracing facilities, meaning
9825 that they can be used to insert tracepoints at (almost) any location
9826 in the target. Some targets may also support controlling @dfn{static
9827 tracepoints} from @value{GDBN}. With static tracing, a set of
9828 instrumentation points, also known as @dfn{markers}, are embedded in
9829 the target program, and can be activated or deactivated by name or
9830 address. These are usually placed at locations which facilitate
9831 investigating what the target is actually doing. @value{GDBN}'s
9832 support for static tracing includes being able to list instrumentation
9833 points, and attach them with @value{GDBN} defined high level
9834 tracepoints that expose the whole range of convenience of
9835 @value{GDBN}'s tracepoints support. Namely, support for collecting
9836 registers values and values of global or local (to the instrumentation
9837 point) variables; tracepoint conditions and trace state variables.
9838 The act of installing a @value{GDBN} static tracepoint on an
9839 instrumentation point, or marker, is referred to as @dfn{probing} a
9840 static tracepoint marker.
9842 @code{gdbserver} supports tracepoints on some target systems.
9843 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9845 This section describes commands to set tracepoints and associated
9846 conditions and actions.
9849 * Create and Delete Tracepoints::
9850 * Enable and Disable Tracepoints::
9851 * Tracepoint Passcounts::
9852 * Tracepoint Conditions::
9853 * Trace State Variables::
9854 * Tracepoint Actions::
9855 * Listing Tracepoints::
9856 * Listing Static Tracepoint Markers::
9857 * Starting and Stopping Trace Experiments::
9858 * Tracepoint Restrictions::
9861 @node Create and Delete Tracepoints
9862 @subsection Create and Delete Tracepoints
9865 @cindex set tracepoint
9867 @item trace @var{location}
9868 The @code{trace} command is very similar to the @code{break} command.
9869 Its argument @var{location} can be a source line, a function name, or
9870 an address in the target program. @xref{Specify Location}. The
9871 @code{trace} command defines a tracepoint, which is a point in the
9872 target program where the debugger will briefly stop, collect some
9873 data, and then allow the program to continue. Setting a tracepoint or
9874 changing its actions doesn't take effect until the next @code{tstart}
9875 command, and once a trace experiment is running, further changes will
9876 not have any effect until the next trace experiment starts.
9878 Here are some examples of using the @code{trace} command:
9881 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9883 (@value{GDBP}) @b{trace +2} // 2 lines forward
9885 (@value{GDBP}) @b{trace my_function} // first source line of function
9887 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9889 (@value{GDBP}) @b{trace *0x2117c4} // an address
9893 You can abbreviate @code{trace} as @code{tr}.
9895 @item trace @var{location} if @var{cond}
9896 Set a tracepoint with condition @var{cond}; evaluate the expression
9897 @var{cond} each time the tracepoint is reached, and collect data only
9898 if the value is nonzero---that is, if @var{cond} evaluates as true.
9899 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9900 information on tracepoint conditions.
9902 @item ftrace @var{location} [ if @var{cond} ]
9903 @cindex set fast tracepoint
9904 @cindex fast tracepoints, setting
9906 The @code{ftrace} command sets a fast tracepoint. For targets that
9907 support them, fast tracepoints will use a more efficient but possibly
9908 less general technique to trigger data collection, such as a jump
9909 instruction instead of a trap, or some sort of hardware support. It
9910 may not be possible to create a fast tracepoint at the desired
9911 location, in which case the command will exit with an explanatory
9914 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9917 @item strace @var{location} [ if @var{cond} ]
9918 @cindex set static tracepoint
9919 @cindex static tracepoints, setting
9920 @cindex probe static tracepoint marker
9922 The @code{strace} command sets a static tracepoint. For targets that
9923 support it, setting a static tracepoint probes a static
9924 instrumentation point, or marker, found at @var{location}. It may not
9925 be possible to set a static tracepoint at the desired location, in
9926 which case the command will exit with an explanatory message.
9928 @value{GDBN} handles arguments to @code{strace} exactly as for
9929 @code{trace}, with the addition that the user can also specify
9930 @code{-m @var{marker}} as @var{location}. This probes the marker
9931 identified by the @var{marker} string identifier. This identifier
9932 depends on the static tracepoint backend library your program is
9933 using. You can find all the marker identifiers in the @samp{ID} field
9934 of the @code{info static-tracepoint-markers} command output.
9935 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9936 Markers}. For example, in the following small program using the UST
9942 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9947 the marker id is composed of joining the first two arguments to the
9948 @code{trace_mark} call with a slash, which translates to:
9951 (@value{GDBP}) info static-tracepoint-markers
9952 Cnt Enb ID Address What
9953 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9959 so you may probe the marker above with:
9962 (@value{GDBP}) strace -m ust/bar33
9965 Static tracepoints accept an extra collect action --- @code{collect
9966 $_sdata}. This collects arbitrary user data passed in the probe point
9967 call to the tracing library. In the UST example above, you'll see
9968 that the third argument to @code{trace_mark} is a printf-like format
9969 string. The user data is then the result of running that formating
9970 string against the following arguments. Note that @code{info
9971 static-tracepoint-markers} command output lists that format string in
9972 the @samp{Data:} field.
9974 You can inspect this data when analyzing the trace buffer, by printing
9975 the $_sdata variable like any other variable available to
9976 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9979 @cindex last tracepoint number
9980 @cindex recent tracepoint number
9981 @cindex tracepoint number
9982 The convenience variable @code{$tpnum} records the tracepoint number
9983 of the most recently set tracepoint.
9985 @kindex delete tracepoint
9986 @cindex tracepoint deletion
9987 @item delete tracepoint @r{[}@var{num}@r{]}
9988 Permanently delete one or more tracepoints. With no argument, the
9989 default is to delete all tracepoints. Note that the regular
9990 @code{delete} command can remove tracepoints also.
9995 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9997 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10001 You can abbreviate this command as @code{del tr}.
10004 @node Enable and Disable Tracepoints
10005 @subsection Enable and Disable Tracepoints
10007 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10010 @kindex disable tracepoint
10011 @item disable tracepoint @r{[}@var{num}@r{]}
10012 Disable tracepoint @var{num}, or all tracepoints if no argument
10013 @var{num} is given. A disabled tracepoint will have no effect during
10014 the next trace experiment, but it is not forgotten. You can re-enable
10015 a disabled tracepoint using the @code{enable tracepoint} command.
10017 @kindex enable tracepoint
10018 @item enable tracepoint @r{[}@var{num}@r{]}
10019 Enable tracepoint @var{num}, or all tracepoints. The enabled
10020 tracepoints will become effective the next time a trace experiment is
10024 @node Tracepoint Passcounts
10025 @subsection Tracepoint Passcounts
10029 @cindex tracepoint pass count
10030 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10031 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10032 automatically stop a trace experiment. If a tracepoint's passcount is
10033 @var{n}, then the trace experiment will be automatically stopped on
10034 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10035 @var{num} is not specified, the @code{passcount} command sets the
10036 passcount of the most recently defined tracepoint. If no passcount is
10037 given, the trace experiment will run until stopped explicitly by the
10043 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10044 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10046 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10047 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10048 (@value{GDBP}) @b{trace foo}
10049 (@value{GDBP}) @b{pass 3}
10050 (@value{GDBP}) @b{trace bar}
10051 (@value{GDBP}) @b{pass 2}
10052 (@value{GDBP}) @b{trace baz}
10053 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10054 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10055 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10056 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10060 @node Tracepoint Conditions
10061 @subsection Tracepoint Conditions
10062 @cindex conditional tracepoints
10063 @cindex tracepoint conditions
10065 The simplest sort of tracepoint collects data every time your program
10066 reaches a specified place. You can also specify a @dfn{condition} for
10067 a tracepoint. A condition is just a Boolean expression in your
10068 programming language (@pxref{Expressions, ,Expressions}). A
10069 tracepoint with a condition evaluates the expression each time your
10070 program reaches it, and data collection happens only if the condition
10073 Tracepoint conditions can be specified when a tracepoint is set, by
10074 using @samp{if} in the arguments to the @code{trace} command.
10075 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10076 also be set or changed at any time with the @code{condition} command,
10077 just as with breakpoints.
10079 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10080 the conditional expression itself. Instead, @value{GDBN} encodes the
10081 expression into an agent expression (@pxref{Agent Expressions})
10082 suitable for execution on the target, independently of @value{GDBN}.
10083 Global variables become raw memory locations, locals become stack
10084 accesses, and so forth.
10086 For instance, suppose you have a function that is usually called
10087 frequently, but should not be called after an error has occurred. You
10088 could use the following tracepoint command to collect data about calls
10089 of that function that happen while the error code is propagating
10090 through the program; an unconditional tracepoint could end up
10091 collecting thousands of useless trace frames that you would have to
10095 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10098 @node Trace State Variables
10099 @subsection Trace State Variables
10100 @cindex trace state variables
10102 A @dfn{trace state variable} is a special type of variable that is
10103 created and managed by target-side code. The syntax is the same as
10104 that for GDB's convenience variables (a string prefixed with ``$''),
10105 but they are stored on the target. They must be created explicitly,
10106 using a @code{tvariable} command. They are always 64-bit signed
10109 Trace state variables are remembered by @value{GDBN}, and downloaded
10110 to the target along with tracepoint information when the trace
10111 experiment starts. There are no intrinsic limits on the number of
10112 trace state variables, beyond memory limitations of the target.
10114 @cindex convenience variables, and trace state variables
10115 Although trace state variables are managed by the target, you can use
10116 them in print commands and expressions as if they were convenience
10117 variables; @value{GDBN} will get the current value from the target
10118 while the trace experiment is running. Trace state variables share
10119 the same namespace as other ``$'' variables, which means that you
10120 cannot have trace state variables with names like @code{$23} or
10121 @code{$pc}, nor can you have a trace state variable and a convenience
10122 variable with the same name.
10126 @item tvariable $@var{name} [ = @var{expression} ]
10128 The @code{tvariable} command creates a new trace state variable named
10129 @code{$@var{name}}, and optionally gives it an initial value of
10130 @var{expression}. @var{expression} is evaluated when this command is
10131 entered; the result will be converted to an integer if possible,
10132 otherwise @value{GDBN} will report an error. A subsequent
10133 @code{tvariable} command specifying the same name does not create a
10134 variable, but instead assigns the supplied initial value to the
10135 existing variable of that name, overwriting any previous initial
10136 value. The default initial value is 0.
10138 @item info tvariables
10139 @kindex info tvariables
10140 List all the trace state variables along with their initial values.
10141 Their current values may also be displayed, if the trace experiment is
10144 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10145 @kindex delete tvariable
10146 Delete the given trace state variables, or all of them if no arguments
10151 @node Tracepoint Actions
10152 @subsection Tracepoint Action Lists
10156 @cindex tracepoint actions
10157 @item actions @r{[}@var{num}@r{]}
10158 This command will prompt for a list of actions to be taken when the
10159 tracepoint is hit. If the tracepoint number @var{num} is not
10160 specified, this command sets the actions for the one that was most
10161 recently defined (so that you can define a tracepoint and then say
10162 @code{actions} without bothering about its number). You specify the
10163 actions themselves on the following lines, one action at a time, and
10164 terminate the actions list with a line containing just @code{end}. So
10165 far, the only defined actions are @code{collect}, @code{teval}, and
10166 @code{while-stepping}.
10168 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10169 Commands, ,Breakpoint Command Lists}), except that only the defined
10170 actions are allowed; any other @value{GDBN} command is rejected.
10172 @cindex remove actions from a tracepoint
10173 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10174 and follow it immediately with @samp{end}.
10177 (@value{GDBP}) @b{collect @var{data}} // collect some data
10179 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10181 (@value{GDBP}) @b{end} // signals the end of actions.
10184 In the following example, the action list begins with @code{collect}
10185 commands indicating the things to be collected when the tracepoint is
10186 hit. Then, in order to single-step and collect additional data
10187 following the tracepoint, a @code{while-stepping} command is used,
10188 followed by the list of things to be collected after each step in a
10189 sequence of single steps. The @code{while-stepping} command is
10190 terminated by its own separate @code{end} command. Lastly, the action
10191 list is terminated by an @code{end} command.
10194 (@value{GDBP}) @b{trace foo}
10195 (@value{GDBP}) @b{actions}
10196 Enter actions for tracepoint 1, one per line:
10199 > while-stepping 12
10200 > collect $pc, arr[i]
10205 @kindex collect @r{(tracepoints)}
10206 @item collect @var{expr1}, @var{expr2}, @dots{}
10207 Collect values of the given expressions when the tracepoint is hit.
10208 This command accepts a comma-separated list of any valid expressions.
10209 In addition to global, static, or local variables, the following
10210 special arguments are supported:
10214 Collect all registers.
10217 Collect all function arguments.
10220 Collect all local variables.
10223 @vindex $_sdata@r{, collect}
10224 Collect static tracepoint marker specific data. Only available for
10225 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10226 Lists}. On the UST static tracepoints library backend, an
10227 instrumentation point resembles a @code{printf} function call. The
10228 tracing library is able to collect user specified data formatted to a
10229 character string using the format provided by the programmer that
10230 instrumented the program. Other backends have similar mechanisms.
10231 Here's an example of a UST marker call:
10234 const char master_name[] = "$your_name";
10235 trace_mark(channel1, marker1, "hello %s", master_name)
10238 In this case, collecting @code{$_sdata} collects the string
10239 @samp{hello $yourname}. When analyzing the trace buffer, you can
10240 inspect @samp{$_sdata} like any other variable available to
10244 You can give several consecutive @code{collect} commands, each one
10245 with a single argument, or one @code{collect} command with several
10246 arguments separated by commas; the effect is the same.
10248 The command @code{info scope} (@pxref{Symbols, info scope}) is
10249 particularly useful for figuring out what data to collect.
10251 @kindex teval @r{(tracepoints)}
10252 @item teval @var{expr1}, @var{expr2}, @dots{}
10253 Evaluate the given expressions when the tracepoint is hit. This
10254 command accepts a comma-separated list of expressions. The results
10255 are discarded, so this is mainly useful for assigning values to trace
10256 state variables (@pxref{Trace State Variables}) without adding those
10257 values to the trace buffer, as would be the case if the @code{collect}
10260 @kindex while-stepping @r{(tracepoints)}
10261 @item while-stepping @var{n}
10262 Perform @var{n} single-step instruction traces after the tracepoint,
10263 collecting new data after each step. The @code{while-stepping}
10264 command is followed by the list of what to collect while stepping
10265 (followed by its own @code{end} command):
10268 > while-stepping 12
10269 > collect $regs, myglobal
10275 Note that @code{$pc} is not automatically collected by
10276 @code{while-stepping}; you need to explicitly collect that register if
10277 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10280 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10281 @kindex set default-collect
10282 @cindex default collection action
10283 This variable is a list of expressions to collect at each tracepoint
10284 hit. It is effectively an additional @code{collect} action prepended
10285 to every tracepoint action list. The expressions are parsed
10286 individually for each tracepoint, so for instance a variable named
10287 @code{xyz} may be interpreted as a global for one tracepoint, and a
10288 local for another, as appropriate to the tracepoint's location.
10290 @item show default-collect
10291 @kindex show default-collect
10292 Show the list of expressions that are collected by default at each
10297 @node Listing Tracepoints
10298 @subsection Listing Tracepoints
10301 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10302 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10303 @cindex information about tracepoints
10304 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10305 Display information about the tracepoint @var{num}. If you don't
10306 specify a tracepoint number, displays information about all the
10307 tracepoints defined so far. The format is similar to that used for
10308 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10309 command, simply restricting itself to tracepoints.
10311 A tracepoint's listing may include additional information specific to
10316 its passcount as given by the @code{passcount @var{n}} command
10320 (@value{GDBP}) @b{info trace}
10321 Num Type Disp Enb Address What
10322 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10324 collect globfoo, $regs
10333 This command can be abbreviated @code{info tp}.
10336 @node Listing Static Tracepoint Markers
10337 @subsection Listing Static Tracepoint Markers
10340 @kindex info static-tracepoint-markers
10341 @cindex information about static tracepoint markers
10342 @item info static-tracepoint-markers
10343 Display information about all static tracepoint markers defined in the
10346 For each marker, the following columns are printed:
10350 An incrementing counter, output to help readability. This is not a
10353 The marker ID, as reported by the target.
10354 @item Enabled or Disabled
10355 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10356 that are not enabled.
10358 Where the marker is in your program, as a memory address.
10360 Where the marker is in the source for your program, as a file and line
10361 number. If the debug information included in the program does not
10362 allow @value{GDBN} to locate the source of the marker, this column
10363 will be left blank.
10367 In addition, the following information may be printed for each marker:
10371 User data passed to the tracing library by the marker call. In the
10372 UST backend, this is the format string passed as argument to the
10374 @item Static tracepoints probing the marker
10375 The list of static tracepoints attached to the marker.
10379 (@value{GDBP}) info static-tracepoint-markers
10380 Cnt ID Enb Address What
10381 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10382 Data: number1 %d number2 %d
10383 Probed by static tracepoints: #2
10384 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10390 @node Starting and Stopping Trace Experiments
10391 @subsection Starting and Stopping Trace Experiments
10395 @cindex start a new trace experiment
10396 @cindex collected data discarded
10398 This command takes no arguments. It starts the trace experiment, and
10399 begins collecting data. This has the side effect of discarding all
10400 the data collected in the trace buffer during the previous trace
10404 @cindex stop a running trace experiment
10406 This command takes no arguments. It ends the trace experiment, and
10407 stops collecting data.
10409 @strong{Note}: a trace experiment and data collection may stop
10410 automatically if any tracepoint's passcount is reached
10411 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10414 @cindex status of trace data collection
10415 @cindex trace experiment, status of
10417 This command displays the status of the current trace data
10421 Here is an example of the commands we described so far:
10424 (@value{GDBP}) @b{trace gdb_c_test}
10425 (@value{GDBP}) @b{actions}
10426 Enter actions for tracepoint #1, one per line.
10427 > collect $regs,$locals,$args
10428 > while-stepping 11
10432 (@value{GDBP}) @b{tstart}
10433 [time passes @dots{}]
10434 (@value{GDBP}) @b{tstop}
10437 @cindex disconnected tracing
10438 You can choose to continue running the trace experiment even if
10439 @value{GDBN} disconnects from the target, voluntarily or
10440 involuntarily. For commands such as @code{detach}, the debugger will
10441 ask what you want to do with the trace. But for unexpected
10442 terminations (@value{GDBN} crash, network outage), it would be
10443 unfortunate to lose hard-won trace data, so the variable
10444 @code{disconnected-tracing} lets you decide whether the trace should
10445 continue running without @value{GDBN}.
10448 @item set disconnected-tracing on
10449 @itemx set disconnected-tracing off
10450 @kindex set disconnected-tracing
10451 Choose whether a tracing run should continue to run if @value{GDBN}
10452 has disconnected from the target. Note that @code{detach} or
10453 @code{quit} will ask you directly what to do about a running trace no
10454 matter what this variable's setting, so the variable is mainly useful
10455 for handling unexpected situations, such as loss of the network.
10457 @item show disconnected-tracing
10458 @kindex show disconnected-tracing
10459 Show the current choice for disconnected tracing.
10463 When you reconnect to the target, the trace experiment may or may not
10464 still be running; it might have filled the trace buffer in the
10465 meantime, or stopped for one of the other reasons. If it is running,
10466 it will continue after reconnection.
10468 Upon reconnection, the target will upload information about the
10469 tracepoints in effect. @value{GDBN} will then compare that
10470 information to the set of tracepoints currently defined, and attempt
10471 to match them up, allowing for the possibility that the numbers may
10472 have changed due to creation and deletion in the meantime. If one of
10473 the target's tracepoints does not match any in @value{GDBN}, the
10474 debugger will create a new tracepoint, so that you have a number with
10475 which to specify that tracepoint. This matching-up process is
10476 necessarily heuristic, and it may result in useless tracepoints being
10477 created; you may simply delete them if they are of no use.
10479 @cindex circular trace buffer
10480 If your target agent supports a @dfn{circular trace buffer}, then you
10481 can run a trace experiment indefinitely without filling the trace
10482 buffer; when space runs out, the agent deletes already-collected trace
10483 frames, oldest first, until there is enough room to continue
10484 collecting. This is especially useful if your tracepoints are being
10485 hit too often, and your trace gets terminated prematurely because the
10486 buffer is full. To ask for a circular trace buffer, simply set
10487 @samp{circular-trace-buffer} to on. You can set this at any time,
10488 including during tracing; if the agent can do it, it will change
10489 buffer handling on the fly, otherwise it will not take effect until
10493 @item set circular-trace-buffer on
10494 @itemx set circular-trace-buffer off
10495 @kindex set circular-trace-buffer
10496 Choose whether a tracing run should use a linear or circular buffer
10497 for trace data. A linear buffer will not lose any trace data, but may
10498 fill up prematurely, while a circular buffer will discard old trace
10499 data, but it will have always room for the latest tracepoint hits.
10501 @item show circular-trace-buffer
10502 @kindex show circular-trace-buffer
10503 Show the current choice for the trace buffer. Note that this may not
10504 match the agent's current buffer handling, nor is it guaranteed to
10505 match the setting that might have been in effect during a past run,
10506 for instance if you are looking at frames from a trace file.
10510 @node Tracepoint Restrictions
10511 @subsection Tracepoint Restrictions
10513 @cindex tracepoint restrictions
10514 There are a number of restrictions on the use of tracepoints. As
10515 described above, tracepoint data gathering occurs on the target
10516 without interaction from @value{GDBN}. Thus the full capabilities of
10517 the debugger are not available during data gathering, and then at data
10518 examination time, you will be limited by only having what was
10519 collected. The following items describe some common problems, but it
10520 is not exhaustive, and you may run into additional difficulties not
10526 Tracepoint expressions are intended to gather objects (lvalues). Thus
10527 the full flexibility of GDB's expression evaluator is not available.
10528 You cannot call functions, cast objects to aggregate types, access
10529 convenience variables or modify values (except by assignment to trace
10530 state variables). Some language features may implicitly call
10531 functions (for instance Objective-C fields with accessors), and therefore
10532 cannot be collected either.
10535 Collection of local variables, either individually or in bulk with
10536 @code{$locals} or @code{$args}, during @code{while-stepping} may
10537 behave erratically. The stepping action may enter a new scope (for
10538 instance by stepping into a function), or the location of the variable
10539 may change (for instance it is loaded into a register). The
10540 tracepoint data recorded uses the location information for the
10541 variables that is correct for the tracepoint location. When the
10542 tracepoint is created, it is not possible, in general, to determine
10543 where the steps of a @code{while-stepping} sequence will advance the
10544 program---particularly if a conditional branch is stepped.
10547 Collection of an incompletely-initialized or partially-destroyed object
10548 may result in something that @value{GDBN} cannot display, or displays
10549 in a misleading way.
10552 When @value{GDBN} displays a pointer to character it automatically
10553 dereferences the pointer to also display characters of the string
10554 being pointed to. However, collecting the pointer during tracing does
10555 not automatically collect the string. You need to explicitly
10556 dereference the pointer and provide size information if you want to
10557 collect not only the pointer, but the memory pointed to. For example,
10558 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10562 It is not possible to collect a complete stack backtrace at a
10563 tracepoint. Instead, you may collect the registers and a few hundred
10564 bytes from the stack pointer with something like @code{*$esp@@300}
10565 (adjust to use the name of the actual stack pointer register on your
10566 target architecture, and the amount of stack you wish to capture).
10567 Then the @code{backtrace} command will show a partial backtrace when
10568 using a trace frame. The number of stack frames that can be examined
10569 depends on the sizes of the frames in the collected stack. Note that
10570 if you ask for a block so large that it goes past the bottom of the
10571 stack, the target agent may report an error trying to read from an
10575 If you do not collect registers at a tracepoint, @value{GDBN} can
10576 infer that the value of @code{$pc} must be the same as the address of
10577 the tracepoint and use that when you are looking at a trace frame
10578 for that tracepoint. However, this cannot work if the tracepoint has
10579 multiple locations (for instance if it was set in a function that was
10580 inlined), or if it has a @code{while-stepping} loop. In those cases
10581 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10586 @node Analyze Collected Data
10587 @section Using the Collected Data
10589 After the tracepoint experiment ends, you use @value{GDBN} commands
10590 for examining the trace data. The basic idea is that each tracepoint
10591 collects a trace @dfn{snapshot} every time it is hit and another
10592 snapshot every time it single-steps. All these snapshots are
10593 consecutively numbered from zero and go into a buffer, and you can
10594 examine them later. The way you examine them is to @dfn{focus} on a
10595 specific trace snapshot. When the remote stub is focused on a trace
10596 snapshot, it will respond to all @value{GDBN} requests for memory and
10597 registers by reading from the buffer which belongs to that snapshot,
10598 rather than from @emph{real} memory or registers of the program being
10599 debugged. This means that @strong{all} @value{GDBN} commands
10600 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10601 behave as if we were currently debugging the program state as it was
10602 when the tracepoint occurred. Any requests for data that are not in
10603 the buffer will fail.
10606 * tfind:: How to select a trace snapshot
10607 * tdump:: How to display all data for a snapshot
10608 * save tracepoints:: How to save tracepoints for a future run
10612 @subsection @code{tfind @var{n}}
10615 @cindex select trace snapshot
10616 @cindex find trace snapshot
10617 The basic command for selecting a trace snapshot from the buffer is
10618 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10619 counting from zero. If no argument @var{n} is given, the next
10620 snapshot is selected.
10622 Here are the various forms of using the @code{tfind} command.
10626 Find the first snapshot in the buffer. This is a synonym for
10627 @code{tfind 0} (since 0 is the number of the first snapshot).
10630 Stop debugging trace snapshots, resume @emph{live} debugging.
10633 Same as @samp{tfind none}.
10636 No argument means find the next trace snapshot.
10639 Find the previous trace snapshot before the current one. This permits
10640 retracing earlier steps.
10642 @item tfind tracepoint @var{num}
10643 Find the next snapshot associated with tracepoint @var{num}. Search
10644 proceeds forward from the last examined trace snapshot. If no
10645 argument @var{num} is given, it means find the next snapshot collected
10646 for the same tracepoint as the current snapshot.
10648 @item tfind pc @var{addr}
10649 Find the next snapshot associated with the value @var{addr} of the
10650 program counter. Search proceeds forward from the last examined trace
10651 snapshot. If no argument @var{addr} is given, it means find the next
10652 snapshot with the same value of PC as the current snapshot.
10654 @item tfind outside @var{addr1}, @var{addr2}
10655 Find the next snapshot whose PC is outside the given range of
10656 addresses (exclusive).
10658 @item tfind range @var{addr1}, @var{addr2}
10659 Find the next snapshot whose PC is between @var{addr1} and
10660 @var{addr2} (inclusive).
10662 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10663 Find the next snapshot associated with the source line @var{n}. If
10664 the optional argument @var{file} is given, refer to line @var{n} in
10665 that source file. Search proceeds forward from the last examined
10666 trace snapshot. If no argument @var{n} is given, it means find the
10667 next line other than the one currently being examined; thus saying
10668 @code{tfind line} repeatedly can appear to have the same effect as
10669 stepping from line to line in a @emph{live} debugging session.
10672 The default arguments for the @code{tfind} commands are specifically
10673 designed to make it easy to scan through the trace buffer. For
10674 instance, @code{tfind} with no argument selects the next trace
10675 snapshot, and @code{tfind -} with no argument selects the previous
10676 trace snapshot. So, by giving one @code{tfind} command, and then
10677 simply hitting @key{RET} repeatedly you can examine all the trace
10678 snapshots in order. Or, by saying @code{tfind -} and then hitting
10679 @key{RET} repeatedly you can examine the snapshots in reverse order.
10680 The @code{tfind line} command with no argument selects the snapshot
10681 for the next source line executed. The @code{tfind pc} command with
10682 no argument selects the next snapshot with the same program counter
10683 (PC) as the current frame. The @code{tfind tracepoint} command with
10684 no argument selects the next trace snapshot collected by the same
10685 tracepoint as the current one.
10687 In addition to letting you scan through the trace buffer manually,
10688 these commands make it easy to construct @value{GDBN} scripts that
10689 scan through the trace buffer and print out whatever collected data
10690 you are interested in. Thus, if we want to examine the PC, FP, and SP
10691 registers from each trace frame in the buffer, we can say this:
10694 (@value{GDBP}) @b{tfind start}
10695 (@value{GDBP}) @b{while ($trace_frame != -1)}
10696 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10697 $trace_frame, $pc, $sp, $fp
10701 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10702 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10703 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10704 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10705 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10706 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10707 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10708 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10709 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10710 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10711 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10714 Or, if we want to examine the variable @code{X} at each source line in
10718 (@value{GDBP}) @b{tfind start}
10719 (@value{GDBP}) @b{while ($trace_frame != -1)}
10720 > printf "Frame %d, X == %d\n", $trace_frame, X
10730 @subsection @code{tdump}
10732 @cindex dump all data collected at tracepoint
10733 @cindex tracepoint data, display
10735 This command takes no arguments. It prints all the data collected at
10736 the current trace snapshot.
10739 (@value{GDBP}) @b{trace 444}
10740 (@value{GDBP}) @b{actions}
10741 Enter actions for tracepoint #2, one per line:
10742 > collect $regs, $locals, $args, gdb_long_test
10745 (@value{GDBP}) @b{tstart}
10747 (@value{GDBP}) @b{tfind line 444}
10748 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10750 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10752 (@value{GDBP}) @b{tdump}
10753 Data collected at tracepoint 2, trace frame 1:
10754 d0 0xc4aa0085 -995491707
10758 d4 0x71aea3d 119204413
10761 d7 0x380035 3670069
10762 a0 0x19e24a 1696330
10763 a1 0x3000668 50333288
10765 a3 0x322000 3284992
10766 a4 0x3000698 50333336
10767 a5 0x1ad3cc 1758156
10768 fp 0x30bf3c 0x30bf3c
10769 sp 0x30bf34 0x30bf34
10771 pc 0x20b2c8 0x20b2c8
10775 p = 0x20e5b4 "gdb-test"
10782 gdb_long_test = 17 '\021'
10787 @code{tdump} works by scanning the tracepoint's current collection
10788 actions and printing the value of each expression listed. So
10789 @code{tdump} can fail, if after a run, you change the tracepoint's
10790 actions to mention variables that were not collected during the run.
10792 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10793 uses the collected value of @code{$pc} to distinguish between trace
10794 frames that were collected at the tracepoint hit, and frames that were
10795 collected while stepping. This allows it to correctly choose whether
10796 to display the basic list of collections, or the collections from the
10797 body of the while-stepping loop. However, if @code{$pc} was not collected,
10798 then @code{tdump} will always attempt to dump using the basic collection
10799 list, and may fail if a while-stepping frame does not include all the
10800 same data that is collected at the tracepoint hit.
10801 @c This is getting pretty arcane, example would be good.
10803 @node save tracepoints
10804 @subsection @code{save tracepoints @var{filename}}
10805 @kindex save tracepoints
10806 @kindex save-tracepoints
10807 @cindex save tracepoints for future sessions
10809 This command saves all current tracepoint definitions together with
10810 their actions and passcounts, into a file @file{@var{filename}}
10811 suitable for use in a later debugging session. To read the saved
10812 tracepoint definitions, use the @code{source} command (@pxref{Command
10813 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10814 alias for @w{@code{save tracepoints}}
10816 @node Tracepoint Variables
10817 @section Convenience Variables for Tracepoints
10818 @cindex tracepoint variables
10819 @cindex convenience variables for tracepoints
10822 @vindex $trace_frame
10823 @item (int) $trace_frame
10824 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10825 snapshot is selected.
10827 @vindex $tracepoint
10828 @item (int) $tracepoint
10829 The tracepoint for the current trace snapshot.
10831 @vindex $trace_line
10832 @item (int) $trace_line
10833 The line number for the current trace snapshot.
10835 @vindex $trace_file
10836 @item (char []) $trace_file
10837 The source file for the current trace snapshot.
10839 @vindex $trace_func
10840 @item (char []) $trace_func
10841 The name of the function containing @code{$tracepoint}.
10844 Note: @code{$trace_file} is not suitable for use in @code{printf},
10845 use @code{output} instead.
10847 Here's a simple example of using these convenience variables for
10848 stepping through all the trace snapshots and printing some of their
10849 data. Note that these are not the same as trace state variables,
10850 which are managed by the target.
10853 (@value{GDBP}) @b{tfind start}
10855 (@value{GDBP}) @b{while $trace_frame != -1}
10856 > output $trace_file
10857 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10863 @section Using Trace Files
10864 @cindex trace files
10866 In some situations, the target running a trace experiment may no
10867 longer be available; perhaps it crashed, or the hardware was needed
10868 for a different activity. To handle these cases, you can arrange to
10869 dump the trace data into a file, and later use that file as a source
10870 of trace data, via the @code{target tfile} command.
10875 @item tsave [ -r ] @var{filename}
10876 Save the trace data to @var{filename}. By default, this command
10877 assumes that @var{filename} refers to the host filesystem, so if
10878 necessary @value{GDBN} will copy raw trace data up from the target and
10879 then save it. If the target supports it, you can also supply the
10880 optional argument @code{-r} (``remote'') to direct the target to save
10881 the data directly into @var{filename} in its own filesystem, which may be
10882 more efficient if the trace buffer is very large. (Note, however, that
10883 @code{target tfile} can only read from files accessible to the host.)
10885 @kindex target tfile
10887 @item target tfile @var{filename}
10888 Use the file named @var{filename} as a source of trace data. Commands
10889 that examine data work as they do with a live target, but it is not
10890 possible to run any new trace experiments. @code{tstatus} will report
10891 the state of the trace run at the moment the data was saved, as well
10892 as the current trace frame you are examining. @var{filename} must be
10893 on a filesystem accessible to the host.
10898 @chapter Debugging Programs That Use Overlays
10901 If your program is too large to fit completely in your target system's
10902 memory, you can sometimes use @dfn{overlays} to work around this
10903 problem. @value{GDBN} provides some support for debugging programs that
10907 * How Overlays Work:: A general explanation of overlays.
10908 * Overlay Commands:: Managing overlays in @value{GDBN}.
10909 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10910 mapped by asking the inferior.
10911 * Overlay Sample Program:: A sample program using overlays.
10914 @node How Overlays Work
10915 @section How Overlays Work
10916 @cindex mapped overlays
10917 @cindex unmapped overlays
10918 @cindex load address, overlay's
10919 @cindex mapped address
10920 @cindex overlay area
10922 Suppose you have a computer whose instruction address space is only 64
10923 kilobytes long, but which has much more memory which can be accessed by
10924 other means: special instructions, segment registers, or memory
10925 management hardware, for example. Suppose further that you want to
10926 adapt a program which is larger than 64 kilobytes to run on this system.
10928 One solution is to identify modules of your program which are relatively
10929 independent, and need not call each other directly; call these modules
10930 @dfn{overlays}. Separate the overlays from the main program, and place
10931 their machine code in the larger memory. Place your main program in
10932 instruction memory, but leave at least enough space there to hold the
10933 largest overlay as well.
10935 Now, to call a function located in an overlay, you must first copy that
10936 overlay's machine code from the large memory into the space set aside
10937 for it in the instruction memory, and then jump to its entry point
10940 @c NB: In the below the mapped area's size is greater or equal to the
10941 @c size of all overlays. This is intentional to remind the developer
10942 @c that overlays don't necessarily need to be the same size.
10946 Data Instruction Larger
10947 Address Space Address Space Address Space
10948 +-----------+ +-----------+ +-----------+
10950 +-----------+ +-----------+ +-----------+<-- overlay 1
10951 | program | | main | .----| overlay 1 | load address
10952 | variables | | program | | +-----------+
10953 | and heap | | | | | |
10954 +-----------+ | | | +-----------+<-- overlay 2
10955 | | +-----------+ | | | load address
10956 +-----------+ | | | .-| overlay 2 |
10958 mapped --->+-----------+ | | +-----------+
10959 address | | | | | |
10960 | overlay | <-' | | |
10961 | area | <---' +-----------+<-- overlay 3
10962 | | <---. | | load address
10963 +-----------+ `--| overlay 3 |
10970 @anchor{A code overlay}A code overlay
10974 The diagram (@pxref{A code overlay}) shows a system with separate data
10975 and instruction address spaces. To map an overlay, the program copies
10976 its code from the larger address space to the instruction address space.
10977 Since the overlays shown here all use the same mapped address, only one
10978 may be mapped at a time. For a system with a single address space for
10979 data and instructions, the diagram would be similar, except that the
10980 program variables and heap would share an address space with the main
10981 program and the overlay area.
10983 An overlay loaded into instruction memory and ready for use is called a
10984 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10985 instruction memory. An overlay not present (or only partially present)
10986 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10987 is its address in the larger memory. The mapped address is also called
10988 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10989 called the @dfn{load memory address}, or @dfn{LMA}.
10991 Unfortunately, overlays are not a completely transparent way to adapt a
10992 program to limited instruction memory. They introduce a new set of
10993 global constraints you must keep in mind as you design your program:
10998 Before calling or returning to a function in an overlay, your program
10999 must make sure that overlay is actually mapped. Otherwise, the call or
11000 return will transfer control to the right address, but in the wrong
11001 overlay, and your program will probably crash.
11004 If the process of mapping an overlay is expensive on your system, you
11005 will need to choose your overlays carefully to minimize their effect on
11006 your program's performance.
11009 The executable file you load onto your system must contain each
11010 overlay's instructions, appearing at the overlay's load address, not its
11011 mapped address. However, each overlay's instructions must be relocated
11012 and its symbols defined as if the overlay were at its mapped address.
11013 You can use GNU linker scripts to specify different load and relocation
11014 addresses for pieces of your program; see @ref{Overlay Description,,,
11015 ld.info, Using ld: the GNU linker}.
11018 The procedure for loading executable files onto your system must be able
11019 to load their contents into the larger address space as well as the
11020 instruction and data spaces.
11024 The overlay system described above is rather simple, and could be
11025 improved in many ways:
11030 If your system has suitable bank switch registers or memory management
11031 hardware, you could use those facilities to make an overlay's load area
11032 contents simply appear at their mapped address in instruction space.
11033 This would probably be faster than copying the overlay to its mapped
11034 area in the usual way.
11037 If your overlays are small enough, you could set aside more than one
11038 overlay area, and have more than one overlay mapped at a time.
11041 You can use overlays to manage data, as well as instructions. In
11042 general, data overlays are even less transparent to your design than
11043 code overlays: whereas code overlays only require care when you call or
11044 return to functions, data overlays require care every time you access
11045 the data. Also, if you change the contents of a data overlay, you
11046 must copy its contents back out to its load address before you can copy a
11047 different data overlay into the same mapped area.
11052 @node Overlay Commands
11053 @section Overlay Commands
11055 To use @value{GDBN}'s overlay support, each overlay in your program must
11056 correspond to a separate section of the executable file. The section's
11057 virtual memory address and load memory address must be the overlay's
11058 mapped and load addresses. Identifying overlays with sections allows
11059 @value{GDBN} to determine the appropriate address of a function or
11060 variable, depending on whether the overlay is mapped or not.
11062 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11063 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11068 Disable @value{GDBN}'s overlay support. When overlay support is
11069 disabled, @value{GDBN} assumes that all functions and variables are
11070 always present at their mapped addresses. By default, @value{GDBN}'s
11071 overlay support is disabled.
11073 @item overlay manual
11074 @cindex manual overlay debugging
11075 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11076 relies on you to tell it which overlays are mapped, and which are not,
11077 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11078 commands described below.
11080 @item overlay map-overlay @var{overlay}
11081 @itemx overlay map @var{overlay}
11082 @cindex map an overlay
11083 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11084 be the name of the object file section containing the overlay. When an
11085 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11086 functions and variables at their mapped addresses. @value{GDBN} assumes
11087 that any other overlays whose mapped ranges overlap that of
11088 @var{overlay} are now unmapped.
11090 @item overlay unmap-overlay @var{overlay}
11091 @itemx overlay unmap @var{overlay}
11092 @cindex unmap an overlay
11093 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11094 must be the name of the object file section containing the overlay.
11095 When an overlay is unmapped, @value{GDBN} assumes it can find the
11096 overlay's functions and variables at their load addresses.
11099 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11100 consults a data structure the overlay manager maintains in the inferior
11101 to see which overlays are mapped. For details, see @ref{Automatic
11102 Overlay Debugging}.
11104 @item overlay load-target
11105 @itemx overlay load
11106 @cindex reloading the overlay table
11107 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11108 re-reads the table @value{GDBN} automatically each time the inferior
11109 stops, so this command should only be necessary if you have changed the
11110 overlay mapping yourself using @value{GDBN}. This command is only
11111 useful when using automatic overlay debugging.
11113 @item overlay list-overlays
11114 @itemx overlay list
11115 @cindex listing mapped overlays
11116 Display a list of the overlays currently mapped, along with their mapped
11117 addresses, load addresses, and sizes.
11121 Normally, when @value{GDBN} prints a code address, it includes the name
11122 of the function the address falls in:
11125 (@value{GDBP}) print main
11126 $3 = @{int ()@} 0x11a0 <main>
11129 When overlay debugging is enabled, @value{GDBN} recognizes code in
11130 unmapped overlays, and prints the names of unmapped functions with
11131 asterisks around them. For example, if @code{foo} is a function in an
11132 unmapped overlay, @value{GDBN} prints it this way:
11135 (@value{GDBP}) overlay list
11136 No sections are mapped.
11137 (@value{GDBP}) print foo
11138 $5 = @{int (int)@} 0x100000 <*foo*>
11141 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11145 (@value{GDBP}) overlay list
11146 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11147 mapped at 0x1016 - 0x104a
11148 (@value{GDBP}) print foo
11149 $6 = @{int (int)@} 0x1016 <foo>
11152 When overlay debugging is enabled, @value{GDBN} can find the correct
11153 address for functions and variables in an overlay, whether or not the
11154 overlay is mapped. This allows most @value{GDBN} commands, like
11155 @code{break} and @code{disassemble}, to work normally, even on unmapped
11156 code. However, @value{GDBN}'s breakpoint support has some limitations:
11160 @cindex breakpoints in overlays
11161 @cindex overlays, setting breakpoints in
11162 You can set breakpoints in functions in unmapped overlays, as long as
11163 @value{GDBN} can write to the overlay at its load address.
11165 @value{GDBN} can not set hardware or simulator-based breakpoints in
11166 unmapped overlays. However, if you set a breakpoint at the end of your
11167 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11168 you are using manual overlay management), @value{GDBN} will re-set its
11169 breakpoints properly.
11173 @node Automatic Overlay Debugging
11174 @section Automatic Overlay Debugging
11175 @cindex automatic overlay debugging
11177 @value{GDBN} can automatically track which overlays are mapped and which
11178 are not, given some simple co-operation from the overlay manager in the
11179 inferior. If you enable automatic overlay debugging with the
11180 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11181 looks in the inferior's memory for certain variables describing the
11182 current state of the overlays.
11184 Here are the variables your overlay manager must define to support
11185 @value{GDBN}'s automatic overlay debugging:
11189 @item @code{_ovly_table}:
11190 This variable must be an array of the following structures:
11195 /* The overlay's mapped address. */
11198 /* The size of the overlay, in bytes. */
11199 unsigned long size;
11201 /* The overlay's load address. */
11204 /* Non-zero if the overlay is currently mapped;
11206 unsigned long mapped;
11210 @item @code{_novlys}:
11211 This variable must be a four-byte signed integer, holding the total
11212 number of elements in @code{_ovly_table}.
11216 To decide whether a particular overlay is mapped or not, @value{GDBN}
11217 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11218 @code{lma} members equal the VMA and LMA of the overlay's section in the
11219 executable file. When @value{GDBN} finds a matching entry, it consults
11220 the entry's @code{mapped} member to determine whether the overlay is
11223 In addition, your overlay manager may define a function called
11224 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11225 will silently set a breakpoint there. If the overlay manager then
11226 calls this function whenever it has changed the overlay table, this
11227 will enable @value{GDBN} to accurately keep track of which overlays
11228 are in program memory, and update any breakpoints that may be set
11229 in overlays. This will allow breakpoints to work even if the
11230 overlays are kept in ROM or other non-writable memory while they
11231 are not being executed.
11233 @node Overlay Sample Program
11234 @section Overlay Sample Program
11235 @cindex overlay example program
11237 When linking a program which uses overlays, you must place the overlays
11238 at their load addresses, while relocating them to run at their mapped
11239 addresses. To do this, you must write a linker script (@pxref{Overlay
11240 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11241 since linker scripts are specific to a particular host system, target
11242 architecture, and target memory layout, this manual cannot provide
11243 portable sample code demonstrating @value{GDBN}'s overlay support.
11245 However, the @value{GDBN} source distribution does contain an overlaid
11246 program, with linker scripts for a few systems, as part of its test
11247 suite. The program consists of the following files from
11248 @file{gdb/testsuite/gdb.base}:
11252 The main program file.
11254 A simple overlay manager, used by @file{overlays.c}.
11259 Overlay modules, loaded and used by @file{overlays.c}.
11262 Linker scripts for linking the test program on the @code{d10v-elf}
11263 and @code{m32r-elf} targets.
11266 You can build the test program using the @code{d10v-elf} GCC
11267 cross-compiler like this:
11270 $ d10v-elf-gcc -g -c overlays.c
11271 $ d10v-elf-gcc -g -c ovlymgr.c
11272 $ d10v-elf-gcc -g -c foo.c
11273 $ d10v-elf-gcc -g -c bar.c
11274 $ d10v-elf-gcc -g -c baz.c
11275 $ d10v-elf-gcc -g -c grbx.c
11276 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11277 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11280 The build process is identical for any other architecture, except that
11281 you must substitute the appropriate compiler and linker script for the
11282 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11286 @chapter Using @value{GDBN} with Different Languages
11289 Although programming languages generally have common aspects, they are
11290 rarely expressed in the same manner. For instance, in ANSI C,
11291 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11292 Modula-2, it is accomplished by @code{p^}. Values can also be
11293 represented (and displayed) differently. Hex numbers in C appear as
11294 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11296 @cindex working language
11297 Language-specific information is built into @value{GDBN} for some languages,
11298 allowing you to express operations like the above in your program's
11299 native language, and allowing @value{GDBN} to output values in a manner
11300 consistent with the syntax of your program's native language. The
11301 language you use to build expressions is called the @dfn{working
11305 * Setting:: Switching between source languages
11306 * Show:: Displaying the language
11307 * Checks:: Type and range checks
11308 * Supported Languages:: Supported languages
11309 * Unsupported Languages:: Unsupported languages
11313 @section Switching Between Source Languages
11315 There are two ways to control the working language---either have @value{GDBN}
11316 set it automatically, or select it manually yourself. You can use the
11317 @code{set language} command for either purpose. On startup, @value{GDBN}
11318 defaults to setting the language automatically. The working language is
11319 used to determine how expressions you type are interpreted, how values
11322 In addition to the working language, every source file that
11323 @value{GDBN} knows about has its own working language. For some object
11324 file formats, the compiler might indicate which language a particular
11325 source file is in. However, most of the time @value{GDBN} infers the
11326 language from the name of the file. The language of a source file
11327 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11328 show each frame appropriately for its own language. There is no way to
11329 set the language of a source file from within @value{GDBN}, but you can
11330 set the language associated with a filename extension. @xref{Show, ,
11331 Displaying the Language}.
11333 This is most commonly a problem when you use a program, such
11334 as @code{cfront} or @code{f2c}, that generates C but is written in
11335 another language. In that case, make the
11336 program use @code{#line} directives in its C output; that way
11337 @value{GDBN} will know the correct language of the source code of the original
11338 program, and will display that source code, not the generated C code.
11341 * Filenames:: Filename extensions and languages.
11342 * Manually:: Setting the working language manually
11343 * Automatically:: Having @value{GDBN} infer the source language
11347 @subsection List of Filename Extensions and Languages
11349 If a source file name ends in one of the following extensions, then
11350 @value{GDBN} infers that its language is the one indicated.
11368 C@t{++} source file
11374 Objective-C source file
11378 Fortran source file
11381 Modula-2 source file
11385 Assembler source file. This actually behaves almost like C, but
11386 @value{GDBN} does not skip over function prologues when stepping.
11389 In addition, you may set the language associated with a filename
11390 extension. @xref{Show, , Displaying the Language}.
11393 @subsection Setting the Working Language
11395 If you allow @value{GDBN} to set the language automatically,
11396 expressions are interpreted the same way in your debugging session and
11399 @kindex set language
11400 If you wish, you may set the language manually. To do this, issue the
11401 command @samp{set language @var{lang}}, where @var{lang} is the name of
11402 a language, such as
11403 @code{c} or @code{modula-2}.
11404 For a list of the supported languages, type @samp{set language}.
11406 Setting the language manually prevents @value{GDBN} from updating the working
11407 language automatically. This can lead to confusion if you try
11408 to debug a program when the working language is not the same as the
11409 source language, when an expression is acceptable to both
11410 languages---but means different things. For instance, if the current
11411 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11419 might not have the effect you intended. In C, this means to add
11420 @code{b} and @code{c} and place the result in @code{a}. The result
11421 printed would be the value of @code{a}. In Modula-2, this means to compare
11422 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11424 @node Automatically
11425 @subsection Having @value{GDBN} Infer the Source Language
11427 To have @value{GDBN} set the working language automatically, use
11428 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11429 then infers the working language. That is, when your program stops in a
11430 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11431 working language to the language recorded for the function in that
11432 frame. If the language for a frame is unknown (that is, if the function
11433 or block corresponding to the frame was defined in a source file that
11434 does not have a recognized extension), the current working language is
11435 not changed, and @value{GDBN} issues a warning.
11437 This may not seem necessary for most programs, which are written
11438 entirely in one source language. However, program modules and libraries
11439 written in one source language can be used by a main program written in
11440 a different source language. Using @samp{set language auto} in this
11441 case frees you from having to set the working language manually.
11444 @section Displaying the Language
11446 The following commands help you find out which language is the
11447 working language, and also what language source files were written in.
11450 @item show language
11451 @kindex show language
11452 Display the current working language. This is the
11453 language you can use with commands such as @code{print} to
11454 build and compute expressions that may involve variables in your program.
11457 @kindex info frame@r{, show the source language}
11458 Display the source language for this frame. This language becomes the
11459 working language if you use an identifier from this frame.
11460 @xref{Frame Info, ,Information about a Frame}, to identify the other
11461 information listed here.
11464 @kindex info source@r{, show the source language}
11465 Display the source language of this source file.
11466 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11467 information listed here.
11470 In unusual circumstances, you may have source files with extensions
11471 not in the standard list. You can then set the extension associated
11472 with a language explicitly:
11475 @item set extension-language @var{ext} @var{language}
11476 @kindex set extension-language
11477 Tell @value{GDBN} that source files with extension @var{ext} are to be
11478 assumed as written in the source language @var{language}.
11480 @item info extensions
11481 @kindex info extensions
11482 List all the filename extensions and the associated languages.
11486 @section Type and Range Checking
11489 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11490 checking are included, but they do not yet have any effect. This
11491 section documents the intended facilities.
11493 @c FIXME remove warning when type/range code added
11495 Some languages are designed to guard you against making seemingly common
11496 errors through a series of compile- and run-time checks. These include
11497 checking the type of arguments to functions and operators, and making
11498 sure mathematical overflows are caught at run time. Checks such as
11499 these help to ensure a program's correctness once it has been compiled
11500 by eliminating type mismatches, and providing active checks for range
11501 errors when your program is running.
11503 @value{GDBN} can check for conditions like the above if you wish.
11504 Although @value{GDBN} does not check the statements in your program,
11505 it can check expressions entered directly into @value{GDBN} for
11506 evaluation via the @code{print} command, for example. As with the
11507 working language, @value{GDBN} can also decide whether or not to check
11508 automatically based on your program's source language.
11509 @xref{Supported Languages, ,Supported Languages}, for the default
11510 settings of supported languages.
11513 * Type Checking:: An overview of type checking
11514 * Range Checking:: An overview of range checking
11517 @cindex type checking
11518 @cindex checks, type
11519 @node Type Checking
11520 @subsection An Overview of Type Checking
11522 Some languages, such as Modula-2, are strongly typed, meaning that the
11523 arguments to operators and functions have to be of the correct type,
11524 otherwise an error occurs. These checks prevent type mismatch
11525 errors from ever causing any run-time problems. For example,
11533 The second example fails because the @code{CARDINAL} 1 is not
11534 type-compatible with the @code{REAL} 2.3.
11536 For the expressions you use in @value{GDBN} commands, you can tell the
11537 @value{GDBN} type checker to skip checking;
11538 to treat any mismatches as errors and abandon the expression;
11539 or to only issue warnings when type mismatches occur,
11540 but evaluate the expression anyway. When you choose the last of
11541 these, @value{GDBN} evaluates expressions like the second example above, but
11542 also issues a warning.
11544 Even if you turn type checking off, there may be other reasons
11545 related to type that prevent @value{GDBN} from evaluating an expression.
11546 For instance, @value{GDBN} does not know how to add an @code{int} and
11547 a @code{struct foo}. These particular type errors have nothing to do
11548 with the language in use, and usually arise from expressions, such as
11549 the one described above, which make little sense to evaluate anyway.
11551 Each language defines to what degree it is strict about type. For
11552 instance, both Modula-2 and C require the arguments to arithmetical
11553 operators to be numbers. In C, enumerated types and pointers can be
11554 represented as numbers, so that they are valid arguments to mathematical
11555 operators. @xref{Supported Languages, ,Supported Languages}, for further
11556 details on specific languages.
11558 @value{GDBN} provides some additional commands for controlling the type checker:
11560 @kindex set check type
11561 @kindex show check type
11563 @item set check type auto
11564 Set type checking on or off based on the current working language.
11565 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11568 @item set check type on
11569 @itemx set check type off
11570 Set type checking on or off, overriding the default setting for the
11571 current working language. Issue a warning if the setting does not
11572 match the language default. If any type mismatches occur in
11573 evaluating an expression while type checking is on, @value{GDBN} prints a
11574 message and aborts evaluation of the expression.
11576 @item set check type warn
11577 Cause the type checker to issue warnings, but to always attempt to
11578 evaluate the expression. Evaluating the expression may still
11579 be impossible for other reasons. For example, @value{GDBN} cannot add
11580 numbers and structures.
11583 Show the current setting of the type checker, and whether or not @value{GDBN}
11584 is setting it automatically.
11587 @cindex range checking
11588 @cindex checks, range
11589 @node Range Checking
11590 @subsection An Overview of Range Checking
11592 In some languages (such as Modula-2), it is an error to exceed the
11593 bounds of a type; this is enforced with run-time checks. Such range
11594 checking is meant to ensure program correctness by making sure
11595 computations do not overflow, or indices on an array element access do
11596 not exceed the bounds of the array.
11598 For expressions you use in @value{GDBN} commands, you can tell
11599 @value{GDBN} to treat range errors in one of three ways: ignore them,
11600 always treat them as errors and abandon the expression, or issue
11601 warnings but evaluate the expression anyway.
11603 A range error can result from numerical overflow, from exceeding an
11604 array index bound, or when you type a constant that is not a member
11605 of any type. Some languages, however, do not treat overflows as an
11606 error. In many implementations of C, mathematical overflow causes the
11607 result to ``wrap around'' to lower values---for example, if @var{m} is
11608 the largest integer value, and @var{s} is the smallest, then
11611 @var{m} + 1 @result{} @var{s}
11614 This, too, is specific to individual languages, and in some cases
11615 specific to individual compilers or machines. @xref{Supported Languages, ,
11616 Supported Languages}, for further details on specific languages.
11618 @value{GDBN} provides some additional commands for controlling the range checker:
11620 @kindex set check range
11621 @kindex show check range
11623 @item set check range auto
11624 Set range checking on or off based on the current working language.
11625 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11628 @item set check range on
11629 @itemx set check range off
11630 Set range checking on or off, overriding the default setting for the
11631 current working language. A warning is issued if the setting does not
11632 match the language default. If a range error occurs and range checking is on,
11633 then a message is printed and evaluation of the expression is aborted.
11635 @item set check range warn
11636 Output messages when the @value{GDBN} range checker detects a range error,
11637 but attempt to evaluate the expression anyway. Evaluating the
11638 expression may still be impossible for other reasons, such as accessing
11639 memory that the process does not own (a typical example from many Unix
11643 Show the current setting of the range checker, and whether or not it is
11644 being set automatically by @value{GDBN}.
11647 @node Supported Languages
11648 @section Supported Languages
11650 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11651 assembly, Modula-2, and Ada.
11652 @c This is false ...
11653 Some @value{GDBN} features may be used in expressions regardless of the
11654 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11655 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11656 ,Expressions}) can be used with the constructs of any supported
11659 The following sections detail to what degree each source language is
11660 supported by @value{GDBN}. These sections are not meant to be language
11661 tutorials or references, but serve only as a reference guide to what the
11662 @value{GDBN} expression parser accepts, and what input and output
11663 formats should look like for different languages. There are many good
11664 books written on each of these languages; please look to these for a
11665 language reference or tutorial.
11668 * C:: C and C@t{++}
11670 * Objective-C:: Objective-C
11671 * OpenCL C:: OpenCL C
11672 * Fortran:: Fortran
11674 * Modula-2:: Modula-2
11679 @subsection C and C@t{++}
11681 @cindex C and C@t{++}
11682 @cindex expressions in C or C@t{++}
11684 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11685 to both languages. Whenever this is the case, we discuss those languages
11689 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11690 @cindex @sc{gnu} C@t{++}
11691 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11692 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11693 effectively, you must compile your C@t{++} programs with a supported
11694 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11695 compiler (@code{aCC}).
11697 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11698 format; if it doesn't work on your system, try the stabs+ debugging
11699 format. You can select those formats explicitly with the @code{g++}
11700 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11701 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11702 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11705 * C Operators:: C and C@t{++} operators
11706 * C Constants:: C and C@t{++} constants
11707 * C Plus Plus Expressions:: C@t{++} expressions
11708 * C Defaults:: Default settings for C and C@t{++}
11709 * C Checks:: C and C@t{++} type and range checks
11710 * Debugging C:: @value{GDBN} and C
11711 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11712 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11716 @subsubsection C and C@t{++} Operators
11718 @cindex C and C@t{++} operators
11720 Operators must be defined on values of specific types. For instance,
11721 @code{+} is defined on numbers, but not on structures. Operators are
11722 often defined on groups of types.
11724 For the purposes of C and C@t{++}, the following definitions hold:
11729 @emph{Integral types} include @code{int} with any of its storage-class
11730 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11733 @emph{Floating-point types} include @code{float}, @code{double}, and
11734 @code{long double} (if supported by the target platform).
11737 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11740 @emph{Scalar types} include all of the above.
11745 The following operators are supported. They are listed here
11746 in order of increasing precedence:
11750 The comma or sequencing operator. Expressions in a comma-separated list
11751 are evaluated from left to right, with the result of the entire
11752 expression being the last expression evaluated.
11755 Assignment. The value of an assignment expression is the value
11756 assigned. Defined on scalar types.
11759 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11760 and translated to @w{@code{@var{a} = @var{a op b}}}.
11761 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11762 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11763 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11766 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11767 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11771 Logical @sc{or}. Defined on integral types.
11774 Logical @sc{and}. Defined on integral types.
11777 Bitwise @sc{or}. Defined on integral types.
11780 Bitwise exclusive-@sc{or}. Defined on integral types.
11783 Bitwise @sc{and}. Defined on integral types.
11786 Equality and inequality. Defined on scalar types. The value of these
11787 expressions is 0 for false and non-zero for true.
11789 @item <@r{, }>@r{, }<=@r{, }>=
11790 Less than, greater than, less than or equal, greater than or equal.
11791 Defined on scalar types. The value of these expressions is 0 for false
11792 and non-zero for true.
11795 left shift, and right shift. Defined on integral types.
11798 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11801 Addition and subtraction. Defined on integral types, floating-point types and
11804 @item *@r{, }/@r{, }%
11805 Multiplication, division, and modulus. Multiplication and division are
11806 defined on integral and floating-point types. Modulus is defined on
11810 Increment and decrement. When appearing before a variable, the
11811 operation is performed before the variable is used in an expression;
11812 when appearing after it, the variable's value is used before the
11813 operation takes place.
11816 Pointer dereferencing. Defined on pointer types. Same precedence as
11820 Address operator. Defined on variables. Same precedence as @code{++}.
11822 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11823 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11824 to examine the address
11825 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11829 Negative. Defined on integral and floating-point types. Same
11830 precedence as @code{++}.
11833 Logical negation. Defined on integral types. Same precedence as
11837 Bitwise complement operator. Defined on integral types. Same precedence as
11842 Structure member, and pointer-to-structure member. For convenience,
11843 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11844 pointer based on the stored type information.
11845 Defined on @code{struct} and @code{union} data.
11848 Dereferences of pointers to members.
11851 Array indexing. @code{@var{a}[@var{i}]} is defined as
11852 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11855 Function parameter list. Same precedence as @code{->}.
11858 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11859 and @code{class} types.
11862 Doubled colons also represent the @value{GDBN} scope operator
11863 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11867 If an operator is redefined in the user code, @value{GDBN} usually
11868 attempts to invoke the redefined version instead of using the operator's
11869 predefined meaning.
11872 @subsubsection C and C@t{++} Constants
11874 @cindex C and C@t{++} constants
11876 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11881 Integer constants are a sequence of digits. Octal constants are
11882 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11883 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11884 @samp{l}, specifying that the constant should be treated as a
11888 Floating point constants are a sequence of digits, followed by a decimal
11889 point, followed by a sequence of digits, and optionally followed by an
11890 exponent. An exponent is of the form:
11891 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11892 sequence of digits. The @samp{+} is optional for positive exponents.
11893 A floating-point constant may also end with a letter @samp{f} or
11894 @samp{F}, specifying that the constant should be treated as being of
11895 the @code{float} (as opposed to the default @code{double}) type; or with
11896 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11900 Enumerated constants consist of enumerated identifiers, or their
11901 integral equivalents.
11904 Character constants are a single character surrounded by single quotes
11905 (@code{'}), or a number---the ordinal value of the corresponding character
11906 (usually its @sc{ascii} value). Within quotes, the single character may
11907 be represented by a letter or by @dfn{escape sequences}, which are of
11908 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11909 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11910 @samp{@var{x}} is a predefined special character---for example,
11911 @samp{\n} for newline.
11914 String constants are a sequence of character constants surrounded by
11915 double quotes (@code{"}). Any valid character constant (as described
11916 above) may appear. Double quotes within the string must be preceded by
11917 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11921 Pointer constants are an integral value. You can also write pointers
11922 to constants using the C operator @samp{&}.
11925 Array constants are comma-separated lists surrounded by braces @samp{@{}
11926 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11927 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11928 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11931 @node C Plus Plus Expressions
11932 @subsubsection C@t{++} Expressions
11934 @cindex expressions in C@t{++}
11935 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11937 @cindex debugging C@t{++} programs
11938 @cindex C@t{++} compilers
11939 @cindex debug formats and C@t{++}
11940 @cindex @value{NGCC} and C@t{++}
11942 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11943 proper compiler and the proper debug format. Currently, @value{GDBN}
11944 works best when debugging C@t{++} code that is compiled with
11945 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11946 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11947 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11948 stabs+ as their default debug format, so you usually don't need to
11949 specify a debug format explicitly. Other compilers and/or debug formats
11950 are likely to work badly or not at all when using @value{GDBN} to debug
11956 @cindex member functions
11958 Member function calls are allowed; you can use expressions like
11961 count = aml->GetOriginal(x, y)
11964 @vindex this@r{, inside C@t{++} member functions}
11965 @cindex namespace in C@t{++}
11967 While a member function is active (in the selected stack frame), your
11968 expressions have the same namespace available as the member function;
11969 that is, @value{GDBN} allows implicit references to the class instance
11970 pointer @code{this} following the same rules as C@t{++}.
11972 @cindex call overloaded functions
11973 @cindex overloaded functions, calling
11974 @cindex type conversions in C@t{++}
11976 You can call overloaded functions; @value{GDBN} resolves the function
11977 call to the right definition, with some restrictions. @value{GDBN} does not
11978 perform overload resolution involving user-defined type conversions,
11979 calls to constructors, or instantiations of templates that do not exist
11980 in the program. It also cannot handle ellipsis argument lists or
11983 It does perform integral conversions and promotions, floating-point
11984 promotions, arithmetic conversions, pointer conversions, conversions of
11985 class objects to base classes, and standard conversions such as those of
11986 functions or arrays to pointers; it requires an exact match on the
11987 number of function arguments.
11989 Overload resolution is always performed, unless you have specified
11990 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11991 ,@value{GDBN} Features for C@t{++}}.
11993 You must specify @code{set overload-resolution off} in order to use an
11994 explicit function signature to call an overloaded function, as in
11996 p 'foo(char,int)'('x', 13)
11999 The @value{GDBN} command-completion facility can simplify this;
12000 see @ref{Completion, ,Command Completion}.
12002 @cindex reference declarations
12004 @value{GDBN} understands variables declared as C@t{++} references; you can use
12005 them in expressions just as you do in C@t{++} source---they are automatically
12008 In the parameter list shown when @value{GDBN} displays a frame, the values of
12009 reference variables are not displayed (unlike other variables); this
12010 avoids clutter, since references are often used for large structures.
12011 The @emph{address} of a reference variable is always shown, unless
12012 you have specified @samp{set print address off}.
12015 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12016 expressions can use it just as expressions in your program do. Since
12017 one scope may be defined in another, you can use @code{::} repeatedly if
12018 necessary, for example in an expression like
12019 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12020 resolving name scope by reference to source files, in both C and C@t{++}
12021 debugging (@pxref{Variables, ,Program Variables}).
12024 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12025 calling virtual functions correctly, printing out virtual bases of
12026 objects, calling functions in a base subobject, casting objects, and
12027 invoking user-defined operators.
12030 @subsubsection C and C@t{++} Defaults
12032 @cindex C and C@t{++} defaults
12034 If you allow @value{GDBN} to set type and range checking automatically, they
12035 both default to @code{off} whenever the working language changes to
12036 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12037 selects the working language.
12039 If you allow @value{GDBN} to set the language automatically, it
12040 recognizes source files whose names end with @file{.c}, @file{.C}, or
12041 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12042 these files, it sets the working language to C or C@t{++}.
12043 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12044 for further details.
12046 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12047 @c unimplemented. If (b) changes, it might make sense to let this node
12048 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12051 @subsubsection C and C@t{++} Type and Range Checks
12053 @cindex C and C@t{++} checks
12055 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12056 is not used. However, if you turn type checking on, @value{GDBN}
12057 considers two variables type equivalent if:
12061 The two variables are structured and have the same structure, union, or
12065 The two variables have the same type name, or types that have been
12066 declared equivalent through @code{typedef}.
12069 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12072 The two @code{struct}, @code{union}, or @code{enum} variables are
12073 declared in the same declaration. (Note: this may not be true for all C
12078 Range checking, if turned on, is done on mathematical operations. Array
12079 indices are not checked, since they are often used to index a pointer
12080 that is not itself an array.
12083 @subsubsection @value{GDBN} and C
12085 The @code{set print union} and @code{show print union} commands apply to
12086 the @code{union} type. When set to @samp{on}, any @code{union} that is
12087 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12088 appears as @samp{@{...@}}.
12090 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12091 with pointers and a memory allocation function. @xref{Expressions,
12094 @node Debugging C Plus Plus
12095 @subsubsection @value{GDBN} Features for C@t{++}
12097 @cindex commands for C@t{++}
12099 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12100 designed specifically for use with C@t{++}. Here is a summary:
12103 @cindex break in overloaded functions
12104 @item @r{breakpoint menus}
12105 When you want a breakpoint in a function whose name is overloaded,
12106 @value{GDBN} has the capability to display a menu of possible breakpoint
12107 locations to help you specify which function definition you want.
12108 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12110 @cindex overloading in C@t{++}
12111 @item rbreak @var{regex}
12112 Setting breakpoints using regular expressions is helpful for setting
12113 breakpoints on overloaded functions that are not members of any special
12115 @xref{Set Breaks, ,Setting Breakpoints}.
12117 @cindex C@t{++} exception handling
12120 Debug C@t{++} exception handling using these commands. @xref{Set
12121 Catchpoints, , Setting Catchpoints}.
12123 @cindex inheritance
12124 @item ptype @var{typename}
12125 Print inheritance relationships as well as other information for type
12127 @xref{Symbols, ,Examining the Symbol Table}.
12129 @cindex C@t{++} symbol display
12130 @item set print demangle
12131 @itemx show print demangle
12132 @itemx set print asm-demangle
12133 @itemx show print asm-demangle
12134 Control whether C@t{++} symbols display in their source form, both when
12135 displaying code as C@t{++} source and when displaying disassemblies.
12136 @xref{Print Settings, ,Print Settings}.
12138 @item set print object
12139 @itemx show print object
12140 Choose whether to print derived (actual) or declared types of objects.
12141 @xref{Print Settings, ,Print Settings}.
12143 @item set print vtbl
12144 @itemx show print vtbl
12145 Control the format for printing virtual function tables.
12146 @xref{Print Settings, ,Print Settings}.
12147 (The @code{vtbl} commands do not work on programs compiled with the HP
12148 ANSI C@t{++} compiler (@code{aCC}).)
12150 @kindex set overload-resolution
12151 @cindex overloaded functions, overload resolution
12152 @item set overload-resolution on
12153 Enable overload resolution for C@t{++} expression evaluation. The default
12154 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12155 and searches for a function whose signature matches the argument types,
12156 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12157 Expressions, ,C@t{++} Expressions}, for details).
12158 If it cannot find a match, it emits a message.
12160 @item set overload-resolution off
12161 Disable overload resolution for C@t{++} expression evaluation. For
12162 overloaded functions that are not class member functions, @value{GDBN}
12163 chooses the first function of the specified name that it finds in the
12164 symbol table, whether or not its arguments are of the correct type. For
12165 overloaded functions that are class member functions, @value{GDBN}
12166 searches for a function whose signature @emph{exactly} matches the
12169 @kindex show overload-resolution
12170 @item show overload-resolution
12171 Show the current setting of overload resolution.
12173 @item @r{Overloaded symbol names}
12174 You can specify a particular definition of an overloaded symbol, using
12175 the same notation that is used to declare such symbols in C@t{++}: type
12176 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12177 also use the @value{GDBN} command-line word completion facilities to list the
12178 available choices, or to finish the type list for you.
12179 @xref{Completion,, Command Completion}, for details on how to do this.
12182 @node Decimal Floating Point
12183 @subsubsection Decimal Floating Point format
12184 @cindex decimal floating point format
12186 @value{GDBN} can examine, set and perform computations with numbers in
12187 decimal floating point format, which in the C language correspond to the
12188 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12189 specified by the extension to support decimal floating-point arithmetic.
12191 There are two encodings in use, depending on the architecture: BID (Binary
12192 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12193 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12196 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12197 to manipulate decimal floating point numbers, it is not possible to convert
12198 (using a cast, for example) integers wider than 32-bit to decimal float.
12200 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12201 point computations, error checking in decimal float operations ignores
12202 underflow, overflow and divide by zero exceptions.
12204 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12205 to inspect @code{_Decimal128} values stored in floating point registers.
12206 See @ref{PowerPC,,PowerPC} for more details.
12212 @value{GDBN} can be used to debug programs written in D and compiled with
12213 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12214 specific feature --- dynamic arrays.
12217 @subsection Objective-C
12219 @cindex Objective-C
12220 This section provides information about some commands and command
12221 options that are useful for debugging Objective-C code. See also
12222 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12223 few more commands specific to Objective-C support.
12226 * Method Names in Commands::
12227 * The Print Command with Objective-C::
12230 @node Method Names in Commands
12231 @subsubsection Method Names in Commands
12233 The following commands have been extended to accept Objective-C method
12234 names as line specifications:
12236 @kindex clear@r{, and Objective-C}
12237 @kindex break@r{, and Objective-C}
12238 @kindex info line@r{, and Objective-C}
12239 @kindex jump@r{, and Objective-C}
12240 @kindex list@r{, and Objective-C}
12244 @item @code{info line}
12249 A fully qualified Objective-C method name is specified as
12252 -[@var{Class} @var{methodName}]
12255 where the minus sign is used to indicate an instance method and a
12256 plus sign (not shown) is used to indicate a class method. The class
12257 name @var{Class} and method name @var{methodName} are enclosed in
12258 brackets, similar to the way messages are specified in Objective-C
12259 source code. For example, to set a breakpoint at the @code{create}
12260 instance method of class @code{Fruit} in the program currently being
12264 break -[Fruit create]
12267 To list ten program lines around the @code{initialize} class method,
12271 list +[NSText initialize]
12274 In the current version of @value{GDBN}, the plus or minus sign is
12275 required. In future versions of @value{GDBN}, the plus or minus
12276 sign will be optional, but you can use it to narrow the search. It
12277 is also possible to specify just a method name:
12283 You must specify the complete method name, including any colons. If
12284 your program's source files contain more than one @code{create} method,
12285 you'll be presented with a numbered list of classes that implement that
12286 method. Indicate your choice by number, or type @samp{0} to exit if
12289 As another example, to clear a breakpoint established at the
12290 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12293 clear -[NSWindow makeKeyAndOrderFront:]
12296 @node The Print Command with Objective-C
12297 @subsubsection The Print Command With Objective-C
12298 @cindex Objective-C, print objects
12299 @kindex print-object
12300 @kindex po @r{(@code{print-object})}
12302 The print command has also been extended to accept methods. For example:
12305 print -[@var{object} hash]
12308 @cindex print an Objective-C object description
12309 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12311 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12312 and print the result. Also, an additional command has been added,
12313 @code{print-object} or @code{po} for short, which is meant to print
12314 the description of an object. However, this command may only work
12315 with certain Objective-C libraries that have a particular hook
12316 function, @code{_NSPrintForDebugger}, defined.
12319 @subsection OpenCL C
12322 This section provides information about @value{GDBN}s OpenCL C support.
12325 * OpenCL C Datatypes::
12326 * OpenCL C Expressions::
12327 * OpenCL C Operators::
12330 @node OpenCL C Datatypes
12331 @subsubsection OpenCL C Datatypes
12333 @cindex OpenCL C Datatypes
12334 @value{GDBN} supports the builtin scalar and vector datatypes specified
12335 by OpenCL 1.1. In addition the half- and double-precision floating point
12336 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12337 extensions are also known to @value{GDBN}.
12339 @node OpenCL C Expressions
12340 @subsubsection OpenCL C Expressions
12342 @cindex OpenCL C Expressions
12343 @value{GDBN} supports accesses to vector components including the access as
12344 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12345 supported by @value{GDBN} can be used as well.
12347 @node OpenCL C Operators
12348 @subsubsection OpenCL C Operators
12350 @cindex OpenCL C Operators
12351 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12355 @subsection Fortran
12356 @cindex Fortran-specific support in @value{GDBN}
12358 @value{GDBN} can be used to debug programs written in Fortran, but it
12359 currently supports only the features of Fortran 77 language.
12361 @cindex trailing underscore, in Fortran symbols
12362 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12363 among them) append an underscore to the names of variables and
12364 functions. When you debug programs compiled by those compilers, you
12365 will need to refer to variables and functions with a trailing
12369 * Fortran Operators:: Fortran operators and expressions
12370 * Fortran Defaults:: Default settings for Fortran
12371 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12374 @node Fortran Operators
12375 @subsubsection Fortran Operators and Expressions
12377 @cindex Fortran operators and expressions
12379 Operators must be defined on values of specific types. For instance,
12380 @code{+} is defined on numbers, but not on characters or other non-
12381 arithmetic types. Operators are often defined on groups of types.
12385 The exponentiation operator. It raises the first operand to the power
12389 The range operator. Normally used in the form of array(low:high) to
12390 represent a section of array.
12393 The access component operator. Normally used to access elements in derived
12394 types. Also suitable for unions. As unions aren't part of regular Fortran,
12395 this can only happen when accessing a register that uses a gdbarch-defined
12399 @node Fortran Defaults
12400 @subsubsection Fortran Defaults
12402 @cindex Fortran Defaults
12404 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12405 default uses case-insensitive matches for Fortran symbols. You can
12406 change that with the @samp{set case-insensitive} command, see
12407 @ref{Symbols}, for the details.
12409 @node Special Fortran Commands
12410 @subsubsection Special Fortran Commands
12412 @cindex Special Fortran commands
12414 @value{GDBN} has some commands to support Fortran-specific features,
12415 such as displaying common blocks.
12418 @cindex @code{COMMON} blocks, Fortran
12419 @kindex info common
12420 @item info common @r{[}@var{common-name}@r{]}
12421 This command prints the values contained in the Fortran @code{COMMON}
12422 block whose name is @var{common-name}. With no argument, the names of
12423 all @code{COMMON} blocks visible at the current program location are
12430 @cindex Pascal support in @value{GDBN}, limitations
12431 Debugging Pascal programs which use sets, subranges, file variables, or
12432 nested functions does not currently work. @value{GDBN} does not support
12433 entering expressions, printing values, or similar features using Pascal
12436 The Pascal-specific command @code{set print pascal_static-members}
12437 controls whether static members of Pascal objects are displayed.
12438 @xref{Print Settings, pascal_static-members}.
12441 @subsection Modula-2
12443 @cindex Modula-2, @value{GDBN} support
12445 The extensions made to @value{GDBN} to support Modula-2 only support
12446 output from the @sc{gnu} Modula-2 compiler (which is currently being
12447 developed). Other Modula-2 compilers are not currently supported, and
12448 attempting to debug executables produced by them is most likely
12449 to give an error as @value{GDBN} reads in the executable's symbol
12452 @cindex expressions in Modula-2
12454 * M2 Operators:: Built-in operators
12455 * Built-In Func/Proc:: Built-in functions and procedures
12456 * M2 Constants:: Modula-2 constants
12457 * M2 Types:: Modula-2 types
12458 * M2 Defaults:: Default settings for Modula-2
12459 * Deviations:: Deviations from standard Modula-2
12460 * M2 Checks:: Modula-2 type and range checks
12461 * M2 Scope:: The scope operators @code{::} and @code{.}
12462 * GDB/M2:: @value{GDBN} and Modula-2
12466 @subsubsection Operators
12467 @cindex Modula-2 operators
12469 Operators must be defined on values of specific types. For instance,
12470 @code{+} is defined on numbers, but not on structures. Operators are
12471 often defined on groups of types. For the purposes of Modula-2, the
12472 following definitions hold:
12477 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12481 @emph{Character types} consist of @code{CHAR} and its subranges.
12484 @emph{Floating-point types} consist of @code{REAL}.
12487 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12491 @emph{Scalar types} consist of all of the above.
12494 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12497 @emph{Boolean types} consist of @code{BOOLEAN}.
12501 The following operators are supported, and appear in order of
12502 increasing precedence:
12506 Function argument or array index separator.
12509 Assignment. The value of @var{var} @code{:=} @var{value} is
12513 Less than, greater than on integral, floating-point, or enumerated
12517 Less than or equal to, greater than or equal to
12518 on integral, floating-point and enumerated types, or set inclusion on
12519 set types. Same precedence as @code{<}.
12521 @item =@r{, }<>@r{, }#
12522 Equality and two ways of expressing inequality, valid on scalar types.
12523 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12524 available for inequality, since @code{#} conflicts with the script
12528 Set membership. Defined on set types and the types of their members.
12529 Same precedence as @code{<}.
12532 Boolean disjunction. Defined on boolean types.
12535 Boolean conjunction. Defined on boolean types.
12538 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12541 Addition and subtraction on integral and floating-point types, or union
12542 and difference on set types.
12545 Multiplication on integral and floating-point types, or set intersection
12549 Division on floating-point types, or symmetric set difference on set
12550 types. Same precedence as @code{*}.
12553 Integer division and remainder. Defined on integral types. Same
12554 precedence as @code{*}.
12557 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12560 Pointer dereferencing. Defined on pointer types.
12563 Boolean negation. Defined on boolean types. Same precedence as
12567 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12568 precedence as @code{^}.
12571 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12574 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12578 @value{GDBN} and Modula-2 scope operators.
12582 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12583 treats the use of the operator @code{IN}, or the use of operators
12584 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12585 @code{<=}, and @code{>=} on sets as an error.
12589 @node Built-In Func/Proc
12590 @subsubsection Built-in Functions and Procedures
12591 @cindex Modula-2 built-ins
12593 Modula-2 also makes available several built-in procedures and functions.
12594 In describing these, the following metavariables are used:
12599 represents an @code{ARRAY} variable.
12602 represents a @code{CHAR} constant or variable.
12605 represents a variable or constant of integral type.
12608 represents an identifier that belongs to a set. Generally used in the
12609 same function with the metavariable @var{s}. The type of @var{s} should
12610 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12613 represents a variable or constant of integral or floating-point type.
12616 represents a variable or constant of floating-point type.
12622 represents a variable.
12625 represents a variable or constant of one of many types. See the
12626 explanation of the function for details.
12629 All Modula-2 built-in procedures also return a result, described below.
12633 Returns the absolute value of @var{n}.
12636 If @var{c} is a lower case letter, it returns its upper case
12637 equivalent, otherwise it returns its argument.
12640 Returns the character whose ordinal value is @var{i}.
12643 Decrements the value in the variable @var{v} by one. Returns the new value.
12645 @item DEC(@var{v},@var{i})
12646 Decrements the value in the variable @var{v} by @var{i}. Returns the
12649 @item EXCL(@var{m},@var{s})
12650 Removes the element @var{m} from the set @var{s}. Returns the new
12653 @item FLOAT(@var{i})
12654 Returns the floating point equivalent of the integer @var{i}.
12656 @item HIGH(@var{a})
12657 Returns the index of the last member of @var{a}.
12660 Increments the value in the variable @var{v} by one. Returns the new value.
12662 @item INC(@var{v},@var{i})
12663 Increments the value in the variable @var{v} by @var{i}. Returns the
12666 @item INCL(@var{m},@var{s})
12667 Adds the element @var{m} to the set @var{s} if it is not already
12668 there. Returns the new set.
12671 Returns the maximum value of the type @var{t}.
12674 Returns the minimum value of the type @var{t}.
12677 Returns boolean TRUE if @var{i} is an odd number.
12680 Returns the ordinal value of its argument. For example, the ordinal
12681 value of a character is its @sc{ascii} value (on machines supporting the
12682 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12683 integral, character and enumerated types.
12685 @item SIZE(@var{x})
12686 Returns the size of its argument. @var{x} can be a variable or a type.
12688 @item TRUNC(@var{r})
12689 Returns the integral part of @var{r}.
12691 @item TSIZE(@var{x})
12692 Returns the size of its argument. @var{x} can be a variable or a type.
12694 @item VAL(@var{t},@var{i})
12695 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12699 @emph{Warning:} Sets and their operations are not yet supported, so
12700 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12704 @cindex Modula-2 constants
12706 @subsubsection Constants
12708 @value{GDBN} allows you to express the constants of Modula-2 in the following
12714 Integer constants are simply a sequence of digits. When used in an
12715 expression, a constant is interpreted to be type-compatible with the
12716 rest of the expression. Hexadecimal integers are specified by a
12717 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12720 Floating point constants appear as a sequence of digits, followed by a
12721 decimal point and another sequence of digits. An optional exponent can
12722 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12723 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12724 digits of the floating point constant must be valid decimal (base 10)
12728 Character constants consist of a single character enclosed by a pair of
12729 like quotes, either single (@code{'}) or double (@code{"}). They may
12730 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12731 followed by a @samp{C}.
12734 String constants consist of a sequence of characters enclosed by a
12735 pair of like quotes, either single (@code{'}) or double (@code{"}).
12736 Escape sequences in the style of C are also allowed. @xref{C
12737 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12741 Enumerated constants consist of an enumerated identifier.
12744 Boolean constants consist of the identifiers @code{TRUE} and
12748 Pointer constants consist of integral values only.
12751 Set constants are not yet supported.
12755 @subsubsection Modula-2 Types
12756 @cindex Modula-2 types
12758 Currently @value{GDBN} can print the following data types in Modula-2
12759 syntax: array types, record types, set types, pointer types, procedure
12760 types, enumerated types, subrange types and base types. You can also
12761 print the contents of variables declared using these type.
12762 This section gives a number of simple source code examples together with
12763 sample @value{GDBN} sessions.
12765 The first example contains the following section of code:
12774 and you can request @value{GDBN} to interrogate the type and value of
12775 @code{r} and @code{s}.
12778 (@value{GDBP}) print s
12780 (@value{GDBP}) ptype s
12782 (@value{GDBP}) print r
12784 (@value{GDBP}) ptype r
12789 Likewise if your source code declares @code{s} as:
12793 s: SET ['A'..'Z'] ;
12797 then you may query the type of @code{s} by:
12800 (@value{GDBP}) ptype s
12801 type = SET ['A'..'Z']
12805 Note that at present you cannot interactively manipulate set
12806 expressions using the debugger.
12808 The following example shows how you might declare an array in Modula-2
12809 and how you can interact with @value{GDBN} to print its type and contents:
12813 s: ARRAY [-10..10] OF CHAR ;
12817 (@value{GDBP}) ptype s
12818 ARRAY [-10..10] OF CHAR
12821 Note that the array handling is not yet complete and although the type
12822 is printed correctly, expression handling still assumes that all
12823 arrays have a lower bound of zero and not @code{-10} as in the example
12826 Here are some more type related Modula-2 examples:
12830 colour = (blue, red, yellow, green) ;
12831 t = [blue..yellow] ;
12839 The @value{GDBN} interaction shows how you can query the data type
12840 and value of a variable.
12843 (@value{GDBP}) print s
12845 (@value{GDBP}) ptype t
12846 type = [blue..yellow]
12850 In this example a Modula-2 array is declared and its contents
12851 displayed. Observe that the contents are written in the same way as
12852 their @code{C} counterparts.
12856 s: ARRAY [1..5] OF CARDINAL ;
12862 (@value{GDBP}) print s
12863 $1 = @{1, 0, 0, 0, 0@}
12864 (@value{GDBP}) ptype s
12865 type = ARRAY [1..5] OF CARDINAL
12868 The Modula-2 language interface to @value{GDBN} also understands
12869 pointer types as shown in this example:
12873 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12880 and you can request that @value{GDBN} describes the type of @code{s}.
12883 (@value{GDBP}) ptype s
12884 type = POINTER TO ARRAY [1..5] OF CARDINAL
12887 @value{GDBN} handles compound types as we can see in this example.
12888 Here we combine array types, record types, pointer types and subrange
12899 myarray = ARRAY myrange OF CARDINAL ;
12900 myrange = [-2..2] ;
12902 s: POINTER TO ARRAY myrange OF foo ;
12906 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12910 (@value{GDBP}) ptype s
12911 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12914 f3 : ARRAY [-2..2] OF CARDINAL;
12919 @subsubsection Modula-2 Defaults
12920 @cindex Modula-2 defaults
12922 If type and range checking are set automatically by @value{GDBN}, they
12923 both default to @code{on} whenever the working language changes to
12924 Modula-2. This happens regardless of whether you or @value{GDBN}
12925 selected the working language.
12927 If you allow @value{GDBN} to set the language automatically, then entering
12928 code compiled from a file whose name ends with @file{.mod} sets the
12929 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12930 Infer the Source Language}, for further details.
12933 @subsubsection Deviations from Standard Modula-2
12934 @cindex Modula-2, deviations from
12936 A few changes have been made to make Modula-2 programs easier to debug.
12937 This is done primarily via loosening its type strictness:
12941 Unlike in standard Modula-2, pointer constants can be formed by
12942 integers. This allows you to modify pointer variables during
12943 debugging. (In standard Modula-2, the actual address contained in a
12944 pointer variable is hidden from you; it can only be modified
12945 through direct assignment to another pointer variable or expression that
12946 returned a pointer.)
12949 C escape sequences can be used in strings and characters to represent
12950 non-printable characters. @value{GDBN} prints out strings with these
12951 escape sequences embedded. Single non-printable characters are
12952 printed using the @samp{CHR(@var{nnn})} format.
12955 The assignment operator (@code{:=}) returns the value of its right-hand
12959 All built-in procedures both modify @emph{and} return their argument.
12963 @subsubsection Modula-2 Type and Range Checks
12964 @cindex Modula-2 checks
12967 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12970 @c FIXME remove warning when type/range checks added
12972 @value{GDBN} considers two Modula-2 variables type equivalent if:
12976 They are of types that have been declared equivalent via a @code{TYPE
12977 @var{t1} = @var{t2}} statement
12980 They have been declared on the same line. (Note: This is true of the
12981 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12984 As long as type checking is enabled, any attempt to combine variables
12985 whose types are not equivalent is an error.
12987 Range checking is done on all mathematical operations, assignment, array
12988 index bounds, and all built-in functions and procedures.
12991 @subsubsection The Scope Operators @code{::} and @code{.}
12993 @cindex @code{.}, Modula-2 scope operator
12994 @cindex colon, doubled as scope operator
12996 @vindex colon-colon@r{, in Modula-2}
12997 @c Info cannot handle :: but TeX can.
13000 @vindex ::@r{, in Modula-2}
13003 There are a few subtle differences between the Modula-2 scope operator
13004 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13009 @var{module} . @var{id}
13010 @var{scope} :: @var{id}
13014 where @var{scope} is the name of a module or a procedure,
13015 @var{module} the name of a module, and @var{id} is any declared
13016 identifier within your program, except another module.
13018 Using the @code{::} operator makes @value{GDBN} search the scope
13019 specified by @var{scope} for the identifier @var{id}. If it is not
13020 found in the specified scope, then @value{GDBN} searches all scopes
13021 enclosing the one specified by @var{scope}.
13023 Using the @code{.} operator makes @value{GDBN} search the current scope for
13024 the identifier specified by @var{id} that was imported from the
13025 definition module specified by @var{module}. With this operator, it is
13026 an error if the identifier @var{id} was not imported from definition
13027 module @var{module}, or if @var{id} is not an identifier in
13031 @subsubsection @value{GDBN} and Modula-2
13033 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13034 Five subcommands of @code{set print} and @code{show print} apply
13035 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13036 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13037 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13038 analogue in Modula-2.
13040 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13041 with any language, is not useful with Modula-2. Its
13042 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13043 created in Modula-2 as they can in C or C@t{++}. However, because an
13044 address can be specified by an integral constant, the construct
13045 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13047 @cindex @code{#} in Modula-2
13048 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13049 interpreted as the beginning of a comment. Use @code{<>} instead.
13055 The extensions made to @value{GDBN} for Ada only support
13056 output from the @sc{gnu} Ada (GNAT) compiler.
13057 Other Ada compilers are not currently supported, and
13058 attempting to debug executables produced by them is most likely
13062 @cindex expressions in Ada
13064 * Ada Mode Intro:: General remarks on the Ada syntax
13065 and semantics supported by Ada mode
13067 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13068 * Additions to Ada:: Extensions of the Ada expression syntax.
13069 * Stopping Before Main Program:: Debugging the program during elaboration.
13070 * Ada Tasks:: Listing and setting breakpoints in tasks.
13071 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13072 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13074 * Ada Glitches:: Known peculiarities of Ada mode.
13077 @node Ada Mode Intro
13078 @subsubsection Introduction
13079 @cindex Ada mode, general
13081 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13082 syntax, with some extensions.
13083 The philosophy behind the design of this subset is
13087 That @value{GDBN} should provide basic literals and access to operations for
13088 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13089 leaving more sophisticated computations to subprograms written into the
13090 program (which therefore may be called from @value{GDBN}).
13093 That type safety and strict adherence to Ada language restrictions
13094 are not particularly important to the @value{GDBN} user.
13097 That brevity is important to the @value{GDBN} user.
13100 Thus, for brevity, the debugger acts as if all names declared in
13101 user-written packages are directly visible, even if they are not visible
13102 according to Ada rules, thus making it unnecessary to fully qualify most
13103 names with their packages, regardless of context. Where this causes
13104 ambiguity, @value{GDBN} asks the user's intent.
13106 The debugger will start in Ada mode if it detects an Ada main program.
13107 As for other languages, it will enter Ada mode when stopped in a program that
13108 was translated from an Ada source file.
13110 While in Ada mode, you may use `@t{--}' for comments. This is useful
13111 mostly for documenting command files. The standard @value{GDBN} comment
13112 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13113 middle (to allow based literals).
13115 The debugger supports limited overloading. Given a subprogram call in which
13116 the function symbol has multiple definitions, it will use the number of
13117 actual parameters and some information about their types to attempt to narrow
13118 the set of definitions. It also makes very limited use of context, preferring
13119 procedures to functions in the context of the @code{call} command, and
13120 functions to procedures elsewhere.
13122 @node Omissions from Ada
13123 @subsubsection Omissions from Ada
13124 @cindex Ada, omissions from
13126 Here are the notable omissions from the subset:
13130 Only a subset of the attributes are supported:
13134 @t{'First}, @t{'Last}, and @t{'Length}
13135 on array objects (not on types and subtypes).
13138 @t{'Min} and @t{'Max}.
13141 @t{'Pos} and @t{'Val}.
13147 @t{'Range} on array objects (not subtypes), but only as the right
13148 operand of the membership (@code{in}) operator.
13151 @t{'Access}, @t{'Unchecked_Access}, and
13152 @t{'Unrestricted_Access} (a GNAT extension).
13160 @code{Characters.Latin_1} are not available and
13161 concatenation is not implemented. Thus, escape characters in strings are
13162 not currently available.
13165 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13166 equality of representations. They will generally work correctly
13167 for strings and arrays whose elements have integer or enumeration types.
13168 They may not work correctly for arrays whose element
13169 types have user-defined equality, for arrays of real values
13170 (in particular, IEEE-conformant floating point, because of negative
13171 zeroes and NaNs), and for arrays whose elements contain unused bits with
13172 indeterminate values.
13175 The other component-by-component array operations (@code{and}, @code{or},
13176 @code{xor}, @code{not}, and relational tests other than equality)
13177 are not implemented.
13180 @cindex array aggregates (Ada)
13181 @cindex record aggregates (Ada)
13182 @cindex aggregates (Ada)
13183 There is limited support for array and record aggregates. They are
13184 permitted only on the right sides of assignments, as in these examples:
13187 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13188 (@value{GDBP}) set An_Array := (1, others => 0)
13189 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13190 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13191 (@value{GDBP}) set A_Record := (1, "Peter", True);
13192 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13196 discriminant's value by assigning an aggregate has an
13197 undefined effect if that discriminant is used within the record.
13198 However, you can first modify discriminants by directly assigning to
13199 them (which normally would not be allowed in Ada), and then performing an
13200 aggregate assignment. For example, given a variable @code{A_Rec}
13201 declared to have a type such as:
13204 type Rec (Len : Small_Integer := 0) is record
13206 Vals : IntArray (1 .. Len);
13210 you can assign a value with a different size of @code{Vals} with two
13214 (@value{GDBP}) set A_Rec.Len := 4
13215 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13218 As this example also illustrates, @value{GDBN} is very loose about the usual
13219 rules concerning aggregates. You may leave out some of the
13220 components of an array or record aggregate (such as the @code{Len}
13221 component in the assignment to @code{A_Rec} above); they will retain their
13222 original values upon assignment. You may freely use dynamic values as
13223 indices in component associations. You may even use overlapping or
13224 redundant component associations, although which component values are
13225 assigned in such cases is not defined.
13228 Calls to dispatching subprograms are not implemented.
13231 The overloading algorithm is much more limited (i.e., less selective)
13232 than that of real Ada. It makes only limited use of the context in
13233 which a subexpression appears to resolve its meaning, and it is much
13234 looser in its rules for allowing type matches. As a result, some
13235 function calls will be ambiguous, and the user will be asked to choose
13236 the proper resolution.
13239 The @code{new} operator is not implemented.
13242 Entry calls are not implemented.
13245 Aside from printing, arithmetic operations on the native VAX floating-point
13246 formats are not supported.
13249 It is not possible to slice a packed array.
13252 The names @code{True} and @code{False}, when not part of a qualified name,
13253 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13255 Should your program
13256 redefine these names in a package or procedure (at best a dubious practice),
13257 you will have to use fully qualified names to access their new definitions.
13260 @node Additions to Ada
13261 @subsubsection Additions to Ada
13262 @cindex Ada, deviations from
13264 As it does for other languages, @value{GDBN} makes certain generic
13265 extensions to Ada (@pxref{Expressions}):
13269 If the expression @var{E} is a variable residing in memory (typically
13270 a local variable or array element) and @var{N} is a positive integer,
13271 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13272 @var{N}-1 adjacent variables following it in memory as an array. In
13273 Ada, this operator is generally not necessary, since its prime use is
13274 in displaying parts of an array, and slicing will usually do this in
13275 Ada. However, there are occasional uses when debugging programs in
13276 which certain debugging information has been optimized away.
13279 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13280 appears in function or file @var{B}.'' When @var{B} is a file name,
13281 you must typically surround it in single quotes.
13284 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13285 @var{type} that appears at address @var{addr}.''
13288 A name starting with @samp{$} is a convenience variable
13289 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13292 In addition, @value{GDBN} provides a few other shortcuts and outright
13293 additions specific to Ada:
13297 The assignment statement is allowed as an expression, returning
13298 its right-hand operand as its value. Thus, you may enter
13301 (@value{GDBP}) set x := y + 3
13302 (@value{GDBP}) print A(tmp := y + 1)
13306 The semicolon is allowed as an ``operator,'' returning as its value
13307 the value of its right-hand operand.
13308 This allows, for example,
13309 complex conditional breaks:
13312 (@value{GDBP}) break f
13313 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13317 Rather than use catenation and symbolic character names to introduce special
13318 characters into strings, one may instead use a special bracket notation,
13319 which is also used to print strings. A sequence of characters of the form
13320 @samp{["@var{XX}"]} within a string or character literal denotes the
13321 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13322 sequence of characters @samp{["""]} also denotes a single quotation mark
13323 in strings. For example,
13325 "One line.["0a"]Next line.["0a"]"
13328 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13332 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13333 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13337 (@value{GDBP}) print 'max(x, y)
13341 When printing arrays, @value{GDBN} uses positional notation when the
13342 array has a lower bound of 1, and uses a modified named notation otherwise.
13343 For example, a one-dimensional array of three integers with a lower bound
13344 of 3 might print as
13351 That is, in contrast to valid Ada, only the first component has a @code{=>}
13355 You may abbreviate attributes in expressions with any unique,
13356 multi-character subsequence of
13357 their names (an exact match gets preference).
13358 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13359 in place of @t{a'length}.
13362 @cindex quoting Ada internal identifiers
13363 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13364 to lower case. The GNAT compiler uses upper-case characters for
13365 some of its internal identifiers, which are normally of no interest to users.
13366 For the rare occasions when you actually have to look at them,
13367 enclose them in angle brackets to avoid the lower-case mapping.
13370 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13374 Printing an object of class-wide type or dereferencing an
13375 access-to-class-wide value will display all the components of the object's
13376 specific type (as indicated by its run-time tag). Likewise, component
13377 selection on such a value will operate on the specific type of the
13382 @node Stopping Before Main Program
13383 @subsubsection Stopping at the Very Beginning
13385 @cindex breakpointing Ada elaboration code
13386 It is sometimes necessary to debug the program during elaboration, and
13387 before reaching the main procedure.
13388 As defined in the Ada Reference
13389 Manual, the elaboration code is invoked from a procedure called
13390 @code{adainit}. To run your program up to the beginning of
13391 elaboration, simply use the following two commands:
13392 @code{tbreak adainit} and @code{run}.
13395 @subsubsection Extensions for Ada Tasks
13396 @cindex Ada, tasking
13398 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13399 @value{GDBN} provides the following task-related commands:
13404 This command shows a list of current Ada tasks, as in the following example:
13411 (@value{GDBP}) info tasks
13412 ID TID P-ID Pri State Name
13413 1 8088000 0 15 Child Activation Wait main_task
13414 2 80a4000 1 15 Accept Statement b
13415 3 809a800 1 15 Child Activation Wait a
13416 * 4 80ae800 3 15 Runnable c
13421 In this listing, the asterisk before the last task indicates it to be the
13422 task currently being inspected.
13426 Represents @value{GDBN}'s internal task number.
13432 The parent's task ID (@value{GDBN}'s internal task number).
13435 The base priority of the task.
13438 Current state of the task.
13442 The task has been created but has not been activated. It cannot be
13446 The task is not blocked for any reason known to Ada. (It may be waiting
13447 for a mutex, though.) It is conceptually "executing" in normal mode.
13450 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13451 that were waiting on terminate alternatives have been awakened and have
13452 terminated themselves.
13454 @item Child Activation Wait
13455 The task is waiting for created tasks to complete activation.
13457 @item Accept Statement
13458 The task is waiting on an accept or selective wait statement.
13460 @item Waiting on entry call
13461 The task is waiting on an entry call.
13463 @item Async Select Wait
13464 The task is waiting to start the abortable part of an asynchronous
13468 The task is waiting on a select statement with only a delay
13471 @item Child Termination Wait
13472 The task is sleeping having completed a master within itself, and is
13473 waiting for the tasks dependent on that master to become terminated or
13474 waiting on a terminate Phase.
13476 @item Wait Child in Term Alt
13477 The task is sleeping waiting for tasks on terminate alternatives to
13478 finish terminating.
13480 @item Accepting RV with @var{taskno}
13481 The task is accepting a rendez-vous with the task @var{taskno}.
13485 Name of the task in the program.
13489 @kindex info task @var{taskno}
13490 @item info task @var{taskno}
13491 This command shows detailled informations on the specified task, as in
13492 the following example:
13497 (@value{GDBP}) info tasks
13498 ID TID P-ID Pri State Name
13499 1 8077880 0 15 Child Activation Wait main_task
13500 * 2 807c468 1 15 Runnable task_1
13501 (@value{GDBP}) info task 2
13502 Ada Task: 0x807c468
13505 Parent: 1 (main_task)
13511 @kindex task@r{ (Ada)}
13512 @cindex current Ada task ID
13513 This command prints the ID of the current task.
13519 (@value{GDBP}) info tasks
13520 ID TID P-ID Pri State Name
13521 1 8077870 0 15 Child Activation Wait main_task
13522 * 2 807c458 1 15 Runnable t
13523 (@value{GDBP}) task
13524 [Current task is 2]
13527 @item task @var{taskno}
13528 @cindex Ada task switching
13529 This command is like the @code{thread @var{threadno}}
13530 command (@pxref{Threads}). It switches the context of debugging
13531 from the current task to the given task.
13537 (@value{GDBP}) info tasks
13538 ID TID P-ID Pri State Name
13539 1 8077870 0 15 Child Activation Wait main_task
13540 * 2 807c458 1 15 Runnable t
13541 (@value{GDBP}) task 1
13542 [Switching to task 1]
13543 #0 0x8067726 in pthread_cond_wait ()
13545 #0 0x8067726 in pthread_cond_wait ()
13546 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13547 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13548 #3 0x806153e in system.tasking.stages.activate_tasks ()
13549 #4 0x804aacc in un () at un.adb:5
13552 @item break @var{linespec} task @var{taskno}
13553 @itemx break @var{linespec} task @var{taskno} if @dots{}
13554 @cindex breakpoints and tasks, in Ada
13555 @cindex task breakpoints, in Ada
13556 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13557 These commands are like the @code{break @dots{} thread @dots{}}
13558 command (@pxref{Thread Stops}).
13559 @var{linespec} specifies source lines, as described
13560 in @ref{Specify Location}.
13562 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13563 to specify that you only want @value{GDBN} to stop the program when a
13564 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13565 numeric task identifiers assigned by @value{GDBN}, shown in the first
13566 column of the @samp{info tasks} display.
13568 If you do not specify @samp{task @var{taskno}} when you set a
13569 breakpoint, the breakpoint applies to @emph{all} tasks of your
13572 You can use the @code{task} qualifier on conditional breakpoints as
13573 well; in this case, place @samp{task @var{taskno}} before the
13574 breakpoint condition (before the @code{if}).
13582 (@value{GDBP}) info tasks
13583 ID TID P-ID Pri State Name
13584 1 140022020 0 15 Child Activation Wait main_task
13585 2 140045060 1 15 Accept/Select Wait t2
13586 3 140044840 1 15 Runnable t1
13587 * 4 140056040 1 15 Runnable t3
13588 (@value{GDBP}) b 15 task 2
13589 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13590 (@value{GDBP}) cont
13595 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13597 (@value{GDBP}) info tasks
13598 ID TID P-ID Pri State Name
13599 1 140022020 0 15 Child Activation Wait main_task
13600 * 2 140045060 1 15 Runnable t2
13601 3 140044840 1 15 Runnable t1
13602 4 140056040 1 15 Delay Sleep t3
13606 @node Ada Tasks and Core Files
13607 @subsubsection Tasking Support when Debugging Core Files
13608 @cindex Ada tasking and core file debugging
13610 When inspecting a core file, as opposed to debugging a live program,
13611 tasking support may be limited or even unavailable, depending on
13612 the platform being used.
13613 For instance, on x86-linux, the list of tasks is available, but task
13614 switching is not supported. On Tru64, however, task switching will work
13617 On certain platforms, including Tru64, the debugger needs to perform some
13618 memory writes in order to provide Ada tasking support. When inspecting
13619 a core file, this means that the core file must be opened with read-write
13620 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13621 Under these circumstances, you should make a backup copy of the core
13622 file before inspecting it with @value{GDBN}.
13624 @node Ravenscar Profile
13625 @subsubsection Tasking Support when using the Ravenscar Profile
13626 @cindex Ravenscar Profile
13628 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13629 specifically designed for systems with safety-critical real-time
13633 @kindex set ravenscar task-switching on
13634 @cindex task switching with program using Ravenscar Profile
13635 @item set ravenscar task-switching on
13636 Allows task switching when debugging a program that uses the Ravenscar
13637 Profile. This is the default.
13639 @kindex set ravenscar task-switching off
13640 @item set ravenscar task-switching off
13641 Turn off task switching when debugging a program that uses the Ravenscar
13642 Profile. This is mostly intended to disable the code that adds support
13643 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13644 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13645 To be effective, this command should be run before the program is started.
13647 @kindex show ravenscar task-switching
13648 @item show ravenscar task-switching
13649 Show whether it is possible to switch from task to task in a program
13650 using the Ravenscar Profile.
13655 @subsubsection Known Peculiarities of Ada Mode
13656 @cindex Ada, problems
13658 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13659 we know of several problems with and limitations of Ada mode in
13661 some of which will be fixed with planned future releases of the debugger
13662 and the GNU Ada compiler.
13666 Static constants that the compiler chooses not to materialize as objects in
13667 storage are invisible to the debugger.
13670 Named parameter associations in function argument lists are ignored (the
13671 argument lists are treated as positional).
13674 Many useful library packages are currently invisible to the debugger.
13677 Fixed-point arithmetic, conversions, input, and output is carried out using
13678 floating-point arithmetic, and may give results that only approximate those on
13682 The GNAT compiler never generates the prefix @code{Standard} for any of
13683 the standard symbols defined by the Ada language. @value{GDBN} knows about
13684 this: it will strip the prefix from names when you use it, and will never
13685 look for a name you have so qualified among local symbols, nor match against
13686 symbols in other packages or subprograms. If you have
13687 defined entities anywhere in your program other than parameters and
13688 local variables whose simple names match names in @code{Standard},
13689 GNAT's lack of qualification here can cause confusion. When this happens,
13690 you can usually resolve the confusion
13691 by qualifying the problematic names with package
13692 @code{Standard} explicitly.
13695 Older versions of the compiler sometimes generate erroneous debugging
13696 information, resulting in the debugger incorrectly printing the value
13697 of affected entities. In some cases, the debugger is able to work
13698 around an issue automatically. In other cases, the debugger is able
13699 to work around the issue, but the work-around has to be specifically
13702 @kindex set ada trust-PAD-over-XVS
13703 @kindex show ada trust-PAD-over-XVS
13706 @item set ada trust-PAD-over-XVS on
13707 Configure GDB to strictly follow the GNAT encoding when computing the
13708 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13709 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13710 a complete description of the encoding used by the GNAT compiler).
13711 This is the default.
13713 @item set ada trust-PAD-over-XVS off
13714 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13715 sometimes prints the wrong value for certain entities, changing @code{ada
13716 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13717 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13718 @code{off}, but this incurs a slight performance penalty, so it is
13719 recommended to leave this setting to @code{on} unless necessary.
13723 @node Unsupported Languages
13724 @section Unsupported Languages
13726 @cindex unsupported languages
13727 @cindex minimal language
13728 In addition to the other fully-supported programming languages,
13729 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13730 It does not represent a real programming language, but provides a set
13731 of capabilities close to what the C or assembly languages provide.
13732 This should allow most simple operations to be performed while debugging
13733 an application that uses a language currently not supported by @value{GDBN}.
13735 If the language is set to @code{auto}, @value{GDBN} will automatically
13736 select this language if the current frame corresponds to an unsupported
13740 @chapter Examining the Symbol Table
13742 The commands described in this chapter allow you to inquire about the
13743 symbols (names of variables, functions and types) defined in your
13744 program. This information is inherent in the text of your program and
13745 does not change as your program executes. @value{GDBN} finds it in your
13746 program's symbol table, in the file indicated when you started @value{GDBN}
13747 (@pxref{File Options, ,Choosing Files}), or by one of the
13748 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13750 @cindex symbol names
13751 @cindex names of symbols
13752 @cindex quoting names
13753 Occasionally, you may need to refer to symbols that contain unusual
13754 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13755 most frequent case is in referring to static variables in other
13756 source files (@pxref{Variables,,Program Variables}). File names
13757 are recorded in object files as debugging symbols, but @value{GDBN} would
13758 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13759 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13760 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13767 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13770 @cindex case-insensitive symbol names
13771 @cindex case sensitivity in symbol names
13772 @kindex set case-sensitive
13773 @item set case-sensitive on
13774 @itemx set case-sensitive off
13775 @itemx set case-sensitive auto
13776 Normally, when @value{GDBN} looks up symbols, it matches their names
13777 with case sensitivity determined by the current source language.
13778 Occasionally, you may wish to control that. The command @code{set
13779 case-sensitive} lets you do that by specifying @code{on} for
13780 case-sensitive matches or @code{off} for case-insensitive ones. If
13781 you specify @code{auto}, case sensitivity is reset to the default
13782 suitable for the source language. The default is case-sensitive
13783 matches for all languages except for Fortran, for which the default is
13784 case-insensitive matches.
13786 @kindex show case-sensitive
13787 @item show case-sensitive
13788 This command shows the current setting of case sensitivity for symbols
13791 @kindex info address
13792 @cindex address of a symbol
13793 @item info address @var{symbol}
13794 Describe where the data for @var{symbol} is stored. For a register
13795 variable, this says which register it is kept in. For a non-register
13796 local variable, this prints the stack-frame offset at which the variable
13799 Note the contrast with @samp{print &@var{symbol}}, which does not work
13800 at all for a register variable, and for a stack local variable prints
13801 the exact address of the current instantiation of the variable.
13803 @kindex info symbol
13804 @cindex symbol from address
13805 @cindex closest symbol and offset for an address
13806 @item info symbol @var{addr}
13807 Print the name of a symbol which is stored at the address @var{addr}.
13808 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13809 nearest symbol and an offset from it:
13812 (@value{GDBP}) info symbol 0x54320
13813 _initialize_vx + 396 in section .text
13817 This is the opposite of the @code{info address} command. You can use
13818 it to find out the name of a variable or a function given its address.
13820 For dynamically linked executables, the name of executable or shared
13821 library containing the symbol is also printed:
13824 (@value{GDBP}) info symbol 0x400225
13825 _start + 5 in section .text of /tmp/a.out
13826 (@value{GDBP}) info symbol 0x2aaaac2811cf
13827 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13831 @item whatis [@var{arg}]
13832 Print the data type of @var{arg}, which can be either an expression or
13833 a data type. With no argument, print the data type of @code{$}, the
13834 last value in the value history. If @var{arg} is an expression, it is
13835 not actually evaluated, and any side-effecting operations (such as
13836 assignments or function calls) inside it do not take place. If
13837 @var{arg} is a type name, it may be the name of a type or typedef, or
13838 for C code it may have the form @samp{class @var{class-name}},
13839 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13840 @samp{enum @var{enum-tag}}.
13841 @xref{Expressions, ,Expressions}.
13844 @item ptype [@var{arg}]
13845 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13846 detailed description of the type, instead of just the name of the type.
13847 @xref{Expressions, ,Expressions}.
13849 For example, for this variable declaration:
13852 struct complex @{double real; double imag;@} v;
13856 the two commands give this output:
13860 (@value{GDBP}) whatis v
13861 type = struct complex
13862 (@value{GDBP}) ptype v
13863 type = struct complex @{
13871 As with @code{whatis}, using @code{ptype} without an argument refers to
13872 the type of @code{$}, the last value in the value history.
13874 @cindex incomplete type
13875 Sometimes, programs use opaque data types or incomplete specifications
13876 of complex data structure. If the debug information included in the
13877 program does not allow @value{GDBN} to display a full declaration of
13878 the data type, it will say @samp{<incomplete type>}. For example,
13879 given these declarations:
13883 struct foo *fooptr;
13887 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13890 (@value{GDBP}) ptype foo
13891 $1 = <incomplete type>
13895 ``Incomplete type'' is C terminology for data types that are not
13896 completely specified.
13899 @item info types @var{regexp}
13901 Print a brief description of all types whose names match the regular
13902 expression @var{regexp} (or all types in your program, if you supply
13903 no argument). Each complete typename is matched as though it were a
13904 complete line; thus, @samp{i type value} gives information on all
13905 types in your program whose names include the string @code{value}, but
13906 @samp{i type ^value$} gives information only on types whose complete
13907 name is @code{value}.
13909 This command differs from @code{ptype} in two ways: first, like
13910 @code{whatis}, it does not print a detailed description; second, it
13911 lists all source files where a type is defined.
13914 @cindex local variables
13915 @item info scope @var{location}
13916 List all the variables local to a particular scope. This command
13917 accepts a @var{location} argument---a function name, a source line, or
13918 an address preceded by a @samp{*}, and prints all the variables local
13919 to the scope defined by that location. (@xref{Specify Location}, for
13920 details about supported forms of @var{location}.) For example:
13923 (@value{GDBP}) @b{info scope command_line_handler}
13924 Scope for command_line_handler:
13925 Symbol rl is an argument at stack/frame offset 8, length 4.
13926 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13927 Symbol linelength is in static storage at address 0x150a1c, length 4.
13928 Symbol p is a local variable in register $esi, length 4.
13929 Symbol p1 is a local variable in register $ebx, length 4.
13930 Symbol nline is a local variable in register $edx, length 4.
13931 Symbol repeat is a local variable at frame offset -8, length 4.
13935 This command is especially useful for determining what data to collect
13936 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13939 @kindex info source
13941 Show information about the current source file---that is, the source file for
13942 the function containing the current point of execution:
13945 the name of the source file, and the directory containing it,
13947 the directory it was compiled in,
13949 its length, in lines,
13951 which programming language it is written in,
13953 whether the executable includes debugging information for that file, and
13954 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13956 whether the debugging information includes information about
13957 preprocessor macros.
13961 @kindex info sources
13963 Print the names of all source files in your program for which there is
13964 debugging information, organized into two lists: files whose symbols
13965 have already been read, and files whose symbols will be read when needed.
13967 @kindex info functions
13968 @item info functions
13969 Print the names and data types of all defined functions.
13971 @item info functions @var{regexp}
13972 Print the names and data types of all defined functions
13973 whose names contain a match for regular expression @var{regexp}.
13974 Thus, @samp{info fun step} finds all functions whose names
13975 include @code{step}; @samp{info fun ^step} finds those whose names
13976 start with @code{step}. If a function name contains characters
13977 that conflict with the regular expression language (e.g.@:
13978 @samp{operator*()}), they may be quoted with a backslash.
13980 @kindex info variables
13981 @item info variables
13982 Print the names and data types of all variables that are defined
13983 outside of functions (i.e.@: excluding local variables).
13985 @item info variables @var{regexp}
13986 Print the names and data types of all variables (except for local
13987 variables) whose names contain a match for regular expression
13990 @kindex info classes
13991 @cindex Objective-C, classes and selectors
13993 @itemx info classes @var{regexp}
13994 Display all Objective-C classes in your program, or
13995 (with the @var{regexp} argument) all those matching a particular regular
13998 @kindex info selectors
13999 @item info selectors
14000 @itemx info selectors @var{regexp}
14001 Display all Objective-C selectors in your program, or
14002 (with the @var{regexp} argument) all those matching a particular regular
14006 This was never implemented.
14007 @kindex info methods
14009 @itemx info methods @var{regexp}
14010 The @code{info methods} command permits the user to examine all defined
14011 methods within C@t{++} program, or (with the @var{regexp} argument) a
14012 specific set of methods found in the various C@t{++} classes. Many
14013 C@t{++} classes provide a large number of methods. Thus, the output
14014 from the @code{ptype} command can be overwhelming and hard to use. The
14015 @code{info-methods} command filters the methods, printing only those
14016 which match the regular-expression @var{regexp}.
14019 @cindex reloading symbols
14020 Some systems allow individual object files that make up your program to
14021 be replaced without stopping and restarting your program. For example,
14022 in VxWorks you can simply recompile a defective object file and keep on
14023 running. If you are running on one of these systems, you can allow
14024 @value{GDBN} to reload the symbols for automatically relinked modules:
14027 @kindex set symbol-reloading
14028 @item set symbol-reloading on
14029 Replace symbol definitions for the corresponding source file when an
14030 object file with a particular name is seen again.
14032 @item set symbol-reloading off
14033 Do not replace symbol definitions when encountering object files of the
14034 same name more than once. This is the default state; if you are not
14035 running on a system that permits automatic relinking of modules, you
14036 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14037 may discard symbols when linking large programs, that may contain
14038 several modules (from different directories or libraries) with the same
14041 @kindex show symbol-reloading
14042 @item show symbol-reloading
14043 Show the current @code{on} or @code{off} setting.
14046 @cindex opaque data types
14047 @kindex set opaque-type-resolution
14048 @item set opaque-type-resolution on
14049 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14050 declared as a pointer to a @code{struct}, @code{class}, or
14051 @code{union}---for example, @code{struct MyType *}---that is used in one
14052 source file although the full declaration of @code{struct MyType} is in
14053 another source file. The default is on.
14055 A change in the setting of this subcommand will not take effect until
14056 the next time symbols for a file are loaded.
14058 @item set opaque-type-resolution off
14059 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14060 is printed as follows:
14062 @{<no data fields>@}
14065 @kindex show opaque-type-resolution
14066 @item show opaque-type-resolution
14067 Show whether opaque types are resolved or not.
14069 @kindex maint print symbols
14070 @cindex symbol dump
14071 @kindex maint print psymbols
14072 @cindex partial symbol dump
14073 @item maint print symbols @var{filename}
14074 @itemx maint print psymbols @var{filename}
14075 @itemx maint print msymbols @var{filename}
14076 Write a dump of debugging symbol data into the file @var{filename}.
14077 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14078 symbols with debugging data are included. If you use @samp{maint print
14079 symbols}, @value{GDBN} includes all the symbols for which it has already
14080 collected full details: that is, @var{filename} reflects symbols for
14081 only those files whose symbols @value{GDBN} has read. You can use the
14082 command @code{info sources} to find out which files these are. If you
14083 use @samp{maint print psymbols} instead, the dump shows information about
14084 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14085 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14086 @samp{maint print msymbols} dumps just the minimal symbol information
14087 required for each object file from which @value{GDBN} has read some symbols.
14088 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14089 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14091 @kindex maint info symtabs
14092 @kindex maint info psymtabs
14093 @cindex listing @value{GDBN}'s internal symbol tables
14094 @cindex symbol tables, listing @value{GDBN}'s internal
14095 @cindex full symbol tables, listing @value{GDBN}'s internal
14096 @cindex partial symbol tables, listing @value{GDBN}'s internal
14097 @item maint info symtabs @r{[} @var{regexp} @r{]}
14098 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14100 List the @code{struct symtab} or @code{struct partial_symtab}
14101 structures whose names match @var{regexp}. If @var{regexp} is not
14102 given, list them all. The output includes expressions which you can
14103 copy into a @value{GDBN} debugging this one to examine a particular
14104 structure in more detail. For example:
14107 (@value{GDBP}) maint info psymtabs dwarf2read
14108 @{ objfile /home/gnu/build/gdb/gdb
14109 ((struct objfile *) 0x82e69d0)
14110 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14111 ((struct partial_symtab *) 0x8474b10)
14114 text addresses 0x814d3c8 -- 0x8158074
14115 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14116 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14117 dependencies (none)
14120 (@value{GDBP}) maint info symtabs
14124 We see that there is one partial symbol table whose filename contains
14125 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14126 and we see that @value{GDBN} has not read in any symtabs yet at all.
14127 If we set a breakpoint on a function, that will cause @value{GDBN} to
14128 read the symtab for the compilation unit containing that function:
14131 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14132 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14134 (@value{GDBP}) maint info symtabs
14135 @{ objfile /home/gnu/build/gdb/gdb
14136 ((struct objfile *) 0x82e69d0)
14137 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14138 ((struct symtab *) 0x86c1f38)
14141 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14142 linetable ((struct linetable *) 0x8370fa0)
14143 debugformat DWARF 2
14152 @chapter Altering Execution
14154 Once you think you have found an error in your program, you might want to
14155 find out for certain whether correcting the apparent error would lead to
14156 correct results in the rest of the run. You can find the answer by
14157 experiment, using the @value{GDBN} features for altering execution of the
14160 For example, you can store new values into variables or memory
14161 locations, give your program a signal, restart it at a different
14162 address, or even return prematurely from a function.
14165 * Assignment:: Assignment to variables
14166 * Jumping:: Continuing at a different address
14167 * Signaling:: Giving your program a signal
14168 * Returning:: Returning from a function
14169 * Calling:: Calling your program's functions
14170 * Patching:: Patching your program
14174 @section Assignment to Variables
14177 @cindex setting variables
14178 To alter the value of a variable, evaluate an assignment expression.
14179 @xref{Expressions, ,Expressions}. For example,
14186 stores the value 4 into the variable @code{x}, and then prints the
14187 value of the assignment expression (which is 4).
14188 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14189 information on operators in supported languages.
14191 @kindex set variable
14192 @cindex variables, setting
14193 If you are not interested in seeing the value of the assignment, use the
14194 @code{set} command instead of the @code{print} command. @code{set} is
14195 really the same as @code{print} except that the expression's value is
14196 not printed and is not put in the value history (@pxref{Value History,
14197 ,Value History}). The expression is evaluated only for its effects.
14199 If the beginning of the argument string of the @code{set} command
14200 appears identical to a @code{set} subcommand, use the @code{set
14201 variable} command instead of just @code{set}. This command is identical
14202 to @code{set} except for its lack of subcommands. For example, if your
14203 program has a variable @code{width}, you get an error if you try to set
14204 a new value with just @samp{set width=13}, because @value{GDBN} has the
14205 command @code{set width}:
14208 (@value{GDBP}) whatis width
14210 (@value{GDBP}) p width
14212 (@value{GDBP}) set width=47
14213 Invalid syntax in expression.
14217 The invalid expression, of course, is @samp{=47}. In
14218 order to actually set the program's variable @code{width}, use
14221 (@value{GDBP}) set var width=47
14224 Because the @code{set} command has many subcommands that can conflict
14225 with the names of program variables, it is a good idea to use the
14226 @code{set variable} command instead of just @code{set}. For example, if
14227 your program has a variable @code{g}, you run into problems if you try
14228 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14229 the command @code{set gnutarget}, abbreviated @code{set g}:
14233 (@value{GDBP}) whatis g
14237 (@value{GDBP}) set g=4
14241 The program being debugged has been started already.
14242 Start it from the beginning? (y or n) y
14243 Starting program: /home/smith/cc_progs/a.out
14244 "/home/smith/cc_progs/a.out": can't open to read symbols:
14245 Invalid bfd target.
14246 (@value{GDBP}) show g
14247 The current BFD target is "=4".
14252 The program variable @code{g} did not change, and you silently set the
14253 @code{gnutarget} to an invalid value. In order to set the variable
14257 (@value{GDBP}) set var g=4
14260 @value{GDBN} allows more implicit conversions in assignments than C; you can
14261 freely store an integer value into a pointer variable or vice versa,
14262 and you can convert any structure to any other structure that is the
14263 same length or shorter.
14264 @comment FIXME: how do structs align/pad in these conversions?
14265 @comment /doc@cygnus.com 18dec1990
14267 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14268 construct to generate a value of specified type at a specified address
14269 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14270 to memory location @code{0x83040} as an integer (which implies a certain size
14271 and representation in memory), and
14274 set @{int@}0x83040 = 4
14278 stores the value 4 into that memory location.
14281 @section Continuing at a Different Address
14283 Ordinarily, when you continue your program, you do so at the place where
14284 it stopped, with the @code{continue} command. You can instead continue at
14285 an address of your own choosing, with the following commands:
14289 @item jump @var{linespec}
14290 @itemx jump @var{location}
14291 Resume execution at line @var{linespec} or at address given by
14292 @var{location}. Execution stops again immediately if there is a
14293 breakpoint there. @xref{Specify Location}, for a description of the
14294 different forms of @var{linespec} and @var{location}. It is common
14295 practice to use the @code{tbreak} command in conjunction with
14296 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14298 The @code{jump} command does not change the current stack frame, or
14299 the stack pointer, or the contents of any memory location or any
14300 register other than the program counter. If line @var{linespec} is in
14301 a different function from the one currently executing, the results may
14302 be bizarre if the two functions expect different patterns of arguments or
14303 of local variables. For this reason, the @code{jump} command requests
14304 confirmation if the specified line is not in the function currently
14305 executing. However, even bizarre results are predictable if you are
14306 well acquainted with the machine-language code of your program.
14309 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14310 On many systems, you can get much the same effect as the @code{jump}
14311 command by storing a new value into the register @code{$pc}. The
14312 difference is that this does not start your program running; it only
14313 changes the address of where it @emph{will} run when you continue. For
14321 makes the next @code{continue} command or stepping command execute at
14322 address @code{0x485}, rather than at the address where your program stopped.
14323 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14325 The most common occasion to use the @code{jump} command is to back
14326 up---perhaps with more breakpoints set---over a portion of a program
14327 that has already executed, in order to examine its execution in more
14332 @section Giving your Program a Signal
14333 @cindex deliver a signal to a program
14337 @item signal @var{signal}
14338 Resume execution where your program stopped, but immediately give it the
14339 signal @var{signal}. @var{signal} can be the name or the number of a
14340 signal. For example, on many systems @code{signal 2} and @code{signal
14341 SIGINT} are both ways of sending an interrupt signal.
14343 Alternatively, if @var{signal} is zero, continue execution without
14344 giving a signal. This is useful when your program stopped on account of
14345 a signal and would ordinary see the signal when resumed with the
14346 @code{continue} command; @samp{signal 0} causes it to resume without a
14349 @code{signal} does not repeat when you press @key{RET} a second time
14350 after executing the command.
14354 Invoking the @code{signal} command is not the same as invoking the
14355 @code{kill} utility from the shell. Sending a signal with @code{kill}
14356 causes @value{GDBN} to decide what to do with the signal depending on
14357 the signal handling tables (@pxref{Signals}). The @code{signal} command
14358 passes the signal directly to your program.
14362 @section Returning from a Function
14365 @cindex returning from a function
14368 @itemx return @var{expression}
14369 You can cancel execution of a function call with the @code{return}
14370 command. If you give an
14371 @var{expression} argument, its value is used as the function's return
14375 When you use @code{return}, @value{GDBN} discards the selected stack frame
14376 (and all frames within it). You can think of this as making the
14377 discarded frame return prematurely. If you wish to specify a value to
14378 be returned, give that value as the argument to @code{return}.
14380 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14381 Frame}), and any other frames inside of it, leaving its caller as the
14382 innermost remaining frame. That frame becomes selected. The
14383 specified value is stored in the registers used for returning values
14386 The @code{return} command does not resume execution; it leaves the
14387 program stopped in the state that would exist if the function had just
14388 returned. In contrast, the @code{finish} command (@pxref{Continuing
14389 and Stepping, ,Continuing and Stepping}) resumes execution until the
14390 selected stack frame returns naturally.
14392 @value{GDBN} needs to know how the @var{expression} argument should be set for
14393 the inferior. The concrete registers assignment depends on the OS ABI and the
14394 type being returned by the selected stack frame. For example it is common for
14395 OS ABI to return floating point values in FPU registers while integer values in
14396 CPU registers. Still some ABIs return even floating point values in CPU
14397 registers. Larger integer widths (such as @code{long long int}) also have
14398 specific placement rules. @value{GDBN} already knows the OS ABI from its
14399 current target so it needs to find out also the type being returned to make the
14400 assignment into the right register(s).
14402 Normally, the selected stack frame has debug info. @value{GDBN} will always
14403 use the debug info instead of the implicit type of @var{expression} when the
14404 debug info is available. For example, if you type @kbd{return -1}, and the
14405 function in the current stack frame is declared to return a @code{long long
14406 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14407 into a @code{long long int}:
14410 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14412 (@value{GDBP}) return -1
14413 Make func return now? (y or n) y
14414 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14415 43 printf ("result=%lld\n", func ());
14419 However, if the selected stack frame does not have a debug info, e.g., if the
14420 function was compiled without debug info, @value{GDBN} has to find out the type
14421 to return from user. Specifying a different type by mistake may set the value
14422 in different inferior registers than the caller code expects. For example,
14423 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14424 of a @code{long long int} result for a debug info less function (on 32-bit
14425 architectures). Therefore the user is required to specify the return type by
14426 an appropriate cast explicitly:
14429 Breakpoint 2, 0x0040050b in func ()
14430 (@value{GDBP}) return -1
14431 Return value type not available for selected stack frame.
14432 Please use an explicit cast of the value to return.
14433 (@value{GDBP}) return (long long int) -1
14434 Make selected stack frame return now? (y or n) y
14435 #0 0x00400526 in main ()
14440 @section Calling Program Functions
14443 @cindex calling functions
14444 @cindex inferior functions, calling
14445 @item print @var{expr}
14446 Evaluate the expression @var{expr} and display the resulting value.
14447 @var{expr} may include calls to functions in the program being
14451 @item call @var{expr}
14452 Evaluate the expression @var{expr} without displaying @code{void}
14455 You can use this variant of the @code{print} command if you want to
14456 execute a function from your program that does not return anything
14457 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14458 with @code{void} returned values that @value{GDBN} will otherwise
14459 print. If the result is not void, it is printed and saved in the
14463 It is possible for the function you call via the @code{print} or
14464 @code{call} command to generate a signal (e.g., if there's a bug in
14465 the function, or if you passed it incorrect arguments). What happens
14466 in that case is controlled by the @code{set unwindonsignal} command.
14468 Similarly, with a C@t{++} program it is possible for the function you
14469 call via the @code{print} or @code{call} command to generate an
14470 exception that is not handled due to the constraints of the dummy
14471 frame. In this case, any exception that is raised in the frame, but has
14472 an out-of-frame exception handler will not be found. GDB builds a
14473 dummy-frame for the inferior function call, and the unwinder cannot
14474 seek for exception handlers outside of this dummy-frame. What happens
14475 in that case is controlled by the
14476 @code{set unwind-on-terminating-exception} command.
14479 @item set unwindonsignal
14480 @kindex set unwindonsignal
14481 @cindex unwind stack in called functions
14482 @cindex call dummy stack unwinding
14483 Set unwinding of the stack if a signal is received while in a function
14484 that @value{GDBN} called in the program being debugged. If set to on,
14485 @value{GDBN} unwinds the stack it created for the call and restores
14486 the context to what it was before the call. If set to off (the
14487 default), @value{GDBN} stops in the frame where the signal was
14490 @item show unwindonsignal
14491 @kindex show unwindonsignal
14492 Show the current setting of stack unwinding in the functions called by
14495 @item set unwind-on-terminating-exception
14496 @kindex set unwind-on-terminating-exception
14497 @cindex unwind stack in called functions with unhandled exceptions
14498 @cindex call dummy stack unwinding on unhandled exception.
14499 Set unwinding of the stack if a C@t{++} exception is raised, but left
14500 unhandled while in a function that @value{GDBN} called in the program being
14501 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14502 it created for the call and restores the context to what it was before
14503 the call. If set to off, @value{GDBN} the exception is delivered to
14504 the default C@t{++} exception handler and the inferior terminated.
14506 @item show unwind-on-terminating-exception
14507 @kindex show unwind-on-terminating-exception
14508 Show the current setting of stack unwinding in the functions called by
14513 @cindex weak alias functions
14514 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14515 for another function. In such case, @value{GDBN} might not pick up
14516 the type information, including the types of the function arguments,
14517 which causes @value{GDBN} to call the inferior function incorrectly.
14518 As a result, the called function will function erroneously and may
14519 even crash. A solution to that is to use the name of the aliased
14523 @section Patching Programs
14525 @cindex patching binaries
14526 @cindex writing into executables
14527 @cindex writing into corefiles
14529 By default, @value{GDBN} opens the file containing your program's
14530 executable code (or the corefile) read-only. This prevents accidental
14531 alterations to machine code; but it also prevents you from intentionally
14532 patching your program's binary.
14534 If you'd like to be able to patch the binary, you can specify that
14535 explicitly with the @code{set write} command. For example, you might
14536 want to turn on internal debugging flags, or even to make emergency
14542 @itemx set write off
14543 If you specify @samp{set write on}, @value{GDBN} opens executable and
14544 core files for both reading and writing; if you specify @kbd{set write
14545 off} (the default), @value{GDBN} opens them read-only.
14547 If you have already loaded a file, you must load it again (using the
14548 @code{exec-file} or @code{core-file} command) after changing @code{set
14549 write}, for your new setting to take effect.
14553 Display whether executable files and core files are opened for writing
14554 as well as reading.
14558 @chapter @value{GDBN} Files
14560 @value{GDBN} needs to know the file name of the program to be debugged,
14561 both in order to read its symbol table and in order to start your
14562 program. To debug a core dump of a previous run, you must also tell
14563 @value{GDBN} the name of the core dump file.
14566 * Files:: Commands to specify files
14567 * Separate Debug Files:: Debugging information in separate files
14568 * Index Files:: Index files speed up GDB
14569 * Symbol Errors:: Errors reading symbol files
14570 * Data Files:: GDB data files
14574 @section Commands to Specify Files
14576 @cindex symbol table
14577 @cindex core dump file
14579 You may want to specify executable and core dump file names. The usual
14580 way to do this is at start-up time, using the arguments to
14581 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14582 Out of @value{GDBN}}).
14584 Occasionally it is necessary to change to a different file during a
14585 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14586 specify a file you want to use. Or you are debugging a remote target
14587 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14588 Program}). In these situations the @value{GDBN} commands to specify
14589 new files are useful.
14592 @cindex executable file
14594 @item file @var{filename}
14595 Use @var{filename} as the program to be debugged. It is read for its
14596 symbols and for the contents of pure memory. It is also the program
14597 executed when you use the @code{run} command. If you do not specify a
14598 directory and the file is not found in the @value{GDBN} working directory,
14599 @value{GDBN} uses the environment variable @code{PATH} as a list of
14600 directories to search, just as the shell does when looking for a program
14601 to run. You can change the value of this variable, for both @value{GDBN}
14602 and your program, using the @code{path} command.
14604 @cindex unlinked object files
14605 @cindex patching object files
14606 You can load unlinked object @file{.o} files into @value{GDBN} using
14607 the @code{file} command. You will not be able to ``run'' an object
14608 file, but you can disassemble functions and inspect variables. Also,
14609 if the underlying BFD functionality supports it, you could use
14610 @kbd{gdb -write} to patch object files using this technique. Note
14611 that @value{GDBN} can neither interpret nor modify relocations in this
14612 case, so branches and some initialized variables will appear to go to
14613 the wrong place. But this feature is still handy from time to time.
14616 @code{file} with no argument makes @value{GDBN} discard any information it
14617 has on both executable file and the symbol table.
14620 @item exec-file @r{[} @var{filename} @r{]}
14621 Specify that the program to be run (but not the symbol table) is found
14622 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14623 if necessary to locate your program. Omitting @var{filename} means to
14624 discard information on the executable file.
14626 @kindex symbol-file
14627 @item symbol-file @r{[} @var{filename} @r{]}
14628 Read symbol table information from file @var{filename}. @code{PATH} is
14629 searched when necessary. Use the @code{file} command to get both symbol
14630 table and program to run from the same file.
14632 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14633 program's symbol table.
14635 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14636 some breakpoints and auto-display expressions. This is because they may
14637 contain pointers to the internal data recording symbols and data types,
14638 which are part of the old symbol table data being discarded inside
14641 @code{symbol-file} does not repeat if you press @key{RET} again after
14644 When @value{GDBN} is configured for a particular environment, it
14645 understands debugging information in whatever format is the standard
14646 generated for that environment; you may use either a @sc{gnu} compiler, or
14647 other compilers that adhere to the local conventions.
14648 Best results are usually obtained from @sc{gnu} compilers; for example,
14649 using @code{@value{NGCC}} you can generate debugging information for
14652 For most kinds of object files, with the exception of old SVR3 systems
14653 using COFF, the @code{symbol-file} command does not normally read the
14654 symbol table in full right away. Instead, it scans the symbol table
14655 quickly to find which source files and which symbols are present. The
14656 details are read later, one source file at a time, as they are needed.
14658 The purpose of this two-stage reading strategy is to make @value{GDBN}
14659 start up faster. For the most part, it is invisible except for
14660 occasional pauses while the symbol table details for a particular source
14661 file are being read. (The @code{set verbose} command can turn these
14662 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14663 Warnings and Messages}.)
14665 We have not implemented the two-stage strategy for COFF yet. When the
14666 symbol table is stored in COFF format, @code{symbol-file} reads the
14667 symbol table data in full right away. Note that ``stabs-in-COFF''
14668 still does the two-stage strategy, since the debug info is actually
14672 @cindex reading symbols immediately
14673 @cindex symbols, reading immediately
14674 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14675 @itemx file @r{[} -readnow @r{]} @var{filename}
14676 You can override the @value{GDBN} two-stage strategy for reading symbol
14677 tables by using the @samp{-readnow} option with any of the commands that
14678 load symbol table information, if you want to be sure @value{GDBN} has the
14679 entire symbol table available.
14681 @c FIXME: for now no mention of directories, since this seems to be in
14682 @c flux. 13mar1992 status is that in theory GDB would look either in
14683 @c current dir or in same dir as myprog; but issues like competing
14684 @c GDB's, or clutter in system dirs, mean that in practice right now
14685 @c only current dir is used. FFish says maybe a special GDB hierarchy
14686 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14690 @item core-file @r{[}@var{filename}@r{]}
14692 Specify the whereabouts of a core dump file to be used as the ``contents
14693 of memory''. Traditionally, core files contain only some parts of the
14694 address space of the process that generated them; @value{GDBN} can access the
14695 executable file itself for other parts.
14697 @code{core-file} with no argument specifies that no core file is
14700 Note that the core file is ignored when your program is actually running
14701 under @value{GDBN}. So, if you have been running your program and you
14702 wish to debug a core file instead, you must kill the subprocess in which
14703 the program is running. To do this, use the @code{kill} command
14704 (@pxref{Kill Process, ,Killing the Child Process}).
14706 @kindex add-symbol-file
14707 @cindex dynamic linking
14708 @item add-symbol-file @var{filename} @var{address}
14709 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14710 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14711 The @code{add-symbol-file} command reads additional symbol table
14712 information from the file @var{filename}. You would use this command
14713 when @var{filename} has been dynamically loaded (by some other means)
14714 into the program that is running. @var{address} should be the memory
14715 address at which the file has been loaded; @value{GDBN} cannot figure
14716 this out for itself. You can additionally specify an arbitrary number
14717 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14718 section name and base address for that section. You can specify any
14719 @var{address} as an expression.
14721 The symbol table of the file @var{filename} is added to the symbol table
14722 originally read with the @code{symbol-file} command. You can use the
14723 @code{add-symbol-file} command any number of times; the new symbol data
14724 thus read keeps adding to the old. To discard all old symbol data
14725 instead, use the @code{symbol-file} command without any arguments.
14727 @cindex relocatable object files, reading symbols from
14728 @cindex object files, relocatable, reading symbols from
14729 @cindex reading symbols from relocatable object files
14730 @cindex symbols, reading from relocatable object files
14731 @cindex @file{.o} files, reading symbols from
14732 Although @var{filename} is typically a shared library file, an
14733 executable file, or some other object file which has been fully
14734 relocated for loading into a process, you can also load symbolic
14735 information from relocatable @file{.o} files, as long as:
14739 the file's symbolic information refers only to linker symbols defined in
14740 that file, not to symbols defined by other object files,
14742 every section the file's symbolic information refers to has actually
14743 been loaded into the inferior, as it appears in the file, and
14745 you can determine the address at which every section was loaded, and
14746 provide these to the @code{add-symbol-file} command.
14750 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14751 relocatable files into an already running program; such systems
14752 typically make the requirements above easy to meet. However, it's
14753 important to recognize that many native systems use complex link
14754 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14755 assembly, for example) that make the requirements difficult to meet. In
14756 general, one cannot assume that using @code{add-symbol-file} to read a
14757 relocatable object file's symbolic information will have the same effect
14758 as linking the relocatable object file into the program in the normal
14761 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14763 @kindex add-symbol-file-from-memory
14764 @cindex @code{syscall DSO}
14765 @cindex load symbols from memory
14766 @item add-symbol-file-from-memory @var{address}
14767 Load symbols from the given @var{address} in a dynamically loaded
14768 object file whose image is mapped directly into the inferior's memory.
14769 For example, the Linux kernel maps a @code{syscall DSO} into each
14770 process's address space; this DSO provides kernel-specific code for
14771 some system calls. The argument can be any expression whose
14772 evaluation yields the address of the file's shared object file header.
14773 For this command to work, you must have used @code{symbol-file} or
14774 @code{exec-file} commands in advance.
14776 @kindex add-shared-symbol-files
14778 @item add-shared-symbol-files @var{library-file}
14779 @itemx assf @var{library-file}
14780 The @code{add-shared-symbol-files} command can currently be used only
14781 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14782 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14783 @value{GDBN} automatically looks for shared libraries, however if
14784 @value{GDBN} does not find yours, you can invoke
14785 @code{add-shared-symbol-files}. It takes one argument: the shared
14786 library's file name. @code{assf} is a shorthand alias for
14787 @code{add-shared-symbol-files}.
14790 @item section @var{section} @var{addr}
14791 The @code{section} command changes the base address of the named
14792 @var{section} of the exec file to @var{addr}. This can be used if the
14793 exec file does not contain section addresses, (such as in the
14794 @code{a.out} format), or when the addresses specified in the file
14795 itself are wrong. Each section must be changed separately. The
14796 @code{info files} command, described below, lists all the sections and
14800 @kindex info target
14803 @code{info files} and @code{info target} are synonymous; both print the
14804 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14805 including the names of the executable and core dump files currently in
14806 use by @value{GDBN}, and the files from which symbols were loaded. The
14807 command @code{help target} lists all possible targets rather than
14810 @kindex maint info sections
14811 @item maint info sections
14812 Another command that can give you extra information about program sections
14813 is @code{maint info sections}. In addition to the section information
14814 displayed by @code{info files}, this command displays the flags and file
14815 offset of each section in the executable and core dump files. In addition,
14816 @code{maint info sections} provides the following command options (which
14817 may be arbitrarily combined):
14821 Display sections for all loaded object files, including shared libraries.
14822 @item @var{sections}
14823 Display info only for named @var{sections}.
14824 @item @var{section-flags}
14825 Display info only for sections for which @var{section-flags} are true.
14826 The section flags that @value{GDBN} currently knows about are:
14829 Section will have space allocated in the process when loaded.
14830 Set for all sections except those containing debug information.
14832 Section will be loaded from the file into the child process memory.
14833 Set for pre-initialized code and data, clear for @code{.bss} sections.
14835 Section needs to be relocated before loading.
14837 Section cannot be modified by the child process.
14839 Section contains executable code only.
14841 Section contains data only (no executable code).
14843 Section will reside in ROM.
14845 Section contains data for constructor/destructor lists.
14847 Section is not empty.
14849 An instruction to the linker to not output the section.
14850 @item COFF_SHARED_LIBRARY
14851 A notification to the linker that the section contains
14852 COFF shared library information.
14854 Section contains common symbols.
14857 @kindex set trust-readonly-sections
14858 @cindex read-only sections
14859 @item set trust-readonly-sections on
14860 Tell @value{GDBN} that readonly sections in your object file
14861 really are read-only (i.e.@: that their contents will not change).
14862 In that case, @value{GDBN} can fetch values from these sections
14863 out of the object file, rather than from the target program.
14864 For some targets (notably embedded ones), this can be a significant
14865 enhancement to debugging performance.
14867 The default is off.
14869 @item set trust-readonly-sections off
14870 Tell @value{GDBN} not to trust readonly sections. This means that
14871 the contents of the section might change while the program is running,
14872 and must therefore be fetched from the target when needed.
14874 @item show trust-readonly-sections
14875 Show the current setting of trusting readonly sections.
14878 All file-specifying commands allow both absolute and relative file names
14879 as arguments. @value{GDBN} always converts the file name to an absolute file
14880 name and remembers it that way.
14882 @cindex shared libraries
14883 @anchor{Shared Libraries}
14884 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14885 and IBM RS/6000 AIX shared libraries.
14887 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14888 shared libraries. @xref{Expat}.
14890 @value{GDBN} automatically loads symbol definitions from shared libraries
14891 when you use the @code{run} command, or when you examine a core file.
14892 (Before you issue the @code{run} command, @value{GDBN} does not understand
14893 references to a function in a shared library, however---unless you are
14894 debugging a core file).
14896 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14897 automatically loads the symbols at the time of the @code{shl_load} call.
14899 @c FIXME: some @value{GDBN} release may permit some refs to undef
14900 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14901 @c FIXME...lib; check this from time to time when updating manual
14903 There are times, however, when you may wish to not automatically load
14904 symbol definitions from shared libraries, such as when they are
14905 particularly large or there are many of them.
14907 To control the automatic loading of shared library symbols, use the
14911 @kindex set auto-solib-add
14912 @item set auto-solib-add @var{mode}
14913 If @var{mode} is @code{on}, symbols from all shared object libraries
14914 will be loaded automatically when the inferior begins execution, you
14915 attach to an independently started inferior, or when the dynamic linker
14916 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14917 is @code{off}, symbols must be loaded manually, using the
14918 @code{sharedlibrary} command. The default value is @code{on}.
14920 @cindex memory used for symbol tables
14921 If your program uses lots of shared libraries with debug info that
14922 takes large amounts of memory, you can decrease the @value{GDBN}
14923 memory footprint by preventing it from automatically loading the
14924 symbols from shared libraries. To that end, type @kbd{set
14925 auto-solib-add off} before running the inferior, then load each
14926 library whose debug symbols you do need with @kbd{sharedlibrary
14927 @var{regexp}}, where @var{regexp} is a regular expression that matches
14928 the libraries whose symbols you want to be loaded.
14930 @kindex show auto-solib-add
14931 @item show auto-solib-add
14932 Display the current autoloading mode.
14935 @cindex load shared library
14936 To explicitly load shared library symbols, use the @code{sharedlibrary}
14940 @kindex info sharedlibrary
14942 @item info share @var{regex}
14943 @itemx info sharedlibrary @var{regex}
14944 Print the names of the shared libraries which are currently loaded
14945 that match @var{regex}. If @var{regex} is omitted then print
14946 all shared libraries that are loaded.
14948 @kindex sharedlibrary
14950 @item sharedlibrary @var{regex}
14951 @itemx share @var{regex}
14952 Load shared object library symbols for files matching a
14953 Unix regular expression.
14954 As with files loaded automatically, it only loads shared libraries
14955 required by your program for a core file or after typing @code{run}. If
14956 @var{regex} is omitted all shared libraries required by your program are
14959 @item nosharedlibrary
14960 @kindex nosharedlibrary
14961 @cindex unload symbols from shared libraries
14962 Unload all shared object library symbols. This discards all symbols
14963 that have been loaded from all shared libraries. Symbols from shared
14964 libraries that were loaded by explicit user requests are not
14968 Sometimes you may wish that @value{GDBN} stops and gives you control
14969 when any of shared library events happen. Use the @code{set
14970 stop-on-solib-events} command for this:
14973 @item set stop-on-solib-events
14974 @kindex set stop-on-solib-events
14975 This command controls whether @value{GDBN} should give you control
14976 when the dynamic linker notifies it about some shared library event.
14977 The most common event of interest is loading or unloading of a new
14980 @item show stop-on-solib-events
14981 @kindex show stop-on-solib-events
14982 Show whether @value{GDBN} stops and gives you control when shared
14983 library events happen.
14986 Shared libraries are also supported in many cross or remote debugging
14987 configurations. @value{GDBN} needs to have access to the target's libraries;
14988 this can be accomplished either by providing copies of the libraries
14989 on the host system, or by asking @value{GDBN} to automatically retrieve the
14990 libraries from the target. If copies of the target libraries are
14991 provided, they need to be the same as the target libraries, although the
14992 copies on the target can be stripped as long as the copies on the host are
14995 @cindex where to look for shared libraries
14996 For remote debugging, you need to tell @value{GDBN} where the target
14997 libraries are, so that it can load the correct copies---otherwise, it
14998 may try to load the host's libraries. @value{GDBN} has two variables
14999 to specify the search directories for target libraries.
15002 @cindex prefix for shared library file names
15003 @cindex system root, alternate
15004 @kindex set solib-absolute-prefix
15005 @kindex set sysroot
15006 @item set sysroot @var{path}
15007 Use @var{path} as the system root for the program being debugged. Any
15008 absolute shared library paths will be prefixed with @var{path}; many
15009 runtime loaders store the absolute paths to the shared library in the
15010 target program's memory. If you use @code{set sysroot} to find shared
15011 libraries, they need to be laid out in the same way that they are on
15012 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15015 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15016 retrieve the target libraries from the remote system. This is only
15017 supported when using a remote target that supports the @code{remote get}
15018 command (@pxref{File Transfer,,Sending files to a remote system}).
15019 The part of @var{path} following the initial @file{remote:}
15020 (if present) is used as system root prefix on the remote file system.
15021 @footnote{If you want to specify a local system root using a directory
15022 that happens to be named @file{remote:}, you need to use some equivalent
15023 variant of the name like @file{./remote:}.}
15025 For targets with an MS-DOS based filesystem, such as MS-Windows and
15026 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15027 absolute file name with @var{path}. But first, on Unix hosts,
15028 @value{GDBN} converts all backslash directory separators into forward
15029 slashes, because the backslash is not a directory separator on Unix:
15032 c:\foo\bar.dll @result{} c:/foo/bar.dll
15035 Then, @value{GDBN} attempts prefixing the target file name with
15036 @var{path}, and looks for the resulting file name in the host file
15040 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15043 If that does not find the shared library, @value{GDBN} tries removing
15044 the @samp{:} character from the drive spec, both for convenience, and,
15045 for the case of the host file system not supporting file names with
15049 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15052 This makes it possible to have a system root that mirrors a target
15053 with more than one drive. E.g., you may want to setup your local
15054 copies of the target system shared libraries like so (note @samp{c} vs
15058 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15059 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15060 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15064 and point the system root at @file{/path/to/sysroot}, so that
15065 @value{GDBN} can find the correct copies of both
15066 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15068 If that still does not find the shared library, @value{GDBN} tries
15069 removing the whole drive spec from the target file name:
15072 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15075 This last lookup makes it possible to not care about the drive name,
15076 if you don't want or need to.
15078 The @code{set solib-absolute-prefix} command is an alias for @code{set
15081 @cindex default system root
15082 @cindex @samp{--with-sysroot}
15083 You can set the default system root by using the configure-time
15084 @samp{--with-sysroot} option. If the system root is inside
15085 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15086 @samp{--exec-prefix}), then the default system root will be updated
15087 automatically if the installed @value{GDBN} is moved to a new
15090 @kindex show sysroot
15092 Display the current shared library prefix.
15094 @kindex set solib-search-path
15095 @item set solib-search-path @var{path}
15096 If this variable is set, @var{path} is a colon-separated list of
15097 directories to search for shared libraries. @samp{solib-search-path}
15098 is used after @samp{sysroot} fails to locate the library, or if the
15099 path to the library is relative instead of absolute. If you want to
15100 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15101 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15102 finding your host's libraries. @samp{sysroot} is preferred; setting
15103 it to a nonexistent directory may interfere with automatic loading
15104 of shared library symbols.
15106 @kindex show solib-search-path
15107 @item show solib-search-path
15108 Display the current shared library search path.
15110 @cindex DOS file-name semantics of file names.
15111 @kindex set target-file-system-kind (unix|dos-based|auto)
15112 @kindex show target-file-system-kind
15113 @item set target-file-system-kind @var{kind}
15114 Set assumed file system kind for target reported file names.
15116 Shared library file names as reported by the target system may not
15117 make sense as is on the system @value{GDBN} is running on. For
15118 example, when remote debugging a target that has MS-DOS based file
15119 system semantics, from a Unix host, the target may be reporting to
15120 @value{GDBN} a list of loaded shared libraries with file names such as
15121 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15122 drive letters, so the @samp{c:\} prefix is not normally understood as
15123 indicating an absolute file name, and neither is the backslash
15124 normally considered a directory separator character. In that case,
15125 the native file system would interpret this whole absolute file name
15126 as a relative file name with no directory components. This would make
15127 it impossible to point @value{GDBN} at a copy of the remote target's
15128 shared libraries on the host using @code{set sysroot}, and impractical
15129 with @code{set solib-search-path}. Setting
15130 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15131 to interpret such file names similarly to how the target would, and to
15132 map them to file names valid on @value{GDBN}'s native file system
15133 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15134 to one of the supported file system kinds. In that case, @value{GDBN}
15135 tries to determine the appropriate file system variant based on the
15136 current target's operating system (@pxref{ABI, ,Configuring the
15137 Current ABI}). The supported file system settings are:
15141 Instruct @value{GDBN} to assume the target file system is of Unix
15142 kind. Only file names starting the forward slash (@samp{/}) character
15143 are considered absolute, and the directory separator character is also
15147 Instruct @value{GDBN} to assume the target file system is DOS based.
15148 File names starting with either a forward slash, or a drive letter
15149 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15150 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15151 considered directory separators.
15154 Instruct @value{GDBN} to use the file system kind associated with the
15155 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15156 This is the default.
15161 @node Separate Debug Files
15162 @section Debugging Information in Separate Files
15163 @cindex separate debugging information files
15164 @cindex debugging information in separate files
15165 @cindex @file{.debug} subdirectories
15166 @cindex debugging information directory, global
15167 @cindex global debugging information directory
15168 @cindex build ID, and separate debugging files
15169 @cindex @file{.build-id} directory
15171 @value{GDBN} allows you to put a program's debugging information in a
15172 file separate from the executable itself, in a way that allows
15173 @value{GDBN} to find and load the debugging information automatically.
15174 Since debugging information can be very large---sometimes larger
15175 than the executable code itself---some systems distribute debugging
15176 information for their executables in separate files, which users can
15177 install only when they need to debug a problem.
15179 @value{GDBN} supports two ways of specifying the separate debug info
15184 The executable contains a @dfn{debug link} that specifies the name of
15185 the separate debug info file. The separate debug file's name is
15186 usually @file{@var{executable}.debug}, where @var{executable} is the
15187 name of the corresponding executable file without leading directories
15188 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15189 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15190 checksum for the debug file, which @value{GDBN} uses to validate that
15191 the executable and the debug file came from the same build.
15194 The executable contains a @dfn{build ID}, a unique bit string that is
15195 also present in the corresponding debug info file. (This is supported
15196 only on some operating systems, notably those which use the ELF format
15197 for binary files and the @sc{gnu} Binutils.) For more details about
15198 this feature, see the description of the @option{--build-id}
15199 command-line option in @ref{Options, , Command Line Options, ld.info,
15200 The GNU Linker}. The debug info file's name is not specified
15201 explicitly by the build ID, but can be computed from the build ID, see
15205 Depending on the way the debug info file is specified, @value{GDBN}
15206 uses two different methods of looking for the debug file:
15210 For the ``debug link'' method, @value{GDBN} looks up the named file in
15211 the directory of the executable file, then in a subdirectory of that
15212 directory named @file{.debug}, and finally under the global debug
15213 directory, in a subdirectory whose name is identical to the leading
15214 directories of the executable's absolute file name.
15217 For the ``build ID'' method, @value{GDBN} looks in the
15218 @file{.build-id} subdirectory of the global debug directory for a file
15219 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15220 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15221 are the rest of the bit string. (Real build ID strings are 32 or more
15222 hex characters, not 10.)
15225 So, for example, suppose you ask @value{GDBN} to debug
15226 @file{/usr/bin/ls}, which has a debug link that specifies the
15227 file @file{ls.debug}, and a build ID whose value in hex is
15228 @code{abcdef1234}. If the global debug directory is
15229 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15230 debug information files, in the indicated order:
15234 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15236 @file{/usr/bin/ls.debug}
15238 @file{/usr/bin/.debug/ls.debug}
15240 @file{/usr/lib/debug/usr/bin/ls.debug}.
15243 You can set the global debugging info directory's name, and view the
15244 name @value{GDBN} is currently using.
15248 @kindex set debug-file-directory
15249 @item set debug-file-directory @var{directories}
15250 Set the directories which @value{GDBN} searches for separate debugging
15251 information files to @var{directory}. Multiple directory components can be set
15252 concatenating them by a directory separator.
15254 @kindex show debug-file-directory
15255 @item show debug-file-directory
15256 Show the directories @value{GDBN} searches for separate debugging
15261 @cindex @code{.gnu_debuglink} sections
15262 @cindex debug link sections
15263 A debug link is a special section of the executable file named
15264 @code{.gnu_debuglink}. The section must contain:
15268 A filename, with any leading directory components removed, followed by
15271 zero to three bytes of padding, as needed to reach the next four-byte
15272 boundary within the section, and
15274 a four-byte CRC checksum, stored in the same endianness used for the
15275 executable file itself. The checksum is computed on the debugging
15276 information file's full contents by the function given below, passing
15277 zero as the @var{crc} argument.
15280 Any executable file format can carry a debug link, as long as it can
15281 contain a section named @code{.gnu_debuglink} with the contents
15284 @cindex @code{.note.gnu.build-id} sections
15285 @cindex build ID sections
15286 The build ID is a special section in the executable file (and in other
15287 ELF binary files that @value{GDBN} may consider). This section is
15288 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15289 It contains unique identification for the built files---the ID remains
15290 the same across multiple builds of the same build tree. The default
15291 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15292 content for the build ID string. The same section with an identical
15293 value is present in the original built binary with symbols, in its
15294 stripped variant, and in the separate debugging information file.
15296 The debugging information file itself should be an ordinary
15297 executable, containing a full set of linker symbols, sections, and
15298 debugging information. The sections of the debugging information file
15299 should have the same names, addresses, and sizes as the original file,
15300 but they need not contain any data---much like a @code{.bss} section
15301 in an ordinary executable.
15303 The @sc{gnu} binary utilities (Binutils) package includes the
15304 @samp{objcopy} utility that can produce
15305 the separated executable / debugging information file pairs using the
15306 following commands:
15309 @kbd{objcopy --only-keep-debug foo foo.debug}
15314 These commands remove the debugging
15315 information from the executable file @file{foo} and place it in the file
15316 @file{foo.debug}. You can use the first, second or both methods to link the
15321 The debug link method needs the following additional command to also leave
15322 behind a debug link in @file{foo}:
15325 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15328 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15329 a version of the @code{strip} command such that the command @kbd{strip foo -f
15330 foo.debug} has the same functionality as the two @code{objcopy} commands and
15331 the @code{ln -s} command above, together.
15334 Build ID gets embedded into the main executable using @code{ld --build-id} or
15335 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15336 compatibility fixes for debug files separation are present in @sc{gnu} binary
15337 utilities (Binutils) package since version 2.18.
15342 @cindex CRC algorithm definition
15343 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15344 IEEE 802.3 using the polynomial:
15346 @c TexInfo requires naked braces for multi-digit exponents for Tex
15347 @c output, but this causes HTML output to barf. HTML has to be set using
15348 @c raw commands. So we end up having to specify this equation in 2
15353 <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>
15354 + <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
15360 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15361 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15365 The function is computed byte at a time, taking the least
15366 significant bit of each byte first. The initial pattern
15367 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15368 the final result is inverted to ensure trailing zeros also affect the
15371 @emph{Note:} This is the same CRC polynomial as used in handling the
15372 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15373 , @value{GDBN} Remote Serial Protocol}). However in the
15374 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15375 significant bit first, and the result is not inverted, so trailing
15376 zeros have no effect on the CRC value.
15378 To complete the description, we show below the code of the function
15379 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15380 initially supplied @code{crc} argument means that an initial call to
15381 this function passing in zero will start computing the CRC using
15384 @kindex gnu_debuglink_crc32
15387 gnu_debuglink_crc32 (unsigned long crc,
15388 unsigned char *buf, size_t len)
15390 static const unsigned long crc32_table[256] =
15392 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15393 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15394 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15395 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15396 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15397 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15398 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15399 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15400 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15401 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15402 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15403 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15404 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15405 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15406 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15407 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15408 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15409 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15410 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15411 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15412 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15413 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15414 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15415 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15416 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15417 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15418 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15419 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15420 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15421 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15422 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15423 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15424 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15425 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15426 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15427 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15428 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15429 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15430 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15431 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15432 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15433 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15434 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15435 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15436 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15437 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15438 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15439 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15440 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15441 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15442 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15445 unsigned char *end;
15447 crc = ~crc & 0xffffffff;
15448 for (end = buf + len; buf < end; ++buf)
15449 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15450 return ~crc & 0xffffffff;
15455 This computation does not apply to the ``build ID'' method.
15459 @section Index Files Speed Up @value{GDBN}
15460 @cindex index files
15461 @cindex @samp{.gdb_index} section
15463 When @value{GDBN} finds a symbol file, it scans the symbols in the
15464 file in order to construct an internal symbol table. This lets most
15465 @value{GDBN} operations work quickly---at the cost of a delay early
15466 on. For large programs, this delay can be quite lengthy, so
15467 @value{GDBN} provides a way to build an index, which speeds up
15470 The index is stored as a section in the symbol file. @value{GDBN} can
15471 write the index to a file, then you can put it into the symbol file
15472 using @command{objcopy}.
15474 To create an index file, use the @code{save gdb-index} command:
15477 @item save gdb-index @var{directory}
15478 @kindex save gdb-index
15479 Create an index file for each symbol file currently known by
15480 @value{GDBN}. Each file is named after its corresponding symbol file,
15481 with @samp{.gdb-index} appended, and is written into the given
15485 Once you have created an index file you can merge it into your symbol
15486 file, here named @file{symfile}, using @command{objcopy}:
15489 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15490 --set-section-flags .gdb_index=readonly symfile symfile
15493 There are currently some limitation on indices. They only work when
15494 for DWARF debugging information, not stabs. And, they do not
15495 currently work for programs using Ada.
15497 @node Symbol Errors
15498 @section Errors Reading Symbol Files
15500 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15501 such as symbol types it does not recognize, or known bugs in compiler
15502 output. By default, @value{GDBN} does not notify you of such problems, since
15503 they are relatively common and primarily of interest to people
15504 debugging compilers. If you are interested in seeing information
15505 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15506 only one message about each such type of problem, no matter how many
15507 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15508 to see how many times the problems occur, with the @code{set
15509 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15512 The messages currently printed, and their meanings, include:
15515 @item inner block not inside outer block in @var{symbol}
15517 The symbol information shows where symbol scopes begin and end
15518 (such as at the start of a function or a block of statements). This
15519 error indicates that an inner scope block is not fully contained
15520 in its outer scope blocks.
15522 @value{GDBN} circumvents the problem by treating the inner block as if it had
15523 the same scope as the outer block. In the error message, @var{symbol}
15524 may be shown as ``@code{(don't know)}'' if the outer block is not a
15527 @item block at @var{address} out of order
15529 The symbol information for symbol scope blocks should occur in
15530 order of increasing addresses. This error indicates that it does not
15533 @value{GDBN} does not circumvent this problem, and has trouble
15534 locating symbols in the source file whose symbols it is reading. (You
15535 can often determine what source file is affected by specifying
15536 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15539 @item bad block start address patched
15541 The symbol information for a symbol scope block has a start address
15542 smaller than the address of the preceding source line. This is known
15543 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15545 @value{GDBN} circumvents the problem by treating the symbol scope block as
15546 starting on the previous source line.
15548 @item bad string table offset in symbol @var{n}
15551 Symbol number @var{n} contains a pointer into the string table which is
15552 larger than the size of the string table.
15554 @value{GDBN} circumvents the problem by considering the symbol to have the
15555 name @code{foo}, which may cause other problems if many symbols end up
15558 @item unknown symbol type @code{0x@var{nn}}
15560 The symbol information contains new data types that @value{GDBN} does
15561 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15562 uncomprehended information, in hexadecimal.
15564 @value{GDBN} circumvents the error by ignoring this symbol information.
15565 This usually allows you to debug your program, though certain symbols
15566 are not accessible. If you encounter such a problem and feel like
15567 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15568 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15569 and examine @code{*bufp} to see the symbol.
15571 @item stub type has NULL name
15573 @value{GDBN} could not find the full definition for a struct or class.
15575 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15576 The symbol information for a C@t{++} member function is missing some
15577 information that recent versions of the compiler should have output for
15580 @item info mismatch between compiler and debugger
15582 @value{GDBN} could not parse a type specification output by the compiler.
15587 @section GDB Data Files
15589 @cindex prefix for data files
15590 @value{GDBN} will sometimes read an auxiliary data file. These files
15591 are kept in a directory known as the @dfn{data directory}.
15593 You can set the data directory's name, and view the name @value{GDBN}
15594 is currently using.
15597 @kindex set data-directory
15598 @item set data-directory @var{directory}
15599 Set the directory which @value{GDBN} searches for auxiliary data files
15600 to @var{directory}.
15602 @kindex show data-directory
15603 @item show data-directory
15604 Show the directory @value{GDBN} searches for auxiliary data files.
15607 @cindex default data directory
15608 @cindex @samp{--with-gdb-datadir}
15609 You can set the default data directory by using the configure-time
15610 @samp{--with-gdb-datadir} option. If the data directory is inside
15611 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15612 @samp{--exec-prefix}), then the default data directory will be updated
15613 automatically if the installed @value{GDBN} is moved to a new
15616 The data directory may also be specified with the
15617 @code{--data-directory} command line option.
15618 @xref{Mode Options}.
15621 @chapter Specifying a Debugging Target
15623 @cindex debugging target
15624 A @dfn{target} is the execution environment occupied by your program.
15626 Often, @value{GDBN} runs in the same host environment as your program;
15627 in that case, the debugging target is specified as a side effect when
15628 you use the @code{file} or @code{core} commands. When you need more
15629 flexibility---for example, running @value{GDBN} on a physically separate
15630 host, or controlling a standalone system over a serial port or a
15631 realtime system over a TCP/IP connection---you can use the @code{target}
15632 command to specify one of the target types configured for @value{GDBN}
15633 (@pxref{Target Commands, ,Commands for Managing Targets}).
15635 @cindex target architecture
15636 It is possible to build @value{GDBN} for several different @dfn{target
15637 architectures}. When @value{GDBN} is built like that, you can choose
15638 one of the available architectures with the @kbd{set architecture}
15642 @kindex set architecture
15643 @kindex show architecture
15644 @item set architecture @var{arch}
15645 This command sets the current target architecture to @var{arch}. The
15646 value of @var{arch} can be @code{"auto"}, in addition to one of the
15647 supported architectures.
15649 @item show architecture
15650 Show the current target architecture.
15652 @item set processor
15654 @kindex set processor
15655 @kindex show processor
15656 These are alias commands for, respectively, @code{set architecture}
15657 and @code{show architecture}.
15661 * Active Targets:: Active targets
15662 * Target Commands:: Commands for managing targets
15663 * Byte Order:: Choosing target byte order
15666 @node Active Targets
15667 @section Active Targets
15669 @cindex stacking targets
15670 @cindex active targets
15671 @cindex multiple targets
15673 There are multiple classes of targets such as: processes, executable files or
15674 recording sessions. Core files belong to the process class, making core file
15675 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15676 on multiple active targets, one in each class. This allows you to (for
15677 example) start a process and inspect its activity, while still having access to
15678 the executable file after the process finishes. Or if you start process
15679 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15680 presented a virtual layer of the recording target, while the process target
15681 remains stopped at the chronologically last point of the process execution.
15683 Use the @code{core-file} and @code{exec-file} commands to select a new core
15684 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15685 specify as a target a process that is already running, use the @code{attach}
15686 command (@pxref{Attach, ,Debugging an Already-running Process}).
15688 @node Target Commands
15689 @section Commands for Managing Targets
15692 @item target @var{type} @var{parameters}
15693 Connects the @value{GDBN} host environment to a target machine or
15694 process. A target is typically a protocol for talking to debugging
15695 facilities. You use the argument @var{type} to specify the type or
15696 protocol of the target machine.
15698 Further @var{parameters} are interpreted by the target protocol, but
15699 typically include things like device names or host names to connect
15700 with, process numbers, and baud rates.
15702 The @code{target} command does not repeat if you press @key{RET} again
15703 after executing the command.
15705 @kindex help target
15707 Displays the names of all targets available. To display targets
15708 currently selected, use either @code{info target} or @code{info files}
15709 (@pxref{Files, ,Commands to Specify Files}).
15711 @item help target @var{name}
15712 Describe a particular target, including any parameters necessary to
15715 @kindex set gnutarget
15716 @item set gnutarget @var{args}
15717 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15718 knows whether it is reading an @dfn{executable},
15719 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15720 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15721 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15724 @emph{Warning:} To specify a file format with @code{set gnutarget},
15725 you must know the actual BFD name.
15729 @xref{Files, , Commands to Specify Files}.
15731 @kindex show gnutarget
15732 @item show gnutarget
15733 Use the @code{show gnutarget} command to display what file format
15734 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15735 @value{GDBN} will determine the file format for each file automatically,
15736 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15739 @cindex common targets
15740 Here are some common targets (available, or not, depending on the GDB
15745 @item target exec @var{program}
15746 @cindex executable file target
15747 An executable file. @samp{target exec @var{program}} is the same as
15748 @samp{exec-file @var{program}}.
15750 @item target core @var{filename}
15751 @cindex core dump file target
15752 A core dump file. @samp{target core @var{filename}} is the same as
15753 @samp{core-file @var{filename}}.
15755 @item target remote @var{medium}
15756 @cindex remote target
15757 A remote system connected to @value{GDBN} via a serial line or network
15758 connection. This command tells @value{GDBN} to use its own remote
15759 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15761 For example, if you have a board connected to @file{/dev/ttya} on the
15762 machine running @value{GDBN}, you could say:
15765 target remote /dev/ttya
15768 @code{target remote} supports the @code{load} command. This is only
15769 useful if you have some other way of getting the stub to the target
15770 system, and you can put it somewhere in memory where it won't get
15771 clobbered by the download.
15773 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15774 @cindex built-in simulator target
15775 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15783 works; however, you cannot assume that a specific memory map, device
15784 drivers, or even basic I/O is available, although some simulators do
15785 provide these. For info about any processor-specific simulator details,
15786 see the appropriate section in @ref{Embedded Processors, ,Embedded
15791 Some configurations may include these targets as well:
15795 @item target nrom @var{dev}
15796 @cindex NetROM ROM emulator target
15797 NetROM ROM emulator. This target only supports downloading.
15801 Different targets are available on different configurations of @value{GDBN};
15802 your configuration may have more or fewer targets.
15804 Many remote targets require you to download the executable's code once
15805 you've successfully established a connection. You may wish to control
15806 various aspects of this process.
15811 @kindex set hash@r{, for remote monitors}
15812 @cindex hash mark while downloading
15813 This command controls whether a hash mark @samp{#} is displayed while
15814 downloading a file to the remote monitor. If on, a hash mark is
15815 displayed after each S-record is successfully downloaded to the
15819 @kindex show hash@r{, for remote monitors}
15820 Show the current status of displaying the hash mark.
15822 @item set debug monitor
15823 @kindex set debug monitor
15824 @cindex display remote monitor communications
15825 Enable or disable display of communications messages between
15826 @value{GDBN} and the remote monitor.
15828 @item show debug monitor
15829 @kindex show debug monitor
15830 Show the current status of displaying communications between
15831 @value{GDBN} and the remote monitor.
15836 @kindex load @var{filename}
15837 @item load @var{filename}
15839 Depending on what remote debugging facilities are configured into
15840 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15841 is meant to make @var{filename} (an executable) available for debugging
15842 on the remote system---by downloading, or dynamic linking, for example.
15843 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15844 the @code{add-symbol-file} command.
15846 If your @value{GDBN} does not have a @code{load} command, attempting to
15847 execute it gets the error message ``@code{You can't do that when your
15848 target is @dots{}}''
15850 The file is loaded at whatever address is specified in the executable.
15851 For some object file formats, you can specify the load address when you
15852 link the program; for other formats, like a.out, the object file format
15853 specifies a fixed address.
15854 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15856 Depending on the remote side capabilities, @value{GDBN} may be able to
15857 load programs into flash memory.
15859 @code{load} does not repeat if you press @key{RET} again after using it.
15863 @section Choosing Target Byte Order
15865 @cindex choosing target byte order
15866 @cindex target byte order
15868 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15869 offer the ability to run either big-endian or little-endian byte
15870 orders. Usually the executable or symbol will include a bit to
15871 designate the endian-ness, and you will not need to worry about
15872 which to use. However, you may still find it useful to adjust
15873 @value{GDBN}'s idea of processor endian-ness manually.
15877 @item set endian big
15878 Instruct @value{GDBN} to assume the target is big-endian.
15880 @item set endian little
15881 Instruct @value{GDBN} to assume the target is little-endian.
15883 @item set endian auto
15884 Instruct @value{GDBN} to use the byte order associated with the
15888 Display @value{GDBN}'s current idea of the target byte order.
15892 Note that these commands merely adjust interpretation of symbolic
15893 data on the host, and that they have absolutely no effect on the
15897 @node Remote Debugging
15898 @chapter Debugging Remote Programs
15899 @cindex remote debugging
15901 If you are trying to debug a program running on a machine that cannot run
15902 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15903 For example, you might use remote debugging on an operating system kernel,
15904 or on a small system which does not have a general purpose operating system
15905 powerful enough to run a full-featured debugger.
15907 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15908 to make this work with particular debugging targets. In addition,
15909 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15910 but not specific to any particular target system) which you can use if you
15911 write the remote stubs---the code that runs on the remote system to
15912 communicate with @value{GDBN}.
15914 Other remote targets may be available in your
15915 configuration of @value{GDBN}; use @code{help target} to list them.
15918 * Connecting:: Connecting to a remote target
15919 * File Transfer:: Sending files to a remote system
15920 * Server:: Using the gdbserver program
15921 * Remote Configuration:: Remote configuration
15922 * Remote Stub:: Implementing a remote stub
15926 @section Connecting to a Remote Target
15928 On the @value{GDBN} host machine, you will need an unstripped copy of
15929 your program, since @value{GDBN} needs symbol and debugging information.
15930 Start up @value{GDBN} as usual, using the name of the local copy of your
15931 program as the first argument.
15933 @cindex @code{target remote}
15934 @value{GDBN} can communicate with the target over a serial line, or
15935 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15936 each case, @value{GDBN} uses the same protocol for debugging your
15937 program; only the medium carrying the debugging packets varies. The
15938 @code{target remote} command establishes a connection to the target.
15939 Its arguments indicate which medium to use:
15943 @item target remote @var{serial-device}
15944 @cindex serial line, @code{target remote}
15945 Use @var{serial-device} to communicate with the target. For example,
15946 to use a serial line connected to the device named @file{/dev/ttyb}:
15949 target remote /dev/ttyb
15952 If you're using a serial line, you may want to give @value{GDBN} the
15953 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15954 (@pxref{Remote Configuration, set remotebaud}) before the
15955 @code{target} command.
15957 @item target remote @code{@var{host}:@var{port}}
15958 @itemx target remote @code{tcp:@var{host}:@var{port}}
15959 @cindex @acronym{TCP} port, @code{target remote}
15960 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15961 The @var{host} may be either a host name or a numeric @acronym{IP}
15962 address; @var{port} must be a decimal number. The @var{host} could be
15963 the target machine itself, if it is directly connected to the net, or
15964 it might be a terminal server which in turn has a serial line to the
15967 For example, to connect to port 2828 on a terminal server named
15971 target remote manyfarms:2828
15974 If your remote target is actually running on the same machine as your
15975 debugger session (e.g.@: a simulator for your target running on the
15976 same host), you can omit the hostname. For example, to connect to
15977 port 1234 on your local machine:
15980 target remote :1234
15984 Note that the colon is still required here.
15986 @item target remote @code{udp:@var{host}:@var{port}}
15987 @cindex @acronym{UDP} port, @code{target remote}
15988 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15989 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15992 target remote udp:manyfarms:2828
15995 When using a @acronym{UDP} connection for remote debugging, you should
15996 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15997 can silently drop packets on busy or unreliable networks, which will
15998 cause havoc with your debugging session.
16000 @item target remote | @var{command}
16001 @cindex pipe, @code{target remote} to
16002 Run @var{command} in the background and communicate with it using a
16003 pipe. The @var{command} is a shell command, to be parsed and expanded
16004 by the system's command shell, @code{/bin/sh}; it should expect remote
16005 protocol packets on its standard input, and send replies on its
16006 standard output. You could use this to run a stand-alone simulator
16007 that speaks the remote debugging protocol, to make net connections
16008 using programs like @code{ssh}, or for other similar tricks.
16010 If @var{command} closes its standard output (perhaps by exiting),
16011 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16012 program has already exited, this will have no effect.)
16016 Once the connection has been established, you can use all the usual
16017 commands to examine and change data. The remote program is already
16018 running; you can use @kbd{step} and @kbd{continue}, and you do not
16019 need to use @kbd{run}.
16021 @cindex interrupting remote programs
16022 @cindex remote programs, interrupting
16023 Whenever @value{GDBN} is waiting for the remote program, if you type the
16024 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16025 program. This may or may not succeed, depending in part on the hardware
16026 and the serial drivers the remote system uses. If you type the
16027 interrupt character once again, @value{GDBN} displays this prompt:
16030 Interrupted while waiting for the program.
16031 Give up (and stop debugging it)? (y or n)
16034 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16035 (If you decide you want to try again later, you can use @samp{target
16036 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16037 goes back to waiting.
16040 @kindex detach (remote)
16042 When you have finished debugging the remote program, you can use the
16043 @code{detach} command to release it from @value{GDBN} control.
16044 Detaching from the target normally resumes its execution, but the results
16045 will depend on your particular remote stub. After the @code{detach}
16046 command, @value{GDBN} is free to connect to another target.
16050 The @code{disconnect} command behaves like @code{detach}, except that
16051 the target is generally not resumed. It will wait for @value{GDBN}
16052 (this instance or another one) to connect and continue debugging. After
16053 the @code{disconnect} command, @value{GDBN} is again free to connect to
16056 @cindex send command to remote monitor
16057 @cindex extend @value{GDBN} for remote targets
16058 @cindex add new commands for external monitor
16060 @item monitor @var{cmd}
16061 This command allows you to send arbitrary commands directly to the
16062 remote monitor. Since @value{GDBN} doesn't care about the commands it
16063 sends like this, this command is the way to extend @value{GDBN}---you
16064 can add new commands that only the external monitor will understand
16068 @node File Transfer
16069 @section Sending files to a remote system
16070 @cindex remote target, file transfer
16071 @cindex file transfer
16072 @cindex sending files to remote systems
16074 Some remote targets offer the ability to transfer files over the same
16075 connection used to communicate with @value{GDBN}. This is convenient
16076 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16077 running @code{gdbserver} over a network interface. For other targets,
16078 e.g.@: embedded devices with only a single serial port, this may be
16079 the only way to upload or download files.
16081 Not all remote targets support these commands.
16085 @item remote put @var{hostfile} @var{targetfile}
16086 Copy file @var{hostfile} from the host system (the machine running
16087 @value{GDBN}) to @var{targetfile} on the target system.
16090 @item remote get @var{targetfile} @var{hostfile}
16091 Copy file @var{targetfile} from the target system to @var{hostfile}
16092 on the host system.
16094 @kindex remote delete
16095 @item remote delete @var{targetfile}
16096 Delete @var{targetfile} from the target system.
16101 @section Using the @code{gdbserver} Program
16104 @cindex remote connection without stubs
16105 @code{gdbserver} is a control program for Unix-like systems, which
16106 allows you to connect your program with a remote @value{GDBN} via
16107 @code{target remote}---but without linking in the usual debugging stub.
16109 @code{gdbserver} is not a complete replacement for the debugging stubs,
16110 because it requires essentially the same operating-system facilities
16111 that @value{GDBN} itself does. In fact, a system that can run
16112 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16113 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16114 because it is a much smaller program than @value{GDBN} itself. It is
16115 also easier to port than all of @value{GDBN}, so you may be able to get
16116 started more quickly on a new system by using @code{gdbserver}.
16117 Finally, if you develop code for real-time systems, you may find that
16118 the tradeoffs involved in real-time operation make it more convenient to
16119 do as much development work as possible on another system, for example
16120 by cross-compiling. You can use @code{gdbserver} to make a similar
16121 choice for debugging.
16123 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16124 or a TCP connection, using the standard @value{GDBN} remote serial
16128 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16129 Do not run @code{gdbserver} connected to any public network; a
16130 @value{GDBN} connection to @code{gdbserver} provides access to the
16131 target system with the same privileges as the user running
16135 @subsection Running @code{gdbserver}
16136 @cindex arguments, to @code{gdbserver}
16138 Run @code{gdbserver} on the target system. You need a copy of the
16139 program you want to debug, including any libraries it requires.
16140 @code{gdbserver} does not need your program's symbol table, so you can
16141 strip the program if necessary to save space. @value{GDBN} on the host
16142 system does all the symbol handling.
16144 To use the server, you must tell it how to communicate with @value{GDBN};
16145 the name of your program; and the arguments for your program. The usual
16149 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16152 @var{comm} is either a device name (to use a serial line) or a TCP
16153 hostname and portnumber. For example, to debug Emacs with the argument
16154 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16158 target> gdbserver /dev/com1 emacs foo.txt
16161 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16164 To use a TCP connection instead of a serial line:
16167 target> gdbserver host:2345 emacs foo.txt
16170 The only difference from the previous example is the first argument,
16171 specifying that you are communicating with the host @value{GDBN} via
16172 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16173 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16174 (Currently, the @samp{host} part is ignored.) You can choose any number
16175 you want for the port number as long as it does not conflict with any
16176 TCP ports already in use on the target system (for example, @code{23} is
16177 reserved for @code{telnet}).@footnote{If you choose a port number that
16178 conflicts with another service, @code{gdbserver} prints an error message
16179 and exits.} You must use the same port number with the host @value{GDBN}
16180 @code{target remote} command.
16182 @subsubsection Attaching to a Running Program
16184 On some targets, @code{gdbserver} can also attach to running programs.
16185 This is accomplished via the @code{--attach} argument. The syntax is:
16188 target> gdbserver --attach @var{comm} @var{pid}
16191 @var{pid} is the process ID of a currently running process. It isn't necessary
16192 to point @code{gdbserver} at a binary for the running process.
16195 @cindex attach to a program by name
16196 You can debug processes by name instead of process ID if your target has the
16197 @code{pidof} utility:
16200 target> gdbserver --attach @var{comm} `pidof @var{program}`
16203 In case more than one copy of @var{program} is running, or @var{program}
16204 has multiple threads, most versions of @code{pidof} support the
16205 @code{-s} option to only return the first process ID.
16207 @subsubsection Multi-Process Mode for @code{gdbserver}
16208 @cindex gdbserver, multiple processes
16209 @cindex multiple processes with gdbserver
16211 When you connect to @code{gdbserver} using @code{target remote},
16212 @code{gdbserver} debugs the specified program only once. When the
16213 program exits, or you detach from it, @value{GDBN} closes the connection
16214 and @code{gdbserver} exits.
16216 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16217 enters multi-process mode. When the debugged program exits, or you
16218 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16219 though no program is running. The @code{run} and @code{attach}
16220 commands instruct @code{gdbserver} to run or attach to a new program.
16221 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16222 remote exec-file}) to select the program to run. Command line
16223 arguments are supported, except for wildcard expansion and I/O
16224 redirection (@pxref{Arguments}).
16226 To start @code{gdbserver} without supplying an initial command to run
16227 or process ID to attach, use the @option{--multi} command line option.
16228 Then you can connect using @kbd{target extended-remote} and start
16229 the program you want to debug.
16231 @code{gdbserver} does not automatically exit in multi-process mode.
16232 You can terminate it by using @code{monitor exit}
16233 (@pxref{Monitor Commands for gdbserver}).
16235 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16237 The @option{--debug} option tells @code{gdbserver} to display extra
16238 status information about the debugging process. The
16239 @option{--remote-debug} option tells @code{gdbserver} to display
16240 remote protocol debug output. These options are intended for
16241 @code{gdbserver} development and for bug reports to the developers.
16243 The @option{--wrapper} option specifies a wrapper to launch programs
16244 for debugging. The option should be followed by the name of the
16245 wrapper, then any command-line arguments to pass to the wrapper, then
16246 @kbd{--} indicating the end of the wrapper arguments.
16248 @code{gdbserver} runs the specified wrapper program with a combined
16249 command line including the wrapper arguments, then the name of the
16250 program to debug, then any arguments to the program. The wrapper
16251 runs until it executes your program, and then @value{GDBN} gains control.
16253 You can use any program that eventually calls @code{execve} with
16254 its arguments as a wrapper. Several standard Unix utilities do
16255 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16256 with @code{exec "$@@"} will also work.
16258 For example, you can use @code{env} to pass an environment variable to
16259 the debugged program, without setting the variable in @code{gdbserver}'s
16263 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16266 @subsection Connecting to @code{gdbserver}
16268 Run @value{GDBN} on the host system.
16270 First make sure you have the necessary symbol files. Load symbols for
16271 your application using the @code{file} command before you connect. Use
16272 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16273 was compiled with the correct sysroot using @code{--with-sysroot}).
16275 The symbol file and target libraries must exactly match the executable
16276 and libraries on the target, with one exception: the files on the host
16277 system should not be stripped, even if the files on the target system
16278 are. Mismatched or missing files will lead to confusing results
16279 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16280 files may also prevent @code{gdbserver} from debugging multi-threaded
16283 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16284 For TCP connections, you must start up @code{gdbserver} prior to using
16285 the @code{target remote} command. Otherwise you may get an error whose
16286 text depends on the host system, but which usually looks something like
16287 @samp{Connection refused}. Don't use the @code{load}
16288 command in @value{GDBN} when using @code{gdbserver}, since the program is
16289 already on the target.
16291 @subsection Monitor Commands for @code{gdbserver}
16292 @cindex monitor commands, for @code{gdbserver}
16293 @anchor{Monitor Commands for gdbserver}
16295 During a @value{GDBN} session using @code{gdbserver}, you can use the
16296 @code{monitor} command to send special requests to @code{gdbserver}.
16297 Here are the available commands.
16301 List the available monitor commands.
16303 @item monitor set debug 0
16304 @itemx monitor set debug 1
16305 Disable or enable general debugging messages.
16307 @item monitor set remote-debug 0
16308 @itemx monitor set remote-debug 1
16309 Disable or enable specific debugging messages associated with the remote
16310 protocol (@pxref{Remote Protocol}).
16312 @item monitor set libthread-db-search-path [PATH]
16313 @cindex gdbserver, search path for @code{libthread_db}
16314 When this command is issued, @var{path} is a colon-separated list of
16315 directories to search for @code{libthread_db} (@pxref{Threads,,set
16316 libthread-db-search-path}). If you omit @var{path},
16317 @samp{libthread-db-search-path} will be reset to an empty list.
16320 Tell gdbserver to exit immediately. This command should be followed by
16321 @code{disconnect} to close the debugging session. @code{gdbserver} will
16322 detach from any attached processes and kill any processes it created.
16323 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16324 of a multi-process mode debug session.
16328 @subsection Tracepoints support in @code{gdbserver}
16329 @cindex tracepoints support in @code{gdbserver}
16331 On some targets, @code{gdbserver} supports tracepoints, fast
16332 tracepoints and static tracepoints.
16334 For fast or static tracepoints to work, a special library called the
16335 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16336 This library is built and distributed as an integral part of
16337 @code{gdbserver}. In addition, support for static tracepoints
16338 requires building the in-process agent library with static tracepoints
16339 support. At present, the UST (LTTng Userspace Tracer,
16340 @url{http://lttng.org/ust}) tracing engine is supported. This support
16341 is automatically available if UST development headers are found in the
16342 standard include path when @code{gdbserver} is built, or if
16343 @code{gdbserver} was explicitly configured using @option{--with-ust}
16344 to point at such headers. You can explicitly disable the support
16345 using @option{--with-ust=no}.
16347 There are several ways to load the in-process agent in your program:
16350 @item Specifying it as dependency at link time
16352 You can link your program dynamically with the in-process agent
16353 library. On most systems, this is accomplished by adding
16354 @code{-linproctrace} to the link command.
16356 @item Using the system's preloading mechanisms
16358 You can force loading the in-process agent at startup time by using
16359 your system's support for preloading shared libraries. Many Unixes
16360 support the concept of preloading user defined libraries. In most
16361 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16362 in the environment. See also the description of @code{gdbserver}'s
16363 @option{--wrapper} command line option.
16365 @item Using @value{GDBN} to force loading the agent at run time
16367 On some systems, you can force the inferior to load a shared library,
16368 by calling a dynamic loader function in the inferior that takes care
16369 of dynamically looking up and loading a shared library. On most Unix
16370 systems, the function is @code{dlopen}. You'll use the @code{call}
16371 command for that. For example:
16374 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16377 Note that on most Unix systems, for the @code{dlopen} function to be
16378 available, the program needs to be linked with @code{-ldl}.
16381 On systems that have a userspace dynamic loader, like most Unix
16382 systems, when you connect to @code{gdbserver} using @code{target
16383 remote}, you'll find that the program is stopped at the dynamic
16384 loader's entry point, and no shared library has been loaded in the
16385 program's address space yet, including the in-process agent. In that
16386 case, before being able to use any of the fast or static tracepoints
16387 features, you need to let the loader run and load the shared
16388 libraries. The simplest way to do that is to run the program to the
16389 main procedure. E.g., if debugging a C or C@t{++} program, start
16390 @code{gdbserver} like so:
16393 $ gdbserver :9999 myprogram
16396 Start GDB and connect to @code{gdbserver} like so, and run to main:
16400 (@value{GDBP}) target remote myhost:9999
16401 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16402 (@value{GDBP}) b main
16403 (@value{GDBP}) continue
16406 The in-process tracing agent library should now be loaded into the
16407 process; you can confirm it with the @code{info sharedlibrary}
16408 command, which will list @file{libinproctrace.so} as loaded in the
16409 process. You are now ready to install fast tracepoints, list static
16410 tracepoint markers, probe static tracepoints markers, and start
16413 @node Remote Configuration
16414 @section Remote Configuration
16417 @kindex show remote
16418 This section documents the configuration options available when
16419 debugging remote programs. For the options related to the File I/O
16420 extensions of the remote protocol, see @ref{system,
16421 system-call-allowed}.
16424 @item set remoteaddresssize @var{bits}
16425 @cindex address size for remote targets
16426 @cindex bits in remote address
16427 Set the maximum size of address in a memory packet to the specified
16428 number of bits. @value{GDBN} will mask off the address bits above
16429 that number, when it passes addresses to the remote target. The
16430 default value is the number of bits in the target's address.
16432 @item show remoteaddresssize
16433 Show the current value of remote address size in bits.
16435 @item set remotebaud @var{n}
16436 @cindex baud rate for remote targets
16437 Set the baud rate for the remote serial I/O to @var{n} baud. The
16438 value is used to set the speed of the serial port used for debugging
16441 @item show remotebaud
16442 Show the current speed of the remote connection.
16444 @item set remotebreak
16445 @cindex interrupt remote programs
16446 @cindex BREAK signal instead of Ctrl-C
16447 @anchor{set remotebreak}
16448 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16449 when you type @kbd{Ctrl-c} to interrupt the program running
16450 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16451 character instead. The default is off, since most remote systems
16452 expect to see @samp{Ctrl-C} as the interrupt signal.
16454 @item show remotebreak
16455 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16456 interrupt the remote program.
16458 @item set remoteflow on
16459 @itemx set remoteflow off
16460 @kindex set remoteflow
16461 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16462 on the serial port used to communicate to the remote target.
16464 @item show remoteflow
16465 @kindex show remoteflow
16466 Show the current setting of hardware flow control.
16468 @item set remotelogbase @var{base}
16469 Set the base (a.k.a.@: radix) of logging serial protocol
16470 communications to @var{base}. Supported values of @var{base} are:
16471 @code{ascii}, @code{octal}, and @code{hex}. The default is
16474 @item show remotelogbase
16475 Show the current setting of the radix for logging remote serial
16478 @item set remotelogfile @var{file}
16479 @cindex record serial communications on file
16480 Record remote serial communications on the named @var{file}. The
16481 default is not to record at all.
16483 @item show remotelogfile.
16484 Show the current setting of the file name on which to record the
16485 serial communications.
16487 @item set remotetimeout @var{num}
16488 @cindex timeout for serial communications
16489 @cindex remote timeout
16490 Set the timeout limit to wait for the remote target to respond to
16491 @var{num} seconds. The default is 2 seconds.
16493 @item show remotetimeout
16494 Show the current number of seconds to wait for the remote target
16497 @cindex limit hardware breakpoints and watchpoints
16498 @cindex remote target, limit break- and watchpoints
16499 @anchor{set remote hardware-watchpoint-limit}
16500 @anchor{set remote hardware-breakpoint-limit}
16501 @item set remote hardware-watchpoint-limit @var{limit}
16502 @itemx set remote hardware-breakpoint-limit @var{limit}
16503 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16504 watchpoints. A limit of -1, the default, is treated as unlimited.
16506 @item set remote exec-file @var{filename}
16507 @itemx show remote exec-file
16508 @anchor{set remote exec-file}
16509 @cindex executable file, for remote target
16510 Select the file used for @code{run} with @code{target
16511 extended-remote}. This should be set to a filename valid on the
16512 target system. If it is not set, the target will use a default
16513 filename (e.g.@: the last program run).
16515 @item set remote interrupt-sequence
16516 @cindex interrupt remote programs
16517 @cindex select Ctrl-C, BREAK or BREAK-g
16518 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16519 @samp{BREAK-g} as the
16520 sequence to the remote target in order to interrupt the execution.
16521 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16522 is high level of serial line for some certain time.
16523 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16524 It is @code{BREAK} signal followed by character @code{g}.
16526 @item show interrupt-sequence
16527 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16528 is sent by @value{GDBN} to interrupt the remote program.
16529 @code{BREAK-g} is BREAK signal followed by @code{g} and
16530 also known as Magic SysRq g.
16532 @item set remote interrupt-on-connect
16533 @cindex send interrupt-sequence on start
16534 Specify whether interrupt-sequence is sent to remote target when
16535 @value{GDBN} connects to it. This is mostly needed when you debug
16536 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16537 which is known as Magic SysRq g in order to connect @value{GDBN}.
16539 @item show interrupt-on-connect
16540 Show whether interrupt-sequence is sent
16541 to remote target when @value{GDBN} connects to it.
16545 @item set tcp auto-retry on
16546 @cindex auto-retry, for remote TCP target
16547 Enable auto-retry for remote TCP connections. This is useful if the remote
16548 debugging agent is launched in parallel with @value{GDBN}; there is a race
16549 condition because the agent may not become ready to accept the connection
16550 before @value{GDBN} attempts to connect. When auto-retry is
16551 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16552 to establish the connection using the timeout specified by
16553 @code{set tcp connect-timeout}.
16555 @item set tcp auto-retry off
16556 Do not auto-retry failed TCP connections.
16558 @item show tcp auto-retry
16559 Show the current auto-retry setting.
16561 @item set tcp connect-timeout @var{seconds}
16562 @cindex connection timeout, for remote TCP target
16563 @cindex timeout, for remote target connection
16564 Set the timeout for establishing a TCP connection to the remote target to
16565 @var{seconds}. The timeout affects both polling to retry failed connections
16566 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16567 that are merely slow to complete, and represents an approximate cumulative
16570 @item show tcp connect-timeout
16571 Show the current connection timeout setting.
16574 @cindex remote packets, enabling and disabling
16575 The @value{GDBN} remote protocol autodetects the packets supported by
16576 your debugging stub. If you need to override the autodetection, you
16577 can use these commands to enable or disable individual packets. Each
16578 packet can be set to @samp{on} (the remote target supports this
16579 packet), @samp{off} (the remote target does not support this packet),
16580 or @samp{auto} (detect remote target support for this packet). They
16581 all default to @samp{auto}. For more information about each packet,
16582 see @ref{Remote Protocol}.
16584 During normal use, you should not have to use any of these commands.
16585 If you do, that may be a bug in your remote debugging stub, or a bug
16586 in @value{GDBN}. You may want to report the problem to the
16587 @value{GDBN} developers.
16589 For each packet @var{name}, the command to enable or disable the
16590 packet is @code{set remote @var{name}-packet}. The available settings
16593 @multitable @columnfractions 0.28 0.32 0.25
16596 @tab Related Features
16598 @item @code{fetch-register}
16600 @tab @code{info registers}
16602 @item @code{set-register}
16606 @item @code{binary-download}
16608 @tab @code{load}, @code{set}
16610 @item @code{read-aux-vector}
16611 @tab @code{qXfer:auxv:read}
16612 @tab @code{info auxv}
16614 @item @code{symbol-lookup}
16615 @tab @code{qSymbol}
16616 @tab Detecting multiple threads
16618 @item @code{attach}
16619 @tab @code{vAttach}
16622 @item @code{verbose-resume}
16624 @tab Stepping or resuming multiple threads
16630 @item @code{software-breakpoint}
16634 @item @code{hardware-breakpoint}
16638 @item @code{write-watchpoint}
16642 @item @code{read-watchpoint}
16646 @item @code{access-watchpoint}
16650 @item @code{target-features}
16651 @tab @code{qXfer:features:read}
16652 @tab @code{set architecture}
16654 @item @code{library-info}
16655 @tab @code{qXfer:libraries:read}
16656 @tab @code{info sharedlibrary}
16658 @item @code{memory-map}
16659 @tab @code{qXfer:memory-map:read}
16660 @tab @code{info mem}
16662 @item @code{read-sdata-object}
16663 @tab @code{qXfer:sdata:read}
16664 @tab @code{print $_sdata}
16666 @item @code{read-spu-object}
16667 @tab @code{qXfer:spu:read}
16668 @tab @code{info spu}
16670 @item @code{write-spu-object}
16671 @tab @code{qXfer:spu:write}
16672 @tab @code{info spu}
16674 @item @code{read-siginfo-object}
16675 @tab @code{qXfer:siginfo:read}
16676 @tab @code{print $_siginfo}
16678 @item @code{write-siginfo-object}
16679 @tab @code{qXfer:siginfo:write}
16680 @tab @code{set $_siginfo}
16682 @item @code{threads}
16683 @tab @code{qXfer:threads:read}
16684 @tab @code{info threads}
16686 @item @code{get-thread-local-@*storage-address}
16687 @tab @code{qGetTLSAddr}
16688 @tab Displaying @code{__thread} variables
16690 @item @code{get-thread-information-block-address}
16691 @tab @code{qGetTIBAddr}
16692 @tab Display MS-Windows Thread Information Block.
16694 @item @code{search-memory}
16695 @tab @code{qSearch:memory}
16698 @item @code{supported-packets}
16699 @tab @code{qSupported}
16700 @tab Remote communications parameters
16702 @item @code{pass-signals}
16703 @tab @code{QPassSignals}
16704 @tab @code{handle @var{signal}}
16706 @item @code{hostio-close-packet}
16707 @tab @code{vFile:close}
16708 @tab @code{remote get}, @code{remote put}
16710 @item @code{hostio-open-packet}
16711 @tab @code{vFile:open}
16712 @tab @code{remote get}, @code{remote put}
16714 @item @code{hostio-pread-packet}
16715 @tab @code{vFile:pread}
16716 @tab @code{remote get}, @code{remote put}
16718 @item @code{hostio-pwrite-packet}
16719 @tab @code{vFile:pwrite}
16720 @tab @code{remote get}, @code{remote put}
16722 @item @code{hostio-unlink-packet}
16723 @tab @code{vFile:unlink}
16724 @tab @code{remote delete}
16726 @item @code{noack-packet}
16727 @tab @code{QStartNoAckMode}
16728 @tab Packet acknowledgment
16730 @item @code{osdata}
16731 @tab @code{qXfer:osdata:read}
16732 @tab @code{info os}
16734 @item @code{query-attached}
16735 @tab @code{qAttached}
16736 @tab Querying remote process attach state.
16738 @item @code{traceframe-info}
16739 @tab @code{qXfer:traceframe-info:read}
16740 @tab Traceframe info
16744 @section Implementing a Remote Stub
16746 @cindex debugging stub, example
16747 @cindex remote stub, example
16748 @cindex stub example, remote debugging
16749 The stub files provided with @value{GDBN} implement the target side of the
16750 communication protocol, and the @value{GDBN} side is implemented in the
16751 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16752 these subroutines to communicate, and ignore the details. (If you're
16753 implementing your own stub file, you can still ignore the details: start
16754 with one of the existing stub files. @file{sparc-stub.c} is the best
16755 organized, and therefore the easiest to read.)
16757 @cindex remote serial debugging, overview
16758 To debug a program running on another machine (the debugging
16759 @dfn{target} machine), you must first arrange for all the usual
16760 prerequisites for the program to run by itself. For example, for a C
16765 A startup routine to set up the C runtime environment; these usually
16766 have a name like @file{crt0}. The startup routine may be supplied by
16767 your hardware supplier, or you may have to write your own.
16770 A C subroutine library to support your program's
16771 subroutine calls, notably managing input and output.
16774 A way of getting your program to the other machine---for example, a
16775 download program. These are often supplied by the hardware
16776 manufacturer, but you may have to write your own from hardware
16780 The next step is to arrange for your program to use a serial port to
16781 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16782 machine). In general terms, the scheme looks like this:
16786 @value{GDBN} already understands how to use this protocol; when everything
16787 else is set up, you can simply use the @samp{target remote} command
16788 (@pxref{Targets,,Specifying a Debugging Target}).
16790 @item On the target,
16791 you must link with your program a few special-purpose subroutines that
16792 implement the @value{GDBN} remote serial protocol. The file containing these
16793 subroutines is called a @dfn{debugging stub}.
16795 On certain remote targets, you can use an auxiliary program
16796 @code{gdbserver} instead of linking a stub into your program.
16797 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16800 The debugging stub is specific to the architecture of the remote
16801 machine; for example, use @file{sparc-stub.c} to debug programs on
16804 @cindex remote serial stub list
16805 These working remote stubs are distributed with @value{GDBN}:
16810 @cindex @file{i386-stub.c}
16813 For Intel 386 and compatible architectures.
16816 @cindex @file{m68k-stub.c}
16817 @cindex Motorola 680x0
16819 For Motorola 680x0 architectures.
16822 @cindex @file{sh-stub.c}
16825 For Renesas SH architectures.
16828 @cindex @file{sparc-stub.c}
16830 For @sc{sparc} architectures.
16832 @item sparcl-stub.c
16833 @cindex @file{sparcl-stub.c}
16836 For Fujitsu @sc{sparclite} architectures.
16840 The @file{README} file in the @value{GDBN} distribution may list other
16841 recently added stubs.
16844 * Stub Contents:: What the stub can do for you
16845 * Bootstrapping:: What you must do for the stub
16846 * Debug Session:: Putting it all together
16849 @node Stub Contents
16850 @subsection What the Stub Can Do for You
16852 @cindex remote serial stub
16853 The debugging stub for your architecture supplies these three
16857 @item set_debug_traps
16858 @findex set_debug_traps
16859 @cindex remote serial stub, initialization
16860 This routine arranges for @code{handle_exception} to run when your
16861 program stops. You must call this subroutine explicitly near the
16862 beginning of your program.
16864 @item handle_exception
16865 @findex handle_exception
16866 @cindex remote serial stub, main routine
16867 This is the central workhorse, but your program never calls it
16868 explicitly---the setup code arranges for @code{handle_exception} to
16869 run when a trap is triggered.
16871 @code{handle_exception} takes control when your program stops during
16872 execution (for example, on a breakpoint), and mediates communications
16873 with @value{GDBN} on the host machine. This is where the communications
16874 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16875 representative on the target machine. It begins by sending summary
16876 information on the state of your program, then continues to execute,
16877 retrieving and transmitting any information @value{GDBN} needs, until you
16878 execute a @value{GDBN} command that makes your program resume; at that point,
16879 @code{handle_exception} returns control to your own code on the target
16883 @cindex @code{breakpoint} subroutine, remote
16884 Use this auxiliary subroutine to make your program contain a
16885 breakpoint. Depending on the particular situation, this may be the only
16886 way for @value{GDBN} to get control. For instance, if your target
16887 machine has some sort of interrupt button, you won't need to call this;
16888 pressing the interrupt button transfers control to
16889 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16890 simply receiving characters on the serial port may also trigger a trap;
16891 again, in that situation, you don't need to call @code{breakpoint} from
16892 your own program---simply running @samp{target remote} from the host
16893 @value{GDBN} session gets control.
16895 Call @code{breakpoint} if none of these is true, or if you simply want
16896 to make certain your program stops at a predetermined point for the
16897 start of your debugging session.
16900 @node Bootstrapping
16901 @subsection What You Must Do for the Stub
16903 @cindex remote stub, support routines
16904 The debugging stubs that come with @value{GDBN} are set up for a particular
16905 chip architecture, but they have no information about the rest of your
16906 debugging target machine.
16908 First of all you need to tell the stub how to communicate with the
16912 @item int getDebugChar()
16913 @findex getDebugChar
16914 Write this subroutine to read a single character from the serial port.
16915 It may be identical to @code{getchar} for your target system; a
16916 different name is used to allow you to distinguish the two if you wish.
16918 @item void putDebugChar(int)
16919 @findex putDebugChar
16920 Write this subroutine to write a single character to the serial port.
16921 It may be identical to @code{putchar} for your target system; a
16922 different name is used to allow you to distinguish the two if you wish.
16925 @cindex control C, and remote debugging
16926 @cindex interrupting remote targets
16927 If you want @value{GDBN} to be able to stop your program while it is
16928 running, you need to use an interrupt-driven serial driver, and arrange
16929 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16930 character). That is the character which @value{GDBN} uses to tell the
16931 remote system to stop.
16933 Getting the debugging target to return the proper status to @value{GDBN}
16934 probably requires changes to the standard stub; one quick and dirty way
16935 is to just execute a breakpoint instruction (the ``dirty'' part is that
16936 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16938 Other routines you need to supply are:
16941 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16942 @findex exceptionHandler
16943 Write this function to install @var{exception_address} in the exception
16944 handling tables. You need to do this because the stub does not have any
16945 way of knowing what the exception handling tables on your target system
16946 are like (for example, the processor's table might be in @sc{rom},
16947 containing entries which point to a table in @sc{ram}).
16948 @var{exception_number} is the exception number which should be changed;
16949 its meaning is architecture-dependent (for example, different numbers
16950 might represent divide by zero, misaligned access, etc). When this
16951 exception occurs, control should be transferred directly to
16952 @var{exception_address}, and the processor state (stack, registers,
16953 and so on) should be just as it is when a processor exception occurs. So if
16954 you want to use a jump instruction to reach @var{exception_address}, it
16955 should be a simple jump, not a jump to subroutine.
16957 For the 386, @var{exception_address} should be installed as an interrupt
16958 gate so that interrupts are masked while the handler runs. The gate
16959 should be at privilege level 0 (the most privileged level). The
16960 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16961 help from @code{exceptionHandler}.
16963 @item void flush_i_cache()
16964 @findex flush_i_cache
16965 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16966 instruction cache, if any, on your target machine. If there is no
16967 instruction cache, this subroutine may be a no-op.
16969 On target machines that have instruction caches, @value{GDBN} requires this
16970 function to make certain that the state of your program is stable.
16974 You must also make sure this library routine is available:
16977 @item void *memset(void *, int, int)
16979 This is the standard library function @code{memset} that sets an area of
16980 memory to a known value. If you have one of the free versions of
16981 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16982 either obtain it from your hardware manufacturer, or write your own.
16985 If you do not use the GNU C compiler, you may need other standard
16986 library subroutines as well; this varies from one stub to another,
16987 but in general the stubs are likely to use any of the common library
16988 subroutines which @code{@value{NGCC}} generates as inline code.
16991 @node Debug Session
16992 @subsection Putting it All Together
16994 @cindex remote serial debugging summary
16995 In summary, when your program is ready to debug, you must follow these
17000 Make sure you have defined the supporting low-level routines
17001 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17003 @code{getDebugChar}, @code{putDebugChar},
17004 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17008 Insert these lines near the top of your program:
17016 For the 680x0 stub only, you need to provide a variable called
17017 @code{exceptionHook}. Normally you just use:
17020 void (*exceptionHook)() = 0;
17024 but if before calling @code{set_debug_traps}, you set it to point to a
17025 function in your program, that function is called when
17026 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17027 error). The function indicated by @code{exceptionHook} is called with
17028 one parameter: an @code{int} which is the exception number.
17031 Compile and link together: your program, the @value{GDBN} debugging stub for
17032 your target architecture, and the supporting subroutines.
17035 Make sure you have a serial connection between your target machine and
17036 the @value{GDBN} host, and identify the serial port on the host.
17039 @c The "remote" target now provides a `load' command, so we should
17040 @c document that. FIXME.
17041 Download your program to your target machine (or get it there by
17042 whatever means the manufacturer provides), and start it.
17045 Start @value{GDBN} on the host, and connect to the target
17046 (@pxref{Connecting,,Connecting to a Remote Target}).
17050 @node Configurations
17051 @chapter Configuration-Specific Information
17053 While nearly all @value{GDBN} commands are available for all native and
17054 cross versions of the debugger, there are some exceptions. This chapter
17055 describes things that are only available in certain configurations.
17057 There are three major categories of configurations: native
17058 configurations, where the host and target are the same, embedded
17059 operating system configurations, which are usually the same for several
17060 different processor architectures, and bare embedded processors, which
17061 are quite different from each other.
17066 * Embedded Processors::
17073 This section describes details specific to particular native
17078 * BSD libkvm Interface:: Debugging BSD kernel memory images
17079 * SVR4 Process Information:: SVR4 process information
17080 * DJGPP Native:: Features specific to the DJGPP port
17081 * Cygwin Native:: Features specific to the Cygwin port
17082 * Hurd Native:: Features specific to @sc{gnu} Hurd
17083 * Neutrino:: Features specific to QNX Neutrino
17084 * Darwin:: Features specific to Darwin
17090 On HP-UX systems, if you refer to a function or variable name that
17091 begins with a dollar sign, @value{GDBN} searches for a user or system
17092 name first, before it searches for a convenience variable.
17095 @node BSD libkvm Interface
17096 @subsection BSD libkvm Interface
17099 @cindex kernel memory image
17100 @cindex kernel crash dump
17102 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17103 interface that provides a uniform interface for accessing kernel virtual
17104 memory images, including live systems and crash dumps. @value{GDBN}
17105 uses this interface to allow you to debug live kernels and kernel crash
17106 dumps on many native BSD configurations. This is implemented as a
17107 special @code{kvm} debugging target. For debugging a live system, load
17108 the currently running kernel into @value{GDBN} and connect to the
17112 (@value{GDBP}) @b{target kvm}
17115 For debugging crash dumps, provide the file name of the crash dump as an
17119 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17122 Once connected to the @code{kvm} target, the following commands are
17128 Set current context from the @dfn{Process Control Block} (PCB) address.
17131 Set current context from proc address. This command isn't available on
17132 modern FreeBSD systems.
17135 @node SVR4 Process Information
17136 @subsection SVR4 Process Information
17138 @cindex examine process image
17139 @cindex process info via @file{/proc}
17141 Many versions of SVR4 and compatible systems provide a facility called
17142 @samp{/proc} that can be used to examine the image of a running
17143 process using file-system subroutines. If @value{GDBN} is configured
17144 for an operating system with this facility, the command @code{info
17145 proc} is available to report information about the process running
17146 your program, or about any process running on your system. @code{info
17147 proc} works only on SVR4 systems that include the @code{procfs} code.
17148 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17149 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17155 @itemx info proc @var{process-id}
17156 Summarize available information about any running process. If a
17157 process ID is specified by @var{process-id}, display information about
17158 that process; otherwise display information about the program being
17159 debugged. The summary includes the debugged process ID, the command
17160 line used to invoke it, its current working directory, and its
17161 executable file's absolute file name.
17163 On some systems, @var{process-id} can be of the form
17164 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17165 within a process. If the optional @var{pid} part is missing, it means
17166 a thread from the process being debugged (the leading @samp{/} still
17167 needs to be present, or else @value{GDBN} will interpret the number as
17168 a process ID rather than a thread ID).
17170 @item info proc mappings
17171 @cindex memory address space mappings
17172 Report the memory address space ranges accessible in the program, with
17173 information on whether the process has read, write, or execute access
17174 rights to each range. On @sc{gnu}/Linux systems, each memory range
17175 includes the object file which is mapped to that range, instead of the
17176 memory access rights to that range.
17178 @item info proc stat
17179 @itemx info proc status
17180 @cindex process detailed status information
17181 These subcommands are specific to @sc{gnu}/Linux systems. They show
17182 the process-related information, including the user ID and group ID;
17183 how many threads are there in the process; its virtual memory usage;
17184 the signals that are pending, blocked, and ignored; its TTY; its
17185 consumption of system and user time; its stack size; its @samp{nice}
17186 value; etc. For more information, see the @samp{proc} man page
17187 (type @kbd{man 5 proc} from your shell prompt).
17189 @item info proc all
17190 Show all the information about the process described under all of the
17191 above @code{info proc} subcommands.
17194 @comment These sub-options of 'info proc' were not included when
17195 @comment procfs.c was re-written. Keep their descriptions around
17196 @comment against the day when someone finds the time to put them back in.
17197 @kindex info proc times
17198 @item info proc times
17199 Starting time, user CPU time, and system CPU time for your program and
17202 @kindex info proc id
17204 Report on the process IDs related to your program: its own process ID,
17205 the ID of its parent, the process group ID, and the session ID.
17208 @item set procfs-trace
17209 @kindex set procfs-trace
17210 @cindex @code{procfs} API calls
17211 This command enables and disables tracing of @code{procfs} API calls.
17213 @item show procfs-trace
17214 @kindex show procfs-trace
17215 Show the current state of @code{procfs} API call tracing.
17217 @item set procfs-file @var{file}
17218 @kindex set procfs-file
17219 Tell @value{GDBN} to write @code{procfs} API trace to the named
17220 @var{file}. @value{GDBN} appends the trace info to the previous
17221 contents of the file. The default is to display the trace on the
17224 @item show procfs-file
17225 @kindex show procfs-file
17226 Show the file to which @code{procfs} API trace is written.
17228 @item proc-trace-entry
17229 @itemx proc-trace-exit
17230 @itemx proc-untrace-entry
17231 @itemx proc-untrace-exit
17232 @kindex proc-trace-entry
17233 @kindex proc-trace-exit
17234 @kindex proc-untrace-entry
17235 @kindex proc-untrace-exit
17236 These commands enable and disable tracing of entries into and exits
17237 from the @code{syscall} interface.
17240 @kindex info pidlist
17241 @cindex process list, QNX Neutrino
17242 For QNX Neutrino only, this command displays the list of all the
17243 processes and all the threads within each process.
17246 @kindex info meminfo
17247 @cindex mapinfo list, QNX Neutrino
17248 For QNX Neutrino only, this command displays the list of all mapinfos.
17252 @subsection Features for Debugging @sc{djgpp} Programs
17253 @cindex @sc{djgpp} debugging
17254 @cindex native @sc{djgpp} debugging
17255 @cindex MS-DOS-specific commands
17258 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17259 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17260 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17261 top of real-mode DOS systems and their emulations.
17263 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17264 defines a few commands specific to the @sc{djgpp} port. This
17265 subsection describes those commands.
17270 This is a prefix of @sc{djgpp}-specific commands which print
17271 information about the target system and important OS structures.
17274 @cindex MS-DOS system info
17275 @cindex free memory information (MS-DOS)
17276 @item info dos sysinfo
17277 This command displays assorted information about the underlying
17278 platform: the CPU type and features, the OS version and flavor, the
17279 DPMI version, and the available conventional and DPMI memory.
17284 @cindex segment descriptor tables
17285 @cindex descriptor tables display
17287 @itemx info dos ldt
17288 @itemx info dos idt
17289 These 3 commands display entries from, respectively, Global, Local,
17290 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17291 tables are data structures which store a descriptor for each segment
17292 that is currently in use. The segment's selector is an index into a
17293 descriptor table; the table entry for that index holds the
17294 descriptor's base address and limit, and its attributes and access
17297 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17298 segment (used for both data and the stack), and a DOS segment (which
17299 allows access to DOS/BIOS data structures and absolute addresses in
17300 conventional memory). However, the DPMI host will usually define
17301 additional segments in order to support the DPMI environment.
17303 @cindex garbled pointers
17304 These commands allow to display entries from the descriptor tables.
17305 Without an argument, all entries from the specified table are
17306 displayed. An argument, which should be an integer expression, means
17307 display a single entry whose index is given by the argument. For
17308 example, here's a convenient way to display information about the
17309 debugged program's data segment:
17312 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17313 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17317 This comes in handy when you want to see whether a pointer is outside
17318 the data segment's limit (i.e.@: @dfn{garbled}).
17320 @cindex page tables display (MS-DOS)
17322 @itemx info dos pte
17323 These two commands display entries from, respectively, the Page
17324 Directory and the Page Tables. Page Directories and Page Tables are
17325 data structures which control how virtual memory addresses are mapped
17326 into physical addresses. A Page Table includes an entry for every
17327 page of memory that is mapped into the program's address space; there
17328 may be several Page Tables, each one holding up to 4096 entries. A
17329 Page Directory has up to 4096 entries, one each for every Page Table
17330 that is currently in use.
17332 Without an argument, @kbd{info dos pde} displays the entire Page
17333 Directory, and @kbd{info dos pte} displays all the entries in all of
17334 the Page Tables. An argument, an integer expression, given to the
17335 @kbd{info dos pde} command means display only that entry from the Page
17336 Directory table. An argument given to the @kbd{info dos pte} command
17337 means display entries from a single Page Table, the one pointed to by
17338 the specified entry in the Page Directory.
17340 @cindex direct memory access (DMA) on MS-DOS
17341 These commands are useful when your program uses @dfn{DMA} (Direct
17342 Memory Access), which needs physical addresses to program the DMA
17345 These commands are supported only with some DPMI servers.
17347 @cindex physical address from linear address
17348 @item info dos address-pte @var{addr}
17349 This command displays the Page Table entry for a specified linear
17350 address. The argument @var{addr} is a linear address which should
17351 already have the appropriate segment's base address added to it,
17352 because this command accepts addresses which may belong to @emph{any}
17353 segment. For example, here's how to display the Page Table entry for
17354 the page where a variable @code{i} is stored:
17357 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17358 @exdent @code{Page Table entry for address 0x11a00d30:}
17359 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17363 This says that @code{i} is stored at offset @code{0xd30} from the page
17364 whose physical base address is @code{0x02698000}, and shows all the
17365 attributes of that page.
17367 Note that you must cast the addresses of variables to a @code{char *},
17368 since otherwise the value of @code{__djgpp_base_address}, the base
17369 address of all variables and functions in a @sc{djgpp} program, will
17370 be added using the rules of C pointer arithmetics: if @code{i} is
17371 declared an @code{int}, @value{GDBN} will add 4 times the value of
17372 @code{__djgpp_base_address} to the address of @code{i}.
17374 Here's another example, it displays the Page Table entry for the
17378 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17379 @exdent @code{Page Table entry for address 0x29110:}
17380 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17384 (The @code{+ 3} offset is because the transfer buffer's address is the
17385 3rd member of the @code{_go32_info_block} structure.) The output
17386 clearly shows that this DPMI server maps the addresses in conventional
17387 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17388 linear (@code{0x29110}) addresses are identical.
17390 This command is supported only with some DPMI servers.
17393 @cindex DOS serial data link, remote debugging
17394 In addition to native debugging, the DJGPP port supports remote
17395 debugging via a serial data link. The following commands are specific
17396 to remote serial debugging in the DJGPP port of @value{GDBN}.
17399 @kindex set com1base
17400 @kindex set com1irq
17401 @kindex set com2base
17402 @kindex set com2irq
17403 @kindex set com3base
17404 @kindex set com3irq
17405 @kindex set com4base
17406 @kindex set com4irq
17407 @item set com1base @var{addr}
17408 This command sets the base I/O port address of the @file{COM1} serial
17411 @item set com1irq @var{irq}
17412 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17413 for the @file{COM1} serial port.
17415 There are similar commands @samp{set com2base}, @samp{set com3irq},
17416 etc.@: for setting the port address and the @code{IRQ} lines for the
17419 @kindex show com1base
17420 @kindex show com1irq
17421 @kindex show com2base
17422 @kindex show com2irq
17423 @kindex show com3base
17424 @kindex show com3irq
17425 @kindex show com4base
17426 @kindex show com4irq
17427 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17428 display the current settings of the base address and the @code{IRQ}
17429 lines used by the COM ports.
17432 @kindex info serial
17433 @cindex DOS serial port status
17434 This command prints the status of the 4 DOS serial ports. For each
17435 port, it prints whether it's active or not, its I/O base address and
17436 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17437 counts of various errors encountered so far.
17441 @node Cygwin Native
17442 @subsection Features for Debugging MS Windows PE Executables
17443 @cindex MS Windows debugging
17444 @cindex native Cygwin debugging
17445 @cindex Cygwin-specific commands
17447 @value{GDBN} supports native debugging of MS Windows programs, including
17448 DLLs with and without symbolic debugging information.
17450 @cindex Ctrl-BREAK, MS-Windows
17451 @cindex interrupt debuggee on MS-Windows
17452 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17453 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17454 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17455 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17456 sequence, which can be used to interrupt the debuggee even if it
17459 There are various additional Cygwin-specific commands, described in
17460 this section. Working with DLLs that have no debugging symbols is
17461 described in @ref{Non-debug DLL Symbols}.
17466 This is a prefix of MS Windows-specific commands which print
17467 information about the target system and important OS structures.
17469 @item info w32 selector
17470 This command displays information returned by
17471 the Win32 API @code{GetThreadSelectorEntry} function.
17472 It takes an optional argument that is evaluated to
17473 a long value to give the information about this given selector.
17474 Without argument, this command displays information
17475 about the six segment registers.
17477 @item info w32 thread-information-block
17478 This command displays thread specific information stored in the
17479 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17480 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17484 This is a Cygwin-specific alias of @code{info shared}.
17486 @kindex dll-symbols
17488 This command loads symbols from a dll similarly to
17489 add-sym command but without the need to specify a base address.
17491 @kindex set cygwin-exceptions
17492 @cindex debugging the Cygwin DLL
17493 @cindex Cygwin DLL, debugging
17494 @item set cygwin-exceptions @var{mode}
17495 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17496 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17497 @value{GDBN} will delay recognition of exceptions, and may ignore some
17498 exceptions which seem to be caused by internal Cygwin DLL
17499 ``bookkeeping''. This option is meant primarily for debugging the
17500 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17501 @value{GDBN} users with false @code{SIGSEGV} signals.
17503 @kindex show cygwin-exceptions
17504 @item show cygwin-exceptions
17505 Displays whether @value{GDBN} will break on exceptions that happen
17506 inside the Cygwin DLL itself.
17508 @kindex set new-console
17509 @item set new-console @var{mode}
17510 If @var{mode} is @code{on} the debuggee will
17511 be started in a new console on next start.
17512 If @var{mode} is @code{off}, the debuggee will
17513 be started in the same console as the debugger.
17515 @kindex show new-console
17516 @item show new-console
17517 Displays whether a new console is used
17518 when the debuggee is started.
17520 @kindex set new-group
17521 @item set new-group @var{mode}
17522 This boolean value controls whether the debuggee should
17523 start a new group or stay in the same group as the debugger.
17524 This affects the way the Windows OS handles
17527 @kindex show new-group
17528 @item show new-group
17529 Displays current value of new-group boolean.
17531 @kindex set debugevents
17532 @item set debugevents
17533 This boolean value adds debug output concerning kernel events related
17534 to the debuggee seen by the debugger. This includes events that
17535 signal thread and process creation and exit, DLL loading and
17536 unloading, console interrupts, and debugging messages produced by the
17537 Windows @code{OutputDebugString} API call.
17539 @kindex set debugexec
17540 @item set debugexec
17541 This boolean value adds debug output concerning execute events
17542 (such as resume thread) seen by the debugger.
17544 @kindex set debugexceptions
17545 @item set debugexceptions
17546 This boolean value adds debug output concerning exceptions in the
17547 debuggee seen by the debugger.
17549 @kindex set debugmemory
17550 @item set debugmemory
17551 This boolean value adds debug output concerning debuggee memory reads
17552 and writes by the debugger.
17556 This boolean values specifies whether the debuggee is called
17557 via a shell or directly (default value is on).
17561 Displays if the debuggee will be started with a shell.
17566 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17569 @node Non-debug DLL Symbols
17570 @subsubsection Support for DLLs without Debugging Symbols
17571 @cindex DLLs with no debugging symbols
17572 @cindex Minimal symbols and DLLs
17574 Very often on windows, some of the DLLs that your program relies on do
17575 not include symbolic debugging information (for example,
17576 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17577 symbols in a DLL, it relies on the minimal amount of symbolic
17578 information contained in the DLL's export table. This section
17579 describes working with such symbols, known internally to @value{GDBN} as
17580 ``minimal symbols''.
17582 Note that before the debugged program has started execution, no DLLs
17583 will have been loaded. The easiest way around this problem is simply to
17584 start the program --- either by setting a breakpoint or letting the
17585 program run once to completion. It is also possible to force
17586 @value{GDBN} to load a particular DLL before starting the executable ---
17587 see the shared library information in @ref{Files}, or the
17588 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17589 explicitly loading symbols from a DLL with no debugging information will
17590 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17591 which may adversely affect symbol lookup performance.
17593 @subsubsection DLL Name Prefixes
17595 In keeping with the naming conventions used by the Microsoft debugging
17596 tools, DLL export symbols are made available with a prefix based on the
17597 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17598 also entered into the symbol table, so @code{CreateFileA} is often
17599 sufficient. In some cases there will be name clashes within a program
17600 (particularly if the executable itself includes full debugging symbols)
17601 necessitating the use of the fully qualified name when referring to the
17602 contents of the DLL. Use single-quotes around the name to avoid the
17603 exclamation mark (``!'') being interpreted as a language operator.
17605 Note that the internal name of the DLL may be all upper-case, even
17606 though the file name of the DLL is lower-case, or vice-versa. Since
17607 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17608 some confusion. If in doubt, try the @code{info functions} and
17609 @code{info variables} commands or even @code{maint print msymbols}
17610 (@pxref{Symbols}). Here's an example:
17613 (@value{GDBP}) info function CreateFileA
17614 All functions matching regular expression "CreateFileA":
17616 Non-debugging symbols:
17617 0x77e885f4 CreateFileA
17618 0x77e885f4 KERNEL32!CreateFileA
17622 (@value{GDBP}) info function !
17623 All functions matching regular expression "!":
17625 Non-debugging symbols:
17626 0x6100114c cygwin1!__assert
17627 0x61004034 cygwin1!_dll_crt0@@0
17628 0x61004240 cygwin1!dll_crt0(per_process *)
17632 @subsubsection Working with Minimal Symbols
17634 Symbols extracted from a DLL's export table do not contain very much
17635 type information. All that @value{GDBN} can do is guess whether a symbol
17636 refers to a function or variable depending on the linker section that
17637 contains the symbol. Also note that the actual contents of the memory
17638 contained in a DLL are not available unless the program is running. This
17639 means that you cannot examine the contents of a variable or disassemble
17640 a function within a DLL without a running program.
17642 Variables are generally treated as pointers and dereferenced
17643 automatically. For this reason, it is often necessary to prefix a
17644 variable name with the address-of operator (``&'') and provide explicit
17645 type information in the command. Here's an example of the type of
17649 (@value{GDBP}) print 'cygwin1!__argv'
17654 (@value{GDBP}) x 'cygwin1!__argv'
17655 0x10021610: "\230y\""
17658 And two possible solutions:
17661 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17662 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17666 (@value{GDBP}) x/2x &'cygwin1!__argv'
17667 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17668 (@value{GDBP}) x/x 0x10021608
17669 0x10021608: 0x0022fd98
17670 (@value{GDBP}) x/s 0x0022fd98
17671 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17674 Setting a break point within a DLL is possible even before the program
17675 starts execution. However, under these circumstances, @value{GDBN} can't
17676 examine the initial instructions of the function in order to skip the
17677 function's frame set-up code. You can work around this by using ``*&''
17678 to set the breakpoint at a raw memory address:
17681 (@value{GDBP}) break *&'python22!PyOS_Readline'
17682 Breakpoint 1 at 0x1e04eff0
17685 The author of these extensions is not entirely convinced that setting a
17686 break point within a shared DLL like @file{kernel32.dll} is completely
17690 @subsection Commands Specific to @sc{gnu} Hurd Systems
17691 @cindex @sc{gnu} Hurd debugging
17693 This subsection describes @value{GDBN} commands specific to the
17694 @sc{gnu} Hurd native debugging.
17699 @kindex set signals@r{, Hurd command}
17700 @kindex set sigs@r{, Hurd command}
17701 This command toggles the state of inferior signal interception by
17702 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17703 affected by this command. @code{sigs} is a shorthand alias for
17708 @kindex show signals@r{, Hurd command}
17709 @kindex show sigs@r{, Hurd command}
17710 Show the current state of intercepting inferior's signals.
17712 @item set signal-thread
17713 @itemx set sigthread
17714 @kindex set signal-thread
17715 @kindex set sigthread
17716 This command tells @value{GDBN} which thread is the @code{libc} signal
17717 thread. That thread is run when a signal is delivered to a running
17718 process. @code{set sigthread} is the shorthand alias of @code{set
17721 @item show signal-thread
17722 @itemx show sigthread
17723 @kindex show signal-thread
17724 @kindex show sigthread
17725 These two commands show which thread will run when the inferior is
17726 delivered a signal.
17729 @kindex set stopped@r{, Hurd command}
17730 This commands tells @value{GDBN} that the inferior process is stopped,
17731 as with the @code{SIGSTOP} signal. The stopped process can be
17732 continued by delivering a signal to it.
17735 @kindex show stopped@r{, Hurd command}
17736 This command shows whether @value{GDBN} thinks the debuggee is
17739 @item set exceptions
17740 @kindex set exceptions@r{, Hurd command}
17741 Use this command to turn off trapping of exceptions in the inferior.
17742 When exception trapping is off, neither breakpoints nor
17743 single-stepping will work. To restore the default, set exception
17746 @item show exceptions
17747 @kindex show exceptions@r{, Hurd command}
17748 Show the current state of trapping exceptions in the inferior.
17750 @item set task pause
17751 @kindex set task@r{, Hurd commands}
17752 @cindex task attributes (@sc{gnu} Hurd)
17753 @cindex pause current task (@sc{gnu} Hurd)
17754 This command toggles task suspension when @value{GDBN} has control.
17755 Setting it to on takes effect immediately, and the task is suspended
17756 whenever @value{GDBN} gets control. Setting it to off will take
17757 effect the next time the inferior is continued. If this option is set
17758 to off, you can use @code{set thread default pause on} or @code{set
17759 thread pause on} (see below) to pause individual threads.
17761 @item show task pause
17762 @kindex show task@r{, Hurd commands}
17763 Show the current state of task suspension.
17765 @item set task detach-suspend-count
17766 @cindex task suspend count
17767 @cindex detach from task, @sc{gnu} Hurd
17768 This command sets the suspend count the task will be left with when
17769 @value{GDBN} detaches from it.
17771 @item show task detach-suspend-count
17772 Show the suspend count the task will be left with when detaching.
17774 @item set task exception-port
17775 @itemx set task excp
17776 @cindex task exception port, @sc{gnu} Hurd
17777 This command sets the task exception port to which @value{GDBN} will
17778 forward exceptions. The argument should be the value of the @dfn{send
17779 rights} of the task. @code{set task excp} is a shorthand alias.
17781 @item set noninvasive
17782 @cindex noninvasive task options
17783 This command switches @value{GDBN} to a mode that is the least
17784 invasive as far as interfering with the inferior is concerned. This
17785 is the same as using @code{set task pause}, @code{set exceptions}, and
17786 @code{set signals} to values opposite to the defaults.
17788 @item info send-rights
17789 @itemx info receive-rights
17790 @itemx info port-rights
17791 @itemx info port-sets
17792 @itemx info dead-names
17795 @cindex send rights, @sc{gnu} Hurd
17796 @cindex receive rights, @sc{gnu} Hurd
17797 @cindex port rights, @sc{gnu} Hurd
17798 @cindex port sets, @sc{gnu} Hurd
17799 @cindex dead names, @sc{gnu} Hurd
17800 These commands display information about, respectively, send rights,
17801 receive rights, port rights, port sets, and dead names of a task.
17802 There are also shorthand aliases: @code{info ports} for @code{info
17803 port-rights} and @code{info psets} for @code{info port-sets}.
17805 @item set thread pause
17806 @kindex set thread@r{, Hurd command}
17807 @cindex thread properties, @sc{gnu} Hurd
17808 @cindex pause current thread (@sc{gnu} Hurd)
17809 This command toggles current thread suspension when @value{GDBN} has
17810 control. Setting it to on takes effect immediately, and the current
17811 thread is suspended whenever @value{GDBN} gets control. Setting it to
17812 off will take effect the next time the inferior is continued.
17813 Normally, this command has no effect, since when @value{GDBN} has
17814 control, the whole task is suspended. However, if you used @code{set
17815 task pause off} (see above), this command comes in handy to suspend
17816 only the current thread.
17818 @item show thread pause
17819 @kindex show thread@r{, Hurd command}
17820 This command shows the state of current thread suspension.
17822 @item set thread run
17823 This command sets whether the current thread is allowed to run.
17825 @item show thread run
17826 Show whether the current thread is allowed to run.
17828 @item set thread detach-suspend-count
17829 @cindex thread suspend count, @sc{gnu} Hurd
17830 @cindex detach from thread, @sc{gnu} Hurd
17831 This command sets the suspend count @value{GDBN} will leave on a
17832 thread when detaching. This number is relative to the suspend count
17833 found by @value{GDBN} when it notices the thread; use @code{set thread
17834 takeover-suspend-count} to force it to an absolute value.
17836 @item show thread detach-suspend-count
17837 Show the suspend count @value{GDBN} will leave on the thread when
17840 @item set thread exception-port
17841 @itemx set thread excp
17842 Set the thread exception port to which to forward exceptions. This
17843 overrides the port set by @code{set task exception-port} (see above).
17844 @code{set thread excp} is the shorthand alias.
17846 @item set thread takeover-suspend-count
17847 Normally, @value{GDBN}'s thread suspend counts are relative to the
17848 value @value{GDBN} finds when it notices each thread. This command
17849 changes the suspend counts to be absolute instead.
17851 @item set thread default
17852 @itemx show thread default
17853 @cindex thread default settings, @sc{gnu} Hurd
17854 Each of the above @code{set thread} commands has a @code{set thread
17855 default} counterpart (e.g., @code{set thread default pause}, @code{set
17856 thread default exception-port}, etc.). The @code{thread default}
17857 variety of commands sets the default thread properties for all
17858 threads; you can then change the properties of individual threads with
17859 the non-default commands.
17864 @subsection QNX Neutrino
17865 @cindex QNX Neutrino
17867 @value{GDBN} provides the following commands specific to the QNX
17871 @item set debug nto-debug
17872 @kindex set debug nto-debug
17873 When set to on, enables debugging messages specific to the QNX
17876 @item show debug nto-debug
17877 @kindex show debug nto-debug
17878 Show the current state of QNX Neutrino messages.
17885 @value{GDBN} provides the following commands specific to the Darwin target:
17888 @item set debug darwin @var{num}
17889 @kindex set debug darwin
17890 When set to a non zero value, enables debugging messages specific to
17891 the Darwin support. Higher values produce more verbose output.
17893 @item show debug darwin
17894 @kindex show debug darwin
17895 Show the current state of Darwin messages.
17897 @item set debug mach-o @var{num}
17898 @kindex set debug mach-o
17899 When set to a non zero value, enables debugging messages while
17900 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17901 file format used on Darwin for object and executable files.) Higher
17902 values produce more verbose output. This is a command to diagnose
17903 problems internal to @value{GDBN} and should not be needed in normal
17906 @item show debug mach-o
17907 @kindex show debug mach-o
17908 Show the current state of Mach-O file messages.
17910 @item set mach-exceptions on
17911 @itemx set mach-exceptions off
17912 @kindex set mach-exceptions
17913 On Darwin, faults are first reported as a Mach exception and are then
17914 mapped to a Posix signal. Use this command to turn on trapping of
17915 Mach exceptions in the inferior. This might be sometimes useful to
17916 better understand the cause of a fault. The default is off.
17918 @item show mach-exceptions
17919 @kindex show mach-exceptions
17920 Show the current state of exceptions trapping.
17925 @section Embedded Operating Systems
17927 This section describes configurations involving the debugging of
17928 embedded operating systems that are available for several different
17932 * VxWorks:: Using @value{GDBN} with VxWorks
17935 @value{GDBN} includes the ability to debug programs running on
17936 various real-time operating systems.
17939 @subsection Using @value{GDBN} with VxWorks
17945 @kindex target vxworks
17946 @item target vxworks @var{machinename}
17947 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17948 is the target system's machine name or IP address.
17952 On VxWorks, @code{load} links @var{filename} dynamically on the
17953 current target system as well as adding its symbols in @value{GDBN}.
17955 @value{GDBN} enables developers to spawn and debug tasks running on networked
17956 VxWorks targets from a Unix host. Already-running tasks spawned from
17957 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17958 both the Unix host and on the VxWorks target. The program
17959 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17960 installed with the name @code{vxgdb}, to distinguish it from a
17961 @value{GDBN} for debugging programs on the host itself.)
17964 @item VxWorks-timeout @var{args}
17965 @kindex vxworks-timeout
17966 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17967 This option is set by the user, and @var{args} represents the number of
17968 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17969 your VxWorks target is a slow software simulator or is on the far side
17970 of a thin network line.
17973 The following information on connecting to VxWorks was current when
17974 this manual was produced; newer releases of VxWorks may use revised
17977 @findex INCLUDE_RDB
17978 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17979 to include the remote debugging interface routines in the VxWorks
17980 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17981 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17982 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17983 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17984 information on configuring and remaking VxWorks, see the manufacturer's
17986 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17988 Once you have included @file{rdb.a} in your VxWorks system image and set
17989 your Unix execution search path to find @value{GDBN}, you are ready to
17990 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17991 @code{vxgdb}, depending on your installation).
17993 @value{GDBN} comes up showing the prompt:
18000 * VxWorks Connection:: Connecting to VxWorks
18001 * VxWorks Download:: VxWorks download
18002 * VxWorks Attach:: Running tasks
18005 @node VxWorks Connection
18006 @subsubsection Connecting to VxWorks
18008 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18009 network. To connect to a target whose host name is ``@code{tt}'', type:
18012 (vxgdb) target vxworks tt
18016 @value{GDBN} displays messages like these:
18019 Attaching remote machine across net...
18024 @value{GDBN} then attempts to read the symbol tables of any object modules
18025 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18026 these files by searching the directories listed in the command search
18027 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18028 to find an object file, it displays a message such as:
18031 prog.o: No such file or directory.
18034 When this happens, add the appropriate directory to the search path with
18035 the @value{GDBN} command @code{path}, and execute the @code{target}
18038 @node VxWorks Download
18039 @subsubsection VxWorks Download
18041 @cindex download to VxWorks
18042 If you have connected to the VxWorks target and you want to debug an
18043 object that has not yet been loaded, you can use the @value{GDBN}
18044 @code{load} command to download a file from Unix to VxWorks
18045 incrementally. The object file given as an argument to the @code{load}
18046 command is actually opened twice: first by the VxWorks target in order
18047 to download the code, then by @value{GDBN} in order to read the symbol
18048 table. This can lead to problems if the current working directories on
18049 the two systems differ. If both systems have NFS mounted the same
18050 filesystems, you can avoid these problems by using absolute paths.
18051 Otherwise, it is simplest to set the working directory on both systems
18052 to the directory in which the object file resides, and then to reference
18053 the file by its name, without any path. For instance, a program
18054 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18055 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18056 program, type this on VxWorks:
18059 -> cd "@var{vxpath}/vw/demo/rdb"
18063 Then, in @value{GDBN}, type:
18066 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18067 (vxgdb) load prog.o
18070 @value{GDBN} displays a response similar to this:
18073 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18076 You can also use the @code{load} command to reload an object module
18077 after editing and recompiling the corresponding source file. Note that
18078 this makes @value{GDBN} delete all currently-defined breakpoints,
18079 auto-displays, and convenience variables, and to clear the value
18080 history. (This is necessary in order to preserve the integrity of
18081 debugger's data structures that reference the target system's symbol
18084 @node VxWorks Attach
18085 @subsubsection Running Tasks
18087 @cindex running VxWorks tasks
18088 You can also attach to an existing task using the @code{attach} command as
18092 (vxgdb) attach @var{task}
18096 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18097 or suspended when you attach to it. Running tasks are suspended at
18098 the time of attachment.
18100 @node Embedded Processors
18101 @section Embedded Processors
18103 This section goes into details specific to particular embedded
18106 @cindex send command to simulator
18107 Whenever a specific embedded processor has a simulator, @value{GDBN}
18108 allows to send an arbitrary command to the simulator.
18111 @item sim @var{command}
18112 @kindex sim@r{, a command}
18113 Send an arbitrary @var{command} string to the simulator. Consult the
18114 documentation for the specific simulator in use for information about
18115 acceptable commands.
18121 * M32R/D:: Renesas M32R/D
18122 * M68K:: Motorola M68K
18123 * MicroBlaze:: Xilinx MicroBlaze
18124 * MIPS Embedded:: MIPS Embedded
18125 * OpenRISC 1000:: OpenRisc 1000
18126 * PA:: HP PA Embedded
18127 * PowerPC Embedded:: PowerPC Embedded
18128 * Sparclet:: Tsqware Sparclet
18129 * Sparclite:: Fujitsu Sparclite
18130 * Z8000:: Zilog Z8000
18133 * Super-H:: Renesas Super-H
18142 @item target rdi @var{dev}
18143 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18144 use this target to communicate with both boards running the Angel
18145 monitor, or with the EmbeddedICE JTAG debug device.
18148 @item target rdp @var{dev}
18153 @value{GDBN} provides the following ARM-specific commands:
18156 @item set arm disassembler
18158 This commands selects from a list of disassembly styles. The
18159 @code{"std"} style is the standard style.
18161 @item show arm disassembler
18163 Show the current disassembly style.
18165 @item set arm apcs32
18166 @cindex ARM 32-bit mode
18167 This command toggles ARM operation mode between 32-bit and 26-bit.
18169 @item show arm apcs32
18170 Display the current usage of the ARM 32-bit mode.
18172 @item set arm fpu @var{fputype}
18173 This command sets the ARM floating-point unit (FPU) type. The
18174 argument @var{fputype} can be one of these:
18178 Determine the FPU type by querying the OS ABI.
18180 Software FPU, with mixed-endian doubles on little-endian ARM
18183 GCC-compiled FPA co-processor.
18185 Software FPU with pure-endian doubles.
18191 Show the current type of the FPU.
18194 This command forces @value{GDBN} to use the specified ABI.
18197 Show the currently used ABI.
18199 @item set arm fallback-mode (arm|thumb|auto)
18200 @value{GDBN} uses the symbol table, when available, to determine
18201 whether instructions are ARM or Thumb. This command controls
18202 @value{GDBN}'s default behavior when the symbol table is not
18203 available. The default is @samp{auto}, which causes @value{GDBN} to
18204 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18207 @item show arm fallback-mode
18208 Show the current fallback instruction mode.
18210 @item set arm force-mode (arm|thumb|auto)
18211 This command overrides use of the symbol table to determine whether
18212 instructions are ARM or Thumb. The default is @samp{auto}, which
18213 causes @value{GDBN} to use the symbol table and then the setting
18214 of @samp{set arm fallback-mode}.
18216 @item show arm force-mode
18217 Show the current forced instruction mode.
18219 @item set debug arm
18220 Toggle whether to display ARM-specific debugging messages from the ARM
18221 target support subsystem.
18223 @item show debug arm
18224 Show whether ARM-specific debugging messages are enabled.
18227 The following commands are available when an ARM target is debugged
18228 using the RDI interface:
18231 @item rdilogfile @r{[}@var{file}@r{]}
18233 @cindex ADP (Angel Debugger Protocol) logging
18234 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18235 With an argument, sets the log file to the specified @var{file}. With
18236 no argument, show the current log file name. The default log file is
18239 @item rdilogenable @r{[}@var{arg}@r{]}
18240 @kindex rdilogenable
18241 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18242 enables logging, with an argument 0 or @code{"no"} disables it. With
18243 no arguments displays the current setting. When logging is enabled,
18244 ADP packets exchanged between @value{GDBN} and the RDI target device
18245 are logged to a file.
18247 @item set rdiromatzero
18248 @kindex set rdiromatzero
18249 @cindex ROM at zero address, RDI
18250 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18251 vector catching is disabled, so that zero address can be used. If off
18252 (the default), vector catching is enabled. For this command to take
18253 effect, it needs to be invoked prior to the @code{target rdi} command.
18255 @item show rdiromatzero
18256 @kindex show rdiromatzero
18257 Show the current setting of ROM at zero address.
18259 @item set rdiheartbeat
18260 @kindex set rdiheartbeat
18261 @cindex RDI heartbeat
18262 Enable or disable RDI heartbeat packets. It is not recommended to
18263 turn on this option, since it confuses ARM and EPI JTAG interface, as
18264 well as the Angel monitor.
18266 @item show rdiheartbeat
18267 @kindex show rdiheartbeat
18268 Show the setting of RDI heartbeat packets.
18272 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18273 The @value{GDBN} ARM simulator accepts the following optional arguments.
18276 @item --swi-support=@var{type}
18277 Tell the simulator which SWI interfaces to support.
18278 @var{type} may be a comma separated list of the following values.
18279 The default value is @code{all}.
18292 @subsection Renesas M32R/D and M32R/SDI
18295 @kindex target m32r
18296 @item target m32r @var{dev}
18297 Renesas M32R/D ROM monitor.
18299 @kindex target m32rsdi
18300 @item target m32rsdi @var{dev}
18301 Renesas M32R SDI server, connected via parallel port to the board.
18304 The following @value{GDBN} commands are specific to the M32R monitor:
18307 @item set download-path @var{path}
18308 @kindex set download-path
18309 @cindex find downloadable @sc{srec} files (M32R)
18310 Set the default path for finding downloadable @sc{srec} files.
18312 @item show download-path
18313 @kindex show download-path
18314 Show the default path for downloadable @sc{srec} files.
18316 @item set board-address @var{addr}
18317 @kindex set board-address
18318 @cindex M32-EVA target board address
18319 Set the IP address for the M32R-EVA target board.
18321 @item show board-address
18322 @kindex show board-address
18323 Show the current IP address of the target board.
18325 @item set server-address @var{addr}
18326 @kindex set server-address
18327 @cindex download server address (M32R)
18328 Set the IP address for the download server, which is the @value{GDBN}'s
18331 @item show server-address
18332 @kindex show server-address
18333 Display the IP address of the download server.
18335 @item upload @r{[}@var{file}@r{]}
18336 @kindex upload@r{, M32R}
18337 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18338 upload capability. If no @var{file} argument is given, the current
18339 executable file is uploaded.
18341 @item tload @r{[}@var{file}@r{]}
18342 @kindex tload@r{, M32R}
18343 Test the @code{upload} command.
18346 The following commands are available for M32R/SDI:
18351 @cindex reset SDI connection, M32R
18352 This command resets the SDI connection.
18356 This command shows the SDI connection status.
18359 @kindex debug_chaos
18360 @cindex M32R/Chaos debugging
18361 Instructs the remote that M32R/Chaos debugging is to be used.
18363 @item use_debug_dma
18364 @kindex use_debug_dma
18365 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18368 @kindex use_mon_code
18369 Instructs the remote to use the MON_CODE method of accessing memory.
18372 @kindex use_ib_break
18373 Instructs the remote to set breakpoints by IB break.
18375 @item use_dbt_break
18376 @kindex use_dbt_break
18377 Instructs the remote to set breakpoints by DBT.
18383 The Motorola m68k configuration includes ColdFire support, and a
18384 target command for the following ROM monitor.
18388 @kindex target dbug
18389 @item target dbug @var{dev}
18390 dBUG ROM monitor for Motorola ColdFire.
18395 @subsection MicroBlaze
18396 @cindex Xilinx MicroBlaze
18397 @cindex XMD, Xilinx Microprocessor Debugger
18399 The MicroBlaze is a soft-core processor supported on various Xilinx
18400 FPGAs, such as Spartan or Virtex series. Boards with these processors
18401 usually have JTAG ports which connect to a host system running the Xilinx
18402 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18403 This host system is used to download the configuration bitstream to
18404 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18405 communicates with the target board using the JTAG interface and
18406 presents a @code{gdbserver} interface to the board. By default
18407 @code{xmd} uses port @code{1234}. (While it is possible to change
18408 this default port, it requires the use of undocumented @code{xmd}
18409 commands. Contact Xilinx support if you need to do this.)
18411 Use these GDB commands to connect to the MicroBlaze target processor.
18414 @item target remote :1234
18415 Use this command to connect to the target if you are running @value{GDBN}
18416 on the same system as @code{xmd}.
18418 @item target remote @var{xmd-host}:1234
18419 Use this command to connect to the target if it is connected to @code{xmd}
18420 running on a different system named @var{xmd-host}.
18423 Use this command to download a program to the MicroBlaze target.
18425 @item set debug microblaze @var{n}
18426 Enable MicroBlaze-specific debugging messages if non-zero.
18428 @item show debug microblaze @var{n}
18429 Show MicroBlaze-specific debugging level.
18432 @node MIPS Embedded
18433 @subsection MIPS Embedded
18435 @cindex MIPS boards
18436 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18437 MIPS board attached to a serial line. This is available when
18438 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18441 Use these @value{GDBN} commands to specify the connection to your target board:
18444 @item target mips @var{port}
18445 @kindex target mips @var{port}
18446 To run a program on the board, start up @code{@value{GDBP}} with the
18447 name of your program as the argument. To connect to the board, use the
18448 command @samp{target mips @var{port}}, where @var{port} is the name of
18449 the serial port connected to the board. If the program has not already
18450 been downloaded to the board, you may use the @code{load} command to
18451 download it. You can then use all the usual @value{GDBN} commands.
18453 For example, this sequence connects to the target board through a serial
18454 port, and loads and runs a program called @var{prog} through the
18458 host$ @value{GDBP} @var{prog}
18459 @value{GDBN} is free software and @dots{}
18460 (@value{GDBP}) target mips /dev/ttyb
18461 (@value{GDBP}) load @var{prog}
18465 @item target mips @var{hostname}:@var{portnumber}
18466 On some @value{GDBN} host configurations, you can specify a TCP
18467 connection (for instance, to a serial line managed by a terminal
18468 concentrator) instead of a serial port, using the syntax
18469 @samp{@var{hostname}:@var{portnumber}}.
18471 @item target pmon @var{port}
18472 @kindex target pmon @var{port}
18475 @item target ddb @var{port}
18476 @kindex target ddb @var{port}
18477 NEC's DDB variant of PMON for Vr4300.
18479 @item target lsi @var{port}
18480 @kindex target lsi @var{port}
18481 LSI variant of PMON.
18483 @kindex target r3900
18484 @item target r3900 @var{dev}
18485 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18487 @kindex target array
18488 @item target array @var{dev}
18489 Array Tech LSI33K RAID controller board.
18495 @value{GDBN} also supports these special commands for MIPS targets:
18498 @item set mipsfpu double
18499 @itemx set mipsfpu single
18500 @itemx set mipsfpu none
18501 @itemx set mipsfpu auto
18502 @itemx show mipsfpu
18503 @kindex set mipsfpu
18504 @kindex show mipsfpu
18505 @cindex MIPS remote floating point
18506 @cindex floating point, MIPS remote
18507 If your target board does not support the MIPS floating point
18508 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18509 need this, you may wish to put the command in your @value{GDBN} init
18510 file). This tells @value{GDBN} how to find the return value of
18511 functions which return floating point values. It also allows
18512 @value{GDBN} to avoid saving the floating point registers when calling
18513 functions on the board. If you are using a floating point coprocessor
18514 with only single precision floating point support, as on the @sc{r4650}
18515 processor, use the command @samp{set mipsfpu single}. The default
18516 double precision floating point coprocessor may be selected using
18517 @samp{set mipsfpu double}.
18519 In previous versions the only choices were double precision or no
18520 floating point, so @samp{set mipsfpu on} will select double precision
18521 and @samp{set mipsfpu off} will select no floating point.
18523 As usual, you can inquire about the @code{mipsfpu} variable with
18524 @samp{show mipsfpu}.
18526 @item set timeout @var{seconds}
18527 @itemx set retransmit-timeout @var{seconds}
18528 @itemx show timeout
18529 @itemx show retransmit-timeout
18530 @cindex @code{timeout}, MIPS protocol
18531 @cindex @code{retransmit-timeout}, MIPS protocol
18532 @kindex set timeout
18533 @kindex show timeout
18534 @kindex set retransmit-timeout
18535 @kindex show retransmit-timeout
18536 You can control the timeout used while waiting for a packet, in the MIPS
18537 remote protocol, with the @code{set timeout @var{seconds}} command. The
18538 default is 5 seconds. Similarly, you can control the timeout used while
18539 waiting for an acknowledgment of a packet with the @code{set
18540 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18541 You can inspect both values with @code{show timeout} and @code{show
18542 retransmit-timeout}. (These commands are @emph{only} available when
18543 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18545 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18546 is waiting for your program to stop. In that case, @value{GDBN} waits
18547 forever because it has no way of knowing how long the program is going
18548 to run before stopping.
18550 @item set syn-garbage-limit @var{num}
18551 @kindex set syn-garbage-limit@r{, MIPS remote}
18552 @cindex synchronize with remote MIPS target
18553 Limit the maximum number of characters @value{GDBN} should ignore when
18554 it tries to synchronize with the remote target. The default is 10
18555 characters. Setting the limit to -1 means there's no limit.
18557 @item show syn-garbage-limit
18558 @kindex show syn-garbage-limit@r{, MIPS remote}
18559 Show the current limit on the number of characters to ignore when
18560 trying to synchronize with the remote system.
18562 @item set monitor-prompt @var{prompt}
18563 @kindex set monitor-prompt@r{, MIPS remote}
18564 @cindex remote monitor prompt
18565 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18566 remote monitor. The default depends on the target:
18576 @item show monitor-prompt
18577 @kindex show monitor-prompt@r{, MIPS remote}
18578 Show the current strings @value{GDBN} expects as the prompt from the
18581 @item set monitor-warnings
18582 @kindex set monitor-warnings@r{, MIPS remote}
18583 Enable or disable monitor warnings about hardware breakpoints. This
18584 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18585 display warning messages whose codes are returned by the @code{lsi}
18586 PMON monitor for breakpoint commands.
18588 @item show monitor-warnings
18589 @kindex show monitor-warnings@r{, MIPS remote}
18590 Show the current setting of printing monitor warnings.
18592 @item pmon @var{command}
18593 @kindex pmon@r{, MIPS remote}
18594 @cindex send PMON command
18595 This command allows sending an arbitrary @var{command} string to the
18596 monitor. The monitor must be in debug mode for this to work.
18599 @node OpenRISC 1000
18600 @subsection OpenRISC 1000
18601 @cindex OpenRISC 1000
18603 @cindex or1k boards
18604 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18605 about platform and commands.
18609 @kindex target jtag
18610 @item target jtag jtag://@var{host}:@var{port}
18612 Connects to remote JTAG server.
18613 JTAG remote server can be either an or1ksim or JTAG server,
18614 connected via parallel port to the board.
18616 Example: @code{target jtag jtag://localhost:9999}
18619 @item or1ksim @var{command}
18620 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18621 Simulator, proprietary commands can be executed.
18623 @kindex info or1k spr
18624 @item info or1k spr
18625 Displays spr groups.
18627 @item info or1k spr @var{group}
18628 @itemx info or1k spr @var{groupno}
18629 Displays register names in selected group.
18631 @item info or1k spr @var{group} @var{register}
18632 @itemx info or1k spr @var{register}
18633 @itemx info or1k spr @var{groupno} @var{registerno}
18634 @itemx info or1k spr @var{registerno}
18635 Shows information about specified spr register.
18638 @item spr @var{group} @var{register} @var{value}
18639 @itemx spr @var{register @var{value}}
18640 @itemx spr @var{groupno} @var{registerno @var{value}}
18641 @itemx spr @var{registerno @var{value}}
18642 Writes @var{value} to specified spr register.
18645 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18646 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18647 program execution and is thus much faster. Hardware breakpoints/watchpoint
18648 triggers can be set using:
18651 Load effective address/data
18653 Store effective address/data
18655 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18660 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18661 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18663 @code{htrace} commands:
18664 @cindex OpenRISC 1000 htrace
18667 @item hwatch @var{conditional}
18668 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18669 or Data. For example:
18671 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18673 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18677 Display information about current HW trace configuration.
18679 @item htrace trigger @var{conditional}
18680 Set starting criteria for HW trace.
18682 @item htrace qualifier @var{conditional}
18683 Set acquisition qualifier for HW trace.
18685 @item htrace stop @var{conditional}
18686 Set HW trace stopping criteria.
18688 @item htrace record [@var{data}]*
18689 Selects the data to be recorded, when qualifier is met and HW trace was
18692 @item htrace enable
18693 @itemx htrace disable
18694 Enables/disables the HW trace.
18696 @item htrace rewind [@var{filename}]
18697 Clears currently recorded trace data.
18699 If filename is specified, new trace file is made and any newly collected data
18700 will be written there.
18702 @item htrace print [@var{start} [@var{len}]]
18703 Prints trace buffer, using current record configuration.
18705 @item htrace mode continuous
18706 Set continuous trace mode.
18708 @item htrace mode suspend
18709 Set suspend trace mode.
18713 @node PowerPC Embedded
18714 @subsection PowerPC Embedded
18716 @cindex DVC register
18717 @value{GDBN} supports using the DVC (Data Value Compare) register to
18718 implement in hardware simple hardware watchpoint conditions of the form:
18721 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18722 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18725 The DVC register will be automatically used when @value{GDBN} detects
18726 such pattern in a condition expression, and the created watchpoint uses one
18727 debug register (either the @code{exact-watchpoints} option is on and the
18728 variable is scalar, or the variable has a length of one byte). This feature
18729 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18732 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18733 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18734 in which case watchpoints using only one debug register are created when
18735 watching variables of scalar types.
18737 You can create an artificial array to watch an arbitrary memory
18738 region using one of the following commands (@pxref{Expressions}):
18741 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18742 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18745 @cindex ranged breakpoint
18746 PowerPC embedded processors support hardware accelerated
18747 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18748 the inferior whenever it executes an instruction at any address within
18749 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18750 use the @code{break-range} command.
18752 @value{GDBN} provides the following PowerPC-specific commands:
18755 @kindex break-range
18756 @item break-range @var{start-location}, @var{end-location}
18757 Set a breakpoint for an address range.
18758 @var{start-location} and @var{end-location} can specify a function name,
18759 a line number, an offset of lines from the current line or from the start
18760 location, or an address of an instruction (see @ref{Specify Location},
18761 for a list of all the possible ways to specify a @var{location}.)
18762 The breakpoint will stop execution of the inferior whenever it
18763 executes an instruction at any address within the specified range,
18764 (including @var{start-location} and @var{end-location}.)
18766 @kindex set powerpc
18767 @item set powerpc soft-float
18768 @itemx show powerpc soft-float
18769 Force @value{GDBN} to use (or not use) a software floating point calling
18770 convention. By default, @value{GDBN} selects the calling convention based
18771 on the selected architecture and the provided executable file.
18773 @item set powerpc vector-abi
18774 @itemx show powerpc vector-abi
18775 Force @value{GDBN} to use the specified calling convention for vector
18776 arguments and return values. The valid options are @samp{auto};
18777 @samp{generic}, to avoid vector registers even if they are present;
18778 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18779 registers. By default, @value{GDBN} selects the calling convention
18780 based on the selected architecture and the provided executable file.
18782 @item set powerpc exact-watchpoints
18783 @itemx show powerpc exact-watchpoints
18784 Allow @value{GDBN} to use only one debug register when watching a variable
18785 of scalar type, thus assuming that the variable is accessed through the
18786 address of its first byte.
18788 @kindex target dink32
18789 @item target dink32 @var{dev}
18790 DINK32 ROM monitor.
18792 @kindex target ppcbug
18793 @item target ppcbug @var{dev}
18794 @kindex target ppcbug1
18795 @item target ppcbug1 @var{dev}
18796 PPCBUG ROM monitor for PowerPC.
18799 @item target sds @var{dev}
18800 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18803 @cindex SDS protocol
18804 The following commands specific to the SDS protocol are supported
18808 @item set sdstimeout @var{nsec}
18809 @kindex set sdstimeout
18810 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18811 default is 2 seconds.
18813 @item show sdstimeout
18814 @kindex show sdstimeout
18815 Show the current value of the SDS timeout.
18817 @item sds @var{command}
18818 @kindex sds@r{, a command}
18819 Send the specified @var{command} string to the SDS monitor.
18824 @subsection HP PA Embedded
18828 @kindex target op50n
18829 @item target op50n @var{dev}
18830 OP50N monitor, running on an OKI HPPA board.
18832 @kindex target w89k
18833 @item target w89k @var{dev}
18834 W89K monitor, running on a Winbond HPPA board.
18839 @subsection Tsqware Sparclet
18843 @value{GDBN} enables developers to debug tasks running on
18844 Sparclet targets from a Unix host.
18845 @value{GDBN} uses code that runs on
18846 both the Unix host and on the Sparclet target. The program
18847 @code{@value{GDBP}} is installed and executed on the Unix host.
18850 @item remotetimeout @var{args}
18851 @kindex remotetimeout
18852 @value{GDBN} supports the option @code{remotetimeout}.
18853 This option is set by the user, and @var{args} represents the number of
18854 seconds @value{GDBN} waits for responses.
18857 @cindex compiling, on Sparclet
18858 When compiling for debugging, include the options @samp{-g} to get debug
18859 information and @samp{-Ttext} to relocate the program to where you wish to
18860 load it on the target. You may also want to add the options @samp{-n} or
18861 @samp{-N} in order to reduce the size of the sections. Example:
18864 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18867 You can use @code{objdump} to verify that the addresses are what you intended:
18870 sparclet-aout-objdump --headers --syms prog
18873 @cindex running, on Sparclet
18875 your Unix execution search path to find @value{GDBN}, you are ready to
18876 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18877 (or @code{sparclet-aout-gdb}, depending on your installation).
18879 @value{GDBN} comes up showing the prompt:
18886 * Sparclet File:: Setting the file to debug
18887 * Sparclet Connection:: Connecting to Sparclet
18888 * Sparclet Download:: Sparclet download
18889 * Sparclet Execution:: Running and debugging
18892 @node Sparclet File
18893 @subsubsection Setting File to Debug
18895 The @value{GDBN} command @code{file} lets you choose with program to debug.
18898 (gdbslet) file prog
18902 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18903 @value{GDBN} locates
18904 the file by searching the directories listed in the command search
18906 If the file was compiled with debug information (option @samp{-g}), source
18907 files will be searched as well.
18908 @value{GDBN} locates
18909 the source files by searching the directories listed in the directory search
18910 path (@pxref{Environment, ,Your Program's Environment}).
18912 to find a file, it displays a message such as:
18915 prog: No such file or directory.
18918 When this happens, add the appropriate directories to the search paths with
18919 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18920 @code{target} command again.
18922 @node Sparclet Connection
18923 @subsubsection Connecting to Sparclet
18925 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18926 To connect to a target on serial port ``@code{ttya}'', type:
18929 (gdbslet) target sparclet /dev/ttya
18930 Remote target sparclet connected to /dev/ttya
18931 main () at ../prog.c:3
18935 @value{GDBN} displays messages like these:
18941 @node Sparclet Download
18942 @subsubsection Sparclet Download
18944 @cindex download to Sparclet
18945 Once connected to the Sparclet target,
18946 you can use the @value{GDBN}
18947 @code{load} command to download the file from the host to the target.
18948 The file name and load offset should be given as arguments to the @code{load}
18950 Since the file format is aout, the program must be loaded to the starting
18951 address. You can use @code{objdump} to find out what this value is. The load
18952 offset is an offset which is added to the VMA (virtual memory address)
18953 of each of the file's sections.
18954 For instance, if the program
18955 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18956 and bss at 0x12010170, in @value{GDBN}, type:
18959 (gdbslet) load prog 0x12010000
18960 Loading section .text, size 0xdb0 vma 0x12010000
18963 If the code is loaded at a different address then what the program was linked
18964 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18965 to tell @value{GDBN} where to map the symbol table.
18967 @node Sparclet Execution
18968 @subsubsection Running and Debugging
18970 @cindex running and debugging Sparclet programs
18971 You can now begin debugging the task using @value{GDBN}'s execution control
18972 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18973 manual for the list of commands.
18977 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18979 Starting program: prog
18980 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18981 3 char *symarg = 0;
18983 4 char *execarg = "hello!";
18988 @subsection Fujitsu Sparclite
18992 @kindex target sparclite
18993 @item target sparclite @var{dev}
18994 Fujitsu sparclite boards, used only for the purpose of loading.
18995 You must use an additional command to debug the program.
18996 For example: target remote @var{dev} using @value{GDBN} standard
19002 @subsection Zilog Z8000
19005 @cindex simulator, Z8000
19006 @cindex Zilog Z8000 simulator
19008 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19011 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19012 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19013 segmented variant). The simulator recognizes which architecture is
19014 appropriate by inspecting the object code.
19017 @item target sim @var{args}
19019 @kindex target sim@r{, with Z8000}
19020 Debug programs on a simulated CPU. If the simulator supports setup
19021 options, specify them via @var{args}.
19025 After specifying this target, you can debug programs for the simulated
19026 CPU in the same style as programs for your host computer; use the
19027 @code{file} command to load a new program image, the @code{run} command
19028 to run your program, and so on.
19030 As well as making available all the usual machine registers
19031 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19032 additional items of information as specially named registers:
19037 Counts clock-ticks in the simulator.
19040 Counts instructions run in the simulator.
19043 Execution time in 60ths of a second.
19047 You can refer to these values in @value{GDBN} expressions with the usual
19048 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19049 conditional breakpoint that suspends only after at least 5000
19050 simulated clock ticks.
19053 @subsection Atmel AVR
19056 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19057 following AVR-specific commands:
19060 @item info io_registers
19061 @kindex info io_registers@r{, AVR}
19062 @cindex I/O registers (Atmel AVR)
19063 This command displays information about the AVR I/O registers. For
19064 each register, @value{GDBN} prints its number and value.
19071 When configured for debugging CRIS, @value{GDBN} provides the
19072 following CRIS-specific commands:
19075 @item set cris-version @var{ver}
19076 @cindex CRIS version
19077 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19078 The CRIS version affects register names and sizes. This command is useful in
19079 case autodetection of the CRIS version fails.
19081 @item show cris-version
19082 Show the current CRIS version.
19084 @item set cris-dwarf2-cfi
19085 @cindex DWARF-2 CFI and CRIS
19086 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19087 Change to @samp{off} when using @code{gcc-cris} whose version is below
19090 @item show cris-dwarf2-cfi
19091 Show the current state of using DWARF-2 CFI.
19093 @item set cris-mode @var{mode}
19095 Set the current CRIS mode to @var{mode}. It should only be changed when
19096 debugging in guru mode, in which case it should be set to
19097 @samp{guru} (the default is @samp{normal}).
19099 @item show cris-mode
19100 Show the current CRIS mode.
19104 @subsection Renesas Super-H
19107 For the Renesas Super-H processor, @value{GDBN} provides these
19112 @kindex regs@r{, Super-H}
19113 Show the values of all Super-H registers.
19115 @item set sh calling-convention @var{convention}
19116 @kindex set sh calling-convention
19117 Set the calling-convention used when calling functions from @value{GDBN}.
19118 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19119 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19120 convention. If the DWARF-2 information of the called function specifies
19121 that the function follows the Renesas calling convention, the function
19122 is called using the Renesas calling convention. If the calling convention
19123 is set to @samp{renesas}, the Renesas calling convention is always used,
19124 regardless of the DWARF-2 information. This can be used to override the
19125 default of @samp{gcc} if debug information is missing, or the compiler
19126 does not emit the DWARF-2 calling convention entry for a function.
19128 @item show sh calling-convention
19129 @kindex show sh calling-convention
19130 Show the current calling convention setting.
19135 @node Architectures
19136 @section Architectures
19138 This section describes characteristics of architectures that affect
19139 all uses of @value{GDBN} with the architecture, both native and cross.
19146 * HPPA:: HP PA architecture
19147 * SPU:: Cell Broadband Engine SPU architecture
19152 @subsection x86 Architecture-specific Issues
19155 @item set struct-convention @var{mode}
19156 @kindex set struct-convention
19157 @cindex struct return convention
19158 @cindex struct/union returned in registers
19159 Set the convention used by the inferior to return @code{struct}s and
19160 @code{union}s from functions to @var{mode}. Possible values of
19161 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19162 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19163 are returned on the stack, while @code{"reg"} means that a
19164 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19165 be returned in a register.
19167 @item show struct-convention
19168 @kindex show struct-convention
19169 Show the current setting of the convention to return @code{struct}s
19178 @kindex set rstack_high_address
19179 @cindex AMD 29K register stack
19180 @cindex register stack, AMD29K
19181 @item set rstack_high_address @var{address}
19182 On AMD 29000 family processors, registers are saved in a separate
19183 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19184 extent of this stack. Normally, @value{GDBN} just assumes that the
19185 stack is ``large enough''. This may result in @value{GDBN} referencing
19186 memory locations that do not exist. If necessary, you can get around
19187 this problem by specifying the ending address of the register stack with
19188 the @code{set rstack_high_address} command. The argument should be an
19189 address, which you probably want to precede with @samp{0x} to specify in
19192 @kindex show rstack_high_address
19193 @item show rstack_high_address
19194 Display the current limit of the register stack, on AMD 29000 family
19202 See the following section.
19207 @cindex stack on Alpha
19208 @cindex stack on MIPS
19209 @cindex Alpha stack
19211 Alpha- and MIPS-based computers use an unusual stack frame, which
19212 sometimes requires @value{GDBN} to search backward in the object code to
19213 find the beginning of a function.
19215 @cindex response time, MIPS debugging
19216 To improve response time (especially for embedded applications, where
19217 @value{GDBN} may be restricted to a slow serial line for this search)
19218 you may want to limit the size of this search, using one of these
19222 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19223 @item set heuristic-fence-post @var{limit}
19224 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19225 search for the beginning of a function. A value of @var{0} (the
19226 default) means there is no limit. However, except for @var{0}, the
19227 larger the limit the more bytes @code{heuristic-fence-post} must search
19228 and therefore the longer it takes to run. You should only need to use
19229 this command when debugging a stripped executable.
19231 @item show heuristic-fence-post
19232 Display the current limit.
19236 These commands are available @emph{only} when @value{GDBN} is configured
19237 for debugging programs on Alpha or MIPS processors.
19239 Several MIPS-specific commands are available when debugging MIPS
19243 @item set mips abi @var{arg}
19244 @kindex set mips abi
19245 @cindex set ABI for MIPS
19246 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19247 values of @var{arg} are:
19251 The default ABI associated with the current binary (this is the
19262 @item show mips abi
19263 @kindex show mips abi
19264 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19267 @itemx show mipsfpu
19268 @xref{MIPS Embedded, set mipsfpu}.
19270 @item set mips mask-address @var{arg}
19271 @kindex set mips mask-address
19272 @cindex MIPS addresses, masking
19273 This command determines whether the most-significant 32 bits of 64-bit
19274 MIPS addresses are masked off. The argument @var{arg} can be
19275 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19276 setting, which lets @value{GDBN} determine the correct value.
19278 @item show mips mask-address
19279 @kindex show mips mask-address
19280 Show whether the upper 32 bits of MIPS addresses are masked off or
19283 @item set remote-mips64-transfers-32bit-regs
19284 @kindex set remote-mips64-transfers-32bit-regs
19285 This command controls compatibility with 64-bit MIPS targets that
19286 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19287 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19288 and 64 bits for other registers, set this option to @samp{on}.
19290 @item show remote-mips64-transfers-32bit-regs
19291 @kindex show remote-mips64-transfers-32bit-regs
19292 Show the current setting of compatibility with older MIPS 64 targets.
19294 @item set debug mips
19295 @kindex set debug mips
19296 This command turns on and off debugging messages for the MIPS-specific
19297 target code in @value{GDBN}.
19299 @item show debug mips
19300 @kindex show debug mips
19301 Show the current setting of MIPS debugging messages.
19307 @cindex HPPA support
19309 When @value{GDBN} is debugging the HP PA architecture, it provides the
19310 following special commands:
19313 @item set debug hppa
19314 @kindex set debug hppa
19315 This command determines whether HPPA architecture-specific debugging
19316 messages are to be displayed.
19318 @item show debug hppa
19319 Show whether HPPA debugging messages are displayed.
19321 @item maint print unwind @var{address}
19322 @kindex maint print unwind@r{, HPPA}
19323 This command displays the contents of the unwind table entry at the
19324 given @var{address}.
19330 @subsection Cell Broadband Engine SPU architecture
19331 @cindex Cell Broadband Engine
19334 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19335 it provides the following special commands:
19338 @item info spu event
19340 Display SPU event facility status. Shows current event mask
19341 and pending event status.
19343 @item info spu signal
19344 Display SPU signal notification facility status. Shows pending
19345 signal-control word and signal notification mode of both signal
19346 notification channels.
19348 @item info spu mailbox
19349 Display SPU mailbox facility status. Shows all pending entries,
19350 in order of processing, in each of the SPU Write Outbound,
19351 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19354 Display MFC DMA status. Shows all pending commands in the MFC
19355 DMA queue. For each entry, opcode, tag, class IDs, effective
19356 and local store addresses and transfer size are shown.
19358 @item info spu proxydma
19359 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19360 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19361 and local store addresses and transfer size are shown.
19365 When @value{GDBN} is debugging a combined PowerPC/SPU application
19366 on the Cell Broadband Engine, it provides in addition the following
19370 @item set spu stop-on-load @var{arg}
19372 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19373 will give control to the user when a new SPE thread enters its @code{main}
19374 function. The default is @code{off}.
19376 @item show spu stop-on-load
19378 Show whether to stop for new SPE threads.
19380 @item set spu auto-flush-cache @var{arg}
19381 Set whether to automatically flush the software-managed cache. When set to
19382 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19383 cache to be flushed whenever SPE execution stops. This provides a consistent
19384 view of PowerPC memory that is accessed via the cache. If an application
19385 does not use the software-managed cache, this option has no effect.
19387 @item show spu auto-flush-cache
19388 Show whether to automatically flush the software-managed cache.
19393 @subsection PowerPC
19394 @cindex PowerPC architecture
19396 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19397 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19398 numbers stored in the floating point registers. These values must be stored
19399 in two consecutive registers, always starting at an even register like
19400 @code{f0} or @code{f2}.
19402 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19403 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19404 @code{f2} and @code{f3} for @code{$dl1} and so on.
19406 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19407 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19410 @node Controlling GDB
19411 @chapter Controlling @value{GDBN}
19413 You can alter the way @value{GDBN} interacts with you by using the
19414 @code{set} command. For commands controlling how @value{GDBN} displays
19415 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19420 * Editing:: Command editing
19421 * Command History:: Command history
19422 * Screen Size:: Screen size
19423 * Numbers:: Numbers
19424 * ABI:: Configuring the current ABI
19425 * Messages/Warnings:: Optional warnings and messages
19426 * Debugging Output:: Optional messages about internal happenings
19427 * Other Misc Settings:: Other Miscellaneous Settings
19435 @value{GDBN} indicates its readiness to read a command by printing a string
19436 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19437 can change the prompt string with the @code{set prompt} command. For
19438 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19439 the prompt in one of the @value{GDBN} sessions so that you can always tell
19440 which one you are talking to.
19442 @emph{Note:} @code{set prompt} does not add a space for you after the
19443 prompt you set. This allows you to set a prompt which ends in a space
19444 or a prompt that does not.
19448 @item set prompt @var{newprompt}
19449 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19451 @kindex show prompt
19453 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19457 @section Command Editing
19459 @cindex command line editing
19461 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19462 @sc{gnu} library provides consistent behavior for programs which provide a
19463 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19464 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19465 substitution, and a storage and recall of command history across
19466 debugging sessions.
19468 You may control the behavior of command line editing in @value{GDBN} with the
19469 command @code{set}.
19472 @kindex set editing
19475 @itemx set editing on
19476 Enable command line editing (enabled by default).
19478 @item set editing off
19479 Disable command line editing.
19481 @kindex show editing
19483 Show whether command line editing is enabled.
19486 @ifset SYSTEM_READLINE
19487 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19489 @ifclear SYSTEM_READLINE
19490 @xref{Command Line Editing},
19492 for more details about the Readline
19493 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19494 encouraged to read that chapter.
19496 @node Command History
19497 @section Command History
19498 @cindex command history
19500 @value{GDBN} can keep track of the commands you type during your
19501 debugging sessions, so that you can be certain of precisely what
19502 happened. Use these commands to manage the @value{GDBN} command
19505 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19506 package, to provide the history facility.
19507 @ifset SYSTEM_READLINE
19508 @xref{Using History Interactively, , , history, GNU History Library},
19510 @ifclear SYSTEM_READLINE
19511 @xref{Using History Interactively},
19513 for the detailed description of the History library.
19515 To issue a command to @value{GDBN} without affecting certain aspects of
19516 the state which is seen by users, prefix it with @samp{server }
19517 (@pxref{Server Prefix}). This
19518 means that this command will not affect the command history, nor will it
19519 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19520 pressed on a line by itself.
19522 @cindex @code{server}, command prefix
19523 The server prefix does not affect the recording of values into the value
19524 history; to print a value without recording it into the value history,
19525 use the @code{output} command instead of the @code{print} command.
19527 Here is the description of @value{GDBN} commands related to command
19531 @cindex history substitution
19532 @cindex history file
19533 @kindex set history filename
19534 @cindex @env{GDBHISTFILE}, environment variable
19535 @item set history filename @var{fname}
19536 Set the name of the @value{GDBN} command history file to @var{fname}.
19537 This is the file where @value{GDBN} reads an initial command history
19538 list, and where it writes the command history from this session when it
19539 exits. You can access this list through history expansion or through
19540 the history command editing characters listed below. This file defaults
19541 to the value of the environment variable @code{GDBHISTFILE}, or to
19542 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19545 @cindex save command history
19546 @kindex set history save
19547 @item set history save
19548 @itemx set history save on
19549 Record command history in a file, whose name may be specified with the
19550 @code{set history filename} command. By default, this option is disabled.
19552 @item set history save off
19553 Stop recording command history in a file.
19555 @cindex history size
19556 @kindex set history size
19557 @cindex @env{HISTSIZE}, environment variable
19558 @item set history size @var{size}
19559 Set the number of commands which @value{GDBN} keeps in its history list.
19560 This defaults to the value of the environment variable
19561 @code{HISTSIZE}, or to 256 if this variable is not set.
19564 History expansion assigns special meaning to the character @kbd{!}.
19565 @ifset SYSTEM_READLINE
19566 @xref{Event Designators, , , history, GNU History Library},
19568 @ifclear SYSTEM_READLINE
19569 @xref{Event Designators},
19573 @cindex history expansion, turn on/off
19574 Since @kbd{!} is also the logical not operator in C, history expansion
19575 is off by default. If you decide to enable history expansion with the
19576 @code{set history expansion on} command, you may sometimes need to
19577 follow @kbd{!} (when it is used as logical not, in an expression) with
19578 a space or a tab to prevent it from being expanded. The readline
19579 history facilities do not attempt substitution on the strings
19580 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19582 The commands to control history expansion are:
19585 @item set history expansion on
19586 @itemx set history expansion
19587 @kindex set history expansion
19588 Enable history expansion. History expansion is off by default.
19590 @item set history expansion off
19591 Disable history expansion.
19594 @kindex show history
19596 @itemx show history filename
19597 @itemx show history save
19598 @itemx show history size
19599 @itemx show history expansion
19600 These commands display the state of the @value{GDBN} history parameters.
19601 @code{show history} by itself displays all four states.
19606 @kindex show commands
19607 @cindex show last commands
19608 @cindex display command history
19609 @item show commands
19610 Display the last ten commands in the command history.
19612 @item show commands @var{n}
19613 Print ten commands centered on command number @var{n}.
19615 @item show commands +
19616 Print ten commands just after the commands last printed.
19620 @section Screen Size
19621 @cindex size of screen
19622 @cindex pauses in output
19624 Certain commands to @value{GDBN} may produce large amounts of
19625 information output to the screen. To help you read all of it,
19626 @value{GDBN} pauses and asks you for input at the end of each page of
19627 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19628 to discard the remaining output. Also, the screen width setting
19629 determines when to wrap lines of output. Depending on what is being
19630 printed, @value{GDBN} tries to break the line at a readable place,
19631 rather than simply letting it overflow onto the following line.
19633 Normally @value{GDBN} knows the size of the screen from the terminal
19634 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19635 together with the value of the @code{TERM} environment variable and the
19636 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19637 you can override it with the @code{set height} and @code{set
19644 @kindex show height
19645 @item set height @var{lpp}
19647 @itemx set width @var{cpl}
19649 These @code{set} commands specify a screen height of @var{lpp} lines and
19650 a screen width of @var{cpl} characters. The associated @code{show}
19651 commands display the current settings.
19653 If you specify a height of zero lines, @value{GDBN} does not pause during
19654 output no matter how long the output is. This is useful if output is to a
19655 file or to an editor buffer.
19657 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19658 from wrapping its output.
19660 @item set pagination on
19661 @itemx set pagination off
19662 @kindex set pagination
19663 Turn the output pagination on or off; the default is on. Turning
19664 pagination off is the alternative to @code{set height 0}. Note that
19665 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19666 Options, -batch}) also automatically disables pagination.
19668 @item show pagination
19669 @kindex show pagination
19670 Show the current pagination mode.
19675 @cindex number representation
19676 @cindex entering numbers
19678 You can always enter numbers in octal, decimal, or hexadecimal in
19679 @value{GDBN} by the usual conventions: octal numbers begin with
19680 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19681 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19682 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19683 10; likewise, the default display for numbers---when no particular
19684 format is specified---is base 10. You can change the default base for
19685 both input and output with the commands described below.
19688 @kindex set input-radix
19689 @item set input-radix @var{base}
19690 Set the default base for numeric input. Supported choices
19691 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19692 specified either unambiguously or using the current input radix; for
19696 set input-radix 012
19697 set input-radix 10.
19698 set input-radix 0xa
19702 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19703 leaves the input radix unchanged, no matter what it was, since
19704 @samp{10}, being without any leading or trailing signs of its base, is
19705 interpreted in the current radix. Thus, if the current radix is 16,
19706 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19709 @kindex set output-radix
19710 @item set output-radix @var{base}
19711 Set the default base for numeric display. Supported choices
19712 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19713 specified either unambiguously or using the current input radix.
19715 @kindex show input-radix
19716 @item show input-radix
19717 Display the current default base for numeric input.
19719 @kindex show output-radix
19720 @item show output-radix
19721 Display the current default base for numeric display.
19723 @item set radix @r{[}@var{base}@r{]}
19727 These commands set and show the default base for both input and output
19728 of numbers. @code{set radix} sets the radix of input and output to
19729 the same base; without an argument, it resets the radix back to its
19730 default value of 10.
19735 @section Configuring the Current ABI
19737 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19738 application automatically. However, sometimes you need to override its
19739 conclusions. Use these commands to manage @value{GDBN}'s view of the
19746 One @value{GDBN} configuration can debug binaries for multiple operating
19747 system targets, either via remote debugging or native emulation.
19748 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19749 but you can override its conclusion using the @code{set osabi} command.
19750 One example where this is useful is in debugging of binaries which use
19751 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19752 not have the same identifying marks that the standard C library for your
19757 Show the OS ABI currently in use.
19760 With no argument, show the list of registered available OS ABI's.
19762 @item set osabi @var{abi}
19763 Set the current OS ABI to @var{abi}.
19766 @cindex float promotion
19768 Generally, the way that an argument of type @code{float} is passed to a
19769 function depends on whether the function is prototyped. For a prototyped
19770 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19771 according to the architecture's convention for @code{float}. For unprototyped
19772 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19773 @code{double} and then passed.
19775 Unfortunately, some forms of debug information do not reliably indicate whether
19776 a function is prototyped. If @value{GDBN} calls a function that is not marked
19777 as prototyped, it consults @kbd{set coerce-float-to-double}.
19780 @kindex set coerce-float-to-double
19781 @item set coerce-float-to-double
19782 @itemx set coerce-float-to-double on
19783 Arguments of type @code{float} will be promoted to @code{double} when passed
19784 to an unprototyped function. This is the default setting.
19786 @item set coerce-float-to-double off
19787 Arguments of type @code{float} will be passed directly to unprototyped
19790 @kindex show coerce-float-to-double
19791 @item show coerce-float-to-double
19792 Show the current setting of promoting @code{float} to @code{double}.
19796 @kindex show cp-abi
19797 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19798 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19799 used to build your application. @value{GDBN} only fully supports
19800 programs with a single C@t{++} ABI; if your program contains code using
19801 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19802 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19803 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19804 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19805 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19806 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19811 Show the C@t{++} ABI currently in use.
19814 With no argument, show the list of supported C@t{++} ABI's.
19816 @item set cp-abi @var{abi}
19817 @itemx set cp-abi auto
19818 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19821 @node Messages/Warnings
19822 @section Optional Warnings and Messages
19824 @cindex verbose operation
19825 @cindex optional warnings
19826 By default, @value{GDBN} is silent about its inner workings. If you are
19827 running on a slow machine, you may want to use the @code{set verbose}
19828 command. This makes @value{GDBN} tell you when it does a lengthy
19829 internal operation, so you will not think it has crashed.
19831 Currently, the messages controlled by @code{set verbose} are those
19832 which announce that the symbol table for a source file is being read;
19833 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19836 @kindex set verbose
19837 @item set verbose on
19838 Enables @value{GDBN} output of certain informational messages.
19840 @item set verbose off
19841 Disables @value{GDBN} output of certain informational messages.
19843 @kindex show verbose
19845 Displays whether @code{set verbose} is on or off.
19848 By default, if @value{GDBN} encounters bugs in the symbol table of an
19849 object file, it is silent; but if you are debugging a compiler, you may
19850 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19855 @kindex set complaints
19856 @item set complaints @var{limit}
19857 Permits @value{GDBN} to output @var{limit} complaints about each type of
19858 unusual symbols before becoming silent about the problem. Set
19859 @var{limit} to zero to suppress all complaints; set it to a large number
19860 to prevent complaints from being suppressed.
19862 @kindex show complaints
19863 @item show complaints
19864 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19868 @anchor{confirmation requests}
19869 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19870 lot of stupid questions to confirm certain commands. For example, if
19871 you try to run a program which is already running:
19875 The program being debugged has been started already.
19876 Start it from the beginning? (y or n)
19879 If you are willing to unflinchingly face the consequences of your own
19880 commands, you can disable this ``feature'':
19884 @kindex set confirm
19886 @cindex confirmation
19887 @cindex stupid questions
19888 @item set confirm off
19889 Disables confirmation requests. Note that running @value{GDBN} with
19890 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19891 automatically disables confirmation requests.
19893 @item set confirm on
19894 Enables confirmation requests (the default).
19896 @kindex show confirm
19898 Displays state of confirmation requests.
19902 @cindex command tracing
19903 If you need to debug user-defined commands or sourced files you may find it
19904 useful to enable @dfn{command tracing}. In this mode each command will be
19905 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19906 quantity denoting the call depth of each command.
19909 @kindex set trace-commands
19910 @cindex command scripts, debugging
19911 @item set trace-commands on
19912 Enable command tracing.
19913 @item set trace-commands off
19914 Disable command tracing.
19915 @item show trace-commands
19916 Display the current state of command tracing.
19919 @node Debugging Output
19920 @section Optional Messages about Internal Happenings
19921 @cindex optional debugging messages
19923 @value{GDBN} has commands that enable optional debugging messages from
19924 various @value{GDBN} subsystems; normally these commands are of
19925 interest to @value{GDBN} maintainers, or when reporting a bug. This
19926 section documents those commands.
19929 @kindex set exec-done-display
19930 @item set exec-done-display
19931 Turns on or off the notification of asynchronous commands'
19932 completion. When on, @value{GDBN} will print a message when an
19933 asynchronous command finishes its execution. The default is off.
19934 @kindex show exec-done-display
19935 @item show exec-done-display
19936 Displays the current setting of asynchronous command completion
19939 @cindex gdbarch debugging info
19940 @cindex architecture debugging info
19941 @item set debug arch
19942 Turns on or off display of gdbarch debugging info. The default is off
19944 @item show debug arch
19945 Displays the current state of displaying gdbarch debugging info.
19946 @item set debug aix-thread
19947 @cindex AIX threads
19948 Display debugging messages about inner workings of the AIX thread
19950 @item show debug aix-thread
19951 Show the current state of AIX thread debugging info display.
19952 @item set debug dwarf2-die
19953 @cindex DWARF2 DIEs
19954 Dump DWARF2 DIEs after they are read in.
19955 The value is the number of nesting levels to print.
19956 A value of zero turns off the display.
19957 @item show debug dwarf2-die
19958 Show the current state of DWARF2 DIE debugging.
19959 @item set debug displaced
19960 @cindex displaced stepping debugging info
19961 Turns on or off display of @value{GDBN} debugging info for the
19962 displaced stepping support. The default is off.
19963 @item show debug displaced
19964 Displays the current state of displaying @value{GDBN} debugging info
19965 related to displaced stepping.
19966 @item set debug event
19967 @cindex event debugging info
19968 Turns on or off display of @value{GDBN} event debugging info. The
19970 @item show debug event
19971 Displays the current state of displaying @value{GDBN} event debugging
19973 @item set debug expression
19974 @cindex expression debugging info
19975 Turns on or off display of debugging info about @value{GDBN}
19976 expression parsing. The default is off.
19977 @item show debug expression
19978 Displays the current state of displaying debugging info about
19979 @value{GDBN} expression parsing.
19980 @item set debug frame
19981 @cindex frame debugging info
19982 Turns on or off display of @value{GDBN} frame debugging info. The
19984 @item show debug frame
19985 Displays the current state of displaying @value{GDBN} frame debugging
19987 @item set debug gnu-nat
19988 @cindex @sc{gnu}/Hurd debug messages
19989 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19990 @item show debug gnu-nat
19991 Show the current state of @sc{gnu}/Hurd debugging messages.
19992 @item set debug infrun
19993 @cindex inferior debugging info
19994 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19995 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19996 for implementing operations such as single-stepping the inferior.
19997 @item show debug infrun
19998 Displays the current state of @value{GDBN} inferior debugging.
19999 @item set debug jit
20000 @cindex just-in-time compilation, debugging messages
20001 Turns on or off debugging messages from JIT debug support.
20002 @item show debug jit
20003 Displays the current state of @value{GDBN} JIT debugging.
20004 @item set debug lin-lwp
20005 @cindex @sc{gnu}/Linux LWP debug messages
20006 @cindex Linux lightweight processes
20007 Turns on or off debugging messages from the Linux LWP debug support.
20008 @item show debug lin-lwp
20009 Show the current state of Linux LWP debugging messages.
20010 @item set debug lin-lwp-async
20011 @cindex @sc{gnu}/Linux LWP async debug messages
20012 @cindex Linux lightweight processes
20013 Turns on or off debugging messages from the Linux LWP async debug support.
20014 @item show debug lin-lwp-async
20015 Show the current state of Linux LWP async debugging messages.
20016 @item set debug observer
20017 @cindex observer debugging info
20018 Turns on or off display of @value{GDBN} observer debugging. This
20019 includes info such as the notification of observable events.
20020 @item show debug observer
20021 Displays the current state of observer debugging.
20022 @item set debug overload
20023 @cindex C@t{++} overload debugging info
20024 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20025 info. This includes info such as ranking of functions, etc. The default
20027 @item show debug overload
20028 Displays the current state of displaying @value{GDBN} C@t{++} overload
20030 @cindex expression parser, debugging info
20031 @cindex debug expression parser
20032 @item set debug parser
20033 Turns on or off the display of expression parser debugging output.
20034 Internally, this sets the @code{yydebug} variable in the expression
20035 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20036 details. The default is off.
20037 @item show debug parser
20038 Show the current state of expression parser debugging.
20039 @cindex packets, reporting on stdout
20040 @cindex serial connections, debugging
20041 @cindex debug remote protocol
20042 @cindex remote protocol debugging
20043 @cindex display remote packets
20044 @item set debug remote
20045 Turns on or off display of reports on all packets sent back and forth across
20046 the serial line to the remote machine. The info is printed on the
20047 @value{GDBN} standard output stream. The default is off.
20048 @item show debug remote
20049 Displays the state of display of remote packets.
20050 @item set debug serial
20051 Turns on or off display of @value{GDBN} serial debugging info. The
20053 @item show debug serial
20054 Displays the current state of displaying @value{GDBN} serial debugging
20056 @item set debug solib-frv
20057 @cindex FR-V shared-library debugging
20058 Turns on or off debugging messages for FR-V shared-library code.
20059 @item show debug solib-frv
20060 Display the current state of FR-V shared-library code debugging
20062 @item set debug target
20063 @cindex target debugging info
20064 Turns on or off display of @value{GDBN} target debugging info. This info
20065 includes what is going on at the target level of GDB, as it happens. The
20066 default is 0. Set it to 1 to track events, and to 2 to also track the
20067 value of large memory transfers. Changes to this flag do not take effect
20068 until the next time you connect to a target or use the @code{run} command.
20069 @item show debug target
20070 Displays the current state of displaying @value{GDBN} target debugging
20072 @item set debug timestamp
20073 @cindex timestampping debugging info
20074 Turns on or off display of timestamps with @value{GDBN} debugging info.
20075 When enabled, seconds and microseconds are displayed before each debugging
20077 @item show debug timestamp
20078 Displays the current state of displaying timestamps with @value{GDBN}
20080 @item set debugvarobj
20081 @cindex variable object debugging info
20082 Turns on or off display of @value{GDBN} variable object debugging
20083 info. The default is off.
20084 @item show debugvarobj
20085 Displays the current state of displaying @value{GDBN} variable object
20087 @item set debug xml
20088 @cindex XML parser debugging
20089 Turns on or off debugging messages for built-in XML parsers.
20090 @item show debug xml
20091 Displays the current state of XML debugging messages.
20094 @node Other Misc Settings
20095 @section Other Miscellaneous Settings
20096 @cindex miscellaneous settings
20099 @kindex set interactive-mode
20100 @item set interactive-mode
20101 If @code{on}, forces @value{GDBN} to assume that GDB was started
20102 in a terminal. In practice, this means that @value{GDBN} should wait
20103 for the user to answer queries generated by commands entered at
20104 the command prompt. If @code{off}, forces @value{GDBN} to operate
20105 in the opposite mode, and it uses the default answers to all queries.
20106 If @code{auto} (the default), @value{GDBN} tries to determine whether
20107 its standard input is a terminal, and works in interactive-mode if it
20108 is, non-interactively otherwise.
20110 In the vast majority of cases, the debugger should be able to guess
20111 correctly which mode should be used. But this setting can be useful
20112 in certain specific cases, such as running a MinGW @value{GDBN}
20113 inside a cygwin window.
20115 @kindex show interactive-mode
20116 @item show interactive-mode
20117 Displays whether the debugger is operating in interactive mode or not.
20120 @node Extending GDB
20121 @chapter Extending @value{GDBN}
20122 @cindex extending GDB
20124 @value{GDBN} provides two mechanisms for extension. The first is based
20125 on composition of @value{GDBN} commands, and the second is based on the
20126 Python scripting language.
20128 To facilitate the use of these extensions, @value{GDBN} is capable
20129 of evaluating the contents of a file. When doing so, @value{GDBN}
20130 can recognize which scripting language is being used by looking at
20131 the filename extension. Files with an unrecognized filename extension
20132 are always treated as a @value{GDBN} Command Files.
20133 @xref{Command Files,, Command files}.
20135 You can control how @value{GDBN} evaluates these files with the following
20139 @kindex set script-extension
20140 @kindex show script-extension
20141 @item set script-extension off
20142 All scripts are always evaluated as @value{GDBN} Command Files.
20144 @item set script-extension soft
20145 The debugger determines the scripting language based on filename
20146 extension. If this scripting language is supported, @value{GDBN}
20147 evaluates the script using that language. Otherwise, it evaluates
20148 the file as a @value{GDBN} Command File.
20150 @item set script-extension strict
20151 The debugger determines the scripting language based on filename
20152 extension, and evaluates the script using that language. If the
20153 language is not supported, then the evaluation fails.
20155 @item show script-extension
20156 Display the current value of the @code{script-extension} option.
20161 * Sequences:: Canned Sequences of Commands
20162 * Python:: Scripting @value{GDBN} using Python
20166 @section Canned Sequences of Commands
20168 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20169 Command Lists}), @value{GDBN} provides two ways to store sequences of
20170 commands for execution as a unit: user-defined commands and command
20174 * Define:: How to define your own commands
20175 * Hooks:: Hooks for user-defined commands
20176 * Command Files:: How to write scripts of commands to be stored in a file
20177 * Output:: Commands for controlled output
20181 @subsection User-defined Commands
20183 @cindex user-defined command
20184 @cindex arguments, to user-defined commands
20185 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20186 which you assign a new name as a command. This is done with the
20187 @code{define} command. User commands may accept up to 10 arguments
20188 separated by whitespace. Arguments are accessed within the user command
20189 via @code{$arg0@dots{}$arg9}. A trivial example:
20193 print $arg0 + $arg1 + $arg2
20198 To execute the command use:
20205 This defines the command @code{adder}, which prints the sum of
20206 its three arguments. Note the arguments are text substitutions, so they may
20207 reference variables, use complex expressions, or even perform inferior
20210 @cindex argument count in user-defined commands
20211 @cindex how many arguments (user-defined commands)
20212 In addition, @code{$argc} may be used to find out how many arguments have
20213 been passed. This expands to a number in the range 0@dots{}10.
20218 print $arg0 + $arg1
20221 print $arg0 + $arg1 + $arg2
20229 @item define @var{commandname}
20230 Define a command named @var{commandname}. If there is already a command
20231 by that name, you are asked to confirm that you want to redefine it.
20232 @var{commandname} may be a bare command name consisting of letters,
20233 numbers, dashes, and underscores. It may also start with any predefined
20234 prefix command. For example, @samp{define target my-target} creates
20235 a user-defined @samp{target my-target} command.
20237 The definition of the command is made up of other @value{GDBN} command lines,
20238 which are given following the @code{define} command. The end of these
20239 commands is marked by a line containing @code{end}.
20242 @kindex end@r{ (user-defined commands)}
20243 @item document @var{commandname}
20244 Document the user-defined command @var{commandname}, so that it can be
20245 accessed by @code{help}. The command @var{commandname} must already be
20246 defined. This command reads lines of documentation just as @code{define}
20247 reads the lines of the command definition, ending with @code{end}.
20248 After the @code{document} command is finished, @code{help} on command
20249 @var{commandname} displays the documentation you have written.
20251 You may use the @code{document} command again to change the
20252 documentation of a command. Redefining the command with @code{define}
20253 does not change the documentation.
20255 @kindex dont-repeat
20256 @cindex don't repeat command
20258 Used inside a user-defined command, this tells @value{GDBN} that this
20259 command should not be repeated when the user hits @key{RET}
20260 (@pxref{Command Syntax, repeat last command}).
20262 @kindex help user-defined
20263 @item help user-defined
20264 List all user-defined commands, with the first line of the documentation
20269 @itemx show user @var{commandname}
20270 Display the @value{GDBN} commands used to define @var{commandname} (but
20271 not its documentation). If no @var{commandname} is given, display the
20272 definitions for all user-defined commands.
20274 @cindex infinite recursion in user-defined commands
20275 @kindex show max-user-call-depth
20276 @kindex set max-user-call-depth
20277 @item show max-user-call-depth
20278 @itemx set max-user-call-depth
20279 The value of @code{max-user-call-depth} controls how many recursion
20280 levels are allowed in user-defined commands before @value{GDBN} suspects an
20281 infinite recursion and aborts the command.
20284 In addition to the above commands, user-defined commands frequently
20285 use control flow commands, described in @ref{Command Files}.
20287 When user-defined commands are executed, the
20288 commands of the definition are not printed. An error in any command
20289 stops execution of the user-defined command.
20291 If used interactively, commands that would ask for confirmation proceed
20292 without asking when used inside a user-defined command. Many @value{GDBN}
20293 commands that normally print messages to say what they are doing omit the
20294 messages when used in a user-defined command.
20297 @subsection User-defined Command Hooks
20298 @cindex command hooks
20299 @cindex hooks, for commands
20300 @cindex hooks, pre-command
20303 You may define @dfn{hooks}, which are a special kind of user-defined
20304 command. Whenever you run the command @samp{foo}, if the user-defined
20305 command @samp{hook-foo} exists, it is executed (with no arguments)
20306 before that command.
20308 @cindex hooks, post-command
20310 A hook may also be defined which is run after the command you executed.
20311 Whenever you run the command @samp{foo}, if the user-defined command
20312 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20313 that command. Post-execution hooks may exist simultaneously with
20314 pre-execution hooks, for the same command.
20316 It is valid for a hook to call the command which it hooks. If this
20317 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20319 @c It would be nice if hookpost could be passed a parameter indicating
20320 @c if the command it hooks executed properly or not. FIXME!
20322 @kindex stop@r{, a pseudo-command}
20323 In addition, a pseudo-command, @samp{stop} exists. Defining
20324 (@samp{hook-stop}) makes the associated commands execute every time
20325 execution stops in your program: before breakpoint commands are run,
20326 displays are printed, or the stack frame is printed.
20328 For example, to ignore @code{SIGALRM} signals while
20329 single-stepping, but treat them normally during normal execution,
20334 handle SIGALRM nopass
20338 handle SIGALRM pass
20341 define hook-continue
20342 handle SIGALRM pass
20346 As a further example, to hook at the beginning and end of the @code{echo}
20347 command, and to add extra text to the beginning and end of the message,
20355 define hookpost-echo
20359 (@value{GDBP}) echo Hello World
20360 <<<---Hello World--->>>
20365 You can define a hook for any single-word command in @value{GDBN}, but
20366 not for command aliases; you should define a hook for the basic command
20367 name, e.g.@: @code{backtrace} rather than @code{bt}.
20368 @c FIXME! So how does Joe User discover whether a command is an alias
20370 You can hook a multi-word command by adding @code{hook-} or
20371 @code{hookpost-} to the last word of the command, e.g.@:
20372 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20374 If an error occurs during the execution of your hook, execution of
20375 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20376 (before the command that you actually typed had a chance to run).
20378 If you try to define a hook which does not match any known command, you
20379 get a warning from the @code{define} command.
20381 @node Command Files
20382 @subsection Command Files
20384 @cindex command files
20385 @cindex scripting commands
20386 A command file for @value{GDBN} is a text file made of lines that are
20387 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20388 also be included. An empty line in a command file does nothing; it
20389 does not mean to repeat the last command, as it would from the
20392 You can request the execution of a command file with the @code{source}
20393 command. Note that the @code{source} command is also used to evaluate
20394 scripts that are not Command Files. The exact behavior can be configured
20395 using the @code{script-extension} setting.
20396 @xref{Extending GDB,, Extending GDB}.
20400 @cindex execute commands from a file
20401 @item source [-s] [-v] @var{filename}
20402 Execute the command file @var{filename}.
20405 The lines in a command file are generally executed sequentially,
20406 unless the order of execution is changed by one of the
20407 @emph{flow-control commands} described below. The commands are not
20408 printed as they are executed. An error in any command terminates
20409 execution of the command file and control is returned to the console.
20411 @value{GDBN} first searches for @var{filename} in the current directory.
20412 If the file is not found there, and @var{filename} does not specify a
20413 directory, then @value{GDBN} also looks for the file on the source search path
20414 (specified with the @samp{directory} command);
20415 except that @file{$cdir} is not searched because the compilation directory
20416 is not relevant to scripts.
20418 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20419 on the search path even if @var{filename} specifies a directory.
20420 The search is done by appending @var{filename} to each element of the
20421 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20422 and the search path contains @file{/home/user} then @value{GDBN} will
20423 look for the script @file{/home/user/mylib/myscript}.
20424 The search is also done if @var{filename} is an absolute path.
20425 For example, if @var{filename} is @file{/tmp/myscript} and
20426 the search path contains @file{/home/user} then @value{GDBN} will
20427 look for the script @file{/home/user/tmp/myscript}.
20428 For DOS-like systems, if @var{filename} contains a drive specification,
20429 it is stripped before concatenation. For example, if @var{filename} is
20430 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20431 will look for the script @file{c:/tmp/myscript}.
20433 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20434 each command as it is executed. The option must be given before
20435 @var{filename}, and is interpreted as part of the filename anywhere else.
20437 Commands that would ask for confirmation if used interactively proceed
20438 without asking when used in a command file. Many @value{GDBN} commands that
20439 normally print messages to say what they are doing omit the messages
20440 when called from command files.
20442 @value{GDBN} also accepts command input from standard input. In this
20443 mode, normal output goes to standard output and error output goes to
20444 standard error. Errors in a command file supplied on standard input do
20445 not terminate execution of the command file---execution continues with
20449 gdb < cmds > log 2>&1
20452 (The syntax above will vary depending on the shell used.) This example
20453 will execute commands from the file @file{cmds}. All output and errors
20454 would be directed to @file{log}.
20456 Since commands stored on command files tend to be more general than
20457 commands typed interactively, they frequently need to deal with
20458 complicated situations, such as different or unexpected values of
20459 variables and symbols, changes in how the program being debugged is
20460 built, etc. @value{GDBN} provides a set of flow-control commands to
20461 deal with these complexities. Using these commands, you can write
20462 complex scripts that loop over data structures, execute commands
20463 conditionally, etc.
20470 This command allows to include in your script conditionally executed
20471 commands. The @code{if} command takes a single argument, which is an
20472 expression to evaluate. It is followed by a series of commands that
20473 are executed only if the expression is true (its value is nonzero).
20474 There can then optionally be an @code{else} line, followed by a series
20475 of commands that are only executed if the expression was false. The
20476 end of the list is marked by a line containing @code{end}.
20480 This command allows to write loops. Its syntax is similar to
20481 @code{if}: the command takes a single argument, which is an expression
20482 to evaluate, and must be followed by the commands to execute, one per
20483 line, terminated by an @code{end}. These commands are called the
20484 @dfn{body} of the loop. The commands in the body of @code{while} are
20485 executed repeatedly as long as the expression evaluates to true.
20489 This command exits the @code{while} loop in whose body it is included.
20490 Execution of the script continues after that @code{while}s @code{end}
20493 @kindex loop_continue
20494 @item loop_continue
20495 This command skips the execution of the rest of the body of commands
20496 in the @code{while} loop in whose body it is included. Execution
20497 branches to the beginning of the @code{while} loop, where it evaluates
20498 the controlling expression.
20500 @kindex end@r{ (if/else/while commands)}
20502 Terminate the block of commands that are the body of @code{if},
20503 @code{else}, or @code{while} flow-control commands.
20508 @subsection Commands for Controlled Output
20510 During the execution of a command file or a user-defined command, normal
20511 @value{GDBN} output is suppressed; the only output that appears is what is
20512 explicitly printed by the commands in the definition. This section
20513 describes three commands useful for generating exactly the output you
20518 @item echo @var{text}
20519 @c I do not consider backslash-space a standard C escape sequence
20520 @c because it is not in ANSI.
20521 Print @var{text}. Nonprinting characters can be included in
20522 @var{text} using C escape sequences, such as @samp{\n} to print a
20523 newline. @strong{No newline is printed unless you specify one.}
20524 In addition to the standard C escape sequences, a backslash followed
20525 by a space stands for a space. This is useful for displaying a
20526 string with spaces at the beginning or the end, since leading and
20527 trailing spaces are otherwise trimmed from all arguments.
20528 To print @samp{@w{ }and foo =@w{ }}, use the command
20529 @samp{echo \@w{ }and foo = \@w{ }}.
20531 A backslash at the end of @var{text} can be used, as in C, to continue
20532 the command onto subsequent lines. For example,
20535 echo This is some text\n\
20536 which is continued\n\
20537 onto several lines.\n
20540 produces the same output as
20543 echo This is some text\n
20544 echo which is continued\n
20545 echo onto several lines.\n
20549 @item output @var{expression}
20550 Print the value of @var{expression} and nothing but that value: no
20551 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20552 value history either. @xref{Expressions, ,Expressions}, for more information
20555 @item output/@var{fmt} @var{expression}
20556 Print the value of @var{expression} in format @var{fmt}. You can use
20557 the same formats as for @code{print}. @xref{Output Formats,,Output
20558 Formats}, for more information.
20561 @item printf @var{template}, @var{expressions}@dots{}
20562 Print the values of one or more @var{expressions} under the control of
20563 the string @var{template}. To print several values, make
20564 @var{expressions} be a comma-separated list of individual expressions,
20565 which may be either numbers or pointers. Their values are printed as
20566 specified by @var{template}, exactly as a C program would do by
20567 executing the code below:
20570 printf (@var{template}, @var{expressions}@dots{});
20573 As in @code{C} @code{printf}, ordinary characters in @var{template}
20574 are printed verbatim, while @dfn{conversion specification} introduced
20575 by the @samp{%} character cause subsequent @var{expressions} to be
20576 evaluated, their values converted and formatted according to type and
20577 style information encoded in the conversion specifications, and then
20580 For example, you can print two values in hex like this:
20583 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20586 @code{printf} supports all the standard @code{C} conversion
20587 specifications, including the flags and modifiers between the @samp{%}
20588 character and the conversion letter, with the following exceptions:
20592 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20595 The modifier @samp{*} is not supported for specifying precision or
20599 The @samp{'} flag (for separation of digits into groups according to
20600 @code{LC_NUMERIC'}) is not supported.
20603 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20607 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20610 The conversion letters @samp{a} and @samp{A} are not supported.
20614 Note that the @samp{ll} type modifier is supported only if the
20615 underlying @code{C} implementation used to build @value{GDBN} supports
20616 the @code{long long int} type, and the @samp{L} type modifier is
20617 supported only if @code{long double} type is available.
20619 As in @code{C}, @code{printf} supports simple backslash-escape
20620 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20621 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20622 single character. Octal and hexadecimal escape sequences are not
20625 Additionally, @code{printf} supports conversion specifications for DFP
20626 (@dfn{Decimal Floating Point}) types using the following length modifiers
20627 together with a floating point specifier.
20632 @samp{H} for printing @code{Decimal32} types.
20635 @samp{D} for printing @code{Decimal64} types.
20638 @samp{DD} for printing @code{Decimal128} types.
20641 If the underlying @code{C} implementation used to build @value{GDBN} has
20642 support for the three length modifiers for DFP types, other modifiers
20643 such as width and precision will also be available for @value{GDBN} to use.
20645 In case there is no such @code{C} support, no additional modifiers will be
20646 available and the value will be printed in the standard way.
20648 Here's an example of printing DFP types using the above conversion letters:
20650 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20654 @item eval @var{template}, @var{expressions}@dots{}
20655 Convert the values of one or more @var{expressions} under the control of
20656 the string @var{template} to a command line, and call it.
20661 @section Scripting @value{GDBN} using Python
20662 @cindex python scripting
20663 @cindex scripting with python
20665 You can script @value{GDBN} using the @uref{http://www.python.org/,
20666 Python programming language}. This feature is available only if
20667 @value{GDBN} was configured using @option{--with-python}.
20669 @cindex python directory
20670 Python scripts used by @value{GDBN} should be installed in
20671 @file{@var{data-directory}/python}, where @var{data-directory} is
20672 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20673 This directory, known as the @dfn{python directory},
20674 is automatically added to the Python Search Path in order to allow
20675 the Python interpreter to locate all scripts installed at this location.
20678 * Python Commands:: Accessing Python from @value{GDBN}.
20679 * Python API:: Accessing @value{GDBN} from Python.
20680 * Auto-loading:: Automatically loading Python code.
20681 * Python modules:: Python modules provided by @value{GDBN}.
20684 @node Python Commands
20685 @subsection Python Commands
20686 @cindex python commands
20687 @cindex commands to access python
20689 @value{GDBN} provides one command for accessing the Python interpreter,
20690 and one related setting:
20694 @item python @r{[}@var{code}@r{]}
20695 The @code{python} command can be used to evaluate Python code.
20697 If given an argument, the @code{python} command will evaluate the
20698 argument as a Python command. For example:
20701 (@value{GDBP}) python print 23
20705 If you do not provide an argument to @code{python}, it will act as a
20706 multi-line command, like @code{define}. In this case, the Python
20707 script is made up of subsequent command lines, given after the
20708 @code{python} command. This command list is terminated using a line
20709 containing @code{end}. For example:
20712 (@value{GDBP}) python
20714 End with a line saying just "end".
20720 @kindex maint set python print-stack
20721 @item maint set python print-stack
20722 By default, @value{GDBN} will print a stack trace when an error occurs
20723 in a Python script. This can be controlled using @code{maint set
20724 python print-stack}: if @code{on}, the default, then Python stack
20725 printing is enabled; if @code{off}, then Python stack printing is
20729 It is also possible to execute a Python script from the @value{GDBN}
20733 @item source @file{script-name}
20734 The script name must end with @samp{.py} and @value{GDBN} must be configured
20735 to recognize the script language based on filename extension using
20736 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20738 @item python execfile ("script-name")
20739 This method is based on the @code{execfile} Python built-in function,
20740 and thus is always available.
20744 @subsection Python API
20746 @cindex programming in python
20748 @cindex python stdout
20749 @cindex python pagination
20750 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20751 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20752 A Python program which outputs to one of these streams may have its
20753 output interrupted by the user (@pxref{Screen Size}). In this
20754 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20757 * Basic Python:: Basic Python Functions.
20758 * Exception Handling:: How Python exceptions are translated.
20759 * Values From Inferior:: Python representation of values.
20760 * Types In Python:: Python representation of types.
20761 * Pretty Printing API:: Pretty-printing values.
20762 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20763 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20764 * Inferiors In Python:: Python representation of inferiors (processes)
20765 * Events In Python:: Listening for events from @value{GDBN}.
20766 * Threads In Python:: Accessing inferior threads from Python.
20767 * Commands In Python:: Implementing new commands in Python.
20768 * Parameters In Python:: Adding new @value{GDBN} parameters.
20769 * Functions In Python:: Writing new convenience functions.
20770 * Progspaces In Python:: Program spaces.
20771 * Objfiles In Python:: Object files.
20772 * Frames In Python:: Accessing inferior stack frames from Python.
20773 * Blocks In Python:: Accessing frame blocks from Python.
20774 * Symbols In Python:: Python representation of symbols.
20775 * Symbol Tables In Python:: Python representation of symbol tables.
20776 * Lazy Strings In Python:: Python representation of lazy strings.
20777 * Breakpoints In Python:: Manipulating breakpoints using Python.
20781 @subsubsection Basic Python
20783 @cindex python functions
20784 @cindex python module
20786 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20787 methods and classes added by @value{GDBN} are placed in this module.
20788 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20789 use in all scripts evaluated by the @code{python} command.
20791 @findex gdb.PYTHONDIR
20793 A string containing the python directory (@pxref{Python}).
20796 @findex gdb.execute
20797 @defun execute command [from_tty] [to_string]
20798 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20799 If a GDB exception happens while @var{command} runs, it is
20800 translated as described in @ref{Exception Handling,,Exception Handling}.
20802 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20803 command as having originated from the user invoking it interactively.
20804 It must be a boolean value. If omitted, it defaults to @code{False}.
20806 By default, any output produced by @var{command} is sent to
20807 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20808 @code{True}, then output will be collected by @code{gdb.execute} and
20809 returned as a string. The default is @code{False}, in which case the
20810 return value is @code{None}. If @var{to_string} is @code{True}, the
20811 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20812 and height, and its pagination will be disabled; @pxref{Screen Size}.
20815 @findex gdb.breakpoints
20817 Return a sequence holding all of @value{GDBN}'s breakpoints.
20818 @xref{Breakpoints In Python}, for more information.
20821 @findex gdb.parameter
20822 @defun parameter parameter
20823 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20824 string naming the parameter to look up; @var{parameter} may contain
20825 spaces if the parameter has a multi-part name. For example,
20826 @samp{print object} is a valid parameter name.
20828 If the named parameter does not exist, this function throws a
20829 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20830 parameter's value is converted to a Python value of the appropriate
20831 type, and returned.
20834 @findex gdb.history
20835 @defun history number
20836 Return a value from @value{GDBN}'s value history (@pxref{Value
20837 History}). @var{number} indicates which history element to return.
20838 If @var{number} is negative, then @value{GDBN} will take its absolute value
20839 and count backward from the last element (i.e., the most recent element) to
20840 find the value to return. If @var{number} is zero, then @value{GDBN} will
20841 return the most recent element. If the element specified by @var{number}
20842 doesn't exist in the value history, a @code{gdb.error} exception will be
20845 If no exception is raised, the return value is always an instance of
20846 @code{gdb.Value} (@pxref{Values From Inferior}).
20849 @findex gdb.parse_and_eval
20850 @defun parse_and_eval expression
20851 Parse @var{expression} as an expression in the current language,
20852 evaluate it, and return the result as a @code{gdb.Value}.
20853 @var{expression} must be a string.
20855 This function can be useful when implementing a new command
20856 (@pxref{Commands In Python}), as it provides a way to parse the
20857 command's argument as an expression. It is also useful simply to
20858 compute values, for example, it is the only way to get the value of a
20859 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20862 @findex gdb.post_event
20863 @defun post_event event
20864 Put @var{event}, a callable object taking no arguments, into
20865 @value{GDBN}'s internal event queue. This callable will be invoked at
20866 some later point, during @value{GDBN}'s event processing. Events
20867 posted using @code{post_event} will be run in the order in which they
20868 were posted; however, there is no way to know when they will be
20869 processed relative to other events inside @value{GDBN}.
20871 @value{GDBN} is not thread-safe. If your Python program uses multiple
20872 threads, you must be careful to only call @value{GDBN}-specific
20873 functions in the main @value{GDBN} thread. @code{post_event} ensures
20877 (@value{GDBP}) python
20881 > def __init__(self, message):
20882 > self.message = message;
20883 > def __call__(self):
20884 > gdb.write(self.message)
20886 >class MyThread1 (threading.Thread):
20888 > gdb.post_event(Writer("Hello "))
20890 >class MyThread2 (threading.Thread):
20892 > gdb.post_event(Writer("World\n"))
20894 >MyThread1().start()
20895 >MyThread2().start()
20897 (@value{GDBP}) Hello World
20902 @defun write string @r{[}stream{]}
20903 Print a string to @value{GDBN}'s paginated output stream. The
20904 optional @var{stream} determines the stream to print to. The default
20905 stream is @value{GDBN}'s standard output stream. Possible stream
20912 @value{GDBN}'s standard output stream.
20917 @value{GDBN}'s standard error stream.
20922 @value{GDBN}'s log stream (@pxref{Logging Output}).
20925 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20926 call this function and will automatically direct the output to the
20932 Flush the buffer of a @value{GDBN} paginated stream so that the
20933 contents are displayed immediately. @value{GDBN} will flush the
20934 contents of a stream automatically when it encounters a newline in the
20935 buffer. The optional @var{stream} determines the stream to flush. The
20936 default stream is @value{GDBN}'s standard output stream. Possible
20943 @value{GDBN}'s standard output stream.
20948 @value{GDBN}'s standard error stream.
20953 @value{GDBN}'s log stream (@pxref{Logging Output}).
20957 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
20958 call this function for the relevant stream.
20961 @findex gdb.target_charset
20962 @defun target_charset
20963 Return the name of the current target character set (@pxref{Character
20964 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20965 that @samp{auto} is never returned.
20968 @findex gdb.target_wide_charset
20969 @defun target_wide_charset
20970 Return the name of the current target wide character set
20971 (@pxref{Character Sets}). This differs from
20972 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20976 @findex gdb.solib_name
20977 @defun solib_name address
20978 Return the name of the shared library holding the given @var{address}
20979 as a string, or @code{None}.
20982 @findex gdb.decode_line
20983 @defun decode_line @r{[}expression@r{]}
20984 Return locations of the line specified by @var{expression}, or of the
20985 current line if no argument was given. This function returns a Python
20986 tuple containing two elements. The first element contains a string
20987 holding any unparsed section of @var{expression} (or @code{None} if
20988 the expression has been fully parsed). The second element contains
20989 either @code{None} or another tuple that contains all the locations
20990 that match the expression represented as @code{gdb.Symtab_and_line}
20991 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20992 provided, it is decoded the way that @value{GDBN}'s inbuilt
20993 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20996 @node Exception Handling
20997 @subsubsection Exception Handling
20998 @cindex python exceptions
20999 @cindex exceptions, python
21001 When executing the @code{python} command, Python exceptions
21002 uncaught within the Python code are translated to calls to
21003 @value{GDBN} error-reporting mechanism. If the command that called
21004 @code{python} does not handle the error, @value{GDBN} will
21005 terminate it and print an error message containing the Python
21006 exception name, the associated value, and the Python call stack
21007 backtrace at the point where the exception was raised. Example:
21010 (@value{GDBP}) python print foo
21011 Traceback (most recent call last):
21012 File "<string>", line 1, in <module>
21013 NameError: name 'foo' is not defined
21016 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21017 Python code are converted to Python exceptions. The type of the
21018 Python exception depends on the error.
21022 This is the base class for most exceptions generated by @value{GDBN}.
21023 It is derived from @code{RuntimeError}, for compatibility with earlier
21024 versions of @value{GDBN}.
21026 If an error occurring in @value{GDBN} does not fit into some more
21027 specific category, then the generated exception will have this type.
21029 @item gdb.MemoryError
21030 This is a subclass of @code{gdb.error} which is thrown when an
21031 operation tried to access invalid memory in the inferior.
21033 @item KeyboardInterrupt
21034 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21035 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21038 In all cases, your exception handler will see the @value{GDBN} error
21039 message as its value and the Python call stack backtrace at the Python
21040 statement closest to where the @value{GDBN} error occured as the
21043 @findex gdb.GdbError
21044 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21045 it is useful to be able to throw an exception that doesn't cause a
21046 traceback to be printed. For example, the user may have invoked the
21047 command incorrectly. Use the @code{gdb.GdbError} exception
21048 to handle this case. Example:
21052 >class HelloWorld (gdb.Command):
21053 > """Greet the whole world."""
21054 > def __init__ (self):
21055 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21056 > def invoke (self, args, from_tty):
21057 > argv = gdb.string_to_argv (args)
21058 > if len (argv) != 0:
21059 > raise gdb.GdbError ("hello-world takes no arguments")
21060 > print "Hello, World!"
21063 (gdb) hello-world 42
21064 hello-world takes no arguments
21067 @node Values From Inferior
21068 @subsubsection Values From Inferior
21069 @cindex values from inferior, with Python
21070 @cindex python, working with values from inferior
21072 @cindex @code{gdb.Value}
21073 @value{GDBN} provides values it obtains from the inferior program in
21074 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21075 for its internal bookkeeping of the inferior's values, and for
21076 fetching values when necessary.
21078 Inferior values that are simple scalars can be used directly in
21079 Python expressions that are valid for the value's data type. Here's
21080 an example for an integer or floating-point value @code{some_val}:
21087 As result of this, @code{bar} will also be a @code{gdb.Value} object
21088 whose values are of the same type as those of @code{some_val}.
21090 Inferior values that are structures or instances of some class can
21091 be accessed using the Python @dfn{dictionary syntax}. For example, if
21092 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21093 can access its @code{foo} element with:
21096 bar = some_val['foo']
21099 Again, @code{bar} will also be a @code{gdb.Value} object.
21101 A @code{gdb.Value} that represents a function can be executed via
21102 inferior function call. Any arguments provided to the call must match
21103 the function's prototype, and must be provided in the order specified
21106 For example, @code{some_val} is a @code{gdb.Value} instance
21107 representing a function that takes two integers as arguments. To
21108 execute this function, call it like so:
21111 result = some_val (10,20)
21114 Any values returned from a function call will be stored as a
21117 The following attributes are provided:
21120 @defivar Value address
21121 If this object is addressable, this read-only attribute holds a
21122 @code{gdb.Value} object representing the address. Otherwise,
21123 this attribute holds @code{None}.
21126 @cindex optimized out value in Python
21127 @defivar Value is_optimized_out
21128 This read-only boolean attribute is true if the compiler optimized out
21129 this value, thus it is not available for fetching from the inferior.
21132 @defivar Value type
21133 The type of this @code{gdb.Value}. The value of this attribute is a
21134 @code{gdb.Type} object (@pxref{Types In Python}).
21137 @defivar Value dynamic_type
21138 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21139 type information (@acronym{RTTI}) to determine the dynamic type of the
21140 value. If this value is of class type, it will return the class in
21141 which the value is embedded, if any. If this value is of pointer or
21142 reference to a class type, it will compute the dynamic type of the
21143 referenced object, and return a pointer or reference to that type,
21144 respectively. In all other cases, it will return the value's static
21147 Note that this feature will only work when debugging a C@t{++} program
21148 that includes @acronym{RTTI} for the object in question. Otherwise,
21149 it will just return the static type of the value as in @kbd{ptype foo}
21150 (@pxref{Symbols, ptype}).
21154 The following methods are provided:
21157 @defmethod Value __init__ @var{val}
21158 Many Python values can be converted directly to a @code{gdb.Value} via
21159 this object initializer. Specifically:
21162 @item Python boolean
21163 A Python boolean is converted to the boolean type from the current
21166 @item Python integer
21167 A Python integer is converted to the C @code{long} type for the
21168 current architecture.
21171 A Python long is converted to the C @code{long long} type for the
21172 current architecture.
21175 A Python float is converted to the C @code{double} type for the
21176 current architecture.
21178 @item Python string
21179 A Python string is converted to a target string, using the current
21182 @item @code{gdb.Value}
21183 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21185 @item @code{gdb.LazyString}
21186 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21187 Python}), then the lazy string's @code{value} method is called, and
21188 its result is used.
21192 @defmethod Value cast type
21193 Return a new instance of @code{gdb.Value} that is the result of
21194 casting this instance to the type described by @var{type}, which must
21195 be a @code{gdb.Type} object. If the cast cannot be performed for some
21196 reason, this method throws an exception.
21199 @defmethod Value dereference
21200 For pointer data types, this method returns a new @code{gdb.Value} object
21201 whose contents is the object pointed to by the pointer. For example, if
21202 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21209 then you can use the corresponding @code{gdb.Value} to access what
21210 @code{foo} points to like this:
21213 bar = foo.dereference ()
21216 The result @code{bar} will be a @code{gdb.Value} object holding the
21217 value pointed to by @code{foo}.
21220 @defmethod Value dynamic_cast type
21221 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21222 operator were used. Consult a C@t{++} reference for details.
21225 @defmethod Value reinterpret_cast type
21226 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21227 operator were used. Consult a C@t{++} reference for details.
21230 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21231 If this @code{gdb.Value} represents a string, then this method
21232 converts the contents to a Python string. Otherwise, this method will
21233 throw an exception.
21235 Strings are recognized in a language-specific way; whether a given
21236 @code{gdb.Value} represents a string is determined by the current
21239 For C-like languages, a value is a string if it is a pointer to or an
21240 array of characters or ints. The string is assumed to be terminated
21241 by a zero of the appropriate width. However if the optional length
21242 argument is given, the string will be converted to that given length,
21243 ignoring any embedded zeros that the string may contain.
21245 If the optional @var{encoding} argument is given, it must be a string
21246 naming the encoding of the string in the @code{gdb.Value}, such as
21247 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21248 the same encodings as the corresponding argument to Python's
21249 @code{string.decode} method, and the Python codec machinery will be used
21250 to convert the string. If @var{encoding} is not given, or if
21251 @var{encoding} is the empty string, then either the @code{target-charset}
21252 (@pxref{Character Sets}) will be used, or a language-specific encoding
21253 will be used, if the current language is able to supply one.
21255 The optional @var{errors} argument is the same as the corresponding
21256 argument to Python's @code{string.decode} method.
21258 If the optional @var{length} argument is given, the string will be
21259 fetched and converted to the given length.
21262 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21263 If this @code{gdb.Value} represents a string, then this method
21264 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21265 In Python}). Otherwise, this method will throw an exception.
21267 If the optional @var{encoding} argument is given, it must be a string
21268 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21269 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21270 @var{encoding} argument is an encoding that @value{GDBN} does
21271 recognize, @value{GDBN} will raise an error.
21273 When a lazy string is printed, the @value{GDBN} encoding machinery is
21274 used to convert the string during printing. If the optional
21275 @var{encoding} argument is not provided, or is an empty string,
21276 @value{GDBN} will automatically select the encoding most suitable for
21277 the string type. For further information on encoding in @value{GDBN}
21278 please see @ref{Character Sets}.
21280 If the optional @var{length} argument is given, the string will be
21281 fetched and encoded to the length of characters specified. If
21282 the @var{length} argument is not provided, the string will be fetched
21283 and encoded until a null of appropriate width is found.
21287 @node Types In Python
21288 @subsubsection Types In Python
21289 @cindex types in Python
21290 @cindex Python, working with types
21293 @value{GDBN} represents types from the inferior using the class
21296 The following type-related functions are available in the @code{gdb}
21299 @findex gdb.lookup_type
21300 @defun lookup_type name [block]
21301 This function looks up a type by name. @var{name} is the name of the
21302 type to look up. It must be a string.
21304 If @var{block} is given, then @var{name} is looked up in that scope.
21305 Otherwise, it is searched for globally.
21307 Ordinarily, this function will return an instance of @code{gdb.Type}.
21308 If the named type cannot be found, it will throw an exception.
21311 An instance of @code{Type} has the following attributes:
21315 The type code for this type. The type code will be one of the
21316 @code{TYPE_CODE_} constants defined below.
21319 @defivar Type sizeof
21320 The size of this type, in target @code{char} units. Usually, a
21321 target's @code{char} type will be an 8-bit byte. However, on some
21322 unusual platforms, this type may have a different size.
21326 The tag name for this type. The tag name is the name after
21327 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21328 languages have this concept. If this type has no tag name, then
21329 @code{None} is returned.
21333 The following methods are provided:
21336 @defmethod Type fields
21337 For structure and union types, this method returns the fields. Range
21338 types have two fields, the minimum and maximum values. Enum types
21339 have one field per enum constant. Function and method types have one
21340 field per parameter. The base types of C@t{++} classes are also
21341 represented as fields. If the type has no fields, or does not fit
21342 into one of these categories, an empty sequence will be returned.
21344 Each field is an object, with some pre-defined attributes:
21347 This attribute is not available for @code{static} fields (as in
21348 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21349 position of the field.
21352 The name of the field, or @code{None} for anonymous fields.
21355 This is @code{True} if the field is artificial, usually meaning that
21356 it was provided by the compiler and not the user. This attribute is
21357 always provided, and is @code{False} if the field is not artificial.
21359 @item is_base_class
21360 This is @code{True} if the field represents a base class of a C@t{++}
21361 structure. This attribute is always provided, and is @code{False}
21362 if the field is not a base class of the type that is the argument of
21363 @code{fields}, or if that type was not a C@t{++} class.
21366 If the field is packed, or is a bitfield, then this will have a
21367 non-zero value, which is the size of the field in bits. Otherwise,
21368 this will be zero; in this case the field's size is given by its type.
21371 The type of the field. This is usually an instance of @code{Type},
21372 but it can be @code{None} in some situations.
21376 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21377 Return a new @code{gdb.Type} object which represents an array of this
21378 type. If one argument is given, it is the inclusive upper bound of
21379 the array; in this case the lower bound is zero. If two arguments are
21380 given, the first argument is the lower bound of the array, and the
21381 second argument is the upper bound of the array. An array's length
21382 must not be negative, but the bounds can be.
21385 @defmethod Type const
21386 Return a new @code{gdb.Type} object which represents a
21387 @code{const}-qualified variant of this type.
21390 @defmethod Type volatile
21391 Return a new @code{gdb.Type} object which represents a
21392 @code{volatile}-qualified variant of this type.
21395 @defmethod Type unqualified
21396 Return a new @code{gdb.Type} object which represents an unqualified
21397 variant of this type. That is, the result is neither @code{const} nor
21401 @defmethod Type range
21402 Return a Python @code{Tuple} object that contains two elements: the
21403 low bound of the argument type and the high bound of that type. If
21404 the type does not have a range, @value{GDBN} will raise a
21405 @code{gdb.error} exception (@pxref{Exception Handling}).
21408 @defmethod Type reference
21409 Return a new @code{gdb.Type} object which represents a reference to this
21413 @defmethod Type pointer
21414 Return a new @code{gdb.Type} object which represents a pointer to this
21418 @defmethod Type strip_typedefs
21419 Return a new @code{gdb.Type} that represents the real type,
21420 after removing all layers of typedefs.
21423 @defmethod Type target
21424 Return a new @code{gdb.Type} object which represents the target type
21427 For a pointer type, the target type is the type of the pointed-to
21428 object. For an array type (meaning C-like arrays), the target type is
21429 the type of the elements of the array. For a function or method type,
21430 the target type is the type of the return value. For a complex type,
21431 the target type is the type of the elements. For a typedef, the
21432 target type is the aliased type.
21434 If the type does not have a target, this method will throw an
21438 @defmethod Type template_argument n [block]
21439 If this @code{gdb.Type} is an instantiation of a template, this will
21440 return a new @code{gdb.Type} which represents the type of the
21441 @var{n}th template argument.
21443 If this @code{gdb.Type} is not a template type, this will throw an
21444 exception. Ordinarily, only C@t{++} code will have template types.
21446 If @var{block} is given, then @var{name} is looked up in that scope.
21447 Otherwise, it is searched for globally.
21452 Each type has a code, which indicates what category this type falls
21453 into. The available type categories are represented by constants
21454 defined in the @code{gdb} module:
21457 @findex TYPE_CODE_PTR
21458 @findex gdb.TYPE_CODE_PTR
21459 @item TYPE_CODE_PTR
21460 The type is a pointer.
21462 @findex TYPE_CODE_ARRAY
21463 @findex gdb.TYPE_CODE_ARRAY
21464 @item TYPE_CODE_ARRAY
21465 The type is an array.
21467 @findex TYPE_CODE_STRUCT
21468 @findex gdb.TYPE_CODE_STRUCT
21469 @item TYPE_CODE_STRUCT
21470 The type is a structure.
21472 @findex TYPE_CODE_UNION
21473 @findex gdb.TYPE_CODE_UNION
21474 @item TYPE_CODE_UNION
21475 The type is a union.
21477 @findex TYPE_CODE_ENUM
21478 @findex gdb.TYPE_CODE_ENUM
21479 @item TYPE_CODE_ENUM
21480 The type is an enum.
21482 @findex TYPE_CODE_FLAGS
21483 @findex gdb.TYPE_CODE_FLAGS
21484 @item TYPE_CODE_FLAGS
21485 A bit flags type, used for things such as status registers.
21487 @findex TYPE_CODE_FUNC
21488 @findex gdb.TYPE_CODE_FUNC
21489 @item TYPE_CODE_FUNC
21490 The type is a function.
21492 @findex TYPE_CODE_INT
21493 @findex gdb.TYPE_CODE_INT
21494 @item TYPE_CODE_INT
21495 The type is an integer type.
21497 @findex TYPE_CODE_FLT
21498 @findex gdb.TYPE_CODE_FLT
21499 @item TYPE_CODE_FLT
21500 A floating point type.
21502 @findex TYPE_CODE_VOID
21503 @findex gdb.TYPE_CODE_VOID
21504 @item TYPE_CODE_VOID
21505 The special type @code{void}.
21507 @findex TYPE_CODE_SET
21508 @findex gdb.TYPE_CODE_SET
21509 @item TYPE_CODE_SET
21512 @findex TYPE_CODE_RANGE
21513 @findex gdb.TYPE_CODE_RANGE
21514 @item TYPE_CODE_RANGE
21515 A range type, that is, an integer type with bounds.
21517 @findex TYPE_CODE_STRING
21518 @findex gdb.TYPE_CODE_STRING
21519 @item TYPE_CODE_STRING
21520 A string type. Note that this is only used for certain languages with
21521 language-defined string types; C strings are not represented this way.
21523 @findex TYPE_CODE_BITSTRING
21524 @findex gdb.TYPE_CODE_BITSTRING
21525 @item TYPE_CODE_BITSTRING
21528 @findex TYPE_CODE_ERROR
21529 @findex gdb.TYPE_CODE_ERROR
21530 @item TYPE_CODE_ERROR
21531 An unknown or erroneous type.
21533 @findex TYPE_CODE_METHOD
21534 @findex gdb.TYPE_CODE_METHOD
21535 @item TYPE_CODE_METHOD
21536 A method type, as found in C@t{++} or Java.
21538 @findex TYPE_CODE_METHODPTR
21539 @findex gdb.TYPE_CODE_METHODPTR
21540 @item TYPE_CODE_METHODPTR
21541 A pointer-to-member-function.
21543 @findex TYPE_CODE_MEMBERPTR
21544 @findex gdb.TYPE_CODE_MEMBERPTR
21545 @item TYPE_CODE_MEMBERPTR
21546 A pointer-to-member.
21548 @findex TYPE_CODE_REF
21549 @findex gdb.TYPE_CODE_REF
21550 @item TYPE_CODE_REF
21553 @findex TYPE_CODE_CHAR
21554 @findex gdb.TYPE_CODE_CHAR
21555 @item TYPE_CODE_CHAR
21558 @findex TYPE_CODE_BOOL
21559 @findex gdb.TYPE_CODE_BOOL
21560 @item TYPE_CODE_BOOL
21563 @findex TYPE_CODE_COMPLEX
21564 @findex gdb.TYPE_CODE_COMPLEX
21565 @item TYPE_CODE_COMPLEX
21566 A complex float type.
21568 @findex TYPE_CODE_TYPEDEF
21569 @findex gdb.TYPE_CODE_TYPEDEF
21570 @item TYPE_CODE_TYPEDEF
21571 A typedef to some other type.
21573 @findex TYPE_CODE_NAMESPACE
21574 @findex gdb.TYPE_CODE_NAMESPACE
21575 @item TYPE_CODE_NAMESPACE
21576 A C@t{++} namespace.
21578 @findex TYPE_CODE_DECFLOAT
21579 @findex gdb.TYPE_CODE_DECFLOAT
21580 @item TYPE_CODE_DECFLOAT
21581 A decimal floating point type.
21583 @findex TYPE_CODE_INTERNAL_FUNCTION
21584 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21585 @item TYPE_CODE_INTERNAL_FUNCTION
21586 A function internal to @value{GDBN}. This is the type used to represent
21587 convenience functions.
21590 Further support for types is provided in the @code{gdb.types}
21591 Python module (@pxref{gdb.types}).
21593 @node Pretty Printing API
21594 @subsubsection Pretty Printing API
21596 An example output is provided (@pxref{Pretty Printing}).
21598 A pretty-printer is just an object that holds a value and implements a
21599 specific interface, defined here.
21601 @defop Operation {pretty printer} children (self)
21602 @value{GDBN} will call this method on a pretty-printer to compute the
21603 children of the pretty-printer's value.
21605 This method must return an object conforming to the Python iterator
21606 protocol. Each item returned by the iterator must be a tuple holding
21607 two elements. The first element is the ``name'' of the child; the
21608 second element is the child's value. The value can be any Python
21609 object which is convertible to a @value{GDBN} value.
21611 This method is optional. If it does not exist, @value{GDBN} will act
21612 as though the value has no children.
21615 @defop Operation {pretty printer} display_hint (self)
21616 The CLI may call this method and use its result to change the
21617 formatting of a value. The result will also be supplied to an MI
21618 consumer as a @samp{displayhint} attribute of the variable being
21621 This method is optional. If it does exist, this method must return a
21624 Some display hints are predefined by @value{GDBN}:
21628 Indicate that the object being printed is ``array-like''. The CLI
21629 uses this to respect parameters such as @code{set print elements} and
21630 @code{set print array}.
21633 Indicate that the object being printed is ``map-like'', and that the
21634 children of this value can be assumed to alternate between keys and
21638 Indicate that the object being printed is ``string-like''. If the
21639 printer's @code{to_string} method returns a Python string of some
21640 kind, then @value{GDBN} will call its internal language-specific
21641 string-printing function to format the string. For the CLI this means
21642 adding quotation marks, possibly escaping some characters, respecting
21643 @code{set print elements}, and the like.
21647 @defop Operation {pretty printer} to_string (self)
21648 @value{GDBN} will call this method to display the string
21649 representation of the value passed to the object's constructor.
21651 When printing from the CLI, if the @code{to_string} method exists,
21652 then @value{GDBN} will prepend its result to the values returned by
21653 @code{children}. Exactly how this formatting is done is dependent on
21654 the display hint, and may change as more hints are added. Also,
21655 depending on the print settings (@pxref{Print Settings}), the CLI may
21656 print just the result of @code{to_string} in a stack trace, omitting
21657 the result of @code{children}.
21659 If this method returns a string, it is printed verbatim.
21661 Otherwise, if this method returns an instance of @code{gdb.Value},
21662 then @value{GDBN} prints this value. This may result in a call to
21663 another pretty-printer.
21665 If instead the method returns a Python value which is convertible to a
21666 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21667 the resulting value. Again, this may result in a call to another
21668 pretty-printer. Python scalars (integers, floats, and booleans) and
21669 strings are convertible to @code{gdb.Value}; other types are not.
21671 Finally, if this method returns @code{None} then no further operations
21672 are peformed in this method and nothing is printed.
21674 If the result is not one of these types, an exception is raised.
21677 @value{GDBN} provides a function which can be used to look up the
21678 default pretty-printer for a @code{gdb.Value}:
21680 @findex gdb.default_visualizer
21681 @defun default_visualizer value
21682 This function takes a @code{gdb.Value} object as an argument. If a
21683 pretty-printer for this value exists, then it is returned. If no such
21684 printer exists, then this returns @code{None}.
21687 @node Selecting Pretty-Printers
21688 @subsubsection Selecting Pretty-Printers
21690 The Python list @code{gdb.pretty_printers} contains an array of
21691 functions or callable objects that have been registered via addition
21692 as a pretty-printer. Printers in this list are called @code{global}
21693 printers, they're available when debugging all inferiors.
21694 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21695 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21698 Each function on these lists is passed a single @code{gdb.Value}
21699 argument and should return a pretty-printer object conforming to the
21700 interface definition above (@pxref{Pretty Printing API}). If a function
21701 cannot create a pretty-printer for the value, it should return
21704 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21705 @code{gdb.Objfile} in the current program space and iteratively calls
21706 each enabled lookup routine in the list for that @code{gdb.Objfile}
21707 until it receives a pretty-printer object.
21708 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21709 searches the pretty-printer list of the current program space,
21710 calling each enabled function until an object is returned.
21711 After these lists have been exhausted, it tries the global
21712 @code{gdb.pretty_printers} list, again calling each enabled function until an
21713 object is returned.
21715 The order in which the objfiles are searched is not specified. For a
21716 given list, functions are always invoked from the head of the list,
21717 and iterated over sequentially until the end of the list, or a printer
21718 object is returned.
21720 For various reasons a pretty-printer may not work.
21721 For example, the underlying data structure may have changed and
21722 the pretty-printer is out of date.
21724 The consequences of a broken pretty-printer are severe enough that
21725 @value{GDBN} provides support for enabling and disabling individual
21726 printers. For example, if @code{print frame-arguments} is on,
21727 a backtrace can become highly illegible if any argument is printed
21728 with a broken printer.
21730 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21731 attribute to the registered function or callable object. If this attribute
21732 is present and its value is @code{False}, the printer is disabled, otherwise
21733 the printer is enabled.
21735 @node Writing a Pretty-Printer
21736 @subsubsection Writing a Pretty-Printer
21737 @cindex writing a pretty-printer
21739 A pretty-printer consists of two parts: a lookup function to detect
21740 if the type is supported, and the printer itself.
21742 Here is an example showing how a @code{std::string} printer might be
21743 written. @xref{Pretty Printing API}, for details on the API this class
21747 class StdStringPrinter(object):
21748 "Print a std::string"
21750 def __init__(self, val):
21753 def to_string(self):
21754 return self.val['_M_dataplus']['_M_p']
21756 def display_hint(self):
21760 And here is an example showing how a lookup function for the printer
21761 example above might be written.
21764 def str_lookup_function(val):
21765 lookup_tag = val.type.tag
21766 if lookup_tag == None:
21768 regex = re.compile("^std::basic_string<char,.*>$")
21769 if regex.match(lookup_tag):
21770 return StdStringPrinter(val)
21774 The example lookup function extracts the value's type, and attempts to
21775 match it to a type that it can pretty-print. If it is a type the
21776 printer can pretty-print, it will return a printer object. If not, it
21777 returns @code{None}.
21779 We recommend that you put your core pretty-printers into a Python
21780 package. If your pretty-printers are for use with a library, we
21781 further recommend embedding a version number into the package name.
21782 This practice will enable @value{GDBN} to load multiple versions of
21783 your pretty-printers at the same time, because they will have
21786 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21787 can be evaluated multiple times without changing its meaning. An
21788 ideal auto-load file will consist solely of @code{import}s of your
21789 printer modules, followed by a call to a register pretty-printers with
21790 the current objfile.
21792 Taken as a whole, this approach will scale nicely to multiple
21793 inferiors, each potentially using a different library version.
21794 Embedding a version number in the Python package name will ensure that
21795 @value{GDBN} is able to load both sets of printers simultaneously.
21796 Then, because the search for pretty-printers is done by objfile, and
21797 because your auto-loaded code took care to register your library's
21798 printers with a specific objfile, @value{GDBN} will find the correct
21799 printers for the specific version of the library used by each
21802 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21803 this code might appear in @code{gdb.libstdcxx.v6}:
21806 def register_printers(objfile):
21807 objfile.pretty_printers.add(str_lookup_function)
21811 And then the corresponding contents of the auto-load file would be:
21814 import gdb.libstdcxx.v6
21815 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21818 The previous example illustrates a basic pretty-printer.
21819 There are a few things that can be improved on.
21820 The printer doesn't have a name, making it hard to identify in a
21821 list of installed printers. The lookup function has a name, but
21822 lookup functions can have arbitrary, even identical, names.
21824 Second, the printer only handles one type, whereas a library typically has
21825 several types. One could install a lookup function for each desired type
21826 in the library, but one could also have a single lookup function recognize
21827 several types. The latter is the conventional way this is handled.
21828 If a pretty-printer can handle multiple data types, then its
21829 @dfn{subprinters} are the printers for the individual data types.
21831 The @code{gdb.printing} module provides a formal way of solving these
21832 problems (@pxref{gdb.printing}).
21833 Here is another example that handles multiple types.
21835 These are the types we are going to pretty-print:
21838 struct foo @{ int a, b; @};
21839 struct bar @{ struct foo x, y; @};
21842 Here are the printers:
21846 """Print a foo object."""
21848 def __init__(self, val):
21851 def to_string(self):
21852 return ("a=<" + str(self.val["a"]) +
21853 "> b=<" + str(self.val["b"]) + ">")
21856 """Print a bar object."""
21858 def __init__(self, val):
21861 def to_string(self):
21862 return ("x=<" + str(self.val["x"]) +
21863 "> y=<" + str(self.val["y"]) + ">")
21866 This example doesn't need a lookup function, that is handled by the
21867 @code{gdb.printing} module. Instead a function is provided to build up
21868 the object that handles the lookup.
21871 import gdb.printing
21873 def build_pretty_printer():
21874 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21876 pp.add_printer('foo', '^foo$', fooPrinter)
21877 pp.add_printer('bar', '^bar$', barPrinter)
21881 And here is the autoload support:
21884 import gdb.printing
21886 gdb.printing.register_pretty_printer(
21887 gdb.current_objfile(),
21888 my_library.build_pretty_printer())
21891 Finally, when this printer is loaded into @value{GDBN}, here is the
21892 corresponding output of @samp{info pretty-printer}:
21895 (gdb) info pretty-printer
21902 @node Inferiors In Python
21903 @subsubsection Inferiors In Python
21904 @cindex inferiors in Python
21906 @findex gdb.Inferior
21907 Programs which are being run under @value{GDBN} are called inferiors
21908 (@pxref{Inferiors and Programs}). Python scripts can access
21909 information about and manipulate inferiors controlled by @value{GDBN}
21910 via objects of the @code{gdb.Inferior} class.
21912 The following inferior-related functions are available in the @code{gdb}
21916 Return a tuple containing all inferior objects.
21919 A @code{gdb.Inferior} object has the following attributes:
21922 @defivar Inferior num
21923 ID of inferior, as assigned by GDB.
21926 @defivar Inferior pid
21927 Process ID of the inferior, as assigned by the underlying operating
21931 @defivar Inferior was_attached
21932 Boolean signaling whether the inferior was created using `attach', or
21933 started by @value{GDBN} itself.
21937 A @code{gdb.Inferior} object has the following methods:
21940 @defmethod Inferior is_valid
21941 Returns @code{True} if the @code{gdb.Inferior} object is valid,
21942 @code{False} if not. A @code{gdb.Inferior} object will become invalid
21943 if the inferior no longer exists within @value{GDBN}. All other
21944 @code{gdb.Inferior} methods will throw an exception if it is invalid
21945 at the time the method is called.
21948 @defmethod Inferior threads
21949 This method returns a tuple holding all the threads which are valid
21950 when it is called. If there are no valid threads, the method will
21951 return an empty tuple.
21954 @findex gdb.read_memory
21955 @defmethod Inferior read_memory address length
21956 Read @var{length} bytes of memory from the inferior, starting at
21957 @var{address}. Returns a buffer object, which behaves much like an array
21958 or a string. It can be modified and given to the @code{gdb.write_memory}
21962 @findex gdb.write_memory
21963 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21964 Write the contents of @var{buffer} to the inferior, starting at
21965 @var{address}. The @var{buffer} parameter must be a Python object
21966 which supports the buffer protocol, i.e., a string, an array or the
21967 object returned from @code{gdb.read_memory}. If given, @var{length}
21968 determines the number of bytes from @var{buffer} to be written.
21971 @findex gdb.search_memory
21972 @defmethod Inferior search_memory address length pattern
21973 Search a region of the inferior memory starting at @var{address} with
21974 the given @var{length} using the search pattern supplied in
21975 @var{pattern}. The @var{pattern} parameter must be a Python object
21976 which supports the buffer protocol, i.e., a string, an array or the
21977 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21978 containing the address where the pattern was found, or @code{None} if
21979 the pattern could not be found.
21983 @node Events In Python
21984 @subsubsection Events In Python
21985 @cindex inferior events in Python
21987 @value{GDBN} provides a general event facility so that Python code can be
21988 notified of various state changes, particularly changes that occur in
21991 An @dfn{event} is just an object that describes some state change. The
21992 type of the object and its attributes will vary depending on the details
21993 of the change. All the existing events are described below.
21995 In order to be notified of an event, you must register an event handler
21996 with an @dfn{event registry}. An event registry is an object in the
21997 @code{gdb.events} module which dispatches particular events. A registry
21998 provides methods to register and unregister event handlers:
22001 @defmethod EventRegistry connect object
22002 Add the given callable @var{object} to the registry. This object will be
22003 called when an event corresponding to this registry occurs.
22006 @defmethod EventRegistry disconnect object
22007 Remove the given @var{object} from the registry. Once removed, the object
22008 will no longer receive notifications of events.
22012 Here is an example:
22015 def exit_handler (event):
22016 print "event type: exit"
22017 print "exit code: %d" % (event.exit_code)
22019 gdb.events.exited.connect (exit_handler)
22022 In the above example we connect our handler @code{exit_handler} to the
22023 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22024 called when the inferior exits. The argument @dfn{event} in this example is
22025 of type @code{gdb.ExitedEvent}. As you can see in the example the
22026 @code{ExitedEvent} object has an attribute which indicates the exit code of
22029 The following is a listing of the event registries that are available and
22030 details of the events they emit:
22035 Emits @code{gdb.ThreadEvent}.
22037 Some events can be thread specific when @value{GDBN} is running in non-stop
22038 mode. When represented in Python, these events all extend
22039 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22040 events which are emitted by this or other modules might extend this event.
22041 Examples of these events are @code{gdb.BreakpointEvent} and
22042 @code{gdb.ContinueEvent}.
22045 @defivar ThreadEvent inferior_thread
22046 In non-stop mode this attribute will be set to the specific thread which was
22047 involved in the emitted event. Otherwise, it will be set to @code{None}.
22051 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22053 This event indicates that the inferior has been continued after a stop. For
22054 inherited attribute refer to @code{gdb.ThreadEvent} above.
22056 @item events.exited
22057 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22058 @code{events.ExitedEvent} has one attribute:
22060 @defivar ExitedEvent exit_code
22061 An integer representing the exit code which the inferior has returned.
22066 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22068 Indicates that the inferior has stopped. All events emitted by this registry
22069 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22070 will indicate the stopped thread when @value{GDBN} is running in non-stop
22071 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22073 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22075 This event indicates that the inferior or one of its threads has received as
22076 signal. @code{gdb.SignalEvent} has the following attributes:
22079 @defivar SignalEvent stop_signal
22080 A string representing the signal received by the inferior. A list of possible
22081 signal values can be obtained by running the command @code{info signals} in
22082 the @value{GDBN} command prompt.
22086 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22088 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22089 has the following attributes:
22092 @defivar BreakpointEvent breakpoint
22093 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22094 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22100 @node Threads In Python
22101 @subsubsection Threads In Python
22102 @cindex threads in python
22104 @findex gdb.InferiorThread
22105 Python scripts can access information about, and manipulate inferior threads
22106 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22108 The following thread-related functions are available in the @code{gdb}
22111 @findex gdb.selected_thread
22112 @defun selected_thread
22113 This function returns the thread object for the selected thread. If there
22114 is no selected thread, this will return @code{None}.
22117 A @code{gdb.InferiorThread} object has the following attributes:
22120 @defivar InferiorThread name
22121 The name of the thread. If the user specified a name using
22122 @code{thread name}, then this returns that name. Otherwise, if an
22123 OS-supplied name is available, then it is returned. Otherwise, this
22124 returns @code{None}.
22126 This attribute can be assigned to. The new value must be a string
22127 object, which sets the new name, or @code{None}, which removes any
22128 user-specified thread name.
22131 @defivar InferiorThread num
22132 ID of the thread, as assigned by GDB.
22135 @defivar InferiorThread ptid
22136 ID of the thread, as assigned by the operating system. This attribute is a
22137 tuple containing three integers. The first is the Process ID (PID); the second
22138 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22139 Either the LWPID or TID may be 0, which indicates that the operating system
22140 does not use that identifier.
22144 A @code{gdb.InferiorThread} object has the following methods:
22147 @defmethod InferiorThread is_valid
22148 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22149 @code{False} if not. A @code{gdb.InferiorThread} object will become
22150 invalid if the thread exits, or the inferior that the thread belongs
22151 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22152 exception if it is invalid at the time the method is called.
22155 @defmethod InferiorThread switch
22156 This changes @value{GDBN}'s currently selected thread to the one represented
22160 @defmethod InferiorThread is_stopped
22161 Return a Boolean indicating whether the thread is stopped.
22164 @defmethod InferiorThread is_running
22165 Return a Boolean indicating whether the thread is running.
22168 @defmethod InferiorThread is_exited
22169 Return a Boolean indicating whether the thread is exited.
22173 @node Commands In Python
22174 @subsubsection Commands In Python
22176 @cindex commands in python
22177 @cindex python commands
22178 You can implement new @value{GDBN} CLI commands in Python. A CLI
22179 command is implemented using an instance of the @code{gdb.Command}
22180 class, most commonly using a subclass.
22182 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22183 The object initializer for @code{Command} registers the new command
22184 with @value{GDBN}. This initializer is normally invoked from the
22185 subclass' own @code{__init__} method.
22187 @var{name} is the name of the command. If @var{name} consists of
22188 multiple words, then the initial words are looked for as prefix
22189 commands. In this case, if one of the prefix commands does not exist,
22190 an exception is raised.
22192 There is no support for multi-line commands.
22194 @var{command_class} should be one of the @samp{COMMAND_} constants
22195 defined below. This argument tells @value{GDBN} how to categorize the
22196 new command in the help system.
22198 @var{completer_class} is an optional argument. If given, it should be
22199 one of the @samp{COMPLETE_} constants defined below. This argument
22200 tells @value{GDBN} how to perform completion for this command. If not
22201 given, @value{GDBN} will attempt to complete using the object's
22202 @code{complete} method (see below); if no such method is found, an
22203 error will occur when completion is attempted.
22205 @var{prefix} is an optional argument. If @code{True}, then the new
22206 command is a prefix command; sub-commands of this command may be
22209 The help text for the new command is taken from the Python
22210 documentation string for the command's class, if there is one. If no
22211 documentation string is provided, the default value ``This command is
22212 not documented.'' is used.
22215 @cindex don't repeat Python command
22216 @defmethod Command dont_repeat
22217 By default, a @value{GDBN} command is repeated when the user enters a
22218 blank line at the command prompt. A command can suppress this
22219 behavior by invoking the @code{dont_repeat} method. This is similar
22220 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22223 @defmethod Command invoke argument from_tty
22224 This method is called by @value{GDBN} when this command is invoked.
22226 @var{argument} is a string. It is the argument to the command, after
22227 leading and trailing whitespace has been stripped.
22229 @var{from_tty} is a boolean argument. When true, this means that the
22230 command was entered by the user at the terminal; when false it means
22231 that the command came from elsewhere.
22233 If this method throws an exception, it is turned into a @value{GDBN}
22234 @code{error} call. Otherwise, the return value is ignored.
22236 @findex gdb.string_to_argv
22237 To break @var{argument} up into an argv-like string use
22238 @code{gdb.string_to_argv}. This function behaves identically to
22239 @value{GDBN}'s internal argument lexer @code{buildargv}.
22240 It is recommended to use this for consistency.
22241 Arguments are separated by spaces and may be quoted.
22245 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22246 ['1', '2 "3', '4 "5', "6 '7"]
22251 @cindex completion of Python commands
22252 @defmethod Command complete text word
22253 This method is called by @value{GDBN} when the user attempts
22254 completion on this command. All forms of completion are handled by
22255 this method, that is, the @key{TAB} and @key{M-?} key bindings
22256 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22259 The arguments @var{text} and @var{word} are both strings. @var{text}
22260 holds the complete command line up to the cursor's location.
22261 @var{word} holds the last word of the command line; this is computed
22262 using a word-breaking heuristic.
22264 The @code{complete} method can return several values:
22267 If the return value is a sequence, the contents of the sequence are
22268 used as the completions. It is up to @code{complete} to ensure that the
22269 contents actually do complete the word. A zero-length sequence is
22270 allowed, it means that there were no completions available. Only
22271 string elements of the sequence are used; other elements in the
22272 sequence are ignored.
22275 If the return value is one of the @samp{COMPLETE_} constants defined
22276 below, then the corresponding @value{GDBN}-internal completion
22277 function is invoked, and its result is used.
22280 All other results are treated as though there were no available
22285 When a new command is registered, it must be declared as a member of
22286 some general class of commands. This is used to classify top-level
22287 commands in the on-line help system; note that prefix commands are not
22288 listed under their own category but rather that of their top-level
22289 command. The available classifications are represented by constants
22290 defined in the @code{gdb} module:
22293 @findex COMMAND_NONE
22294 @findex gdb.COMMAND_NONE
22296 The command does not belong to any particular class. A command in
22297 this category will not be displayed in any of the help categories.
22299 @findex COMMAND_RUNNING
22300 @findex gdb.COMMAND_RUNNING
22301 @item COMMAND_RUNNING
22302 The command is related to running the inferior. For example,
22303 @code{start}, @code{step}, and @code{continue} are in this category.
22304 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22305 commands in this category.
22307 @findex COMMAND_DATA
22308 @findex gdb.COMMAND_DATA
22310 The command is related to data or variables. For example,
22311 @code{call}, @code{find}, and @code{print} are in this category. Type
22312 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22315 @findex COMMAND_STACK
22316 @findex gdb.COMMAND_STACK
22317 @item COMMAND_STACK
22318 The command has to do with manipulation of the stack. For example,
22319 @code{backtrace}, @code{frame}, and @code{return} are in this
22320 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22321 list of commands in this category.
22323 @findex COMMAND_FILES
22324 @findex gdb.COMMAND_FILES
22325 @item COMMAND_FILES
22326 This class is used for file-related commands. For example,
22327 @code{file}, @code{list} and @code{section} are in this category.
22328 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22329 commands in this category.
22331 @findex COMMAND_SUPPORT
22332 @findex gdb.COMMAND_SUPPORT
22333 @item COMMAND_SUPPORT
22334 This should be used for ``support facilities'', generally meaning
22335 things that are useful to the user when interacting with @value{GDBN},
22336 but not related to the state of the inferior. For example,
22337 @code{help}, @code{make}, and @code{shell} are in this category. Type
22338 @kbd{help support} at the @value{GDBN} prompt to see a list of
22339 commands in this category.
22341 @findex COMMAND_STATUS
22342 @findex gdb.COMMAND_STATUS
22343 @item COMMAND_STATUS
22344 The command is an @samp{info}-related command, that is, related to the
22345 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22346 and @code{show} are in this category. Type @kbd{help status} at the
22347 @value{GDBN} prompt to see a list of commands in this category.
22349 @findex COMMAND_BREAKPOINTS
22350 @findex gdb.COMMAND_BREAKPOINTS
22351 @item COMMAND_BREAKPOINTS
22352 The command has to do with breakpoints. For example, @code{break},
22353 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22354 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22357 @findex COMMAND_TRACEPOINTS
22358 @findex gdb.COMMAND_TRACEPOINTS
22359 @item COMMAND_TRACEPOINTS
22360 The command has to do with tracepoints. For example, @code{trace},
22361 @code{actions}, and @code{tfind} are in this category. Type
22362 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22363 commands in this category.
22365 @findex COMMAND_OBSCURE
22366 @findex gdb.COMMAND_OBSCURE
22367 @item COMMAND_OBSCURE
22368 The command is only used in unusual circumstances, or is not of
22369 general interest to users. For example, @code{checkpoint},
22370 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22371 obscure} at the @value{GDBN} prompt to see a list of commands in this
22374 @findex COMMAND_MAINTENANCE
22375 @findex gdb.COMMAND_MAINTENANCE
22376 @item COMMAND_MAINTENANCE
22377 The command is only useful to @value{GDBN} maintainers. The
22378 @code{maintenance} and @code{flushregs} commands are in this category.
22379 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22380 commands in this category.
22383 A new command can use a predefined completion function, either by
22384 specifying it via an argument at initialization, or by returning it
22385 from the @code{complete} method. These predefined completion
22386 constants are all defined in the @code{gdb} module:
22389 @findex COMPLETE_NONE
22390 @findex gdb.COMPLETE_NONE
22391 @item COMPLETE_NONE
22392 This constant means that no completion should be done.
22394 @findex COMPLETE_FILENAME
22395 @findex gdb.COMPLETE_FILENAME
22396 @item COMPLETE_FILENAME
22397 This constant means that filename completion should be performed.
22399 @findex COMPLETE_LOCATION
22400 @findex gdb.COMPLETE_LOCATION
22401 @item COMPLETE_LOCATION
22402 This constant means that location completion should be done.
22403 @xref{Specify Location}.
22405 @findex COMPLETE_COMMAND
22406 @findex gdb.COMPLETE_COMMAND
22407 @item COMPLETE_COMMAND
22408 This constant means that completion should examine @value{GDBN}
22411 @findex COMPLETE_SYMBOL
22412 @findex gdb.COMPLETE_SYMBOL
22413 @item COMPLETE_SYMBOL
22414 This constant means that completion should be done using symbol names
22418 The following code snippet shows how a trivial CLI command can be
22419 implemented in Python:
22422 class HelloWorld (gdb.Command):
22423 """Greet the whole world."""
22425 def __init__ (self):
22426 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22428 def invoke (self, arg, from_tty):
22429 print "Hello, World!"
22434 The last line instantiates the class, and is necessary to trigger the
22435 registration of the command with @value{GDBN}. Depending on how the
22436 Python code is read into @value{GDBN}, you may need to import the
22437 @code{gdb} module explicitly.
22439 @node Parameters In Python
22440 @subsubsection Parameters In Python
22442 @cindex parameters in python
22443 @cindex python parameters
22444 @tindex gdb.Parameter
22446 You can implement new @value{GDBN} parameters using Python. A new
22447 parameter is implemented as an instance of the @code{gdb.Parameter}
22450 Parameters are exposed to the user via the @code{set} and
22451 @code{show} commands. @xref{Help}.
22453 There are many parameters that already exist and can be set in
22454 @value{GDBN}. Two examples are: @code{set follow fork} and
22455 @code{set charset}. Setting these parameters influences certain
22456 behavior in @value{GDBN}. Similarly, you can define parameters that
22457 can be used to influence behavior in custom Python scripts and commands.
22459 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22460 The object initializer for @code{Parameter} registers the new
22461 parameter with @value{GDBN}. This initializer is normally invoked
22462 from the subclass' own @code{__init__} method.
22464 @var{name} is the name of the new parameter. If @var{name} consists
22465 of multiple words, then the initial words are looked for as prefix
22466 parameters. An example of this can be illustrated with the
22467 @code{set print} set of parameters. If @var{name} is
22468 @code{print foo}, then @code{print} will be searched as the prefix
22469 parameter. In this case the parameter can subsequently be accessed in
22470 @value{GDBN} as @code{set print foo}.
22472 If @var{name} consists of multiple words, and no prefix parameter group
22473 can be found, an exception is raised.
22475 @var{command-class} should be one of the @samp{COMMAND_} constants
22476 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22477 categorize the new parameter in the help system.
22479 @var{parameter-class} should be one of the @samp{PARAM_} constants
22480 defined below. This argument tells @value{GDBN} the type of the new
22481 parameter; this information is used for input validation and
22484 If @var{parameter-class} is @code{PARAM_ENUM}, then
22485 @var{enum-sequence} must be a sequence of strings. These strings
22486 represent the possible values for the parameter.
22488 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22489 of a fourth argument will cause an exception to be thrown.
22491 The help text for the new parameter is taken from the Python
22492 documentation string for the parameter's class, if there is one. If
22493 there is no documentation string, a default value is used.
22496 @defivar Parameter set_doc
22497 If this attribute exists, and is a string, then its value is used as
22498 the help text for this parameter's @code{set} command. The value is
22499 examined when @code{Parameter.__init__} is invoked; subsequent changes
22503 @defivar Parameter show_doc
22504 If this attribute exists, and is a string, then its value is used as
22505 the help text for this parameter's @code{show} command. The value is
22506 examined when @code{Parameter.__init__} is invoked; subsequent changes
22510 @defivar Parameter value
22511 The @code{value} attribute holds the underlying value of the
22512 parameter. It can be read and assigned to just as any other
22513 attribute. @value{GDBN} does validation when assignments are made.
22516 There are two methods that should be implemented in any
22517 @code{Parameter} class. These are:
22519 @defop Operation {parameter} get_set_string self
22520 @value{GDBN} will call this method when a @var{parameter}'s value has
22521 been changed via the @code{set} API (for example, @kbd{set foo off}).
22522 The @code{value} attribute has already been populated with the new
22523 value and may be used in output. This method must return a string.
22526 @defop Operation {parameter} get_show_string self svalue
22527 @value{GDBN} will call this method when a @var{parameter}'s
22528 @code{show} API has been invoked (for example, @kbd{show foo}). The
22529 argument @code{svalue} receives the string representation of the
22530 current value. This method must return a string.
22533 When a new parameter is defined, its type must be specified. The
22534 available types are represented by constants defined in the @code{gdb}
22538 @findex PARAM_BOOLEAN
22539 @findex gdb.PARAM_BOOLEAN
22540 @item PARAM_BOOLEAN
22541 The value is a plain boolean. The Python boolean values, @code{True}
22542 and @code{False} are the only valid values.
22544 @findex PARAM_AUTO_BOOLEAN
22545 @findex gdb.PARAM_AUTO_BOOLEAN
22546 @item PARAM_AUTO_BOOLEAN
22547 The value has three possible states: true, false, and @samp{auto}. In
22548 Python, true and false are represented using boolean constants, and
22549 @samp{auto} is represented using @code{None}.
22551 @findex PARAM_UINTEGER
22552 @findex gdb.PARAM_UINTEGER
22553 @item PARAM_UINTEGER
22554 The value is an unsigned integer. The value of 0 should be
22555 interpreted to mean ``unlimited''.
22557 @findex PARAM_INTEGER
22558 @findex gdb.PARAM_INTEGER
22559 @item PARAM_INTEGER
22560 The value is a signed integer. The value of 0 should be interpreted
22561 to mean ``unlimited''.
22563 @findex PARAM_STRING
22564 @findex gdb.PARAM_STRING
22566 The value is a string. When the user modifies the string, any escape
22567 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22568 translated into corresponding characters and encoded into the current
22571 @findex PARAM_STRING_NOESCAPE
22572 @findex gdb.PARAM_STRING_NOESCAPE
22573 @item PARAM_STRING_NOESCAPE
22574 The value is a string. When the user modifies the string, escapes are
22575 passed through untranslated.
22577 @findex PARAM_OPTIONAL_FILENAME
22578 @findex gdb.PARAM_OPTIONAL_FILENAME
22579 @item PARAM_OPTIONAL_FILENAME
22580 The value is a either a filename (a string), or @code{None}.
22582 @findex PARAM_FILENAME
22583 @findex gdb.PARAM_FILENAME
22584 @item PARAM_FILENAME
22585 The value is a filename. This is just like
22586 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22588 @findex PARAM_ZINTEGER
22589 @findex gdb.PARAM_ZINTEGER
22590 @item PARAM_ZINTEGER
22591 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22592 is interpreted as itself.
22595 @findex gdb.PARAM_ENUM
22597 The value is a string, which must be one of a collection string
22598 constants provided when the parameter is created.
22601 @node Functions In Python
22602 @subsubsection Writing new convenience functions
22604 @cindex writing convenience functions
22605 @cindex convenience functions in python
22606 @cindex python convenience functions
22607 @tindex gdb.Function
22609 You can implement new convenience functions (@pxref{Convenience Vars})
22610 in Python. A convenience function is an instance of a subclass of the
22611 class @code{gdb.Function}.
22613 @defmethod Function __init__ name
22614 The initializer for @code{Function} registers the new function with
22615 @value{GDBN}. The argument @var{name} is the name of the function,
22616 a string. The function will be visible to the user as a convenience
22617 variable of type @code{internal function}, whose name is the same as
22618 the given @var{name}.
22620 The documentation for the new function is taken from the documentation
22621 string for the new class.
22624 @defmethod Function invoke @var{*args}
22625 When a convenience function is evaluated, its arguments are converted
22626 to instances of @code{gdb.Value}, and then the function's
22627 @code{invoke} method is called. Note that @value{GDBN} does not
22628 predetermine the arity of convenience functions. Instead, all
22629 available arguments are passed to @code{invoke}, following the
22630 standard Python calling convention. In particular, a convenience
22631 function can have default values for parameters without ill effect.
22633 The return value of this method is used as its value in the enclosing
22634 expression. If an ordinary Python value is returned, it is converted
22635 to a @code{gdb.Value} following the usual rules.
22638 The following code snippet shows how a trivial convenience function can
22639 be implemented in Python:
22642 class Greet (gdb.Function):
22643 """Return string to greet someone.
22644 Takes a name as argument."""
22646 def __init__ (self):
22647 super (Greet, self).__init__ ("greet")
22649 def invoke (self, name):
22650 return "Hello, %s!" % name.string ()
22655 The last line instantiates the class, and is necessary to trigger the
22656 registration of the function with @value{GDBN}. Depending on how the
22657 Python code is read into @value{GDBN}, you may need to import the
22658 @code{gdb} module explicitly.
22660 @node Progspaces In Python
22661 @subsubsection Program Spaces In Python
22663 @cindex progspaces in python
22664 @tindex gdb.Progspace
22666 A program space, or @dfn{progspace}, represents a symbolic view
22667 of an address space.
22668 It consists of all of the objfiles of the program.
22669 @xref{Objfiles In Python}.
22670 @xref{Inferiors and Programs, program spaces}, for more details
22671 about program spaces.
22673 The following progspace-related functions are available in the
22676 @findex gdb.current_progspace
22677 @defun current_progspace
22678 This function returns the program space of the currently selected inferior.
22679 @xref{Inferiors and Programs}.
22682 @findex gdb.progspaces
22684 Return a sequence of all the progspaces currently known to @value{GDBN}.
22687 Each progspace is represented by an instance of the @code{gdb.Progspace}
22690 @defivar Progspace filename
22691 The file name of the progspace as a string.
22694 @defivar Progspace pretty_printers
22695 The @code{pretty_printers} attribute is a list of functions. It is
22696 used to look up pretty-printers. A @code{Value} is passed to each
22697 function in order; if the function returns @code{None}, then the
22698 search continues. Otherwise, the return value should be an object
22699 which is used to format the value. @xref{Pretty Printing API}, for more
22703 @node Objfiles In Python
22704 @subsubsection Objfiles In Python
22706 @cindex objfiles in python
22707 @tindex gdb.Objfile
22709 @value{GDBN} loads symbols for an inferior from various
22710 symbol-containing files (@pxref{Files}). These include the primary
22711 executable file, any shared libraries used by the inferior, and any
22712 separate debug info files (@pxref{Separate Debug Files}).
22713 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22715 The following objfile-related functions are available in the
22718 @findex gdb.current_objfile
22719 @defun current_objfile
22720 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22721 sets the ``current objfile'' to the corresponding objfile. This
22722 function returns the current objfile. If there is no current objfile,
22723 this function returns @code{None}.
22726 @findex gdb.objfiles
22728 Return a sequence of all the objfiles current known to @value{GDBN}.
22729 @xref{Objfiles In Python}.
22732 Each objfile is represented by an instance of the @code{gdb.Objfile}
22735 @defivar Objfile filename
22736 The file name of the objfile as a string.
22739 @defivar Objfile pretty_printers
22740 The @code{pretty_printers} attribute is a list of functions. It is
22741 used to look up pretty-printers. A @code{Value} is passed to each
22742 function in order; if the function returns @code{None}, then the
22743 search continues. Otherwise, the return value should be an object
22744 which is used to format the value. @xref{Pretty Printing API}, for more
22748 A @code{gdb.Objfile} object has the following methods:
22750 @defmethod Objfile is_valid
22751 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22752 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22753 if the object file it refers to is not loaded in @value{GDBN} any
22754 longer. All other @code{gdb.Objfile} methods will throw an exception
22755 if it is invalid at the time the method is called.
22758 @node Frames In Python
22759 @subsubsection Accessing inferior stack frames from Python.
22761 @cindex frames in python
22762 When the debugged program stops, @value{GDBN} is able to analyze its call
22763 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22764 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22765 while its corresponding frame exists in the inferior's stack. If you try
22766 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22767 exception (@pxref{Exception Handling}).
22769 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22773 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22777 The following frame-related functions are available in the @code{gdb} module:
22779 @findex gdb.selected_frame
22780 @defun selected_frame
22781 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22784 @findex gdb.newest_frame
22785 @defun newest_frame
22786 Return the newest frame object for the selected thread.
22789 @defun frame_stop_reason_string reason
22790 Return a string explaining the reason why @value{GDBN} stopped unwinding
22791 frames, as expressed by the given @var{reason} code (an integer, see the
22792 @code{unwind_stop_reason} method further down in this section).
22795 A @code{gdb.Frame} object has the following methods:
22798 @defmethod Frame is_valid
22799 Returns true if the @code{gdb.Frame} object is valid, false if not.
22800 A frame object can become invalid if the frame it refers to doesn't
22801 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22802 an exception if it is invalid at the time the method is called.
22805 @defmethod Frame name
22806 Returns the function name of the frame, or @code{None} if it can't be
22810 @defmethod Frame type
22811 Returns the type of the frame. The value can be one of:
22813 @item gdb.NORMAL_FRAME
22814 An ordinary stack frame.
22816 @item gdb.DUMMY_FRAME
22817 A fake stack frame that was created by @value{GDBN} when performing an
22818 inferior function call.
22820 @item gdb.INLINE_FRAME
22821 A frame representing an inlined function. The function was inlined
22822 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22824 @item gdb.SIGTRAMP_FRAME
22825 A signal trampoline frame. This is the frame created by the OS when
22826 it calls into a signal handler.
22828 @item gdb.ARCH_FRAME
22829 A fake stack frame representing a cross-architecture call.
22831 @item gdb.SENTINEL_FRAME
22832 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22837 @defmethod Frame unwind_stop_reason
22838 Return an integer representing the reason why it's not possible to find
22839 more frames toward the outermost frame. Use
22840 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22841 function to a string.
22844 @defmethod Frame pc
22845 Returns the frame's resume address.
22848 @defmethod Frame block
22849 Return the frame's code block. @xref{Blocks In Python}.
22852 @defmethod Frame function
22853 Return the symbol for the function corresponding to this frame.
22854 @xref{Symbols In Python}.
22857 @defmethod Frame older
22858 Return the frame that called this frame.
22861 @defmethod Frame newer
22862 Return the frame called by this frame.
22865 @defmethod Frame find_sal
22866 Return the frame's symtab and line object.
22867 @xref{Symbol Tables In Python}.
22870 @defmethod Frame read_var variable @r{[}block@r{]}
22871 Return the value of @var{variable} in this frame. If the optional
22872 argument @var{block} is provided, search for the variable from that
22873 block; otherwise start at the frame's current block (which is
22874 determined by the frame's current program counter). @var{variable}
22875 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22876 @code{gdb.Block} object.
22879 @defmethod Frame select
22880 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22885 @node Blocks In Python
22886 @subsubsection Accessing frame blocks from Python.
22888 @cindex blocks in python
22891 Within each frame, @value{GDBN} maintains information on each block
22892 stored in that frame. These blocks are organized hierarchically, and
22893 are represented individually in Python as a @code{gdb.Block}.
22894 Please see @ref{Frames In Python}, for a more in-depth discussion on
22895 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22896 detailed technical information on @value{GDBN}'s book-keeping of the
22899 The following block-related functions are available in the @code{gdb}
22902 @findex gdb.block_for_pc
22903 @defun block_for_pc pc
22904 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22905 block cannot be found for the @var{pc} value specified, the function
22906 will return @code{None}.
22909 A @code{gdb.Block} object has the following methods:
22912 @defmethod Block is_valid
22913 Returns @code{True} if the @code{gdb.Block} object is valid,
22914 @code{False} if not. A block object can become invalid if the block it
22915 refers to doesn't exist anymore in the inferior. All other
22916 @code{gdb.Block} methods will throw an exception if it is invalid at
22917 the time the method is called. This method is also made available to
22918 the Python iterator object that @code{gdb.Block} provides in an iteration
22919 context and via the Python @code{iter} built-in function.
22923 A @code{gdb.Block} object has the following attributes:
22926 @defivar Block start
22927 The start address of the block. This attribute is not writable.
22931 The end address of the block. This attribute is not writable.
22934 @defivar Block function
22935 The name of the block represented as a @code{gdb.Symbol}. If the
22936 block is not named, then this attribute holds @code{None}. This
22937 attribute is not writable.
22940 @defivar Block superblock
22941 The block containing this block. If this parent block does not exist,
22942 this attribute holds @code{None}. This attribute is not writable.
22946 @node Symbols In Python
22947 @subsubsection Python representation of Symbols.
22949 @cindex symbols in python
22952 @value{GDBN} represents every variable, function and type as an
22953 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22954 Similarly, Python represents these symbols in @value{GDBN} with the
22955 @code{gdb.Symbol} object.
22957 The following symbol-related functions are available in the @code{gdb}
22960 @findex gdb.lookup_symbol
22961 @defun lookup_symbol name @r{[}block@r{]} @r{[}domain@r{]}
22962 This function searches for a symbol by name. The search scope can be
22963 restricted to the parameters defined in the optional domain and block
22966 @var{name} is the name of the symbol. It must be a string. The
22967 optional @var{block} argument restricts the search to symbols visible
22968 in that @var{block}. The @var{block} argument must be a
22969 @code{gdb.Block} object. If omitted, the block for the current frame
22970 is used. The optional @var{domain} argument restricts
22971 the search to the domain type. The @var{domain} argument must be a
22972 domain constant defined in the @code{gdb} module and described later
22975 The result is a tuple of two elements.
22976 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
22978 If the symbol is found, the second element is @code{True} if the symbol
22979 is a field of a method's object (e.g., @code{this} in C@t{++}),
22980 otherwise it is @code{False}.
22981 If the symbol is not found, the second element is @code{False}.
22984 @findex gdb.lookup_global_symbol
22985 @defun lookup_global_symbol name @r{[}domain@r{]}
22986 This function searches for a global symbol by name.
22987 The search scope can be restricted to by the domain argument.
22989 @var{name} is the name of the symbol. It must be a string.
22990 The optional @var{domain} argument restricts the search to the domain type.
22991 The @var{domain} argument must be a domain constant defined in the @code{gdb}
22992 module and described later in this chapter.
22994 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
22998 A @code{gdb.Symbol} object has the following attributes:
23001 @defivar Symbol symtab
23002 The symbol table in which the symbol appears. This attribute is
23003 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23004 Python}. This attribute is not writable.
23007 @defivar Symbol name
23008 The name of the symbol as a string. This attribute is not writable.
23011 @defivar Symbol linkage_name
23012 The name of the symbol, as used by the linker (i.e., may be mangled).
23013 This attribute is not writable.
23016 @defivar Symbol print_name
23017 The name of the symbol in a form suitable for output. This is either
23018 @code{name} or @code{linkage_name}, depending on whether the user
23019 asked @value{GDBN} to display demangled or mangled names.
23022 @defivar Symbol addr_class
23023 The address class of the symbol. This classifies how to find the value
23024 of a symbol. Each address class is a constant defined in the
23025 @code{gdb} module and described later in this chapter.
23028 @defivar Symbol is_argument
23029 @code{True} if the symbol is an argument of a function.
23032 @defivar Symbol is_constant
23033 @code{True} if the symbol is a constant.
23036 @defivar Symbol is_function
23037 @code{True} if the symbol is a function or a method.
23040 @defivar Symbol is_variable
23041 @code{True} if the symbol is a variable.
23045 A @code{gdb.Symbol} object has the following methods:
23048 @defmethod Symbol is_valid
23049 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23050 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23051 the symbol it refers to does not exist in @value{GDBN} any longer.
23052 All other @code{gdb.Symbol} methods will throw an exception if it is
23053 invalid at the time the method is called.
23057 The available domain categories in @code{gdb.Symbol} are represented
23058 as constants in the @code{gdb} module:
23061 @findex SYMBOL_UNDEF_DOMAIN
23062 @findex gdb.SYMBOL_UNDEF_DOMAIN
23063 @item SYMBOL_UNDEF_DOMAIN
23064 This is used when a domain has not been discovered or none of the
23065 following domains apply. This usually indicates an error either
23066 in the symbol information or in @value{GDBN}'s handling of symbols.
23067 @findex SYMBOL_VAR_DOMAIN
23068 @findex gdb.SYMBOL_VAR_DOMAIN
23069 @item SYMBOL_VAR_DOMAIN
23070 This domain contains variables, function names, typedef names and enum
23072 @findex SYMBOL_STRUCT_DOMAIN
23073 @findex gdb.SYMBOL_STRUCT_DOMAIN
23074 @item SYMBOL_STRUCT_DOMAIN
23075 This domain holds struct, union and enum type names.
23076 @findex SYMBOL_LABEL_DOMAIN
23077 @findex gdb.SYMBOL_LABEL_DOMAIN
23078 @item SYMBOL_LABEL_DOMAIN
23079 This domain contains names of labels (for gotos).
23080 @findex SYMBOL_VARIABLES_DOMAIN
23081 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23082 @item SYMBOL_VARIABLES_DOMAIN
23083 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23084 contains everything minus functions and types.
23085 @findex SYMBOL_FUNCTIONS_DOMAIN
23086 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23087 @item SYMBOL_FUNCTION_DOMAIN
23088 This domain contains all functions.
23089 @findex SYMBOL_TYPES_DOMAIN
23090 @findex gdb.SYMBOL_TYPES_DOMAIN
23091 @item SYMBOL_TYPES_DOMAIN
23092 This domain contains all types.
23095 The available address class categories in @code{gdb.Symbol} are represented
23096 as constants in the @code{gdb} module:
23099 @findex SYMBOL_LOC_UNDEF
23100 @findex gdb.SYMBOL_LOC_UNDEF
23101 @item SYMBOL_LOC_UNDEF
23102 If this is returned by address class, it indicates an error either in
23103 the symbol information or in @value{GDBN}'s handling of symbols.
23104 @findex SYMBOL_LOC_CONST
23105 @findex gdb.SYMBOL_LOC_CONST
23106 @item SYMBOL_LOC_CONST
23107 Value is constant int.
23108 @findex SYMBOL_LOC_STATIC
23109 @findex gdb.SYMBOL_LOC_STATIC
23110 @item SYMBOL_LOC_STATIC
23111 Value is at a fixed address.
23112 @findex SYMBOL_LOC_REGISTER
23113 @findex gdb.SYMBOL_LOC_REGISTER
23114 @item SYMBOL_LOC_REGISTER
23115 Value is in a register.
23116 @findex SYMBOL_LOC_ARG
23117 @findex gdb.SYMBOL_LOC_ARG
23118 @item SYMBOL_LOC_ARG
23119 Value is an argument. This value is at the offset stored within the
23120 symbol inside the frame's argument list.
23121 @findex SYMBOL_LOC_REF_ARG
23122 @findex gdb.SYMBOL_LOC_REF_ARG
23123 @item SYMBOL_LOC_REF_ARG
23124 Value address is stored in the frame's argument list. Just like
23125 @code{LOC_ARG} except that the value's address is stored at the
23126 offset, not the value itself.
23127 @findex SYMBOL_LOC_REGPARM_ADDR
23128 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23129 @item SYMBOL_LOC_REGPARM_ADDR
23130 Value is a specified register. Just like @code{LOC_REGISTER} except
23131 the register holds the address of the argument instead of the argument
23133 @findex SYMBOL_LOC_LOCAL
23134 @findex gdb.SYMBOL_LOC_LOCAL
23135 @item SYMBOL_LOC_LOCAL
23136 Value is a local variable.
23137 @findex SYMBOL_LOC_TYPEDEF
23138 @findex gdb.SYMBOL_LOC_TYPEDEF
23139 @item SYMBOL_LOC_TYPEDEF
23140 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23142 @findex SYMBOL_LOC_BLOCK
23143 @findex gdb.SYMBOL_LOC_BLOCK
23144 @item SYMBOL_LOC_BLOCK
23146 @findex SYMBOL_LOC_CONST_BYTES
23147 @findex gdb.SYMBOL_LOC_CONST_BYTES
23148 @item SYMBOL_LOC_CONST_BYTES
23149 Value is a byte-sequence.
23150 @findex SYMBOL_LOC_UNRESOLVED
23151 @findex gdb.SYMBOL_LOC_UNRESOLVED
23152 @item SYMBOL_LOC_UNRESOLVED
23153 Value is at a fixed address, but the address of the variable has to be
23154 determined from the minimal symbol table whenever the variable is
23156 @findex SYMBOL_LOC_OPTIMIZED_OUT
23157 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23158 @item SYMBOL_LOC_OPTIMIZED_OUT
23159 The value does not actually exist in the program.
23160 @findex SYMBOL_LOC_COMPUTED
23161 @findex gdb.SYMBOL_LOC_COMPUTED
23162 @item SYMBOL_LOC_COMPUTED
23163 The value's address is a computed location.
23166 @node Symbol Tables In Python
23167 @subsubsection Symbol table representation in Python.
23169 @cindex symbol tables in python
23171 @tindex gdb.Symtab_and_line
23173 Access to symbol table data maintained by @value{GDBN} on the inferior
23174 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23175 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23176 from the @code{find_sal} method in @code{gdb.Frame} object.
23177 @xref{Frames In Python}.
23179 For more information on @value{GDBN}'s symbol table management, see
23180 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23182 A @code{gdb.Symtab_and_line} object has the following attributes:
23185 @defivar Symtab_and_line symtab
23186 The symbol table object (@code{gdb.Symtab}) for this frame.
23187 This attribute is not writable.
23190 @defivar Symtab_and_line pc
23191 Indicates the current program counter address. This attribute is not
23195 @defivar Symtab_and_line line
23196 Indicates the current line number for this object. This
23197 attribute is not writable.
23201 A @code{gdb.Symtab_and_line} object has the following methods:
23204 @defmethod Symtab_and_line is_valid
23205 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23206 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23207 invalid if the Symbol table and line object it refers to does not
23208 exist in @value{GDBN} any longer. All other
23209 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23210 invalid at the time the method is called.
23214 A @code{gdb.Symtab} object has the following attributes:
23217 @defivar Symtab filename
23218 The symbol table's source filename. This attribute is not writable.
23221 @defivar Symtab objfile
23222 The symbol table's backing object file. @xref{Objfiles In Python}.
23223 This attribute is not writable.
23227 A @code{gdb.Symtab} object has the following methods:
23230 @defmethod Symtab is_valid
23231 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23232 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23233 the symbol table it refers to does not exist in @value{GDBN} any
23234 longer. All other @code{gdb.Symtab} methods will throw an exception
23235 if it is invalid at the time the method is called.
23238 @defmethod Symtab fullname
23239 Return the symbol table's source absolute file name.
23243 @node Breakpoints In Python
23244 @subsubsection Manipulating breakpoints using Python
23246 @cindex breakpoints in python
23247 @tindex gdb.Breakpoint
23249 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23252 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23253 Create a new breakpoint. @var{spec} is a string naming the
23254 location of the breakpoint, or an expression that defines a
23255 watchpoint. The contents can be any location recognized by the
23256 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23257 command. The optional @var{type} denotes the breakpoint to create
23258 from the types defined later in this chapter. This argument can be
23259 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23260 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23261 allows the breakpoint to become invisible to the user. The breakpoint
23262 will neither be reported when created, nor will it be listed in the
23263 output from @code{info breakpoints} (but will be listed with the
23264 @code{maint info breakpoints} command). The optional @var{wp_class}
23265 argument defines the class of watchpoint to create, if @var{type} is
23266 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23267 assumed to be a @var{WP_WRITE} class.
23270 @defop Operation {gdb.Breakpoint} stop (self)
23271 The @code{gdb.Breakpoint} class can be sub-classed and, in
23272 particular, you may choose to implement the @code{stop} method.
23273 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23274 it will be called when the inferior reaches any location of a
23275 breakpoint which instantiates that sub-class. If the method returns
23276 @code{True}, the inferior will be stopped at the location of the
23277 breakpoint, otherwise the inferior will continue.
23279 If there are multiple breakpoints at the same location with a
23280 @code{stop} method, each one will be called regardless of the
23281 return status of the previous. This ensures that all @code{stop}
23282 methods have a chance to execute at that location. In this scenario
23283 if one of the methods returns @code{True} but the others return
23284 @code{False}, the inferior will still be stopped.
23286 Example @code{stop} implementation:
23289 class MyBreakpoint (gdb.Breakpoint):
23291 inf_val = gdb.parse_and_eval("foo")
23298 The available watchpoint types represented by constants are defined in the
23303 @findex gdb.WP_READ
23305 Read only watchpoint.
23308 @findex gdb.WP_WRITE
23310 Write only watchpoint.
23313 @findex gdb.WP_ACCESS
23315 Read/Write watchpoint.
23318 @defmethod Breakpoint is_valid
23319 Return @code{True} if this @code{Breakpoint} object is valid,
23320 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23321 if the user deletes the breakpoint. In this case, the object still
23322 exists, but the underlying breakpoint does not. In the cases of
23323 watchpoint scope, the watchpoint remains valid even if execution of the
23324 inferior leaves the scope of that watchpoint.
23327 @defmethod Breakpoint delete
23328 Permanently deletes the @value{GDBN} breakpoint. This also
23329 invalidates the Python @code{Breakpoint} object. Any further access
23330 to this object's attributes or methods will raise an error.
23333 @defivar Breakpoint enabled
23334 This attribute is @code{True} if the breakpoint is enabled, and
23335 @code{False} otherwise. This attribute is writable.
23338 @defivar Breakpoint silent
23339 This attribute is @code{True} if the breakpoint is silent, and
23340 @code{False} otherwise. This attribute is writable.
23342 Note that a breakpoint can also be silent if it has commands and the
23343 first command is @code{silent}. This is not reported by the
23344 @code{silent} attribute.
23347 @defivar Breakpoint thread
23348 If the breakpoint is thread-specific, this attribute holds the thread
23349 id. If the breakpoint is not thread-specific, this attribute is
23350 @code{None}. This attribute is writable.
23353 @defivar Breakpoint task
23354 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23355 id. If the breakpoint is not task-specific (or the underlying
23356 language is not Ada), this attribute is @code{None}. This attribute
23360 @defivar Breakpoint ignore_count
23361 This attribute holds the ignore count for the breakpoint, an integer.
23362 This attribute is writable.
23365 @defivar Breakpoint number
23366 This attribute holds the breakpoint's number --- the identifier used by
23367 the user to manipulate the breakpoint. This attribute is not writable.
23370 @defivar Breakpoint type
23371 This attribute holds the breakpoint's type --- the identifier used to
23372 determine the actual breakpoint type or use-case. This attribute is not
23376 @defivar Breakpoint visible
23377 This attribute tells whether the breakpoint is visible to the user
23378 when set, or when the @samp{info breakpoints} command is run. This
23379 attribute is not writable.
23382 The available types are represented by constants defined in the @code{gdb}
23386 @findex BP_BREAKPOINT
23387 @findex gdb.BP_BREAKPOINT
23388 @item BP_BREAKPOINT
23389 Normal code breakpoint.
23391 @findex BP_WATCHPOINT
23392 @findex gdb.BP_WATCHPOINT
23393 @item BP_WATCHPOINT
23394 Watchpoint breakpoint.
23396 @findex BP_HARDWARE_WATCHPOINT
23397 @findex gdb.BP_HARDWARE_WATCHPOINT
23398 @item BP_HARDWARE_WATCHPOINT
23399 Hardware assisted watchpoint.
23401 @findex BP_READ_WATCHPOINT
23402 @findex gdb.BP_READ_WATCHPOINT
23403 @item BP_READ_WATCHPOINT
23404 Hardware assisted read watchpoint.
23406 @findex BP_ACCESS_WATCHPOINT
23407 @findex gdb.BP_ACCESS_WATCHPOINT
23408 @item BP_ACCESS_WATCHPOINT
23409 Hardware assisted access watchpoint.
23412 @defivar Breakpoint hit_count
23413 This attribute holds the hit count for the breakpoint, an integer.
23414 This attribute is writable, but currently it can only be set to zero.
23417 @defivar Breakpoint location
23418 This attribute holds the location of the breakpoint, as specified by
23419 the user. It is a string. If the breakpoint does not have a location
23420 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23421 attribute is not writable.
23424 @defivar Breakpoint expression
23425 This attribute holds a breakpoint expression, as specified by
23426 the user. It is a string. If the breakpoint does not have an
23427 expression (the breakpoint is not a watchpoint) the attribute's value
23428 is @code{None}. This attribute is not writable.
23431 @defivar Breakpoint condition
23432 This attribute holds the condition of the breakpoint, as specified by
23433 the user. It is a string. If there is no condition, this attribute's
23434 value is @code{None}. This attribute is writable.
23437 @defivar Breakpoint commands
23438 This attribute holds the commands attached to the breakpoint. If
23439 there are commands, this attribute's value is a string holding all the
23440 commands, separated by newlines. If there are no commands, this
23441 attribute is @code{None}. This attribute is not writable.
23444 @node Lazy Strings In Python
23445 @subsubsection Python representation of lazy strings.
23447 @cindex lazy strings in python
23448 @tindex gdb.LazyString
23450 A @dfn{lazy string} is a string whose contents is not retrieved or
23451 encoded until it is needed.
23453 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23454 @code{address} that points to a region of memory, an @code{encoding}
23455 that will be used to encode that region of memory, and a @code{length}
23456 to delimit the region of memory that represents the string. The
23457 difference between a @code{gdb.LazyString} and a string wrapped within
23458 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23459 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23460 retrieved and encoded during printing, while a @code{gdb.Value}
23461 wrapping a string is immediately retrieved and encoded on creation.
23463 A @code{gdb.LazyString} object has the following functions:
23465 @defmethod LazyString value
23466 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23467 will point to the string in memory, but will lose all the delayed
23468 retrieval, encoding and handling that @value{GDBN} applies to a
23469 @code{gdb.LazyString}.
23472 @defivar LazyString address
23473 This attribute holds the address of the string. This attribute is not
23477 @defivar LazyString length
23478 This attribute holds the length of the string in characters. If the
23479 length is -1, then the string will be fetched and encoded up to the
23480 first null of appropriate width. This attribute is not writable.
23483 @defivar LazyString encoding
23484 This attribute holds the encoding that will be applied to the string
23485 when the string is printed by @value{GDBN}. If the encoding is not
23486 set, or contains an empty string, then @value{GDBN} will select the
23487 most appropriate encoding when the string is printed. This attribute
23491 @defivar LazyString type
23492 This attribute holds the type that is represented by the lazy string's
23493 type. For a lazy string this will always be a pointer type. To
23494 resolve this to the lazy string's character type, use the type's
23495 @code{target} method. @xref{Types In Python}. This attribute is not
23500 @subsection Auto-loading
23501 @cindex auto-loading, Python
23503 When a new object file is read (for example, due to the @code{file}
23504 command, or because the inferior has loaded a shared library),
23505 @value{GDBN} will look for Python support scripts in several ways:
23506 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23509 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23510 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23511 * Which flavor to choose?::
23514 The auto-loading feature is useful for supplying application-specific
23515 debugging commands and scripts.
23517 Auto-loading can be enabled or disabled.
23520 @kindex set auto-load-scripts
23521 @item set auto-load-scripts [yes|no]
23522 Enable or disable the auto-loading of Python scripts.
23524 @kindex show auto-load-scripts
23525 @item show auto-load-scripts
23526 Show whether auto-loading of Python scripts is enabled or disabled.
23529 When reading an auto-loaded file, @value{GDBN} sets the
23530 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23531 function (@pxref{Objfiles In Python}). This can be useful for
23532 registering objfile-specific pretty-printers.
23534 @node objfile-gdb.py file
23535 @subsubsection The @file{@var{objfile}-gdb.py} file
23536 @cindex @file{@var{objfile}-gdb.py}
23538 When a new object file is read, @value{GDBN} looks for
23539 a file named @file{@var{objfile}-gdb.py},
23540 where @var{objfile} is the object file's real name, formed by ensuring
23541 that the file name is absolute, following all symlinks, and resolving
23542 @code{.} and @code{..} components. If this file exists and is
23543 readable, @value{GDBN} will evaluate it as a Python script.
23545 If this file does not exist, and if the parameter
23546 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23547 then @value{GDBN} will look for @var{real-name} in all of the
23548 directories mentioned in the value of @code{debug-file-directory}.
23550 Finally, if this file does not exist, then @value{GDBN} will look for
23551 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23552 @var{data-directory} is @value{GDBN}'s data directory (available via
23553 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23554 is the object file's real name, as described above.
23556 @value{GDBN} does not track which files it has already auto-loaded this way.
23557 @value{GDBN} will load the associated script every time the corresponding
23558 @var{objfile} is opened.
23559 So your @file{-gdb.py} file should be careful to avoid errors if it
23560 is evaluated more than once.
23562 @node .debug_gdb_scripts section
23563 @subsubsection The @code{.debug_gdb_scripts} section
23564 @cindex @code{.debug_gdb_scripts} section
23566 For systems using file formats like ELF and COFF,
23567 when @value{GDBN} loads a new object file
23568 it will look for a special section named @samp{.debug_gdb_scripts}.
23569 If this section exists, its contents is a list of names of scripts to load.
23571 @value{GDBN} will look for each specified script file first in the
23572 current directory and then along the source search path
23573 (@pxref{Source Path, ,Specifying Source Directories}),
23574 except that @file{$cdir} is not searched, since the compilation
23575 directory is not relevant to scripts.
23577 Entries can be placed in section @code{.debug_gdb_scripts} with,
23578 for example, this GCC macro:
23581 /* Note: The "MS" section flags are to remove duplicates. */
23582 #define DEFINE_GDB_SCRIPT(script_name) \
23584 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23586 .asciz \"" script_name "\"\n\
23592 Then one can reference the macro in a header or source file like this:
23595 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23598 The script name may include directories if desired.
23600 If the macro is put in a header, any application or library
23601 using this header will get a reference to the specified script.
23603 @node Which flavor to choose?
23604 @subsubsection Which flavor to choose?
23606 Given the multiple ways of auto-loading Python scripts, it might not always
23607 be clear which one to choose. This section provides some guidance.
23609 Benefits of the @file{-gdb.py} way:
23613 Can be used with file formats that don't support multiple sections.
23616 Ease of finding scripts for public libraries.
23618 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23619 in the source search path.
23620 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23621 isn't a source directory in which to find the script.
23624 Doesn't require source code additions.
23627 Benefits of the @code{.debug_gdb_scripts} way:
23631 Works with static linking.
23633 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23634 trigger their loading. When an application is statically linked the only
23635 objfile available is the executable, and it is cumbersome to attach all the
23636 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23639 Works with classes that are entirely inlined.
23641 Some classes can be entirely inlined, and thus there may not be an associated
23642 shared library to attach a @file{-gdb.py} script to.
23645 Scripts needn't be copied out of the source tree.
23647 In some circumstances, apps can be built out of large collections of internal
23648 libraries, and the build infrastructure necessary to install the
23649 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23650 cumbersome. It may be easier to specify the scripts in the
23651 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23652 top of the source tree to the source search path.
23655 @node Python modules
23656 @subsection Python modules
23657 @cindex python modules
23659 @value{GDBN} comes with a module to assist writing Python code.
23662 * gdb.printing:: Building and registering pretty-printers.
23663 * gdb.types:: Utilities for working with types.
23667 @subsubsection gdb.printing
23668 @cindex gdb.printing
23670 This module provides a collection of utilities for working with
23674 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23675 This class specifies the API that makes @samp{info pretty-printer},
23676 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23677 Pretty-printers should generally inherit from this class.
23679 @item SubPrettyPrinter (@var{name})
23680 For printers that handle multiple types, this class specifies the
23681 corresponding API for the subprinters.
23683 @item RegexpCollectionPrettyPrinter (@var{name})
23684 Utility class for handling multiple printers, all recognized via
23685 regular expressions.
23686 @xref{Writing a Pretty-Printer}, for an example.
23688 @item register_pretty_printer (@var{obj}, @var{printer})
23689 Register @var{printer} with the pretty-printer list of @var{obj}.
23693 @subsubsection gdb.types
23696 This module provides a collection of utilities for working with
23697 @code{gdb.Types} objects.
23700 @item get_basic_type (@var{type})
23701 Return @var{type} with const and volatile qualifiers stripped,
23702 and with typedefs and C@t{++} references converted to the underlying type.
23707 typedef const int const_int;
23709 const_int& foo_ref (foo);
23710 int main () @{ return 0; @}
23717 (gdb) python import gdb.types
23718 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23719 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23723 @item has_field (@var{type}, @var{field})
23724 Return @code{True} if @var{type}, assumed to be a type with fields
23725 (e.g., a structure or union), has field @var{field}.
23727 @item make_enum_dict (@var{enum_type})
23728 Return a Python @code{dictionary} type produced from @var{enum_type}.
23732 @chapter Command Interpreters
23733 @cindex command interpreters
23735 @value{GDBN} supports multiple command interpreters, and some command
23736 infrastructure to allow users or user interface writers to switch
23737 between interpreters or run commands in other interpreters.
23739 @value{GDBN} currently supports two command interpreters, the console
23740 interpreter (sometimes called the command-line interpreter or @sc{cli})
23741 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23742 describes both of these interfaces in great detail.
23744 By default, @value{GDBN} will start with the console interpreter.
23745 However, the user may choose to start @value{GDBN} with another
23746 interpreter by specifying the @option{-i} or @option{--interpreter}
23747 startup options. Defined interpreters include:
23751 @cindex console interpreter
23752 The traditional console or command-line interpreter. This is the most often
23753 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23754 @value{GDBN} will use this interpreter.
23757 @cindex mi interpreter
23758 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23759 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23760 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23764 @cindex mi2 interpreter
23765 The current @sc{gdb/mi} interface.
23768 @cindex mi1 interpreter
23769 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23773 @cindex invoke another interpreter
23774 The interpreter being used by @value{GDBN} may not be dynamically
23775 switched at runtime. Although possible, this could lead to a very
23776 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23777 enters the command "interpreter-set console" in a console view,
23778 @value{GDBN} would switch to using the console interpreter, rendering
23779 the IDE inoperable!
23781 @kindex interpreter-exec
23782 Although you may only choose a single interpreter at startup, you may execute
23783 commands in any interpreter from the current interpreter using the appropriate
23784 command. If you are running the console interpreter, simply use the
23785 @code{interpreter-exec} command:
23788 interpreter-exec mi "-data-list-register-names"
23791 @sc{gdb/mi} has a similar command, although it is only available in versions of
23792 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23795 @chapter @value{GDBN} Text User Interface
23797 @cindex Text User Interface
23800 * TUI Overview:: TUI overview
23801 * TUI Keys:: TUI key bindings
23802 * TUI Single Key Mode:: TUI single key mode
23803 * TUI Commands:: TUI-specific commands
23804 * TUI Configuration:: TUI configuration variables
23807 The @value{GDBN} Text User Interface (TUI) is a terminal
23808 interface which uses the @code{curses} library to show the source
23809 file, the assembly output, the program registers and @value{GDBN}
23810 commands in separate text windows. The TUI mode is supported only
23811 on platforms where a suitable version of the @code{curses} library
23814 @pindex @value{GDBTUI}
23815 The TUI mode is enabled by default when you invoke @value{GDBN} as
23816 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23817 You can also switch in and out of TUI mode while @value{GDBN} runs by
23818 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23819 @xref{TUI Keys, ,TUI Key Bindings}.
23822 @section TUI Overview
23824 In TUI mode, @value{GDBN} can display several text windows:
23828 This window is the @value{GDBN} command window with the @value{GDBN}
23829 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23830 managed using readline.
23833 The source window shows the source file of the program. The current
23834 line and active breakpoints are displayed in this window.
23837 The assembly window shows the disassembly output of the program.
23840 This window shows the processor registers. Registers are highlighted
23841 when their values change.
23844 The source and assembly windows show the current program position
23845 by highlighting the current line and marking it with a @samp{>} marker.
23846 Breakpoints are indicated with two markers. The first marker
23847 indicates the breakpoint type:
23851 Breakpoint which was hit at least once.
23854 Breakpoint which was never hit.
23857 Hardware breakpoint which was hit at least once.
23860 Hardware breakpoint which was never hit.
23863 The second marker indicates whether the breakpoint is enabled or not:
23867 Breakpoint is enabled.
23870 Breakpoint is disabled.
23873 The source, assembly and register windows are updated when the current
23874 thread changes, when the frame changes, or when the program counter
23877 These windows are not all visible at the same time. The command
23878 window is always visible. The others can be arranged in several
23889 source and assembly,
23892 source and registers, or
23895 assembly and registers.
23898 A status line above the command window shows the following information:
23902 Indicates the current @value{GDBN} target.
23903 (@pxref{Targets, ,Specifying a Debugging Target}).
23906 Gives the current process or thread number.
23907 When no process is being debugged, this field is set to @code{No process}.
23910 Gives the current function name for the selected frame.
23911 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23912 When there is no symbol corresponding to the current program counter,
23913 the string @code{??} is displayed.
23916 Indicates the current line number for the selected frame.
23917 When the current line number is not known, the string @code{??} is displayed.
23920 Indicates the current program counter address.
23924 @section TUI Key Bindings
23925 @cindex TUI key bindings
23927 The TUI installs several key bindings in the readline keymaps
23928 @ifset SYSTEM_READLINE
23929 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23931 @ifclear SYSTEM_READLINE
23932 (@pxref{Command Line Editing}).
23934 The following key bindings are installed for both TUI mode and the
23935 @value{GDBN} standard mode.
23944 Enter or leave the TUI mode. When leaving the TUI mode,
23945 the curses window management stops and @value{GDBN} operates using
23946 its standard mode, writing on the terminal directly. When reentering
23947 the TUI mode, control is given back to the curses windows.
23948 The screen is then refreshed.
23952 Use a TUI layout with only one window. The layout will
23953 either be @samp{source} or @samp{assembly}. When the TUI mode
23954 is not active, it will switch to the TUI mode.
23956 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23960 Use a TUI layout with at least two windows. When the current
23961 layout already has two windows, the next layout with two windows is used.
23962 When a new layout is chosen, one window will always be common to the
23963 previous layout and the new one.
23965 Think of it as the Emacs @kbd{C-x 2} binding.
23969 Change the active window. The TUI associates several key bindings
23970 (like scrolling and arrow keys) with the active window. This command
23971 gives the focus to the next TUI window.
23973 Think of it as the Emacs @kbd{C-x o} binding.
23977 Switch in and out of the TUI SingleKey mode that binds single
23978 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23981 The following key bindings only work in the TUI mode:
23986 Scroll the active window one page up.
23990 Scroll the active window one page down.
23994 Scroll the active window one line up.
23998 Scroll the active window one line down.
24002 Scroll the active window one column left.
24006 Scroll the active window one column right.
24010 Refresh the screen.
24013 Because the arrow keys scroll the active window in the TUI mode, they
24014 are not available for their normal use by readline unless the command
24015 window has the focus. When another window is active, you must use
24016 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24017 and @kbd{C-f} to control the command window.
24019 @node TUI Single Key Mode
24020 @section TUI Single Key Mode
24021 @cindex TUI single key mode
24023 The TUI also provides a @dfn{SingleKey} mode, which binds several
24024 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24025 switch into this mode, where the following key bindings are used:
24028 @kindex c @r{(SingleKey TUI key)}
24032 @kindex d @r{(SingleKey TUI key)}
24036 @kindex f @r{(SingleKey TUI key)}
24040 @kindex n @r{(SingleKey TUI key)}
24044 @kindex q @r{(SingleKey TUI key)}
24046 exit the SingleKey mode.
24048 @kindex r @r{(SingleKey TUI key)}
24052 @kindex s @r{(SingleKey TUI key)}
24056 @kindex u @r{(SingleKey TUI key)}
24060 @kindex v @r{(SingleKey TUI key)}
24064 @kindex w @r{(SingleKey TUI key)}
24069 Other keys temporarily switch to the @value{GDBN} command prompt.
24070 The key that was pressed is inserted in the editing buffer so that
24071 it is possible to type most @value{GDBN} commands without interaction
24072 with the TUI SingleKey mode. Once the command is entered the TUI
24073 SingleKey mode is restored. The only way to permanently leave
24074 this mode is by typing @kbd{q} or @kbd{C-x s}.
24078 @section TUI-specific Commands
24079 @cindex TUI commands
24081 The TUI has specific commands to control the text windows.
24082 These commands are always available, even when @value{GDBN} is not in
24083 the TUI mode. When @value{GDBN} is in the standard mode, most
24084 of these commands will automatically switch to the TUI mode.
24086 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24087 terminal, or @value{GDBN} has been started with the machine interface
24088 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24089 these commands will fail with an error, because it would not be
24090 possible or desirable to enable curses window management.
24095 List and give the size of all displayed windows.
24099 Display the next layout.
24102 Display the previous layout.
24105 Display the source window only.
24108 Display the assembly window only.
24111 Display the source and assembly window.
24114 Display the register window together with the source or assembly window.
24118 Make the next window active for scrolling.
24121 Make the previous window active for scrolling.
24124 Make the source window active for scrolling.
24127 Make the assembly window active for scrolling.
24130 Make the register window active for scrolling.
24133 Make the command window active for scrolling.
24137 Refresh the screen. This is similar to typing @kbd{C-L}.
24139 @item tui reg float
24141 Show the floating point registers in the register window.
24143 @item tui reg general
24144 Show the general registers in the register window.
24147 Show the next register group. The list of register groups as well as
24148 their order is target specific. The predefined register groups are the
24149 following: @code{general}, @code{float}, @code{system}, @code{vector},
24150 @code{all}, @code{save}, @code{restore}.
24152 @item tui reg system
24153 Show the system registers in the register window.
24157 Update the source window and the current execution point.
24159 @item winheight @var{name} +@var{count}
24160 @itemx winheight @var{name} -@var{count}
24162 Change the height of the window @var{name} by @var{count}
24163 lines. Positive counts increase the height, while negative counts
24166 @item tabset @var{nchars}
24168 Set the width of tab stops to be @var{nchars} characters.
24171 @node TUI Configuration
24172 @section TUI Configuration Variables
24173 @cindex TUI configuration variables
24175 Several configuration variables control the appearance of TUI windows.
24178 @item set tui border-kind @var{kind}
24179 @kindex set tui border-kind
24180 Select the border appearance for the source, assembly and register windows.
24181 The possible values are the following:
24184 Use a space character to draw the border.
24187 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24190 Use the Alternate Character Set to draw the border. The border is
24191 drawn using character line graphics if the terminal supports them.
24194 @item set tui border-mode @var{mode}
24195 @kindex set tui border-mode
24196 @itemx set tui active-border-mode @var{mode}
24197 @kindex set tui active-border-mode
24198 Select the display attributes for the borders of the inactive windows
24199 or the active window. The @var{mode} can be one of the following:
24202 Use normal attributes to display the border.
24208 Use reverse video mode.
24211 Use half bright mode.
24213 @item half-standout
24214 Use half bright and standout mode.
24217 Use extra bright or bold mode.
24219 @item bold-standout
24220 Use extra bright or bold and standout mode.
24225 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24228 @cindex @sc{gnu} Emacs
24229 A special interface allows you to use @sc{gnu} Emacs to view (and
24230 edit) the source files for the program you are debugging with
24233 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24234 executable file you want to debug as an argument. This command starts
24235 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24236 created Emacs buffer.
24237 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24239 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24244 All ``terminal'' input and output goes through an Emacs buffer, called
24247 This applies both to @value{GDBN} commands and their output, and to the input
24248 and output done by the program you are debugging.
24250 This is useful because it means that you can copy the text of previous
24251 commands and input them again; you can even use parts of the output
24254 All the facilities of Emacs' Shell mode are available for interacting
24255 with your program. In particular, you can send signals the usual
24256 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24260 @value{GDBN} displays source code through Emacs.
24262 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24263 source file for that frame and puts an arrow (@samp{=>}) at the
24264 left margin of the current line. Emacs uses a separate buffer for
24265 source display, and splits the screen to show both your @value{GDBN} session
24268 Explicit @value{GDBN} @code{list} or search commands still produce output as
24269 usual, but you probably have no reason to use them from Emacs.
24272 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24273 a graphical mode, enabled by default, which provides further buffers
24274 that can control the execution and describe the state of your program.
24275 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24277 If you specify an absolute file name when prompted for the @kbd{M-x
24278 gdb} argument, then Emacs sets your current working directory to where
24279 your program resides. If you only specify the file name, then Emacs
24280 sets your current working directory to the directory associated
24281 with the previous buffer. In this case, @value{GDBN} may find your
24282 program by searching your environment's @code{PATH} variable, but on
24283 some operating systems it might not find the source. So, although the
24284 @value{GDBN} input and output session proceeds normally, the auxiliary
24285 buffer does not display the current source and line of execution.
24287 The initial working directory of @value{GDBN} is printed on the top
24288 line of the GUD buffer and this serves as a default for the commands
24289 that specify files for @value{GDBN} to operate on. @xref{Files,
24290 ,Commands to Specify Files}.
24292 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24293 need to call @value{GDBN} by a different name (for example, if you
24294 keep several configurations around, with different names) you can
24295 customize the Emacs variable @code{gud-gdb-command-name} to run the
24298 In the GUD buffer, you can use these special Emacs commands in
24299 addition to the standard Shell mode commands:
24303 Describe the features of Emacs' GUD Mode.
24306 Execute to another source line, like the @value{GDBN} @code{step} command; also
24307 update the display window to show the current file and location.
24310 Execute to next source line in this function, skipping all function
24311 calls, like the @value{GDBN} @code{next} command. Then update the display window
24312 to show the current file and location.
24315 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24316 display window accordingly.
24319 Execute until exit from the selected stack frame, like the @value{GDBN}
24320 @code{finish} command.
24323 Continue execution of your program, like the @value{GDBN} @code{continue}
24327 Go up the number of frames indicated by the numeric argument
24328 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24329 like the @value{GDBN} @code{up} command.
24332 Go down the number of frames indicated by the numeric argument, like the
24333 @value{GDBN} @code{down} command.
24336 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24337 tells @value{GDBN} to set a breakpoint on the source line point is on.
24339 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24340 separate frame which shows a backtrace when the GUD buffer is current.
24341 Move point to any frame in the stack and type @key{RET} to make it
24342 become the current frame and display the associated source in the
24343 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24344 selected frame become the current one. In graphical mode, the
24345 speedbar displays watch expressions.
24347 If you accidentally delete the source-display buffer, an easy way to get
24348 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24349 request a frame display; when you run under Emacs, this recreates
24350 the source buffer if necessary to show you the context of the current
24353 The source files displayed in Emacs are in ordinary Emacs buffers
24354 which are visiting the source files in the usual way. You can edit
24355 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24356 communicates with Emacs in terms of line numbers. If you add or
24357 delete lines from the text, the line numbers that @value{GDBN} knows cease
24358 to correspond properly with the code.
24360 A more detailed description of Emacs' interaction with @value{GDBN} is
24361 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24364 @c The following dropped because Epoch is nonstandard. Reactivate
24365 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24367 @kindex Emacs Epoch environment
24371 Version 18 of @sc{gnu} Emacs has a built-in window system
24372 called the @code{epoch}
24373 environment. Users of this environment can use a new command,
24374 @code{inspect} which performs identically to @code{print} except that
24375 each value is printed in its own window.
24380 @chapter The @sc{gdb/mi} Interface
24382 @unnumberedsec Function and Purpose
24384 @cindex @sc{gdb/mi}, its purpose
24385 @sc{gdb/mi} is a line based machine oriented text interface to
24386 @value{GDBN} and is activated by specifying using the
24387 @option{--interpreter} command line option (@pxref{Mode Options}). It
24388 is specifically intended to support the development of systems which
24389 use the debugger as just one small component of a larger system.
24391 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24392 in the form of a reference manual.
24394 Note that @sc{gdb/mi} is still under construction, so some of the
24395 features described below are incomplete and subject to change
24396 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24398 @unnumberedsec Notation and Terminology
24400 @cindex notational conventions, for @sc{gdb/mi}
24401 This chapter uses the following notation:
24405 @code{|} separates two alternatives.
24408 @code{[ @var{something} ]} indicates that @var{something} is optional:
24409 it may or may not be given.
24412 @code{( @var{group} )*} means that @var{group} inside the parentheses
24413 may repeat zero or more times.
24416 @code{( @var{group} )+} means that @var{group} inside the parentheses
24417 may repeat one or more times.
24420 @code{"@var{string}"} means a literal @var{string}.
24424 @heading Dependencies
24428 * GDB/MI General Design::
24429 * GDB/MI Command Syntax::
24430 * GDB/MI Compatibility with CLI::
24431 * GDB/MI Development and Front Ends::
24432 * GDB/MI Output Records::
24433 * GDB/MI Simple Examples::
24434 * GDB/MI Command Description Format::
24435 * GDB/MI Breakpoint Commands::
24436 * GDB/MI Program Context::
24437 * GDB/MI Thread Commands::
24438 * GDB/MI Program Execution::
24439 * GDB/MI Stack Manipulation::
24440 * GDB/MI Variable Objects::
24441 * GDB/MI Data Manipulation::
24442 * GDB/MI Tracepoint Commands::
24443 * GDB/MI Symbol Query::
24444 * GDB/MI File Commands::
24446 * GDB/MI Kod Commands::
24447 * GDB/MI Memory Overlay Commands::
24448 * GDB/MI Signal Handling Commands::
24450 * GDB/MI Target Manipulation::
24451 * GDB/MI File Transfer Commands::
24452 * GDB/MI Miscellaneous Commands::
24455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24456 @node GDB/MI General Design
24457 @section @sc{gdb/mi} General Design
24458 @cindex GDB/MI General Design
24460 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24461 parts---commands sent to @value{GDBN}, responses to those commands
24462 and notifications. Each command results in exactly one response,
24463 indicating either successful completion of the command, or an error.
24464 For the commands that do not resume the target, the response contains the
24465 requested information. For the commands that resume the target, the
24466 response only indicates whether the target was successfully resumed.
24467 Notifications is the mechanism for reporting changes in the state of the
24468 target, or in @value{GDBN} state, that cannot conveniently be associated with
24469 a command and reported as part of that command response.
24471 The important examples of notifications are:
24475 Exec notifications. These are used to report changes in
24476 target state---when a target is resumed, or stopped. It would not
24477 be feasible to include this information in response of resuming
24478 commands, because one resume commands can result in multiple events in
24479 different threads. Also, quite some time may pass before any event
24480 happens in the target, while a frontend needs to know whether the resuming
24481 command itself was successfully executed.
24484 Console output, and status notifications. Console output
24485 notifications are used to report output of CLI commands, as well as
24486 diagnostics for other commands. Status notifications are used to
24487 report the progress of a long-running operation. Naturally, including
24488 this information in command response would mean no output is produced
24489 until the command is finished, which is undesirable.
24492 General notifications. Commands may have various side effects on
24493 the @value{GDBN} or target state beyond their official purpose. For example,
24494 a command may change the selected thread. Although such changes can
24495 be included in command response, using notification allows for more
24496 orthogonal frontend design.
24500 There's no guarantee that whenever an MI command reports an error,
24501 @value{GDBN} or the target are in any specific state, and especially,
24502 the state is not reverted to the state before the MI command was
24503 processed. Therefore, whenever an MI command results in an error,
24504 we recommend that the frontend refreshes all the information shown in
24505 the user interface.
24509 * Context management::
24510 * Asynchronous and non-stop modes::
24514 @node Context management
24515 @subsection Context management
24517 In most cases when @value{GDBN} accesses the target, this access is
24518 done in context of a specific thread and frame (@pxref{Frames}).
24519 Often, even when accessing global data, the target requires that a thread
24520 be specified. The CLI interface maintains the selected thread and frame,
24521 and supplies them to target on each command. This is convenient,
24522 because a command line user would not want to specify that information
24523 explicitly on each command, and because user interacts with
24524 @value{GDBN} via a single terminal, so no confusion is possible as
24525 to what thread and frame are the current ones.
24527 In the case of MI, the concept of selected thread and frame is less
24528 useful. First, a frontend can easily remember this information
24529 itself. Second, a graphical frontend can have more than one window,
24530 each one used for debugging a different thread, and the frontend might
24531 want to access additional threads for internal purposes. This
24532 increases the risk that by relying on implicitly selected thread, the
24533 frontend may be operating on a wrong one. Therefore, each MI command
24534 should explicitly specify which thread and frame to operate on. To
24535 make it possible, each MI command accepts the @samp{--thread} and
24536 @samp{--frame} options, the value to each is @value{GDBN} identifier
24537 for thread and frame to operate on.
24539 Usually, each top-level window in a frontend allows the user to select
24540 a thread and a frame, and remembers the user selection for further
24541 operations. However, in some cases @value{GDBN} may suggest that the
24542 current thread be changed. For example, when stopping on a breakpoint
24543 it is reasonable to switch to the thread where breakpoint is hit. For
24544 another example, if the user issues the CLI @samp{thread} command via
24545 the frontend, it is desirable to change the frontend's selected thread to the
24546 one specified by user. @value{GDBN} communicates the suggestion to
24547 change current thread using the @samp{=thread-selected} notification.
24548 No such notification is available for the selected frame at the moment.
24550 Note that historically, MI shares the selected thread with CLI, so
24551 frontends used the @code{-thread-select} to execute commands in the
24552 right context. However, getting this to work right is cumbersome. The
24553 simplest way is for frontend to emit @code{-thread-select} command
24554 before every command. This doubles the number of commands that need
24555 to be sent. The alternative approach is to suppress @code{-thread-select}
24556 if the selected thread in @value{GDBN} is supposed to be identical to the
24557 thread the frontend wants to operate on. However, getting this
24558 optimization right can be tricky. In particular, if the frontend
24559 sends several commands to @value{GDBN}, and one of the commands changes the
24560 selected thread, then the behaviour of subsequent commands will
24561 change. So, a frontend should either wait for response from such
24562 problematic commands, or explicitly add @code{-thread-select} for
24563 all subsequent commands. No frontend is known to do this exactly
24564 right, so it is suggested to just always pass the @samp{--thread} and
24565 @samp{--frame} options.
24567 @node Asynchronous and non-stop modes
24568 @subsection Asynchronous command execution and non-stop mode
24570 On some targets, @value{GDBN} is capable of processing MI commands
24571 even while the target is running. This is called @dfn{asynchronous
24572 command execution} (@pxref{Background Execution}). The frontend may
24573 specify a preferrence for asynchronous execution using the
24574 @code{-gdb-set target-async 1} command, which should be emitted before
24575 either running the executable or attaching to the target. After the
24576 frontend has started the executable or attached to the target, it can
24577 find if asynchronous execution is enabled using the
24578 @code{-list-target-features} command.
24580 Even if @value{GDBN} can accept a command while target is running,
24581 many commands that access the target do not work when the target is
24582 running. Therefore, asynchronous command execution is most useful
24583 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24584 it is possible to examine the state of one thread, while other threads
24587 When a given thread is running, MI commands that try to access the
24588 target in the context of that thread may not work, or may work only on
24589 some targets. In particular, commands that try to operate on thread's
24590 stack will not work, on any target. Commands that read memory, or
24591 modify breakpoints, may work or not work, depending on the target. Note
24592 that even commands that operate on global state, such as @code{print},
24593 @code{set}, and breakpoint commands, still access the target in the
24594 context of a specific thread, so frontend should try to find a
24595 stopped thread and perform the operation on that thread (using the
24596 @samp{--thread} option).
24598 Which commands will work in the context of a running thread is
24599 highly target dependent. However, the two commands
24600 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24601 to find the state of a thread, will always work.
24603 @node Thread groups
24604 @subsection Thread groups
24605 @value{GDBN} may be used to debug several processes at the same time.
24606 On some platfroms, @value{GDBN} may support debugging of several
24607 hardware systems, each one having several cores with several different
24608 processes running on each core. This section describes the MI
24609 mechanism to support such debugging scenarios.
24611 The key observation is that regardless of the structure of the
24612 target, MI can have a global list of threads, because most commands that
24613 accept the @samp{--thread} option do not need to know what process that
24614 thread belongs to. Therefore, it is not necessary to introduce
24615 neither additional @samp{--process} option, nor an notion of the
24616 current process in the MI interface. The only strictly new feature
24617 that is required is the ability to find how the threads are grouped
24620 To allow the user to discover such grouping, and to support arbitrary
24621 hierarchy of machines/cores/processes, MI introduces the concept of a
24622 @dfn{thread group}. Thread group is a collection of threads and other
24623 thread groups. A thread group always has a string identifier, a type,
24624 and may have additional attributes specific to the type. A new
24625 command, @code{-list-thread-groups}, returns the list of top-level
24626 thread groups, which correspond to processes that @value{GDBN} is
24627 debugging at the moment. By passing an identifier of a thread group
24628 to the @code{-list-thread-groups} command, it is possible to obtain
24629 the members of specific thread group.
24631 To allow the user to easily discover processes, and other objects, he
24632 wishes to debug, a concept of @dfn{available thread group} is
24633 introduced. Available thread group is an thread group that
24634 @value{GDBN} is not debugging, but that can be attached to, using the
24635 @code{-target-attach} command. The list of available top-level thread
24636 groups can be obtained using @samp{-list-thread-groups --available}.
24637 In general, the content of a thread group may be only retrieved only
24638 after attaching to that thread group.
24640 Thread groups are related to inferiors (@pxref{Inferiors and
24641 Programs}). Each inferior corresponds to a thread group of a special
24642 type @samp{process}, and some additional operations are permitted on
24643 such thread groups.
24645 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24646 @node GDB/MI Command Syntax
24647 @section @sc{gdb/mi} Command Syntax
24650 * GDB/MI Input Syntax::
24651 * GDB/MI Output Syntax::
24654 @node GDB/MI Input Syntax
24655 @subsection @sc{gdb/mi} Input Syntax
24657 @cindex input syntax for @sc{gdb/mi}
24658 @cindex @sc{gdb/mi}, input syntax
24660 @item @var{command} @expansion{}
24661 @code{@var{cli-command} | @var{mi-command}}
24663 @item @var{cli-command} @expansion{}
24664 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24665 @var{cli-command} is any existing @value{GDBN} CLI command.
24667 @item @var{mi-command} @expansion{}
24668 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24669 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24671 @item @var{token} @expansion{}
24672 "any sequence of digits"
24674 @item @var{option} @expansion{}
24675 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24677 @item @var{parameter} @expansion{}
24678 @code{@var{non-blank-sequence} | @var{c-string}}
24680 @item @var{operation} @expansion{}
24681 @emph{any of the operations described in this chapter}
24683 @item @var{non-blank-sequence} @expansion{}
24684 @emph{anything, provided it doesn't contain special characters such as
24685 "-", @var{nl}, """ and of course " "}
24687 @item @var{c-string} @expansion{}
24688 @code{""" @var{seven-bit-iso-c-string-content} """}
24690 @item @var{nl} @expansion{}
24699 The CLI commands are still handled by the @sc{mi} interpreter; their
24700 output is described below.
24703 The @code{@var{token}}, when present, is passed back when the command
24707 Some @sc{mi} commands accept optional arguments as part of the parameter
24708 list. Each option is identified by a leading @samp{-} (dash) and may be
24709 followed by an optional argument parameter. Options occur first in the
24710 parameter list and can be delimited from normal parameters using
24711 @samp{--} (this is useful when some parameters begin with a dash).
24718 We want easy access to the existing CLI syntax (for debugging).
24721 We want it to be easy to spot a @sc{mi} operation.
24724 @node GDB/MI Output Syntax
24725 @subsection @sc{gdb/mi} Output Syntax
24727 @cindex output syntax of @sc{gdb/mi}
24728 @cindex @sc{gdb/mi}, output syntax
24729 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24730 followed, optionally, by a single result record. This result record
24731 is for the most recent command. The sequence of output records is
24732 terminated by @samp{(gdb)}.
24734 If an input command was prefixed with a @code{@var{token}} then the
24735 corresponding output for that command will also be prefixed by that same
24739 @item @var{output} @expansion{}
24740 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24742 @item @var{result-record} @expansion{}
24743 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24745 @item @var{out-of-band-record} @expansion{}
24746 @code{@var{async-record} | @var{stream-record}}
24748 @item @var{async-record} @expansion{}
24749 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24751 @item @var{exec-async-output} @expansion{}
24752 @code{[ @var{token} ] "*" @var{async-output}}
24754 @item @var{status-async-output} @expansion{}
24755 @code{[ @var{token} ] "+" @var{async-output}}
24757 @item @var{notify-async-output} @expansion{}
24758 @code{[ @var{token} ] "=" @var{async-output}}
24760 @item @var{async-output} @expansion{}
24761 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24763 @item @var{result-class} @expansion{}
24764 @code{"done" | "running" | "connected" | "error" | "exit"}
24766 @item @var{async-class} @expansion{}
24767 @code{"stopped" | @var{others}} (where @var{others} will be added
24768 depending on the needs---this is still in development).
24770 @item @var{result} @expansion{}
24771 @code{ @var{variable} "=" @var{value}}
24773 @item @var{variable} @expansion{}
24774 @code{ @var{string} }
24776 @item @var{value} @expansion{}
24777 @code{ @var{const} | @var{tuple} | @var{list} }
24779 @item @var{const} @expansion{}
24780 @code{@var{c-string}}
24782 @item @var{tuple} @expansion{}
24783 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24785 @item @var{list} @expansion{}
24786 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24787 @var{result} ( "," @var{result} )* "]" }
24789 @item @var{stream-record} @expansion{}
24790 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24792 @item @var{console-stream-output} @expansion{}
24793 @code{"~" @var{c-string}}
24795 @item @var{target-stream-output} @expansion{}
24796 @code{"@@" @var{c-string}}
24798 @item @var{log-stream-output} @expansion{}
24799 @code{"&" @var{c-string}}
24801 @item @var{nl} @expansion{}
24804 @item @var{token} @expansion{}
24805 @emph{any sequence of digits}.
24813 All output sequences end in a single line containing a period.
24816 The @code{@var{token}} is from the corresponding request. Note that
24817 for all async output, while the token is allowed by the grammar and
24818 may be output by future versions of @value{GDBN} for select async
24819 output messages, it is generally omitted. Frontends should treat
24820 all async output as reporting general changes in the state of the
24821 target and there should be no need to associate async output to any
24825 @cindex status output in @sc{gdb/mi}
24826 @var{status-async-output} contains on-going status information about the
24827 progress of a slow operation. It can be discarded. All status output is
24828 prefixed by @samp{+}.
24831 @cindex async output in @sc{gdb/mi}
24832 @var{exec-async-output} contains asynchronous state change on the target
24833 (stopped, started, disappeared). All async output is prefixed by
24837 @cindex notify output in @sc{gdb/mi}
24838 @var{notify-async-output} contains supplementary information that the
24839 client should handle (e.g., a new breakpoint information). All notify
24840 output is prefixed by @samp{=}.
24843 @cindex console output in @sc{gdb/mi}
24844 @var{console-stream-output} is output that should be displayed as is in the
24845 console. It is the textual response to a CLI command. All the console
24846 output is prefixed by @samp{~}.
24849 @cindex target output in @sc{gdb/mi}
24850 @var{target-stream-output} is the output produced by the target program.
24851 All the target output is prefixed by @samp{@@}.
24854 @cindex log output in @sc{gdb/mi}
24855 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24856 instance messages that should be displayed as part of an error log. All
24857 the log output is prefixed by @samp{&}.
24860 @cindex list output in @sc{gdb/mi}
24861 New @sc{gdb/mi} commands should only output @var{lists} containing
24867 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24868 details about the various output records.
24870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24871 @node GDB/MI Compatibility with CLI
24872 @section @sc{gdb/mi} Compatibility with CLI
24874 @cindex compatibility, @sc{gdb/mi} and CLI
24875 @cindex @sc{gdb/mi}, compatibility with CLI
24877 For the developers convenience CLI commands can be entered directly,
24878 but there may be some unexpected behaviour. For example, commands
24879 that query the user will behave as if the user replied yes, breakpoint
24880 command lists are not executed and some CLI commands, such as
24881 @code{if}, @code{when} and @code{define}, prompt for further input with
24882 @samp{>}, which is not valid MI output.
24884 This feature may be removed at some stage in the future and it is
24885 recommended that front ends use the @code{-interpreter-exec} command
24886 (@pxref{-interpreter-exec}).
24888 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24889 @node GDB/MI Development and Front Ends
24890 @section @sc{gdb/mi} Development and Front Ends
24891 @cindex @sc{gdb/mi} development
24893 The application which takes the MI output and presents the state of the
24894 program being debugged to the user is called a @dfn{front end}.
24896 Although @sc{gdb/mi} is still incomplete, it is currently being used
24897 by a variety of front ends to @value{GDBN}. This makes it difficult
24898 to introduce new functionality without breaking existing usage. This
24899 section tries to minimize the problems by describing how the protocol
24902 Some changes in MI need not break a carefully designed front end, and
24903 for these the MI version will remain unchanged. The following is a
24904 list of changes that may occur within one level, so front ends should
24905 parse MI output in a way that can handle them:
24909 New MI commands may be added.
24912 New fields may be added to the output of any MI command.
24915 The range of values for fields with specified values, e.g.,
24916 @code{in_scope} (@pxref{-var-update}) may be extended.
24918 @c The format of field's content e.g type prefix, may change so parse it
24919 @c at your own risk. Yes, in general?
24921 @c The order of fields may change? Shouldn't really matter but it might
24922 @c resolve inconsistencies.
24925 If the changes are likely to break front ends, the MI version level
24926 will be increased by one. This will allow the front end to parse the
24927 output according to the MI version. Apart from mi0, new versions of
24928 @value{GDBN} will not support old versions of MI and it will be the
24929 responsibility of the front end to work with the new one.
24931 @c Starting with mi3, add a new command -mi-version that prints the MI
24934 The best way to avoid unexpected changes in MI that might break your front
24935 end is to make your project known to @value{GDBN} developers and
24936 follow development on @email{gdb@@sourceware.org} and
24937 @email{gdb-patches@@sourceware.org}.
24938 @cindex mailing lists
24940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24941 @node GDB/MI Output Records
24942 @section @sc{gdb/mi} Output Records
24945 * GDB/MI Result Records::
24946 * GDB/MI Stream Records::
24947 * GDB/MI Async Records::
24948 * GDB/MI Frame Information::
24949 * GDB/MI Thread Information::
24950 * GDB/MI Ada Exception Information::
24953 @node GDB/MI Result Records
24954 @subsection @sc{gdb/mi} Result Records
24956 @cindex result records in @sc{gdb/mi}
24957 @cindex @sc{gdb/mi}, result records
24958 In addition to a number of out-of-band notifications, the response to a
24959 @sc{gdb/mi} command includes one of the following result indications:
24963 @item "^done" [ "," @var{results} ]
24964 The synchronous operation was successful, @code{@var{results}} are the return
24969 This result record is equivalent to @samp{^done}. Historically, it
24970 was output instead of @samp{^done} if the command has resumed the
24971 target. This behaviour is maintained for backward compatibility, but
24972 all frontends should treat @samp{^done} and @samp{^running}
24973 identically and rely on the @samp{*running} output record to determine
24974 which threads are resumed.
24978 @value{GDBN} has connected to a remote target.
24980 @item "^error" "," @var{c-string}
24982 The operation failed. The @code{@var{c-string}} contains the corresponding
24987 @value{GDBN} has terminated.
24991 @node GDB/MI Stream Records
24992 @subsection @sc{gdb/mi} Stream Records
24994 @cindex @sc{gdb/mi}, stream records
24995 @cindex stream records in @sc{gdb/mi}
24996 @value{GDBN} internally maintains a number of output streams: the console, the
24997 target, and the log. The output intended for each of these streams is
24998 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25000 Each stream record begins with a unique @dfn{prefix character} which
25001 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25002 Syntax}). In addition to the prefix, each stream record contains a
25003 @code{@var{string-output}}. This is either raw text (with an implicit new
25004 line) or a quoted C string (which does not contain an implicit newline).
25007 @item "~" @var{string-output}
25008 The console output stream contains text that should be displayed in the
25009 CLI console window. It contains the textual responses to CLI commands.
25011 @item "@@" @var{string-output}
25012 The target output stream contains any textual output from the running
25013 target. This is only present when GDB's event loop is truly
25014 asynchronous, which is currently only the case for remote targets.
25016 @item "&" @var{string-output}
25017 The log stream contains debugging messages being produced by @value{GDBN}'s
25021 @node GDB/MI Async Records
25022 @subsection @sc{gdb/mi} Async Records
25024 @cindex async records in @sc{gdb/mi}
25025 @cindex @sc{gdb/mi}, async records
25026 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25027 additional changes that have occurred. Those changes can either be a
25028 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25029 target activity (e.g., target stopped).
25031 The following is the list of possible async records:
25035 @item *running,thread-id="@var{thread}"
25036 The target is now running. The @var{thread} field tells which
25037 specific thread is now running, and can be @samp{all} if all threads
25038 are running. The frontend should assume that no interaction with a
25039 running thread is possible after this notification is produced.
25040 The frontend should not assume that this notification is output
25041 only once for any command. @value{GDBN} may emit this notification
25042 several times, either for different threads, because it cannot resume
25043 all threads together, or even for a single thread, if the thread must
25044 be stepped though some code before letting it run freely.
25046 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25047 The target has stopped. The @var{reason} field can have one of the
25051 @item breakpoint-hit
25052 A breakpoint was reached.
25053 @item watchpoint-trigger
25054 A watchpoint was triggered.
25055 @item read-watchpoint-trigger
25056 A read watchpoint was triggered.
25057 @item access-watchpoint-trigger
25058 An access watchpoint was triggered.
25059 @item function-finished
25060 An -exec-finish or similar CLI command was accomplished.
25061 @item location-reached
25062 An -exec-until or similar CLI command was accomplished.
25063 @item watchpoint-scope
25064 A watchpoint has gone out of scope.
25065 @item end-stepping-range
25066 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25067 similar CLI command was accomplished.
25068 @item exited-signalled
25069 The inferior exited because of a signal.
25071 The inferior exited.
25072 @item exited-normally
25073 The inferior exited normally.
25074 @item signal-received
25075 A signal was received by the inferior.
25078 The @var{id} field identifies the thread that directly caused the stop
25079 -- for example by hitting a breakpoint. Depending on whether all-stop
25080 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25081 stop all threads, or only the thread that directly triggered the stop.
25082 If all threads are stopped, the @var{stopped} field will have the
25083 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25084 field will be a list of thread identifiers. Presently, this list will
25085 always include a single thread, but frontend should be prepared to see
25086 several threads in the list. The @var{core} field reports the
25087 processor core on which the stop event has happened. This field may be absent
25088 if such information is not available.
25090 @item =thread-group-added,id="@var{id}"
25091 @itemx =thread-group-removed,id="@var{id}"
25092 A thread group was either added or removed. The @var{id} field
25093 contains the @value{GDBN} identifier of the thread group. When a thread
25094 group is added, it generally might not be associated with a running
25095 process. When a thread group is removed, its id becomes invalid and
25096 cannot be used in any way.
25098 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25099 A thread group became associated with a running program,
25100 either because the program was just started or the thread group
25101 was attached to a program. The @var{id} field contains the
25102 @value{GDBN} identifier of the thread group. The @var{pid} field
25103 contains process identifier, specific to the operating system.
25105 @itemx =thread-group-exited,id="@var{id}"
25106 A thread group is no longer associated with a running program,
25107 either because the program has exited, or because it was detached
25108 from. The @var{id} field contains the @value{GDBN} identifier of the
25111 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25112 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25113 A thread either was created, or has exited. The @var{id} field
25114 contains the @value{GDBN} identifier of the thread. The @var{gid}
25115 field identifies the thread group this thread belongs to.
25117 @item =thread-selected,id="@var{id}"
25118 Informs that the selected thread was changed as result of the last
25119 command. This notification is not emitted as result of @code{-thread-select}
25120 command but is emitted whenever an MI command that is not documented
25121 to change the selected thread actually changes it. In particular,
25122 invoking, directly or indirectly (via user-defined command), the CLI
25123 @code{thread} command, will generate this notification.
25125 We suggest that in response to this notification, front ends
25126 highlight the selected thread and cause subsequent commands to apply to
25129 @item =library-loaded,...
25130 Reports that a new library file was loaded by the program. This
25131 notification has 4 fields---@var{id}, @var{target-name},
25132 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25133 opaque identifier of the library. For remote debugging case,
25134 @var{target-name} and @var{host-name} fields give the name of the
25135 library file on the target, and on the host respectively. For native
25136 debugging, both those fields have the same value. The
25137 @var{symbols-loaded} field is emitted only for backward compatibility
25138 and should not be relied on to convey any useful information. The
25139 @var{thread-group} field, if present, specifies the id of the thread
25140 group in whose context the library was loaded. If the field is
25141 absent, it means the library was loaded in the context of all present
25144 @item =library-unloaded,...
25145 Reports that a library was unloaded by the program. This notification
25146 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25147 the same meaning as for the @code{=library-loaded} notification.
25148 The @var{thread-group} field, if present, specifies the id of the
25149 thread group in whose context the library was unloaded. If the field is
25150 absent, it means the library was unloaded in the context of all present
25155 @node GDB/MI Frame Information
25156 @subsection @sc{gdb/mi} Frame Information
25158 Response from many MI commands includes an information about stack
25159 frame. This information is a tuple that may have the following
25164 The level of the stack frame. The innermost frame has the level of
25165 zero. This field is always present.
25168 The name of the function corresponding to the frame. This field may
25169 be absent if @value{GDBN} is unable to determine the function name.
25172 The code address for the frame. This field is always present.
25175 The name of the source files that correspond to the frame's code
25176 address. This field may be absent.
25179 The source line corresponding to the frames' code address. This field
25183 The name of the binary file (either executable or shared library) the
25184 corresponds to the frame's code address. This field may be absent.
25188 @node GDB/MI Thread Information
25189 @subsection @sc{gdb/mi} Thread Information
25191 Whenever @value{GDBN} has to report an information about a thread, it
25192 uses a tuple with the following fields:
25196 The numeric id assigned to the thread by @value{GDBN}. This field is
25200 Target-specific string identifying the thread. This field is always present.
25203 Additional information about the thread provided by the target.
25204 It is supposed to be human-readable and not interpreted by the
25205 frontend. This field is optional.
25208 Either @samp{stopped} or @samp{running}, depending on whether the
25209 thread is presently running. This field is always present.
25212 The value of this field is an integer number of the processor core the
25213 thread was last seen on. This field is optional.
25216 @node GDB/MI Ada Exception Information
25217 @subsection @sc{gdb/mi} Ada Exception Information
25219 Whenever a @code{*stopped} record is emitted because the program
25220 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25221 @value{GDBN} provides the name of the exception that was raised via
25222 the @code{exception-name} field.
25224 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25225 @node GDB/MI Simple Examples
25226 @section Simple Examples of @sc{gdb/mi} Interaction
25227 @cindex @sc{gdb/mi}, simple examples
25229 This subsection presents several simple examples of interaction using
25230 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25231 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25232 the output received from @sc{gdb/mi}.
25234 Note the line breaks shown in the examples are here only for
25235 readability, they don't appear in the real output.
25237 @subheading Setting a Breakpoint
25239 Setting a breakpoint generates synchronous output which contains detailed
25240 information of the breakpoint.
25243 -> -break-insert main
25244 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25245 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25246 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25250 @subheading Program Execution
25252 Program execution generates asynchronous records and MI gives the
25253 reason that execution stopped.
25259 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25260 frame=@{addr="0x08048564",func="main",
25261 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25262 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25267 <- *stopped,reason="exited-normally"
25271 @subheading Quitting @value{GDBN}
25273 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25281 Please note that @samp{^exit} is printed immediately, but it might
25282 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25283 performs necessary cleanups, including killing programs being debugged
25284 or disconnecting from debug hardware, so the frontend should wait till
25285 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25286 fails to exit in reasonable time.
25288 @subheading A Bad Command
25290 Here's what happens if you pass a non-existent command:
25294 <- ^error,msg="Undefined MI command: rubbish"
25299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25300 @node GDB/MI Command Description Format
25301 @section @sc{gdb/mi} Command Description Format
25303 The remaining sections describe blocks of commands. Each block of
25304 commands is laid out in a fashion similar to this section.
25306 @subheading Motivation
25308 The motivation for this collection of commands.
25310 @subheading Introduction
25312 A brief introduction to this collection of commands as a whole.
25314 @subheading Commands
25316 For each command in the block, the following is described:
25318 @subsubheading Synopsis
25321 -command @var{args}@dots{}
25324 @subsubheading Result
25326 @subsubheading @value{GDBN} Command
25328 The corresponding @value{GDBN} CLI command(s), if any.
25330 @subsubheading Example
25332 Example(s) formatted for readability. Some of the described commands have
25333 not been implemented yet and these are labeled N.A.@: (not available).
25336 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25337 @node GDB/MI Breakpoint Commands
25338 @section @sc{gdb/mi} Breakpoint Commands
25340 @cindex breakpoint commands for @sc{gdb/mi}
25341 @cindex @sc{gdb/mi}, breakpoint commands
25342 This section documents @sc{gdb/mi} commands for manipulating
25345 @subheading The @code{-break-after} Command
25346 @findex -break-after
25348 @subsubheading Synopsis
25351 -break-after @var{number} @var{count}
25354 The breakpoint number @var{number} is not in effect until it has been
25355 hit @var{count} times. To see how this is reflected in the output of
25356 the @samp{-break-list} command, see the description of the
25357 @samp{-break-list} command below.
25359 @subsubheading @value{GDBN} Command
25361 The corresponding @value{GDBN} command is @samp{ignore}.
25363 @subsubheading Example
25368 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25369 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25370 fullname="/home/foo/hello.c",line="5",times="0"@}
25377 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25378 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25379 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25380 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25381 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25382 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25383 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25384 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25385 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25386 line="5",times="0",ignore="3"@}]@}
25391 @subheading The @code{-break-catch} Command
25392 @findex -break-catch
25395 @subheading The @code{-break-commands} Command
25396 @findex -break-commands
25398 @subsubheading Synopsis
25401 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25404 Specifies the CLI commands that should be executed when breakpoint
25405 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25406 are the commands. If no command is specified, any previously-set
25407 commands are cleared. @xref{Break Commands}. Typical use of this
25408 functionality is tracing a program, that is, printing of values of
25409 some variables whenever breakpoint is hit and then continuing.
25411 @subsubheading @value{GDBN} Command
25413 The corresponding @value{GDBN} command is @samp{commands}.
25415 @subsubheading Example
25420 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25421 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25422 fullname="/home/foo/hello.c",line="5",times="0"@}
25424 -break-commands 1 "print v" "continue"
25429 @subheading The @code{-break-condition} Command
25430 @findex -break-condition
25432 @subsubheading Synopsis
25435 -break-condition @var{number} @var{expr}
25438 Breakpoint @var{number} will stop the program only if the condition in
25439 @var{expr} is true. The condition becomes part of the
25440 @samp{-break-list} output (see the description of the @samp{-break-list}
25443 @subsubheading @value{GDBN} Command
25445 The corresponding @value{GDBN} command is @samp{condition}.
25447 @subsubheading Example
25451 -break-condition 1 1
25455 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25456 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25457 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25458 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25459 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25460 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25461 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25462 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25463 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25464 line="5",cond="1",times="0",ignore="3"@}]@}
25468 @subheading The @code{-break-delete} Command
25469 @findex -break-delete
25471 @subsubheading Synopsis
25474 -break-delete ( @var{breakpoint} )+
25477 Delete the breakpoint(s) whose number(s) are specified in the argument
25478 list. This is obviously reflected in the breakpoint list.
25480 @subsubheading @value{GDBN} Command
25482 The corresponding @value{GDBN} command is @samp{delete}.
25484 @subsubheading Example
25492 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25493 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25494 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25495 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25496 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25497 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25498 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25503 @subheading The @code{-break-disable} Command
25504 @findex -break-disable
25506 @subsubheading Synopsis
25509 -break-disable ( @var{breakpoint} )+
25512 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25513 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25515 @subsubheading @value{GDBN} Command
25517 The corresponding @value{GDBN} command is @samp{disable}.
25519 @subsubheading Example
25527 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25528 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25529 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25530 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25531 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25532 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25533 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25534 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25535 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25536 line="5",times="0"@}]@}
25540 @subheading The @code{-break-enable} Command
25541 @findex -break-enable
25543 @subsubheading Synopsis
25546 -break-enable ( @var{breakpoint} )+
25549 Enable (previously disabled) @var{breakpoint}(s).
25551 @subsubheading @value{GDBN} Command
25553 The corresponding @value{GDBN} command is @samp{enable}.
25555 @subsubheading Example
25563 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25564 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25565 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25566 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25567 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25568 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25569 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25570 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25571 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25572 line="5",times="0"@}]@}
25576 @subheading The @code{-break-info} Command
25577 @findex -break-info
25579 @subsubheading Synopsis
25582 -break-info @var{breakpoint}
25586 Get information about a single breakpoint.
25588 @subsubheading @value{GDBN} Command
25590 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25592 @subsubheading Example
25595 @subheading The @code{-break-insert} Command
25596 @findex -break-insert
25598 @subsubheading Synopsis
25601 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25602 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25603 [ -p @var{thread} ] [ @var{location} ]
25607 If specified, @var{location}, can be one of:
25614 @item filename:linenum
25615 @item filename:function
25619 The possible optional parameters of this command are:
25623 Insert a temporary breakpoint.
25625 Insert a hardware breakpoint.
25626 @item -c @var{condition}
25627 Make the breakpoint conditional on @var{condition}.
25628 @item -i @var{ignore-count}
25629 Initialize the @var{ignore-count}.
25631 If @var{location} cannot be parsed (for example if it
25632 refers to unknown files or functions), create a pending
25633 breakpoint. Without this flag, @value{GDBN} will report
25634 an error, and won't create a breakpoint, if @var{location}
25637 Create a disabled breakpoint.
25639 Create a tracepoint. @xref{Tracepoints}. When this parameter
25640 is used together with @samp{-h}, a fast tracepoint is created.
25643 @subsubheading Result
25645 The result is in the form:
25648 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25649 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25650 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25651 times="@var{times}"@}
25655 where @var{number} is the @value{GDBN} number for this breakpoint,
25656 @var{funcname} is the name of the function where the breakpoint was
25657 inserted, @var{filename} is the name of the source file which contains
25658 this function, @var{lineno} is the source line number within that file
25659 and @var{times} the number of times that the breakpoint has been hit
25660 (always 0 for -break-insert but may be greater for -break-info or -break-list
25661 which use the same output).
25663 Note: this format is open to change.
25664 @c An out-of-band breakpoint instead of part of the result?
25666 @subsubheading @value{GDBN} Command
25668 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25669 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25671 @subsubheading Example
25676 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25677 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25679 -break-insert -t foo
25680 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25681 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25684 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25685 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25686 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25687 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25688 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25689 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25690 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25691 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25692 addr="0x0001072c", func="main",file="recursive2.c",
25693 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25694 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25695 addr="0x00010774",func="foo",file="recursive2.c",
25696 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25698 -break-insert -r foo.*
25699 ~int foo(int, int);
25700 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25701 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25705 @subheading The @code{-break-list} Command
25706 @findex -break-list
25708 @subsubheading Synopsis
25714 Displays the list of inserted breakpoints, showing the following fields:
25718 number of the breakpoint
25720 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25722 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25725 is the breakpoint enabled or no: @samp{y} or @samp{n}
25727 memory location at which the breakpoint is set
25729 logical location of the breakpoint, expressed by function name, file
25732 number of times the breakpoint has been hit
25735 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25736 @code{body} field is an empty list.
25738 @subsubheading @value{GDBN} Command
25740 The corresponding @value{GDBN} command is @samp{info break}.
25742 @subsubheading Example
25747 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25748 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25749 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25750 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25751 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25752 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25753 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25754 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25755 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25756 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25757 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25758 line="13",times="0"@}]@}
25762 Here's an example of the result when there are no breakpoints:
25767 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25768 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25769 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25770 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25771 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25772 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25773 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25778 @subheading The @code{-break-passcount} Command
25779 @findex -break-passcount
25781 @subsubheading Synopsis
25784 -break-passcount @var{tracepoint-number} @var{passcount}
25787 Set the passcount for tracepoint @var{tracepoint-number} to
25788 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25789 is not a tracepoint, error is emitted. This corresponds to CLI
25790 command @samp{passcount}.
25792 @subheading The @code{-break-watch} Command
25793 @findex -break-watch
25795 @subsubheading Synopsis
25798 -break-watch [ -a | -r ]
25801 Create a watchpoint. With the @samp{-a} option it will create an
25802 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25803 read from or on a write to the memory location. With the @samp{-r}
25804 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25805 trigger only when the memory location is accessed for reading. Without
25806 either of the options, the watchpoint created is a regular watchpoint,
25807 i.e., it will trigger when the memory location is accessed for writing.
25808 @xref{Set Watchpoints, , Setting Watchpoints}.
25810 Note that @samp{-break-list} will report a single list of watchpoints and
25811 breakpoints inserted.
25813 @subsubheading @value{GDBN} Command
25815 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25818 @subsubheading Example
25820 Setting a watchpoint on a variable in the @code{main} function:
25825 ^done,wpt=@{number="2",exp="x"@}
25830 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25831 value=@{old="-268439212",new="55"@},
25832 frame=@{func="main",args=[],file="recursive2.c",
25833 fullname="/home/foo/bar/recursive2.c",line="5"@}
25837 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25838 the program execution twice: first for the variable changing value, then
25839 for the watchpoint going out of scope.
25844 ^done,wpt=@{number="5",exp="C"@}
25849 *stopped,reason="watchpoint-trigger",
25850 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25851 frame=@{func="callee4",args=[],
25852 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25853 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25858 *stopped,reason="watchpoint-scope",wpnum="5",
25859 frame=@{func="callee3",args=[@{name="strarg",
25860 value="0x11940 \"A string argument.\""@}],
25861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25866 Listing breakpoints and watchpoints, at different points in the program
25867 execution. Note that once the watchpoint goes out of scope, it is
25873 ^done,wpt=@{number="2",exp="C"@}
25876 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25877 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25878 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25879 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25880 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25881 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25882 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25883 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25884 addr="0x00010734",func="callee4",
25885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25886 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25887 bkpt=@{number="2",type="watchpoint",disp="keep",
25888 enabled="y",addr="",what="C",times="0"@}]@}
25893 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25894 value=@{old="-276895068",new="3"@},
25895 frame=@{func="callee4",args=[],
25896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25897 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25900 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25901 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25902 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25903 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25904 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25905 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25906 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25907 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25908 addr="0x00010734",func="callee4",
25909 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25910 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25911 bkpt=@{number="2",type="watchpoint",disp="keep",
25912 enabled="y",addr="",what="C",times="-5"@}]@}
25916 ^done,reason="watchpoint-scope",wpnum="2",
25917 frame=@{func="callee3",args=[@{name="strarg",
25918 value="0x11940 \"A string argument.\""@}],
25919 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25920 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25923 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25924 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25925 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25926 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25927 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25928 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25929 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25930 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25931 addr="0x00010734",func="callee4",
25932 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25933 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25938 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25939 @node GDB/MI Program Context
25940 @section @sc{gdb/mi} Program Context
25942 @subheading The @code{-exec-arguments} Command
25943 @findex -exec-arguments
25946 @subsubheading Synopsis
25949 -exec-arguments @var{args}
25952 Set the inferior program arguments, to be used in the next
25955 @subsubheading @value{GDBN} Command
25957 The corresponding @value{GDBN} command is @samp{set args}.
25959 @subsubheading Example
25963 -exec-arguments -v word
25970 @subheading The @code{-exec-show-arguments} Command
25971 @findex -exec-show-arguments
25973 @subsubheading Synopsis
25976 -exec-show-arguments
25979 Print the arguments of the program.
25981 @subsubheading @value{GDBN} Command
25983 The corresponding @value{GDBN} command is @samp{show args}.
25985 @subsubheading Example
25990 @subheading The @code{-environment-cd} Command
25991 @findex -environment-cd
25993 @subsubheading Synopsis
25996 -environment-cd @var{pathdir}
25999 Set @value{GDBN}'s working directory.
26001 @subsubheading @value{GDBN} Command
26003 The corresponding @value{GDBN} command is @samp{cd}.
26005 @subsubheading Example
26009 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26015 @subheading The @code{-environment-directory} Command
26016 @findex -environment-directory
26018 @subsubheading Synopsis
26021 -environment-directory [ -r ] [ @var{pathdir} ]+
26024 Add directories @var{pathdir} to beginning of search path for source files.
26025 If the @samp{-r} option is used, the search path is reset to the default
26026 search path. If directories @var{pathdir} are supplied in addition to the
26027 @samp{-r} option, the search path is first reset and then addition
26029 Multiple directories may be specified, separated by blanks. Specifying
26030 multiple directories in a single command
26031 results in the directories added to the beginning of the
26032 search path in the same order they were presented in the command.
26033 If blanks are needed as
26034 part of a directory name, double-quotes should be used around
26035 the name. In the command output, the path will show up separated
26036 by the system directory-separator character. The directory-separator
26037 character must not be used
26038 in any directory name.
26039 If no directories are specified, the current search path is displayed.
26041 @subsubheading @value{GDBN} Command
26043 The corresponding @value{GDBN} command is @samp{dir}.
26045 @subsubheading Example
26049 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26050 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26052 -environment-directory ""
26053 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26055 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26056 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26058 -environment-directory -r
26059 ^done,source-path="$cdir:$cwd"
26064 @subheading The @code{-environment-path} Command
26065 @findex -environment-path
26067 @subsubheading Synopsis
26070 -environment-path [ -r ] [ @var{pathdir} ]+
26073 Add directories @var{pathdir} to beginning of search path for object files.
26074 If the @samp{-r} option is used, the search path is reset to the original
26075 search path that existed at gdb start-up. If directories @var{pathdir} are
26076 supplied in addition to the
26077 @samp{-r} option, the search path is first reset and then addition
26079 Multiple directories may be specified, separated by blanks. Specifying
26080 multiple directories in a single command
26081 results in the directories added to the beginning of the
26082 search path in the same order they were presented in the command.
26083 If blanks are needed as
26084 part of a directory name, double-quotes should be used around
26085 the name. In the command output, the path will show up separated
26086 by the system directory-separator character. The directory-separator
26087 character must not be used
26088 in any directory name.
26089 If no directories are specified, the current path is displayed.
26092 @subsubheading @value{GDBN} Command
26094 The corresponding @value{GDBN} command is @samp{path}.
26096 @subsubheading Example
26101 ^done,path="/usr/bin"
26103 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26104 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26106 -environment-path -r /usr/local/bin
26107 ^done,path="/usr/local/bin:/usr/bin"
26112 @subheading The @code{-environment-pwd} Command
26113 @findex -environment-pwd
26115 @subsubheading Synopsis
26121 Show the current working directory.
26123 @subsubheading @value{GDBN} Command
26125 The corresponding @value{GDBN} command is @samp{pwd}.
26127 @subsubheading Example
26132 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26137 @node GDB/MI Thread Commands
26138 @section @sc{gdb/mi} Thread Commands
26141 @subheading The @code{-thread-info} Command
26142 @findex -thread-info
26144 @subsubheading Synopsis
26147 -thread-info [ @var{thread-id} ]
26150 Reports information about either a specific thread, if
26151 the @var{thread-id} parameter is present, or about all
26152 threads. When printing information about all threads,
26153 also reports the current thread.
26155 @subsubheading @value{GDBN} Command
26157 The @samp{info thread} command prints the same information
26160 @subsubheading Result
26162 The result is a list of threads. The following attributes are
26163 defined for a given thread:
26167 This field exists only for the current thread. It has the value @samp{*}.
26170 The identifier that @value{GDBN} uses to refer to the thread.
26173 The identifier that the target uses to refer to the thread.
26176 Extra information about the thread, in a target-specific format. This
26180 The name of the thread. If the user specified a name using the
26181 @code{thread name} command, then this name is given. Otherwise, if
26182 @value{GDBN} can extract the thread name from the target, then that
26183 name is given. If @value{GDBN} cannot find the thread name, then this
26187 The stack frame currently executing in the thread.
26190 The thread's state. The @samp{state} field may have the following
26195 The thread is stopped. Frame information is available for stopped
26199 The thread is running. There's no frame information for running
26205 If @value{GDBN} can find the CPU core on which this thread is running,
26206 then this field is the core identifier. This field is optional.
26210 @subsubheading Example
26215 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26216 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26217 args=[]@},state="running"@},
26218 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26219 frame=@{level="0",addr="0x0804891f",func="foo",
26220 args=[@{name="i",value="10"@}],
26221 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26222 state="running"@}],
26223 current-thread-id="1"
26227 @subheading The @code{-thread-list-ids} Command
26228 @findex -thread-list-ids
26230 @subsubheading Synopsis
26236 Produces a list of the currently known @value{GDBN} thread ids. At the
26237 end of the list it also prints the total number of such threads.
26239 This command is retained for historical reasons, the
26240 @code{-thread-info} command should be used instead.
26242 @subsubheading @value{GDBN} Command
26244 Part of @samp{info threads} supplies the same information.
26246 @subsubheading Example
26251 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26252 current-thread-id="1",number-of-threads="3"
26257 @subheading The @code{-thread-select} Command
26258 @findex -thread-select
26260 @subsubheading Synopsis
26263 -thread-select @var{threadnum}
26266 Make @var{threadnum} the current thread. It prints the number of the new
26267 current thread, and the topmost frame for that thread.
26269 This command is deprecated in favor of explicitly using the
26270 @samp{--thread} option to each command.
26272 @subsubheading @value{GDBN} Command
26274 The corresponding @value{GDBN} command is @samp{thread}.
26276 @subsubheading Example
26283 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26284 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26288 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26289 number-of-threads="3"
26292 ^done,new-thread-id="3",
26293 frame=@{level="0",func="vprintf",
26294 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26295 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26300 @node GDB/MI Program Execution
26301 @section @sc{gdb/mi} Program Execution
26303 These are the asynchronous commands which generate the out-of-band
26304 record @samp{*stopped}. Currently @value{GDBN} only really executes
26305 asynchronously with remote targets and this interaction is mimicked in
26308 @subheading The @code{-exec-continue} Command
26309 @findex -exec-continue
26311 @subsubheading Synopsis
26314 -exec-continue [--reverse] [--all|--thread-group N]
26317 Resumes the execution of the inferior program, which will continue
26318 to execute until it reaches a debugger stop event. If the
26319 @samp{--reverse} option is specified, execution resumes in reverse until
26320 it reaches a stop event. Stop events may include
26323 breakpoints or watchpoints
26325 signals or exceptions
26327 the end of the process (or its beginning under @samp{--reverse})
26329 the end or beginning of a replay log if one is being used.
26331 In all-stop mode (@pxref{All-Stop
26332 Mode}), may resume only one thread, or all threads, depending on the
26333 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26334 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26335 ignored in all-stop mode. If the @samp{--thread-group} options is
26336 specified, then all threads in that thread group are resumed.
26338 @subsubheading @value{GDBN} Command
26340 The corresponding @value{GDBN} corresponding is @samp{continue}.
26342 @subsubheading Example
26349 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26350 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26356 @subheading The @code{-exec-finish} Command
26357 @findex -exec-finish
26359 @subsubheading Synopsis
26362 -exec-finish [--reverse]
26365 Resumes the execution of the inferior program until the current
26366 function is exited. Displays the results returned by the function.
26367 If the @samp{--reverse} option is specified, resumes the reverse
26368 execution of the inferior program until the point where current
26369 function was called.
26371 @subsubheading @value{GDBN} Command
26373 The corresponding @value{GDBN} command is @samp{finish}.
26375 @subsubheading Example
26377 Function returning @code{void}.
26384 *stopped,reason="function-finished",frame=@{func="main",args=[],
26385 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26389 Function returning other than @code{void}. The name of the internal
26390 @value{GDBN} variable storing the result is printed, together with the
26397 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26398 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26399 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26400 gdb-result-var="$1",return-value="0"
26405 @subheading The @code{-exec-interrupt} Command
26406 @findex -exec-interrupt
26408 @subsubheading Synopsis
26411 -exec-interrupt [--all|--thread-group N]
26414 Interrupts the background execution of the target. Note how the token
26415 associated with the stop message is the one for the execution command
26416 that has been interrupted. The token for the interrupt itself only
26417 appears in the @samp{^done} output. If the user is trying to
26418 interrupt a non-running program, an error message will be printed.
26420 Note that when asynchronous execution is enabled, this command is
26421 asynchronous just like other execution commands. That is, first the
26422 @samp{^done} response will be printed, and the target stop will be
26423 reported after that using the @samp{*stopped} notification.
26425 In non-stop mode, only the context thread is interrupted by default.
26426 All threads (in all inferiors) will be interrupted if the
26427 @samp{--all} option is specified. If the @samp{--thread-group}
26428 option is specified, all threads in that group will be interrupted.
26430 @subsubheading @value{GDBN} Command
26432 The corresponding @value{GDBN} command is @samp{interrupt}.
26434 @subsubheading Example
26445 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26446 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26447 fullname="/home/foo/bar/try.c",line="13"@}
26452 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26456 @subheading The @code{-exec-jump} Command
26459 @subsubheading Synopsis
26462 -exec-jump @var{location}
26465 Resumes execution of the inferior program at the location specified by
26466 parameter. @xref{Specify Location}, for a description of the
26467 different forms of @var{location}.
26469 @subsubheading @value{GDBN} Command
26471 The corresponding @value{GDBN} command is @samp{jump}.
26473 @subsubheading Example
26476 -exec-jump foo.c:10
26477 *running,thread-id="all"
26482 @subheading The @code{-exec-next} Command
26485 @subsubheading Synopsis
26488 -exec-next [--reverse]
26491 Resumes execution of the inferior program, stopping when the beginning
26492 of the next source line is reached.
26494 If the @samp{--reverse} option is specified, resumes reverse execution
26495 of the inferior program, stopping at the beginning of the previous
26496 source line. If you issue this command on the first line of a
26497 function, it will take you back to the caller of that function, to the
26498 source line where the function was called.
26501 @subsubheading @value{GDBN} Command
26503 The corresponding @value{GDBN} command is @samp{next}.
26505 @subsubheading Example
26511 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26516 @subheading The @code{-exec-next-instruction} Command
26517 @findex -exec-next-instruction
26519 @subsubheading Synopsis
26522 -exec-next-instruction [--reverse]
26525 Executes one machine instruction. If the instruction is a function
26526 call, continues until the function returns. If the program stops at an
26527 instruction in the middle of a source line, the address will be
26530 If the @samp{--reverse} option is specified, resumes reverse execution
26531 of the inferior program, stopping at the previous instruction. If the
26532 previously executed instruction was a return from another function,
26533 it will continue to execute in reverse until the call to that function
26534 (from the current stack frame) is reached.
26536 @subsubheading @value{GDBN} Command
26538 The corresponding @value{GDBN} command is @samp{nexti}.
26540 @subsubheading Example
26544 -exec-next-instruction
26548 *stopped,reason="end-stepping-range",
26549 addr="0x000100d4",line="5",file="hello.c"
26554 @subheading The @code{-exec-return} Command
26555 @findex -exec-return
26557 @subsubheading Synopsis
26563 Makes current function return immediately. Doesn't execute the inferior.
26564 Displays the new current frame.
26566 @subsubheading @value{GDBN} Command
26568 The corresponding @value{GDBN} command is @samp{return}.
26570 @subsubheading Example
26574 200-break-insert callee4
26575 200^done,bkpt=@{number="1",addr="0x00010734",
26576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26581 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26582 frame=@{func="callee4",args=[],
26583 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26584 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26590 111^done,frame=@{level="0",func="callee3",
26591 args=[@{name="strarg",
26592 value="0x11940 \"A string argument.\""@}],
26593 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26594 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26599 @subheading The @code{-exec-run} Command
26602 @subsubheading Synopsis
26605 -exec-run [--all | --thread-group N]
26608 Starts execution of the inferior from the beginning. The inferior
26609 executes until either a breakpoint is encountered or the program
26610 exits. In the latter case the output will include an exit code, if
26611 the program has exited exceptionally.
26613 When no option is specified, the current inferior is started. If the
26614 @samp{--thread-group} option is specified, it should refer to a thread
26615 group of type @samp{process}, and that thread group will be started.
26616 If the @samp{--all} option is specified, then all inferiors will be started.
26618 @subsubheading @value{GDBN} Command
26620 The corresponding @value{GDBN} command is @samp{run}.
26622 @subsubheading Examples
26627 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26632 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26633 frame=@{func="main",args=[],file="recursive2.c",
26634 fullname="/home/foo/bar/recursive2.c",line="4"@}
26639 Program exited normally:
26647 *stopped,reason="exited-normally"
26652 Program exited exceptionally:
26660 *stopped,reason="exited",exit-code="01"
26664 Another way the program can terminate is if it receives a signal such as
26665 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26669 *stopped,reason="exited-signalled",signal-name="SIGINT",
26670 signal-meaning="Interrupt"
26674 @c @subheading -exec-signal
26677 @subheading The @code{-exec-step} Command
26680 @subsubheading Synopsis
26683 -exec-step [--reverse]
26686 Resumes execution of the inferior program, stopping when the beginning
26687 of the next source line is reached, if the next source line is not a
26688 function call. If it is, stop at the first instruction of the called
26689 function. If the @samp{--reverse} option is specified, resumes reverse
26690 execution of the inferior program, stopping at the beginning of the
26691 previously executed source line.
26693 @subsubheading @value{GDBN} Command
26695 The corresponding @value{GDBN} command is @samp{step}.
26697 @subsubheading Example
26699 Stepping into a function:
26705 *stopped,reason="end-stepping-range",
26706 frame=@{func="foo",args=[@{name="a",value="10"@},
26707 @{name="b",value="0"@}],file="recursive2.c",
26708 fullname="/home/foo/bar/recursive2.c",line="11"@}
26718 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26723 @subheading The @code{-exec-step-instruction} Command
26724 @findex -exec-step-instruction
26726 @subsubheading Synopsis
26729 -exec-step-instruction [--reverse]
26732 Resumes the inferior which executes one machine instruction. If the
26733 @samp{--reverse} option is specified, resumes reverse execution of the
26734 inferior program, stopping at the previously executed instruction.
26735 The output, once @value{GDBN} has stopped, will vary depending on
26736 whether we have stopped in the middle of a source line or not. In the
26737 former case, the address at which the program stopped will be printed
26740 @subsubheading @value{GDBN} Command
26742 The corresponding @value{GDBN} command is @samp{stepi}.
26744 @subsubheading Example
26748 -exec-step-instruction
26752 *stopped,reason="end-stepping-range",
26753 frame=@{func="foo",args=[],file="try.c",
26754 fullname="/home/foo/bar/try.c",line="10"@}
26756 -exec-step-instruction
26760 *stopped,reason="end-stepping-range",
26761 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26762 fullname="/home/foo/bar/try.c",line="10"@}
26767 @subheading The @code{-exec-until} Command
26768 @findex -exec-until
26770 @subsubheading Synopsis
26773 -exec-until [ @var{location} ]
26776 Executes the inferior until the @var{location} specified in the
26777 argument is reached. If there is no argument, the inferior executes
26778 until a source line greater than the current one is reached. The
26779 reason for stopping in this case will be @samp{location-reached}.
26781 @subsubheading @value{GDBN} Command
26783 The corresponding @value{GDBN} command is @samp{until}.
26785 @subsubheading Example
26789 -exec-until recursive2.c:6
26793 *stopped,reason="location-reached",frame=@{func="main",args=[],
26794 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26799 @subheading -file-clear
26800 Is this going away????
26803 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26804 @node GDB/MI Stack Manipulation
26805 @section @sc{gdb/mi} Stack Manipulation Commands
26808 @subheading The @code{-stack-info-frame} Command
26809 @findex -stack-info-frame
26811 @subsubheading Synopsis
26817 Get info on the selected frame.
26819 @subsubheading @value{GDBN} Command
26821 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26822 (without arguments).
26824 @subsubheading Example
26829 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26830 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26831 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26835 @subheading The @code{-stack-info-depth} Command
26836 @findex -stack-info-depth
26838 @subsubheading Synopsis
26841 -stack-info-depth [ @var{max-depth} ]
26844 Return the depth of the stack. If the integer argument @var{max-depth}
26845 is specified, do not count beyond @var{max-depth} frames.
26847 @subsubheading @value{GDBN} Command
26849 There's no equivalent @value{GDBN} command.
26851 @subsubheading Example
26853 For a stack with frame levels 0 through 11:
26860 -stack-info-depth 4
26863 -stack-info-depth 12
26866 -stack-info-depth 11
26869 -stack-info-depth 13
26874 @subheading The @code{-stack-list-arguments} Command
26875 @findex -stack-list-arguments
26877 @subsubheading Synopsis
26880 -stack-list-arguments @var{print-values}
26881 [ @var{low-frame} @var{high-frame} ]
26884 Display a list of the arguments for the frames between @var{low-frame}
26885 and @var{high-frame} (inclusive). If @var{low-frame} and
26886 @var{high-frame} are not provided, list the arguments for the whole
26887 call stack. If the two arguments are equal, show the single frame
26888 at the corresponding level. It is an error if @var{low-frame} is
26889 larger than the actual number of frames. On the other hand,
26890 @var{high-frame} may be larger than the actual number of frames, in
26891 which case only existing frames will be returned.
26893 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26894 the variables; if it is 1 or @code{--all-values}, print also their
26895 values; and if it is 2 or @code{--simple-values}, print the name,
26896 type and value for simple data types, and the name and type for arrays,
26897 structures and unions.
26899 Use of this command to obtain arguments in a single frame is
26900 deprecated in favor of the @samp{-stack-list-variables} command.
26902 @subsubheading @value{GDBN} Command
26904 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26905 @samp{gdb_get_args} command which partially overlaps with the
26906 functionality of @samp{-stack-list-arguments}.
26908 @subsubheading Example
26915 frame=@{level="0",addr="0x00010734",func="callee4",
26916 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26917 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26918 frame=@{level="1",addr="0x0001076c",func="callee3",
26919 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26920 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26921 frame=@{level="2",addr="0x0001078c",func="callee2",
26922 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26923 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26924 frame=@{level="3",addr="0x000107b4",func="callee1",
26925 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26926 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26927 frame=@{level="4",addr="0x000107e0",func="main",
26928 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26929 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26931 -stack-list-arguments 0
26934 frame=@{level="0",args=[]@},
26935 frame=@{level="1",args=[name="strarg"]@},
26936 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26937 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26938 frame=@{level="4",args=[]@}]
26940 -stack-list-arguments 1
26943 frame=@{level="0",args=[]@},
26945 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26946 frame=@{level="2",args=[
26947 @{name="intarg",value="2"@},
26948 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26949 @{frame=@{level="3",args=[
26950 @{name="intarg",value="2"@},
26951 @{name="strarg",value="0x11940 \"A string argument.\""@},
26952 @{name="fltarg",value="3.5"@}]@},
26953 frame=@{level="4",args=[]@}]
26955 -stack-list-arguments 0 2 2
26956 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26958 -stack-list-arguments 1 2 2
26959 ^done,stack-args=[frame=@{level="2",
26960 args=[@{name="intarg",value="2"@},
26961 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26965 @c @subheading -stack-list-exception-handlers
26968 @subheading The @code{-stack-list-frames} Command
26969 @findex -stack-list-frames
26971 @subsubheading Synopsis
26974 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26977 List the frames currently on the stack. For each frame it displays the
26982 The frame number, 0 being the topmost frame, i.e., the innermost function.
26984 The @code{$pc} value for that frame.
26988 File name of the source file where the function lives.
26989 @item @var{fullname}
26990 The full file name of the source file where the function lives.
26992 Line number corresponding to the @code{$pc}.
26994 The shared library where this function is defined. This is only given
26995 if the frame's function is not known.
26998 If invoked without arguments, this command prints a backtrace for the
26999 whole stack. If given two integer arguments, it shows the frames whose
27000 levels are between the two arguments (inclusive). If the two arguments
27001 are equal, it shows the single frame at the corresponding level. It is
27002 an error if @var{low-frame} is larger than the actual number of
27003 frames. On the other hand, @var{high-frame} may be larger than the
27004 actual number of frames, in which case only existing frames will be returned.
27006 @subsubheading @value{GDBN} Command
27008 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27010 @subsubheading Example
27012 Full stack backtrace:
27018 [frame=@{level="0",addr="0x0001076c",func="foo",
27019 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27020 frame=@{level="1",addr="0x000107a4",func="foo",
27021 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27022 frame=@{level="2",addr="0x000107a4",func="foo",
27023 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27024 frame=@{level="3",addr="0x000107a4",func="foo",
27025 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27026 frame=@{level="4",addr="0x000107a4",func="foo",
27027 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27028 frame=@{level="5",addr="0x000107a4",func="foo",
27029 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27030 frame=@{level="6",addr="0x000107a4",func="foo",
27031 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27032 frame=@{level="7",addr="0x000107a4",func="foo",
27033 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27034 frame=@{level="8",addr="0x000107a4",func="foo",
27035 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27036 frame=@{level="9",addr="0x000107a4",func="foo",
27037 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27038 frame=@{level="10",addr="0x000107a4",func="foo",
27039 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27040 frame=@{level="11",addr="0x00010738",func="main",
27041 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27045 Show frames between @var{low_frame} and @var{high_frame}:
27049 -stack-list-frames 3 5
27051 [frame=@{level="3",addr="0x000107a4",func="foo",
27052 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27053 frame=@{level="4",addr="0x000107a4",func="foo",
27054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27055 frame=@{level="5",addr="0x000107a4",func="foo",
27056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27060 Show a single frame:
27064 -stack-list-frames 3 3
27066 [frame=@{level="3",addr="0x000107a4",func="foo",
27067 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27072 @subheading The @code{-stack-list-locals} Command
27073 @findex -stack-list-locals
27075 @subsubheading Synopsis
27078 -stack-list-locals @var{print-values}
27081 Display the local variable names for the selected frame. If
27082 @var{print-values} is 0 or @code{--no-values}, print only the names of
27083 the variables; if it is 1 or @code{--all-values}, print also their
27084 values; and if it is 2 or @code{--simple-values}, print the name,
27085 type and value for simple data types, and the name and type for arrays,
27086 structures and unions. In this last case, a frontend can immediately
27087 display the value of simple data types and create variable objects for
27088 other data types when the user wishes to explore their values in
27091 This command is deprecated in favor of the
27092 @samp{-stack-list-variables} command.
27094 @subsubheading @value{GDBN} Command
27096 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27098 @subsubheading Example
27102 -stack-list-locals 0
27103 ^done,locals=[name="A",name="B",name="C"]
27105 -stack-list-locals --all-values
27106 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27107 @{name="C",value="@{1, 2, 3@}"@}]
27108 -stack-list-locals --simple-values
27109 ^done,locals=[@{name="A",type="int",value="1"@},
27110 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27114 @subheading The @code{-stack-list-variables} Command
27115 @findex -stack-list-variables
27117 @subsubheading Synopsis
27120 -stack-list-variables @var{print-values}
27123 Display the names of local variables and function arguments for the selected frame. If
27124 @var{print-values} is 0 or @code{--no-values}, print only the names of
27125 the variables; if it is 1 or @code{--all-values}, print also their
27126 values; and if it is 2 or @code{--simple-values}, print the name,
27127 type and value for simple data types, and the name and type for arrays,
27128 structures and unions.
27130 @subsubheading Example
27134 -stack-list-variables --thread 1 --frame 0 --all-values
27135 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27140 @subheading The @code{-stack-select-frame} Command
27141 @findex -stack-select-frame
27143 @subsubheading Synopsis
27146 -stack-select-frame @var{framenum}
27149 Change the selected frame. Select a different frame @var{framenum} on
27152 This command in deprecated in favor of passing the @samp{--frame}
27153 option to every command.
27155 @subsubheading @value{GDBN} Command
27157 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27158 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27160 @subsubheading Example
27164 -stack-select-frame 2
27169 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27170 @node GDB/MI Variable Objects
27171 @section @sc{gdb/mi} Variable Objects
27175 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27177 For the implementation of a variable debugger window (locals, watched
27178 expressions, etc.), we are proposing the adaptation of the existing code
27179 used by @code{Insight}.
27181 The two main reasons for that are:
27185 It has been proven in practice (it is already on its second generation).
27188 It will shorten development time (needless to say how important it is
27192 The original interface was designed to be used by Tcl code, so it was
27193 slightly changed so it could be used through @sc{gdb/mi}. This section
27194 describes the @sc{gdb/mi} operations that will be available and gives some
27195 hints about their use.
27197 @emph{Note}: In addition to the set of operations described here, we
27198 expect the @sc{gui} implementation of a variable window to require, at
27199 least, the following operations:
27202 @item @code{-gdb-show} @code{output-radix}
27203 @item @code{-stack-list-arguments}
27204 @item @code{-stack-list-locals}
27205 @item @code{-stack-select-frame}
27210 @subheading Introduction to Variable Objects
27212 @cindex variable objects in @sc{gdb/mi}
27214 Variable objects are "object-oriented" MI interface for examining and
27215 changing values of expressions. Unlike some other MI interfaces that
27216 work with expressions, variable objects are specifically designed for
27217 simple and efficient presentation in the frontend. A variable object
27218 is identified by string name. When a variable object is created, the
27219 frontend specifies the expression for that variable object. The
27220 expression can be a simple variable, or it can be an arbitrary complex
27221 expression, and can even involve CPU registers. After creating a
27222 variable object, the frontend can invoke other variable object
27223 operations---for example to obtain or change the value of a variable
27224 object, or to change display format.
27226 Variable objects have hierarchical tree structure. Any variable object
27227 that corresponds to a composite type, such as structure in C, has
27228 a number of child variable objects, for example corresponding to each
27229 element of a structure. A child variable object can itself have
27230 children, recursively. Recursion ends when we reach
27231 leaf variable objects, which always have built-in types. Child variable
27232 objects are created only by explicit request, so if a frontend
27233 is not interested in the children of a particular variable object, no
27234 child will be created.
27236 For a leaf variable object it is possible to obtain its value as a
27237 string, or set the value from a string. String value can be also
27238 obtained for a non-leaf variable object, but it's generally a string
27239 that only indicates the type of the object, and does not list its
27240 contents. Assignment to a non-leaf variable object is not allowed.
27242 A frontend does not need to read the values of all variable objects each time
27243 the program stops. Instead, MI provides an update command that lists all
27244 variable objects whose values has changed since the last update
27245 operation. This considerably reduces the amount of data that must
27246 be transferred to the frontend. As noted above, children variable
27247 objects are created on demand, and only leaf variable objects have a
27248 real value. As result, gdb will read target memory only for leaf
27249 variables that frontend has created.
27251 The automatic update is not always desirable. For example, a frontend
27252 might want to keep a value of some expression for future reference,
27253 and never update it. For another example, fetching memory is
27254 relatively slow for embedded targets, so a frontend might want
27255 to disable automatic update for the variables that are either not
27256 visible on the screen, or ``closed''. This is possible using so
27257 called ``frozen variable objects''. Such variable objects are never
27258 implicitly updated.
27260 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27261 fixed variable object, the expression is parsed when the variable
27262 object is created, including associating identifiers to specific
27263 variables. The meaning of expression never changes. For a floating
27264 variable object the values of variables whose names appear in the
27265 expressions are re-evaluated every time in the context of the current
27266 frame. Consider this example:
27271 struct work_state state;
27278 If a fixed variable object for the @code{state} variable is created in
27279 this function, and we enter the recursive call, the variable
27280 object will report the value of @code{state} in the top-level
27281 @code{do_work} invocation. On the other hand, a floating variable
27282 object will report the value of @code{state} in the current frame.
27284 If an expression specified when creating a fixed variable object
27285 refers to a local variable, the variable object becomes bound to the
27286 thread and frame in which the variable object is created. When such
27287 variable object is updated, @value{GDBN} makes sure that the
27288 thread/frame combination the variable object is bound to still exists,
27289 and re-evaluates the variable object in context of that thread/frame.
27291 The following is the complete set of @sc{gdb/mi} operations defined to
27292 access this functionality:
27294 @multitable @columnfractions .4 .6
27295 @item @strong{Operation}
27296 @tab @strong{Description}
27298 @item @code{-enable-pretty-printing}
27299 @tab enable Python-based pretty-printing
27300 @item @code{-var-create}
27301 @tab create a variable object
27302 @item @code{-var-delete}
27303 @tab delete the variable object and/or its children
27304 @item @code{-var-set-format}
27305 @tab set the display format of this variable
27306 @item @code{-var-show-format}
27307 @tab show the display format of this variable
27308 @item @code{-var-info-num-children}
27309 @tab tells how many children this object has
27310 @item @code{-var-list-children}
27311 @tab return a list of the object's children
27312 @item @code{-var-info-type}
27313 @tab show the type of this variable object
27314 @item @code{-var-info-expression}
27315 @tab print parent-relative expression that this variable object represents
27316 @item @code{-var-info-path-expression}
27317 @tab print full expression that this variable object represents
27318 @item @code{-var-show-attributes}
27319 @tab is this variable editable? does it exist here?
27320 @item @code{-var-evaluate-expression}
27321 @tab get the value of this variable
27322 @item @code{-var-assign}
27323 @tab set the value of this variable
27324 @item @code{-var-update}
27325 @tab update the variable and its children
27326 @item @code{-var-set-frozen}
27327 @tab set frozeness attribute
27328 @item @code{-var-set-update-range}
27329 @tab set range of children to display on update
27332 In the next subsection we describe each operation in detail and suggest
27333 how it can be used.
27335 @subheading Description And Use of Operations on Variable Objects
27337 @subheading The @code{-enable-pretty-printing} Command
27338 @findex -enable-pretty-printing
27341 -enable-pretty-printing
27344 @value{GDBN} allows Python-based visualizers to affect the output of the
27345 MI variable object commands. However, because there was no way to
27346 implement this in a fully backward-compatible way, a front end must
27347 request that this functionality be enabled.
27349 Once enabled, this feature cannot be disabled.
27351 Note that if Python support has not been compiled into @value{GDBN},
27352 this command will still succeed (and do nothing).
27354 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27355 may work differently in future versions of @value{GDBN}.
27357 @subheading The @code{-var-create} Command
27358 @findex -var-create
27360 @subsubheading Synopsis
27363 -var-create @{@var{name} | "-"@}
27364 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27367 This operation creates a variable object, which allows the monitoring of
27368 a variable, the result of an expression, a memory cell or a CPU
27371 The @var{name} parameter is the string by which the object can be
27372 referenced. It must be unique. If @samp{-} is specified, the varobj
27373 system will generate a string ``varNNNNNN'' automatically. It will be
27374 unique provided that one does not specify @var{name} of that format.
27375 The command fails if a duplicate name is found.
27377 The frame under which the expression should be evaluated can be
27378 specified by @var{frame-addr}. A @samp{*} indicates that the current
27379 frame should be used. A @samp{@@} indicates that a floating variable
27380 object must be created.
27382 @var{expression} is any expression valid on the current language set (must not
27383 begin with a @samp{*}), or one of the following:
27387 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27390 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27393 @samp{$@var{regname}} --- a CPU register name
27396 @cindex dynamic varobj
27397 A varobj's contents may be provided by a Python-based pretty-printer. In this
27398 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27399 have slightly different semantics in some cases. If the
27400 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27401 will never create a dynamic varobj. This ensures backward
27402 compatibility for existing clients.
27404 @subsubheading Result
27406 This operation returns attributes of the newly-created varobj. These
27411 The name of the varobj.
27414 The number of children of the varobj. This number is not necessarily
27415 reliable for a dynamic varobj. Instead, you must examine the
27416 @samp{has_more} attribute.
27419 The varobj's scalar value. For a varobj whose type is some sort of
27420 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27421 will not be interesting.
27424 The varobj's type. This is a string representation of the type, as
27425 would be printed by the @value{GDBN} CLI.
27428 If a variable object is bound to a specific thread, then this is the
27429 thread's identifier.
27432 For a dynamic varobj, this indicates whether there appear to be any
27433 children available. For a non-dynamic varobj, this will be 0.
27436 This attribute will be present and have the value @samp{1} if the
27437 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27438 then this attribute will not be present.
27441 A dynamic varobj can supply a display hint to the front end. The
27442 value comes directly from the Python pretty-printer object's
27443 @code{display_hint} method. @xref{Pretty Printing API}.
27446 Typical output will look like this:
27449 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27450 has_more="@var{has_more}"
27454 @subheading The @code{-var-delete} Command
27455 @findex -var-delete
27457 @subsubheading Synopsis
27460 -var-delete [ -c ] @var{name}
27463 Deletes a previously created variable object and all of its children.
27464 With the @samp{-c} option, just deletes the children.
27466 Returns an error if the object @var{name} is not found.
27469 @subheading The @code{-var-set-format} Command
27470 @findex -var-set-format
27472 @subsubheading Synopsis
27475 -var-set-format @var{name} @var{format-spec}
27478 Sets the output format for the value of the object @var{name} to be
27481 @anchor{-var-set-format}
27482 The syntax for the @var{format-spec} is as follows:
27485 @var{format-spec} @expansion{}
27486 @{binary | decimal | hexadecimal | octal | natural@}
27489 The natural format is the default format choosen automatically
27490 based on the variable type (like decimal for an @code{int}, hex
27491 for pointers, etc.).
27493 For a variable with children, the format is set only on the
27494 variable itself, and the children are not affected.
27496 @subheading The @code{-var-show-format} Command
27497 @findex -var-show-format
27499 @subsubheading Synopsis
27502 -var-show-format @var{name}
27505 Returns the format used to display the value of the object @var{name}.
27508 @var{format} @expansion{}
27513 @subheading The @code{-var-info-num-children} Command
27514 @findex -var-info-num-children
27516 @subsubheading Synopsis
27519 -var-info-num-children @var{name}
27522 Returns the number of children of a variable object @var{name}:
27528 Note that this number is not completely reliable for a dynamic varobj.
27529 It will return the current number of children, but more children may
27533 @subheading The @code{-var-list-children} Command
27534 @findex -var-list-children
27536 @subsubheading Synopsis
27539 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27541 @anchor{-var-list-children}
27543 Return a list of the children of the specified variable object and
27544 create variable objects for them, if they do not already exist. With
27545 a single argument or if @var{print-values} has a value of 0 or
27546 @code{--no-values}, print only the names of the variables; if
27547 @var{print-values} is 1 or @code{--all-values}, also print their
27548 values; and if it is 2 or @code{--simple-values} print the name and
27549 value for simple data types and just the name for arrays, structures
27552 @var{from} and @var{to}, if specified, indicate the range of children
27553 to report. If @var{from} or @var{to} is less than zero, the range is
27554 reset and all children will be reported. Otherwise, children starting
27555 at @var{from} (zero-based) and up to and excluding @var{to} will be
27558 If a child range is requested, it will only affect the current call to
27559 @code{-var-list-children}, but not future calls to @code{-var-update}.
27560 For this, you must instead use @code{-var-set-update-range}. The
27561 intent of this approach is to enable a front end to implement any
27562 update approach it likes; for example, scrolling a view may cause the
27563 front end to request more children with @code{-var-list-children}, and
27564 then the front end could call @code{-var-set-update-range} with a
27565 different range to ensure that future updates are restricted to just
27568 For each child the following results are returned:
27573 Name of the variable object created for this child.
27576 The expression to be shown to the user by the front end to designate this child.
27577 For example this may be the name of a structure member.
27579 For a dynamic varobj, this value cannot be used to form an
27580 expression. There is no way to do this at all with a dynamic varobj.
27582 For C/C@t{++} structures there are several pseudo children returned to
27583 designate access qualifiers. For these pseudo children @var{exp} is
27584 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27585 type and value are not present.
27587 A dynamic varobj will not report the access qualifying
27588 pseudo-children, regardless of the language. This information is not
27589 available at all with a dynamic varobj.
27592 Number of children this child has. For a dynamic varobj, this will be
27596 The type of the child.
27599 If values were requested, this is the value.
27602 If this variable object is associated with a thread, this is the thread id.
27603 Otherwise this result is not present.
27606 If the variable object is frozen, this variable will be present with a value of 1.
27609 The result may have its own attributes:
27613 A dynamic varobj can supply a display hint to the front end. The
27614 value comes directly from the Python pretty-printer object's
27615 @code{display_hint} method. @xref{Pretty Printing API}.
27618 This is an integer attribute which is nonzero if there are children
27619 remaining after the end of the selected range.
27622 @subsubheading Example
27626 -var-list-children n
27627 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27628 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27630 -var-list-children --all-values n
27631 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27632 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27636 @subheading The @code{-var-info-type} Command
27637 @findex -var-info-type
27639 @subsubheading Synopsis
27642 -var-info-type @var{name}
27645 Returns the type of the specified variable @var{name}. The type is
27646 returned as a string in the same format as it is output by the
27650 type=@var{typename}
27654 @subheading The @code{-var-info-expression} Command
27655 @findex -var-info-expression
27657 @subsubheading Synopsis
27660 -var-info-expression @var{name}
27663 Returns a string that is suitable for presenting this
27664 variable object in user interface. The string is generally
27665 not valid expression in the current language, and cannot be evaluated.
27667 For example, if @code{a} is an array, and variable object
27668 @code{A} was created for @code{a}, then we'll get this output:
27671 (gdb) -var-info-expression A.1
27672 ^done,lang="C",exp="1"
27676 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27678 Note that the output of the @code{-var-list-children} command also
27679 includes those expressions, so the @code{-var-info-expression} command
27682 @subheading The @code{-var-info-path-expression} Command
27683 @findex -var-info-path-expression
27685 @subsubheading Synopsis
27688 -var-info-path-expression @var{name}
27691 Returns an expression that can be evaluated in the current
27692 context and will yield the same value that a variable object has.
27693 Compare this with the @code{-var-info-expression} command, which
27694 result can be used only for UI presentation. Typical use of
27695 the @code{-var-info-path-expression} command is creating a
27696 watchpoint from a variable object.
27698 This command is currently not valid for children of a dynamic varobj,
27699 and will give an error when invoked on one.
27701 For example, suppose @code{C} is a C@t{++} class, derived from class
27702 @code{Base}, and that the @code{Base} class has a member called
27703 @code{m_size}. Assume a variable @code{c} is has the type of
27704 @code{C} and a variable object @code{C} was created for variable
27705 @code{c}. Then, we'll get this output:
27707 (gdb) -var-info-path-expression C.Base.public.m_size
27708 ^done,path_expr=((Base)c).m_size)
27711 @subheading The @code{-var-show-attributes} Command
27712 @findex -var-show-attributes
27714 @subsubheading Synopsis
27717 -var-show-attributes @var{name}
27720 List attributes of the specified variable object @var{name}:
27723 status=@var{attr} [ ( ,@var{attr} )* ]
27727 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27729 @subheading The @code{-var-evaluate-expression} Command
27730 @findex -var-evaluate-expression
27732 @subsubheading Synopsis
27735 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27738 Evaluates the expression that is represented by the specified variable
27739 object and returns its value as a string. The format of the string
27740 can be specified with the @samp{-f} option. The possible values of
27741 this option are the same as for @code{-var-set-format}
27742 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27743 the current display format will be used. The current display format
27744 can be changed using the @code{-var-set-format} command.
27750 Note that one must invoke @code{-var-list-children} for a variable
27751 before the value of a child variable can be evaluated.
27753 @subheading The @code{-var-assign} Command
27754 @findex -var-assign
27756 @subsubheading Synopsis
27759 -var-assign @var{name} @var{expression}
27762 Assigns the value of @var{expression} to the variable object specified
27763 by @var{name}. The object must be @samp{editable}. If the variable's
27764 value is altered by the assign, the variable will show up in any
27765 subsequent @code{-var-update} list.
27767 @subsubheading Example
27775 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27779 @subheading The @code{-var-update} Command
27780 @findex -var-update
27782 @subsubheading Synopsis
27785 -var-update [@var{print-values}] @{@var{name} | "*"@}
27788 Reevaluate the expressions corresponding to the variable object
27789 @var{name} and all its direct and indirect children, and return the
27790 list of variable objects whose values have changed; @var{name} must
27791 be a root variable object. Here, ``changed'' means that the result of
27792 @code{-var-evaluate-expression} before and after the
27793 @code{-var-update} is different. If @samp{*} is used as the variable
27794 object names, all existing variable objects are updated, except
27795 for frozen ones (@pxref{-var-set-frozen}). The option
27796 @var{print-values} determines whether both names and values, or just
27797 names are printed. The possible values of this option are the same
27798 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27799 recommended to use the @samp{--all-values} option, to reduce the
27800 number of MI commands needed on each program stop.
27802 With the @samp{*} parameter, if a variable object is bound to a
27803 currently running thread, it will not be updated, without any
27806 If @code{-var-set-update-range} was previously used on a varobj, then
27807 only the selected range of children will be reported.
27809 @code{-var-update} reports all the changed varobjs in a tuple named
27812 Each item in the change list is itself a tuple holding:
27816 The name of the varobj.
27819 If values were requested for this update, then this field will be
27820 present and will hold the value of the varobj.
27823 @anchor{-var-update}
27824 This field is a string which may take one of three values:
27828 The variable object's current value is valid.
27831 The variable object does not currently hold a valid value but it may
27832 hold one in the future if its associated expression comes back into
27836 The variable object no longer holds a valid value.
27837 This can occur when the executable file being debugged has changed,
27838 either through recompilation or by using the @value{GDBN} @code{file}
27839 command. The front end should normally choose to delete these variable
27843 In the future new values may be added to this list so the front should
27844 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27847 This is only present if the varobj is still valid. If the type
27848 changed, then this will be the string @samp{true}; otherwise it will
27852 If the varobj's type changed, then this field will be present and will
27855 @item new_num_children
27856 For a dynamic varobj, if the number of children changed, or if the
27857 type changed, this will be the new number of children.
27859 The @samp{numchild} field in other varobj responses is generally not
27860 valid for a dynamic varobj -- it will show the number of children that
27861 @value{GDBN} knows about, but because dynamic varobjs lazily
27862 instantiate their children, this will not reflect the number of
27863 children which may be available.
27865 The @samp{new_num_children} attribute only reports changes to the
27866 number of children known by @value{GDBN}. This is the only way to
27867 detect whether an update has removed children (which necessarily can
27868 only happen at the end of the update range).
27871 The display hint, if any.
27874 This is an integer value, which will be 1 if there are more children
27875 available outside the varobj's update range.
27878 This attribute will be present and have the value @samp{1} if the
27879 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27880 then this attribute will not be present.
27883 If new children were added to a dynamic varobj within the selected
27884 update range (as set by @code{-var-set-update-range}), then they will
27885 be listed in this attribute.
27888 @subsubheading Example
27895 -var-update --all-values var1
27896 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27897 type_changed="false"@}]
27901 @subheading The @code{-var-set-frozen} Command
27902 @findex -var-set-frozen
27903 @anchor{-var-set-frozen}
27905 @subsubheading Synopsis
27908 -var-set-frozen @var{name} @var{flag}
27911 Set the frozenness flag on the variable object @var{name}. The
27912 @var{flag} parameter should be either @samp{1} to make the variable
27913 frozen or @samp{0} to make it unfrozen. If a variable object is
27914 frozen, then neither itself, nor any of its children, are
27915 implicitly updated by @code{-var-update} of
27916 a parent variable or by @code{-var-update *}. Only
27917 @code{-var-update} of the variable itself will update its value and
27918 values of its children. After a variable object is unfrozen, it is
27919 implicitly updated by all subsequent @code{-var-update} operations.
27920 Unfreezing a variable does not update it, only subsequent
27921 @code{-var-update} does.
27923 @subsubheading Example
27927 -var-set-frozen V 1
27932 @subheading The @code{-var-set-update-range} command
27933 @findex -var-set-update-range
27934 @anchor{-var-set-update-range}
27936 @subsubheading Synopsis
27939 -var-set-update-range @var{name} @var{from} @var{to}
27942 Set the range of children to be returned by future invocations of
27943 @code{-var-update}.
27945 @var{from} and @var{to} indicate the range of children to report. If
27946 @var{from} or @var{to} is less than zero, the range is reset and all
27947 children will be reported. Otherwise, children starting at @var{from}
27948 (zero-based) and up to and excluding @var{to} will be reported.
27950 @subsubheading Example
27954 -var-set-update-range V 1 2
27958 @subheading The @code{-var-set-visualizer} command
27959 @findex -var-set-visualizer
27960 @anchor{-var-set-visualizer}
27962 @subsubheading Synopsis
27965 -var-set-visualizer @var{name} @var{visualizer}
27968 Set a visualizer for the variable object @var{name}.
27970 @var{visualizer} is the visualizer to use. The special value
27971 @samp{None} means to disable any visualizer in use.
27973 If not @samp{None}, @var{visualizer} must be a Python expression.
27974 This expression must evaluate to a callable object which accepts a
27975 single argument. @value{GDBN} will call this object with the value of
27976 the varobj @var{name} as an argument (this is done so that the same
27977 Python pretty-printing code can be used for both the CLI and MI).
27978 When called, this object must return an object which conforms to the
27979 pretty-printing interface (@pxref{Pretty Printing API}).
27981 The pre-defined function @code{gdb.default_visualizer} may be used to
27982 select a visualizer by following the built-in process
27983 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27984 a varobj is created, and so ordinarily is not needed.
27986 This feature is only available if Python support is enabled. The MI
27987 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27988 can be used to check this.
27990 @subsubheading Example
27992 Resetting the visualizer:
27996 -var-set-visualizer V None
28000 Reselecting the default (type-based) visualizer:
28004 -var-set-visualizer V gdb.default_visualizer
28008 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28009 can be used to instantiate this class for a varobj:
28013 -var-set-visualizer V "lambda val: SomeClass()"
28017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28018 @node GDB/MI Data Manipulation
28019 @section @sc{gdb/mi} Data Manipulation
28021 @cindex data manipulation, in @sc{gdb/mi}
28022 @cindex @sc{gdb/mi}, data manipulation
28023 This section describes the @sc{gdb/mi} commands that manipulate data:
28024 examine memory and registers, evaluate expressions, etc.
28026 @c REMOVED FROM THE INTERFACE.
28027 @c @subheading -data-assign
28028 @c Change the value of a program variable. Plenty of side effects.
28029 @c @subsubheading GDB Command
28031 @c @subsubheading Example
28034 @subheading The @code{-data-disassemble} Command
28035 @findex -data-disassemble
28037 @subsubheading Synopsis
28041 [ -s @var{start-addr} -e @var{end-addr} ]
28042 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28050 @item @var{start-addr}
28051 is the beginning address (or @code{$pc})
28052 @item @var{end-addr}
28054 @item @var{filename}
28055 is the name of the file to disassemble
28056 @item @var{linenum}
28057 is the line number to disassemble around
28059 is the number of disassembly lines to be produced. If it is -1,
28060 the whole function will be disassembled, in case no @var{end-addr} is
28061 specified. If @var{end-addr} is specified as a non-zero value, and
28062 @var{lines} is lower than the number of disassembly lines between
28063 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28064 displayed; if @var{lines} is higher than the number of lines between
28065 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28068 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28069 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28070 mixed source and disassembly with raw opcodes).
28073 @subsubheading Result
28075 The output for each instruction is composed of four fields:
28084 Note that whatever included in the instruction field, is not manipulated
28085 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28087 @subsubheading @value{GDBN} Command
28089 There's no direct mapping from this command to the CLI.
28091 @subsubheading Example
28093 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28097 -data-disassemble -s $pc -e "$pc + 20" -- 0
28100 @{address="0x000107c0",func-name="main",offset="4",
28101 inst="mov 2, %o0"@},
28102 @{address="0x000107c4",func-name="main",offset="8",
28103 inst="sethi %hi(0x11800), %o2"@},
28104 @{address="0x000107c8",func-name="main",offset="12",
28105 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28106 @{address="0x000107cc",func-name="main",offset="16",
28107 inst="sethi %hi(0x11800), %o2"@},
28108 @{address="0x000107d0",func-name="main",offset="20",
28109 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28113 Disassemble the whole @code{main} function. Line 32 is part of
28117 -data-disassemble -f basics.c -l 32 -- 0
28119 @{address="0x000107bc",func-name="main",offset="0",
28120 inst="save %sp, -112, %sp"@},
28121 @{address="0x000107c0",func-name="main",offset="4",
28122 inst="mov 2, %o0"@},
28123 @{address="0x000107c4",func-name="main",offset="8",
28124 inst="sethi %hi(0x11800), %o2"@},
28126 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28127 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28131 Disassemble 3 instructions from the start of @code{main}:
28135 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28137 @{address="0x000107bc",func-name="main",offset="0",
28138 inst="save %sp, -112, %sp"@},
28139 @{address="0x000107c0",func-name="main",offset="4",
28140 inst="mov 2, %o0"@},
28141 @{address="0x000107c4",func-name="main",offset="8",
28142 inst="sethi %hi(0x11800), %o2"@}]
28146 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28150 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28152 src_and_asm_line=@{line="31",
28153 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28154 testsuite/gdb.mi/basics.c",line_asm_insn=[
28155 @{address="0x000107bc",func-name="main",offset="0",
28156 inst="save %sp, -112, %sp"@}]@},
28157 src_and_asm_line=@{line="32",
28158 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28159 testsuite/gdb.mi/basics.c",line_asm_insn=[
28160 @{address="0x000107c0",func-name="main",offset="4",
28161 inst="mov 2, %o0"@},
28162 @{address="0x000107c4",func-name="main",offset="8",
28163 inst="sethi %hi(0x11800), %o2"@}]@}]
28168 @subheading The @code{-data-evaluate-expression} Command
28169 @findex -data-evaluate-expression
28171 @subsubheading Synopsis
28174 -data-evaluate-expression @var{expr}
28177 Evaluate @var{expr} as an expression. The expression could contain an
28178 inferior function call. The function call will execute synchronously.
28179 If the expression contains spaces, it must be enclosed in double quotes.
28181 @subsubheading @value{GDBN} Command
28183 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28184 @samp{call}. In @code{gdbtk} only, there's a corresponding
28185 @samp{gdb_eval} command.
28187 @subsubheading Example
28189 In the following example, the numbers that precede the commands are the
28190 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28191 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28195 211-data-evaluate-expression A
28198 311-data-evaluate-expression &A
28199 311^done,value="0xefffeb7c"
28201 411-data-evaluate-expression A+3
28204 511-data-evaluate-expression "A + 3"
28210 @subheading The @code{-data-list-changed-registers} Command
28211 @findex -data-list-changed-registers
28213 @subsubheading Synopsis
28216 -data-list-changed-registers
28219 Display a list of the registers that have changed.
28221 @subsubheading @value{GDBN} Command
28223 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28224 has the corresponding command @samp{gdb_changed_register_list}.
28226 @subsubheading Example
28228 On a PPC MBX board:
28236 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28237 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28240 -data-list-changed-registers
28241 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28242 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28243 "24","25","26","27","28","30","31","64","65","66","67","69"]
28248 @subheading The @code{-data-list-register-names} Command
28249 @findex -data-list-register-names
28251 @subsubheading Synopsis
28254 -data-list-register-names [ ( @var{regno} )+ ]
28257 Show a list of register names for the current target. If no arguments
28258 are given, it shows a list of the names of all the registers. If
28259 integer numbers are given as arguments, it will print a list of the
28260 names of the registers corresponding to the arguments. To ensure
28261 consistency between a register name and its number, the output list may
28262 include empty register names.
28264 @subsubheading @value{GDBN} Command
28266 @value{GDBN} does not have a command which corresponds to
28267 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28268 corresponding command @samp{gdb_regnames}.
28270 @subsubheading Example
28272 For the PPC MBX board:
28275 -data-list-register-names
28276 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28277 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28278 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28279 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28280 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28281 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28282 "", "pc","ps","cr","lr","ctr","xer"]
28284 -data-list-register-names 1 2 3
28285 ^done,register-names=["r1","r2","r3"]
28289 @subheading The @code{-data-list-register-values} Command
28290 @findex -data-list-register-values
28292 @subsubheading Synopsis
28295 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28298 Display the registers' contents. @var{fmt} is the format according to
28299 which the registers' contents are to be returned, followed by an optional
28300 list of numbers specifying the registers to display. A missing list of
28301 numbers indicates that the contents of all the registers must be returned.
28303 Allowed formats for @var{fmt} are:
28320 @subsubheading @value{GDBN} Command
28322 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28323 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28325 @subsubheading Example
28327 For a PPC MBX board (note: line breaks are for readability only, they
28328 don't appear in the actual output):
28332 -data-list-register-values r 64 65
28333 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28334 @{number="65",value="0x00029002"@}]
28336 -data-list-register-values x
28337 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28338 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28339 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28340 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28341 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28342 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28343 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28344 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28345 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28346 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28347 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28348 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28349 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28350 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28351 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28352 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28353 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28354 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28355 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28356 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28357 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28358 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28359 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28360 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28361 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28362 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28363 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28364 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28365 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28366 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28367 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28368 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28369 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28370 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28371 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28372 @{number="69",value="0x20002b03"@}]
28377 @subheading The @code{-data-read-memory} Command
28378 @findex -data-read-memory
28380 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28382 @subsubheading Synopsis
28385 -data-read-memory [ -o @var{byte-offset} ]
28386 @var{address} @var{word-format} @var{word-size}
28387 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28394 @item @var{address}
28395 An expression specifying the address of the first memory word to be
28396 read. Complex expressions containing embedded white space should be
28397 quoted using the C convention.
28399 @item @var{word-format}
28400 The format to be used to print the memory words. The notation is the
28401 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28404 @item @var{word-size}
28405 The size of each memory word in bytes.
28407 @item @var{nr-rows}
28408 The number of rows in the output table.
28410 @item @var{nr-cols}
28411 The number of columns in the output table.
28414 If present, indicates that each row should include an @sc{ascii} dump. The
28415 value of @var{aschar} is used as a padding character when a byte is not a
28416 member of the printable @sc{ascii} character set (printable @sc{ascii}
28417 characters are those whose code is between 32 and 126, inclusively).
28419 @item @var{byte-offset}
28420 An offset to add to the @var{address} before fetching memory.
28423 This command displays memory contents as a table of @var{nr-rows} by
28424 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28425 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28426 (returned as @samp{total-bytes}). Should less than the requested number
28427 of bytes be returned by the target, the missing words are identified
28428 using @samp{N/A}. The number of bytes read from the target is returned
28429 in @samp{nr-bytes} and the starting address used to read memory in
28432 The address of the next/previous row or page is available in
28433 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28436 @subsubheading @value{GDBN} Command
28438 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28439 @samp{gdb_get_mem} memory read command.
28441 @subsubheading Example
28443 Read six bytes of memory starting at @code{bytes+6} but then offset by
28444 @code{-6} bytes. Format as three rows of two columns. One byte per
28445 word. Display each word in hex.
28449 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28450 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28451 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28452 prev-page="0x0000138a",memory=[
28453 @{addr="0x00001390",data=["0x00","0x01"]@},
28454 @{addr="0x00001392",data=["0x02","0x03"]@},
28455 @{addr="0x00001394",data=["0x04","0x05"]@}]
28459 Read two bytes of memory starting at address @code{shorts + 64} and
28460 display as a single word formatted in decimal.
28464 5-data-read-memory shorts+64 d 2 1 1
28465 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28466 next-row="0x00001512",prev-row="0x0000150e",
28467 next-page="0x00001512",prev-page="0x0000150e",memory=[
28468 @{addr="0x00001510",data=["128"]@}]
28472 Read thirty two bytes of memory starting at @code{bytes+16} and format
28473 as eight rows of four columns. Include a string encoding with @samp{x}
28474 used as the non-printable character.
28478 4-data-read-memory bytes+16 x 1 8 4 x
28479 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28480 next-row="0x000013c0",prev-row="0x0000139c",
28481 next-page="0x000013c0",prev-page="0x00001380",memory=[
28482 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28483 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28484 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28485 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28486 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28487 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28488 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28489 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28493 @subheading The @code{-data-read-memory-bytes} Command
28494 @findex -data-read-memory-bytes
28496 @subsubheading Synopsis
28499 -data-read-memory-bytes [ -o @var{byte-offset} ]
28500 @var{address} @var{count}
28507 @item @var{address}
28508 An expression specifying the address of the first memory word to be
28509 read. Complex expressions containing embedded white space should be
28510 quoted using the C convention.
28513 The number of bytes to read. This should be an integer literal.
28515 @item @var{byte-offset}
28516 The offsets in bytes relative to @var{address} at which to start
28517 reading. This should be an integer literal. This option is provided
28518 so that a frontend is not required to first evaluate address and then
28519 perform address arithmetics itself.
28523 This command attempts to read all accessible memory regions in the
28524 specified range. First, all regions marked as unreadable in the memory
28525 map (if one is defined) will be skipped. @xref{Memory Region
28526 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28527 regions. For each one, if reading full region results in an errors,
28528 @value{GDBN} will try to read a subset of the region.
28530 In general, every single byte in the region may be readable or not,
28531 and the only way to read every readable byte is to try a read at
28532 every address, which is not practical. Therefore, @value{GDBN} will
28533 attempt to read all accessible bytes at either beginning or the end
28534 of the region, using a binary division scheme. This heuristic works
28535 well for reading accross a memory map boundary. Note that if a region
28536 has a readable range that is neither at the beginning or the end,
28537 @value{GDBN} will not read it.
28539 The result record (@pxref{GDB/MI Result Records}) that is output of
28540 the command includes a field named @samp{memory} whose content is a
28541 list of tuples. Each tuple represent a successfully read memory block
28542 and has the following fields:
28546 The start address of the memory block, as hexadecimal literal.
28549 The end address of the memory block, as hexadecimal literal.
28552 The offset of the memory block, as hexadecimal literal, relative to
28553 the start address passed to @code{-data-read-memory-bytes}.
28556 The contents of the memory block, in hex.
28562 @subsubheading @value{GDBN} Command
28564 The corresponding @value{GDBN} command is @samp{x}.
28566 @subsubheading Example
28570 -data-read-memory-bytes &a 10
28571 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28573 contents="01000000020000000300"@}]
28578 @subheading The @code{-data-write-memory-bytes} Command
28579 @findex -data-write-memory-bytes
28581 @subsubheading Synopsis
28584 -data-write-memory-bytes @var{address} @var{contents}
28591 @item @var{address}
28592 An expression specifying the address of the first memory word to be
28593 read. Complex expressions containing embedded white space should be
28594 quoted using the C convention.
28596 @item @var{contents}
28597 The hex-encoded bytes to write.
28601 @subsubheading @value{GDBN} Command
28603 There's no corresponding @value{GDBN} command.
28605 @subsubheading Example
28609 -data-write-memory-bytes &a "aabbccdd"
28615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28616 @node GDB/MI Tracepoint Commands
28617 @section @sc{gdb/mi} Tracepoint Commands
28619 The commands defined in this section implement MI support for
28620 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28622 @subheading The @code{-trace-find} Command
28623 @findex -trace-find
28625 @subsubheading Synopsis
28628 -trace-find @var{mode} [@var{parameters}@dots{}]
28631 Find a trace frame using criteria defined by @var{mode} and
28632 @var{parameters}. The following table lists permissible
28633 modes and their parameters. For details of operation, see @ref{tfind}.
28638 No parameters are required. Stops examining trace frames.
28641 An integer is required as parameter. Selects tracepoint frame with
28644 @item tracepoint-number
28645 An integer is required as parameter. Finds next
28646 trace frame that corresponds to tracepoint with the specified number.
28649 An address is required as parameter. Finds
28650 next trace frame that corresponds to any tracepoint at the specified
28653 @item pc-inside-range
28654 Two addresses are required as parameters. Finds next trace
28655 frame that corresponds to a tracepoint at an address inside the
28656 specified range. Both bounds are considered to be inside the range.
28658 @item pc-outside-range
28659 Two addresses are required as parameters. Finds
28660 next trace frame that corresponds to a tracepoint at an address outside
28661 the specified range. Both bounds are considered to be inside the range.
28664 Line specification is required as parameter. @xref{Specify Location}.
28665 Finds next trace frame that corresponds to a tracepoint at
28666 the specified location.
28670 If @samp{none} was passed as @var{mode}, the response does not
28671 have fields. Otherwise, the response may have the following fields:
28675 This field has either @samp{0} or @samp{1} as the value, depending
28676 on whether a matching tracepoint was found.
28679 The index of the found traceframe. This field is present iff
28680 the @samp{found} field has value of @samp{1}.
28683 The index of the found tracepoint. This field is present iff
28684 the @samp{found} field has value of @samp{1}.
28687 The information about the frame corresponding to the found trace
28688 frame. This field is present only if a trace frame was found.
28689 @xref{GDB/MI Frame Information}, for description of this field.
28693 @subsubheading @value{GDBN} Command
28695 The corresponding @value{GDBN} command is @samp{tfind}.
28697 @subheading -trace-define-variable
28698 @findex -trace-define-variable
28700 @subsubheading Synopsis
28703 -trace-define-variable @var{name} [ @var{value} ]
28706 Create trace variable @var{name} if it does not exist. If
28707 @var{value} is specified, sets the initial value of the specified
28708 trace variable to that value. Note that the @var{name} should start
28709 with the @samp{$} character.
28711 @subsubheading @value{GDBN} Command
28713 The corresponding @value{GDBN} command is @samp{tvariable}.
28715 @subheading -trace-list-variables
28716 @findex -trace-list-variables
28718 @subsubheading Synopsis
28721 -trace-list-variables
28724 Return a table of all defined trace variables. Each element of the
28725 table has the following fields:
28729 The name of the trace variable. This field is always present.
28732 The initial value. This is a 64-bit signed integer. This
28733 field is always present.
28736 The value the trace variable has at the moment. This is a 64-bit
28737 signed integer. This field is absent iff current value is
28738 not defined, for example if the trace was never run, or is
28743 @subsubheading @value{GDBN} Command
28745 The corresponding @value{GDBN} command is @samp{tvariables}.
28747 @subsubheading Example
28751 -trace-list-variables
28752 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28753 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28754 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28755 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28756 body=[variable=@{name="$trace_timestamp",initial="0"@}
28757 variable=@{name="$foo",initial="10",current="15"@}]@}
28761 @subheading -trace-save
28762 @findex -trace-save
28764 @subsubheading Synopsis
28767 -trace-save [-r ] @var{filename}
28770 Saves the collected trace data to @var{filename}. Without the
28771 @samp{-r} option, the data is downloaded from the target and saved
28772 in a local file. With the @samp{-r} option the target is asked
28773 to perform the save.
28775 @subsubheading @value{GDBN} Command
28777 The corresponding @value{GDBN} command is @samp{tsave}.
28780 @subheading -trace-start
28781 @findex -trace-start
28783 @subsubheading Synopsis
28789 Starts a tracing experiments. The result of this command does not
28792 @subsubheading @value{GDBN} Command
28794 The corresponding @value{GDBN} command is @samp{tstart}.
28796 @subheading -trace-status
28797 @findex -trace-status
28799 @subsubheading Synopsis
28805 Obtains the status of a tracing experiment. The result may include
28806 the following fields:
28811 May have a value of either @samp{0}, when no tracing operations are
28812 supported, @samp{1}, when all tracing operations are supported, or
28813 @samp{file} when examining trace file. In the latter case, examining
28814 of trace frame is possible but new tracing experiement cannot be
28815 started. This field is always present.
28818 May have a value of either @samp{0} or @samp{1} depending on whether
28819 tracing experiement is in progress on target. This field is present
28820 if @samp{supported} field is not @samp{0}.
28823 Report the reason why the tracing was stopped last time. This field
28824 may be absent iff tracing was never stopped on target yet. The
28825 value of @samp{request} means the tracing was stopped as result of
28826 the @code{-trace-stop} command. The value of @samp{overflow} means
28827 the tracing buffer is full. The value of @samp{disconnection} means
28828 tracing was automatically stopped when @value{GDBN} has disconnected.
28829 The value of @samp{passcount} means tracing was stopped when a
28830 tracepoint was passed a maximal number of times for that tracepoint.
28831 This field is present if @samp{supported} field is not @samp{0}.
28833 @item stopping-tracepoint
28834 The number of tracepoint whose passcount as exceeded. This field is
28835 present iff the @samp{stop-reason} field has the value of
28839 @itemx frames-created
28840 The @samp{frames} field is a count of the total number of trace frames
28841 in the trace buffer, while @samp{frames-created} is the total created
28842 during the run, including ones that were discarded, such as when a
28843 circular trace buffer filled up. Both fields are optional.
28847 These fields tell the current size of the tracing buffer and the
28848 remaining space. These fields are optional.
28851 The value of the circular trace buffer flag. @code{1} means that the
28852 trace buffer is circular and old trace frames will be discarded if
28853 necessary to make room, @code{0} means that the trace buffer is linear
28857 The value of the disconnected tracing flag. @code{1} means that
28858 tracing will continue after @value{GDBN} disconnects, @code{0} means
28859 that the trace run will stop.
28863 @subsubheading @value{GDBN} Command
28865 The corresponding @value{GDBN} command is @samp{tstatus}.
28867 @subheading -trace-stop
28868 @findex -trace-stop
28870 @subsubheading Synopsis
28876 Stops a tracing experiment. The result of this command has the same
28877 fields as @code{-trace-status}, except that the @samp{supported} and
28878 @samp{running} fields are not output.
28880 @subsubheading @value{GDBN} Command
28882 The corresponding @value{GDBN} command is @samp{tstop}.
28885 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28886 @node GDB/MI Symbol Query
28887 @section @sc{gdb/mi} Symbol Query Commands
28891 @subheading The @code{-symbol-info-address} Command
28892 @findex -symbol-info-address
28894 @subsubheading Synopsis
28897 -symbol-info-address @var{symbol}
28900 Describe where @var{symbol} is stored.
28902 @subsubheading @value{GDBN} Command
28904 The corresponding @value{GDBN} command is @samp{info address}.
28906 @subsubheading Example
28910 @subheading The @code{-symbol-info-file} Command
28911 @findex -symbol-info-file
28913 @subsubheading Synopsis
28919 Show the file for the symbol.
28921 @subsubheading @value{GDBN} Command
28923 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28924 @samp{gdb_find_file}.
28926 @subsubheading Example
28930 @subheading The @code{-symbol-info-function} Command
28931 @findex -symbol-info-function
28933 @subsubheading Synopsis
28936 -symbol-info-function
28939 Show which function the symbol lives in.
28941 @subsubheading @value{GDBN} Command
28943 @samp{gdb_get_function} in @code{gdbtk}.
28945 @subsubheading Example
28949 @subheading The @code{-symbol-info-line} Command
28950 @findex -symbol-info-line
28952 @subsubheading Synopsis
28958 Show the core addresses of the code for a source line.
28960 @subsubheading @value{GDBN} Command
28962 The corresponding @value{GDBN} command is @samp{info line}.
28963 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28965 @subsubheading Example
28969 @subheading The @code{-symbol-info-symbol} Command
28970 @findex -symbol-info-symbol
28972 @subsubheading Synopsis
28975 -symbol-info-symbol @var{addr}
28978 Describe what symbol is at location @var{addr}.
28980 @subsubheading @value{GDBN} Command
28982 The corresponding @value{GDBN} command is @samp{info symbol}.
28984 @subsubheading Example
28988 @subheading The @code{-symbol-list-functions} Command
28989 @findex -symbol-list-functions
28991 @subsubheading Synopsis
28994 -symbol-list-functions
28997 List the functions in the executable.
28999 @subsubheading @value{GDBN} Command
29001 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29002 @samp{gdb_search} in @code{gdbtk}.
29004 @subsubheading Example
29009 @subheading The @code{-symbol-list-lines} Command
29010 @findex -symbol-list-lines
29012 @subsubheading Synopsis
29015 -symbol-list-lines @var{filename}
29018 Print the list of lines that contain code and their associated program
29019 addresses for the given source filename. The entries are sorted in
29020 ascending PC order.
29022 @subsubheading @value{GDBN} Command
29024 There is no corresponding @value{GDBN} command.
29026 @subsubheading Example
29029 -symbol-list-lines basics.c
29030 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29036 @subheading The @code{-symbol-list-types} Command
29037 @findex -symbol-list-types
29039 @subsubheading Synopsis
29045 List all the type names.
29047 @subsubheading @value{GDBN} Command
29049 The corresponding commands are @samp{info types} in @value{GDBN},
29050 @samp{gdb_search} in @code{gdbtk}.
29052 @subsubheading Example
29056 @subheading The @code{-symbol-list-variables} Command
29057 @findex -symbol-list-variables
29059 @subsubheading Synopsis
29062 -symbol-list-variables
29065 List all the global and static variable names.
29067 @subsubheading @value{GDBN} Command
29069 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29071 @subsubheading Example
29075 @subheading The @code{-symbol-locate} Command
29076 @findex -symbol-locate
29078 @subsubheading Synopsis
29084 @subsubheading @value{GDBN} Command
29086 @samp{gdb_loc} in @code{gdbtk}.
29088 @subsubheading Example
29092 @subheading The @code{-symbol-type} Command
29093 @findex -symbol-type
29095 @subsubheading Synopsis
29098 -symbol-type @var{variable}
29101 Show type of @var{variable}.
29103 @subsubheading @value{GDBN} Command
29105 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29106 @samp{gdb_obj_variable}.
29108 @subsubheading Example
29113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29114 @node GDB/MI File Commands
29115 @section @sc{gdb/mi} File Commands
29117 This section describes the GDB/MI commands to specify executable file names
29118 and to read in and obtain symbol table information.
29120 @subheading The @code{-file-exec-and-symbols} Command
29121 @findex -file-exec-and-symbols
29123 @subsubheading Synopsis
29126 -file-exec-and-symbols @var{file}
29129 Specify the executable file to be debugged. This file is the one from
29130 which the symbol table is also read. If no file is specified, the
29131 command clears the executable and symbol information. If breakpoints
29132 are set when using this command with no arguments, @value{GDBN} will produce
29133 error messages. Otherwise, no output is produced, except a completion
29136 @subsubheading @value{GDBN} Command
29138 The corresponding @value{GDBN} command is @samp{file}.
29140 @subsubheading Example
29144 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29150 @subheading The @code{-file-exec-file} Command
29151 @findex -file-exec-file
29153 @subsubheading Synopsis
29156 -file-exec-file @var{file}
29159 Specify the executable file to be debugged. Unlike
29160 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29161 from this file. If used without argument, @value{GDBN} clears the information
29162 about the executable file. No output is produced, except a completion
29165 @subsubheading @value{GDBN} Command
29167 The corresponding @value{GDBN} command is @samp{exec-file}.
29169 @subsubheading Example
29173 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29180 @subheading The @code{-file-list-exec-sections} Command
29181 @findex -file-list-exec-sections
29183 @subsubheading Synopsis
29186 -file-list-exec-sections
29189 List the sections of the current executable file.
29191 @subsubheading @value{GDBN} Command
29193 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29194 information as this command. @code{gdbtk} has a corresponding command
29195 @samp{gdb_load_info}.
29197 @subsubheading Example
29202 @subheading The @code{-file-list-exec-source-file} Command
29203 @findex -file-list-exec-source-file
29205 @subsubheading Synopsis
29208 -file-list-exec-source-file
29211 List the line number, the current source file, and the absolute path
29212 to the current source file for the current executable. The macro
29213 information field has a value of @samp{1} or @samp{0} depending on
29214 whether or not the file includes preprocessor macro information.
29216 @subsubheading @value{GDBN} Command
29218 The @value{GDBN} equivalent is @samp{info source}
29220 @subsubheading Example
29224 123-file-list-exec-source-file
29225 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29230 @subheading The @code{-file-list-exec-source-files} Command
29231 @findex -file-list-exec-source-files
29233 @subsubheading Synopsis
29236 -file-list-exec-source-files
29239 List the source files for the current executable.
29241 It will always output the filename, but only when @value{GDBN} can find
29242 the absolute file name of a source file, will it output the fullname.
29244 @subsubheading @value{GDBN} Command
29246 The @value{GDBN} equivalent is @samp{info sources}.
29247 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29249 @subsubheading Example
29252 -file-list-exec-source-files
29254 @{file=foo.c,fullname=/home/foo.c@},
29255 @{file=/home/bar.c,fullname=/home/bar.c@},
29256 @{file=gdb_could_not_find_fullpath.c@}]
29261 @subheading The @code{-file-list-shared-libraries} Command
29262 @findex -file-list-shared-libraries
29264 @subsubheading Synopsis
29267 -file-list-shared-libraries
29270 List the shared libraries in the program.
29272 @subsubheading @value{GDBN} Command
29274 The corresponding @value{GDBN} command is @samp{info shared}.
29276 @subsubheading Example
29280 @subheading The @code{-file-list-symbol-files} Command
29281 @findex -file-list-symbol-files
29283 @subsubheading Synopsis
29286 -file-list-symbol-files
29291 @subsubheading @value{GDBN} Command
29293 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29295 @subsubheading Example
29300 @subheading The @code{-file-symbol-file} Command
29301 @findex -file-symbol-file
29303 @subsubheading Synopsis
29306 -file-symbol-file @var{file}
29309 Read symbol table info from the specified @var{file} argument. When
29310 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29311 produced, except for a completion notification.
29313 @subsubheading @value{GDBN} Command
29315 The corresponding @value{GDBN} command is @samp{symbol-file}.
29317 @subsubheading Example
29321 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29327 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29328 @node GDB/MI Memory Overlay Commands
29329 @section @sc{gdb/mi} Memory Overlay Commands
29331 The memory overlay commands are not implemented.
29333 @c @subheading -overlay-auto
29335 @c @subheading -overlay-list-mapping-state
29337 @c @subheading -overlay-list-overlays
29339 @c @subheading -overlay-map
29341 @c @subheading -overlay-off
29343 @c @subheading -overlay-on
29345 @c @subheading -overlay-unmap
29347 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29348 @node GDB/MI Signal Handling Commands
29349 @section @sc{gdb/mi} Signal Handling Commands
29351 Signal handling commands are not implemented.
29353 @c @subheading -signal-handle
29355 @c @subheading -signal-list-handle-actions
29357 @c @subheading -signal-list-signal-types
29361 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29362 @node GDB/MI Target Manipulation
29363 @section @sc{gdb/mi} Target Manipulation Commands
29366 @subheading The @code{-target-attach} Command
29367 @findex -target-attach
29369 @subsubheading Synopsis
29372 -target-attach @var{pid} | @var{gid} | @var{file}
29375 Attach to a process @var{pid} or a file @var{file} outside of
29376 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29377 group, the id previously returned by
29378 @samp{-list-thread-groups --available} must be used.
29380 @subsubheading @value{GDBN} Command
29382 The corresponding @value{GDBN} command is @samp{attach}.
29384 @subsubheading Example
29388 =thread-created,id="1"
29389 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29395 @subheading The @code{-target-compare-sections} Command
29396 @findex -target-compare-sections
29398 @subsubheading Synopsis
29401 -target-compare-sections [ @var{section} ]
29404 Compare data of section @var{section} on target to the exec file.
29405 Without the argument, all sections are compared.
29407 @subsubheading @value{GDBN} Command
29409 The @value{GDBN} equivalent is @samp{compare-sections}.
29411 @subsubheading Example
29416 @subheading The @code{-target-detach} Command
29417 @findex -target-detach
29419 @subsubheading Synopsis
29422 -target-detach [ @var{pid} | @var{gid} ]
29425 Detach from the remote target which normally resumes its execution.
29426 If either @var{pid} or @var{gid} is specified, detaches from either
29427 the specified process, or specified thread group. There's no output.
29429 @subsubheading @value{GDBN} Command
29431 The corresponding @value{GDBN} command is @samp{detach}.
29433 @subsubheading Example
29443 @subheading The @code{-target-disconnect} Command
29444 @findex -target-disconnect
29446 @subsubheading Synopsis
29452 Disconnect from the remote target. There's no output and the target is
29453 generally not resumed.
29455 @subsubheading @value{GDBN} Command
29457 The corresponding @value{GDBN} command is @samp{disconnect}.
29459 @subsubheading Example
29469 @subheading The @code{-target-download} Command
29470 @findex -target-download
29472 @subsubheading Synopsis
29478 Loads the executable onto the remote target.
29479 It prints out an update message every half second, which includes the fields:
29483 The name of the section.
29485 The size of what has been sent so far for that section.
29487 The size of the section.
29489 The total size of what was sent so far (the current and the previous sections).
29491 The size of the overall executable to download.
29495 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29496 @sc{gdb/mi} Output Syntax}).
29498 In addition, it prints the name and size of the sections, as they are
29499 downloaded. These messages include the following fields:
29503 The name of the section.
29505 The size of the section.
29507 The size of the overall executable to download.
29511 At the end, a summary is printed.
29513 @subsubheading @value{GDBN} Command
29515 The corresponding @value{GDBN} command is @samp{load}.
29517 @subsubheading Example
29519 Note: each status message appears on a single line. Here the messages
29520 have been broken down so that they can fit onto a page.
29525 +download,@{section=".text",section-size="6668",total-size="9880"@}
29526 +download,@{section=".text",section-sent="512",section-size="6668",
29527 total-sent="512",total-size="9880"@}
29528 +download,@{section=".text",section-sent="1024",section-size="6668",
29529 total-sent="1024",total-size="9880"@}
29530 +download,@{section=".text",section-sent="1536",section-size="6668",
29531 total-sent="1536",total-size="9880"@}
29532 +download,@{section=".text",section-sent="2048",section-size="6668",
29533 total-sent="2048",total-size="9880"@}
29534 +download,@{section=".text",section-sent="2560",section-size="6668",
29535 total-sent="2560",total-size="9880"@}
29536 +download,@{section=".text",section-sent="3072",section-size="6668",
29537 total-sent="3072",total-size="9880"@}
29538 +download,@{section=".text",section-sent="3584",section-size="6668",
29539 total-sent="3584",total-size="9880"@}
29540 +download,@{section=".text",section-sent="4096",section-size="6668",
29541 total-sent="4096",total-size="9880"@}
29542 +download,@{section=".text",section-sent="4608",section-size="6668",
29543 total-sent="4608",total-size="9880"@}
29544 +download,@{section=".text",section-sent="5120",section-size="6668",
29545 total-sent="5120",total-size="9880"@}
29546 +download,@{section=".text",section-sent="5632",section-size="6668",
29547 total-sent="5632",total-size="9880"@}
29548 +download,@{section=".text",section-sent="6144",section-size="6668",
29549 total-sent="6144",total-size="9880"@}
29550 +download,@{section=".text",section-sent="6656",section-size="6668",
29551 total-sent="6656",total-size="9880"@}
29552 +download,@{section=".init",section-size="28",total-size="9880"@}
29553 +download,@{section=".fini",section-size="28",total-size="9880"@}
29554 +download,@{section=".data",section-size="3156",total-size="9880"@}
29555 +download,@{section=".data",section-sent="512",section-size="3156",
29556 total-sent="7236",total-size="9880"@}
29557 +download,@{section=".data",section-sent="1024",section-size="3156",
29558 total-sent="7748",total-size="9880"@}
29559 +download,@{section=".data",section-sent="1536",section-size="3156",
29560 total-sent="8260",total-size="9880"@}
29561 +download,@{section=".data",section-sent="2048",section-size="3156",
29562 total-sent="8772",total-size="9880"@}
29563 +download,@{section=".data",section-sent="2560",section-size="3156",
29564 total-sent="9284",total-size="9880"@}
29565 +download,@{section=".data",section-sent="3072",section-size="3156",
29566 total-sent="9796",total-size="9880"@}
29567 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29574 @subheading The @code{-target-exec-status} Command
29575 @findex -target-exec-status
29577 @subsubheading Synopsis
29580 -target-exec-status
29583 Provide information on the state of the target (whether it is running or
29584 not, for instance).
29586 @subsubheading @value{GDBN} Command
29588 There's no equivalent @value{GDBN} command.
29590 @subsubheading Example
29594 @subheading The @code{-target-list-available-targets} Command
29595 @findex -target-list-available-targets
29597 @subsubheading Synopsis
29600 -target-list-available-targets
29603 List the possible targets to connect to.
29605 @subsubheading @value{GDBN} Command
29607 The corresponding @value{GDBN} command is @samp{help target}.
29609 @subsubheading Example
29613 @subheading The @code{-target-list-current-targets} Command
29614 @findex -target-list-current-targets
29616 @subsubheading Synopsis
29619 -target-list-current-targets
29622 Describe the current target.
29624 @subsubheading @value{GDBN} Command
29626 The corresponding information is printed by @samp{info file} (among
29629 @subsubheading Example
29633 @subheading The @code{-target-list-parameters} Command
29634 @findex -target-list-parameters
29636 @subsubheading Synopsis
29639 -target-list-parameters
29645 @subsubheading @value{GDBN} Command
29649 @subsubheading Example
29653 @subheading The @code{-target-select} Command
29654 @findex -target-select
29656 @subsubheading Synopsis
29659 -target-select @var{type} @var{parameters @dots{}}
29662 Connect @value{GDBN} to the remote target. This command takes two args:
29666 The type of target, for instance @samp{remote}, etc.
29667 @item @var{parameters}
29668 Device names, host names and the like. @xref{Target Commands, ,
29669 Commands for Managing Targets}, for more details.
29672 The output is a connection notification, followed by the address at
29673 which the target program is, in the following form:
29676 ^connected,addr="@var{address}",func="@var{function name}",
29677 args=[@var{arg list}]
29680 @subsubheading @value{GDBN} Command
29682 The corresponding @value{GDBN} command is @samp{target}.
29684 @subsubheading Example
29688 -target-select remote /dev/ttya
29689 ^connected,addr="0xfe00a300",func="??",args=[]
29693 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29694 @node GDB/MI File Transfer Commands
29695 @section @sc{gdb/mi} File Transfer Commands
29698 @subheading The @code{-target-file-put} Command
29699 @findex -target-file-put
29701 @subsubheading Synopsis
29704 -target-file-put @var{hostfile} @var{targetfile}
29707 Copy file @var{hostfile} from the host system (the machine running
29708 @value{GDBN}) to @var{targetfile} on the target system.
29710 @subsubheading @value{GDBN} Command
29712 The corresponding @value{GDBN} command is @samp{remote put}.
29714 @subsubheading Example
29718 -target-file-put localfile remotefile
29724 @subheading The @code{-target-file-get} Command
29725 @findex -target-file-get
29727 @subsubheading Synopsis
29730 -target-file-get @var{targetfile} @var{hostfile}
29733 Copy file @var{targetfile} from the target system to @var{hostfile}
29734 on the host system.
29736 @subsubheading @value{GDBN} Command
29738 The corresponding @value{GDBN} command is @samp{remote get}.
29740 @subsubheading Example
29744 -target-file-get remotefile localfile
29750 @subheading The @code{-target-file-delete} Command
29751 @findex -target-file-delete
29753 @subsubheading Synopsis
29756 -target-file-delete @var{targetfile}
29759 Delete @var{targetfile} from the target system.
29761 @subsubheading @value{GDBN} Command
29763 The corresponding @value{GDBN} command is @samp{remote delete}.
29765 @subsubheading Example
29769 -target-file-delete remotefile
29775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29776 @node GDB/MI Miscellaneous Commands
29777 @section Miscellaneous @sc{gdb/mi} Commands
29779 @c @subheading -gdb-complete
29781 @subheading The @code{-gdb-exit} Command
29784 @subsubheading Synopsis
29790 Exit @value{GDBN} immediately.
29792 @subsubheading @value{GDBN} Command
29794 Approximately corresponds to @samp{quit}.
29796 @subsubheading Example
29806 @subheading The @code{-exec-abort} Command
29807 @findex -exec-abort
29809 @subsubheading Synopsis
29815 Kill the inferior running program.
29817 @subsubheading @value{GDBN} Command
29819 The corresponding @value{GDBN} command is @samp{kill}.
29821 @subsubheading Example
29826 @subheading The @code{-gdb-set} Command
29829 @subsubheading Synopsis
29835 Set an internal @value{GDBN} variable.
29836 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29838 @subsubheading @value{GDBN} Command
29840 The corresponding @value{GDBN} command is @samp{set}.
29842 @subsubheading Example
29852 @subheading The @code{-gdb-show} Command
29855 @subsubheading Synopsis
29861 Show the current value of a @value{GDBN} variable.
29863 @subsubheading @value{GDBN} Command
29865 The corresponding @value{GDBN} command is @samp{show}.
29867 @subsubheading Example
29876 @c @subheading -gdb-source
29879 @subheading The @code{-gdb-version} Command
29880 @findex -gdb-version
29882 @subsubheading Synopsis
29888 Show version information for @value{GDBN}. Used mostly in testing.
29890 @subsubheading @value{GDBN} Command
29892 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29893 default shows this information when you start an interactive session.
29895 @subsubheading Example
29897 @c This example modifies the actual output from GDB to avoid overfull
29903 ~Copyright 2000 Free Software Foundation, Inc.
29904 ~GDB is free software, covered by the GNU General Public License, and
29905 ~you are welcome to change it and/or distribute copies of it under
29906 ~ certain conditions.
29907 ~Type "show copying" to see the conditions.
29908 ~There is absolutely no warranty for GDB. Type "show warranty" for
29910 ~This GDB was configured as
29911 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29916 @subheading The @code{-list-features} Command
29917 @findex -list-features
29919 Returns a list of particular features of the MI protocol that
29920 this version of gdb implements. A feature can be a command,
29921 or a new field in an output of some command, or even an
29922 important bugfix. While a frontend can sometimes detect presence
29923 of a feature at runtime, it is easier to perform detection at debugger
29926 The command returns a list of strings, with each string naming an
29927 available feature. Each returned string is just a name, it does not
29928 have any internal structure. The list of possible feature names
29934 (gdb) -list-features
29935 ^done,result=["feature1","feature2"]
29938 The current list of features is:
29941 @item frozen-varobjs
29942 Indicates presence of the @code{-var-set-frozen} command, as well
29943 as possible presense of the @code{frozen} field in the output
29944 of @code{-varobj-create}.
29945 @item pending-breakpoints
29946 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29948 Indicates presence of Python scripting support, Python-based
29949 pretty-printing commands, and possible presence of the
29950 @samp{display_hint} field in the output of @code{-var-list-children}
29952 Indicates presence of the @code{-thread-info} command.
29953 @item data-read-memory-bytes
29954 Indicates presense of the @code{-data-read-memory-bytes} and the
29955 @code{-data-write-memory-bytes} commands.
29959 @subheading The @code{-list-target-features} Command
29960 @findex -list-target-features
29962 Returns a list of particular features that are supported by the
29963 target. Those features affect the permitted MI commands, but
29964 unlike the features reported by the @code{-list-features} command, the
29965 features depend on which target GDB is using at the moment. Whenever
29966 a target can change, due to commands such as @code{-target-select},
29967 @code{-target-attach} or @code{-exec-run}, the list of target features
29968 may change, and the frontend should obtain it again.
29972 (gdb) -list-features
29973 ^done,result=["async"]
29976 The current list of features is:
29980 Indicates that the target is capable of asynchronous command
29981 execution, which means that @value{GDBN} will accept further commands
29982 while the target is running.
29985 Indicates that the target is capable of reverse execution.
29986 @xref{Reverse Execution}, for more information.
29990 @subheading The @code{-list-thread-groups} Command
29991 @findex -list-thread-groups
29993 @subheading Synopsis
29996 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29999 Lists thread groups (@pxref{Thread groups}). When a single thread
30000 group is passed as the argument, lists the children of that group.
30001 When several thread group are passed, lists information about those
30002 thread groups. Without any parameters, lists information about all
30003 top-level thread groups.
30005 Normally, thread groups that are being debugged are reported.
30006 With the @samp{--available} option, @value{GDBN} reports thread groups
30007 available on the target.
30009 The output of this command may have either a @samp{threads} result or
30010 a @samp{groups} result. The @samp{thread} result has a list of tuples
30011 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30012 Information}). The @samp{groups} result has a list of tuples as value,
30013 each tuple describing a thread group. If top-level groups are
30014 requested (that is, no parameter is passed), or when several groups
30015 are passed, the output always has a @samp{groups} result. The format
30016 of the @samp{group} result is described below.
30018 To reduce the number of roundtrips it's possible to list thread groups
30019 together with their children, by passing the @samp{--recurse} option
30020 and the recursion depth. Presently, only recursion depth of 1 is
30021 permitted. If this option is present, then every reported thread group
30022 will also include its children, either as @samp{group} or
30023 @samp{threads} field.
30025 In general, any combination of option and parameters is permitted, with
30026 the following caveats:
30030 When a single thread group is passed, the output will typically
30031 be the @samp{threads} result. Because threads may not contain
30032 anything, the @samp{recurse} option will be ignored.
30035 When the @samp{--available} option is passed, limited information may
30036 be available. In particular, the list of threads of a process might
30037 be inaccessible. Further, specifying specific thread groups might
30038 not give any performance advantage over listing all thread groups.
30039 The frontend should assume that @samp{-list-thread-groups --available}
30040 is always an expensive operation and cache the results.
30044 The @samp{groups} result is a list of tuples, where each tuple may
30045 have the following fields:
30049 Identifier of the thread group. This field is always present.
30050 The identifier is an opaque string; frontends should not try to
30051 convert it to an integer, even though it might look like one.
30054 The type of the thread group. At present, only @samp{process} is a
30058 The target-specific process identifier. This field is only present
30059 for thread groups of type @samp{process} and only if the process exists.
30062 The number of children this thread group has. This field may be
30063 absent for an available thread group.
30066 This field has a list of tuples as value, each tuple describing a
30067 thread. It may be present if the @samp{--recurse} option is
30068 specified, and it's actually possible to obtain the threads.
30071 This field is a list of integers, each identifying a core that one
30072 thread of the group is running on. This field may be absent if
30073 such information is not available.
30076 The name of the executable file that corresponds to this thread group.
30077 The field is only present for thread groups of type @samp{process},
30078 and only if there is a corresponding executable file.
30082 @subheading Example
30086 -list-thread-groups
30087 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30088 -list-thread-groups 17
30089 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30090 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30091 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30092 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30093 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30094 -list-thread-groups --available
30095 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30096 -list-thread-groups --available --recurse 1
30097 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30098 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30099 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30100 -list-thread-groups --available --recurse 1 17 18
30101 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30102 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30103 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30107 @subheading The @code{-add-inferior} Command
30108 @findex -add-inferior
30110 @subheading Synopsis
30116 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30117 inferior is not associated with any executable. Such association may
30118 be established with the @samp{-file-exec-and-symbols} command
30119 (@pxref{GDB/MI File Commands}). The command response has a single
30120 field, @samp{thread-group}, whose value is the identifier of the
30121 thread group corresponding to the new inferior.
30123 @subheading Example
30128 ^done,thread-group="i3"
30131 @subheading The @code{-interpreter-exec} Command
30132 @findex -interpreter-exec
30134 @subheading Synopsis
30137 -interpreter-exec @var{interpreter} @var{command}
30139 @anchor{-interpreter-exec}
30141 Execute the specified @var{command} in the given @var{interpreter}.
30143 @subheading @value{GDBN} Command
30145 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30147 @subheading Example
30151 -interpreter-exec console "break main"
30152 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30153 &"During symbol reading, bad structure-type format.\n"
30154 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30159 @subheading The @code{-inferior-tty-set} Command
30160 @findex -inferior-tty-set
30162 @subheading Synopsis
30165 -inferior-tty-set /dev/pts/1
30168 Set terminal for future runs of the program being debugged.
30170 @subheading @value{GDBN} Command
30172 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30174 @subheading Example
30178 -inferior-tty-set /dev/pts/1
30183 @subheading The @code{-inferior-tty-show} Command
30184 @findex -inferior-tty-show
30186 @subheading Synopsis
30192 Show terminal for future runs of program being debugged.
30194 @subheading @value{GDBN} Command
30196 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30198 @subheading Example
30202 -inferior-tty-set /dev/pts/1
30206 ^done,inferior_tty_terminal="/dev/pts/1"
30210 @subheading The @code{-enable-timings} Command
30211 @findex -enable-timings
30213 @subheading Synopsis
30216 -enable-timings [yes | no]
30219 Toggle the printing of the wallclock, user and system times for an MI
30220 command as a field in its output. This command is to help frontend
30221 developers optimize the performance of their code. No argument is
30222 equivalent to @samp{yes}.
30224 @subheading @value{GDBN} Command
30228 @subheading Example
30236 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30237 addr="0x080484ed",func="main",file="myprog.c",
30238 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30239 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30247 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30248 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30249 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30250 fullname="/home/nickrob/myprog.c",line="73"@}
30255 @chapter @value{GDBN} Annotations
30257 This chapter describes annotations in @value{GDBN}. Annotations were
30258 designed to interface @value{GDBN} to graphical user interfaces or other
30259 similar programs which want to interact with @value{GDBN} at a
30260 relatively high level.
30262 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30266 This is Edition @value{EDITION}, @value{DATE}.
30270 * Annotations Overview:: What annotations are; the general syntax.
30271 * Server Prefix:: Issuing a command without affecting user state.
30272 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30273 * Errors:: Annotations for error messages.
30274 * Invalidation:: Some annotations describe things now invalid.
30275 * Annotations for Running::
30276 Whether the program is running, how it stopped, etc.
30277 * Source Annotations:: Annotations describing source code.
30280 @node Annotations Overview
30281 @section What is an Annotation?
30282 @cindex annotations
30284 Annotations start with a newline character, two @samp{control-z}
30285 characters, and the name of the annotation. If there is no additional
30286 information associated with this annotation, the name of the annotation
30287 is followed immediately by a newline. If there is additional
30288 information, the name of the annotation is followed by a space, the
30289 additional information, and a newline. The additional information
30290 cannot contain newline characters.
30292 Any output not beginning with a newline and two @samp{control-z}
30293 characters denotes literal output from @value{GDBN}. Currently there is
30294 no need for @value{GDBN} to output a newline followed by two
30295 @samp{control-z} characters, but if there was such a need, the
30296 annotations could be extended with an @samp{escape} annotation which
30297 means those three characters as output.
30299 The annotation @var{level}, which is specified using the
30300 @option{--annotate} command line option (@pxref{Mode Options}), controls
30301 how much information @value{GDBN} prints together with its prompt,
30302 values of expressions, source lines, and other types of output. Level 0
30303 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30304 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30305 for programs that control @value{GDBN}, and level 2 annotations have
30306 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30307 Interface, annotate, GDB's Obsolete Annotations}).
30310 @kindex set annotate
30311 @item set annotate @var{level}
30312 The @value{GDBN} command @code{set annotate} sets the level of
30313 annotations to the specified @var{level}.
30315 @item show annotate
30316 @kindex show annotate
30317 Show the current annotation level.
30320 This chapter describes level 3 annotations.
30322 A simple example of starting up @value{GDBN} with annotations is:
30325 $ @kbd{gdb --annotate=3}
30327 Copyright 2003 Free Software Foundation, Inc.
30328 GDB is free software, covered by the GNU General Public License,
30329 and you are welcome to change it and/or distribute copies of it
30330 under certain conditions.
30331 Type "show copying" to see the conditions.
30332 There is absolutely no warranty for GDB. Type "show warranty"
30334 This GDB was configured as "i386-pc-linux-gnu"
30345 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30346 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30347 denotes a @samp{control-z} character) are annotations; the rest is
30348 output from @value{GDBN}.
30350 @node Server Prefix
30351 @section The Server Prefix
30352 @cindex server prefix
30354 If you prefix a command with @samp{server } then it will not affect
30355 the command history, nor will it affect @value{GDBN}'s notion of which
30356 command to repeat if @key{RET} is pressed on a line by itself. This
30357 means that commands can be run behind a user's back by a front-end in
30358 a transparent manner.
30360 The @code{server } prefix does not affect the recording of values into
30361 the value history; to print a value without recording it into the
30362 value history, use the @code{output} command instead of the
30363 @code{print} command.
30365 Using this prefix also disables confirmation requests
30366 (@pxref{confirmation requests}).
30369 @section Annotation for @value{GDBN} Input
30371 @cindex annotations for prompts
30372 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30373 to know when to send output, when the output from a given command is
30376 Different kinds of input each have a different @dfn{input type}. Each
30377 input type has three annotations: a @code{pre-} annotation, which
30378 denotes the beginning of any prompt which is being output, a plain
30379 annotation, which denotes the end of the prompt, and then a @code{post-}
30380 annotation which denotes the end of any echo which may (or may not) be
30381 associated with the input. For example, the @code{prompt} input type
30382 features the following annotations:
30390 The input types are
30393 @findex pre-prompt annotation
30394 @findex prompt annotation
30395 @findex post-prompt annotation
30397 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30399 @findex pre-commands annotation
30400 @findex commands annotation
30401 @findex post-commands annotation
30403 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30404 command. The annotations are repeated for each command which is input.
30406 @findex pre-overload-choice annotation
30407 @findex overload-choice annotation
30408 @findex post-overload-choice annotation
30409 @item overload-choice
30410 When @value{GDBN} wants the user to select between various overloaded functions.
30412 @findex pre-query annotation
30413 @findex query annotation
30414 @findex post-query annotation
30416 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30418 @findex pre-prompt-for-continue annotation
30419 @findex prompt-for-continue annotation
30420 @findex post-prompt-for-continue annotation
30421 @item prompt-for-continue
30422 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30423 expect this to work well; instead use @code{set height 0} to disable
30424 prompting. This is because the counting of lines is buggy in the
30425 presence of annotations.
30430 @cindex annotations for errors, warnings and interrupts
30432 @findex quit annotation
30437 This annotation occurs right before @value{GDBN} responds to an interrupt.
30439 @findex error annotation
30444 This annotation occurs right before @value{GDBN} responds to an error.
30446 Quit and error annotations indicate that any annotations which @value{GDBN} was
30447 in the middle of may end abruptly. For example, if a
30448 @code{value-history-begin} annotation is followed by a @code{error}, one
30449 cannot expect to receive the matching @code{value-history-end}. One
30450 cannot expect not to receive it either, however; an error annotation
30451 does not necessarily mean that @value{GDBN} is immediately returning all the way
30454 @findex error-begin annotation
30455 A quit or error annotation may be preceded by
30461 Any output between that and the quit or error annotation is the error
30464 Warning messages are not yet annotated.
30465 @c If we want to change that, need to fix warning(), type_error(),
30466 @c range_error(), and possibly other places.
30469 @section Invalidation Notices
30471 @cindex annotations for invalidation messages
30472 The following annotations say that certain pieces of state may have
30476 @findex frames-invalid annotation
30477 @item ^Z^Zframes-invalid
30479 The frames (for example, output from the @code{backtrace} command) may
30482 @findex breakpoints-invalid annotation
30483 @item ^Z^Zbreakpoints-invalid
30485 The breakpoints may have changed. For example, the user just added or
30486 deleted a breakpoint.
30489 @node Annotations for Running
30490 @section Running the Program
30491 @cindex annotations for running programs
30493 @findex starting annotation
30494 @findex stopping annotation
30495 When the program starts executing due to a @value{GDBN} command such as
30496 @code{step} or @code{continue},
30502 is output. When the program stops,
30508 is output. Before the @code{stopped} annotation, a variety of
30509 annotations describe how the program stopped.
30512 @findex exited annotation
30513 @item ^Z^Zexited @var{exit-status}
30514 The program exited, and @var{exit-status} is the exit status (zero for
30515 successful exit, otherwise nonzero).
30517 @findex signalled annotation
30518 @findex signal-name annotation
30519 @findex signal-name-end annotation
30520 @findex signal-string annotation
30521 @findex signal-string-end annotation
30522 @item ^Z^Zsignalled
30523 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30524 annotation continues:
30530 ^Z^Zsignal-name-end
30534 ^Z^Zsignal-string-end
30539 where @var{name} is the name of the signal, such as @code{SIGILL} or
30540 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30541 as @code{Illegal Instruction} or @code{Segmentation fault}.
30542 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30543 user's benefit and have no particular format.
30545 @findex signal annotation
30547 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30548 just saying that the program received the signal, not that it was
30549 terminated with it.
30551 @findex breakpoint annotation
30552 @item ^Z^Zbreakpoint @var{number}
30553 The program hit breakpoint number @var{number}.
30555 @findex watchpoint annotation
30556 @item ^Z^Zwatchpoint @var{number}
30557 The program hit watchpoint number @var{number}.
30560 @node Source Annotations
30561 @section Displaying Source
30562 @cindex annotations for source display
30564 @findex source annotation
30565 The following annotation is used instead of displaying source code:
30568 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30571 where @var{filename} is an absolute file name indicating which source
30572 file, @var{line} is the line number within that file (where 1 is the
30573 first line in the file), @var{character} is the character position
30574 within the file (where 0 is the first character in the file) (for most
30575 debug formats this will necessarily point to the beginning of a line),
30576 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30577 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30578 @var{addr} is the address in the target program associated with the
30579 source which is being displayed. @var{addr} is in the form @samp{0x}
30580 followed by one or more lowercase hex digits (note that this does not
30581 depend on the language).
30583 @node JIT Interface
30584 @chapter JIT Compilation Interface
30585 @cindex just-in-time compilation
30586 @cindex JIT compilation interface
30588 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30589 interface. A JIT compiler is a program or library that generates native
30590 executable code at runtime and executes it, usually in order to achieve good
30591 performance while maintaining platform independence.
30593 Programs that use JIT compilation are normally difficult to debug because
30594 portions of their code are generated at runtime, instead of being loaded from
30595 object files, which is where @value{GDBN} normally finds the program's symbols
30596 and debug information. In order to debug programs that use JIT compilation,
30597 @value{GDBN} has an interface that allows the program to register in-memory
30598 symbol files with @value{GDBN} at runtime.
30600 If you are using @value{GDBN} to debug a program that uses this interface, then
30601 it should work transparently so long as you have not stripped the binary. If
30602 you are developing a JIT compiler, then the interface is documented in the rest
30603 of this chapter. At this time, the only known client of this interface is the
30606 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30607 JIT compiler communicates with @value{GDBN} by writing data into a global
30608 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30609 attaches, it reads a linked list of symbol files from the global variable to
30610 find existing code, and puts a breakpoint in the function so that it can find
30611 out about additional code.
30614 * Declarations:: Relevant C struct declarations
30615 * Registering Code:: Steps to register code
30616 * Unregistering Code:: Steps to unregister code
30620 @section JIT Declarations
30622 These are the relevant struct declarations that a C program should include to
30623 implement the interface:
30633 struct jit_code_entry
30635 struct jit_code_entry *next_entry;
30636 struct jit_code_entry *prev_entry;
30637 const char *symfile_addr;
30638 uint64_t symfile_size;
30641 struct jit_descriptor
30644 /* This type should be jit_actions_t, but we use uint32_t
30645 to be explicit about the bitwidth. */
30646 uint32_t action_flag;
30647 struct jit_code_entry *relevant_entry;
30648 struct jit_code_entry *first_entry;
30651 /* GDB puts a breakpoint in this function. */
30652 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30654 /* Make sure to specify the version statically, because the
30655 debugger may check the version before we can set it. */
30656 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30659 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30660 modifications to this global data properly, which can easily be done by putting
30661 a global mutex around modifications to these structures.
30663 @node Registering Code
30664 @section Registering Code
30666 To register code with @value{GDBN}, the JIT should follow this protocol:
30670 Generate an object file in memory with symbols and other desired debug
30671 information. The file must include the virtual addresses of the sections.
30674 Create a code entry for the file, which gives the start and size of the symbol
30678 Add it to the linked list in the JIT descriptor.
30681 Point the relevant_entry field of the descriptor at the entry.
30684 Set @code{action_flag} to @code{JIT_REGISTER} and call
30685 @code{__jit_debug_register_code}.
30688 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30689 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30690 new code. However, the linked list must still be maintained in order to allow
30691 @value{GDBN} to attach to a running process and still find the symbol files.
30693 @node Unregistering Code
30694 @section Unregistering Code
30696 If code is freed, then the JIT should use the following protocol:
30700 Remove the code entry corresponding to the code from the linked list.
30703 Point the @code{relevant_entry} field of the descriptor at the code entry.
30706 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30707 @code{__jit_debug_register_code}.
30710 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30711 and the JIT will leak the memory used for the associated symbol files.
30714 @chapter Reporting Bugs in @value{GDBN}
30715 @cindex bugs in @value{GDBN}
30716 @cindex reporting bugs in @value{GDBN}
30718 Your bug reports play an essential role in making @value{GDBN} reliable.
30720 Reporting a bug may help you by bringing a solution to your problem, or it
30721 may not. But in any case the principal function of a bug report is to help
30722 the entire community by making the next version of @value{GDBN} work better. Bug
30723 reports are your contribution to the maintenance of @value{GDBN}.
30725 In order for a bug report to serve its purpose, you must include the
30726 information that enables us to fix the bug.
30729 * Bug Criteria:: Have you found a bug?
30730 * Bug Reporting:: How to report bugs
30734 @section Have You Found a Bug?
30735 @cindex bug criteria
30737 If you are not sure whether you have found a bug, here are some guidelines:
30740 @cindex fatal signal
30741 @cindex debugger crash
30742 @cindex crash of debugger
30744 If the debugger gets a fatal signal, for any input whatever, that is a
30745 @value{GDBN} bug. Reliable debuggers never crash.
30747 @cindex error on valid input
30749 If @value{GDBN} produces an error message for valid input, that is a
30750 bug. (Note that if you're cross debugging, the problem may also be
30751 somewhere in the connection to the target.)
30753 @cindex invalid input
30755 If @value{GDBN} does not produce an error message for invalid input,
30756 that is a bug. However, you should note that your idea of
30757 ``invalid input'' might be our idea of ``an extension'' or ``support
30758 for traditional practice''.
30761 If you are an experienced user of debugging tools, your suggestions
30762 for improvement of @value{GDBN} are welcome in any case.
30765 @node Bug Reporting
30766 @section How to Report Bugs
30767 @cindex bug reports
30768 @cindex @value{GDBN} bugs, reporting
30770 A number of companies and individuals offer support for @sc{gnu} products.
30771 If you obtained @value{GDBN} from a support organization, we recommend you
30772 contact that organization first.
30774 You can find contact information for many support companies and
30775 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30777 @c should add a web page ref...
30780 @ifset BUGURL_DEFAULT
30781 In any event, we also recommend that you submit bug reports for
30782 @value{GDBN}. The preferred method is to submit them directly using
30783 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30784 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30787 @strong{Do not send bug reports to @samp{info-gdb}, or to
30788 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30789 not want to receive bug reports. Those that do have arranged to receive
30792 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30793 serves as a repeater. The mailing list and the newsgroup carry exactly
30794 the same messages. Often people think of posting bug reports to the
30795 newsgroup instead of mailing them. This appears to work, but it has one
30796 problem which can be crucial: a newsgroup posting often lacks a mail
30797 path back to the sender. Thus, if we need to ask for more information,
30798 we may be unable to reach you. For this reason, it is better to send
30799 bug reports to the mailing list.
30801 @ifclear BUGURL_DEFAULT
30802 In any event, we also recommend that you submit bug reports for
30803 @value{GDBN} to @value{BUGURL}.
30807 The fundamental principle of reporting bugs usefully is this:
30808 @strong{report all the facts}. If you are not sure whether to state a
30809 fact or leave it out, state it!
30811 Often people omit facts because they think they know what causes the
30812 problem and assume that some details do not matter. Thus, you might
30813 assume that the name of the variable you use in an example does not matter.
30814 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30815 stray memory reference which happens to fetch from the location where that
30816 name is stored in memory; perhaps, if the name were different, the contents
30817 of that location would fool the debugger into doing the right thing despite
30818 the bug. Play it safe and give a specific, complete example. That is the
30819 easiest thing for you to do, and the most helpful.
30821 Keep in mind that the purpose of a bug report is to enable us to fix the
30822 bug. It may be that the bug has been reported previously, but neither
30823 you nor we can know that unless your bug report is complete and
30826 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30827 bell?'' Those bug reports are useless, and we urge everyone to
30828 @emph{refuse to respond to them} except to chide the sender to report
30831 To enable us to fix the bug, you should include all these things:
30835 The version of @value{GDBN}. @value{GDBN} announces it if you start
30836 with no arguments; you can also print it at any time using @code{show
30839 Without this, we will not know whether there is any point in looking for
30840 the bug in the current version of @value{GDBN}.
30843 The type of machine you are using, and the operating system name and
30847 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30848 ``@value{GCC}--2.8.1''.
30851 What compiler (and its version) was used to compile the program you are
30852 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30853 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30854 to get this information; for other compilers, see the documentation for
30858 The command arguments you gave the compiler to compile your example and
30859 observe the bug. For example, did you use @samp{-O}? To guarantee
30860 you will not omit something important, list them all. A copy of the
30861 Makefile (or the output from make) is sufficient.
30863 If we were to try to guess the arguments, we would probably guess wrong
30864 and then we might not encounter the bug.
30867 A complete input script, and all necessary source files, that will
30871 A description of what behavior you observe that you believe is
30872 incorrect. For example, ``It gets a fatal signal.''
30874 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30875 will certainly notice it. But if the bug is incorrect output, we might
30876 not notice unless it is glaringly wrong. You might as well not give us
30877 a chance to make a mistake.
30879 Even if the problem you experience is a fatal signal, you should still
30880 say so explicitly. Suppose something strange is going on, such as, your
30881 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30882 the C library on your system. (This has happened!) Your copy might
30883 crash and ours would not. If you told us to expect a crash, then when
30884 ours fails to crash, we would know that the bug was not happening for
30885 us. If you had not told us to expect a crash, then we would not be able
30886 to draw any conclusion from our observations.
30889 @cindex recording a session script
30890 To collect all this information, you can use a session recording program
30891 such as @command{script}, which is available on many Unix systems.
30892 Just run your @value{GDBN} session inside @command{script} and then
30893 include the @file{typescript} file with your bug report.
30895 Another way to record a @value{GDBN} session is to run @value{GDBN}
30896 inside Emacs and then save the entire buffer to a file.
30899 If you wish to suggest changes to the @value{GDBN} source, send us context
30900 diffs. If you even discuss something in the @value{GDBN} source, refer to
30901 it by context, not by line number.
30903 The line numbers in our development sources will not match those in your
30904 sources. Your line numbers would convey no useful information to us.
30908 Here are some things that are not necessary:
30912 A description of the envelope of the bug.
30914 Often people who encounter a bug spend a lot of time investigating
30915 which changes to the input file will make the bug go away and which
30916 changes will not affect it.
30918 This is often time consuming and not very useful, because the way we
30919 will find the bug is by running a single example under the debugger
30920 with breakpoints, not by pure deduction from a series of examples.
30921 We recommend that you save your time for something else.
30923 Of course, if you can find a simpler example to report @emph{instead}
30924 of the original one, that is a convenience for us. Errors in the
30925 output will be easier to spot, running under the debugger will take
30926 less time, and so on.
30928 However, simplification is not vital; if you do not want to do this,
30929 report the bug anyway and send us the entire test case you used.
30932 A patch for the bug.
30934 A patch for the bug does help us if it is a good one. But do not omit
30935 the necessary information, such as the test case, on the assumption that
30936 a patch is all we need. We might see problems with your patch and decide
30937 to fix the problem another way, or we might not understand it at all.
30939 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30940 construct an example that will make the program follow a certain path
30941 through the code. If you do not send us the example, we will not be able
30942 to construct one, so we will not be able to verify that the bug is fixed.
30944 And if we cannot understand what bug you are trying to fix, or why your
30945 patch should be an improvement, we will not install it. A test case will
30946 help us to understand.
30949 A guess about what the bug is or what it depends on.
30951 Such guesses are usually wrong. Even we cannot guess right about such
30952 things without first using the debugger to find the facts.
30955 @c The readline documentation is distributed with the readline code
30956 @c and consists of the two following files:
30958 @c inc-hist.texinfo
30959 @c Use -I with makeinfo to point to the appropriate directory,
30960 @c environment var TEXINPUTS with TeX.
30961 @ifclear SYSTEM_READLINE
30962 @include rluser.texi
30963 @include inc-hist.texinfo
30967 @node Formatting Documentation
30968 @appendix Formatting Documentation
30970 @cindex @value{GDBN} reference card
30971 @cindex reference card
30972 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30973 for printing with PostScript or Ghostscript, in the @file{gdb}
30974 subdirectory of the main source directory@footnote{In
30975 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30976 release.}. If you can use PostScript or Ghostscript with your printer,
30977 you can print the reference card immediately with @file{refcard.ps}.
30979 The release also includes the source for the reference card. You
30980 can format it, using @TeX{}, by typing:
30986 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30987 mode on US ``letter'' size paper;
30988 that is, on a sheet 11 inches wide by 8.5 inches
30989 high. You will need to specify this form of printing as an option to
30990 your @sc{dvi} output program.
30992 @cindex documentation
30994 All the documentation for @value{GDBN} comes as part of the machine-readable
30995 distribution. The documentation is written in Texinfo format, which is
30996 a documentation system that uses a single source file to produce both
30997 on-line information and a printed manual. You can use one of the Info
30998 formatting commands to create the on-line version of the documentation
30999 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31001 @value{GDBN} includes an already formatted copy of the on-line Info
31002 version of this manual in the @file{gdb} subdirectory. The main Info
31003 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31004 subordinate files matching @samp{gdb.info*} in the same directory. If
31005 necessary, you can print out these files, or read them with any editor;
31006 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31007 Emacs or the standalone @code{info} program, available as part of the
31008 @sc{gnu} Texinfo distribution.
31010 If you want to format these Info files yourself, you need one of the
31011 Info formatting programs, such as @code{texinfo-format-buffer} or
31014 If you have @code{makeinfo} installed, and are in the top level
31015 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31016 version @value{GDBVN}), you can make the Info file by typing:
31023 If you want to typeset and print copies of this manual, you need @TeX{},
31024 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31025 Texinfo definitions file.
31027 @TeX{} is a typesetting program; it does not print files directly, but
31028 produces output files called @sc{dvi} files. To print a typeset
31029 document, you need a program to print @sc{dvi} files. If your system
31030 has @TeX{} installed, chances are it has such a program. The precise
31031 command to use depends on your system; @kbd{lpr -d} is common; another
31032 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31033 require a file name without any extension or a @samp{.dvi} extension.
31035 @TeX{} also requires a macro definitions file called
31036 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31037 written in Texinfo format. On its own, @TeX{} cannot either read or
31038 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31039 and is located in the @file{gdb-@var{version-number}/texinfo}
31042 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31043 typeset and print this manual. First switch to the @file{gdb}
31044 subdirectory of the main source directory (for example, to
31045 @file{gdb-@value{GDBVN}/gdb}) and type:
31051 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31053 @node Installing GDB
31054 @appendix Installing @value{GDBN}
31055 @cindex installation
31058 * Requirements:: Requirements for building @value{GDBN}
31059 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31060 * Separate Objdir:: Compiling @value{GDBN} in another directory
31061 * Config Names:: Specifying names for hosts and targets
31062 * Configure Options:: Summary of options for configure
31063 * System-wide configuration:: Having a system-wide init file
31067 @section Requirements for Building @value{GDBN}
31068 @cindex building @value{GDBN}, requirements for
31070 Building @value{GDBN} requires various tools and packages to be available.
31071 Other packages will be used only if they are found.
31073 @heading Tools/Packages Necessary for Building @value{GDBN}
31075 @item ISO C90 compiler
31076 @value{GDBN} is written in ISO C90. It should be buildable with any
31077 working C90 compiler, e.g.@: GCC.
31081 @heading Tools/Packages Optional for Building @value{GDBN}
31085 @value{GDBN} can use the Expat XML parsing library. This library may be
31086 included with your operating system distribution; if it is not, you
31087 can get the latest version from @url{http://expat.sourceforge.net}.
31088 The @file{configure} script will search for this library in several
31089 standard locations; if it is installed in an unusual path, you can
31090 use the @option{--with-libexpat-prefix} option to specify its location.
31096 Remote protocol memory maps (@pxref{Memory Map Format})
31098 Target descriptions (@pxref{Target Descriptions})
31100 Remote shared library lists (@pxref{Library List Format})
31102 MS-Windows shared libraries (@pxref{Shared Libraries})
31104 Traceframe info (@pxref{Traceframe Info Format})
31108 @cindex compressed debug sections
31109 @value{GDBN} will use the @samp{zlib} library, if available, to read
31110 compressed debug sections. Some linkers, such as GNU gold, are capable
31111 of producing binaries with compressed debug sections. If @value{GDBN}
31112 is compiled with @samp{zlib}, it will be able to read the debug
31113 information in such binaries.
31115 The @samp{zlib} library is likely included with your operating system
31116 distribution; if it is not, you can get the latest version from
31117 @url{http://zlib.net}.
31120 @value{GDBN}'s features related to character sets (@pxref{Character
31121 Sets}) require a functioning @code{iconv} implementation. If you are
31122 on a GNU system, then this is provided by the GNU C Library. Some
31123 other systems also provide a working @code{iconv}.
31125 On systems with @code{iconv}, you can install GNU Libiconv. If you
31126 have previously installed Libiconv, you can use the
31127 @option{--with-libiconv-prefix} option to configure.
31129 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31130 arrange to build Libiconv if a directory named @file{libiconv} appears
31131 in the top-most source directory. If Libiconv is built this way, and
31132 if the operating system does not provide a suitable @code{iconv}
31133 implementation, then the just-built library will automatically be used
31134 by @value{GDBN}. One easy way to set this up is to download GNU
31135 Libiconv, unpack it, and then rename the directory holding the
31136 Libiconv source code to @samp{libiconv}.
31139 @node Running Configure
31140 @section Invoking the @value{GDBN} @file{configure} Script
31141 @cindex configuring @value{GDBN}
31142 @value{GDBN} comes with a @file{configure} script that automates the process
31143 of preparing @value{GDBN} for installation; you can then use @code{make} to
31144 build the @code{gdb} program.
31146 @c irrelevant in info file; it's as current as the code it lives with.
31147 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31148 look at the @file{README} file in the sources; we may have improved the
31149 installation procedures since publishing this manual.}
31152 The @value{GDBN} distribution includes all the source code you need for
31153 @value{GDBN} in a single directory, whose name is usually composed by
31154 appending the version number to @samp{gdb}.
31156 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31157 @file{gdb-@value{GDBVN}} directory. That directory contains:
31160 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31161 script for configuring @value{GDBN} and all its supporting libraries
31163 @item gdb-@value{GDBVN}/gdb
31164 the source specific to @value{GDBN} itself
31166 @item gdb-@value{GDBVN}/bfd
31167 source for the Binary File Descriptor library
31169 @item gdb-@value{GDBVN}/include
31170 @sc{gnu} include files
31172 @item gdb-@value{GDBVN}/libiberty
31173 source for the @samp{-liberty} free software library
31175 @item gdb-@value{GDBVN}/opcodes
31176 source for the library of opcode tables and disassemblers
31178 @item gdb-@value{GDBVN}/readline
31179 source for the @sc{gnu} command-line interface
31181 @item gdb-@value{GDBVN}/glob
31182 source for the @sc{gnu} filename pattern-matching subroutine
31184 @item gdb-@value{GDBVN}/mmalloc
31185 source for the @sc{gnu} memory-mapped malloc package
31188 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31189 from the @file{gdb-@var{version-number}} source directory, which in
31190 this example is the @file{gdb-@value{GDBVN}} directory.
31192 First switch to the @file{gdb-@var{version-number}} source directory
31193 if you are not already in it; then run @file{configure}. Pass the
31194 identifier for the platform on which @value{GDBN} will run as an
31200 cd gdb-@value{GDBVN}
31201 ./configure @var{host}
31206 where @var{host} is an identifier such as @samp{sun4} or
31207 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31208 (You can often leave off @var{host}; @file{configure} tries to guess the
31209 correct value by examining your system.)
31211 Running @samp{configure @var{host}} and then running @code{make} builds the
31212 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31213 libraries, then @code{gdb} itself. The configured source files, and the
31214 binaries, are left in the corresponding source directories.
31217 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31218 system does not recognize this automatically when you run a different
31219 shell, you may need to run @code{sh} on it explicitly:
31222 sh configure @var{host}
31225 If you run @file{configure} from a directory that contains source
31226 directories for multiple libraries or programs, such as the
31227 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31229 creates configuration files for every directory level underneath (unless
31230 you tell it not to, with the @samp{--norecursion} option).
31232 You should run the @file{configure} script from the top directory in the
31233 source tree, the @file{gdb-@var{version-number}} directory. If you run
31234 @file{configure} from one of the subdirectories, you will configure only
31235 that subdirectory. That is usually not what you want. In particular,
31236 if you run the first @file{configure} from the @file{gdb} subdirectory
31237 of the @file{gdb-@var{version-number}} directory, you will omit the
31238 configuration of @file{bfd}, @file{readline}, and other sibling
31239 directories of the @file{gdb} subdirectory. This leads to build errors
31240 about missing include files such as @file{bfd/bfd.h}.
31242 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31243 However, you should make sure that the shell on your path (named by
31244 the @samp{SHELL} environment variable) is publicly readable. Remember
31245 that @value{GDBN} uses the shell to start your program---some systems refuse to
31246 let @value{GDBN} debug child processes whose programs are not readable.
31248 @node Separate Objdir
31249 @section Compiling @value{GDBN} in Another Directory
31251 If you want to run @value{GDBN} versions for several host or target machines,
31252 you need a different @code{gdb} compiled for each combination of
31253 host and target. @file{configure} is designed to make this easy by
31254 allowing you to generate each configuration in a separate subdirectory,
31255 rather than in the source directory. If your @code{make} program
31256 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31257 @code{make} in each of these directories builds the @code{gdb}
31258 program specified there.
31260 To build @code{gdb} in a separate directory, run @file{configure}
31261 with the @samp{--srcdir} option to specify where to find the source.
31262 (You also need to specify a path to find @file{configure}
31263 itself from your working directory. If the path to @file{configure}
31264 would be the same as the argument to @samp{--srcdir}, you can leave out
31265 the @samp{--srcdir} option; it is assumed.)
31267 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31268 separate directory for a Sun 4 like this:
31272 cd gdb-@value{GDBVN}
31275 ../gdb-@value{GDBVN}/configure sun4
31280 When @file{configure} builds a configuration using a remote source
31281 directory, it creates a tree for the binaries with the same structure
31282 (and using the same names) as the tree under the source directory. In
31283 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31284 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31285 @file{gdb-sun4/gdb}.
31287 Make sure that your path to the @file{configure} script has just one
31288 instance of @file{gdb} in it. If your path to @file{configure} looks
31289 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31290 one subdirectory of @value{GDBN}, not the whole package. This leads to
31291 build errors about missing include files such as @file{bfd/bfd.h}.
31293 One popular reason to build several @value{GDBN} configurations in separate
31294 directories is to configure @value{GDBN} for cross-compiling (where
31295 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31296 programs that run on another machine---the @dfn{target}).
31297 You specify a cross-debugging target by
31298 giving the @samp{--target=@var{target}} option to @file{configure}.
31300 When you run @code{make} to build a program or library, you must run
31301 it in a configured directory---whatever directory you were in when you
31302 called @file{configure} (or one of its subdirectories).
31304 The @code{Makefile} that @file{configure} generates in each source
31305 directory also runs recursively. If you type @code{make} in a source
31306 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31307 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31308 will build all the required libraries, and then build GDB.
31310 When you have multiple hosts or targets configured in separate
31311 directories, you can run @code{make} on them in parallel (for example,
31312 if they are NFS-mounted on each of the hosts); they will not interfere
31316 @section Specifying Names for Hosts and Targets
31318 The specifications used for hosts and targets in the @file{configure}
31319 script are based on a three-part naming scheme, but some short predefined
31320 aliases are also supported. The full naming scheme encodes three pieces
31321 of information in the following pattern:
31324 @var{architecture}-@var{vendor}-@var{os}
31327 For example, you can use the alias @code{sun4} as a @var{host} argument,
31328 or as the value for @var{target} in a @code{--target=@var{target}}
31329 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31331 The @file{configure} script accompanying @value{GDBN} does not provide
31332 any query facility to list all supported host and target names or
31333 aliases. @file{configure} calls the Bourne shell script
31334 @code{config.sub} to map abbreviations to full names; you can read the
31335 script, if you wish, or you can use it to test your guesses on
31336 abbreviations---for example:
31339 % sh config.sub i386-linux
31341 % sh config.sub alpha-linux
31342 alpha-unknown-linux-gnu
31343 % sh config.sub hp9k700
31345 % sh config.sub sun4
31346 sparc-sun-sunos4.1.1
31347 % sh config.sub sun3
31348 m68k-sun-sunos4.1.1
31349 % sh config.sub i986v
31350 Invalid configuration `i986v': machine `i986v' not recognized
31354 @code{config.sub} is also distributed in the @value{GDBN} source
31355 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31357 @node Configure Options
31358 @section @file{configure} Options
31360 Here is a summary of the @file{configure} options and arguments that
31361 are most often useful for building @value{GDBN}. @file{configure} also has
31362 several other options not listed here. @inforef{What Configure
31363 Does,,configure.info}, for a full explanation of @file{configure}.
31366 configure @r{[}--help@r{]}
31367 @r{[}--prefix=@var{dir}@r{]}
31368 @r{[}--exec-prefix=@var{dir}@r{]}
31369 @r{[}--srcdir=@var{dirname}@r{]}
31370 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31371 @r{[}--target=@var{target}@r{]}
31376 You may introduce options with a single @samp{-} rather than
31377 @samp{--} if you prefer; but you may abbreviate option names if you use
31382 Display a quick summary of how to invoke @file{configure}.
31384 @item --prefix=@var{dir}
31385 Configure the source to install programs and files under directory
31388 @item --exec-prefix=@var{dir}
31389 Configure the source to install programs under directory
31392 @c avoid splitting the warning from the explanation:
31394 @item --srcdir=@var{dirname}
31395 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31396 @code{make} that implements the @code{VPATH} feature.}@*
31397 Use this option to make configurations in directories separate from the
31398 @value{GDBN} source directories. Among other things, you can use this to
31399 build (or maintain) several configurations simultaneously, in separate
31400 directories. @file{configure} writes configuration-specific files in
31401 the current directory, but arranges for them to use the source in the
31402 directory @var{dirname}. @file{configure} creates directories under
31403 the working directory in parallel to the source directories below
31406 @item --norecursion
31407 Configure only the directory level where @file{configure} is executed; do not
31408 propagate configuration to subdirectories.
31410 @item --target=@var{target}
31411 Configure @value{GDBN} for cross-debugging programs running on the specified
31412 @var{target}. Without this option, @value{GDBN} is configured to debug
31413 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31415 There is no convenient way to generate a list of all available targets.
31417 @item @var{host} @dots{}
31418 Configure @value{GDBN} to run on the specified @var{host}.
31420 There is no convenient way to generate a list of all available hosts.
31423 There are many other options available as well, but they are generally
31424 needed for special purposes only.
31426 @node System-wide configuration
31427 @section System-wide configuration and settings
31428 @cindex system-wide init file
31430 @value{GDBN} can be configured to have a system-wide init file;
31431 this file will be read and executed at startup (@pxref{Startup, , What
31432 @value{GDBN} does during startup}).
31434 Here is the corresponding configure option:
31437 @item --with-system-gdbinit=@var{file}
31438 Specify that the default location of the system-wide init file is
31442 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31443 it may be subject to relocation. Two possible cases:
31447 If the default location of this init file contains @file{$prefix},
31448 it will be subject to relocation. Suppose that the configure options
31449 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31450 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31451 init file is looked for as @file{$install/etc/gdbinit} instead of
31452 @file{$prefix/etc/gdbinit}.
31455 By contrast, if the default location does not contain the prefix,
31456 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31457 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31458 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31459 wherever @value{GDBN} is installed.
31462 @node Maintenance Commands
31463 @appendix Maintenance Commands
31464 @cindex maintenance commands
31465 @cindex internal commands
31467 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31468 includes a number of commands intended for @value{GDBN} developers,
31469 that are not documented elsewhere in this manual. These commands are
31470 provided here for reference. (For commands that turn on debugging
31471 messages, see @ref{Debugging Output}.)
31474 @kindex maint agent
31475 @kindex maint agent-eval
31476 @item maint agent @var{expression}
31477 @itemx maint agent-eval @var{expression}
31478 Translate the given @var{expression} into remote agent bytecodes.
31479 This command is useful for debugging the Agent Expression mechanism
31480 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31481 expression useful for data collection, such as by tracepoints, while
31482 @samp{maint agent-eval} produces an expression that evaluates directly
31483 to a result. For instance, a collection expression for @code{globa +
31484 globb} will include bytecodes to record four bytes of memory at each
31485 of the addresses of @code{globa} and @code{globb}, while discarding
31486 the result of the addition, while an evaluation expression will do the
31487 addition and return the sum.
31489 @kindex maint info breakpoints
31490 @item @anchor{maint info breakpoints}maint info breakpoints
31491 Using the same format as @samp{info breakpoints}, display both the
31492 breakpoints you've set explicitly, and those @value{GDBN} is using for
31493 internal purposes. Internal breakpoints are shown with negative
31494 breakpoint numbers. The type column identifies what kind of breakpoint
31499 Normal, explicitly set breakpoint.
31502 Normal, explicitly set watchpoint.
31505 Internal breakpoint, used to handle correctly stepping through
31506 @code{longjmp} calls.
31508 @item longjmp resume
31509 Internal breakpoint at the target of a @code{longjmp}.
31512 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31515 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31518 Shared library events.
31522 @kindex set displaced-stepping
31523 @kindex show displaced-stepping
31524 @cindex displaced stepping support
31525 @cindex out-of-line single-stepping
31526 @item set displaced-stepping
31527 @itemx show displaced-stepping
31528 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31529 if the target supports it. Displaced stepping is a way to single-step
31530 over breakpoints without removing them from the inferior, by executing
31531 an out-of-line copy of the instruction that was originally at the
31532 breakpoint location. It is also known as out-of-line single-stepping.
31535 @item set displaced-stepping on
31536 If the target architecture supports it, @value{GDBN} will use
31537 displaced stepping to step over breakpoints.
31539 @item set displaced-stepping off
31540 @value{GDBN} will not use displaced stepping to step over breakpoints,
31541 even if such is supported by the target architecture.
31543 @cindex non-stop mode, and @samp{set displaced-stepping}
31544 @item set displaced-stepping auto
31545 This is the default mode. @value{GDBN} will use displaced stepping
31546 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31547 architecture supports displaced stepping.
31550 @kindex maint check-symtabs
31551 @item maint check-symtabs
31552 Check the consistency of psymtabs and symtabs.
31554 @kindex maint cplus first_component
31555 @item maint cplus first_component @var{name}
31556 Print the first C@t{++} class/namespace component of @var{name}.
31558 @kindex maint cplus namespace
31559 @item maint cplus namespace
31560 Print the list of possible C@t{++} namespaces.
31562 @kindex maint demangle
31563 @item maint demangle @var{name}
31564 Demangle a C@t{++} or Objective-C mangled @var{name}.
31566 @kindex maint deprecate
31567 @kindex maint undeprecate
31568 @cindex deprecated commands
31569 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31570 @itemx maint undeprecate @var{command}
31571 Deprecate or undeprecate the named @var{command}. Deprecated commands
31572 cause @value{GDBN} to issue a warning when you use them. The optional
31573 argument @var{replacement} says which newer command should be used in
31574 favor of the deprecated one; if it is given, @value{GDBN} will mention
31575 the replacement as part of the warning.
31577 @kindex maint dump-me
31578 @item maint dump-me
31579 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31580 Cause a fatal signal in the debugger and force it to dump its core.
31581 This is supported only on systems which support aborting a program
31582 with the @code{SIGQUIT} signal.
31584 @kindex maint internal-error
31585 @kindex maint internal-warning
31586 @item maint internal-error @r{[}@var{message-text}@r{]}
31587 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31588 Cause @value{GDBN} to call the internal function @code{internal_error}
31589 or @code{internal_warning} and hence behave as though an internal error
31590 or internal warning has been detected. In addition to reporting the
31591 internal problem, these functions give the user the opportunity to
31592 either quit @value{GDBN} or create a core file of the current
31593 @value{GDBN} session.
31595 These commands take an optional parameter @var{message-text} that is
31596 used as the text of the error or warning message.
31598 Here's an example of using @code{internal-error}:
31601 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31602 @dots{}/maint.c:121: internal-error: testing, 1, 2
31603 A problem internal to GDB has been detected. Further
31604 debugging may prove unreliable.
31605 Quit this debugging session? (y or n) @kbd{n}
31606 Create a core file? (y or n) @kbd{n}
31610 @cindex @value{GDBN} internal error
31611 @cindex internal errors, control of @value{GDBN} behavior
31613 @kindex maint set internal-error
31614 @kindex maint show internal-error
31615 @kindex maint set internal-warning
31616 @kindex maint show internal-warning
31617 @item maint set internal-error @var{action} [ask|yes|no]
31618 @itemx maint show internal-error @var{action}
31619 @itemx maint set internal-warning @var{action} [ask|yes|no]
31620 @itemx maint show internal-warning @var{action}
31621 When @value{GDBN} reports an internal problem (error or warning) it
31622 gives the user the opportunity to both quit @value{GDBN} and create a
31623 core file of the current @value{GDBN} session. These commands let you
31624 override the default behaviour for each particular @var{action},
31625 described in the table below.
31629 You can specify that @value{GDBN} should always (yes) or never (no)
31630 quit. The default is to ask the user what to do.
31633 You can specify that @value{GDBN} should always (yes) or never (no)
31634 create a core file. The default is to ask the user what to do.
31637 @kindex maint packet
31638 @item maint packet @var{text}
31639 If @value{GDBN} is talking to an inferior via the serial protocol,
31640 then this command sends the string @var{text} to the inferior, and
31641 displays the response packet. @value{GDBN} supplies the initial
31642 @samp{$} character, the terminating @samp{#} character, and the
31645 @kindex maint print architecture
31646 @item maint print architecture @r{[}@var{file}@r{]}
31647 Print the entire architecture configuration. The optional argument
31648 @var{file} names the file where the output goes.
31650 @kindex maint print c-tdesc
31651 @item maint print c-tdesc
31652 Print the current target description (@pxref{Target Descriptions}) as
31653 a C source file. The created source file can be used in @value{GDBN}
31654 when an XML parser is not available to parse the description.
31656 @kindex maint print dummy-frames
31657 @item maint print dummy-frames
31658 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31661 (@value{GDBP}) @kbd{b add}
31663 (@value{GDBP}) @kbd{print add(2,3)}
31664 Breakpoint 2, add (a=2, b=3) at @dots{}
31666 The program being debugged stopped while in a function called from GDB.
31668 (@value{GDBP}) @kbd{maint print dummy-frames}
31669 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31670 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31671 call_lo=0x01014000 call_hi=0x01014001
31675 Takes an optional file parameter.
31677 @kindex maint print registers
31678 @kindex maint print raw-registers
31679 @kindex maint print cooked-registers
31680 @kindex maint print register-groups
31681 @item maint print registers @r{[}@var{file}@r{]}
31682 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31683 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31684 @itemx maint print register-groups @r{[}@var{file}@r{]}
31685 Print @value{GDBN}'s internal register data structures.
31687 The command @code{maint print raw-registers} includes the contents of
31688 the raw register cache; the command @code{maint print cooked-registers}
31689 includes the (cooked) value of all registers, including registers which
31690 aren't available on the target nor visible to user; and the
31691 command @code{maint print register-groups} includes the groups that each
31692 register is a member of. @xref{Registers,, Registers, gdbint,
31693 @value{GDBN} Internals}.
31695 These commands take an optional parameter, a file name to which to
31696 write the information.
31698 @kindex maint print reggroups
31699 @item maint print reggroups @r{[}@var{file}@r{]}
31700 Print @value{GDBN}'s internal register group data structures. The
31701 optional argument @var{file} tells to what file to write the
31704 The register groups info looks like this:
31707 (@value{GDBP}) @kbd{maint print reggroups}
31720 This command forces @value{GDBN} to flush its internal register cache.
31722 @kindex maint print objfiles
31723 @cindex info for known object files
31724 @item maint print objfiles
31725 Print a dump of all known object files. For each object file, this
31726 command prints its name, address in memory, and all of its psymtabs
31729 @kindex maint print section-scripts
31730 @cindex info for known .debug_gdb_scripts-loaded scripts
31731 @item maint print section-scripts [@var{regexp}]
31732 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31733 If @var{regexp} is specified, only print scripts loaded by object files
31734 matching @var{regexp}.
31735 For each script, this command prints its name as specified in the objfile,
31736 and the full path if known.
31737 @xref{.debug_gdb_scripts section}.
31739 @kindex maint print statistics
31740 @cindex bcache statistics
31741 @item maint print statistics
31742 This command prints, for each object file in the program, various data
31743 about that object file followed by the byte cache (@dfn{bcache})
31744 statistics for the object file. The objfile data includes the number
31745 of minimal, partial, full, and stabs symbols, the number of types
31746 defined by the objfile, the number of as yet unexpanded psym tables,
31747 the number of line tables and string tables, and the amount of memory
31748 used by the various tables. The bcache statistics include the counts,
31749 sizes, and counts of duplicates of all and unique objects, max,
31750 average, and median entry size, total memory used and its overhead and
31751 savings, and various measures of the hash table size and chain
31754 @kindex maint print target-stack
31755 @cindex target stack description
31756 @item maint print target-stack
31757 A @dfn{target} is an interface between the debugger and a particular
31758 kind of file or process. Targets can be stacked in @dfn{strata},
31759 so that more than one target can potentially respond to a request.
31760 In particular, memory accesses will walk down the stack of targets
31761 until they find a target that is interested in handling that particular
31764 This command prints a short description of each layer that was pushed on
31765 the @dfn{target stack}, starting from the top layer down to the bottom one.
31767 @kindex maint print type
31768 @cindex type chain of a data type
31769 @item maint print type @var{expr}
31770 Print the type chain for a type specified by @var{expr}. The argument
31771 can be either a type name or a symbol. If it is a symbol, the type of
31772 that symbol is described. The type chain produced by this command is
31773 a recursive definition of the data type as stored in @value{GDBN}'s
31774 data structures, including its flags and contained types.
31776 @kindex maint set dwarf2 always-disassemble
31777 @kindex maint show dwarf2 always-disassemble
31778 @item maint set dwarf2 always-disassemble
31779 @item maint show dwarf2 always-disassemble
31780 Control the behavior of @code{info address} when using DWARF debugging
31783 The default is @code{off}, which means that @value{GDBN} should try to
31784 describe a variable's location in an easily readable format. When
31785 @code{on}, @value{GDBN} will instead display the DWARF location
31786 expression in an assembly-like format. Note that some locations are
31787 too complex for @value{GDBN} to describe simply; in this case you will
31788 always see the disassembly form.
31790 Here is an example of the resulting disassembly:
31793 (gdb) info addr argc
31794 Symbol "argc" is a complex DWARF expression:
31798 For more information on these expressions, see
31799 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31801 @kindex maint set dwarf2 max-cache-age
31802 @kindex maint show dwarf2 max-cache-age
31803 @item maint set dwarf2 max-cache-age
31804 @itemx maint show dwarf2 max-cache-age
31805 Control the DWARF 2 compilation unit cache.
31807 @cindex DWARF 2 compilation units cache
31808 In object files with inter-compilation-unit references, such as those
31809 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31810 reader needs to frequently refer to previously read compilation units.
31811 This setting controls how long a compilation unit will remain in the
31812 cache if it is not referenced. A higher limit means that cached
31813 compilation units will be stored in memory longer, and more total
31814 memory will be used. Setting it to zero disables caching, which will
31815 slow down @value{GDBN} startup, but reduce memory consumption.
31817 @kindex maint set profile
31818 @kindex maint show profile
31819 @cindex profiling GDB
31820 @item maint set profile
31821 @itemx maint show profile
31822 Control profiling of @value{GDBN}.
31824 Profiling will be disabled until you use the @samp{maint set profile}
31825 command to enable it. When you enable profiling, the system will begin
31826 collecting timing and execution count data; when you disable profiling or
31827 exit @value{GDBN}, the results will be written to a log file. Remember that
31828 if you use profiling, @value{GDBN} will overwrite the profiling log file
31829 (often called @file{gmon.out}). If you have a record of important profiling
31830 data in a @file{gmon.out} file, be sure to move it to a safe location.
31832 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31833 compiled with the @samp{-pg} compiler option.
31835 @kindex maint set show-debug-regs
31836 @kindex maint show show-debug-regs
31837 @cindex hardware debug registers
31838 @item maint set show-debug-regs
31839 @itemx maint show show-debug-regs
31840 Control whether to show variables that mirror the hardware debug
31841 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31842 enabled, the debug registers values are shown when @value{GDBN} inserts or
31843 removes a hardware breakpoint or watchpoint, and when the inferior
31844 triggers a hardware-assisted breakpoint or watchpoint.
31846 @kindex maint set show-all-tib
31847 @kindex maint show show-all-tib
31848 @item maint set show-all-tib
31849 @itemx maint show show-all-tib
31850 Control whether to show all non zero areas within a 1k block starting
31851 at thread local base, when using the @samp{info w32 thread-information-block}
31854 @kindex maint space
31855 @cindex memory used by commands
31857 Control whether to display memory usage for each command. If set to a
31858 nonzero value, @value{GDBN} will display how much memory each command
31859 took, following the command's own output. This can also be requested
31860 by invoking @value{GDBN} with the @option{--statistics} command-line
31861 switch (@pxref{Mode Options}).
31864 @cindex time of command execution
31866 Control whether to display the execution time for each command. If
31867 set to a nonzero value, @value{GDBN} will display how much time it
31868 took to execute each command, following the command's own output.
31869 The time is not printed for the commands that run the target, since
31870 there's no mechanism currently to compute how much time was spend
31871 by @value{GDBN} and how much time was spend by the program been debugged.
31872 it's not possibly currently
31873 This can also be requested by invoking @value{GDBN} with the
31874 @option{--statistics} command-line switch (@pxref{Mode Options}).
31876 @kindex maint translate-address
31877 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31878 Find the symbol stored at the location specified by the address
31879 @var{addr} and an optional section name @var{section}. If found,
31880 @value{GDBN} prints the name of the closest symbol and an offset from
31881 the symbol's location to the specified address. This is similar to
31882 the @code{info address} command (@pxref{Symbols}), except that this
31883 command also allows to find symbols in other sections.
31885 If section was not specified, the section in which the symbol was found
31886 is also printed. For dynamically linked executables, the name of
31887 executable or shared library containing the symbol is printed as well.
31891 The following command is useful for non-interactive invocations of
31892 @value{GDBN}, such as in the test suite.
31895 @item set watchdog @var{nsec}
31896 @kindex set watchdog
31897 @cindex watchdog timer
31898 @cindex timeout for commands
31899 Set the maximum number of seconds @value{GDBN} will wait for the
31900 target operation to finish. If this time expires, @value{GDBN}
31901 reports and error and the command is aborted.
31903 @item show watchdog
31904 Show the current setting of the target wait timeout.
31907 @node Remote Protocol
31908 @appendix @value{GDBN} Remote Serial Protocol
31913 * Stop Reply Packets::
31914 * General Query Packets::
31915 * Architecture-Specific Protocol Details::
31916 * Tracepoint Packets::
31917 * Host I/O Packets::
31919 * Notification Packets::
31920 * Remote Non-Stop::
31921 * Packet Acknowledgment::
31923 * File-I/O Remote Protocol Extension::
31924 * Library List Format::
31925 * Memory Map Format::
31926 * Thread List Format::
31927 * Traceframe Info Format::
31933 There may be occasions when you need to know something about the
31934 protocol---for example, if there is only one serial port to your target
31935 machine, you might want your program to do something special if it
31936 recognizes a packet meant for @value{GDBN}.
31938 In the examples below, @samp{->} and @samp{<-} are used to indicate
31939 transmitted and received data, respectively.
31941 @cindex protocol, @value{GDBN} remote serial
31942 @cindex serial protocol, @value{GDBN} remote
31943 @cindex remote serial protocol
31944 All @value{GDBN} commands and responses (other than acknowledgments
31945 and notifications, see @ref{Notification Packets}) are sent as a
31946 @var{packet}. A @var{packet} is introduced with the character
31947 @samp{$}, the actual @var{packet-data}, and the terminating character
31948 @samp{#} followed by a two-digit @var{checksum}:
31951 @code{$}@var{packet-data}@code{#}@var{checksum}
31955 @cindex checksum, for @value{GDBN} remote
31957 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31958 characters between the leading @samp{$} and the trailing @samp{#} (an
31959 eight bit unsigned checksum).
31961 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31962 specification also included an optional two-digit @var{sequence-id}:
31965 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31968 @cindex sequence-id, for @value{GDBN} remote
31970 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31971 has never output @var{sequence-id}s. Stubs that handle packets added
31972 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31974 When either the host or the target machine receives a packet, the first
31975 response expected is an acknowledgment: either @samp{+} (to indicate
31976 the package was received correctly) or @samp{-} (to request
31980 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31985 The @samp{+}/@samp{-} acknowledgments can be disabled
31986 once a connection is established.
31987 @xref{Packet Acknowledgment}, for details.
31989 The host (@value{GDBN}) sends @var{command}s, and the target (the
31990 debugging stub incorporated in your program) sends a @var{response}. In
31991 the case of step and continue @var{command}s, the response is only sent
31992 when the operation has completed, and the target has again stopped all
31993 threads in all attached processes. This is the default all-stop mode
31994 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31995 execution mode; see @ref{Remote Non-Stop}, for details.
31997 @var{packet-data} consists of a sequence of characters with the
31998 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32001 @cindex remote protocol, field separator
32002 Fields within the packet should be separated using @samp{,} @samp{;} or
32003 @samp{:}. Except where otherwise noted all numbers are represented in
32004 @sc{hex} with leading zeros suppressed.
32006 Implementors should note that prior to @value{GDBN} 5.0, the character
32007 @samp{:} could not appear as the third character in a packet (as it
32008 would potentially conflict with the @var{sequence-id}).
32010 @cindex remote protocol, binary data
32011 @anchor{Binary Data}
32012 Binary data in most packets is encoded either as two hexadecimal
32013 digits per byte of binary data. This allowed the traditional remote
32014 protocol to work over connections which were only seven-bit clean.
32015 Some packets designed more recently assume an eight-bit clean
32016 connection, and use a more efficient encoding to send and receive
32019 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32020 as an escape character. Any escaped byte is transmitted as the escape
32021 character followed by the original character XORed with @code{0x20}.
32022 For example, the byte @code{0x7d} would be transmitted as the two
32023 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32024 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32025 @samp{@}}) must always be escaped. Responses sent by the stub
32026 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32027 is not interpreted as the start of a run-length encoded sequence
32030 Response @var{data} can be run-length encoded to save space.
32031 Run-length encoding replaces runs of identical characters with one
32032 instance of the repeated character, followed by a @samp{*} and a
32033 repeat count. The repeat count is itself sent encoded, to avoid
32034 binary characters in @var{data}: a value of @var{n} is sent as
32035 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32036 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32037 code 32) for a repeat count of 3. (This is because run-length
32038 encoding starts to win for counts 3 or more.) Thus, for example,
32039 @samp{0* } is a run-length encoding of ``0000'': the space character
32040 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32043 The printable characters @samp{#} and @samp{$} or with a numeric value
32044 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32045 seven repeats (@samp{$}) can be expanded using a repeat count of only
32046 five (@samp{"}). For example, @samp{00000000} can be encoded as
32049 The error response returned for some packets includes a two character
32050 error number. That number is not well defined.
32052 @cindex empty response, for unsupported packets
32053 For any @var{command} not supported by the stub, an empty response
32054 (@samp{$#00}) should be returned. That way it is possible to extend the
32055 protocol. A newer @value{GDBN} can tell if a packet is supported based
32058 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
32059 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
32065 The following table provides a complete list of all currently defined
32066 @var{command}s and their corresponding response @var{data}.
32067 @xref{File-I/O Remote Protocol Extension}, for details about the File
32068 I/O extension of the remote protocol.
32070 Each packet's description has a template showing the packet's overall
32071 syntax, followed by an explanation of the packet's meaning. We
32072 include spaces in some of the templates for clarity; these are not
32073 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32074 separate its components. For example, a template like @samp{foo
32075 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32076 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32077 @var{baz}. @value{GDBN} does not transmit a space character between the
32078 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32081 @cindex @var{thread-id}, in remote protocol
32082 @anchor{thread-id syntax}
32083 Several packets and replies include a @var{thread-id} field to identify
32084 a thread. Normally these are positive numbers with a target-specific
32085 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32086 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32089 In addition, the remote protocol supports a multiprocess feature in
32090 which the @var{thread-id} syntax is extended to optionally include both
32091 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32092 The @var{pid} (process) and @var{tid} (thread) components each have the
32093 format described above: a positive number with target-specific
32094 interpretation formatted as a big-endian hex string, literal @samp{-1}
32095 to indicate all processes or threads (respectively), or @samp{0} to
32096 indicate an arbitrary process or thread. Specifying just a process, as
32097 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32098 error to specify all processes but a specific thread, such as
32099 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32100 for those packets and replies explicitly documented to include a process
32101 ID, rather than a @var{thread-id}.
32103 The multiprocess @var{thread-id} syntax extensions are only used if both
32104 @value{GDBN} and the stub report support for the @samp{multiprocess}
32105 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32108 Note that all packet forms beginning with an upper- or lower-case
32109 letter, other than those described here, are reserved for future use.
32111 Here are the packet descriptions.
32116 @cindex @samp{!} packet
32117 @anchor{extended mode}
32118 Enable extended mode. In extended mode, the remote server is made
32119 persistent. The @samp{R} packet is used to restart the program being
32125 The remote target both supports and has enabled extended mode.
32129 @cindex @samp{?} packet
32130 Indicate the reason the target halted. The reply is the same as for
32131 step and continue. This packet has a special interpretation when the
32132 target is in non-stop mode; see @ref{Remote Non-Stop}.
32135 @xref{Stop Reply Packets}, for the reply specifications.
32137 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32138 @cindex @samp{A} packet
32139 Initialized @code{argv[]} array passed into program. @var{arglen}
32140 specifies the number of bytes in the hex encoded byte stream
32141 @var{arg}. See @code{gdbserver} for more details.
32146 The arguments were set.
32152 @cindex @samp{b} packet
32153 (Don't use this packet; its behavior is not well-defined.)
32154 Change the serial line speed to @var{baud}.
32156 JTC: @emph{When does the transport layer state change? When it's
32157 received, or after the ACK is transmitted. In either case, there are
32158 problems if the command or the acknowledgment packet is dropped.}
32160 Stan: @emph{If people really wanted to add something like this, and get
32161 it working for the first time, they ought to modify ser-unix.c to send
32162 some kind of out-of-band message to a specially-setup stub and have the
32163 switch happen "in between" packets, so that from remote protocol's point
32164 of view, nothing actually happened.}
32166 @item B @var{addr},@var{mode}
32167 @cindex @samp{B} packet
32168 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32169 breakpoint at @var{addr}.
32171 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32172 (@pxref{insert breakpoint or watchpoint packet}).
32174 @cindex @samp{bc} packet
32177 Backward continue. Execute the target system in reverse. No parameter.
32178 @xref{Reverse Execution}, for more information.
32181 @xref{Stop Reply Packets}, for the reply specifications.
32183 @cindex @samp{bs} packet
32186 Backward single step. Execute one instruction in reverse. No parameter.
32187 @xref{Reverse Execution}, for more information.
32190 @xref{Stop Reply Packets}, for the reply specifications.
32192 @item c @r{[}@var{addr}@r{]}
32193 @cindex @samp{c} packet
32194 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32195 resume at current address.
32198 @xref{Stop Reply Packets}, for the reply specifications.
32200 @item C @var{sig}@r{[};@var{addr}@r{]}
32201 @cindex @samp{C} packet
32202 Continue with signal @var{sig} (hex signal number). If
32203 @samp{;@var{addr}} is omitted, resume at same address.
32206 @xref{Stop Reply Packets}, for the reply specifications.
32209 @cindex @samp{d} packet
32212 Don't use this packet; instead, define a general set packet
32213 (@pxref{General Query Packets}).
32217 @cindex @samp{D} packet
32218 The first form of the packet is used to detach @value{GDBN} from the
32219 remote system. It is sent to the remote target
32220 before @value{GDBN} disconnects via the @code{detach} command.
32222 The second form, including a process ID, is used when multiprocess
32223 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32224 detach only a specific process. The @var{pid} is specified as a
32225 big-endian hex string.
32235 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32236 @cindex @samp{F} packet
32237 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32238 This is part of the File-I/O protocol extension. @xref{File-I/O
32239 Remote Protocol Extension}, for the specification.
32242 @anchor{read registers packet}
32243 @cindex @samp{g} packet
32244 Read general registers.
32248 @item @var{XX@dots{}}
32249 Each byte of register data is described by two hex digits. The bytes
32250 with the register are transmitted in target byte order. The size of
32251 each register and their position within the @samp{g} packet are
32252 determined by the @value{GDBN} internal gdbarch functions
32253 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32254 specification of several standard @samp{g} packets is specified below.
32256 When reading registers from a trace frame (@pxref{Analyze Collected
32257 Data,,Using the Collected Data}), the stub may also return a string of
32258 literal @samp{x}'s in place of the register data digits, to indicate
32259 that the corresponding register has not been collected, thus its value
32260 is unavailable. For example, for an architecture with 4 registers of
32261 4 bytes each, the following reply indicates to @value{GDBN} that
32262 registers 0 and 2 have not been collected, while registers 1 and 3
32263 have been collected, and both have zero value:
32267 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32274 @item G @var{XX@dots{}}
32275 @cindex @samp{G} packet
32276 Write general registers. @xref{read registers packet}, for a
32277 description of the @var{XX@dots{}} data.
32287 @item H @var{c} @var{thread-id}
32288 @cindex @samp{H} packet
32289 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32290 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
32291 should be @samp{c} for step and continue operations, @samp{g} for other
32292 operations. The thread designator @var{thread-id} has the format and
32293 interpretation described in @ref{thread-id syntax}.
32304 @c 'H': How restrictive (or permissive) is the thread model. If a
32305 @c thread is selected and stopped, are other threads allowed
32306 @c to continue to execute? As I mentioned above, I think the
32307 @c semantics of each command when a thread is selected must be
32308 @c described. For example:
32310 @c 'g': If the stub supports threads and a specific thread is
32311 @c selected, returns the register block from that thread;
32312 @c otherwise returns current registers.
32314 @c 'G' If the stub supports threads and a specific thread is
32315 @c selected, sets the registers of the register block of
32316 @c that thread; otherwise sets current registers.
32318 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32319 @anchor{cycle step packet}
32320 @cindex @samp{i} packet
32321 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32322 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32323 step starting at that address.
32326 @cindex @samp{I} packet
32327 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32331 @cindex @samp{k} packet
32334 FIXME: @emph{There is no description of how to operate when a specific
32335 thread context has been selected (i.e.@: does 'k' kill only that
32338 @item m @var{addr},@var{length}
32339 @cindex @samp{m} packet
32340 Read @var{length} bytes of memory starting at address @var{addr}.
32341 Note that @var{addr} may not be aligned to any particular boundary.
32343 The stub need not use any particular size or alignment when gathering
32344 data from memory for the response; even if @var{addr} is word-aligned
32345 and @var{length} is a multiple of the word size, the stub is free to
32346 use byte accesses, or not. For this reason, this packet may not be
32347 suitable for accessing memory-mapped I/O devices.
32348 @cindex alignment of remote memory accesses
32349 @cindex size of remote memory accesses
32350 @cindex memory, alignment and size of remote accesses
32354 @item @var{XX@dots{}}
32355 Memory contents; each byte is transmitted as a two-digit hexadecimal
32356 number. The reply may contain fewer bytes than requested if the
32357 server was able to read only part of the region of memory.
32362 @item M @var{addr},@var{length}:@var{XX@dots{}}
32363 @cindex @samp{M} packet
32364 Write @var{length} bytes of memory starting at address @var{addr}.
32365 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32366 hexadecimal number.
32373 for an error (this includes the case where only part of the data was
32378 @cindex @samp{p} packet
32379 Read the value of register @var{n}; @var{n} is in hex.
32380 @xref{read registers packet}, for a description of how the returned
32381 register value is encoded.
32385 @item @var{XX@dots{}}
32386 the register's value
32390 Indicating an unrecognized @var{query}.
32393 @item P @var{n@dots{}}=@var{r@dots{}}
32394 @anchor{write register packet}
32395 @cindex @samp{P} packet
32396 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32397 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32398 digits for each byte in the register (target byte order).
32408 @item q @var{name} @var{params}@dots{}
32409 @itemx Q @var{name} @var{params}@dots{}
32410 @cindex @samp{q} packet
32411 @cindex @samp{Q} packet
32412 General query (@samp{q}) and set (@samp{Q}). These packets are
32413 described fully in @ref{General Query Packets}.
32416 @cindex @samp{r} packet
32417 Reset the entire system.
32419 Don't use this packet; use the @samp{R} packet instead.
32422 @cindex @samp{R} packet
32423 Restart the program being debugged. @var{XX}, while needed, is ignored.
32424 This packet is only available in extended mode (@pxref{extended mode}).
32426 The @samp{R} packet has no reply.
32428 @item s @r{[}@var{addr}@r{]}
32429 @cindex @samp{s} packet
32430 Single step. @var{addr} is the address at which to resume. If
32431 @var{addr} is omitted, resume at same address.
32434 @xref{Stop Reply Packets}, for the reply specifications.
32436 @item S @var{sig}@r{[};@var{addr}@r{]}
32437 @anchor{step with signal packet}
32438 @cindex @samp{S} packet
32439 Step with signal. This is analogous to the @samp{C} packet, but
32440 requests a single-step, rather than a normal resumption of execution.
32443 @xref{Stop Reply Packets}, for the reply specifications.
32445 @item t @var{addr}:@var{PP},@var{MM}
32446 @cindex @samp{t} packet
32447 Search backwards starting at address @var{addr} for a match with pattern
32448 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32449 @var{addr} must be at least 3 digits.
32451 @item T @var{thread-id}
32452 @cindex @samp{T} packet
32453 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32458 thread is still alive
32464 Packets starting with @samp{v} are identified by a multi-letter name,
32465 up to the first @samp{;} or @samp{?} (or the end of the packet).
32467 @item vAttach;@var{pid}
32468 @cindex @samp{vAttach} packet
32469 Attach to a new process with the specified process ID @var{pid}.
32470 The process ID is a
32471 hexadecimal integer identifying the process. In all-stop mode, all
32472 threads in the attached process are stopped; in non-stop mode, it may be
32473 attached without being stopped if that is supported by the target.
32475 @c In non-stop mode, on a successful vAttach, the stub should set the
32476 @c current thread to a thread of the newly-attached process. After
32477 @c attaching, GDB queries for the attached process's thread ID with qC.
32478 @c Also note that, from a user perspective, whether or not the
32479 @c target is stopped on attach in non-stop mode depends on whether you
32480 @c use the foreground or background version of the attach command, not
32481 @c on what vAttach does; GDB does the right thing with respect to either
32482 @c stopping or restarting threads.
32484 This packet is only available in extended mode (@pxref{extended mode}).
32490 @item @r{Any stop packet}
32491 for success in all-stop mode (@pxref{Stop Reply Packets})
32493 for success in non-stop mode (@pxref{Remote Non-Stop})
32496 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32497 @cindex @samp{vCont} packet
32498 Resume the inferior, specifying different actions for each thread.
32499 If an action is specified with no @var{thread-id}, then it is applied to any
32500 threads that don't have a specific action specified; if no default action is
32501 specified then other threads should remain stopped in all-stop mode and
32502 in their current state in non-stop mode.
32503 Specifying multiple
32504 default actions is an error; specifying no actions is also an error.
32505 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32507 Currently supported actions are:
32513 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32517 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32522 The optional argument @var{addr} normally associated with the
32523 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32524 not supported in @samp{vCont}.
32526 The @samp{t} action is only relevant in non-stop mode
32527 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32528 A stop reply should be generated for any affected thread not already stopped.
32529 When a thread is stopped by means of a @samp{t} action,
32530 the corresponding stop reply should indicate that the thread has stopped with
32531 signal @samp{0}, regardless of whether the target uses some other signal
32532 as an implementation detail.
32535 @xref{Stop Reply Packets}, for the reply specifications.
32538 @cindex @samp{vCont?} packet
32539 Request a list of actions supported by the @samp{vCont} packet.
32543 @item vCont@r{[};@var{action}@dots{}@r{]}
32544 The @samp{vCont} packet is supported. Each @var{action} is a supported
32545 command in the @samp{vCont} packet.
32547 The @samp{vCont} packet is not supported.
32550 @item vFile:@var{operation}:@var{parameter}@dots{}
32551 @cindex @samp{vFile} packet
32552 Perform a file operation on the target system. For details,
32553 see @ref{Host I/O Packets}.
32555 @item vFlashErase:@var{addr},@var{length}
32556 @cindex @samp{vFlashErase} packet
32557 Direct the stub to erase @var{length} bytes of flash starting at
32558 @var{addr}. The region may enclose any number of flash blocks, but
32559 its start and end must fall on block boundaries, as indicated by the
32560 flash block size appearing in the memory map (@pxref{Memory Map
32561 Format}). @value{GDBN} groups flash memory programming operations
32562 together, and sends a @samp{vFlashDone} request after each group; the
32563 stub is allowed to delay erase operation until the @samp{vFlashDone}
32564 packet is received.
32566 The stub must support @samp{vCont} if it reports support for
32567 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32568 this case @samp{vCont} actions can be specified to apply to all threads
32569 in a process by using the @samp{p@var{pid}.-1} form of the
32580 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32581 @cindex @samp{vFlashWrite} packet
32582 Direct the stub to write data to flash address @var{addr}. The data
32583 is passed in binary form using the same encoding as for the @samp{X}
32584 packet (@pxref{Binary Data}). The memory ranges specified by
32585 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32586 not overlap, and must appear in order of increasing addresses
32587 (although @samp{vFlashErase} packets for higher addresses may already
32588 have been received; the ordering is guaranteed only between
32589 @samp{vFlashWrite} packets). If a packet writes to an address that was
32590 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32591 target-specific method, the results are unpredictable.
32599 for vFlashWrite addressing non-flash memory
32605 @cindex @samp{vFlashDone} packet
32606 Indicate to the stub that flash programming operation is finished.
32607 The stub is permitted to delay or batch the effects of a group of
32608 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32609 @samp{vFlashDone} packet is received. The contents of the affected
32610 regions of flash memory are unpredictable until the @samp{vFlashDone}
32611 request is completed.
32613 @item vKill;@var{pid}
32614 @cindex @samp{vKill} packet
32615 Kill the process with the specified process ID. @var{pid} is a
32616 hexadecimal integer identifying the process. This packet is used in
32617 preference to @samp{k} when multiprocess protocol extensions are
32618 supported; see @ref{multiprocess extensions}.
32628 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32629 @cindex @samp{vRun} packet
32630 Run the program @var{filename}, passing it each @var{argument} on its
32631 command line. The file and arguments are hex-encoded strings. If
32632 @var{filename} is an empty string, the stub may use a default program
32633 (e.g.@: the last program run). The program is created in the stopped
32636 @c FIXME: What about non-stop mode?
32638 This packet is only available in extended mode (@pxref{extended mode}).
32644 @item @r{Any stop packet}
32645 for success (@pxref{Stop Reply Packets})
32649 @anchor{vStopped packet}
32650 @cindex @samp{vStopped} packet
32652 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32653 reply and prompt for the stub to report another one.
32657 @item @r{Any stop packet}
32658 if there is another unreported stop event (@pxref{Stop Reply Packets})
32660 if there are no unreported stop events
32663 @item X @var{addr},@var{length}:@var{XX@dots{}}
32665 @cindex @samp{X} packet
32666 Write data to memory, where the data is transmitted in binary.
32667 @var{addr} is address, @var{length} is number of bytes,
32668 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32678 @item z @var{type},@var{addr},@var{kind}
32679 @itemx Z @var{type},@var{addr},@var{kind}
32680 @anchor{insert breakpoint or watchpoint packet}
32681 @cindex @samp{z} packet
32682 @cindex @samp{Z} packets
32683 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32684 watchpoint starting at address @var{address} of kind @var{kind}.
32686 Each breakpoint and watchpoint packet @var{type} is documented
32689 @emph{Implementation notes: A remote target shall return an empty string
32690 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32691 remote target shall support either both or neither of a given
32692 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32693 avoid potential problems with duplicate packets, the operations should
32694 be implemented in an idempotent way.}
32696 @item z0,@var{addr},@var{kind}
32697 @itemx Z0,@var{addr},@var{kind}
32698 @cindex @samp{z0} packet
32699 @cindex @samp{Z0} packet
32700 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32701 @var{addr} of type @var{kind}.
32703 A memory breakpoint is implemented by replacing the instruction at
32704 @var{addr} with a software breakpoint or trap instruction. The
32705 @var{kind} is target-specific and typically indicates the size of
32706 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32707 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32708 architectures have additional meanings for @var{kind};
32709 see @ref{Architecture-Specific Protocol Details}.
32711 @emph{Implementation note: It is possible for a target to copy or move
32712 code that contains memory breakpoints (e.g., when implementing
32713 overlays). The behavior of this packet, in the presence of such a
32714 target, is not defined.}
32726 @item z1,@var{addr},@var{kind}
32727 @itemx Z1,@var{addr},@var{kind}
32728 @cindex @samp{z1} packet
32729 @cindex @samp{Z1} packet
32730 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32731 address @var{addr}.
32733 A hardware breakpoint is implemented using a mechanism that is not
32734 dependant on being able to modify the target's memory. @var{kind}
32735 has the same meaning as in @samp{Z0} packets.
32737 @emph{Implementation note: A hardware breakpoint is not affected by code
32750 @item z2,@var{addr},@var{kind}
32751 @itemx Z2,@var{addr},@var{kind}
32752 @cindex @samp{z2} packet
32753 @cindex @samp{Z2} packet
32754 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32755 @var{kind} is interpreted as the number of bytes to watch.
32767 @item z3,@var{addr},@var{kind}
32768 @itemx Z3,@var{addr},@var{kind}
32769 @cindex @samp{z3} packet
32770 @cindex @samp{Z3} packet
32771 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32772 @var{kind} is interpreted as the number of bytes to watch.
32784 @item z4,@var{addr},@var{kind}
32785 @itemx Z4,@var{addr},@var{kind}
32786 @cindex @samp{z4} packet
32787 @cindex @samp{Z4} packet
32788 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32789 @var{kind} is interpreted as the number of bytes to watch.
32803 @node Stop Reply Packets
32804 @section Stop Reply Packets
32805 @cindex stop reply packets
32807 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32808 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32809 receive any of the below as a reply. Except for @samp{?}
32810 and @samp{vStopped}, that reply is only returned
32811 when the target halts. In the below the exact meaning of @dfn{signal
32812 number} is defined by the header @file{include/gdb/signals.h} in the
32813 @value{GDBN} source code.
32815 As in the description of request packets, we include spaces in the
32816 reply templates for clarity; these are not part of the reply packet's
32817 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32823 The program received signal number @var{AA} (a two-digit hexadecimal
32824 number). This is equivalent to a @samp{T} response with no
32825 @var{n}:@var{r} pairs.
32827 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32828 @cindex @samp{T} packet reply
32829 The program received signal number @var{AA} (a two-digit hexadecimal
32830 number). This is equivalent to an @samp{S} response, except that the
32831 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32832 and other information directly in the stop reply packet, reducing
32833 round-trip latency. Single-step and breakpoint traps are reported
32834 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32838 If @var{n} is a hexadecimal number, it is a register number, and the
32839 corresponding @var{r} gives that register's value. @var{r} is a
32840 series of bytes in target byte order, with each byte given by a
32841 two-digit hex number.
32844 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32845 the stopped thread, as specified in @ref{thread-id syntax}.
32848 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32849 the core on which the stop event was detected.
32852 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32853 specific event that stopped the target. The currently defined stop
32854 reasons are listed below. @var{aa} should be @samp{05}, the trap
32855 signal. At most one stop reason should be present.
32858 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32859 and go on to the next; this allows us to extend the protocol in the
32863 The currently defined stop reasons are:
32869 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32872 @cindex shared library events, remote reply
32874 The packet indicates that the loaded libraries have changed.
32875 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32876 list of loaded libraries. @var{r} is ignored.
32878 @cindex replay log events, remote reply
32880 The packet indicates that the target cannot continue replaying
32881 logged execution events, because it has reached the end (or the
32882 beginning when executing backward) of the log. The value of @var{r}
32883 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32884 for more information.
32888 @itemx W @var{AA} ; process:@var{pid}
32889 The process exited, and @var{AA} is the exit status. This is only
32890 applicable to certain targets.
32892 The second form of the response, including the process ID of the exited
32893 process, can be used only when @value{GDBN} has reported support for
32894 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32895 The @var{pid} is formatted as a big-endian hex string.
32898 @itemx X @var{AA} ; process:@var{pid}
32899 The process terminated with signal @var{AA}.
32901 The second form of the response, including the process ID of the
32902 terminated process, can be used only when @value{GDBN} has reported
32903 support for multiprocess protocol extensions; see @ref{multiprocess
32904 extensions}. The @var{pid} is formatted as a big-endian hex string.
32906 @item O @var{XX}@dots{}
32907 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32908 written as the program's console output. This can happen at any time
32909 while the program is running and the debugger should continue to wait
32910 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32912 @item F @var{call-id},@var{parameter}@dots{}
32913 @var{call-id} is the identifier which says which host system call should
32914 be called. This is just the name of the function. Translation into the
32915 correct system call is only applicable as it's defined in @value{GDBN}.
32916 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32919 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32920 this very system call.
32922 The target replies with this packet when it expects @value{GDBN} to
32923 call a host system call on behalf of the target. @value{GDBN} replies
32924 with an appropriate @samp{F} packet and keeps up waiting for the next
32925 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32926 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32927 Protocol Extension}, for more details.
32931 @node General Query Packets
32932 @section General Query Packets
32933 @cindex remote query requests
32935 Packets starting with @samp{q} are @dfn{general query packets};
32936 packets starting with @samp{Q} are @dfn{general set packets}. General
32937 query and set packets are a semi-unified form for retrieving and
32938 sending information to and from the stub.
32940 The initial letter of a query or set packet is followed by a name
32941 indicating what sort of thing the packet applies to. For example,
32942 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32943 definitions with the stub. These packet names follow some
32948 The name must not contain commas, colons or semicolons.
32950 Most @value{GDBN} query and set packets have a leading upper case
32953 The names of custom vendor packets should use a company prefix, in
32954 lower case, followed by a period. For example, packets designed at
32955 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32956 foos) or @samp{Qacme.bar} (for setting bars).
32959 The name of a query or set packet should be separated from any
32960 parameters by a @samp{:}; the parameters themselves should be
32961 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32962 full packet name, and check for a separator or the end of the packet,
32963 in case two packet names share a common prefix. New packets should not begin
32964 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32965 packets predate these conventions, and have arguments without any terminator
32966 for the packet name; we suspect they are in widespread use in places that
32967 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32968 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32971 Like the descriptions of the other packets, each description here
32972 has a template showing the packet's overall syntax, followed by an
32973 explanation of the packet's meaning. We include spaces in some of the
32974 templates for clarity; these are not part of the packet's syntax. No
32975 @value{GDBN} packet uses spaces to separate its components.
32977 Here are the currently defined query and set packets:
32981 @item QAllow:@var{op}:@var{val}@dots{}
32982 @cindex @samp{QAllow} packet
32983 Specify which operations @value{GDBN} expects to request of the
32984 target, as a semicolon-separated list of operation name and value
32985 pairs. Possible values for @var{op} include @samp{WriteReg},
32986 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32987 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32988 indicating that @value{GDBN} will not request the operation, or 1,
32989 indicating that it may. (The target can then use this to set up its
32990 own internals optimally, for instance if the debugger never expects to
32991 insert breakpoints, it may not need to install its own trap handler.)
32994 @cindex current thread, remote request
32995 @cindex @samp{qC} packet
32996 Return the current thread ID.
33000 @item QC @var{thread-id}
33001 Where @var{thread-id} is a thread ID as documented in
33002 @ref{thread-id syntax}.
33003 @item @r{(anything else)}
33004 Any other reply implies the old thread ID.
33007 @item qCRC:@var{addr},@var{length}
33008 @cindex CRC of memory block, remote request
33009 @cindex @samp{qCRC} packet
33010 Compute the CRC checksum of a block of memory using CRC-32 defined in
33011 IEEE 802.3. The CRC is computed byte at a time, taking the most
33012 significant bit of each byte first. The initial pattern code
33013 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33015 @emph{Note:} This is the same CRC used in validating separate debug
33016 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33017 Files}). However the algorithm is slightly different. When validating
33018 separate debug files, the CRC is computed taking the @emph{least}
33019 significant bit of each byte first, and the final result is inverted to
33020 detect trailing zeros.
33025 An error (such as memory fault)
33026 @item C @var{crc32}
33027 The specified memory region's checksum is @var{crc32}.
33031 @itemx qsThreadInfo
33032 @cindex list active threads, remote request
33033 @cindex @samp{qfThreadInfo} packet
33034 @cindex @samp{qsThreadInfo} packet
33035 Obtain a list of all active thread IDs from the target (OS). Since there
33036 may be too many active threads to fit into one reply packet, this query
33037 works iteratively: it may require more than one query/reply sequence to
33038 obtain the entire list of threads. The first query of the sequence will
33039 be the @samp{qfThreadInfo} query; subsequent queries in the
33040 sequence will be the @samp{qsThreadInfo} query.
33042 NOTE: This packet replaces the @samp{qL} query (see below).
33046 @item m @var{thread-id}
33048 @item m @var{thread-id},@var{thread-id}@dots{}
33049 a comma-separated list of thread IDs
33051 (lower case letter @samp{L}) denotes end of list.
33054 In response to each query, the target will reply with a list of one or
33055 more thread IDs, separated by commas.
33056 @value{GDBN} will respond to each reply with a request for more thread
33057 ids (using the @samp{qs} form of the query), until the target responds
33058 with @samp{l} (lower-case ell, for @dfn{last}).
33059 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33062 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33063 @cindex get thread-local storage address, remote request
33064 @cindex @samp{qGetTLSAddr} packet
33065 Fetch the address associated with thread local storage specified
33066 by @var{thread-id}, @var{offset}, and @var{lm}.
33068 @var{thread-id} is the thread ID associated with the
33069 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33071 @var{offset} is the (big endian, hex encoded) offset associated with the
33072 thread local variable. (This offset is obtained from the debug
33073 information associated with the variable.)
33075 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33076 load module associated with the thread local storage. For example,
33077 a @sc{gnu}/Linux system will pass the link map address of the shared
33078 object associated with the thread local storage under consideration.
33079 Other operating environments may choose to represent the load module
33080 differently, so the precise meaning of this parameter will vary.
33084 @item @var{XX}@dots{}
33085 Hex encoded (big endian) bytes representing the address of the thread
33086 local storage requested.
33089 An error occurred. @var{nn} are hex digits.
33092 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33095 @item qGetTIBAddr:@var{thread-id}
33096 @cindex get thread information block address
33097 @cindex @samp{qGetTIBAddr} packet
33098 Fetch address of the Windows OS specific Thread Information Block.
33100 @var{thread-id} is the thread ID associated with the thread.
33104 @item @var{XX}@dots{}
33105 Hex encoded (big endian) bytes representing the linear address of the
33106 thread information block.
33109 An error occured. This means that either the thread was not found, or the
33110 address could not be retrieved.
33113 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33116 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33117 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33118 digit) is one to indicate the first query and zero to indicate a
33119 subsequent query; @var{threadcount} (two hex digits) is the maximum
33120 number of threads the response packet can contain; and @var{nextthread}
33121 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33122 returned in the response as @var{argthread}.
33124 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33128 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33129 Where: @var{count} (two hex digits) is the number of threads being
33130 returned; @var{done} (one hex digit) is zero to indicate more threads
33131 and one indicates no further threads; @var{argthreadid} (eight hex
33132 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33133 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33134 digits). See @code{remote.c:parse_threadlist_response()}.
33138 @cindex section offsets, remote request
33139 @cindex @samp{qOffsets} packet
33140 Get section offsets that the target used when relocating the downloaded
33145 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33146 Relocate the @code{Text} section by @var{xxx} from its original address.
33147 Relocate the @code{Data} section by @var{yyy} from its original address.
33148 If the object file format provides segment information (e.g.@: @sc{elf}
33149 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33150 segments by the supplied offsets.
33152 @emph{Note: while a @code{Bss} offset may be included in the response,
33153 @value{GDBN} ignores this and instead applies the @code{Data} offset
33154 to the @code{Bss} section.}
33156 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33157 Relocate the first segment of the object file, which conventionally
33158 contains program code, to a starting address of @var{xxx}. If
33159 @samp{DataSeg} is specified, relocate the second segment, which
33160 conventionally contains modifiable data, to a starting address of
33161 @var{yyy}. @value{GDBN} will report an error if the object file
33162 does not contain segment information, or does not contain at least
33163 as many segments as mentioned in the reply. Extra segments are
33164 kept at fixed offsets relative to the last relocated segment.
33167 @item qP @var{mode} @var{thread-id}
33168 @cindex thread information, remote request
33169 @cindex @samp{qP} packet
33170 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33171 encoded 32 bit mode; @var{thread-id} is a thread ID
33172 (@pxref{thread-id syntax}).
33174 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33177 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33181 @cindex non-stop mode, remote request
33182 @cindex @samp{QNonStop} packet
33184 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33185 @xref{Remote Non-Stop}, for more information.
33190 The request succeeded.
33193 An error occurred. @var{nn} are hex digits.
33196 An empty reply indicates that @samp{QNonStop} is not supported by
33200 This packet is not probed by default; the remote stub must request it,
33201 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33202 Use of this packet is controlled by the @code{set non-stop} command;
33203 @pxref{Non-Stop Mode}.
33205 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33206 @cindex pass signals to inferior, remote request
33207 @cindex @samp{QPassSignals} packet
33208 @anchor{QPassSignals}
33209 Each listed @var{signal} should be passed directly to the inferior process.
33210 Signals are numbered identically to continue packets and stop replies
33211 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33212 strictly greater than the previous item. These signals do not need to stop
33213 the inferior, or be reported to @value{GDBN}. All other signals should be
33214 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33215 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33216 new list. This packet improves performance when using @samp{handle
33217 @var{signal} nostop noprint pass}.
33222 The request succeeded.
33225 An error occurred. @var{nn} are hex digits.
33228 An empty reply indicates that @samp{QPassSignals} is not supported by
33232 Use of this packet is controlled by the @code{set remote pass-signals}
33233 command (@pxref{Remote Configuration, set remote pass-signals}).
33234 This packet is not probed by default; the remote stub must request it,
33235 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33237 @item qRcmd,@var{command}
33238 @cindex execute remote command, remote request
33239 @cindex @samp{qRcmd} packet
33240 @var{command} (hex encoded) is passed to the local interpreter for
33241 execution. Invalid commands should be reported using the output
33242 string. Before the final result packet, the target may also respond
33243 with a number of intermediate @samp{O@var{output}} console output
33244 packets. @emph{Implementors should note that providing access to a
33245 stubs's interpreter may have security implications}.
33250 A command response with no output.
33252 A command response with the hex encoded output string @var{OUTPUT}.
33254 Indicate a badly formed request.
33256 An empty reply indicates that @samp{qRcmd} is not recognized.
33259 (Note that the @code{qRcmd} packet's name is separated from the
33260 command by a @samp{,}, not a @samp{:}, contrary to the naming
33261 conventions above. Please don't use this packet as a model for new
33264 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33265 @cindex searching memory, in remote debugging
33266 @cindex @samp{qSearch:memory} packet
33267 @anchor{qSearch memory}
33268 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33269 @var{address} and @var{length} are encoded in hex.
33270 @var{search-pattern} is a sequence of bytes, hex encoded.
33275 The pattern was not found.
33277 The pattern was found at @var{address}.
33279 A badly formed request or an error was encountered while searching memory.
33281 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33284 @item QStartNoAckMode
33285 @cindex @samp{QStartNoAckMode} packet
33286 @anchor{QStartNoAckMode}
33287 Request that the remote stub disable the normal @samp{+}/@samp{-}
33288 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33293 The stub has switched to no-acknowledgment mode.
33294 @value{GDBN} acknowledges this reponse,
33295 but neither the stub nor @value{GDBN} shall send or expect further
33296 @samp{+}/@samp{-} acknowledgments in the current connection.
33298 An empty reply indicates that the stub does not support no-acknowledgment mode.
33301 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33302 @cindex supported packets, remote query
33303 @cindex features of the remote protocol
33304 @cindex @samp{qSupported} packet
33305 @anchor{qSupported}
33306 Tell the remote stub about features supported by @value{GDBN}, and
33307 query the stub for features it supports. This packet allows
33308 @value{GDBN} and the remote stub to take advantage of each others'
33309 features. @samp{qSupported} also consolidates multiple feature probes
33310 at startup, to improve @value{GDBN} performance---a single larger
33311 packet performs better than multiple smaller probe packets on
33312 high-latency links. Some features may enable behavior which must not
33313 be on by default, e.g.@: because it would confuse older clients or
33314 stubs. Other features may describe packets which could be
33315 automatically probed for, but are not. These features must be
33316 reported before @value{GDBN} will use them. This ``default
33317 unsupported'' behavior is not appropriate for all packets, but it
33318 helps to keep the initial connection time under control with new
33319 versions of @value{GDBN} which support increasing numbers of packets.
33323 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33324 The stub supports or does not support each returned @var{stubfeature},
33325 depending on the form of each @var{stubfeature} (see below for the
33328 An empty reply indicates that @samp{qSupported} is not recognized,
33329 or that no features needed to be reported to @value{GDBN}.
33332 The allowed forms for each feature (either a @var{gdbfeature} in the
33333 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33337 @item @var{name}=@var{value}
33338 The remote protocol feature @var{name} is supported, and associated
33339 with the specified @var{value}. The format of @var{value} depends
33340 on the feature, but it must not include a semicolon.
33342 The remote protocol feature @var{name} is supported, and does not
33343 need an associated value.
33345 The remote protocol feature @var{name} is not supported.
33347 The remote protocol feature @var{name} may be supported, and
33348 @value{GDBN} should auto-detect support in some other way when it is
33349 needed. This form will not be used for @var{gdbfeature} notifications,
33350 but may be used for @var{stubfeature} responses.
33353 Whenever the stub receives a @samp{qSupported} request, the
33354 supplied set of @value{GDBN} features should override any previous
33355 request. This allows @value{GDBN} to put the stub in a known
33356 state, even if the stub had previously been communicating with
33357 a different version of @value{GDBN}.
33359 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33364 This feature indicates whether @value{GDBN} supports multiprocess
33365 extensions to the remote protocol. @value{GDBN} does not use such
33366 extensions unless the stub also reports that it supports them by
33367 including @samp{multiprocess+} in its @samp{qSupported} reply.
33368 @xref{multiprocess extensions}, for details.
33371 This feature indicates that @value{GDBN} supports the XML target
33372 description. If the stub sees @samp{xmlRegisters=} with target
33373 specific strings separated by a comma, it will report register
33377 This feature indicates whether @value{GDBN} supports the
33378 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33379 instruction reply packet}).
33382 Stubs should ignore any unknown values for
33383 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33384 packet supports receiving packets of unlimited length (earlier
33385 versions of @value{GDBN} may reject overly long responses). Additional values
33386 for @var{gdbfeature} may be defined in the future to let the stub take
33387 advantage of new features in @value{GDBN}, e.g.@: incompatible
33388 improvements in the remote protocol---the @samp{multiprocess} feature is
33389 an example of such a feature. The stub's reply should be independent
33390 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33391 describes all the features it supports, and then the stub replies with
33392 all the features it supports.
33394 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33395 responses, as long as each response uses one of the standard forms.
33397 Some features are flags. A stub which supports a flag feature
33398 should respond with a @samp{+} form response. Other features
33399 require values, and the stub should respond with an @samp{=}
33402 Each feature has a default value, which @value{GDBN} will use if
33403 @samp{qSupported} is not available or if the feature is not mentioned
33404 in the @samp{qSupported} response. The default values are fixed; a
33405 stub is free to omit any feature responses that match the defaults.
33407 Not all features can be probed, but for those which can, the probing
33408 mechanism is useful: in some cases, a stub's internal
33409 architecture may not allow the protocol layer to know some information
33410 about the underlying target in advance. This is especially common in
33411 stubs which may be configured for multiple targets.
33413 These are the currently defined stub features and their properties:
33415 @multitable @columnfractions 0.35 0.2 0.12 0.2
33416 @c NOTE: The first row should be @headitem, but we do not yet require
33417 @c a new enough version of Texinfo (4.7) to use @headitem.
33419 @tab Value Required
33423 @item @samp{PacketSize}
33428 @item @samp{qXfer:auxv:read}
33433 @item @samp{qXfer:features:read}
33438 @item @samp{qXfer:libraries:read}
33443 @item @samp{qXfer:memory-map:read}
33448 @item @samp{qXfer:sdata:read}
33453 @item @samp{qXfer:spu:read}
33458 @item @samp{qXfer:spu:write}
33463 @item @samp{qXfer:siginfo:read}
33468 @item @samp{qXfer:siginfo:write}
33473 @item @samp{qXfer:threads:read}
33478 @item @samp{qXfer:traceframe-info:read}
33484 @item @samp{QNonStop}
33489 @item @samp{QPassSignals}
33494 @item @samp{QStartNoAckMode}
33499 @item @samp{multiprocess}
33504 @item @samp{ConditionalTracepoints}
33509 @item @samp{ReverseContinue}
33514 @item @samp{ReverseStep}
33519 @item @samp{TracepointSource}
33524 @item @samp{QAllow}
33531 These are the currently defined stub features, in more detail:
33534 @cindex packet size, remote protocol
33535 @item PacketSize=@var{bytes}
33536 The remote stub can accept packets up to at least @var{bytes} in
33537 length. @value{GDBN} will send packets up to this size for bulk
33538 transfers, and will never send larger packets. This is a limit on the
33539 data characters in the packet, including the frame and checksum.
33540 There is no trailing NUL byte in a remote protocol packet; if the stub
33541 stores packets in a NUL-terminated format, it should allow an extra
33542 byte in its buffer for the NUL. If this stub feature is not supported,
33543 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33545 @item qXfer:auxv:read
33546 The remote stub understands the @samp{qXfer:auxv:read} packet
33547 (@pxref{qXfer auxiliary vector read}).
33549 @item qXfer:features:read
33550 The remote stub understands the @samp{qXfer:features:read} packet
33551 (@pxref{qXfer target description read}).
33553 @item qXfer:libraries:read
33554 The remote stub understands the @samp{qXfer:libraries:read} packet
33555 (@pxref{qXfer library list read}).
33557 @item qXfer:memory-map:read
33558 The remote stub understands the @samp{qXfer:memory-map:read} packet
33559 (@pxref{qXfer memory map read}).
33561 @item qXfer:sdata:read
33562 The remote stub understands the @samp{qXfer:sdata:read} packet
33563 (@pxref{qXfer sdata read}).
33565 @item qXfer:spu:read
33566 The remote stub understands the @samp{qXfer:spu:read} packet
33567 (@pxref{qXfer spu read}).
33569 @item qXfer:spu:write
33570 The remote stub understands the @samp{qXfer:spu:write} packet
33571 (@pxref{qXfer spu write}).
33573 @item qXfer:siginfo:read
33574 The remote stub understands the @samp{qXfer:siginfo:read} packet
33575 (@pxref{qXfer siginfo read}).
33577 @item qXfer:siginfo:write
33578 The remote stub understands the @samp{qXfer:siginfo:write} packet
33579 (@pxref{qXfer siginfo write}).
33581 @item qXfer:threads:read
33582 The remote stub understands the @samp{qXfer:threads:read} packet
33583 (@pxref{qXfer threads read}).
33585 @item qXfer:traceframe-info:read
33586 The remote stub understands the @samp{qXfer:traceframe-info:read}
33587 packet (@pxref{qXfer traceframe info read}).
33590 The remote stub understands the @samp{QNonStop} packet
33591 (@pxref{QNonStop}).
33594 The remote stub understands the @samp{QPassSignals} packet
33595 (@pxref{QPassSignals}).
33597 @item QStartNoAckMode
33598 The remote stub understands the @samp{QStartNoAckMode} packet and
33599 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33602 @anchor{multiprocess extensions}
33603 @cindex multiprocess extensions, in remote protocol
33604 The remote stub understands the multiprocess extensions to the remote
33605 protocol syntax. The multiprocess extensions affect the syntax of
33606 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33607 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33608 replies. Note that reporting this feature indicates support for the
33609 syntactic extensions only, not that the stub necessarily supports
33610 debugging of more than one process at a time. The stub must not use
33611 multiprocess extensions in packet replies unless @value{GDBN} has also
33612 indicated it supports them in its @samp{qSupported} request.
33614 @item qXfer:osdata:read
33615 The remote stub understands the @samp{qXfer:osdata:read} packet
33616 ((@pxref{qXfer osdata read}).
33618 @item ConditionalTracepoints
33619 The remote stub accepts and implements conditional expressions defined
33620 for tracepoints (@pxref{Tracepoint Conditions}).
33622 @item ReverseContinue
33623 The remote stub accepts and implements the reverse continue packet
33627 The remote stub accepts and implements the reverse step packet
33630 @item TracepointSource
33631 The remote stub understands the @samp{QTDPsrc} packet that supplies
33632 the source form of tracepoint definitions.
33635 The remote stub understands the @samp{QAllow} packet.
33637 @item StaticTracepoint
33638 @cindex static tracepoints, in remote protocol
33639 The remote stub supports static tracepoints.
33644 @cindex symbol lookup, remote request
33645 @cindex @samp{qSymbol} packet
33646 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33647 requests. Accept requests from the target for the values of symbols.
33652 The target does not need to look up any (more) symbols.
33653 @item qSymbol:@var{sym_name}
33654 The target requests the value of symbol @var{sym_name} (hex encoded).
33655 @value{GDBN} may provide the value by using the
33656 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33660 @item qSymbol:@var{sym_value}:@var{sym_name}
33661 Set the value of @var{sym_name} to @var{sym_value}.
33663 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33664 target has previously requested.
33666 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33667 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33673 The target does not need to look up any (more) symbols.
33674 @item qSymbol:@var{sym_name}
33675 The target requests the value of a new symbol @var{sym_name} (hex
33676 encoded). @value{GDBN} will continue to supply the values of symbols
33677 (if available), until the target ceases to request them.
33682 @item QTDisconnected
33689 @xref{Tracepoint Packets}.
33691 @item qThreadExtraInfo,@var{thread-id}
33692 @cindex thread attributes info, remote request
33693 @cindex @samp{qThreadExtraInfo} packet
33694 Obtain a printable string description of a thread's attributes from
33695 the target OS. @var{thread-id} is a thread ID;
33696 see @ref{thread-id syntax}. This
33697 string may contain anything that the target OS thinks is interesting
33698 for @value{GDBN} to tell the user about the thread. The string is
33699 displayed in @value{GDBN}'s @code{info threads} display. Some
33700 examples of possible thread extra info strings are @samp{Runnable}, or
33701 @samp{Blocked on Mutex}.
33705 @item @var{XX}@dots{}
33706 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33707 comprising the printable string containing the extra information about
33708 the thread's attributes.
33711 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33712 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33713 conventions above. Please don't use this packet as a model for new
33728 @xref{Tracepoint Packets}.
33730 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33731 @cindex read special object, remote request
33732 @cindex @samp{qXfer} packet
33733 @anchor{qXfer read}
33734 Read uninterpreted bytes from the target's special data area
33735 identified by the keyword @var{object}. Request @var{length} bytes
33736 starting at @var{offset} bytes into the data. The content and
33737 encoding of @var{annex} is specific to @var{object}; it can supply
33738 additional details about what data to access.
33740 Here are the specific requests of this form defined so far. All
33741 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33742 formats, listed below.
33745 @item qXfer:auxv:read::@var{offset},@var{length}
33746 @anchor{qXfer auxiliary vector read}
33747 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33748 auxiliary vector}. Note @var{annex} must be empty.
33750 This packet is not probed by default; the remote stub must request it,
33751 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33753 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33754 @anchor{qXfer target description read}
33755 Access the @dfn{target description}. @xref{Target Descriptions}. The
33756 annex specifies which XML document to access. The main description is
33757 always loaded from the @samp{target.xml} annex.
33759 This packet is not probed by default; the remote stub must request it,
33760 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33762 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33763 @anchor{qXfer library list read}
33764 Access the target's list of loaded libraries. @xref{Library List Format}.
33765 The annex part of the generic @samp{qXfer} packet must be empty
33766 (@pxref{qXfer read}).
33768 Targets which maintain a list of libraries in the program's memory do
33769 not need to implement this packet; it is designed for platforms where
33770 the operating system manages the list of loaded libraries.
33772 This packet is not probed by default; the remote stub must request it,
33773 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33775 @item qXfer:memory-map:read::@var{offset},@var{length}
33776 @anchor{qXfer memory map read}
33777 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33778 annex part of the generic @samp{qXfer} packet must be empty
33779 (@pxref{qXfer read}).
33781 This packet is not probed by default; the remote stub must request it,
33782 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33784 @item qXfer:sdata:read::@var{offset},@var{length}
33785 @anchor{qXfer sdata read}
33787 Read contents of the extra collected static tracepoint marker
33788 information. The annex part of the generic @samp{qXfer} packet must
33789 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33792 This packet is not probed by default; the remote stub must request it,
33793 by supplying an appropriate @samp{qSupported} response
33794 (@pxref{qSupported}).
33796 @item qXfer:siginfo:read::@var{offset},@var{length}
33797 @anchor{qXfer siginfo read}
33798 Read contents of the extra signal information on the target
33799 system. The annex part of the generic @samp{qXfer} packet must be
33800 empty (@pxref{qXfer read}).
33802 This packet is not probed by default; the remote stub must request it,
33803 by supplying an appropriate @samp{qSupported} response
33804 (@pxref{qSupported}).
33806 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33807 @anchor{qXfer spu read}
33808 Read contents of an @code{spufs} file on the target system. The
33809 annex specifies which file to read; it must be of the form
33810 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33811 in the target process, and @var{name} identifes the @code{spufs} file
33812 in that context to be accessed.
33814 This packet is not probed by default; the remote stub must request it,
33815 by supplying an appropriate @samp{qSupported} response
33816 (@pxref{qSupported}).
33818 @item qXfer:threads:read::@var{offset},@var{length}
33819 @anchor{qXfer threads read}
33820 Access the list of threads on target. @xref{Thread List Format}. The
33821 annex part of the generic @samp{qXfer} packet must be empty
33822 (@pxref{qXfer read}).
33824 This packet is not probed by default; the remote stub must request it,
33825 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33827 @item qXfer:traceframe-info:read::@var{offset},@var{length}
33828 @anchor{qXfer traceframe info read}
33830 Return a description of the current traceframe's contents.
33831 @xref{Traceframe Info Format}. The annex part of the generic
33832 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
33834 This packet is not probed by default; the remote stub must request it,
33835 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33837 @item qXfer:osdata:read::@var{offset},@var{length}
33838 @anchor{qXfer osdata read}
33839 Access the target's @dfn{operating system information}.
33840 @xref{Operating System Information}.
33847 Data @var{data} (@pxref{Binary Data}) has been read from the
33848 target. There may be more data at a higher address (although
33849 it is permitted to return @samp{m} even for the last valid
33850 block of data, as long as at least one byte of data was read).
33851 @var{data} may have fewer bytes than the @var{length} in the
33855 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33856 There is no more data to be read. @var{data} may have fewer bytes
33857 than the @var{length} in the request.
33860 The @var{offset} in the request is at the end of the data.
33861 There is no more data to be read.
33864 The request was malformed, or @var{annex} was invalid.
33867 The offset was invalid, or there was an error encountered reading the data.
33868 @var{nn} is a hex-encoded @code{errno} value.
33871 An empty reply indicates the @var{object} string was not recognized by
33872 the stub, or that the object does not support reading.
33875 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33876 @cindex write data into object, remote request
33877 @anchor{qXfer write}
33878 Write uninterpreted bytes into the target's special data area
33879 identified by the keyword @var{object}, starting at @var{offset} bytes
33880 into the data. @var{data}@dots{} is the binary-encoded data
33881 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33882 is specific to @var{object}; it can supply additional details about what data
33885 Here are the specific requests of this form defined so far. All
33886 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33887 formats, listed below.
33890 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33891 @anchor{qXfer siginfo write}
33892 Write @var{data} to the extra signal information on the target system.
33893 The annex part of the generic @samp{qXfer} packet must be
33894 empty (@pxref{qXfer write}).
33896 This packet is not probed by default; the remote stub must request it,
33897 by supplying an appropriate @samp{qSupported} response
33898 (@pxref{qSupported}).
33900 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33901 @anchor{qXfer spu write}
33902 Write @var{data} to an @code{spufs} file on the target system. The
33903 annex specifies which file to write; it must be of the form
33904 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33905 in the target process, and @var{name} identifes the @code{spufs} file
33906 in that context to be accessed.
33908 This packet is not probed by default; the remote stub must request it,
33909 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33915 @var{nn} (hex encoded) is the number of bytes written.
33916 This may be fewer bytes than supplied in the request.
33919 The request was malformed, or @var{annex} was invalid.
33922 The offset was invalid, or there was an error encountered writing the data.
33923 @var{nn} is a hex-encoded @code{errno} value.
33926 An empty reply indicates the @var{object} string was not
33927 recognized by the stub, or that the object does not support writing.
33930 @item qXfer:@var{object}:@var{operation}:@dots{}
33931 Requests of this form may be added in the future. When a stub does
33932 not recognize the @var{object} keyword, or its support for
33933 @var{object} does not recognize the @var{operation} keyword, the stub
33934 must respond with an empty packet.
33936 @item qAttached:@var{pid}
33937 @cindex query attached, remote request
33938 @cindex @samp{qAttached} packet
33939 Return an indication of whether the remote server attached to an
33940 existing process or created a new process. When the multiprocess
33941 protocol extensions are supported (@pxref{multiprocess extensions}),
33942 @var{pid} is an integer in hexadecimal format identifying the target
33943 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33944 the query packet will be simplified as @samp{qAttached}.
33946 This query is used, for example, to know whether the remote process
33947 should be detached or killed when a @value{GDBN} session is ended with
33948 the @code{quit} command.
33953 The remote server attached to an existing process.
33955 The remote server created a new process.
33957 A badly formed request or an error was encountered.
33962 @node Architecture-Specific Protocol Details
33963 @section Architecture-Specific Protocol Details
33965 This section describes how the remote protocol is applied to specific
33966 target architectures. Also see @ref{Standard Target Features}, for
33967 details of XML target descriptions for each architecture.
33971 @subsubsection Breakpoint Kinds
33973 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33978 16-bit Thumb mode breakpoint.
33981 32-bit Thumb mode (Thumb-2) breakpoint.
33984 32-bit ARM mode breakpoint.
33990 @subsubsection Register Packet Format
33992 The following @code{g}/@code{G} packets have previously been defined.
33993 In the below, some thirty-two bit registers are transferred as
33994 sixty-four bits. Those registers should be zero/sign extended (which?)
33995 to fill the space allocated. Register bytes are transferred in target
33996 byte order. The two nibbles within a register byte are transferred
33997 most-significant - least-significant.
34003 All registers are transferred as thirty-two bit quantities in the order:
34004 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34005 registers; fsr; fir; fp.
34009 All registers are transferred as sixty-four bit quantities (including
34010 thirty-two bit registers such as @code{sr}). The ordering is the same
34015 @node Tracepoint Packets
34016 @section Tracepoint Packets
34017 @cindex tracepoint packets
34018 @cindex packets, tracepoint
34020 Here we describe the packets @value{GDBN} uses to implement
34021 tracepoints (@pxref{Tracepoints}).
34025 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34026 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34027 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34028 the tracepoint is disabled. @var{step} is the tracepoint's step
34029 count, and @var{pass} is its pass count. If an @samp{F} is present,
34030 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34031 the number of bytes that the target should copy elsewhere to make room
34032 for the tracepoint. If an @samp{X} is present, it introduces a
34033 tracepoint condition, which consists of a hexadecimal length, followed
34034 by a comma and hex-encoded bytes, in a manner similar to action
34035 encodings as described below. If the trailing @samp{-} is present,
34036 further @samp{QTDP} packets will follow to specify this tracepoint's
34042 The packet was understood and carried out.
34044 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34046 The packet was not recognized.
34049 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34050 Define actions to be taken when a tracepoint is hit. @var{n} and
34051 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34052 this tracepoint. This packet may only be sent immediately after
34053 another @samp{QTDP} packet that ended with a @samp{-}. If the
34054 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34055 specifying more actions for this tracepoint.
34057 In the series of action packets for a given tracepoint, at most one
34058 can have an @samp{S} before its first @var{action}. If such a packet
34059 is sent, it and the following packets define ``while-stepping''
34060 actions. Any prior packets define ordinary actions --- that is, those
34061 taken when the tracepoint is first hit. If no action packet has an
34062 @samp{S}, then all the packets in the series specify ordinary
34063 tracepoint actions.
34065 The @samp{@var{action}@dots{}} portion of the packet is a series of
34066 actions, concatenated without separators. Each action has one of the
34072 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34073 a hexadecimal number whose @var{i}'th bit is set if register number
34074 @var{i} should be collected. (The least significant bit is numbered
34075 zero.) Note that @var{mask} may be any number of digits long; it may
34076 not fit in a 32-bit word.
34078 @item M @var{basereg},@var{offset},@var{len}
34079 Collect @var{len} bytes of memory starting at the address in register
34080 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34081 @samp{-1}, then the range has a fixed address: @var{offset} is the
34082 address of the lowest byte to collect. The @var{basereg},
34083 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34084 values (the @samp{-1} value for @var{basereg} is a special case).
34086 @item X @var{len},@var{expr}
34087 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34088 it directs. @var{expr} is an agent expression, as described in
34089 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34090 two-digit hex number in the packet; @var{len} is the number of bytes
34091 in the expression (and thus one-half the number of hex digits in the
34096 Any number of actions may be packed together in a single @samp{QTDP}
34097 packet, as long as the packet does not exceed the maximum packet
34098 length (400 bytes, for many stubs). There may be only one @samp{R}
34099 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34100 actions. Any registers referred to by @samp{M} and @samp{X} actions
34101 must be collected by a preceding @samp{R} action. (The
34102 ``while-stepping'' actions are treated as if they were attached to a
34103 separate tracepoint, as far as these restrictions are concerned.)
34108 The packet was understood and carried out.
34110 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34112 The packet was not recognized.
34115 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34116 @cindex @samp{QTDPsrc} packet
34117 Specify a source string of tracepoint @var{n} at address @var{addr}.
34118 This is useful to get accurate reproduction of the tracepoints
34119 originally downloaded at the beginning of the trace run. @var{type}
34120 is the name of the tracepoint part, such as @samp{cond} for the
34121 tracepoint's conditional expression (see below for a list of types), while
34122 @var{bytes} is the string, encoded in hexadecimal.
34124 @var{start} is the offset of the @var{bytes} within the overall source
34125 string, while @var{slen} is the total length of the source string.
34126 This is intended for handling source strings that are longer than will
34127 fit in a single packet.
34128 @c Add detailed example when this info is moved into a dedicated
34129 @c tracepoint descriptions section.
34131 The available string types are @samp{at} for the location,
34132 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34133 @value{GDBN} sends a separate packet for each command in the action
34134 list, in the same order in which the commands are stored in the list.
34136 The target does not need to do anything with source strings except
34137 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34140 Although this packet is optional, and @value{GDBN} will only send it
34141 if the target replies with @samp{TracepointSource} @xref{General
34142 Query Packets}, it makes both disconnected tracing and trace files
34143 much easier to use. Otherwise the user must be careful that the
34144 tracepoints in effect while looking at trace frames are identical to
34145 the ones in effect during the trace run; even a small discrepancy
34146 could cause @samp{tdump} not to work, or a particular trace frame not
34149 @item QTDV:@var{n}:@var{value}
34150 @cindex define trace state variable, remote request
34151 @cindex @samp{QTDV} packet
34152 Create a new trace state variable, number @var{n}, with an initial
34153 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34154 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34155 the option of not using this packet for initial values of zero; the
34156 target should simply create the trace state variables as they are
34157 mentioned in expressions.
34159 @item QTFrame:@var{n}
34160 Select the @var{n}'th tracepoint frame from the buffer, and use the
34161 register and memory contents recorded there to answer subsequent
34162 request packets from @value{GDBN}.
34164 A successful reply from the stub indicates that the stub has found the
34165 requested frame. The response is a series of parts, concatenated
34166 without separators, describing the frame we selected. Each part has
34167 one of the following forms:
34171 The selected frame is number @var{n} in the trace frame buffer;
34172 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34173 was no frame matching the criteria in the request packet.
34176 The selected trace frame records a hit of tracepoint number @var{t};
34177 @var{t} is a hexadecimal number.
34181 @item QTFrame:pc:@var{addr}
34182 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34183 currently selected frame whose PC is @var{addr};
34184 @var{addr} is a hexadecimal number.
34186 @item QTFrame:tdp:@var{t}
34187 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34188 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34189 is a hexadecimal number.
34191 @item QTFrame:range:@var{start}:@var{end}
34192 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34193 currently selected frame whose PC is between @var{start} (inclusive)
34194 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34197 @item QTFrame:outside:@var{start}:@var{end}
34198 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34199 frame @emph{outside} the given range of addresses (exclusive).
34202 Begin the tracepoint experiment. Begin collecting data from
34203 tracepoint hits in the trace frame buffer. This packet supports the
34204 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34205 instruction reply packet}).
34208 End the tracepoint experiment. Stop collecting trace frames.
34211 Clear the table of tracepoints, and empty the trace frame buffer.
34213 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34214 Establish the given ranges of memory as ``transparent''. The stub
34215 will answer requests for these ranges from memory's current contents,
34216 if they were not collected as part of the tracepoint hit.
34218 @value{GDBN} uses this to mark read-only regions of memory, like those
34219 containing program code. Since these areas never change, they should
34220 still have the same contents they did when the tracepoint was hit, so
34221 there's no reason for the stub to refuse to provide their contents.
34223 @item QTDisconnected:@var{value}
34224 Set the choice to what to do with the tracing run when @value{GDBN}
34225 disconnects from the target. A @var{value} of 1 directs the target to
34226 continue the tracing run, while 0 tells the target to stop tracing if
34227 @value{GDBN} is no longer in the picture.
34230 Ask the stub if there is a trace experiment running right now.
34232 The reply has the form:
34236 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34237 @var{running} is a single digit @code{1} if the trace is presently
34238 running, or @code{0} if not. It is followed by semicolon-separated
34239 optional fields that an agent may use to report additional status.
34243 If the trace is not running, the agent may report any of several
34244 explanations as one of the optional fields:
34249 No trace has been run yet.
34252 The trace was stopped by a user-originated stop command.
34255 The trace stopped because the trace buffer filled up.
34257 @item tdisconnected:0
34258 The trace stopped because @value{GDBN} disconnected from the target.
34260 @item tpasscount:@var{tpnum}
34261 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34263 @item terror:@var{text}:@var{tpnum}
34264 The trace stopped because tracepoint @var{tpnum} had an error. The
34265 string @var{text} is available to describe the nature of the error
34266 (for instance, a divide by zero in the condition expression).
34267 @var{text} is hex encoded.
34270 The trace stopped for some other reason.
34274 Additional optional fields supply statistical and other information.
34275 Although not required, they are extremely useful for users monitoring
34276 the progress of a trace run. If a trace has stopped, and these
34277 numbers are reported, they must reflect the state of the just-stopped
34282 @item tframes:@var{n}
34283 The number of trace frames in the buffer.
34285 @item tcreated:@var{n}
34286 The total number of trace frames created during the run. This may
34287 be larger than the trace frame count, if the buffer is circular.
34289 @item tsize:@var{n}
34290 The total size of the trace buffer, in bytes.
34292 @item tfree:@var{n}
34293 The number of bytes still unused in the buffer.
34295 @item circular:@var{n}
34296 The value of the circular trace buffer flag. @code{1} means that the
34297 trace buffer is circular and old trace frames will be discarded if
34298 necessary to make room, @code{0} means that the trace buffer is linear
34301 @item disconn:@var{n}
34302 The value of the disconnected tracing flag. @code{1} means that
34303 tracing will continue after @value{GDBN} disconnects, @code{0} means
34304 that the trace run will stop.
34308 @item qTV:@var{var}
34309 @cindex trace state variable value, remote request
34310 @cindex @samp{qTV} packet
34311 Ask the stub for the value of the trace state variable number @var{var}.
34316 The value of the variable is @var{value}. This will be the current
34317 value of the variable if the user is examining a running target, or a
34318 saved value if the variable was collected in the trace frame that the
34319 user is looking at. Note that multiple requests may result in
34320 different reply values, such as when requesting values while the
34321 program is running.
34324 The value of the variable is unknown. This would occur, for example,
34325 if the user is examining a trace frame in which the requested variable
34331 These packets request data about tracepoints that are being used by
34332 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34333 of data, and multiple @code{qTsP} to get additional pieces. Replies
34334 to these packets generally take the form of the @code{QTDP} packets
34335 that define tracepoints. (FIXME add detailed syntax)
34339 These packets request data about trace state variables that are on the
34340 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34341 and multiple @code{qTsV} to get additional variables. Replies to
34342 these packets follow the syntax of the @code{QTDV} packets that define
34343 trace state variables.
34347 These packets request data about static tracepoint markers that exist
34348 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34349 first piece of data, and multiple @code{qTsSTM} to get additional
34350 pieces. Replies to these packets take the following form:
34354 @item m @var{address}:@var{id}:@var{extra}
34356 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34357 a comma-separated list of markers
34359 (lower case letter @samp{L}) denotes end of list.
34361 An error occurred. @var{nn} are hex digits.
34363 An empty reply indicates that the request is not supported by the
34367 @var{address} is encoded in hex.
34368 @var{id} and @var{extra} are strings encoded in hex.
34370 In response to each query, the target will reply with a list of one or
34371 more markers, separated by commas. @value{GDBN} will respond to each
34372 reply with a request for more markers (using the @samp{qs} form of the
34373 query), until the target responds with @samp{l} (lower-case ell, for
34376 @item qTSTMat:@var{address}
34377 This packets requests data about static tracepoint markers in the
34378 target program at @var{address}. Replies to this packet follow the
34379 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34380 tracepoint markers.
34382 @item QTSave:@var{filename}
34383 This packet directs the target to save trace data to the file name
34384 @var{filename} in the target's filesystem. @var{filename} is encoded
34385 as a hex string; the interpretation of the file name (relative vs
34386 absolute, wild cards, etc) is up to the target.
34388 @item qTBuffer:@var{offset},@var{len}
34389 Return up to @var{len} bytes of the current contents of trace buffer,
34390 starting at @var{offset}. The trace buffer is treated as if it were
34391 a contiguous collection of traceframes, as per the trace file format.
34392 The reply consists as many hex-encoded bytes as the target can deliver
34393 in a packet; it is not an error to return fewer than were asked for.
34394 A reply consisting of just @code{l} indicates that no bytes are
34397 @item QTBuffer:circular:@var{value}
34398 This packet directs the target to use a circular trace buffer if
34399 @var{value} is 1, or a linear buffer if the value is 0.
34403 @subsection Relocate instruction reply packet
34404 When installing fast tracepoints in memory, the target may need to
34405 relocate the instruction currently at the tracepoint address to a
34406 different address in memory. For most instructions, a simple copy is
34407 enough, but, for example, call instructions that implicitly push the
34408 return address on the stack, and relative branches or other
34409 PC-relative instructions require offset adjustment, so that the effect
34410 of executing the instruction at a different address is the same as if
34411 it had executed in the original location.
34413 In response to several of the tracepoint packets, the target may also
34414 respond with a number of intermediate @samp{qRelocInsn} request
34415 packets before the final result packet, to have @value{GDBN} handle
34416 this relocation operation. If a packet supports this mechanism, its
34417 documentation will explicitly say so. See for example the above
34418 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34419 format of the request is:
34422 @item qRelocInsn:@var{from};@var{to}
34424 This requests @value{GDBN} to copy instruction at address @var{from}
34425 to address @var{to}, possibly adjusted so that executing the
34426 instruction at @var{to} has the same effect as executing it at
34427 @var{from}. @value{GDBN} writes the adjusted instruction to target
34428 memory starting at @var{to}.
34433 @item qRelocInsn:@var{adjusted_size}
34434 Informs the stub the relocation is complete. @var{adjusted_size} is
34435 the length in bytes of resulting relocated instruction sequence.
34437 A badly formed request was detected, or an error was encountered while
34438 relocating the instruction.
34441 @node Host I/O Packets
34442 @section Host I/O Packets
34443 @cindex Host I/O, remote protocol
34444 @cindex file transfer, remote protocol
34446 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34447 operations on the far side of a remote link. For example, Host I/O is
34448 used to upload and download files to a remote target with its own
34449 filesystem. Host I/O uses the same constant values and data structure
34450 layout as the target-initiated File-I/O protocol. However, the
34451 Host I/O packets are structured differently. The target-initiated
34452 protocol relies on target memory to store parameters and buffers.
34453 Host I/O requests are initiated by @value{GDBN}, and the
34454 target's memory is not involved. @xref{File-I/O Remote Protocol
34455 Extension}, for more details on the target-initiated protocol.
34457 The Host I/O request packets all encode a single operation along with
34458 its arguments. They have this format:
34462 @item vFile:@var{operation}: @var{parameter}@dots{}
34463 @var{operation} is the name of the particular request; the target
34464 should compare the entire packet name up to the second colon when checking
34465 for a supported operation. The format of @var{parameter} depends on
34466 the operation. Numbers are always passed in hexadecimal. Negative
34467 numbers have an explicit minus sign (i.e.@: two's complement is not
34468 used). Strings (e.g.@: filenames) are encoded as a series of
34469 hexadecimal bytes. The last argument to a system call may be a
34470 buffer of escaped binary data (@pxref{Binary Data}).
34474 The valid responses to Host I/O packets are:
34478 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34479 @var{result} is the integer value returned by this operation, usually
34480 non-negative for success and -1 for errors. If an error has occured,
34481 @var{errno} will be included in the result. @var{errno} will have a
34482 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34483 operations which return data, @var{attachment} supplies the data as a
34484 binary buffer. Binary buffers in response packets are escaped in the
34485 normal way (@pxref{Binary Data}). See the individual packet
34486 documentation for the interpretation of @var{result} and
34490 An empty response indicates that this operation is not recognized.
34494 These are the supported Host I/O operations:
34497 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34498 Open a file at @var{pathname} and return a file descriptor for it, or
34499 return -1 if an error occurs. @var{pathname} is a string,
34500 @var{flags} is an integer indicating a mask of open flags
34501 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34502 of mode bits to use if the file is created (@pxref{mode_t Values}).
34503 @xref{open}, for details of the open flags and mode values.
34505 @item vFile:close: @var{fd}
34506 Close the open file corresponding to @var{fd} and return 0, or
34507 -1 if an error occurs.
34509 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34510 Read data from the open file corresponding to @var{fd}. Up to
34511 @var{count} bytes will be read from the file, starting at @var{offset}
34512 relative to the start of the file. The target may read fewer bytes;
34513 common reasons include packet size limits and an end-of-file
34514 condition. The number of bytes read is returned. Zero should only be
34515 returned for a successful read at the end of the file, or if
34516 @var{count} was zero.
34518 The data read should be returned as a binary attachment on success.
34519 If zero bytes were read, the response should include an empty binary
34520 attachment (i.e.@: a trailing semicolon). The return value is the
34521 number of target bytes read; the binary attachment may be longer if
34522 some characters were escaped.
34524 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34525 Write @var{data} (a binary buffer) to the open file corresponding
34526 to @var{fd}. Start the write at @var{offset} from the start of the
34527 file. Unlike many @code{write} system calls, there is no
34528 separate @var{count} argument; the length of @var{data} in the
34529 packet is used. @samp{vFile:write} returns the number of bytes written,
34530 which may be shorter than the length of @var{data}, or -1 if an
34533 @item vFile:unlink: @var{pathname}
34534 Delete the file at @var{pathname} on the target. Return 0,
34535 or -1 if an error occurs. @var{pathname} is a string.
34540 @section Interrupts
34541 @cindex interrupts (remote protocol)
34543 When a program on the remote target is running, @value{GDBN} may
34544 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34545 a @code{BREAK} followed by @code{g},
34546 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34548 The precise meaning of @code{BREAK} is defined by the transport
34549 mechanism and may, in fact, be undefined. @value{GDBN} does not
34550 currently define a @code{BREAK} mechanism for any of the network
34551 interfaces except for TCP, in which case @value{GDBN} sends the
34552 @code{telnet} BREAK sequence.
34554 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34555 transport mechanisms. It is represented by sending the single byte
34556 @code{0x03} without any of the usual packet overhead described in
34557 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34558 transmitted as part of a packet, it is considered to be packet data
34559 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34560 (@pxref{X packet}), used for binary downloads, may include an unescaped
34561 @code{0x03} as part of its packet.
34563 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34564 When Linux kernel receives this sequence from serial port,
34565 it stops execution and connects to gdb.
34567 Stubs are not required to recognize these interrupt mechanisms and the
34568 precise meaning associated with receipt of the interrupt is
34569 implementation defined. If the target supports debugging of multiple
34570 threads and/or processes, it should attempt to interrupt all
34571 currently-executing threads and processes.
34572 If the stub is successful at interrupting the
34573 running program, it should send one of the stop
34574 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34575 of successfully stopping the program in all-stop mode, and a stop reply
34576 for each stopped thread in non-stop mode.
34577 Interrupts received while the
34578 program is stopped are discarded.
34580 @node Notification Packets
34581 @section Notification Packets
34582 @cindex notification packets
34583 @cindex packets, notification
34585 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34586 packets that require no acknowledgment. Both the GDB and the stub
34587 may send notifications (although the only notifications defined at
34588 present are sent by the stub). Notifications carry information
34589 without incurring the round-trip latency of an acknowledgment, and so
34590 are useful for low-impact communications where occasional packet loss
34593 A notification packet has the form @samp{% @var{data} #
34594 @var{checksum}}, where @var{data} is the content of the notification,
34595 and @var{checksum} is a checksum of @var{data}, computed and formatted
34596 as for ordinary @value{GDBN} packets. A notification's @var{data}
34597 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34598 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34599 to acknowledge the notification's receipt or to report its corruption.
34601 Every notification's @var{data} begins with a name, which contains no
34602 colon characters, followed by a colon character.
34604 Recipients should silently ignore corrupted notifications and
34605 notifications they do not understand. Recipients should restart
34606 timeout periods on receipt of a well-formed notification, whether or
34607 not they understand it.
34609 Senders should only send the notifications described here when this
34610 protocol description specifies that they are permitted. In the
34611 future, we may extend the protocol to permit existing notifications in
34612 new contexts; this rule helps older senders avoid confusing newer
34615 (Older versions of @value{GDBN} ignore bytes received until they see
34616 the @samp{$} byte that begins an ordinary packet, so new stubs may
34617 transmit notifications without fear of confusing older clients. There
34618 are no notifications defined for @value{GDBN} to send at the moment, but we
34619 assume that most older stubs would ignore them, as well.)
34621 The following notification packets from the stub to @value{GDBN} are
34625 @item Stop: @var{reply}
34626 Report an asynchronous stop event in non-stop mode.
34627 The @var{reply} has the form of a stop reply, as
34628 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34629 for information on how these notifications are acknowledged by
34633 @node Remote Non-Stop
34634 @section Remote Protocol Support for Non-Stop Mode
34636 @value{GDBN}'s remote protocol supports non-stop debugging of
34637 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34638 supports non-stop mode, it should report that to @value{GDBN} by including
34639 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34641 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34642 establishing a new connection with the stub. Entering non-stop mode
34643 does not alter the state of any currently-running threads, but targets
34644 must stop all threads in any already-attached processes when entering
34645 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34646 probe the target state after a mode change.
34648 In non-stop mode, when an attached process encounters an event that
34649 would otherwise be reported with a stop reply, it uses the
34650 asynchronous notification mechanism (@pxref{Notification Packets}) to
34651 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34652 in all processes are stopped when a stop reply is sent, in non-stop
34653 mode only the thread reporting the stop event is stopped. That is,
34654 when reporting a @samp{S} or @samp{T} response to indicate completion
34655 of a step operation, hitting a breakpoint, or a fault, only the
34656 affected thread is stopped; any other still-running threads continue
34657 to run. When reporting a @samp{W} or @samp{X} response, all running
34658 threads belonging to other attached processes continue to run.
34660 Only one stop reply notification at a time may be pending; if
34661 additional stop events occur before @value{GDBN} has acknowledged the
34662 previous notification, they must be queued by the stub for later
34663 synchronous transmission in response to @samp{vStopped} packets from
34664 @value{GDBN}. Because the notification mechanism is unreliable,
34665 the stub is permitted to resend a stop reply notification
34666 if it believes @value{GDBN} may not have received it. @value{GDBN}
34667 ignores additional stop reply notifications received before it has
34668 finished processing a previous notification and the stub has completed
34669 sending any queued stop events.
34671 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34672 notification at any time. Specifically, they may appear when
34673 @value{GDBN} is not otherwise reading input from the stub, or when
34674 @value{GDBN} is expecting to read a normal synchronous response or a
34675 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34676 Notification packets are distinct from any other communication from
34677 the stub so there is no ambiguity.
34679 After receiving a stop reply notification, @value{GDBN} shall
34680 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34681 as a regular, synchronous request to the stub. Such acknowledgment
34682 is not required to happen immediately, as @value{GDBN} is permitted to
34683 send other, unrelated packets to the stub first, which the stub should
34686 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34687 stop events to report to @value{GDBN}, it shall respond by sending a
34688 normal stop reply response. @value{GDBN} shall then send another
34689 @samp{vStopped} packet to solicit further responses; again, it is
34690 permitted to send other, unrelated packets as well which the stub
34691 should process normally.
34693 If the stub receives a @samp{vStopped} packet and there are no
34694 additional stop events to report, the stub shall return an @samp{OK}
34695 response. At this point, if further stop events occur, the stub shall
34696 send a new stop reply notification, @value{GDBN} shall accept the
34697 notification, and the process shall be repeated.
34699 In non-stop mode, the target shall respond to the @samp{?} packet as
34700 follows. First, any incomplete stop reply notification/@samp{vStopped}
34701 sequence in progress is abandoned. The target must begin a new
34702 sequence reporting stop events for all stopped threads, whether or not
34703 it has previously reported those events to @value{GDBN}. The first
34704 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34705 subsequent stop replies are sent as responses to @samp{vStopped} packets
34706 using the mechanism described above. The target must not send
34707 asynchronous stop reply notifications until the sequence is complete.
34708 If all threads are running when the target receives the @samp{?} packet,
34709 or if the target is not attached to any process, it shall respond
34712 @node Packet Acknowledgment
34713 @section Packet Acknowledgment
34715 @cindex acknowledgment, for @value{GDBN} remote
34716 @cindex packet acknowledgment, for @value{GDBN} remote
34717 By default, when either the host or the target machine receives a packet,
34718 the first response expected is an acknowledgment: either @samp{+} (to indicate
34719 the package was received correctly) or @samp{-} (to request retransmission).
34720 This mechanism allows the @value{GDBN} remote protocol to operate over
34721 unreliable transport mechanisms, such as a serial line.
34723 In cases where the transport mechanism is itself reliable (such as a pipe or
34724 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34725 It may be desirable to disable them in that case to reduce communication
34726 overhead, or for other reasons. This can be accomplished by means of the
34727 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34729 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34730 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34731 and response format still includes the normal checksum, as described in
34732 @ref{Overview}, but the checksum may be ignored by the receiver.
34734 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34735 no-acknowledgment mode, it should report that to @value{GDBN}
34736 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34737 @pxref{qSupported}.
34738 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34739 disabled via the @code{set remote noack-packet off} command
34740 (@pxref{Remote Configuration}),
34741 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34742 Only then may the stub actually turn off packet acknowledgments.
34743 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34744 response, which can be safely ignored by the stub.
34746 Note that @code{set remote noack-packet} command only affects negotiation
34747 between @value{GDBN} and the stub when subsequent connections are made;
34748 it does not affect the protocol acknowledgment state for any current
34750 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34751 new connection is established,
34752 there is also no protocol request to re-enable the acknowledgments
34753 for the current connection, once disabled.
34758 Example sequence of a target being re-started. Notice how the restart
34759 does not get any direct output:
34764 @emph{target restarts}
34767 <- @code{T001:1234123412341234}
34771 Example sequence of a target being stepped by a single instruction:
34774 -> @code{G1445@dots{}}
34779 <- @code{T001:1234123412341234}
34783 <- @code{1455@dots{}}
34787 @node File-I/O Remote Protocol Extension
34788 @section File-I/O Remote Protocol Extension
34789 @cindex File-I/O remote protocol extension
34792 * File-I/O Overview::
34793 * Protocol Basics::
34794 * The F Request Packet::
34795 * The F Reply Packet::
34796 * The Ctrl-C Message::
34798 * List of Supported Calls::
34799 * Protocol-specific Representation of Datatypes::
34801 * File-I/O Examples::
34804 @node File-I/O Overview
34805 @subsection File-I/O Overview
34806 @cindex file-i/o overview
34808 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34809 target to use the host's file system and console I/O to perform various
34810 system calls. System calls on the target system are translated into a
34811 remote protocol packet to the host system, which then performs the needed
34812 actions and returns a response packet to the target system.
34813 This simulates file system operations even on targets that lack file systems.
34815 The protocol is defined to be independent of both the host and target systems.
34816 It uses its own internal representation of datatypes and values. Both
34817 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34818 translating the system-dependent value representations into the internal
34819 protocol representations when data is transmitted.
34821 The communication is synchronous. A system call is possible only when
34822 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34823 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34824 the target is stopped to allow deterministic access to the target's
34825 memory. Therefore File-I/O is not interruptible by target signals. On
34826 the other hand, it is possible to interrupt File-I/O by a user interrupt
34827 (@samp{Ctrl-C}) within @value{GDBN}.
34829 The target's request to perform a host system call does not finish
34830 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34831 after finishing the system call, the target returns to continuing the
34832 previous activity (continue, step). No additional continue or step
34833 request from @value{GDBN} is required.
34836 (@value{GDBP}) continue
34837 <- target requests 'system call X'
34838 target is stopped, @value{GDBN} executes system call
34839 -> @value{GDBN} returns result
34840 ... target continues, @value{GDBN} returns to wait for the target
34841 <- target hits breakpoint and sends a Txx packet
34844 The protocol only supports I/O on the console and to regular files on
34845 the host file system. Character or block special devices, pipes,
34846 named pipes, sockets or any other communication method on the host
34847 system are not supported by this protocol.
34849 File I/O is not supported in non-stop mode.
34851 @node Protocol Basics
34852 @subsection Protocol Basics
34853 @cindex protocol basics, file-i/o
34855 The File-I/O protocol uses the @code{F} packet as the request as well
34856 as reply packet. Since a File-I/O system call can only occur when
34857 @value{GDBN} is waiting for a response from the continuing or stepping target,
34858 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34859 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34860 This @code{F} packet contains all information needed to allow @value{GDBN}
34861 to call the appropriate host system call:
34865 A unique identifier for the requested system call.
34868 All parameters to the system call. Pointers are given as addresses
34869 in the target memory address space. Pointers to strings are given as
34870 pointer/length pair. Numerical values are given as they are.
34871 Numerical control flags are given in a protocol-specific representation.
34875 At this point, @value{GDBN} has to perform the following actions.
34879 If the parameters include pointer values to data needed as input to a
34880 system call, @value{GDBN} requests this data from the target with a
34881 standard @code{m} packet request. This additional communication has to be
34882 expected by the target implementation and is handled as any other @code{m}
34886 @value{GDBN} translates all value from protocol representation to host
34887 representation as needed. Datatypes are coerced into the host types.
34890 @value{GDBN} calls the system call.
34893 It then coerces datatypes back to protocol representation.
34896 If the system call is expected to return data in buffer space specified
34897 by pointer parameters to the call, the data is transmitted to the
34898 target using a @code{M} or @code{X} packet. This packet has to be expected
34899 by the target implementation and is handled as any other @code{M} or @code{X}
34904 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34905 necessary information for the target to continue. This at least contains
34912 @code{errno}, if has been changed by the system call.
34919 After having done the needed type and value coercion, the target continues
34920 the latest continue or step action.
34922 @node The F Request Packet
34923 @subsection The @code{F} Request Packet
34924 @cindex file-i/o request packet
34925 @cindex @code{F} request packet
34927 The @code{F} request packet has the following format:
34930 @item F@var{call-id},@var{parameter@dots{}}
34932 @var{call-id} is the identifier to indicate the host system call to be called.
34933 This is just the name of the function.
34935 @var{parameter@dots{}} are the parameters to the system call.
34936 Parameters are hexadecimal integer values, either the actual values in case
34937 of scalar datatypes, pointers to target buffer space in case of compound
34938 datatypes and unspecified memory areas, or pointer/length pairs in case
34939 of string parameters. These are appended to the @var{call-id} as a
34940 comma-delimited list. All values are transmitted in ASCII
34941 string representation, pointer/length pairs separated by a slash.
34947 @node The F Reply Packet
34948 @subsection The @code{F} Reply Packet
34949 @cindex file-i/o reply packet
34950 @cindex @code{F} reply packet
34952 The @code{F} reply packet has the following format:
34956 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34958 @var{retcode} is the return code of the system call as hexadecimal value.
34960 @var{errno} is the @code{errno} set by the call, in protocol-specific
34962 This parameter can be omitted if the call was successful.
34964 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34965 case, @var{errno} must be sent as well, even if the call was successful.
34966 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34973 or, if the call was interrupted before the host call has been performed:
34980 assuming 4 is the protocol-specific representation of @code{EINTR}.
34985 @node The Ctrl-C Message
34986 @subsection The @samp{Ctrl-C} Message
34987 @cindex ctrl-c message, in file-i/o protocol
34989 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
34990 reply packet (@pxref{The F Reply Packet}),
34991 the target should behave as if it had
34992 gotten a break message. The meaning for the target is ``system call
34993 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
34994 (as with a break message) and return to @value{GDBN} with a @code{T02}
34997 It's important for the target to know in which
34998 state the system call was interrupted. There are two possible cases:
35002 The system call hasn't been performed on the host yet.
35005 The system call on the host has been finished.
35009 These two states can be distinguished by the target by the value of the
35010 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35011 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35012 on POSIX systems. In any other case, the target may presume that the
35013 system call has been finished --- successfully or not --- and should behave
35014 as if the break message arrived right after the system call.
35016 @value{GDBN} must behave reliably. If the system call has not been called
35017 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35018 @code{errno} in the packet. If the system call on the host has been finished
35019 before the user requests a break, the full action must be finished by
35020 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35021 The @code{F} packet may only be sent when either nothing has happened
35022 or the full action has been completed.
35025 @subsection Console I/O
35026 @cindex console i/o as part of file-i/o
35028 By default and if not explicitly closed by the target system, the file
35029 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35030 on the @value{GDBN} console is handled as any other file output operation
35031 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35032 by @value{GDBN} so that after the target read request from file descriptor
35033 0 all following typing is buffered until either one of the following
35038 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35040 system call is treated as finished.
35043 The user presses @key{RET}. This is treated as end of input with a trailing
35047 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35048 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35052 If the user has typed more characters than fit in the buffer given to
35053 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35054 either another @code{read(0, @dots{})} is requested by the target, or debugging
35055 is stopped at the user's request.
35058 @node List of Supported Calls
35059 @subsection List of Supported Calls
35060 @cindex list of supported file-i/o calls
35077 @unnumberedsubsubsec open
35078 @cindex open, file-i/o system call
35083 int open(const char *pathname, int flags);
35084 int open(const char *pathname, int flags, mode_t mode);
35088 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35091 @var{flags} is the bitwise @code{OR} of the following values:
35095 If the file does not exist it will be created. The host
35096 rules apply as far as file ownership and time stamps
35100 When used with @code{O_CREAT}, if the file already exists it is
35101 an error and open() fails.
35104 If the file already exists and the open mode allows
35105 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35106 truncated to zero length.
35109 The file is opened in append mode.
35112 The file is opened for reading only.
35115 The file is opened for writing only.
35118 The file is opened for reading and writing.
35122 Other bits are silently ignored.
35126 @var{mode} is the bitwise @code{OR} of the following values:
35130 User has read permission.
35133 User has write permission.
35136 Group has read permission.
35139 Group has write permission.
35142 Others have read permission.
35145 Others have write permission.
35149 Other bits are silently ignored.
35152 @item Return value:
35153 @code{open} returns the new file descriptor or -1 if an error
35160 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35163 @var{pathname} refers to a directory.
35166 The requested access is not allowed.
35169 @var{pathname} was too long.
35172 A directory component in @var{pathname} does not exist.
35175 @var{pathname} refers to a device, pipe, named pipe or socket.
35178 @var{pathname} refers to a file on a read-only filesystem and
35179 write access was requested.
35182 @var{pathname} is an invalid pointer value.
35185 No space on device to create the file.
35188 The process already has the maximum number of files open.
35191 The limit on the total number of files open on the system
35195 The call was interrupted by the user.
35201 @unnumberedsubsubsec close
35202 @cindex close, file-i/o system call
35211 @samp{Fclose,@var{fd}}
35213 @item Return value:
35214 @code{close} returns zero on success, or -1 if an error occurred.
35220 @var{fd} isn't a valid open file descriptor.
35223 The call was interrupted by the user.
35229 @unnumberedsubsubsec read
35230 @cindex read, file-i/o system call
35235 int read(int fd, void *buf, unsigned int count);
35239 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35241 @item Return value:
35242 On success, the number of bytes read is returned.
35243 Zero indicates end of file. If count is zero, read
35244 returns zero as well. On error, -1 is returned.
35250 @var{fd} is not a valid file descriptor or is not open for
35254 @var{bufptr} is an invalid pointer value.
35257 The call was interrupted by the user.
35263 @unnumberedsubsubsec write
35264 @cindex write, file-i/o system call
35269 int write(int fd, const void *buf, unsigned int count);
35273 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35275 @item Return value:
35276 On success, the number of bytes written are returned.
35277 Zero indicates nothing was written. On error, -1
35284 @var{fd} is not a valid file descriptor or is not open for
35288 @var{bufptr} is an invalid pointer value.
35291 An attempt was made to write a file that exceeds the
35292 host-specific maximum file size allowed.
35295 No space on device to write the data.
35298 The call was interrupted by the user.
35304 @unnumberedsubsubsec lseek
35305 @cindex lseek, file-i/o system call
35310 long lseek (int fd, long offset, int flag);
35314 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35316 @var{flag} is one of:
35320 The offset is set to @var{offset} bytes.
35323 The offset is set to its current location plus @var{offset}
35327 The offset is set to the size of the file plus @var{offset}
35331 @item Return value:
35332 On success, the resulting unsigned offset in bytes from
35333 the beginning of the file is returned. Otherwise, a
35334 value of -1 is returned.
35340 @var{fd} is not a valid open file descriptor.
35343 @var{fd} is associated with the @value{GDBN} console.
35346 @var{flag} is not a proper value.
35349 The call was interrupted by the user.
35355 @unnumberedsubsubsec rename
35356 @cindex rename, file-i/o system call
35361 int rename(const char *oldpath, const char *newpath);
35365 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35367 @item Return value:
35368 On success, zero is returned. On error, -1 is returned.
35374 @var{newpath} is an existing directory, but @var{oldpath} is not a
35378 @var{newpath} is a non-empty directory.
35381 @var{oldpath} or @var{newpath} is a directory that is in use by some
35385 An attempt was made to make a directory a subdirectory
35389 A component used as a directory in @var{oldpath} or new
35390 path is not a directory. Or @var{oldpath} is a directory
35391 and @var{newpath} exists but is not a directory.
35394 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35397 No access to the file or the path of the file.
35401 @var{oldpath} or @var{newpath} was too long.
35404 A directory component in @var{oldpath} or @var{newpath} does not exist.
35407 The file is on a read-only filesystem.
35410 The device containing the file has no room for the new
35414 The call was interrupted by the user.
35420 @unnumberedsubsubsec unlink
35421 @cindex unlink, file-i/o system call
35426 int unlink(const char *pathname);
35430 @samp{Funlink,@var{pathnameptr}/@var{len}}
35432 @item Return value:
35433 On success, zero is returned. On error, -1 is returned.
35439 No access to the file or the path of the file.
35442 The system does not allow unlinking of directories.
35445 The file @var{pathname} cannot be unlinked because it's
35446 being used by another process.
35449 @var{pathnameptr} is an invalid pointer value.
35452 @var{pathname} was too long.
35455 A directory component in @var{pathname} does not exist.
35458 A component of the path is not a directory.
35461 The file is on a read-only filesystem.
35464 The call was interrupted by the user.
35470 @unnumberedsubsubsec stat/fstat
35471 @cindex fstat, file-i/o system call
35472 @cindex stat, file-i/o system call
35477 int stat(const char *pathname, struct stat *buf);
35478 int fstat(int fd, struct stat *buf);
35482 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35483 @samp{Ffstat,@var{fd},@var{bufptr}}
35485 @item Return value:
35486 On success, zero is returned. On error, -1 is returned.
35492 @var{fd} is not a valid open file.
35495 A directory component in @var{pathname} does not exist or the
35496 path is an empty string.
35499 A component of the path is not a directory.
35502 @var{pathnameptr} is an invalid pointer value.
35505 No access to the file or the path of the file.
35508 @var{pathname} was too long.
35511 The call was interrupted by the user.
35517 @unnumberedsubsubsec gettimeofday
35518 @cindex gettimeofday, file-i/o system call
35523 int gettimeofday(struct timeval *tv, void *tz);
35527 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35529 @item Return value:
35530 On success, 0 is returned, -1 otherwise.
35536 @var{tz} is a non-NULL pointer.
35539 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35545 @unnumberedsubsubsec isatty
35546 @cindex isatty, file-i/o system call
35551 int isatty(int fd);
35555 @samp{Fisatty,@var{fd}}
35557 @item Return value:
35558 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35564 The call was interrupted by the user.
35569 Note that the @code{isatty} call is treated as a special case: it returns
35570 1 to the target if the file descriptor is attached
35571 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35572 would require implementing @code{ioctl} and would be more complex than
35577 @unnumberedsubsubsec system
35578 @cindex system, file-i/o system call
35583 int system(const char *command);
35587 @samp{Fsystem,@var{commandptr}/@var{len}}
35589 @item Return value:
35590 If @var{len} is zero, the return value indicates whether a shell is
35591 available. A zero return value indicates a shell is not available.
35592 For non-zero @var{len}, the value returned is -1 on error and the
35593 return status of the command otherwise. Only the exit status of the
35594 command is returned, which is extracted from the host's @code{system}
35595 return value by calling @code{WEXITSTATUS(retval)}. In case
35596 @file{/bin/sh} could not be executed, 127 is returned.
35602 The call was interrupted by the user.
35607 @value{GDBN} takes over the full task of calling the necessary host calls
35608 to perform the @code{system} call. The return value of @code{system} on
35609 the host is simplified before it's returned
35610 to the target. Any termination signal information from the child process
35611 is discarded, and the return value consists
35612 entirely of the exit status of the called command.
35614 Due to security concerns, the @code{system} call is by default refused
35615 by @value{GDBN}. The user has to allow this call explicitly with the
35616 @code{set remote system-call-allowed 1} command.
35619 @item set remote system-call-allowed
35620 @kindex set remote system-call-allowed
35621 Control whether to allow the @code{system} calls in the File I/O
35622 protocol for the remote target. The default is zero (disabled).
35624 @item show remote system-call-allowed
35625 @kindex show remote system-call-allowed
35626 Show whether the @code{system} calls are allowed in the File I/O
35630 @node Protocol-specific Representation of Datatypes
35631 @subsection Protocol-specific Representation of Datatypes
35632 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35635 * Integral Datatypes::
35637 * Memory Transfer::
35642 @node Integral Datatypes
35643 @unnumberedsubsubsec Integral Datatypes
35644 @cindex integral datatypes, in file-i/o protocol
35646 The integral datatypes used in the system calls are @code{int},
35647 @code{unsigned int}, @code{long}, @code{unsigned long},
35648 @code{mode_t}, and @code{time_t}.
35650 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35651 implemented as 32 bit values in this protocol.
35653 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35655 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35656 in @file{limits.h}) to allow range checking on host and target.
35658 @code{time_t} datatypes are defined as seconds since the Epoch.
35660 All integral datatypes transferred as part of a memory read or write of a
35661 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35664 @node Pointer Values
35665 @unnumberedsubsubsec Pointer Values
35666 @cindex pointer values, in file-i/o protocol
35668 Pointers to target data are transmitted as they are. An exception
35669 is made for pointers to buffers for which the length isn't
35670 transmitted as part of the function call, namely strings. Strings
35671 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35678 which is a pointer to data of length 18 bytes at position 0x1aaf.
35679 The length is defined as the full string length in bytes, including
35680 the trailing null byte. For example, the string @code{"hello world"}
35681 at address 0x123456 is transmitted as
35687 @node Memory Transfer
35688 @unnumberedsubsubsec Memory Transfer
35689 @cindex memory transfer, in file-i/o protocol
35691 Structured data which is transferred using a memory read or write (for
35692 example, a @code{struct stat}) is expected to be in a protocol-specific format
35693 with all scalar multibyte datatypes being big endian. Translation to
35694 this representation needs to be done both by the target before the @code{F}
35695 packet is sent, and by @value{GDBN} before
35696 it transfers memory to the target. Transferred pointers to structured
35697 data should point to the already-coerced data at any time.
35701 @unnumberedsubsubsec struct stat
35702 @cindex struct stat, in file-i/o protocol
35704 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35705 is defined as follows:
35709 unsigned int st_dev; /* device */
35710 unsigned int st_ino; /* inode */
35711 mode_t st_mode; /* protection */
35712 unsigned int st_nlink; /* number of hard links */
35713 unsigned int st_uid; /* user ID of owner */
35714 unsigned int st_gid; /* group ID of owner */
35715 unsigned int st_rdev; /* device type (if inode device) */
35716 unsigned long st_size; /* total size, in bytes */
35717 unsigned long st_blksize; /* blocksize for filesystem I/O */
35718 unsigned long st_blocks; /* number of blocks allocated */
35719 time_t st_atime; /* time of last access */
35720 time_t st_mtime; /* time of last modification */
35721 time_t st_ctime; /* time of last change */
35725 The integral datatypes conform to the definitions given in the
35726 appropriate section (see @ref{Integral Datatypes}, for details) so this
35727 structure is of size 64 bytes.
35729 The values of several fields have a restricted meaning and/or
35735 A value of 0 represents a file, 1 the console.
35738 No valid meaning for the target. Transmitted unchanged.
35741 Valid mode bits are described in @ref{Constants}. Any other
35742 bits have currently no meaning for the target.
35747 No valid meaning for the target. Transmitted unchanged.
35752 These values have a host and file system dependent
35753 accuracy. Especially on Windows hosts, the file system may not
35754 support exact timing values.
35757 The target gets a @code{struct stat} of the above representation and is
35758 responsible for coercing it to the target representation before
35761 Note that due to size differences between the host, target, and protocol
35762 representations of @code{struct stat} members, these members could eventually
35763 get truncated on the target.
35765 @node struct timeval
35766 @unnumberedsubsubsec struct timeval
35767 @cindex struct timeval, in file-i/o protocol
35769 The buffer of type @code{struct timeval} used by the File-I/O protocol
35770 is defined as follows:
35774 time_t tv_sec; /* second */
35775 long tv_usec; /* microsecond */
35779 The integral datatypes conform to the definitions given in the
35780 appropriate section (see @ref{Integral Datatypes}, for details) so this
35781 structure is of size 8 bytes.
35784 @subsection Constants
35785 @cindex constants, in file-i/o protocol
35787 The following values are used for the constants inside of the
35788 protocol. @value{GDBN} and target are responsible for translating these
35789 values before and after the call as needed.
35800 @unnumberedsubsubsec Open Flags
35801 @cindex open flags, in file-i/o protocol
35803 All values are given in hexadecimal representation.
35815 @node mode_t Values
35816 @unnumberedsubsubsec mode_t Values
35817 @cindex mode_t values, in file-i/o protocol
35819 All values are given in octal representation.
35836 @unnumberedsubsubsec Errno Values
35837 @cindex errno values, in file-i/o protocol
35839 All values are given in decimal representation.
35864 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35865 any error value not in the list of supported error numbers.
35868 @unnumberedsubsubsec Lseek Flags
35869 @cindex lseek flags, in file-i/o protocol
35878 @unnumberedsubsubsec Limits
35879 @cindex limits, in file-i/o protocol
35881 All values are given in decimal representation.
35884 INT_MIN -2147483648
35886 UINT_MAX 4294967295
35887 LONG_MIN -9223372036854775808
35888 LONG_MAX 9223372036854775807
35889 ULONG_MAX 18446744073709551615
35892 @node File-I/O Examples
35893 @subsection File-I/O Examples
35894 @cindex file-i/o examples
35896 Example sequence of a write call, file descriptor 3, buffer is at target
35897 address 0x1234, 6 bytes should be written:
35900 <- @code{Fwrite,3,1234,6}
35901 @emph{request memory read from target}
35904 @emph{return "6 bytes written"}
35908 Example sequence of a read call, file descriptor 3, buffer is at target
35909 address 0x1234, 6 bytes should be read:
35912 <- @code{Fread,3,1234,6}
35913 @emph{request memory write to target}
35914 -> @code{X1234,6:XXXXXX}
35915 @emph{return "6 bytes read"}
35919 Example sequence of a read call, call fails on the host due to invalid
35920 file descriptor (@code{EBADF}):
35923 <- @code{Fread,3,1234,6}
35927 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35931 <- @code{Fread,3,1234,6}
35936 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35940 <- @code{Fread,3,1234,6}
35941 -> @code{X1234,6:XXXXXX}
35945 @node Library List Format
35946 @section Library List Format
35947 @cindex library list format, remote protocol
35949 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35950 same process as your application to manage libraries. In this case,
35951 @value{GDBN} can use the loader's symbol table and normal memory
35952 operations to maintain a list of shared libraries. On other
35953 platforms, the operating system manages loaded libraries.
35954 @value{GDBN} can not retrieve the list of currently loaded libraries
35955 through memory operations, so it uses the @samp{qXfer:libraries:read}
35956 packet (@pxref{qXfer library list read}) instead. The remote stub
35957 queries the target's operating system and reports which libraries
35960 The @samp{qXfer:libraries:read} packet returns an XML document which
35961 lists loaded libraries and their offsets. Each library has an
35962 associated name and one or more segment or section base addresses,
35963 which report where the library was loaded in memory.
35965 For the common case of libraries that are fully linked binaries, the
35966 library should have a list of segments. If the target supports
35967 dynamic linking of a relocatable object file, its library XML element
35968 should instead include a list of allocated sections. The segment or
35969 section bases are start addresses, not relocation offsets; they do not
35970 depend on the library's link-time base addresses.
35972 @value{GDBN} must be linked with the Expat library to support XML
35973 library lists. @xref{Expat}.
35975 A simple memory map, with one loaded library relocated by a single
35976 offset, looks like this:
35980 <library name="/lib/libc.so.6">
35981 <segment address="0x10000000"/>
35986 Another simple memory map, with one loaded library with three
35987 allocated sections (.text, .data, .bss), looks like this:
35991 <library name="sharedlib.o">
35992 <section address="0x10000000"/>
35993 <section address="0x20000000"/>
35994 <section address="0x30000000"/>
35999 The format of a library list is described by this DTD:
36002 <!-- library-list: Root element with versioning -->
36003 <!ELEMENT library-list (library)*>
36004 <!ATTLIST library-list version CDATA #FIXED "1.0">
36005 <!ELEMENT library (segment*, section*)>
36006 <!ATTLIST library name CDATA #REQUIRED>
36007 <!ELEMENT segment EMPTY>
36008 <!ATTLIST segment address CDATA #REQUIRED>
36009 <!ELEMENT section EMPTY>
36010 <!ATTLIST section address CDATA #REQUIRED>
36013 In addition, segments and section descriptors cannot be mixed within a
36014 single library element, and you must supply at least one segment or
36015 section for each library.
36017 @node Memory Map Format
36018 @section Memory Map Format
36019 @cindex memory map format
36021 To be able to write into flash memory, @value{GDBN} needs to obtain a
36022 memory map from the target. This section describes the format of the
36025 The memory map is obtained using the @samp{qXfer:memory-map:read}
36026 (@pxref{qXfer memory map read}) packet and is an XML document that
36027 lists memory regions.
36029 @value{GDBN} must be linked with the Expat library to support XML
36030 memory maps. @xref{Expat}.
36032 The top-level structure of the document is shown below:
36035 <?xml version="1.0"?>
36036 <!DOCTYPE memory-map
36037 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36038 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36044 Each region can be either:
36049 A region of RAM starting at @var{addr} and extending for @var{length}
36053 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36058 A region of read-only memory:
36061 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36066 A region of flash memory, with erasure blocks @var{blocksize}
36070 <memory type="flash" start="@var{addr}" length="@var{length}">
36071 <property name="blocksize">@var{blocksize}</property>
36077 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36078 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36079 packets to write to addresses in such ranges.
36081 The formal DTD for memory map format is given below:
36084 <!-- ................................................... -->
36085 <!-- Memory Map XML DTD ................................ -->
36086 <!-- File: memory-map.dtd .............................. -->
36087 <!-- .................................... .............. -->
36088 <!-- memory-map.dtd -->
36089 <!-- memory-map: Root element with versioning -->
36090 <!ELEMENT memory-map (memory | property)>
36091 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36092 <!ELEMENT memory (property)>
36093 <!-- memory: Specifies a memory region,
36094 and its type, or device. -->
36095 <!ATTLIST memory type CDATA #REQUIRED
36096 start CDATA #REQUIRED
36097 length CDATA #REQUIRED
36098 device CDATA #IMPLIED>
36099 <!-- property: Generic attribute tag -->
36100 <!ELEMENT property (#PCDATA | property)*>
36101 <!ATTLIST property name CDATA #REQUIRED>
36104 @node Thread List Format
36105 @section Thread List Format
36106 @cindex thread list format
36108 To efficiently update the list of threads and their attributes,
36109 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36110 (@pxref{qXfer threads read}) and obtains the XML document with
36111 the following structure:
36114 <?xml version="1.0"?>
36116 <thread id="id" core="0">
36117 ... description ...
36122 Each @samp{thread} element must have the @samp{id} attribute that
36123 identifies the thread (@pxref{thread-id syntax}). The
36124 @samp{core} attribute, if present, specifies which processor core
36125 the thread was last executing on. The content of the of @samp{thread}
36126 element is interpreted as human-readable auxilliary information.
36128 @node Traceframe Info Format
36129 @section Traceframe Info Format
36130 @cindex traceframe info format
36132 To be able to know which objects in the inferior can be examined when
36133 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36134 memory ranges, registers and trace state variables that have been
36135 collected in a traceframe.
36137 This list is obtained using the @samp{qXfer:traceframe-info:read}
36138 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36140 @value{GDBN} must be linked with the Expat library to support XML
36141 traceframe info discovery. @xref{Expat}.
36143 The top-level structure of the document is shown below:
36146 <?xml version="1.0"?>
36147 <!DOCTYPE traceframe-info
36148 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36149 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36155 Each traceframe block can be either:
36160 A region of collected memory starting at @var{addr} and extending for
36161 @var{length} bytes from there:
36164 <memory start="@var{addr}" length="@var{length}"/>
36169 The formal DTD for the traceframe info format is given below:
36172 <!ELEMENT traceframe-info (memory)* >
36173 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36175 <!ELEMENT memory EMPTY>
36176 <!ATTLIST memory start CDATA #REQUIRED
36177 length CDATA #REQUIRED>
36180 @include agentexpr.texi
36182 @node Trace File Format
36183 @appendix Trace File Format
36184 @cindex trace file format
36186 The trace file comes in three parts: a header, a textual description
36187 section, and a trace frame section with binary data.
36189 The header has the form @code{\x7fTRACE0\n}. The first byte is
36190 @code{0x7f} so as to indicate that the file contains binary data,
36191 while the @code{0} is a version number that may have different values
36194 The description section consists of multiple lines of @sc{ascii} text
36195 separated by newline characters (@code{0xa}). The lines may include a
36196 variety of optional descriptive or context-setting information, such
36197 as tracepoint definitions or register set size. @value{GDBN} will
36198 ignore any line that it does not recognize. An empty line marks the end
36201 @c FIXME add some specific types of data
36203 The trace frame section consists of a number of consecutive frames.
36204 Each frame begins with a two-byte tracepoint number, followed by a
36205 four-byte size giving the amount of data in the frame. The data in
36206 the frame consists of a number of blocks, each introduced by a
36207 character indicating its type (at least register, memory, and trace
36208 state variable). The data in this section is raw binary, not a
36209 hexadecimal or other encoding; its endianness matches the target's
36212 @c FIXME bi-arch may require endianness/arch info in description section
36215 @item R @var{bytes}
36216 Register block. The number and ordering of bytes matches that of a
36217 @code{g} packet in the remote protocol. Note that these are the
36218 actual bytes, in target order and @value{GDBN} register order, not a
36219 hexadecimal encoding.
36221 @item M @var{address} @var{length} @var{bytes}...
36222 Memory block. This is a contiguous block of memory, at the 8-byte
36223 address @var{address}, with a 2-byte length @var{length}, followed by
36224 @var{length} bytes.
36226 @item V @var{number} @var{value}
36227 Trace state variable block. This records the 8-byte signed value
36228 @var{value} of trace state variable numbered @var{number}.
36232 Future enhancements of the trace file format may include additional types
36235 @node Target Descriptions
36236 @appendix Target Descriptions
36237 @cindex target descriptions
36239 @strong{Warning:} target descriptions are still under active development,
36240 and the contents and format may change between @value{GDBN} releases.
36241 The format is expected to stabilize in the future.
36243 One of the challenges of using @value{GDBN} to debug embedded systems
36244 is that there are so many minor variants of each processor
36245 architecture in use. It is common practice for vendors to start with
36246 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36247 and then make changes to adapt it to a particular market niche. Some
36248 architectures have hundreds of variants, available from dozens of
36249 vendors. This leads to a number of problems:
36253 With so many different customized processors, it is difficult for
36254 the @value{GDBN} maintainers to keep up with the changes.
36256 Since individual variants may have short lifetimes or limited
36257 audiences, it may not be worthwhile to carry information about every
36258 variant in the @value{GDBN} source tree.
36260 When @value{GDBN} does support the architecture of the embedded system
36261 at hand, the task of finding the correct architecture name to give the
36262 @command{set architecture} command can be error-prone.
36265 To address these problems, the @value{GDBN} remote protocol allows a
36266 target system to not only identify itself to @value{GDBN}, but to
36267 actually describe its own features. This lets @value{GDBN} support
36268 processor variants it has never seen before --- to the extent that the
36269 descriptions are accurate, and that @value{GDBN} understands them.
36271 @value{GDBN} must be linked with the Expat library to support XML
36272 target descriptions. @xref{Expat}.
36275 * Retrieving Descriptions:: How descriptions are fetched from a target.
36276 * Target Description Format:: The contents of a target description.
36277 * Predefined Target Types:: Standard types available for target
36279 * Standard Target Features:: Features @value{GDBN} knows about.
36282 @node Retrieving Descriptions
36283 @section Retrieving Descriptions
36285 Target descriptions can be read from the target automatically, or
36286 specified by the user manually. The default behavior is to read the
36287 description from the target. @value{GDBN} retrieves it via the remote
36288 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36289 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36290 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36291 XML document, of the form described in @ref{Target Description
36294 Alternatively, you can specify a file to read for the target description.
36295 If a file is set, the target will not be queried. The commands to
36296 specify a file are:
36299 @cindex set tdesc filename
36300 @item set tdesc filename @var{path}
36301 Read the target description from @var{path}.
36303 @cindex unset tdesc filename
36304 @item unset tdesc filename
36305 Do not read the XML target description from a file. @value{GDBN}
36306 will use the description supplied by the current target.
36308 @cindex show tdesc filename
36309 @item show tdesc filename
36310 Show the filename to read for a target description, if any.
36314 @node Target Description Format
36315 @section Target Description Format
36316 @cindex target descriptions, XML format
36318 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36319 document which complies with the Document Type Definition provided in
36320 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36321 means you can use generally available tools like @command{xmllint} to
36322 check that your feature descriptions are well-formed and valid.
36323 However, to help people unfamiliar with XML write descriptions for
36324 their targets, we also describe the grammar here.
36326 Target descriptions can identify the architecture of the remote target
36327 and (for some architectures) provide information about custom register
36328 sets. They can also identify the OS ABI of the remote target.
36329 @value{GDBN} can use this information to autoconfigure for your
36330 target, or to warn you if you connect to an unsupported target.
36332 Here is a simple target description:
36335 <target version="1.0">
36336 <architecture>i386:x86-64</architecture>
36341 This minimal description only says that the target uses
36342 the x86-64 architecture.
36344 A target description has the following overall form, with [ ] marking
36345 optional elements and @dots{} marking repeatable elements. The elements
36346 are explained further below.
36349 <?xml version="1.0"?>
36350 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36351 <target version="1.0">
36352 @r{[}@var{architecture}@r{]}
36353 @r{[}@var{osabi}@r{]}
36354 @r{[}@var{compatible}@r{]}
36355 @r{[}@var{feature}@dots{}@r{]}
36360 The description is generally insensitive to whitespace and line
36361 breaks, under the usual common-sense rules. The XML version
36362 declaration and document type declaration can generally be omitted
36363 (@value{GDBN} does not require them), but specifying them may be
36364 useful for XML validation tools. The @samp{version} attribute for
36365 @samp{<target>} may also be omitted, but we recommend
36366 including it; if future versions of @value{GDBN} use an incompatible
36367 revision of @file{gdb-target.dtd}, they will detect and report
36368 the version mismatch.
36370 @subsection Inclusion
36371 @cindex target descriptions, inclusion
36374 @cindex <xi:include>
36377 It can sometimes be valuable to split a target description up into
36378 several different annexes, either for organizational purposes, or to
36379 share files between different possible target descriptions. You can
36380 divide a description into multiple files by replacing any element of
36381 the target description with an inclusion directive of the form:
36384 <xi:include href="@var{document}"/>
36388 When @value{GDBN} encounters an element of this form, it will retrieve
36389 the named XML @var{document}, and replace the inclusion directive with
36390 the contents of that document. If the current description was read
36391 using @samp{qXfer}, then so will be the included document;
36392 @var{document} will be interpreted as the name of an annex. If the
36393 current description was read from a file, @value{GDBN} will look for
36394 @var{document} as a file in the same directory where it found the
36395 original description.
36397 @subsection Architecture
36398 @cindex <architecture>
36400 An @samp{<architecture>} element has this form:
36403 <architecture>@var{arch}</architecture>
36406 @var{arch} is one of the architectures from the set accepted by
36407 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36410 @cindex @code{<osabi>}
36412 This optional field was introduced in @value{GDBN} version 7.0.
36413 Previous versions of @value{GDBN} ignore it.
36415 An @samp{<osabi>} element has this form:
36418 <osabi>@var{abi-name}</osabi>
36421 @var{abi-name} is an OS ABI name from the same selection accepted by
36422 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36424 @subsection Compatible Architecture
36425 @cindex @code{<compatible>}
36427 This optional field was introduced in @value{GDBN} version 7.0.
36428 Previous versions of @value{GDBN} ignore it.
36430 A @samp{<compatible>} element has this form:
36433 <compatible>@var{arch}</compatible>
36436 @var{arch} is one of the architectures from the set accepted by
36437 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36439 A @samp{<compatible>} element is used to specify that the target
36440 is able to run binaries in some other than the main target architecture
36441 given by the @samp{<architecture>} element. For example, on the
36442 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36443 or @code{powerpc:common64}, but the system is able to run binaries
36444 in the @code{spu} architecture as well. The way to describe this
36445 capability with @samp{<compatible>} is as follows:
36448 <architecture>powerpc:common</architecture>
36449 <compatible>spu</compatible>
36452 @subsection Features
36455 Each @samp{<feature>} describes some logical portion of the target
36456 system. Features are currently used to describe available CPU
36457 registers and the types of their contents. A @samp{<feature>} element
36461 <feature name="@var{name}">
36462 @r{[}@var{type}@dots{}@r{]}
36468 Each feature's name should be unique within the description. The name
36469 of a feature does not matter unless @value{GDBN} has some special
36470 knowledge of the contents of that feature; if it does, the feature
36471 should have its standard name. @xref{Standard Target Features}.
36475 Any register's value is a collection of bits which @value{GDBN} must
36476 interpret. The default interpretation is a two's complement integer,
36477 but other types can be requested by name in the register description.
36478 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36479 Target Types}), and the description can define additional composite types.
36481 Each type element must have an @samp{id} attribute, which gives
36482 a unique (within the containing @samp{<feature>}) name to the type.
36483 Types must be defined before they are used.
36486 Some targets offer vector registers, which can be treated as arrays
36487 of scalar elements. These types are written as @samp{<vector>} elements,
36488 specifying the array element type, @var{type}, and the number of elements,
36492 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36496 If a register's value is usefully viewed in multiple ways, define it
36497 with a union type containing the useful representations. The
36498 @samp{<union>} element contains one or more @samp{<field>} elements,
36499 each of which has a @var{name} and a @var{type}:
36502 <union id="@var{id}">
36503 <field name="@var{name}" type="@var{type}"/>
36509 If a register's value is composed from several separate values, define
36510 it with a structure type. There are two forms of the @samp{<struct>}
36511 element; a @samp{<struct>} element must either contain only bitfields
36512 or contain no bitfields. If the structure contains only bitfields,
36513 its total size in bytes must be specified, each bitfield must have an
36514 explicit start and end, and bitfields are automatically assigned an
36515 integer type. The field's @var{start} should be less than or
36516 equal to its @var{end}, and zero represents the least significant bit.
36519 <struct id="@var{id}" size="@var{size}">
36520 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36525 If the structure contains no bitfields, then each field has an
36526 explicit type, and no implicit padding is added.
36529 <struct id="@var{id}">
36530 <field name="@var{name}" type="@var{type}"/>
36536 If a register's value is a series of single-bit flags, define it with
36537 a flags type. The @samp{<flags>} element has an explicit @var{size}
36538 and contains one or more @samp{<field>} elements. Each field has a
36539 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36543 <flags id="@var{id}" size="@var{size}">
36544 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36549 @subsection Registers
36552 Each register is represented as an element with this form:
36555 <reg name="@var{name}"
36556 bitsize="@var{size}"
36557 @r{[}regnum="@var{num}"@r{]}
36558 @r{[}save-restore="@var{save-restore}"@r{]}
36559 @r{[}type="@var{type}"@r{]}
36560 @r{[}group="@var{group}"@r{]}/>
36564 The components are as follows:
36569 The register's name; it must be unique within the target description.
36572 The register's size, in bits.
36575 The register's number. If omitted, a register's number is one greater
36576 than that of the previous register (either in the current feature or in
36577 a preceeding feature); the first register in the target description
36578 defaults to zero. This register number is used to read or write
36579 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36580 packets, and registers appear in the @code{g} and @code{G} packets
36581 in order of increasing register number.
36584 Whether the register should be preserved across inferior function
36585 calls; this must be either @code{yes} or @code{no}. The default is
36586 @code{yes}, which is appropriate for most registers except for
36587 some system control registers; this is not related to the target's
36591 The type of the register. @var{type} may be a predefined type, a type
36592 defined in the current feature, or one of the special types @code{int}
36593 and @code{float}. @code{int} is an integer type of the correct size
36594 for @var{bitsize}, and @code{float} is a floating point type (in the
36595 architecture's normal floating point format) of the correct size for
36596 @var{bitsize}. The default is @code{int}.
36599 The register group to which this register belongs. @var{group} must
36600 be either @code{general}, @code{float}, or @code{vector}. If no
36601 @var{group} is specified, @value{GDBN} will not display the register
36602 in @code{info registers}.
36606 @node Predefined Target Types
36607 @section Predefined Target Types
36608 @cindex target descriptions, predefined types
36610 Type definitions in the self-description can build up composite types
36611 from basic building blocks, but can not define fundamental types. Instead,
36612 standard identifiers are provided by @value{GDBN} for the fundamental
36613 types. The currently supported types are:
36622 Signed integer types holding the specified number of bits.
36629 Unsigned integer types holding the specified number of bits.
36633 Pointers to unspecified code and data. The program counter and
36634 any dedicated return address register may be marked as code
36635 pointers; printing a code pointer converts it into a symbolic
36636 address. The stack pointer and any dedicated address registers
36637 may be marked as data pointers.
36640 Single precision IEEE floating point.
36643 Double precision IEEE floating point.
36646 The 12-byte extended precision format used by ARM FPA registers.
36649 The 10-byte extended precision format used by x87 registers.
36652 32bit @sc{eflags} register used by x86.
36655 32bit @sc{mxcsr} register used by x86.
36659 @node Standard Target Features
36660 @section Standard Target Features
36661 @cindex target descriptions, standard features
36663 A target description must contain either no registers or all the
36664 target's registers. If the description contains no registers, then
36665 @value{GDBN} will assume a default register layout, selected based on
36666 the architecture. If the description contains any registers, the
36667 default layout will not be used; the standard registers must be
36668 described in the target description, in such a way that @value{GDBN}
36669 can recognize them.
36671 This is accomplished by giving specific names to feature elements
36672 which contain standard registers. @value{GDBN} will look for features
36673 with those names and verify that they contain the expected registers;
36674 if any known feature is missing required registers, or if any required
36675 feature is missing, @value{GDBN} will reject the target
36676 description. You can add additional registers to any of the
36677 standard features --- @value{GDBN} will display them just as if
36678 they were added to an unrecognized feature.
36680 This section lists the known features and their expected contents.
36681 Sample XML documents for these features are included in the
36682 @value{GDBN} source tree, in the directory @file{gdb/features}.
36684 Names recognized by @value{GDBN} should include the name of the
36685 company or organization which selected the name, and the overall
36686 architecture to which the feature applies; so e.g.@: the feature
36687 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36689 The names of registers are not case sensitive for the purpose
36690 of recognizing standard features, but @value{GDBN} will only display
36691 registers using the capitalization used in the description.
36698 * PowerPC Features::
36703 @subsection ARM Features
36704 @cindex target descriptions, ARM features
36706 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36708 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36709 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36711 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36712 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36713 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36716 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36717 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36719 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36720 it should contain at least registers @samp{wR0} through @samp{wR15} and
36721 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36722 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36724 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36725 should contain at least registers @samp{d0} through @samp{d15}. If
36726 they are present, @samp{d16} through @samp{d31} should also be included.
36727 @value{GDBN} will synthesize the single-precision registers from
36728 halves of the double-precision registers.
36730 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36731 need to contain registers; it instructs @value{GDBN} to display the
36732 VFP double-precision registers as vectors and to synthesize the
36733 quad-precision registers from pairs of double-precision registers.
36734 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36735 be present and include 32 double-precision registers.
36737 @node i386 Features
36738 @subsection i386 Features
36739 @cindex target descriptions, i386 features
36741 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36742 targets. It should describe the following registers:
36746 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36748 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36750 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36751 @samp{fs}, @samp{gs}
36753 @samp{st0} through @samp{st7}
36755 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36756 @samp{foseg}, @samp{fooff} and @samp{fop}
36759 The register sets may be different, depending on the target.
36761 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36762 describe registers:
36766 @samp{xmm0} through @samp{xmm7} for i386
36768 @samp{xmm0} through @samp{xmm15} for amd64
36773 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36774 @samp{org.gnu.gdb.i386.sse} feature. It should
36775 describe the upper 128 bits of @sc{ymm} registers:
36779 @samp{ymm0h} through @samp{ymm7h} for i386
36781 @samp{ymm0h} through @samp{ymm15h} for amd64
36784 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36785 describe a single register, @samp{orig_eax}.
36787 @node MIPS Features
36788 @subsection MIPS Features
36789 @cindex target descriptions, MIPS features
36791 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36792 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36793 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36796 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36797 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36798 registers. They may be 32-bit or 64-bit depending on the target.
36800 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36801 it may be optional in a future version of @value{GDBN}. It should
36802 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36803 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36805 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36806 contain a single register, @samp{restart}, which is used by the
36807 Linux kernel to control restartable syscalls.
36809 @node M68K Features
36810 @subsection M68K Features
36811 @cindex target descriptions, M68K features
36814 @item @samp{org.gnu.gdb.m68k.core}
36815 @itemx @samp{org.gnu.gdb.coldfire.core}
36816 @itemx @samp{org.gnu.gdb.fido.core}
36817 One of those features must be always present.
36818 The feature that is present determines which flavor of m68k is
36819 used. The feature that is present should contain registers
36820 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36821 @samp{sp}, @samp{ps} and @samp{pc}.
36823 @item @samp{org.gnu.gdb.coldfire.fp}
36824 This feature is optional. If present, it should contain registers
36825 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36829 @node PowerPC Features
36830 @subsection PowerPC Features
36831 @cindex target descriptions, PowerPC features
36833 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36834 targets. It should contain registers @samp{r0} through @samp{r31},
36835 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36836 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36838 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36839 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36841 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36842 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36845 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36846 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36847 will combine these registers with the floating point registers
36848 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36849 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36850 through @samp{vs63}, the set of vector registers for POWER7.
36852 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36853 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36854 @samp{spefscr}. SPE targets should provide 32-bit registers in
36855 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36856 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36857 these to present registers @samp{ev0} through @samp{ev31} to the
36860 @node Operating System Information
36861 @appendix Operating System Information
36862 @cindex operating system information
36868 Users of @value{GDBN} often wish to obtain information about the state of
36869 the operating system running on the target---for example the list of
36870 processes, or the list of open files. This section describes the
36871 mechanism that makes it possible. This mechanism is similar to the
36872 target features mechanism (@pxref{Target Descriptions}), but focuses
36873 on a different aspect of target.
36875 Operating system information is retrived from the target via the
36876 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36877 read}). The object name in the request should be @samp{osdata}, and
36878 the @var{annex} identifies the data to be fetched.
36881 @appendixsection Process list
36882 @cindex operating system information, process list
36884 When requesting the process list, the @var{annex} field in the
36885 @samp{qXfer} request should be @samp{processes}. The returned data is
36886 an XML document. The formal syntax of this document is defined in
36887 @file{gdb/features/osdata.dtd}.
36889 An example document is:
36892 <?xml version="1.0"?>
36893 <!DOCTYPE target SYSTEM "osdata.dtd">
36894 <osdata type="processes">
36896 <column name="pid">1</column>
36897 <column name="user">root</column>
36898 <column name="command">/sbin/init</column>
36899 <column name="cores">1,2,3</column>
36904 Each item should include a column whose name is @samp{pid}. The value
36905 of that column should identify the process on the target. The
36906 @samp{user} and @samp{command} columns are optional, and will be
36907 displayed by @value{GDBN}. The @samp{cores} column, if present,
36908 should contain a comma-separated list of cores that this process
36909 is running on. Target may provide additional columns,
36910 which @value{GDBN} currently ignores.
36914 @node GNU Free Documentation License
36915 @appendix GNU Free Documentation License
36924 % I think something like @colophon should be in texinfo. In the
36926 \long\def\colophon{\hbox to0pt{}\vfill
36927 \centerline{The body of this manual is set in}
36928 \centerline{\fontname\tenrm,}
36929 \centerline{with headings in {\bf\fontname\tenbf}}
36930 \centerline{and examples in {\tt\fontname\tentt}.}
36931 \centerline{{\it\fontname\tenit\/},}
36932 \centerline{{\bf\fontname\tenbf}, and}
36933 \centerline{{\sl\fontname\tensl\/}}
36934 \centerline{are used for emphasis.}\vfill}
36936 % Blame: doc@cygnus.com, 1991.