* gdb/source.c (source_info): Mention whether the symtab has
[deliverable/binutils-gdb.git] / gdb / doc / gdb.texinfo
CommitLineData
c906108c 1\input texinfo @c -*-texinfo-*-
b6ba6518 2@c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
8a037dd7 3@c 1999, 2000, 2001, 2002
c906108c
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4@c Free Software Foundation, Inc.
5@c
5d161b24 6@c %**start of header
c906108c
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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.
9@setfilename gdb.info
10@c
11@include gdb-cfg.texi
12@c
c906108c 13@settitle Debugging with @value{GDBN}
c906108c
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14@setchapternewpage odd
15@c %**end of header
16
17@iftex
18@c @smallbook
19@c @cropmarks
20@end iftex
21
22@finalout
23@syncodeindex ky cp
24
41afff9a 25@c readline appendices use @vindex, @findex and @ftable,
48e934c6 26@c annotate.texi and gdbmi use @findex.
c906108c 27@syncodeindex vr cp
41afff9a 28@syncodeindex fn cp
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29
30@c !!set GDB manual's edition---not the same as GDB version!
e9c75b65 31@set EDITION Ninth
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32
33@c !!set GDB manual's revision date
959acfd1 34@set DATE December 2001
c906108c 35
6c0e9fb3 36@c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
c906108c 37
c906108c 38@c This is a dir.info fragment to support semi-automated addition of
6d2ebf8b 39@c manuals to an info tree.
96a2c332
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40@dircategory Programming & development tools.
41@direntry
c906108c 42* Gdb: (gdb). The @sc{gnu} debugger.
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43@end direntry
44
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45@ifinfo
46This file documents the @sc{gnu} debugger @value{GDBN}.
47
48
5d161b24 49This is the @value{EDITION} Edition, @value{DATE},
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50of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger}
51for @value{GDBN} Version @value{GDBVN}.
52
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53Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
54 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
c906108c 55
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56Permission is granted to copy, distribute and/or modify this document
57under the terms of the GNU Free Documentation License, Version 1.1 or
58any later version published by the Free Software Foundation; with the
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59Invariant Sections being ``Free Software'' and ``Free Software Needs
60Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
61and with the Back-Cover Texts as in (a) below.
c906108c 62
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63(a) The Free Software Foundation's Back-Cover Text is: ``You have
64freedom to copy and modify this GNU Manual, like GNU software. Copies
65published by the Free Software Foundation raise funds for GNU
66development.''
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67@end ifinfo
68
69@titlepage
70@title Debugging with @value{GDBN}
71@subtitle The @sc{gnu} Source-Level Debugger
c906108c 72@sp 1
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73@subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
74@subtitle @value{DATE}
9e9c5ae7 75@author Richard Stallman, Roland Pesch, Stan Shebs, et al.
c906108c 76@page
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77@tex
78{\parskip=0pt
53a5351d 79\hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
c906108c
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80\hfill {\it Debugging with @value{GDBN}}\par
81\hfill \TeX{}info \texinfoversion\par
82}
83@end tex
53a5351d 84
c906108c 85@vskip 0pt plus 1filll
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86Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
871996, 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
c906108c 88@sp 2
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89Published by the Free Software Foundation @*
9059 Temple Place - Suite 330, @*
91Boston, MA 02111-1307 USA @*
6d2ebf8b 92ISBN 1-882114-77-9 @*
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93
94Permission is granted to copy, distribute and/or modify this document
95under the terms of the GNU Free Documentation License, Version 1.1 or
96any later version published by the Free Software Foundation; with the
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97Invariant Sections being ``Free Software'' and ``Free Software Needs
98Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99and with the Back-Cover Texts as in (a) below.
e9c75b65 100
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101(a) The Free Software Foundation's Back-Cover Text is: ``You have
102freedom to copy and modify this GNU Manual, like GNU software. Copies
103published by the Free Software Foundation raise funds for GNU
104development.''
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105@end titlepage
106@page
107
6c0e9fb3 108@ifnottex
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109@node Top, Summary, (dir), (dir)
110
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111@top Debugging with @value{GDBN}
112
113This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
114
5d161b24 115This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
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116@value{GDBVN}.
117
8a037dd7 118Copyright (C) 1988-2002 Free Software Foundation, Inc.
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119
120@menu
121* Summary:: Summary of @value{GDBN}
122* Sample Session:: A sample @value{GDBN} session
123
124* Invocation:: Getting in and out of @value{GDBN}
125* Commands:: @value{GDBN} commands
126* Running:: Running programs under @value{GDBN}
127* Stopping:: Stopping and continuing
128* Stack:: Examining the stack
129* Source:: Examining source files
130* Data:: Examining data
e2e0bcd1 131* Macros:: Preprocessor Macros
b37052ae 132* Tracepoints:: Debugging remote targets non-intrusively
df0cd8c5 133* Overlays:: Debugging programs that use overlays
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134
135* Languages:: Using @value{GDBN} with different languages
136
137* Symbols:: Examining the symbol table
138* Altering:: Altering execution
139* GDB Files:: @value{GDBN} files
140* Targets:: Specifying a debugging target
6b2f586d 141* Remote Debugging:: Debugging remote programs
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142* Configurations:: Configuration-specific information
143* Controlling GDB:: Controlling @value{GDBN}
144* Sequences:: Canned sequences of commands
c4555f82 145* TUI:: @value{GDBN} Text User Interface
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146* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
147* Annotations:: @value{GDBN}'s annotation interface.
7162c0ca 148* GDB/MI:: @value{GDBN}'s Machine Interface.
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149
150* GDB Bugs:: Reporting bugs in @value{GDBN}
151* Formatting Documentation:: How to format and print @value{GDBN} documentation
152
153* Command Line Editing:: Command Line Editing
154* Using History Interactively:: Using History Interactively
155* Installing GDB:: Installing GDB
eb12ee30 156* Maintenance Commands:: Maintenance Commands
e0ce93ac 157* Remote Protocol:: GDB Remote Serial Protocol
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158* Copying:: GNU General Public License says
159 how you can copy and share GDB
6826cf00 160* GNU Free Documentation License:: The license for this documentation
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161* Index:: Index
162@end menu
163
6c0e9fb3 164@end ifnottex
c906108c 165
449f3b6c 166@contents
449f3b6c 167
6d2ebf8b 168@node Summary
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169@unnumbered Summary of @value{GDBN}
170
171The purpose of a debugger such as @value{GDBN} is to allow you to see what is
172going on ``inside'' another program while it executes---or what another
173program was doing at the moment it crashed.
174
175@value{GDBN} can do four main kinds of things (plus other things in support of
176these) to help you catch bugs in the act:
177
178@itemize @bullet
179@item
180Start your program, specifying anything that might affect its behavior.
181
182@item
183Make your program stop on specified conditions.
184
185@item
186Examine what has happened, when your program has stopped.
187
188@item
189Change things in your program, so you can experiment with correcting the
190effects of one bug and go on to learn about another.
191@end itemize
192
cce74817 193You can use @value{GDBN} to debug programs written in C and C++.
c906108c 194For more information, see @ref{Support,,Supported languages}.
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195For more information, see @ref{C,,C and C++}.
196
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197@cindex Chill
198@cindex Modula-2
c906108c 199Support for Modula-2 and Chill is partial. For information on Modula-2,
cce74817 200see @ref{Modula-2,,Modula-2}. For information on Chill, see @ref{Chill}.
c906108c 201
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202@cindex Pascal
203Debugging Pascal programs which use sets, subranges, file variables, or
204nested functions does not currently work. @value{GDBN} does not support
205entering expressions, printing values, or similar features using Pascal
206syntax.
c906108c 207
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208@cindex Fortran
209@value{GDBN} can be used to debug programs written in Fortran, although
53a5351d 210it may be necessary to refer to some variables with a trailing
cce74817 211underscore.
c906108c 212
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213@menu
214* Free Software:: Freely redistributable software
215* Contributors:: Contributors to GDB
216@end menu
217
6d2ebf8b 218@node Free Software
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219@unnumberedsec Free software
220
5d161b24 221@value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
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222General Public License
223(GPL). The GPL gives you the freedom to copy or adapt a licensed
224program---but every person getting a copy also gets with it the
225freedom to modify that copy (which means that they must get access to
226the source code), and the freedom to distribute further copies.
227Typical software companies use copyrights to limit your freedoms; the
228Free Software Foundation uses the GPL to preserve these freedoms.
229
230Fundamentally, the General Public License is a license which says that
231you have these freedoms and that you cannot take these freedoms away
232from anyone else.
233
2666264b 234@unnumberedsec Free Software Needs Free Documentation
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235
236The biggest deficiency in the free software community today is not in
237the software---it is the lack of good free documentation that we can
238include with the free software. Many of our most important
239programs do not come with free reference manuals and free introductory
240texts. Documentation is an essential part of any software package;
241when an important free software package does not come with a free
242manual and a free tutorial, that is a major gap. We have many such
243gaps today.
244
245Consider Perl, for instance. The tutorial manuals that people
246normally use are non-free. How did this come about? Because the
247authors of those manuals published them with restrictive terms---no
248copying, no modification, source files not available---which exclude
249them from the free software world.
250
251That wasn't the first time this sort of thing happened, and it was far
252from the last. Many times we have heard a GNU user eagerly describe a
253manual that he is writing, his intended contribution to the community,
254only to learn that he had ruined everything by signing a publication
255contract to make it non-free.
256
257Free documentation, like free software, is a matter of freedom, not
258price. The problem with the non-free manual is not that publishers
259charge a price for printed copies---that in itself is fine. (The Free
260Software Foundation sells printed copies of manuals, too.) The
261problem is the restrictions on the use of the manual. Free manuals
262are available in source code form, and give you permission to copy and
263modify. Non-free manuals do not allow this.
264
265The criteria of freedom for a free manual are roughly the same as for
266free software. Redistribution (including the normal kinds of
267commercial redistribution) must be permitted, so that the manual can
268accompany every copy of the program, both on-line and on paper.
269
270Permission for modification of the technical content is crucial too.
271When people modify the software, adding or changing features, if they
272are conscientious they will change the manual too---so they can
273provide accurate and clear documentation for the modified program. A
274manual that leaves you no choice but to write a new manual to document
275a changed version of the program is not really available to our
276community.
277
278Some kinds of limits on the way modification is handled are
279acceptable. For example, requirements to preserve the original
280author's copyright notice, the distribution terms, or the list of
281authors, are ok. It is also no problem to require modified versions
282to include notice that they were modified. Even entire sections that
283may not be deleted or changed are acceptable, as long as they deal
284with nontechnical topics (like this one). These kinds of restrictions
285are acceptable because they don't obstruct the community's normal use
286of the manual.
287
288However, it must be possible to modify all the @emph{technical}
289content of the manual, and then distribute the result in all the usual
290media, through all the usual channels. Otherwise, the restrictions
291obstruct the use of the manual, it is not free, and we need another
292manual to replace it.
293
294Please spread the word about this issue. Our community continues to
295lose manuals to proprietary publishing. If we spread the word that
296free software needs free reference manuals and free tutorials, perhaps
297the next person who wants to contribute by writing documentation will
298realize, before it is too late, that only free manuals contribute to
299the free software community.
300
301If you are writing documentation, please insist on publishing it under
302the GNU Free Documentation License or another free documentation
303license. Remember that this decision requires your approval---you
304don't have to let the publisher decide. Some commercial publishers
305will use a free license if you insist, but they will not propose the
306option; it is up to you to raise the issue and say firmly that this is
307what you want. If the publisher you are dealing with refuses, please
308try other publishers. If you're not sure whether a proposed license
42584a72 309is free, write to @email{licensing@@gnu.org}.
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310
311You can encourage commercial publishers to sell more free, copylefted
312manuals and tutorials by buying them, and particularly by buying
313copies from the publishers that paid for their writing or for major
314improvements. Meanwhile, try to avoid buying non-free documentation
315at all. Check the distribution terms of a manual before you buy it,
316and insist that whoever seeks your business must respect your freedom.
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317Check the history of the book, and try to reward the publishers that
318have paid or pay the authors to work on it.
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319
320The Free Software Foundation maintains a list of free documentation
321published by other publishers, at
322@url{http://www.fsf.org/doc/other-free-books.html}.
323
6d2ebf8b 324@node Contributors
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325@unnumberedsec Contributors to @value{GDBN}
326
327Richard Stallman was the original author of @value{GDBN}, and of many
328other @sc{gnu} programs. Many others have contributed to its
329development. This section attempts to credit major contributors. One
330of the virtues of free software is that everyone is free to contribute
331to it; with regret, we cannot actually acknowledge everyone here. The
332file @file{ChangeLog} in the @value{GDBN} distribution approximates a
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333blow-by-blow account.
334
335Changes much prior to version 2.0 are lost in the mists of time.
336
337@quotation
338@emph{Plea:} Additions to this section are particularly welcome. If you
339or your friends (or enemies, to be evenhanded) have been unfairly
340omitted from this list, we would like to add your names!
341@end quotation
342
343So that they may not regard their many labors as thankless, we
344particularly thank those who shepherded @value{GDBN} through major
345releases:
b37052ae 346Andrew Cagney (releases 5.0 and 5.1);
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347Jim Blandy (release 4.18);
348Jason Molenda (release 4.17);
349Stan Shebs (release 4.14);
350Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
351Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
352John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
353Jim Kingdon (releases 3.5, 3.4, and 3.3);
354and Randy Smith (releases 3.2, 3.1, and 3.0).
355
356Richard Stallman, assisted at various times by Peter TerMaat, Chris
357Hanson, and Richard Mlynarik, handled releases through 2.8.
358
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359Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
360in @value{GDBN}, with significant additional contributions from Per
361Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
362demangler. Early work on C@t{++} was by Peter TerMaat (who also did
363much general update work leading to release 3.0).
c906108c 364
b37052ae 365@value{GDBN} uses the BFD subroutine library to examine multiple
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366object-file formats; BFD was a joint project of David V.
367Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
368
369David Johnson wrote the original COFF support; Pace Willison did
370the original support for encapsulated COFF.
371
96c405b3 372Brent Benson of Harris Computer Systems contributed DWARF2 support.
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373
374Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
375Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
376support.
377Jean-Daniel Fekete contributed Sun 386i support.
378Chris Hanson improved the HP9000 support.
379Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
380David Johnson contributed Encore Umax support.
381Jyrki Kuoppala contributed Altos 3068 support.
382Jeff Law contributed HP PA and SOM support.
383Keith Packard contributed NS32K support.
384Doug Rabson contributed Acorn Risc Machine support.
385Bob Rusk contributed Harris Nighthawk CX-UX support.
386Chris Smith contributed Convex support (and Fortran debugging).
387Jonathan Stone contributed Pyramid support.
388Michael Tiemann contributed SPARC support.
389Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
390Pace Willison contributed Intel 386 support.
391Jay Vosburgh contributed Symmetry support.
392
393Andreas Schwab contributed M68K Linux support.
394
395Rich Schaefer and Peter Schauer helped with support of SunOS shared
396libraries.
397
398Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
399about several machine instruction sets.
400
401Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
402remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
403contributed remote debugging modules for the i960, VxWorks, A29K UDI,
404and RDI targets, respectively.
405
406Brian Fox is the author of the readline libraries providing
407command-line editing and command history.
408
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409Andrew Beers of SUNY Buffalo wrote the language-switching code, the
410Modula-2 support, and contributed the Languages chapter of this manual.
c906108c 411
5d161b24 412Fred Fish wrote most of the support for Unix System Vr4.
b37052ae 413He also enhanced the command-completion support to cover C@t{++} overloaded
c906108c 414symbols.
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415
416Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
417Super-H processors.
418
419NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
420
421Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
422
423Toshiba sponsored the support for the TX39 Mips processor.
424
425Matsushita sponsored the support for the MN10200 and MN10300 processors.
426
96a2c332 427Fujitsu sponsored the support for SPARClite and FR30 processors.
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428
429Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
430watchpoints.
431
432Michael Snyder added support for tracepoints.
433
434Stu Grossman wrote gdbserver.
435
436Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
96a2c332 437nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
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438
439The following people at the Hewlett-Packard Company contributed
440support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
b37052ae 441(narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
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442compiler, and the terminal user interface: Ben Krepp, Richard Title,
443John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
444Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
445information in this manual.
446
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447DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
448Robert Hoehne made significant contributions to the DJGPP port.
449
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450Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
451development since 1991. Cygnus engineers who have worked on @value{GDBN}
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452fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
453Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
454Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
455Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
456Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
457addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
458JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
459Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
460Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
461Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
462Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
463Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
464Zuhn have made contributions both large and small.
c906108c 465
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466Jim Blandy added support for preprocessor macros, while working for Red
467Hat.
c906108c 468
6d2ebf8b 469@node Sample Session
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470@chapter A Sample @value{GDBN} Session
471
472You can use this manual at your leisure to read all about @value{GDBN}.
473However, a handful of commands are enough to get started using the
474debugger. This chapter illustrates those commands.
475
476@iftex
477In this sample session, we emphasize user input like this: @b{input},
478to make it easier to pick out from the surrounding output.
479@end iftex
480
481@c FIXME: this example may not be appropriate for some configs, where
482@c FIXME...primary interest is in remote use.
483
484One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
485processor) exhibits the following bug: sometimes, when we change its
486quote strings from the default, the commands used to capture one macro
487definition within another stop working. In the following short @code{m4}
488session, we define a macro @code{foo} which expands to @code{0000}; we
489then use the @code{m4} built-in @code{defn} to define @code{bar} as the
490same thing. However, when we change the open quote string to
491@code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
492procedure fails to define a new synonym @code{baz}:
493
494@smallexample
495$ @b{cd gnu/m4}
496$ @b{./m4}
497@b{define(foo,0000)}
498
499@b{foo}
5000000
501@b{define(bar,defn(`foo'))}
502
503@b{bar}
5040000
505@b{changequote(<QUOTE>,<UNQUOTE>)}
506
507@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
508@b{baz}
509@b{C-d}
510m4: End of input: 0: fatal error: EOF in string
511@end smallexample
512
513@noindent
514Let us use @value{GDBN} to try to see what is going on.
515
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516@smallexample
517$ @b{@value{GDBP} m4}
518@c FIXME: this falsifies the exact text played out, to permit smallbook
519@c FIXME... format to come out better.
520@value{GDBN} is free software and you are welcome to distribute copies
5d161b24 521 of it under certain conditions; type "show copying" to see
c906108c 522 the conditions.
5d161b24 523There is absolutely no warranty for @value{GDBN}; type "show warranty"
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524 for details.
525
526@value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
527(@value{GDBP})
528@end smallexample
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529
530@noindent
531@value{GDBN} reads only enough symbol data to know where to find the
532rest when needed; as a result, the first prompt comes up very quickly.
533We now tell @value{GDBN} to use a narrower display width than usual, so
534that examples fit in this manual.
535
536@smallexample
537(@value{GDBP}) @b{set width 70}
538@end smallexample
539
540@noindent
541We need to see how the @code{m4} built-in @code{changequote} works.
542Having looked at the source, we know the relevant subroutine is
543@code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
544@code{break} command.
545
546@smallexample
547(@value{GDBP}) @b{break m4_changequote}
548Breakpoint 1 at 0x62f4: file builtin.c, line 879.
549@end smallexample
550
551@noindent
552Using the @code{run} command, we start @code{m4} running under @value{GDBN}
553control; as long as control does not reach the @code{m4_changequote}
554subroutine, the program runs as usual:
555
556@smallexample
557(@value{GDBP}) @b{run}
558Starting program: /work/Editorial/gdb/gnu/m4/m4
559@b{define(foo,0000)}
560
561@b{foo}
5620000
563@end smallexample
564
565@noindent
566To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
567suspends execution of @code{m4}, displaying information about the
568context where it stops.
569
570@smallexample
571@b{changequote(<QUOTE>,<UNQUOTE>)}
572
5d161b24 573Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
c906108c
SS
574 at builtin.c:879
575879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
576@end smallexample
577
578@noindent
579Now we use the command @code{n} (@code{next}) to advance execution to
580the next line of the current function.
581
582@smallexample
583(@value{GDBP}) @b{n}
584882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
585 : nil,
586@end smallexample
587
588@noindent
589@code{set_quotes} looks like a promising subroutine. We can go into it
590by using the command @code{s} (@code{step}) instead of @code{next}.
591@code{step} goes to the next line to be executed in @emph{any}
592subroutine, so it steps into @code{set_quotes}.
593
594@smallexample
595(@value{GDBP}) @b{s}
596set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
597 at input.c:530
598530 if (lquote != def_lquote)
599@end smallexample
600
601@noindent
602The display that shows the subroutine where @code{m4} is now
603suspended (and its arguments) is called a stack frame display. It
604shows a summary of the stack. We can use the @code{backtrace}
605command (which can also be spelled @code{bt}), to see where we are
606in the stack as a whole: the @code{backtrace} command displays a
607stack frame for each active subroutine.
608
609@smallexample
610(@value{GDBP}) @b{bt}
611#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
612 at input.c:530
5d161b24 613#1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
c906108c
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614 at builtin.c:882
615#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
616#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
617 at macro.c:71
618#4 0x79dc in expand_input () at macro.c:40
619#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
620@end smallexample
621
622@noindent
623We step through a few more lines to see what happens. The first two
624times, we can use @samp{s}; the next two times we use @code{n} to avoid
625falling into the @code{xstrdup} subroutine.
626
627@smallexample
628(@value{GDBP}) @b{s}
6290x3b5c 532 if (rquote != def_rquote)
630(@value{GDBP}) @b{s}
6310x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
632def_lquote : xstrdup(lq);
633(@value{GDBP}) @b{n}
634536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
635 : xstrdup(rq);
636(@value{GDBP}) @b{n}
637538 len_lquote = strlen(rquote);
638@end smallexample
639
640@noindent
641The last line displayed looks a little odd; we can examine the variables
642@code{lquote} and @code{rquote} to see if they are in fact the new left
643and right quotes we specified. We use the command @code{p}
644(@code{print}) to see their values.
645
646@smallexample
647(@value{GDBP}) @b{p lquote}
648$1 = 0x35d40 "<QUOTE>"
649(@value{GDBP}) @b{p rquote}
650$2 = 0x35d50 "<UNQUOTE>"
651@end smallexample
652
653@noindent
654@code{lquote} and @code{rquote} are indeed the new left and right quotes.
655To look at some context, we can display ten lines of source
656surrounding the current line with the @code{l} (@code{list}) command.
657
658@smallexample
659(@value{GDBP}) @b{l}
660533 xfree(rquote);
661534
662535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
663 : xstrdup (lq);
664536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
665 : xstrdup (rq);
666537
667538 len_lquote = strlen(rquote);
668539 len_rquote = strlen(lquote);
669540 @}
670541
671542 void
672@end smallexample
673
674@noindent
675Let us step past the two lines that set @code{len_lquote} and
676@code{len_rquote}, and then examine the values of those variables.
677
678@smallexample
679(@value{GDBP}) @b{n}
680539 len_rquote = strlen(lquote);
681(@value{GDBP}) @b{n}
682540 @}
683(@value{GDBP}) @b{p len_lquote}
684$3 = 9
685(@value{GDBP}) @b{p len_rquote}
686$4 = 7
687@end smallexample
688
689@noindent
690That certainly looks wrong, assuming @code{len_lquote} and
691@code{len_rquote} are meant to be the lengths of @code{lquote} and
692@code{rquote} respectively. We can set them to better values using
693the @code{p} command, since it can print the value of
694any expression---and that expression can include subroutine calls and
695assignments.
696
697@smallexample
698(@value{GDBP}) @b{p len_lquote=strlen(lquote)}
699$5 = 7
700(@value{GDBP}) @b{p len_rquote=strlen(rquote)}
701$6 = 9
702@end smallexample
703
704@noindent
705Is that enough to fix the problem of using the new quotes with the
706@code{m4} built-in @code{defn}? We can allow @code{m4} to continue
707executing with the @code{c} (@code{continue}) command, and then try the
708example that caused trouble initially:
709
710@smallexample
711(@value{GDBP}) @b{c}
712Continuing.
713
714@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
715
716baz
7170000
718@end smallexample
719
720@noindent
721Success! The new quotes now work just as well as the default ones. The
722problem seems to have been just the two typos defining the wrong
723lengths. We allow @code{m4} exit by giving it an EOF as input:
724
725@smallexample
726@b{C-d}
727Program exited normally.
728@end smallexample
729
730@noindent
731The message @samp{Program exited normally.} is from @value{GDBN}; it
732indicates @code{m4} has finished executing. We can end our @value{GDBN}
733session with the @value{GDBN} @code{quit} command.
734
735@smallexample
736(@value{GDBP}) @b{quit}
737@end smallexample
c906108c 738
6d2ebf8b 739@node Invocation
c906108c
SS
740@chapter Getting In and Out of @value{GDBN}
741
742This chapter discusses how to start @value{GDBN}, and how to get out of it.
5d161b24 743The essentials are:
c906108c 744@itemize @bullet
5d161b24 745@item
53a5351d 746type @samp{@value{GDBP}} to start @value{GDBN}.
5d161b24 747@item
c906108c
SS
748type @kbd{quit} or @kbd{C-d} to exit.
749@end itemize
750
751@menu
752* Invoking GDB:: How to start @value{GDBN}
753* Quitting GDB:: How to quit @value{GDBN}
754* Shell Commands:: How to use shell commands inside @value{GDBN}
755@end menu
756
6d2ebf8b 757@node Invoking GDB
c906108c
SS
758@section Invoking @value{GDBN}
759
c906108c
SS
760Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
761@value{GDBN} reads commands from the terminal until you tell it to exit.
762
763You can also run @code{@value{GDBP}} with a variety of arguments and options,
764to specify more of your debugging environment at the outset.
765
c906108c
SS
766The command-line options described here are designed
767to cover a variety of situations; in some environments, some of these
5d161b24 768options may effectively be unavailable.
c906108c
SS
769
770The most usual way to start @value{GDBN} is with one argument,
771specifying an executable program:
772
474c8240 773@smallexample
c906108c 774@value{GDBP} @var{program}
474c8240 775@end smallexample
c906108c 776
c906108c
SS
777@noindent
778You can also start with both an executable program and a core file
779specified:
780
474c8240 781@smallexample
c906108c 782@value{GDBP} @var{program} @var{core}
474c8240 783@end smallexample
c906108c
SS
784
785You can, instead, specify a process ID as a second argument, if you want
786to debug a running process:
787
474c8240 788@smallexample
c906108c 789@value{GDBP} @var{program} 1234
474c8240 790@end smallexample
c906108c
SS
791
792@noindent
793would attach @value{GDBN} to process @code{1234} (unless you also have a file
794named @file{1234}; @value{GDBN} does check for a core file first).
795
c906108c 796Taking advantage of the second command-line argument requires a fairly
2df3850c
JM
797complete operating system; when you use @value{GDBN} as a remote
798debugger attached to a bare board, there may not be any notion of
799``process'', and there is often no way to get a core dump. @value{GDBN}
800will warn you if it is unable to attach or to read core dumps.
c906108c 801
aa26fa3a
TT
802You can optionally have @code{@value{GDBP}} pass any arguments after the
803executable file to the inferior using @code{--args}. This option stops
804option processing.
474c8240 805@smallexample
aa26fa3a 806gdb --args gcc -O2 -c foo.c
474c8240 807@end smallexample
aa26fa3a
TT
808This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
809@code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
810
96a2c332 811You can run @code{@value{GDBP}} without printing the front material, which describes
c906108c
SS
812@value{GDBN}'s non-warranty, by specifying @code{-silent}:
813
814@smallexample
815@value{GDBP} -silent
816@end smallexample
817
818@noindent
819You can further control how @value{GDBN} starts up by using command-line
820options. @value{GDBN} itself can remind you of the options available.
821
822@noindent
823Type
824
474c8240 825@smallexample
c906108c 826@value{GDBP} -help
474c8240 827@end smallexample
c906108c
SS
828
829@noindent
830to display all available options and briefly describe their use
831(@samp{@value{GDBP} -h} is a shorter equivalent).
832
833All options and command line arguments you give are processed
834in sequential order. The order makes a difference when the
835@samp{-x} option is used.
836
837
838@menu
c906108c
SS
839* File Options:: Choosing files
840* Mode Options:: Choosing modes
841@end menu
842
6d2ebf8b 843@node File Options
c906108c
SS
844@subsection Choosing files
845
2df3850c 846When @value{GDBN} starts, it reads any arguments other than options as
c906108c
SS
847specifying an executable file and core file (or process ID). This is
848the same as if the arguments were specified by the @samp{-se} and
19837790
MS
849@samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
850first argument that does not have an associated option flag as
851equivalent to the @samp{-se} option followed by that argument; and the
852second argument that does not have an associated option flag, if any, as
853equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
854If the second argument begins with a decimal digit, @value{GDBN} will
855first attempt to attach to it as a process, and if that fails, attempt
856to open it as a corefile. If you have a corefile whose name begins with
857a digit, you can prevent @value{GDBN} from treating it as a pid by
79f12247 858prefixing it with @file{./}, eg. @file{./12345}.
7a292a7a
SS
859
860If @value{GDBN} has not been configured to included core file support,
861such as for most embedded targets, then it will complain about a second
862argument and ignore it.
c906108c
SS
863
864Many options have both long and short forms; both are shown in the
865following list. @value{GDBN} also recognizes the long forms if you truncate
866them, so long as enough of the option is present to be unambiguous.
867(If you prefer, you can flag option arguments with @samp{--} rather
868than @samp{-}, though we illustrate the more usual convention.)
869
d700128c
EZ
870@c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
871@c way, both those who look for -foo and --foo in the index, will find
872@c it.
873
c906108c
SS
874@table @code
875@item -symbols @var{file}
876@itemx -s @var{file}
d700128c
EZ
877@cindex @code{--symbols}
878@cindex @code{-s}
c906108c
SS
879Read symbol table from file @var{file}.
880
881@item -exec @var{file}
882@itemx -e @var{file}
d700128c
EZ
883@cindex @code{--exec}
884@cindex @code{-e}
7a292a7a
SS
885Use file @var{file} as the executable file to execute when appropriate,
886and for examining pure data in conjunction with a core dump.
c906108c
SS
887
888@item -se @var{file}
d700128c 889@cindex @code{--se}
c906108c
SS
890Read symbol table from file @var{file} and use it as the executable
891file.
892
c906108c
SS
893@item -core @var{file}
894@itemx -c @var{file}
d700128c
EZ
895@cindex @code{--core}
896@cindex @code{-c}
19837790 897Use file @var{file} as a core dump to examine.
c906108c
SS
898
899@item -c @var{number}
19837790
MS
900@item -pid @var{number}
901@itemx -p @var{number}
902@cindex @code{--pid}
903@cindex @code{-p}
904Connect to process ID @var{number}, as with the @code{attach} command.
905If there is no such process, @value{GDBN} will attempt to open a core
906file named @var{number}.
c906108c
SS
907
908@item -command @var{file}
909@itemx -x @var{file}
d700128c
EZ
910@cindex @code{--command}
911@cindex @code{-x}
c906108c
SS
912Execute @value{GDBN} commands from file @var{file}. @xref{Command
913Files,, Command files}.
914
915@item -directory @var{directory}
916@itemx -d @var{directory}
d700128c
EZ
917@cindex @code{--directory}
918@cindex @code{-d}
c906108c
SS
919Add @var{directory} to the path to search for source files.
920
c906108c
SS
921@item -m
922@itemx -mapped
d700128c
EZ
923@cindex @code{--mapped}
924@cindex @code{-m}
c906108c
SS
925@emph{Warning: this option depends on operating system facilities that are not
926supported on all systems.}@*
927If memory-mapped files are available on your system through the @code{mmap}
5d161b24 928system call, you can use this option
c906108c
SS
929to have @value{GDBN} write the symbols from your
930program into a reusable file in the current directory. If the program you are debugging is
96a2c332 931called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
c906108c
SS
932Future @value{GDBN} debugging sessions notice the presence of this file,
933and can quickly map in symbol information from it, rather than reading
934the symbol table from the executable program.
935
936The @file{.syms} file is specific to the host machine where @value{GDBN}
937is run. It holds an exact image of the internal @value{GDBN} symbol
938table. It cannot be shared across multiple host platforms.
c906108c 939
c906108c
SS
940@item -r
941@itemx -readnow
d700128c
EZ
942@cindex @code{--readnow}
943@cindex @code{-r}
c906108c
SS
944Read each symbol file's entire symbol table immediately, rather than
945the default, which is to read it incrementally as it is needed.
946This makes startup slower, but makes future operations faster.
53a5351d 947
c906108c
SS
948@end table
949
2df3850c 950You typically combine the @code{-mapped} and @code{-readnow} options in
c906108c 951order to build a @file{.syms} file that contains complete symbol
2df3850c
JM
952information. (@xref{Files,,Commands to specify files}, for information
953on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
954but build a @file{.syms} file for future use is:
c906108c 955
474c8240 956@smallexample
2df3850c 957gdb -batch -nx -mapped -readnow programname
474c8240 958@end smallexample
c906108c 959
6d2ebf8b 960@node Mode Options
c906108c
SS
961@subsection Choosing modes
962
963You can run @value{GDBN} in various alternative modes---for example, in
964batch mode or quiet mode.
965
966@table @code
967@item -nx
968@itemx -n
d700128c
EZ
969@cindex @code{--nx}
970@cindex @code{-n}
96565e91 971Do not execute commands found in any initialization files. Normally,
2df3850c
JM
972@value{GDBN} executes the commands in these files after all the command
973options and arguments have been processed. @xref{Command Files,,Command
974files}.
c906108c
SS
975
976@item -quiet
d700128c 977@itemx -silent
c906108c 978@itemx -q
d700128c
EZ
979@cindex @code{--quiet}
980@cindex @code{--silent}
981@cindex @code{-q}
c906108c
SS
982``Quiet''. Do not print the introductory and copyright messages. These
983messages are also suppressed in batch mode.
984
985@item -batch
d700128c 986@cindex @code{--batch}
c906108c
SS
987Run in batch mode. Exit with status @code{0} after processing all the
988command files specified with @samp{-x} (and all commands from
989initialization files, if not inhibited with @samp{-n}). Exit with
990nonzero status if an error occurs in executing the @value{GDBN} commands
991in the command files.
992
2df3850c
JM
993Batch mode may be useful for running @value{GDBN} as a filter, for
994example to download and run a program on another computer; in order to
995make this more useful, the message
c906108c 996
474c8240 997@smallexample
c906108c 998Program exited normally.
474c8240 999@end smallexample
c906108c
SS
1000
1001@noindent
2df3850c
JM
1002(which is ordinarily issued whenever a program running under
1003@value{GDBN} control terminates) is not issued when running in batch
1004mode.
1005
1006@item -nowindows
1007@itemx -nw
d700128c
EZ
1008@cindex @code{--nowindows}
1009@cindex @code{-nw}
2df3850c 1010``No windows''. If @value{GDBN} comes with a graphical user interface
96a2c332 1011(GUI) built in, then this option tells @value{GDBN} to only use the command-line
2df3850c
JM
1012interface. If no GUI is available, this option has no effect.
1013
1014@item -windows
1015@itemx -w
d700128c
EZ
1016@cindex @code{--windows}
1017@cindex @code{-w}
2df3850c
JM
1018If @value{GDBN} includes a GUI, then this option requires it to be
1019used if possible.
c906108c
SS
1020
1021@item -cd @var{directory}
d700128c 1022@cindex @code{--cd}
c906108c
SS
1023Run @value{GDBN} using @var{directory} as its working directory,
1024instead of the current directory.
1025
c906108c
SS
1026@item -fullname
1027@itemx -f
d700128c
EZ
1028@cindex @code{--fullname}
1029@cindex @code{-f}
7a292a7a
SS
1030@sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1031subprocess. It tells @value{GDBN} to output the full file name and line
1032number in a standard, recognizable fashion each time a stack frame is
1033displayed (which includes each time your program stops). This
1034recognizable format looks like two @samp{\032} characters, followed by
1035the file name, line number and character position separated by colons,
1036and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1037@samp{\032} characters as a signal to display the source code for the
1038frame.
c906108c 1039
d700128c
EZ
1040@item -epoch
1041@cindex @code{--epoch}
1042The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1043@value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1044routines so as to allow Epoch to display values of expressions in a
1045separate window.
1046
1047@item -annotate @var{level}
1048@cindex @code{--annotate}
1049This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1050effect is identical to using @samp{set annotate @var{level}}
1051(@pxref{Annotations}).
1052Annotation level controls how much information does @value{GDBN} print
1053together with its prompt, values of expressions, source lines, and other
1054types of output. Level 0 is the normal, level 1 is for use when
1055@value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1056maximum annotation suitable for programs that control @value{GDBN}.
1057
1058@item -async
1059@cindex @code{--async}
1060Use the asynchronous event loop for the command-line interface.
1061@value{GDBN} processes all events, such as user keyboard input, via a
1062special event loop. This allows @value{GDBN} to accept and process user
1063commands in parallel with the debugged process being
1064run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1065MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1066suspended when the debuggee runs.}, so you don't need to wait for
1067control to return to @value{GDBN} before you type the next command.
b37052ae 1068(@emph{Note:} as of version 5.1, the target side of the asynchronous
d700128c
EZ
1069operation is not yet in place, so @samp{-async} does not work fully
1070yet.)
1071@c FIXME: when the target side of the event loop is done, the above NOTE
1072@c should be removed.
1073
1074When the standard input is connected to a terminal device, @value{GDBN}
1075uses the asynchronous event loop by default, unless disabled by the
1076@samp{-noasync} option.
1077
1078@item -noasync
1079@cindex @code{--noasync}
1080Disable the asynchronous event loop for the command-line interface.
1081
aa26fa3a
TT
1082@item --args
1083@cindex @code{--args}
1084Change interpretation of command line so that arguments following the
1085executable file are passed as command line arguments to the inferior.
1086This option stops option processing.
1087
2df3850c
JM
1088@item -baud @var{bps}
1089@itemx -b @var{bps}
d700128c
EZ
1090@cindex @code{--baud}
1091@cindex @code{-b}
c906108c
SS
1092Set the line speed (baud rate or bits per second) of any serial
1093interface used by @value{GDBN} for remote debugging.
c906108c
SS
1094
1095@item -tty @var{device}
d700128c
EZ
1096@itemx -t @var{device}
1097@cindex @code{--tty}
1098@cindex @code{-t}
c906108c
SS
1099Run using @var{device} for your program's standard input and output.
1100@c FIXME: kingdon thinks there is more to -tty. Investigate.
c906108c 1101
53a5351d 1102@c resolve the situation of these eventually
c4555f82
SC
1103@item -tui
1104@cindex @code{--tui}
1105Activate the Terminal User Interface when starting.
1106The Terminal User Interface manages several text windows on the terminal,
1107showing source, assembly, registers and @value{GDBN} command outputs
1108(@pxref{TUI, ,@value{GDBN} Text User Interface}).
1109Do not use this option if you run @value{GDBN} from Emacs
1110(@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
53a5351d
JM
1111
1112@c @item -xdb
d700128c 1113@c @cindex @code{--xdb}
53a5351d
JM
1114@c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1115@c For information, see the file @file{xdb_trans.html}, which is usually
1116@c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1117@c systems.
1118
d700128c
EZ
1119@item -interpreter @var{interp}
1120@cindex @code{--interpreter}
1121Use the interpreter @var{interp} for interface with the controlling
1122program or device. This option is meant to be set by programs which
94bbb2c0
AC
1123communicate with @value{GDBN} using it as a back end.
1124
1125@samp{--interpreter=mi} (or @samp{--interpreter=mi1}) causes
1126@value{GDBN} to use the @dfn{gdb/mi interface} (@pxref{GDB/MI, , The
1127@sc{gdb/mi} Interface}). The older @sc{gdb/mi} interface, included in
1128@value{GDBN} version 5.0 can be selected with @samp{--interpreter=mi0}.
d700128c
EZ
1129
1130@item -write
1131@cindex @code{--write}
1132Open the executable and core files for both reading and writing. This
1133is equivalent to the @samp{set write on} command inside @value{GDBN}
1134(@pxref{Patching}).
1135
1136@item -statistics
1137@cindex @code{--statistics}
1138This option causes @value{GDBN} to print statistics about time and
1139memory usage after it completes each command and returns to the prompt.
1140
1141@item -version
1142@cindex @code{--version}
1143This option causes @value{GDBN} to print its version number and
1144no-warranty blurb, and exit.
1145
c906108c
SS
1146@end table
1147
6d2ebf8b 1148@node Quitting GDB
c906108c
SS
1149@section Quitting @value{GDBN}
1150@cindex exiting @value{GDBN}
1151@cindex leaving @value{GDBN}
1152
1153@table @code
1154@kindex quit @r{[}@var{expression}@r{]}
41afff9a 1155@kindex q @r{(@code{quit})}
96a2c332
SS
1156@item quit @r{[}@var{expression}@r{]}
1157@itemx q
1158To exit @value{GDBN}, use the @code{quit} command (abbreviated
1159@code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1160do not supply @var{expression}, @value{GDBN} will terminate normally;
1161otherwise it will terminate using the result of @var{expression} as the
1162error code.
c906108c
SS
1163@end table
1164
1165@cindex interrupt
1166An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1167terminates the action of any @value{GDBN} command that is in progress and
1168returns to @value{GDBN} command level. It is safe to type the interrupt
1169character at any time because @value{GDBN} does not allow it to take effect
1170until a time when it is safe.
1171
c906108c
SS
1172If you have been using @value{GDBN} to control an attached process or
1173device, you can release it with the @code{detach} command
1174(@pxref{Attach, ,Debugging an already-running process}).
c906108c 1175
6d2ebf8b 1176@node Shell Commands
c906108c
SS
1177@section Shell commands
1178
1179If you need to execute occasional shell commands during your
1180debugging session, there is no need to leave or suspend @value{GDBN}; you can
1181just use the @code{shell} command.
1182
1183@table @code
1184@kindex shell
1185@cindex shell escape
1186@item shell @var{command string}
1187Invoke a standard shell to execute @var{command string}.
c906108c 1188If it exists, the environment variable @code{SHELL} determines which
d4f3574e
SS
1189shell to run. Otherwise @value{GDBN} uses the default shell
1190(@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
c906108c
SS
1191@end table
1192
1193The utility @code{make} is often needed in development environments.
1194You do not have to use the @code{shell} command for this purpose in
1195@value{GDBN}:
1196
1197@table @code
1198@kindex make
1199@cindex calling make
1200@item make @var{make-args}
1201Execute the @code{make} program with the specified
1202arguments. This is equivalent to @samp{shell make @var{make-args}}.
1203@end table
1204
6d2ebf8b 1205@node Commands
c906108c
SS
1206@chapter @value{GDBN} Commands
1207
1208You can abbreviate a @value{GDBN} command to the first few letters of the command
1209name, if that abbreviation is unambiguous; and you can repeat certain
1210@value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1211key to get @value{GDBN} to fill out the rest of a word in a command (or to
1212show you the alternatives available, if there is more than one possibility).
1213
1214@menu
1215* Command Syntax:: How to give commands to @value{GDBN}
1216* Completion:: Command completion
1217* Help:: How to ask @value{GDBN} for help
1218@end menu
1219
6d2ebf8b 1220@node Command Syntax
c906108c
SS
1221@section Command syntax
1222
1223A @value{GDBN} command is a single line of input. There is no limit on
1224how long it can be. It starts with a command name, which is followed by
1225arguments whose meaning depends on the command name. For example, the
1226command @code{step} accepts an argument which is the number of times to
1227step, as in @samp{step 5}. You can also use the @code{step} command
96a2c332 1228with no arguments. Some commands do not allow any arguments.
c906108c
SS
1229
1230@cindex abbreviation
1231@value{GDBN} command names may always be truncated if that abbreviation is
1232unambiguous. Other possible command abbreviations are listed in the
1233documentation for individual commands. In some cases, even ambiguous
1234abbreviations are allowed; for example, @code{s} is specially defined as
1235equivalent to @code{step} even though there are other commands whose
1236names start with @code{s}. You can test abbreviations by using them as
1237arguments to the @code{help} command.
1238
1239@cindex repeating commands
41afff9a 1240@kindex RET @r{(repeat last command)}
c906108c 1241A blank line as input to @value{GDBN} (typing just @key{RET}) means to
96a2c332 1242repeat the previous command. Certain commands (for example, @code{run})
c906108c
SS
1243will not repeat this way; these are commands whose unintentional
1244repetition might cause trouble and which you are unlikely to want to
1245repeat.
1246
1247The @code{list} and @code{x} commands, when you repeat them with
1248@key{RET}, construct new arguments rather than repeating
1249exactly as typed. This permits easy scanning of source or memory.
1250
1251@value{GDBN} can also use @key{RET} in another way: to partition lengthy
1252output, in a way similar to the common utility @code{more}
1253(@pxref{Screen Size,,Screen size}). Since it is easy to press one
1254@key{RET} too many in this situation, @value{GDBN} disables command
1255repetition after any command that generates this sort of display.
1256
41afff9a 1257@kindex # @r{(a comment)}
c906108c
SS
1258@cindex comment
1259Any text from a @kbd{#} to the end of the line is a comment; it does
1260nothing. This is useful mainly in command files (@pxref{Command
1261Files,,Command files}).
1262
88118b3a
TT
1263@cindex repeating command sequences
1264@kindex C-o @r{(operate-and-get-next)}
1265The @kbd{C-o} binding is useful for repeating a complex sequence of
1266commands. This command accepts the current line, like @kbd{RET}, and
1267then fetches the next line relative to the current line from the history
1268for editing.
1269
6d2ebf8b 1270@node Completion
c906108c
SS
1271@section Command completion
1272
1273@cindex completion
1274@cindex word completion
1275@value{GDBN} can fill in the rest of a word in a command for you, if there is
1276only one possibility; it can also show you what the valid possibilities
1277are for the next word in a command, at any time. This works for @value{GDBN}
1278commands, @value{GDBN} subcommands, and the names of symbols in your program.
1279
1280Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1281of a word. If there is only one possibility, @value{GDBN} fills in the
1282word, and waits for you to finish the command (or press @key{RET} to
1283enter it). For example, if you type
1284
1285@c FIXME "@key" does not distinguish its argument sufficiently to permit
1286@c complete accuracy in these examples; space introduced for clarity.
1287@c If texinfo enhancements make it unnecessary, it would be nice to
1288@c replace " @key" by "@key" in the following...
474c8240 1289@smallexample
c906108c 1290(@value{GDBP}) info bre @key{TAB}
474c8240 1291@end smallexample
c906108c
SS
1292
1293@noindent
1294@value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1295the only @code{info} subcommand beginning with @samp{bre}:
1296
474c8240 1297@smallexample
c906108c 1298(@value{GDBP}) info breakpoints
474c8240 1299@end smallexample
c906108c
SS
1300
1301@noindent
1302You can either press @key{RET} at this point, to run the @code{info
1303breakpoints} command, or backspace and enter something else, if
1304@samp{breakpoints} does not look like the command you expected. (If you
1305were sure you wanted @code{info breakpoints} in the first place, you
1306might as well just type @key{RET} immediately after @samp{info bre},
1307to exploit command abbreviations rather than command completion).
1308
1309If there is more than one possibility for the next word when you press
1310@key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1311characters and try again, or just press @key{TAB} a second time;
1312@value{GDBN} displays all the possible completions for that word. For
1313example, you might want to set a breakpoint on a subroutine whose name
1314begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1315just sounds the bell. Typing @key{TAB} again displays all the
1316function names in your program that begin with those characters, for
1317example:
1318
474c8240 1319@smallexample
c906108c
SS
1320(@value{GDBP}) b make_ @key{TAB}
1321@exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
5d161b24
DB
1322make_a_section_from_file make_environ
1323make_abs_section make_function_type
1324make_blockvector make_pointer_type
1325make_cleanup make_reference_type
c906108c
SS
1326make_command make_symbol_completion_list
1327(@value{GDBP}) b make_
474c8240 1328@end smallexample
c906108c
SS
1329
1330@noindent
1331After displaying the available possibilities, @value{GDBN} copies your
1332partial input (@samp{b make_} in the example) so you can finish the
1333command.
1334
1335If you just want to see the list of alternatives in the first place, you
b37052ae 1336can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
7a292a7a 1337means @kbd{@key{META} ?}. You can type this either by holding down a
c906108c 1338key designated as the @key{META} shift on your keyboard (if there is
7a292a7a 1339one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
c906108c
SS
1340
1341@cindex quotes in commands
1342@cindex completion of quoted strings
1343Sometimes the string you need, while logically a ``word'', may contain
7a292a7a
SS
1344parentheses or other characters that @value{GDBN} normally excludes from
1345its notion of a word. To permit word completion to work in this
1346situation, you may enclose words in @code{'} (single quote marks) in
1347@value{GDBN} commands.
c906108c 1348
c906108c 1349The most likely situation where you might need this is in typing the
b37052ae
EZ
1350name of a C@t{++} function. This is because C@t{++} allows function
1351overloading (multiple definitions of the same function, distinguished
1352by argument type). For example, when you want to set a breakpoint you
1353may need to distinguish whether you mean the version of @code{name}
1354that takes an @code{int} parameter, @code{name(int)}, or the version
1355that takes a @code{float} parameter, @code{name(float)}. To use the
1356word-completion facilities in this situation, type a single quote
1357@code{'} at the beginning of the function name. This alerts
1358@value{GDBN} that it may need to consider more information than usual
1359when you press @key{TAB} or @kbd{M-?} to request word completion:
c906108c 1360
474c8240 1361@smallexample
96a2c332 1362(@value{GDBP}) b 'bubble( @kbd{M-?}
c906108c
SS
1363bubble(double,double) bubble(int,int)
1364(@value{GDBP}) b 'bubble(
474c8240 1365@end smallexample
c906108c
SS
1366
1367In some cases, @value{GDBN} can tell that completing a name requires using
1368quotes. When this happens, @value{GDBN} inserts the quote for you (while
1369completing as much as it can) if you do not type the quote in the first
1370place:
1371
474c8240 1372@smallexample
c906108c
SS
1373(@value{GDBP}) b bub @key{TAB}
1374@exdent @value{GDBN} alters your input line to the following, and rings a bell:
1375(@value{GDBP}) b 'bubble(
474c8240 1376@end smallexample
c906108c
SS
1377
1378@noindent
1379In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1380you have not yet started typing the argument list when you ask for
1381completion on an overloaded symbol.
1382
d4f3574e 1383For more information about overloaded functions, see @ref{C plus plus
b37052ae 1384expressions, ,C@t{++} expressions}. You can use the command @code{set
c906108c 1385overload-resolution off} to disable overload resolution;
b37052ae 1386see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
c906108c
SS
1387
1388
6d2ebf8b 1389@node Help
c906108c
SS
1390@section Getting help
1391@cindex online documentation
1392@kindex help
1393
5d161b24 1394You can always ask @value{GDBN} itself for information on its commands,
c906108c
SS
1395using the command @code{help}.
1396
1397@table @code
41afff9a 1398@kindex h @r{(@code{help})}
c906108c
SS
1399@item help
1400@itemx h
1401You can use @code{help} (abbreviated @code{h}) with no arguments to
1402display a short list of named classes of commands:
1403
1404@smallexample
1405(@value{GDBP}) help
1406List of classes of commands:
1407
2df3850c 1408aliases -- Aliases of other commands
c906108c 1409breakpoints -- Making program stop at certain points
2df3850c 1410data -- Examining data
c906108c 1411files -- Specifying and examining files
2df3850c
JM
1412internals -- Maintenance commands
1413obscure -- Obscure features
1414running -- Running the program
1415stack -- Examining the stack
c906108c
SS
1416status -- Status inquiries
1417support -- Support facilities
96a2c332
SS
1418tracepoints -- Tracing of program execution without@*
1419 stopping the program
c906108c 1420user-defined -- User-defined commands
c906108c 1421
5d161b24 1422Type "help" followed by a class name for a list of
c906108c 1423commands in that class.
5d161b24 1424Type "help" followed by command name for full
c906108c
SS
1425documentation.
1426Command name abbreviations are allowed if unambiguous.
1427(@value{GDBP})
1428@end smallexample
96a2c332 1429@c the above line break eliminates huge line overfull...
c906108c
SS
1430
1431@item help @var{class}
1432Using one of the general help classes as an argument, you can get a
1433list of the individual commands in that class. For example, here is the
1434help display for the class @code{status}:
1435
1436@smallexample
1437(@value{GDBP}) help status
1438Status inquiries.
1439
1440List of commands:
1441
1442@c Line break in "show" line falsifies real output, but needed
1443@c to fit in smallbook page size.
2df3850c
JM
1444info -- Generic command for showing things
1445 about the program being debugged
1446show -- Generic command for showing things
1447 about the debugger
c906108c 1448
5d161b24 1449Type "help" followed by command name for full
c906108c
SS
1450documentation.
1451Command name abbreviations are allowed if unambiguous.
1452(@value{GDBP})
1453@end smallexample
1454
1455@item help @var{command}
1456With a command name as @code{help} argument, @value{GDBN} displays a
1457short paragraph on how to use that command.
1458
6837a0a2
DB
1459@kindex apropos
1460@item apropos @var{args}
1461The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1462commands, and their documentation, for the regular expression specified in
1463@var{args}. It prints out all matches found. For example:
1464
1465@smallexample
1466apropos reload
1467@end smallexample
1468
b37052ae
EZ
1469@noindent
1470results in:
6837a0a2
DB
1471
1472@smallexample
6d2ebf8b
SS
1473@c @group
1474set symbol-reloading -- Set dynamic symbol table reloading
1475 multiple times in one run
1476show symbol-reloading -- Show dynamic symbol table reloading
1477 multiple times in one run
1478@c @end group
6837a0a2
DB
1479@end smallexample
1480
c906108c
SS
1481@kindex complete
1482@item complete @var{args}
1483The @code{complete @var{args}} command lists all the possible completions
1484for the beginning of a command. Use @var{args} to specify the beginning of the
1485command you want completed. For example:
1486
1487@smallexample
1488complete i
1489@end smallexample
1490
1491@noindent results in:
1492
1493@smallexample
1494@group
2df3850c
JM
1495if
1496ignore
c906108c
SS
1497info
1498inspect
c906108c
SS
1499@end group
1500@end smallexample
1501
1502@noindent This is intended for use by @sc{gnu} Emacs.
1503@end table
1504
1505In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1506and @code{show} to inquire about the state of your program, or the state
1507of @value{GDBN} itself. Each command supports many topics of inquiry; this
1508manual introduces each of them in the appropriate context. The listings
1509under @code{info} and under @code{show} in the Index point to
1510all the sub-commands. @xref{Index}.
1511
1512@c @group
1513@table @code
1514@kindex info
41afff9a 1515@kindex i @r{(@code{info})}
c906108c
SS
1516@item info
1517This command (abbreviated @code{i}) is for describing the state of your
1518program. For example, you can list the arguments given to your program
1519with @code{info args}, list the registers currently in use with @code{info
1520registers}, or list the breakpoints you have set with @code{info breakpoints}.
1521You can get a complete list of the @code{info} sub-commands with
1522@w{@code{help info}}.
1523
1524@kindex set
1525@item set
5d161b24 1526You can assign the result of an expression to an environment variable with
c906108c
SS
1527@code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1528@code{set prompt $}.
1529
1530@kindex show
1531@item show
5d161b24 1532In contrast to @code{info}, @code{show} is for describing the state of
c906108c
SS
1533@value{GDBN} itself.
1534You can change most of the things you can @code{show}, by using the
1535related command @code{set}; for example, you can control what number
1536system is used for displays with @code{set radix}, or simply inquire
1537which is currently in use with @code{show radix}.
1538
1539@kindex info set
1540To display all the settable parameters and their current
1541values, you can use @code{show} with no arguments; you may also use
1542@code{info set}. Both commands produce the same display.
1543@c FIXME: "info set" violates the rule that "info" is for state of
1544@c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1545@c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1546@end table
1547@c @end group
1548
1549Here are three miscellaneous @code{show} subcommands, all of which are
1550exceptional in lacking corresponding @code{set} commands:
1551
1552@table @code
1553@kindex show version
1554@cindex version number
1555@item show version
1556Show what version of @value{GDBN} is running. You should include this
2df3850c
JM
1557information in @value{GDBN} bug-reports. If multiple versions of
1558@value{GDBN} are in use at your site, you may need to determine which
1559version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1560commands are introduced, and old ones may wither away. Also, many
1561system vendors ship variant versions of @value{GDBN}, and there are
96a2c332 1562variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2df3850c
JM
1563The version number is the same as the one announced when you start
1564@value{GDBN}.
c906108c
SS
1565
1566@kindex show copying
1567@item show copying
1568Display information about permission for copying @value{GDBN}.
1569
1570@kindex show warranty
1571@item show warranty
2df3850c 1572Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
96a2c332 1573if your version of @value{GDBN} comes with one.
2df3850c 1574
c906108c
SS
1575@end table
1576
6d2ebf8b 1577@node Running
c906108c
SS
1578@chapter Running Programs Under @value{GDBN}
1579
1580When you run a program under @value{GDBN}, you must first generate
1581debugging information when you compile it.
7a292a7a
SS
1582
1583You may start @value{GDBN} with its arguments, if any, in an environment
1584of your choice. If you are doing native debugging, you may redirect
1585your program's input and output, debug an already running process, or
1586kill a child process.
c906108c
SS
1587
1588@menu
1589* Compilation:: Compiling for debugging
1590* Starting:: Starting your program
c906108c
SS
1591* Arguments:: Your program's arguments
1592* Environment:: Your program's environment
c906108c
SS
1593
1594* Working Directory:: Your program's working directory
1595* Input/Output:: Your program's input and output
1596* Attach:: Debugging an already-running process
1597* Kill Process:: Killing the child process
c906108c
SS
1598
1599* Threads:: Debugging programs with multiple threads
1600* Processes:: Debugging programs with multiple processes
1601@end menu
1602
6d2ebf8b 1603@node Compilation
c906108c
SS
1604@section Compiling for debugging
1605
1606In order to debug a program effectively, you need to generate
1607debugging information when you compile it. This debugging information
1608is stored in the object file; it describes the data type of each
1609variable or function and the correspondence between source line numbers
1610and addresses in the executable code.
1611
1612To request debugging information, specify the @samp{-g} option when you run
1613the compiler.
1614
e2e0bcd1
JB
1615Most compilers do not include information about preprocessor macros in
1616the debugging information if you specify the @option{-g} flag alone,
1617because this information is rather large. Version 3.1 of @value{NGCC},
1618the @sc{gnu} C compiler, provides macro information if you specify the
1619options @option{-gdwarf-2} and @option{-g3}; the former option requests
1620debugging information in the Dwarf 2 format, and the latter requests
1621``extra information''. In the future, we hope to find more compact ways
1622to represent macro information, so that it can be included with
1623@option{-g} alone.
1624
c906108c
SS
1625Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1626options together. Using those compilers, you cannot generate optimized
1627executables containing debugging information.
1628
53a5351d
JM
1629@value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1630without @samp{-O}, making it possible to debug optimized code. We
1631recommend that you @emph{always} use @samp{-g} whenever you compile a
1632program. You may think your program is correct, but there is no sense
1633in pushing your luck.
c906108c
SS
1634
1635@cindex optimized code, debugging
1636@cindex debugging optimized code
1637When you debug a program compiled with @samp{-g -O}, remember that the
1638optimizer is rearranging your code; the debugger shows you what is
1639really there. Do not be too surprised when the execution path does not
1640exactly match your source file! An extreme example: if you define a
1641variable, but never use it, @value{GDBN} never sees that
1642variable---because the compiler optimizes it out of existence.
1643
1644Some things do not work as well with @samp{-g -O} as with just
1645@samp{-g}, particularly on machines with instruction scheduling. If in
1646doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1647please report it to us as a bug (including a test case!).
1648
1649Older versions of the @sc{gnu} C compiler permitted a variant option
1650@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1651format; if your @sc{gnu} C compiler has this option, do not use it.
1652
1653@need 2000
6d2ebf8b 1654@node Starting
c906108c
SS
1655@section Starting your program
1656@cindex starting
1657@cindex running
1658
1659@table @code
1660@kindex run
41afff9a 1661@kindex r @r{(@code{run})}
c906108c
SS
1662@item run
1663@itemx r
7a292a7a
SS
1664Use the @code{run} command to start your program under @value{GDBN}.
1665You must first specify the program name (except on VxWorks) with an
1666argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1667@value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1668(@pxref{Files, ,Commands to specify files}).
c906108c
SS
1669
1670@end table
1671
c906108c
SS
1672If you are running your program in an execution environment that
1673supports processes, @code{run} creates an inferior process and makes
1674that process run your program. (In environments without processes,
1675@code{run} jumps to the start of your program.)
1676
1677The execution of a program is affected by certain information it
1678receives from its superior. @value{GDBN} provides ways to specify this
1679information, which you must do @emph{before} starting your program. (You
1680can change it after starting your program, but such changes only affect
1681your program the next time you start it.) This information may be
1682divided into four categories:
1683
1684@table @asis
1685@item The @emph{arguments.}
1686Specify the arguments to give your program as the arguments of the
1687@code{run} command. If a shell is available on your target, the shell
1688is used to pass the arguments, so that you may use normal conventions
1689(such as wildcard expansion or variable substitution) in describing
1690the arguments.
1691In Unix systems, you can control which shell is used with the
1692@code{SHELL} environment variable.
1693@xref{Arguments, ,Your program's arguments}.
1694
1695@item The @emph{environment.}
1696Your program normally inherits its environment from @value{GDBN}, but you can
1697use the @value{GDBN} commands @code{set environment} and @code{unset
1698environment} to change parts of the environment that affect
1699your program. @xref{Environment, ,Your program's environment}.
1700
1701@item The @emph{working directory.}
1702Your program inherits its working directory from @value{GDBN}. You can set
1703the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1704@xref{Working Directory, ,Your program's working directory}.
1705
1706@item The @emph{standard input and output.}
1707Your program normally uses the same device for standard input and
1708standard output as @value{GDBN} is using. You can redirect input and output
1709in the @code{run} command line, or you can use the @code{tty} command to
1710set a different device for your program.
1711@xref{Input/Output, ,Your program's input and output}.
1712
1713@cindex pipes
1714@emph{Warning:} While input and output redirection work, you cannot use
1715pipes to pass the output of the program you are debugging to another
1716program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1717wrong program.
1718@end table
c906108c
SS
1719
1720When you issue the @code{run} command, your program begins to execute
1721immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1722of how to arrange for your program to stop. Once your program has
1723stopped, you may call functions in your program, using the @code{print}
1724or @code{call} commands. @xref{Data, ,Examining Data}.
1725
1726If the modification time of your symbol file has changed since the last
1727time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1728table, and reads it again. When it does this, @value{GDBN} tries to retain
1729your current breakpoints.
1730
6d2ebf8b 1731@node Arguments
c906108c
SS
1732@section Your program's arguments
1733
1734@cindex arguments (to your program)
1735The arguments to your program can be specified by the arguments of the
5d161b24 1736@code{run} command.
c906108c
SS
1737They are passed to a shell, which expands wildcard characters and
1738performs redirection of I/O, and thence to your program. Your
1739@code{SHELL} environment variable (if it exists) specifies what shell
1740@value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
d4f3574e
SS
1741the default shell (@file{/bin/sh} on Unix).
1742
1743On non-Unix systems, the program is usually invoked directly by
1744@value{GDBN}, which emulates I/O redirection via the appropriate system
1745calls, and the wildcard characters are expanded by the startup code of
1746the program, not by the shell.
c906108c
SS
1747
1748@code{run} with no arguments uses the same arguments used by the previous
1749@code{run}, or those set by the @code{set args} command.
1750
c906108c 1751@table @code
41afff9a 1752@kindex set args
c906108c
SS
1753@item set args
1754Specify the arguments to be used the next time your program is run. If
1755@code{set args} has no arguments, @code{run} executes your program
1756with no arguments. Once you have run your program with arguments,
1757using @code{set args} before the next @code{run} is the only way to run
1758it again without arguments.
1759
1760@kindex show args
1761@item show args
1762Show the arguments to give your program when it is started.
1763@end table
1764
6d2ebf8b 1765@node Environment
c906108c
SS
1766@section Your program's environment
1767
1768@cindex environment (of your program)
1769The @dfn{environment} consists of a set of environment variables and
1770their values. Environment variables conventionally record such things as
1771your user name, your home directory, your terminal type, and your search
1772path for programs to run. Usually you set up environment variables with
1773the shell and they are inherited by all the other programs you run. When
1774debugging, it can be useful to try running your program with a modified
1775environment without having to start @value{GDBN} over again.
1776
1777@table @code
1778@kindex path
1779@item path @var{directory}
1780Add @var{directory} to the front of the @code{PATH} environment variable
17cc6a06
EZ
1781(the search path for executables) that will be passed to your program.
1782The value of @code{PATH} used by @value{GDBN} does not change.
d4f3574e
SS
1783You may specify several directory names, separated by whitespace or by a
1784system-dependent separator character (@samp{:} on Unix, @samp{;} on
1785MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1786is moved to the front, so it is searched sooner.
c906108c
SS
1787
1788You can use the string @samp{$cwd} to refer to whatever is the current
1789working directory at the time @value{GDBN} searches the path. If you
1790use @samp{.} instead, it refers to the directory where you executed the
1791@code{path} command. @value{GDBN} replaces @samp{.} in the
1792@var{directory} argument (with the current path) before adding
1793@var{directory} to the search path.
1794@c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1795@c document that, since repeating it would be a no-op.
1796
1797@kindex show paths
1798@item show paths
1799Display the list of search paths for executables (the @code{PATH}
1800environment variable).
1801
1802@kindex show environment
1803@item show environment @r{[}@var{varname}@r{]}
1804Print the value of environment variable @var{varname} to be given to
1805your program when it starts. If you do not supply @var{varname},
1806print the names and values of all environment variables to be given to
1807your program. You can abbreviate @code{environment} as @code{env}.
1808
1809@kindex set environment
53a5351d 1810@item set environment @var{varname} @r{[}=@var{value}@r{]}
c906108c
SS
1811Set environment variable @var{varname} to @var{value}. The value
1812changes for your program only, not for @value{GDBN} itself. @var{value} may
1813be any string; the values of environment variables are just strings, and
1814any interpretation is supplied by your program itself. The @var{value}
1815parameter is optional; if it is eliminated, the variable is set to a
1816null value.
1817@c "any string" here does not include leading, trailing
1818@c blanks. Gnu asks: does anyone care?
1819
1820For example, this command:
1821
474c8240 1822@smallexample
c906108c 1823set env USER = foo
474c8240 1824@end smallexample
c906108c
SS
1825
1826@noindent
d4f3574e 1827tells the debugged program, when subsequently run, that its user is named
c906108c
SS
1828@samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1829are not actually required.)
1830
1831@kindex unset environment
1832@item unset environment @var{varname}
1833Remove variable @var{varname} from the environment to be passed to your
1834program. This is different from @samp{set env @var{varname} =};
1835@code{unset environment} removes the variable from the environment,
1836rather than assigning it an empty value.
1837@end table
1838
d4f3574e
SS
1839@emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1840the shell indicated
c906108c
SS
1841by your @code{SHELL} environment variable if it exists (or
1842@code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1843that runs an initialization file---such as @file{.cshrc} for C-shell, or
1844@file{.bashrc} for BASH---any variables you set in that file affect
1845your program. You may wish to move setting of environment variables to
1846files that are only run when you sign on, such as @file{.login} or
1847@file{.profile}.
1848
6d2ebf8b 1849@node Working Directory
c906108c
SS
1850@section Your program's working directory
1851
1852@cindex working directory (of your program)
1853Each time you start your program with @code{run}, it inherits its
1854working directory from the current working directory of @value{GDBN}.
1855The @value{GDBN} working directory is initially whatever it inherited
1856from its parent process (typically the shell), but you can specify a new
1857working directory in @value{GDBN} with the @code{cd} command.
1858
1859The @value{GDBN} working directory also serves as a default for the commands
1860that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1861specify files}.
1862
1863@table @code
1864@kindex cd
1865@item cd @var{directory}
1866Set the @value{GDBN} working directory to @var{directory}.
1867
1868@kindex pwd
1869@item pwd
1870Print the @value{GDBN} working directory.
1871@end table
1872
6d2ebf8b 1873@node Input/Output
c906108c
SS
1874@section Your program's input and output
1875
1876@cindex redirection
1877@cindex i/o
1878@cindex terminal
1879By default, the program you run under @value{GDBN} does input and output to
5d161b24 1880the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
c906108c
SS
1881to its own terminal modes to interact with you, but it records the terminal
1882modes your program was using and switches back to them when you continue
1883running your program.
1884
1885@table @code
1886@kindex info terminal
1887@item info terminal
1888Displays information recorded by @value{GDBN} about the terminal modes your
1889program is using.
1890@end table
1891
1892You can redirect your program's input and/or output using shell
1893redirection with the @code{run} command. For example,
1894
474c8240 1895@smallexample
c906108c 1896run > outfile
474c8240 1897@end smallexample
c906108c
SS
1898
1899@noindent
1900starts your program, diverting its output to the file @file{outfile}.
1901
1902@kindex tty
1903@cindex controlling terminal
1904Another way to specify where your program should do input and output is
1905with the @code{tty} command. This command accepts a file name as
1906argument, and causes this file to be the default for future @code{run}
1907commands. It also resets the controlling terminal for the child
1908process, for future @code{run} commands. For example,
1909
474c8240 1910@smallexample
c906108c 1911tty /dev/ttyb
474c8240 1912@end smallexample
c906108c
SS
1913
1914@noindent
1915directs that processes started with subsequent @code{run} commands
1916default to do input and output on the terminal @file{/dev/ttyb} and have
1917that as their controlling terminal.
1918
1919An explicit redirection in @code{run} overrides the @code{tty} command's
1920effect on the input/output device, but not its effect on the controlling
1921terminal.
1922
1923When you use the @code{tty} command or redirect input in the @code{run}
1924command, only the input @emph{for your program} is affected. The input
1925for @value{GDBN} still comes from your terminal.
1926
6d2ebf8b 1927@node Attach
c906108c
SS
1928@section Debugging an already-running process
1929@kindex attach
1930@cindex attach
1931
1932@table @code
1933@item attach @var{process-id}
1934This command attaches to a running process---one that was started
1935outside @value{GDBN}. (@code{info files} shows your active
1936targets.) The command takes as argument a process ID. The usual way to
1937find out the process-id of a Unix process is with the @code{ps} utility,
1938or with the @samp{jobs -l} shell command.
1939
1940@code{attach} does not repeat if you press @key{RET} a second time after
1941executing the command.
1942@end table
1943
1944To use @code{attach}, your program must be running in an environment
1945which supports processes; for example, @code{attach} does not work for
1946programs on bare-board targets that lack an operating system. You must
1947also have permission to send the process a signal.
1948
1949When you use @code{attach}, the debugger finds the program running in
1950the process first by looking in the current working directory, then (if
1951the program is not found) by using the source file search path
1952(@pxref{Source Path, ,Specifying source directories}). You can also use
1953the @code{file} command to load the program. @xref{Files, ,Commands to
1954Specify Files}.
1955
1956The first thing @value{GDBN} does after arranging to debug the specified
1957process is to stop it. You can examine and modify an attached process
53a5351d
JM
1958with all the @value{GDBN} commands that are ordinarily available when
1959you start processes with @code{run}. You can insert breakpoints; you
1960can step and continue; you can modify storage. If you would rather the
1961process continue running, you may use the @code{continue} command after
c906108c
SS
1962attaching @value{GDBN} to the process.
1963
1964@table @code
1965@kindex detach
1966@item detach
1967When you have finished debugging the attached process, you can use the
1968@code{detach} command to release it from @value{GDBN} control. Detaching
1969the process continues its execution. After the @code{detach} command,
1970that process and @value{GDBN} become completely independent once more, and you
1971are ready to @code{attach} another process or start one with @code{run}.
1972@code{detach} does not repeat if you press @key{RET} again after
1973executing the command.
1974@end table
1975
1976If you exit @value{GDBN} or use the @code{run} command while you have an
1977attached process, you kill that process. By default, @value{GDBN} asks
1978for confirmation if you try to do either of these things; you can
1979control whether or not you need to confirm by using the @code{set
1980confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1981messages}).
1982
6d2ebf8b 1983@node Kill Process
c906108c 1984@section Killing the child process
c906108c
SS
1985
1986@table @code
1987@kindex kill
1988@item kill
1989Kill the child process in which your program is running under @value{GDBN}.
1990@end table
1991
1992This command is useful if you wish to debug a core dump instead of a
1993running process. @value{GDBN} ignores any core dump file while your program
1994is running.
1995
1996On some operating systems, a program cannot be executed outside @value{GDBN}
1997while you have breakpoints set on it inside @value{GDBN}. You can use the
1998@code{kill} command in this situation to permit running your program
1999outside the debugger.
2000
2001The @code{kill} command is also useful if you wish to recompile and
2002relink your program, since on many systems it is impossible to modify an
2003executable file while it is running in a process. In this case, when you
2004next type @code{run}, @value{GDBN} notices that the file has changed, and
2005reads the symbol table again (while trying to preserve your current
2006breakpoint settings).
2007
6d2ebf8b 2008@node Threads
c906108c 2009@section Debugging programs with multiple threads
c906108c
SS
2010
2011@cindex threads of execution
2012@cindex multiple threads
2013@cindex switching threads
2014In some operating systems, such as HP-UX and Solaris, a single program
2015may have more than one @dfn{thread} of execution. The precise semantics
2016of threads differ from one operating system to another, but in general
2017the threads of a single program are akin to multiple processes---except
2018that they share one address space (that is, they can all examine and
2019modify the same variables). On the other hand, each thread has its own
2020registers and execution stack, and perhaps private memory.
2021
2022@value{GDBN} provides these facilities for debugging multi-thread
2023programs:
2024
2025@itemize @bullet
2026@item automatic notification of new threads
2027@item @samp{thread @var{threadno}}, a command to switch among threads
2028@item @samp{info threads}, a command to inquire about existing threads
5d161b24 2029@item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
c906108c
SS
2030a command to apply a command to a list of threads
2031@item thread-specific breakpoints
2032@end itemize
2033
c906108c
SS
2034@quotation
2035@emph{Warning:} These facilities are not yet available on every
2036@value{GDBN} configuration where the operating system supports threads.
2037If your @value{GDBN} does not support threads, these commands have no
2038effect. For example, a system without thread support shows no output
2039from @samp{info threads}, and always rejects the @code{thread} command,
2040like this:
2041
2042@smallexample
2043(@value{GDBP}) info threads
2044(@value{GDBP}) thread 1
2045Thread ID 1 not known. Use the "info threads" command to
2046see the IDs of currently known threads.
2047@end smallexample
2048@c FIXME to implementors: how hard would it be to say "sorry, this GDB
2049@c doesn't support threads"?
2050@end quotation
c906108c
SS
2051
2052@cindex focus of debugging
2053@cindex current thread
2054The @value{GDBN} thread debugging facility allows you to observe all
2055threads while your program runs---but whenever @value{GDBN} takes
2056control, one thread in particular is always the focus of debugging.
2057This thread is called the @dfn{current thread}. Debugging commands show
2058program information from the perspective of the current thread.
2059
41afff9a 2060@cindex @code{New} @var{systag} message
c906108c
SS
2061@cindex thread identifier (system)
2062@c FIXME-implementors!! It would be more helpful if the [New...] message
2063@c included GDB's numeric thread handle, so you could just go to that
2064@c thread without first checking `info threads'.
2065Whenever @value{GDBN} detects a new thread in your program, it displays
2066the target system's identification for the thread with a message in the
2067form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2068whose form varies depending on the particular system. For example, on
2069LynxOS, you might see
2070
474c8240 2071@smallexample
c906108c 2072[New process 35 thread 27]
474c8240 2073@end smallexample
c906108c
SS
2074
2075@noindent
2076when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2077the @var{systag} is simply something like @samp{process 368}, with no
2078further qualifier.
2079
2080@c FIXME!! (1) Does the [New...] message appear even for the very first
2081@c thread of a program, or does it only appear for the
6ca652b0 2082@c second---i.e.@: when it becomes obvious we have a multithread
c906108c
SS
2083@c program?
2084@c (2) *Is* there necessarily a first thread always? Or do some
2085@c multithread systems permit starting a program with multiple
5d161b24 2086@c threads ab initio?
c906108c
SS
2087
2088@cindex thread number
2089@cindex thread identifier (GDB)
2090For debugging purposes, @value{GDBN} associates its own thread
2091number---always a single integer---with each thread in your program.
2092
2093@table @code
2094@kindex info threads
2095@item info threads
2096Display a summary of all threads currently in your
2097program. @value{GDBN} displays for each thread (in this order):
2098
2099@enumerate
2100@item the thread number assigned by @value{GDBN}
2101
2102@item the target system's thread identifier (@var{systag})
2103
2104@item the current stack frame summary for that thread
2105@end enumerate
2106
2107@noindent
2108An asterisk @samp{*} to the left of the @value{GDBN} thread number
2109indicates the current thread.
2110
5d161b24 2111For example,
c906108c
SS
2112@end table
2113@c end table here to get a little more width for example
2114
2115@smallexample
2116(@value{GDBP}) info threads
2117 3 process 35 thread 27 0x34e5 in sigpause ()
2118 2 process 35 thread 23 0x34e5 in sigpause ()
2119* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2120 at threadtest.c:68
2121@end smallexample
53a5351d
JM
2122
2123On HP-UX systems:
c906108c
SS
2124
2125@cindex thread number
2126@cindex thread identifier (GDB)
2127For debugging purposes, @value{GDBN} associates its own thread
2128number---a small integer assigned in thread-creation order---with each
2129thread in your program.
2130
41afff9a
EZ
2131@cindex @code{New} @var{systag} message, on HP-UX
2132@cindex thread identifier (system), on HP-UX
c906108c
SS
2133@c FIXME-implementors!! It would be more helpful if the [New...] message
2134@c included GDB's numeric thread handle, so you could just go to that
2135@c thread without first checking `info threads'.
2136Whenever @value{GDBN} detects a new thread in your program, it displays
2137both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2138form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2139whose form varies depending on the particular system. For example, on
2140HP-UX, you see
2141
474c8240 2142@smallexample
c906108c 2143[New thread 2 (system thread 26594)]
474c8240 2144@end smallexample
c906108c
SS
2145
2146@noindent
5d161b24 2147when @value{GDBN} notices a new thread.
c906108c
SS
2148
2149@table @code
2150@kindex info threads
2151@item info threads
2152Display a summary of all threads currently in your
2153program. @value{GDBN} displays for each thread (in this order):
2154
2155@enumerate
2156@item the thread number assigned by @value{GDBN}
2157
2158@item the target system's thread identifier (@var{systag})
2159
2160@item the current stack frame summary for that thread
2161@end enumerate
2162
2163@noindent
2164An asterisk @samp{*} to the left of the @value{GDBN} thread number
2165indicates the current thread.
2166
5d161b24 2167For example,
c906108c
SS
2168@end table
2169@c end table here to get a little more width for example
2170
474c8240 2171@smallexample
c906108c 2172(@value{GDBP}) info threads
6d2ebf8b
SS
2173 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2174 at quicksort.c:137
2175 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2176 from /usr/lib/libc.2
2177 1 system thread 27905 0x7b003498 in _brk () \@*
2178 from /usr/lib/libc.2
474c8240 2179@end smallexample
c906108c
SS
2180
2181@table @code
2182@kindex thread @var{threadno}
2183@item thread @var{threadno}
2184Make thread number @var{threadno} the current thread. The command
2185argument @var{threadno} is the internal @value{GDBN} thread number, as
2186shown in the first field of the @samp{info threads} display.
2187@value{GDBN} responds by displaying the system identifier of the thread
2188you selected, and its current stack frame summary:
2189
2190@smallexample
2191@c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2192(@value{GDBP}) thread 2
c906108c 2193[Switching to process 35 thread 23]
c906108c
SS
21940x34e5 in sigpause ()
2195@end smallexample
2196
2197@noindent
2198As with the @samp{[New @dots{}]} message, the form of the text after
2199@samp{Switching to} depends on your system's conventions for identifying
5d161b24 2200threads.
c906108c
SS
2201
2202@kindex thread apply
2203@item thread apply [@var{threadno}] [@var{all}] @var{args}
2204The @code{thread apply} command allows you to apply a command to one or
2205more threads. Specify the numbers of the threads that you want affected
2206with the command argument @var{threadno}. @var{threadno} is the internal
2207@value{GDBN} thread number, as shown in the first field of the @samp{info
5d161b24
DB
2208threads} display. To apply a command to all threads, use
2209@code{thread apply all} @var{args}.
c906108c
SS
2210@end table
2211
2212@cindex automatic thread selection
2213@cindex switching threads automatically
2214@cindex threads, automatic switching
2215Whenever @value{GDBN} stops your program, due to a breakpoint or a
2216signal, it automatically selects the thread where that breakpoint or
2217signal happened. @value{GDBN} alerts you to the context switch with a
2218message of the form @samp{[Switching to @var{systag}]} to identify the
2219thread.
2220
2221@xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2222more information about how @value{GDBN} behaves when you stop and start
2223programs with multiple threads.
2224
2225@xref{Set Watchpoints,,Setting watchpoints}, for information about
2226watchpoints in programs with multiple threads.
c906108c 2227
6d2ebf8b 2228@node Processes
c906108c
SS
2229@section Debugging programs with multiple processes
2230
2231@cindex fork, debugging programs which call
2232@cindex multiple processes
2233@cindex processes, multiple
53a5351d
JM
2234On most systems, @value{GDBN} has no special support for debugging
2235programs which create additional processes using the @code{fork}
2236function. When a program forks, @value{GDBN} will continue to debug the
2237parent process and the child process will run unimpeded. If you have
2238set a breakpoint in any code which the child then executes, the child
2239will get a @code{SIGTRAP} signal which (unless it catches the signal)
2240will cause it to terminate.
c906108c
SS
2241
2242However, if you want to debug the child process there is a workaround
2243which isn't too painful. Put a call to @code{sleep} in the code which
2244the child process executes after the fork. It may be useful to sleep
2245only if a certain environment variable is set, or a certain file exists,
2246so that the delay need not occur when you don't want to run @value{GDBN}
2247on the child. While the child is sleeping, use the @code{ps} program to
2248get its process ID. Then tell @value{GDBN} (a new invocation of
2249@value{GDBN} if you are also debugging the parent process) to attach to
d4f3574e 2250the child process (@pxref{Attach}). From that point on you can debug
c906108c 2251the child process just like any other process which you attached to.
c906108c 2252
53a5351d
JM
2253On HP-UX (11.x and later only?), @value{GDBN} provides support for
2254debugging programs that create additional processes using the
2255@code{fork} or @code{vfork} function.
c906108c
SS
2256
2257By default, when a program forks, @value{GDBN} will continue to debug
2258the parent process and the child process will run unimpeded.
2259
2260If you want to follow the child process instead of the parent process,
2261use the command @w{@code{set follow-fork-mode}}.
2262
2263@table @code
2264@kindex set follow-fork-mode
2265@item set follow-fork-mode @var{mode}
2266Set the debugger response to a program call of @code{fork} or
2267@code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2268process. The @var{mode} can be:
2269
2270@table @code
2271@item parent
2272The original process is debugged after a fork. The child process runs
2df3850c 2273unimpeded. This is the default.
c906108c
SS
2274
2275@item child
2276The new process is debugged after a fork. The parent process runs
2277unimpeded.
2278
2279@item ask
2280The debugger will ask for one of the above choices.
2281@end table
2282
2283@item show follow-fork-mode
2df3850c 2284Display the current debugger response to a @code{fork} or @code{vfork} call.
c906108c
SS
2285@end table
2286
2287If you ask to debug a child process and a @code{vfork} is followed by an
2288@code{exec}, @value{GDBN} executes the new target up to the first
2289breakpoint in the new target. If you have a breakpoint set on
2290@code{main} in your original program, the breakpoint will also be set on
2291the child process's @code{main}.
2292
2293When a child process is spawned by @code{vfork}, you cannot debug the
2294child or parent until an @code{exec} call completes.
2295
2296If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2297call executes, the new target restarts. To restart the parent process,
2298use the @code{file} command with the parent executable name as its
2299argument.
2300
2301You can use the @code{catch} command to make @value{GDBN} stop whenever
2302a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2303Catchpoints, ,Setting catchpoints}.
c906108c 2304
6d2ebf8b 2305@node Stopping
c906108c
SS
2306@chapter Stopping and Continuing
2307
2308The principal purposes of using a debugger are so that you can stop your
2309program before it terminates; or so that, if your program runs into
2310trouble, you can investigate and find out why.
2311
7a292a7a
SS
2312Inside @value{GDBN}, your program may stop for any of several reasons,
2313such as a signal, a breakpoint, or reaching a new line after a
2314@value{GDBN} command such as @code{step}. You may then examine and
2315change variables, set new breakpoints or remove old ones, and then
2316continue execution. Usually, the messages shown by @value{GDBN} provide
2317ample explanation of the status of your program---but you can also
2318explicitly request this information at any time.
c906108c
SS
2319
2320@table @code
2321@kindex info program
2322@item info program
2323Display information about the status of your program: whether it is
7a292a7a 2324running or not, what process it is, and why it stopped.
c906108c
SS
2325@end table
2326
2327@menu
2328* Breakpoints:: Breakpoints, watchpoints, and catchpoints
2329* Continuing and Stepping:: Resuming execution
c906108c 2330* Signals:: Signals
c906108c 2331* Thread Stops:: Stopping and starting multi-thread programs
c906108c
SS
2332@end menu
2333
6d2ebf8b 2334@node Breakpoints
c906108c
SS
2335@section Breakpoints, watchpoints, and catchpoints
2336
2337@cindex breakpoints
2338A @dfn{breakpoint} makes your program stop whenever a certain point in
2339the program is reached. For each breakpoint, you can add conditions to
2340control in finer detail whether your program stops. You can set
2341breakpoints with the @code{break} command and its variants (@pxref{Set
2342Breaks, ,Setting breakpoints}), to specify the place where your program
2343should stop by line number, function name or exact address in the
2344program.
2345
2346In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2347breakpoints in shared libraries before the executable is run. There is
2348a minor limitation on HP-UX systems: you must wait until the executable
2349is run in order to set breakpoints in shared library routines that are
2350not called directly by the program (for example, routines that are
2351arguments in a @code{pthread_create} call).
2352
2353@cindex watchpoints
2354@cindex memory tracing
2355@cindex breakpoint on memory address
2356@cindex breakpoint on variable modification
2357A @dfn{watchpoint} is a special breakpoint that stops your program
2358when the value of an expression changes. You must use a different
2359command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2360watchpoints}), but aside from that, you can manage a watchpoint like
2361any other breakpoint: you enable, disable, and delete both breakpoints
2362and watchpoints using the same commands.
2363
2364You can arrange to have values from your program displayed automatically
2365whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2366Automatic display}.
2367
2368@cindex catchpoints
2369@cindex breakpoint on events
2370A @dfn{catchpoint} is another special breakpoint that stops your program
b37052ae 2371when a certain kind of event occurs, such as the throwing of a C@t{++}
c906108c
SS
2372exception or the loading of a library. As with watchpoints, you use a
2373different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2374catchpoints}), but aside from that, you can manage a catchpoint like any
2375other breakpoint. (To stop when your program receives a signal, use the
d4f3574e 2376@code{handle} command; see @ref{Signals, ,Signals}.)
c906108c
SS
2377
2378@cindex breakpoint numbers
2379@cindex numbers for breakpoints
2380@value{GDBN} assigns a number to each breakpoint, watchpoint, or
2381catchpoint when you create it; these numbers are successive integers
2382starting with one. In many of the commands for controlling various
2383features of breakpoints you use the breakpoint number to say which
2384breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2385@dfn{disabled}; if disabled, it has no effect on your program until you
2386enable it again.
2387
c5394b80
JM
2388@cindex breakpoint ranges
2389@cindex ranges of breakpoints
2390Some @value{GDBN} commands accept a range of breakpoints on which to
2391operate. A breakpoint range is either a single breakpoint number, like
2392@samp{5}, or two such numbers, in increasing order, separated by a
2393hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2394all breakpoint in that range are operated on.
2395
c906108c
SS
2396@menu
2397* Set Breaks:: Setting breakpoints
2398* Set Watchpoints:: Setting watchpoints
2399* Set Catchpoints:: Setting catchpoints
2400* Delete Breaks:: Deleting breakpoints
2401* Disabling:: Disabling breakpoints
2402* Conditions:: Break conditions
2403* Break Commands:: Breakpoint command lists
c906108c 2404* Breakpoint Menus:: Breakpoint menus
d4f3574e 2405* Error in Breakpoints:: ``Cannot insert breakpoints''
c906108c
SS
2406@end menu
2407
6d2ebf8b 2408@node Set Breaks
c906108c
SS
2409@subsection Setting breakpoints
2410
5d161b24 2411@c FIXME LMB what does GDB do if no code on line of breakpt?
c906108c
SS
2412@c consider in particular declaration with/without initialization.
2413@c
2414@c FIXME 2 is there stuff on this already? break at fun start, already init?
2415
2416@kindex break
41afff9a
EZ
2417@kindex b @r{(@code{break})}
2418@vindex $bpnum@r{, convenience variable}
c906108c
SS
2419@cindex latest breakpoint
2420Breakpoints are set with the @code{break} command (abbreviated
5d161b24 2421@code{b}). The debugger convenience variable @samp{$bpnum} records the
f3b28801 2422number of the breakpoint you've set most recently; see @ref{Convenience
c906108c
SS
2423Vars,, Convenience variables}, for a discussion of what you can do with
2424convenience variables.
2425
2426You have several ways to say where the breakpoint should go.
2427
2428@table @code
2429@item break @var{function}
5d161b24 2430Set a breakpoint at entry to function @var{function}.
c906108c 2431When using source languages that permit overloading of symbols, such as
b37052ae 2432C@t{++}, @var{function} may refer to more than one possible place to break.
c906108c 2433@xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
c906108c
SS
2434
2435@item break +@var{offset}
2436@itemx break -@var{offset}
2437Set a breakpoint some number of lines forward or back from the position
d4f3574e 2438at which execution stopped in the currently selected @dfn{stack frame}.
2df3850c 2439(@xref{Frames, ,Frames}, for a description of stack frames.)
c906108c
SS
2440
2441@item break @var{linenum}
2442Set a breakpoint at line @var{linenum} in the current source file.
d4f3574e
SS
2443The current source file is the last file whose source text was printed.
2444The breakpoint will stop your program just before it executes any of the
c906108c
SS
2445code on that line.
2446
2447@item break @var{filename}:@var{linenum}
2448Set a breakpoint at line @var{linenum} in source file @var{filename}.
2449
2450@item break @var{filename}:@var{function}
2451Set a breakpoint at entry to function @var{function} found in file
2452@var{filename}. Specifying a file name as well as a function name is
2453superfluous except when multiple files contain similarly named
2454functions.
2455
2456@item break *@var{address}
2457Set a breakpoint at address @var{address}. You can use this to set
2458breakpoints in parts of your program which do not have debugging
2459information or source files.
2460
2461@item break
2462When called without any arguments, @code{break} sets a breakpoint at
2463the next instruction to be executed in the selected stack frame
2464(@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2465innermost, this makes your program stop as soon as control
2466returns to that frame. This is similar to the effect of a
2467@code{finish} command in the frame inside the selected frame---except
2468that @code{finish} does not leave an active breakpoint. If you use
2469@code{break} without an argument in the innermost frame, @value{GDBN} stops
2470the next time it reaches the current location; this may be useful
2471inside loops.
2472
2473@value{GDBN} normally ignores breakpoints when it resumes execution, until at
2474least one instruction has been executed. If it did not do this, you
2475would be unable to proceed past a breakpoint without first disabling the
2476breakpoint. This rule applies whether or not the breakpoint already
2477existed when your program stopped.
2478
2479@item break @dots{} if @var{cond}
2480Set a breakpoint with condition @var{cond}; evaluate the expression
2481@var{cond} each time the breakpoint is reached, and stop only if the
2482value is nonzero---that is, if @var{cond} evaluates as true.
2483@samp{@dots{}} stands for one of the possible arguments described
2484above (or no argument) specifying where to break. @xref{Conditions,
2485,Break conditions}, for more information on breakpoint conditions.
2486
2487@kindex tbreak
2488@item tbreak @var{args}
2489Set a breakpoint enabled only for one stop. @var{args} are the
2490same as for the @code{break} command, and the breakpoint is set in the same
2491way, but the breakpoint is automatically deleted after the first time your
2492program stops there. @xref{Disabling, ,Disabling breakpoints}.
2493
c906108c
SS
2494@kindex hbreak
2495@item hbreak @var{args}
d4f3574e
SS
2496Set a hardware-assisted breakpoint. @var{args} are the same as for the
2497@code{break} command and the breakpoint is set in the same way, but the
c906108c
SS
2498breakpoint requires hardware support and some target hardware may not
2499have this support. The main purpose of this is EPROM/ROM code
d4f3574e
SS
2500debugging, so you can set a breakpoint at an instruction without
2501changing the instruction. This can be used with the new trap-generation
2502provided by SPARClite DSU and some x86-based targets. These targets
2503will generate traps when a program accesses some data or instruction
2504address that is assigned to the debug registers. However the hardware
2505breakpoint registers can take a limited number of breakpoints. For
2506example, on the DSU, only two data breakpoints can be set at a time, and
2507@value{GDBN} will reject this command if more than two are used. Delete
2508or disable unused hardware breakpoints before setting new ones
2509(@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
c906108c
SS
2510
2511@kindex thbreak
2512@item thbreak @var{args}
2513Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2514are the same as for the @code{hbreak} command and the breakpoint is set in
5d161b24 2515the same way. However, like the @code{tbreak} command,
c906108c
SS
2516the breakpoint is automatically deleted after the
2517first time your program stops there. Also, like the @code{hbreak}
5d161b24
DB
2518command, the breakpoint requires hardware support and some target hardware
2519may not have this support. @xref{Disabling, ,Disabling breakpoints}.
d4f3574e 2520See also @ref{Conditions, ,Break conditions}.
c906108c
SS
2521
2522@kindex rbreak
2523@cindex regular expression
2524@item rbreak @var{regex}
c906108c 2525Set breakpoints on all functions matching the regular expression
11cf8741
JM
2526@var{regex}. This command sets an unconditional breakpoint on all
2527matches, printing a list of all breakpoints it set. Once these
2528breakpoints are set, they are treated just like the breakpoints set with
2529the @code{break} command. You can delete them, disable them, or make
2530them conditional the same way as any other breakpoint.
2531
2532The syntax of the regular expression is the standard one used with tools
2533like @file{grep}. Note that this is different from the syntax used by
2534shells, so for instance @code{foo*} matches all functions that include
2535an @code{fo} followed by zero or more @code{o}s. There is an implicit
2536@code{.*} leading and trailing the regular expression you supply, so to
2537match only functions that begin with @code{foo}, use @code{^foo}.
c906108c 2538
b37052ae 2539When debugging C@t{++} programs, @code{rbreak} is useful for setting
c906108c
SS
2540breakpoints on overloaded functions that are not members of any special
2541classes.
c906108c
SS
2542
2543@kindex info breakpoints
2544@cindex @code{$_} and @code{info breakpoints}
2545@item info breakpoints @r{[}@var{n}@r{]}
2546@itemx info break @r{[}@var{n}@r{]}
2547@itemx info watchpoints @r{[}@var{n}@r{]}
2548Print a table of all breakpoints, watchpoints, and catchpoints set and
2549not deleted, with the following columns for each breakpoint:
2550
2551@table @emph
2552@item Breakpoint Numbers
2553@item Type
2554Breakpoint, watchpoint, or catchpoint.
2555@item Disposition
2556Whether the breakpoint is marked to be disabled or deleted when hit.
2557@item Enabled or Disabled
2558Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2559that are not enabled.
2560@item Address
2df3850c 2561Where the breakpoint is in your program, as a memory address.
c906108c
SS
2562@item What
2563Where the breakpoint is in the source for your program, as a file and
2564line number.
2565@end table
2566
2567@noindent
2568If a breakpoint is conditional, @code{info break} shows the condition on
2569the line following the affected breakpoint; breakpoint commands, if any,
2570are listed after that.
2571
2572@noindent
2573@code{info break} with a breakpoint
2574number @var{n} as argument lists only that breakpoint. The
2575convenience variable @code{$_} and the default examining-address for
2576the @code{x} command are set to the address of the last breakpoint
5d161b24 2577listed (@pxref{Memory, ,Examining memory}).
c906108c
SS
2578
2579@noindent
2580@code{info break} displays a count of the number of times the breakpoint
2581has been hit. This is especially useful in conjunction with the
2582@code{ignore} command. You can ignore a large number of breakpoint
2583hits, look at the breakpoint info to see how many times the breakpoint
2584was hit, and then run again, ignoring one less than that number. This
2585will get you quickly to the last hit of that breakpoint.
2586@end table
2587
2588@value{GDBN} allows you to set any number of breakpoints at the same place in
2589your program. There is nothing silly or meaningless about this. When
2590the breakpoints are conditional, this is even useful
2591(@pxref{Conditions, ,Break conditions}).
2592
2593@cindex negative breakpoint numbers
2594@cindex internal @value{GDBN} breakpoints
eb12ee30
AC
2595@value{GDBN} itself sometimes sets breakpoints in your program for
2596special purposes, such as proper handling of @code{longjmp} (in C
2597programs). These internal breakpoints are assigned negative numbers,
2598starting with @code{-1}; @samp{info breakpoints} does not display them.
c906108c 2599You can see these breakpoints with the @value{GDBN} maintenance command
eb12ee30 2600@samp{maint info breakpoints} (@pxref{maint info breakpoints}).
c906108c
SS
2601
2602
6d2ebf8b 2603@node Set Watchpoints
c906108c
SS
2604@subsection Setting watchpoints
2605
2606@cindex setting watchpoints
2607@cindex software watchpoints
2608@cindex hardware watchpoints
2609You can use a watchpoint to stop execution whenever the value of an
2610expression changes, without having to predict a particular place where
2611this may happen.
2612
2613Depending on your system, watchpoints may be implemented in software or
2df3850c 2614hardware. @value{GDBN} does software watchpointing by single-stepping your
c906108c
SS
2615program and testing the variable's value each time, which is hundreds of
2616times slower than normal execution. (But this may still be worth it, to
2617catch errors where you have no clue what part of your program is the
2618culprit.)
2619
d4f3574e 2620On some systems, such as HP-UX, Linux and some other x86-based targets,
2df3850c 2621@value{GDBN} includes support for
c906108c
SS
2622hardware watchpoints, which do not slow down the running of your
2623program.
2624
2625@table @code
2626@kindex watch
2627@item watch @var{expr}
2628Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2629is written into by the program and its value changes.
2630
2631@kindex rwatch
2632@item rwatch @var{expr}
2633Set a watchpoint that will break when watch @var{expr} is read by the program.
c906108c
SS
2634
2635@kindex awatch
2636@item awatch @var{expr}
2df3850c 2637Set a watchpoint that will break when @var{expr} is either read or written into
7be570e7 2638by the program.
c906108c
SS
2639
2640@kindex info watchpoints
2641@item info watchpoints
2642This command prints a list of watchpoints, breakpoints, and catchpoints;
2643it is the same as @code{info break}.
2644@end table
2645
2646@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2647watchpoints execute very quickly, and the debugger reports a change in
2648value at the exact instruction where the change occurs. If @value{GDBN}
2649cannot set a hardware watchpoint, it sets a software watchpoint, which
2650executes more slowly and reports the change in value at the next
2651statement, not the instruction, after the change occurs.
2652
2653When you issue the @code{watch} command, @value{GDBN} reports
2654
474c8240 2655@smallexample
c906108c 2656Hardware watchpoint @var{num}: @var{expr}
474c8240 2657@end smallexample
c906108c
SS
2658
2659@noindent
2660if it was able to set a hardware watchpoint.
2661
7be570e7
JM
2662Currently, the @code{awatch} and @code{rwatch} commands can only set
2663hardware watchpoints, because accesses to data that don't change the
2664value of the watched expression cannot be detected without examining
2665every instruction as it is being executed, and @value{GDBN} does not do
2666that currently. If @value{GDBN} finds that it is unable to set a
2667hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2668will print a message like this:
2669
2670@smallexample
2671Expression cannot be implemented with read/access watchpoint.
2672@end smallexample
2673
2674Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2675data type of the watched expression is wider than what a hardware
2676watchpoint on the target machine can handle. For example, some systems
2677can only watch regions that are up to 4 bytes wide; on such systems you
2678cannot set hardware watchpoints for an expression that yields a
2679double-precision floating-point number (which is typically 8 bytes
2680wide). As a work-around, it might be possible to break the large region
2681into a series of smaller ones and watch them with separate watchpoints.
2682
2683If you set too many hardware watchpoints, @value{GDBN} might be unable
2684to insert all of them when you resume the execution of your program.
2685Since the precise number of active watchpoints is unknown until such
2686time as the program is about to be resumed, @value{GDBN} might not be
2687able to warn you about this when you set the watchpoints, and the
2688warning will be printed only when the program is resumed:
2689
2690@smallexample
2691Hardware watchpoint @var{num}: Could not insert watchpoint
2692@end smallexample
2693
2694@noindent
2695If this happens, delete or disable some of the watchpoints.
2696
2697The SPARClite DSU will generate traps when a program accesses some data
2698or instruction address that is assigned to the debug registers. For the
2699data addresses, DSU facilitates the @code{watch} command. However the
2700hardware breakpoint registers can only take two data watchpoints, and
2701both watchpoints must be the same kind. For example, you can set two
2702watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2703@strong{or} two with @code{awatch} commands, but you cannot set one
2704watchpoint with one command and the other with a different command.
c906108c
SS
2705@value{GDBN} will reject the command if you try to mix watchpoints.
2706Delete or disable unused watchpoint commands before setting new ones.
2707
2708If you call a function interactively using @code{print} or @code{call},
2df3850c 2709any watchpoints you have set will be inactive until @value{GDBN} reaches another
c906108c
SS
2710kind of breakpoint or the call completes.
2711
7be570e7
JM
2712@value{GDBN} automatically deletes watchpoints that watch local
2713(automatic) variables, or expressions that involve such variables, when
2714they go out of scope, that is, when the execution leaves the block in
2715which these variables were defined. In particular, when the program
2716being debugged terminates, @emph{all} local variables go out of scope,
2717and so only watchpoints that watch global variables remain set. If you
2718rerun the program, you will need to set all such watchpoints again. One
2719way of doing that would be to set a code breakpoint at the entry to the
2720@code{main} function and when it breaks, set all the watchpoints.
2721
c906108c
SS
2722@quotation
2723@cindex watchpoints and threads
2724@cindex threads and watchpoints
c906108c
SS
2725@emph{Warning:} In multi-thread programs, watchpoints have only limited
2726usefulness. With the current watchpoint implementation, @value{GDBN}
2727can only watch the value of an expression @emph{in a single thread}. If
2728you are confident that the expression can only change due to the current
2729thread's activity (and if you are also confident that no other thread
2730can become current), then you can use watchpoints as usual. However,
2731@value{GDBN} may not notice when a non-current thread's activity changes
2732the expression.
53a5351d 2733
d4f3574e 2734@c FIXME: this is almost identical to the previous paragraph.
53a5351d
JM
2735@emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2736have only limited usefulness. If @value{GDBN} creates a software
2737watchpoint, it can only watch the value of an expression @emph{in a
2738single thread}. If you are confident that the expression can only
2739change due to the current thread's activity (and if you are also
2740confident that no other thread can become current), then you can use
2741software watchpoints as usual. However, @value{GDBN} may not notice
2742when a non-current thread's activity changes the expression. (Hardware
2743watchpoints, in contrast, watch an expression in all threads.)
c906108c 2744@end quotation
c906108c 2745
6d2ebf8b 2746@node Set Catchpoints
c906108c 2747@subsection Setting catchpoints
d4f3574e 2748@cindex catchpoints, setting
c906108c
SS
2749@cindex exception handlers
2750@cindex event handling
2751
2752You can use @dfn{catchpoints} to cause the debugger to stop for certain
b37052ae 2753kinds of program events, such as C@t{++} exceptions or the loading of a
c906108c
SS
2754shared library. Use the @code{catch} command to set a catchpoint.
2755
2756@table @code
2757@kindex catch
2758@item catch @var{event}
2759Stop when @var{event} occurs. @var{event} can be any of the following:
2760@table @code
2761@item throw
2762@kindex catch throw
b37052ae 2763The throwing of a C@t{++} exception.
c906108c
SS
2764
2765@item catch
2766@kindex catch catch
b37052ae 2767The catching of a C@t{++} exception.
c906108c
SS
2768
2769@item exec
2770@kindex catch exec
2771A call to @code{exec}. This is currently only available for HP-UX.
2772
2773@item fork
2774@kindex catch fork
2775A call to @code{fork}. This is currently only available for HP-UX.
2776
2777@item vfork
2778@kindex catch vfork
2779A call to @code{vfork}. This is currently only available for HP-UX.
2780
2781@item load
2782@itemx load @var{libname}
2783@kindex catch load
2784The dynamic loading of any shared library, or the loading of the library
2785@var{libname}. This is currently only available for HP-UX.
2786
2787@item unload
2788@itemx unload @var{libname}
2789@kindex catch unload
2790The unloading of any dynamically loaded shared library, or the unloading
2791of the library @var{libname}. This is currently only available for HP-UX.
2792@end table
2793
2794@item tcatch @var{event}
2795Set a catchpoint that is enabled only for one stop. The catchpoint is
2796automatically deleted after the first time the event is caught.
2797
2798@end table
2799
2800Use the @code{info break} command to list the current catchpoints.
2801
b37052ae 2802There are currently some limitations to C@t{++} exception handling
c906108c
SS
2803(@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2804
2805@itemize @bullet
2806@item
2807If you call a function interactively, @value{GDBN} normally returns
2808control to you when the function has finished executing. If the call
2809raises an exception, however, the call may bypass the mechanism that
2810returns control to you and cause your program either to abort or to
2811simply continue running until it hits a breakpoint, catches a signal
2812that @value{GDBN} is listening for, or exits. This is the case even if
2813you set a catchpoint for the exception; catchpoints on exceptions are
2814disabled within interactive calls.
2815
2816@item
2817You cannot raise an exception interactively.
2818
2819@item
2820You cannot install an exception handler interactively.
2821@end itemize
2822
2823@cindex raise exceptions
2824Sometimes @code{catch} is not the best way to debug exception handling:
2825if you need to know exactly where an exception is raised, it is better to
2826stop @emph{before} the exception handler is called, since that way you
2827can see the stack before any unwinding takes place. If you set a
2828breakpoint in an exception handler instead, it may not be easy to find
2829out where the exception was raised.
2830
2831To stop just before an exception handler is called, you need some
b37052ae 2832knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
c906108c
SS
2833raised by calling a library function named @code{__raise_exception}
2834which has the following ANSI C interface:
2835
474c8240 2836@smallexample
c906108c 2837 /* @var{addr} is where the exception identifier is stored.
d4f3574e
SS
2838 @var{id} is the exception identifier. */
2839 void __raise_exception (void **addr, void *id);
474c8240 2840@end smallexample
c906108c
SS
2841
2842@noindent
2843To make the debugger catch all exceptions before any stack
2844unwinding takes place, set a breakpoint on @code{__raise_exception}
2845(@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2846
2847With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2848that depends on the value of @var{id}, you can stop your program when
2849a specific exception is raised. You can use multiple conditional
2850breakpoints to stop your program when any of a number of exceptions are
2851raised.
2852
2853
6d2ebf8b 2854@node Delete Breaks
c906108c
SS
2855@subsection Deleting breakpoints
2856
2857@cindex clearing breakpoints, watchpoints, catchpoints
2858@cindex deleting breakpoints, watchpoints, catchpoints
2859It is often necessary to eliminate a breakpoint, watchpoint, or
2860catchpoint once it has done its job and you no longer want your program
2861to stop there. This is called @dfn{deleting} the breakpoint. A
2862breakpoint that has been deleted no longer exists; it is forgotten.
2863
2864With the @code{clear} command you can delete breakpoints according to
2865where they are in your program. With the @code{delete} command you can
2866delete individual breakpoints, watchpoints, or catchpoints by specifying
2867their breakpoint numbers.
2868
2869It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2870automatically ignores breakpoints on the first instruction to be executed
2871when you continue execution without changing the execution address.
2872
2873@table @code
2874@kindex clear
2875@item clear
2876Delete any breakpoints at the next instruction to be executed in the
2877selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2878the innermost frame is selected, this is a good way to delete a
2879breakpoint where your program just stopped.
2880
2881@item clear @var{function}
2882@itemx clear @var{filename}:@var{function}
2883Delete any breakpoints set at entry to the function @var{function}.
2884
2885@item clear @var{linenum}
2886@itemx clear @var{filename}:@var{linenum}
2887Delete any breakpoints set at or within the code of the specified line.
2888
2889@cindex delete breakpoints
2890@kindex delete
41afff9a 2891@kindex d @r{(@code{delete})}
c5394b80
JM
2892@item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2893Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2894ranges specified as arguments. If no argument is specified, delete all
c906108c
SS
2895breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2896confirm off}). You can abbreviate this command as @code{d}.
2897@end table
2898
6d2ebf8b 2899@node Disabling
c906108c
SS
2900@subsection Disabling breakpoints
2901
2902@kindex disable breakpoints
2903@kindex enable breakpoints
2904Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2905prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2906it had been deleted, but remembers the information on the breakpoint so
2907that you can @dfn{enable} it again later.
2908
2909You disable and enable breakpoints, watchpoints, and catchpoints with
2910the @code{enable} and @code{disable} commands, optionally specifying one
2911or more breakpoint numbers as arguments. Use @code{info break} or
2912@code{info watch} to print a list of breakpoints, watchpoints, and
2913catchpoints if you do not know which numbers to use.
2914
2915A breakpoint, watchpoint, or catchpoint can have any of four different
2916states of enablement:
2917
2918@itemize @bullet
2919@item
2920Enabled. The breakpoint stops your program. A breakpoint set
2921with the @code{break} command starts out in this state.
2922@item
2923Disabled. The breakpoint has no effect on your program.
2924@item
2925Enabled once. The breakpoint stops your program, but then becomes
d4f3574e 2926disabled.
c906108c
SS
2927@item
2928Enabled for deletion. The breakpoint stops your program, but
d4f3574e
SS
2929immediately after it does so it is deleted permanently. A breakpoint
2930set with the @code{tbreak} command starts out in this state.
c906108c
SS
2931@end itemize
2932
2933You can use the following commands to enable or disable breakpoints,
2934watchpoints, and catchpoints:
2935
2936@table @code
2937@kindex disable breakpoints
2938@kindex disable
41afff9a 2939@kindex dis @r{(@code{disable})}
c5394b80 2940@item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
c906108c
SS
2941Disable the specified breakpoints---or all breakpoints, if none are
2942listed. A disabled breakpoint has no effect but is not forgotten. All
2943options such as ignore-counts, conditions and commands are remembered in
2944case the breakpoint is enabled again later. You may abbreviate
2945@code{disable} as @code{dis}.
2946
2947@kindex enable breakpoints
2948@kindex enable
c5394b80 2949@item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
c906108c
SS
2950Enable the specified breakpoints (or all defined breakpoints). They
2951become effective once again in stopping your program.
2952
c5394b80 2953@item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
c906108c
SS
2954Enable the specified breakpoints temporarily. @value{GDBN} disables any
2955of these breakpoints immediately after stopping your program.
2956
c5394b80 2957@item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
c906108c
SS
2958Enable the specified breakpoints to work once, then die. @value{GDBN}
2959deletes any of these breakpoints as soon as your program stops there.
2960@end table
2961
d4f3574e
SS
2962@c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2963@c confusing: tbreak is also initially enabled.
c906108c
SS
2964Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2965,Setting breakpoints}), breakpoints that you set are initially enabled;
2966subsequently, they become disabled or enabled only when you use one of
2967the commands above. (The command @code{until} can set and delete a
2968breakpoint of its own, but it does not change the state of your other
2969breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2970stepping}.)
2971
6d2ebf8b 2972@node Conditions
c906108c
SS
2973@subsection Break conditions
2974@cindex conditional breakpoints
2975@cindex breakpoint conditions
2976
2977@c FIXME what is scope of break condition expr? Context where wanted?
5d161b24 2978@c in particular for a watchpoint?
c906108c
SS
2979The simplest sort of breakpoint breaks every time your program reaches a
2980specified place. You can also specify a @dfn{condition} for a
2981breakpoint. A condition is just a Boolean expression in your
2982programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2983a condition evaluates the expression each time your program reaches it,
2984and your program stops only if the condition is @emph{true}.
2985
2986This is the converse of using assertions for program validation; in that
2987situation, you want to stop when the assertion is violated---that is,
2988when the condition is false. In C, if you want to test an assertion expressed
2989by the condition @var{assert}, you should set the condition
2990@samp{! @var{assert}} on the appropriate breakpoint.
2991
2992Conditions are also accepted for watchpoints; you may not need them,
2993since a watchpoint is inspecting the value of an expression anyhow---but
2994it might be simpler, say, to just set a watchpoint on a variable name,
2995and specify a condition that tests whether the new value is an interesting
2996one.
2997
2998Break conditions can have side effects, and may even call functions in
2999your program. This can be useful, for example, to activate functions
3000that log program progress, or to use your own print functions to
3001format special data structures. The effects are completely predictable
3002unless there is another enabled breakpoint at the same address. (In
3003that case, @value{GDBN} might see the other breakpoint first and stop your
3004program without checking the condition of this one.) Note that
d4f3574e
SS
3005breakpoint commands are usually more convenient and flexible than break
3006conditions for the
c906108c
SS
3007purpose of performing side effects when a breakpoint is reached
3008(@pxref{Break Commands, ,Breakpoint command lists}).
3009
3010Break conditions can be specified when a breakpoint is set, by using
3011@samp{if} in the arguments to the @code{break} command. @xref{Set
3012Breaks, ,Setting breakpoints}. They can also be changed at any time
3013with the @code{condition} command.
53a5351d 3014
c906108c
SS
3015You can also use the @code{if} keyword with the @code{watch} command.
3016The @code{catch} command does not recognize the @code{if} keyword;
3017@code{condition} is the only way to impose a further condition on a
3018catchpoint.
c906108c
SS
3019
3020@table @code
3021@kindex condition
3022@item condition @var{bnum} @var{expression}
3023Specify @var{expression} as the break condition for breakpoint,
3024watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3025breakpoint @var{bnum} stops your program only if the value of
3026@var{expression} is true (nonzero, in C). When you use
3027@code{condition}, @value{GDBN} checks @var{expression} immediately for
3028syntactic correctness, and to determine whether symbols in it have
d4f3574e
SS
3029referents in the context of your breakpoint. If @var{expression} uses
3030symbols not referenced in the context of the breakpoint, @value{GDBN}
3031prints an error message:
3032
474c8240 3033@smallexample
d4f3574e 3034No symbol "foo" in current context.
474c8240 3035@end smallexample
d4f3574e
SS
3036
3037@noindent
c906108c
SS
3038@value{GDBN} does
3039not actually evaluate @var{expression} at the time the @code{condition}
d4f3574e
SS
3040command (or a command that sets a breakpoint with a condition, like
3041@code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
c906108c
SS
3042
3043@item condition @var{bnum}
3044Remove the condition from breakpoint number @var{bnum}. It becomes
3045an ordinary unconditional breakpoint.
3046@end table
3047
3048@cindex ignore count (of breakpoint)
3049A special case of a breakpoint condition is to stop only when the
3050breakpoint has been reached a certain number of times. This is so
3051useful that there is a special way to do it, using the @dfn{ignore
3052count} of the breakpoint. Every breakpoint has an ignore count, which
3053is an integer. Most of the time, the ignore count is zero, and
3054therefore has no effect. But if your program reaches a breakpoint whose
3055ignore count is positive, then instead of stopping, it just decrements
3056the ignore count by one and continues. As a result, if the ignore count
3057value is @var{n}, the breakpoint does not stop the next @var{n} times
3058your program reaches it.
3059
3060@table @code
3061@kindex ignore
3062@item ignore @var{bnum} @var{count}
3063Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3064The next @var{count} times the breakpoint is reached, your program's
3065execution does not stop; other than to decrement the ignore count, @value{GDBN}
3066takes no action.
3067
3068To make the breakpoint stop the next time it is reached, specify
3069a count of zero.
3070
3071When you use @code{continue} to resume execution of your program from a
3072breakpoint, you can specify an ignore count directly as an argument to
3073@code{continue}, rather than using @code{ignore}. @xref{Continuing and
3074Stepping,,Continuing and stepping}.
3075
3076If a breakpoint has a positive ignore count and a condition, the
3077condition is not checked. Once the ignore count reaches zero,
3078@value{GDBN} resumes checking the condition.
3079
3080You could achieve the effect of the ignore count with a condition such
3081as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3082is decremented each time. @xref{Convenience Vars, ,Convenience
3083variables}.
3084@end table
3085
3086Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3087
3088
6d2ebf8b 3089@node Break Commands
c906108c
SS
3090@subsection Breakpoint command lists
3091
3092@cindex breakpoint commands
3093You can give any breakpoint (or watchpoint or catchpoint) a series of
3094commands to execute when your program stops due to that breakpoint. For
3095example, you might want to print the values of certain expressions, or
3096enable other breakpoints.
3097
3098@table @code
3099@kindex commands
3100@kindex end
3101@item commands @r{[}@var{bnum}@r{]}
3102@itemx @dots{} @var{command-list} @dots{}
3103@itemx end
3104Specify a list of commands for breakpoint number @var{bnum}. The commands
3105themselves appear on the following lines. Type a line containing just
3106@code{end} to terminate the commands.
3107
3108To remove all commands from a breakpoint, type @code{commands} and
3109follow it immediately with @code{end}; that is, give no commands.
3110
3111With no @var{bnum} argument, @code{commands} refers to the last
3112breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3113recently encountered).
3114@end table
3115
3116Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3117disabled within a @var{command-list}.
3118
3119You can use breakpoint commands to start your program up again. Simply
3120use the @code{continue} command, or @code{step}, or any other command
3121that resumes execution.
3122
3123Any other commands in the command list, after a command that resumes
3124execution, are ignored. This is because any time you resume execution
3125(even with a simple @code{next} or @code{step}), you may encounter
3126another breakpoint---which could have its own command list, leading to
3127ambiguities about which list to execute.
3128
3129@kindex silent
3130If the first command you specify in a command list is @code{silent}, the
3131usual message about stopping at a breakpoint is not printed. This may
3132be desirable for breakpoints that are to print a specific message and
3133then continue. If none of the remaining commands print anything, you
3134see no sign that the breakpoint was reached. @code{silent} is
3135meaningful only at the beginning of a breakpoint command list.
3136
3137The commands @code{echo}, @code{output}, and @code{printf} allow you to
3138print precisely controlled output, and are often useful in silent
3139breakpoints. @xref{Output, ,Commands for controlled output}.
3140
3141For example, here is how you could use breakpoint commands to print the
3142value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3143
474c8240 3144@smallexample
c906108c
SS
3145break foo if x>0
3146commands
3147silent
3148printf "x is %d\n",x
3149cont
3150end
474c8240 3151@end smallexample
c906108c
SS
3152
3153One application for breakpoint commands is to compensate for one bug so
3154you can test for another. Put a breakpoint just after the erroneous line
3155of code, give it a condition to detect the case in which something
3156erroneous has been done, and give it commands to assign correct values
3157to any variables that need them. End with the @code{continue} command
3158so that your program does not stop, and start with the @code{silent}
3159command so that no output is produced. Here is an example:
3160
474c8240 3161@smallexample
c906108c
SS
3162break 403
3163commands
3164silent
3165set x = y + 4
3166cont
3167end
474c8240 3168@end smallexample
c906108c 3169
6d2ebf8b 3170@node Breakpoint Menus
c906108c
SS
3171@subsection Breakpoint menus
3172@cindex overloading
3173@cindex symbol overloading
3174
b37052ae 3175Some programming languages (notably C@t{++}) permit a single function name
c906108c
SS
3176to be defined several times, for application in different contexts.
3177This is called @dfn{overloading}. When a function name is overloaded,
3178@samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3179a breakpoint. If you realize this is a problem, you can use
3180something like @samp{break @var{function}(@var{types})} to specify which
3181particular version of the function you want. Otherwise, @value{GDBN} offers
3182you a menu of numbered choices for different possible breakpoints, and
3183waits for your selection with the prompt @samp{>}. The first two
3184options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3185sets a breakpoint at each definition of @var{function}, and typing
3186@kbd{0} aborts the @code{break} command without setting any new
3187breakpoints.
3188
3189For example, the following session excerpt shows an attempt to set a
3190breakpoint at the overloaded symbol @code{String::after}.
3191We choose three particular definitions of that function name:
3192
3193@c FIXME! This is likely to change to show arg type lists, at least
3194@smallexample
3195@group
3196(@value{GDBP}) b String::after
3197[0] cancel
3198[1] all
3199[2] file:String.cc; line number:867
3200[3] file:String.cc; line number:860
3201[4] file:String.cc; line number:875
3202[5] file:String.cc; line number:853
3203[6] file:String.cc; line number:846
3204[7] file:String.cc; line number:735
3205> 2 4 6
3206Breakpoint 1 at 0xb26c: file String.cc, line 867.
3207Breakpoint 2 at 0xb344: file String.cc, line 875.
3208Breakpoint 3 at 0xafcc: file String.cc, line 846.
3209Multiple breakpoints were set.
3210Use the "delete" command to delete unwanted
3211 breakpoints.
3212(@value{GDBP})
3213@end group
3214@end smallexample
c906108c
SS
3215
3216@c @ifclear BARETARGET
6d2ebf8b 3217@node Error in Breakpoints
d4f3574e 3218@subsection ``Cannot insert breakpoints''
c906108c
SS
3219@c
3220@c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3221@c
d4f3574e
SS
3222Under some operating systems, breakpoints cannot be used in a program if
3223any other process is running that program. In this situation,
5d161b24 3224attempting to run or continue a program with a breakpoint causes
d4f3574e
SS
3225@value{GDBN} to print an error message:
3226
474c8240 3227@smallexample
d4f3574e
SS
3228Cannot insert breakpoints.
3229The same program may be running in another process.
474c8240 3230@end smallexample
d4f3574e
SS
3231
3232When this happens, you have three ways to proceed:
3233
3234@enumerate
3235@item
3236Remove or disable the breakpoints, then continue.
3237
3238@item
5d161b24 3239Suspend @value{GDBN}, and copy the file containing your program to a new
d4f3574e 3240name. Resume @value{GDBN} and use the @code{exec-file} command to specify
5d161b24 3241that @value{GDBN} should run your program under that name.
d4f3574e
SS
3242Then start your program again.
3243
3244@item
3245Relink your program so that the text segment is nonsharable, using the
3246linker option @samp{-N}. The operating system limitation may not apply
3247to nonsharable executables.
3248@end enumerate
c906108c
SS
3249@c @end ifclear
3250
d4f3574e
SS
3251A similar message can be printed if you request too many active
3252hardware-assisted breakpoints and watchpoints:
3253
3254@c FIXME: the precise wording of this message may change; the relevant
3255@c source change is not committed yet (Sep 3, 1999).
3256@smallexample
3257Stopped; cannot insert breakpoints.
3258You may have requested too many hardware breakpoints and watchpoints.
3259@end smallexample
3260
3261@noindent
3262This message is printed when you attempt to resume the program, since
3263only then @value{GDBN} knows exactly how many hardware breakpoints and
3264watchpoints it needs to insert.
3265
3266When this message is printed, you need to disable or remove some of the
3267hardware-assisted breakpoints and watchpoints, and then continue.
3268
3269
6d2ebf8b 3270@node Continuing and Stepping
c906108c
SS
3271@section Continuing and stepping
3272
3273@cindex stepping
3274@cindex continuing
3275@cindex resuming execution
3276@dfn{Continuing} means resuming program execution until your program
3277completes normally. In contrast, @dfn{stepping} means executing just
3278one more ``step'' of your program, where ``step'' may mean either one
3279line of source code, or one machine instruction (depending on what
7a292a7a
SS
3280particular command you use). Either when continuing or when stepping,
3281your program may stop even sooner, due to a breakpoint or a signal. (If
d4f3574e
SS
3282it stops due to a signal, you may want to use @code{handle}, or use
3283@samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
c906108c
SS
3284
3285@table @code
3286@kindex continue
41afff9a
EZ
3287@kindex c @r{(@code{continue})}
3288@kindex fg @r{(resume foreground execution)}
c906108c
SS
3289@item continue @r{[}@var{ignore-count}@r{]}
3290@itemx c @r{[}@var{ignore-count}@r{]}
3291@itemx fg @r{[}@var{ignore-count}@r{]}
3292Resume program execution, at the address where your program last stopped;
3293any breakpoints set at that address are bypassed. The optional argument
3294@var{ignore-count} allows you to specify a further number of times to
3295ignore a breakpoint at this location; its effect is like that of
3296@code{ignore} (@pxref{Conditions, ,Break conditions}).
3297
3298The argument @var{ignore-count} is meaningful only when your program
3299stopped due to a breakpoint. At other times, the argument to
3300@code{continue} is ignored.
3301
d4f3574e
SS
3302The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3303debugged program is deemed to be the foreground program) are provided
3304purely for convenience, and have exactly the same behavior as
3305@code{continue}.
c906108c
SS
3306@end table
3307
3308To resume execution at a different place, you can use @code{return}
3309(@pxref{Returning, ,Returning from a function}) to go back to the
3310calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3311different address}) to go to an arbitrary location in your program.
3312
3313A typical technique for using stepping is to set a breakpoint
3314(@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3315beginning of the function or the section of your program where a problem
3316is believed to lie, run your program until it stops at that breakpoint,
3317and then step through the suspect area, examining the variables that are
3318interesting, until you see the problem happen.
3319
3320@table @code
3321@kindex step
41afff9a 3322@kindex s @r{(@code{step})}
c906108c
SS
3323@item step
3324Continue running your program until control reaches a different source
3325line, then stop it and return control to @value{GDBN}. This command is
3326abbreviated @code{s}.
3327
3328@quotation
3329@c "without debugging information" is imprecise; actually "without line
3330@c numbers in the debugging information". (gcc -g1 has debugging info but
3331@c not line numbers). But it seems complex to try to make that
3332@c distinction here.
3333@emph{Warning:} If you use the @code{step} command while control is
3334within a function that was compiled without debugging information,
3335execution proceeds until control reaches a function that does have
3336debugging information. Likewise, it will not step into a function which
3337is compiled without debugging information. To step through functions
3338without debugging information, use the @code{stepi} command, described
3339below.
3340@end quotation
3341
4a92d011
EZ
3342The @code{step} command only stops at the first instruction of a source
3343line. This prevents the multiple stops that could otherwise occur in
3344@code{switch} statements, @code{for} loops, etc. @code{step} continues
3345to stop if a function that has debugging information is called within
3346the line. In other words, @code{step} @emph{steps inside} any functions
3347called within the line.
c906108c 3348
d4f3574e
SS
3349Also, the @code{step} command only enters a function if there is line
3350number information for the function. Otherwise it acts like the
5d161b24 3351@code{next} command. This avoids problems when using @code{cc -gl}
c906108c 3352on MIPS machines. Previously, @code{step} entered subroutines if there
5d161b24 3353was any debugging information about the routine.
c906108c
SS
3354
3355@item step @var{count}
3356Continue running as in @code{step}, but do so @var{count} times. If a
7a292a7a
SS
3357breakpoint is reached, or a signal not related to stepping occurs before
3358@var{count} steps, stepping stops right away.
c906108c
SS
3359
3360@kindex next
41afff9a 3361@kindex n @r{(@code{next})}
c906108c
SS
3362@item next @r{[}@var{count}@r{]}
3363Continue to the next source line in the current (innermost) stack frame.
7a292a7a
SS
3364This is similar to @code{step}, but function calls that appear within
3365the line of code are executed without stopping. Execution stops when
3366control reaches a different line of code at the original stack level
3367that was executing when you gave the @code{next} command. This command
3368is abbreviated @code{n}.
c906108c
SS
3369
3370An argument @var{count} is a repeat count, as for @code{step}.
3371
3372
3373@c FIX ME!! Do we delete this, or is there a way it fits in with
3374@c the following paragraph? --- Vctoria
3375@c
3376@c @code{next} within a function that lacks debugging information acts like
3377@c @code{step}, but any function calls appearing within the code of the
3378@c function are executed without stopping.
3379
d4f3574e
SS
3380The @code{next} command only stops at the first instruction of a
3381source line. This prevents multiple stops that could otherwise occur in
4a92d011 3382@code{switch} statements, @code{for} loops, etc.
c906108c 3383
b90a5f51
CF
3384@kindex set step-mode
3385@item set step-mode
3386@cindex functions without line info, and stepping
3387@cindex stepping into functions with no line info
3388@itemx set step-mode on
4a92d011 3389The @code{set step-mode on} command causes the @code{step} command to
b90a5f51
CF
3390stop at the first instruction of a function which contains no debug line
3391information rather than stepping over it.
3392
4a92d011
EZ
3393This is useful in cases where you may be interested in inspecting the
3394machine instructions of a function which has no symbolic info and do not
3395want @value{GDBN} to automatically skip over this function.
b90a5f51
CF
3396
3397@item set step-mode off
4a92d011 3398Causes the @code{step} command to step over any functions which contains no
b90a5f51
CF
3399debug information. This is the default.
3400
c906108c
SS
3401@kindex finish
3402@item finish
3403Continue running until just after function in the selected stack frame
3404returns. Print the returned value (if any).
3405
3406Contrast this with the @code{return} command (@pxref{Returning,
3407,Returning from a function}).
3408
3409@kindex until
41afff9a 3410@kindex u @r{(@code{until})}
c906108c
SS
3411@item until
3412@itemx u
3413Continue running until a source line past the current line, in the
3414current stack frame, is reached. This command is used to avoid single
3415stepping through a loop more than once. It is like the @code{next}
3416command, except that when @code{until} encounters a jump, it
3417automatically continues execution until the program counter is greater
3418than the address of the jump.
3419
3420This means that when you reach the end of a loop after single stepping
3421though it, @code{until} makes your program continue execution until it
3422exits the loop. In contrast, a @code{next} command at the end of a loop
3423simply steps back to the beginning of the loop, which forces you to step
3424through the next iteration.
3425
3426@code{until} always stops your program if it attempts to exit the current
3427stack frame.
3428
3429@code{until} may produce somewhat counterintuitive results if the order
3430of machine code does not match the order of the source lines. For
3431example, in the following excerpt from a debugging session, the @code{f}
3432(@code{frame}) command shows that execution is stopped at line
3433@code{206}; yet when we use @code{until}, we get to line @code{195}:
3434
474c8240 3435@smallexample
c906108c
SS
3436(@value{GDBP}) f
3437#0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3438206 expand_input();
3439(@value{GDBP}) until
3440195 for ( ; argc > 0; NEXTARG) @{
474c8240 3441@end smallexample
c906108c
SS
3442
3443This happened because, for execution efficiency, the compiler had
3444generated code for the loop closure test at the end, rather than the
3445start, of the loop---even though the test in a C @code{for}-loop is
3446written before the body of the loop. The @code{until} command appeared
3447to step back to the beginning of the loop when it advanced to this
3448expression; however, it has not really gone to an earlier
3449statement---not in terms of the actual machine code.
3450
3451@code{until} with no argument works by means of single
3452instruction stepping, and hence is slower than @code{until} with an
3453argument.
3454
3455@item until @var{location}
3456@itemx u @var{location}
3457Continue running your program until either the specified location is
3458reached, or the current stack frame returns. @var{location} is any of
3459the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3460,Setting breakpoints}). This form of the command uses breakpoints,
3461and hence is quicker than @code{until} without an argument.
3462
3463@kindex stepi
41afff9a 3464@kindex si @r{(@code{stepi})}
c906108c 3465@item stepi
96a2c332 3466@itemx stepi @var{arg}
c906108c
SS
3467@itemx si
3468Execute one machine instruction, then stop and return to the debugger.
3469
3470It is often useful to do @samp{display/i $pc} when stepping by machine
3471instructions. This makes @value{GDBN} automatically display the next
3472instruction to be executed, each time your program stops. @xref{Auto
3473Display,, Automatic display}.
3474
3475An argument is a repeat count, as in @code{step}.
3476
3477@need 750
3478@kindex nexti
41afff9a 3479@kindex ni @r{(@code{nexti})}
c906108c 3480@item nexti
96a2c332 3481@itemx nexti @var{arg}
c906108c
SS
3482@itemx ni
3483Execute one machine instruction, but if it is a function call,
3484proceed until the function returns.
3485
3486An argument is a repeat count, as in @code{next}.
3487@end table
3488
6d2ebf8b 3489@node Signals
c906108c
SS
3490@section Signals
3491@cindex signals
3492
3493A signal is an asynchronous event that can happen in a program. The
3494operating system defines the possible kinds of signals, and gives each
3495kind a name and a number. For example, in Unix @code{SIGINT} is the
d4f3574e 3496signal a program gets when you type an interrupt character (often @kbd{C-c});
c906108c
SS
3497@code{SIGSEGV} is the signal a program gets from referencing a place in
3498memory far away from all the areas in use; @code{SIGALRM} occurs when
3499the alarm clock timer goes off (which happens only if your program has
3500requested an alarm).
3501
3502@cindex fatal signals
3503Some signals, including @code{SIGALRM}, are a normal part of the
3504functioning of your program. Others, such as @code{SIGSEGV}, indicate
d4f3574e 3505errors; these signals are @dfn{fatal} (they kill your program immediately) if the
c906108c
SS
3506program has not specified in advance some other way to handle the signal.
3507@code{SIGINT} does not indicate an error in your program, but it is normally
3508fatal so it can carry out the purpose of the interrupt: to kill the program.
3509
3510@value{GDBN} has the ability to detect any occurrence of a signal in your
3511program. You can tell @value{GDBN} in advance what to do for each kind of
3512signal.
3513
3514@cindex handling signals
24f93129
EZ
3515Normally, @value{GDBN} is set up to let the non-erroneous signals like
3516@code{SIGALRM} be silently passed to your program
3517(so as not to interfere with their role in the program's functioning)
c906108c
SS
3518but to stop your program immediately whenever an error signal happens.
3519You can change these settings with the @code{handle} command.
3520
3521@table @code
3522@kindex info signals
3523@item info signals
96a2c332 3524@itemx info handle
c906108c
SS
3525Print a table of all the kinds of signals and how @value{GDBN} has been told to
3526handle each one. You can use this to see the signal numbers of all
3527the defined types of signals.
3528
d4f3574e 3529@code{info handle} is an alias for @code{info signals}.
c906108c
SS
3530
3531@kindex handle
3532@item handle @var{signal} @var{keywords}@dots{}
5ece1a18
EZ
3533Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3534can be the number of a signal or its name (with or without the
24f93129 3535@samp{SIG} at the beginning); a list of signal numbers of the form
5ece1a18
EZ
3536@samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3537known signals. The @var{keywords} say what change to make.
c906108c
SS
3538@end table
3539
3540@c @group
3541The keywords allowed by the @code{handle} command can be abbreviated.
3542Their full names are:
3543
3544@table @code
3545@item nostop
3546@value{GDBN} should not stop your program when this signal happens. It may
3547still print a message telling you that the signal has come in.
3548
3549@item stop
3550@value{GDBN} should stop your program when this signal happens. This implies
3551the @code{print} keyword as well.
3552
3553@item print
3554@value{GDBN} should print a message when this signal happens.
3555
3556@item noprint
3557@value{GDBN} should not mention the occurrence of the signal at all. This
3558implies the @code{nostop} keyword as well.
3559
3560@item pass
5ece1a18 3561@itemx noignore
c906108c
SS
3562@value{GDBN} should allow your program to see this signal; your program
3563can handle the signal, or else it may terminate if the signal is fatal
5ece1a18 3564and not handled. @code{pass} and @code{noignore} are synonyms.
c906108c
SS
3565
3566@item nopass
5ece1a18 3567@itemx ignore
c906108c 3568@value{GDBN} should not allow your program to see this signal.
5ece1a18 3569@code{nopass} and @code{ignore} are synonyms.
c906108c
SS
3570@end table
3571@c @end group
3572
d4f3574e
SS
3573When a signal stops your program, the signal is not visible to the
3574program until you
c906108c
SS
3575continue. Your program sees the signal then, if @code{pass} is in
3576effect for the signal in question @emph{at that time}. In other words,
3577after @value{GDBN} reports a signal, you can use the @code{handle}
3578command with @code{pass} or @code{nopass} to control whether your
3579program sees that signal when you continue.
3580
24f93129
EZ
3581The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3582non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3583@code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3584erroneous signals.
3585
c906108c
SS
3586You can also use the @code{signal} command to prevent your program from
3587seeing a signal, or cause it to see a signal it normally would not see,
3588or to give it any signal at any time. For example, if your program stopped
3589due to some sort of memory reference error, you might store correct
3590values into the erroneous variables and continue, hoping to see more
3591execution; but your program would probably terminate immediately as
3592a result of the fatal signal once it saw the signal. To prevent this,
3593you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5d161b24 3594program a signal}.
c906108c 3595
6d2ebf8b 3596@node Thread Stops
c906108c
SS
3597@section Stopping and starting multi-thread programs
3598
3599When your program has multiple threads (@pxref{Threads,, Debugging
3600programs with multiple threads}), you can choose whether to set
3601breakpoints on all threads, or on a particular thread.
3602
3603@table @code
3604@cindex breakpoints and threads
3605@cindex thread breakpoints
3606@kindex break @dots{} thread @var{threadno}
3607@item break @var{linespec} thread @var{threadno}
3608@itemx break @var{linespec} thread @var{threadno} if @dots{}
3609@var{linespec} specifies source lines; there are several ways of
3610writing them, but the effect is always to specify some source line.
3611
3612Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3613to specify that you only want @value{GDBN} to stop the program when a
3614particular thread reaches this breakpoint. @var{threadno} is one of the
3615numeric thread identifiers assigned by @value{GDBN}, shown in the first
3616column of the @samp{info threads} display.
3617
3618If you do not specify @samp{thread @var{threadno}} when you set a
3619breakpoint, the breakpoint applies to @emph{all} threads of your
3620program.
3621
3622You can use the @code{thread} qualifier on conditional breakpoints as
3623well; in this case, place @samp{thread @var{threadno}} before the
3624breakpoint condition, like this:
3625
3626@smallexample
2df3850c 3627(@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
c906108c
SS
3628@end smallexample
3629
3630@end table
3631
3632@cindex stopped threads
3633@cindex threads, stopped
3634Whenever your program stops under @value{GDBN} for any reason,
3635@emph{all} threads of execution stop, not just the current thread. This
3636allows you to examine the overall state of the program, including
3637switching between threads, without worrying that things may change
3638underfoot.
3639
3640@cindex continuing threads
3641@cindex threads, continuing
3642Conversely, whenever you restart the program, @emph{all} threads start
3643executing. @emph{This is true even when single-stepping} with commands
5d161b24 3644like @code{step} or @code{next}.
c906108c
SS
3645
3646In particular, @value{GDBN} cannot single-step all threads in lockstep.
3647Since thread scheduling is up to your debugging target's operating
3648system (not controlled by @value{GDBN}), other threads may
3649execute more than one statement while the current thread completes a
3650single step. Moreover, in general other threads stop in the middle of a
3651statement, rather than at a clean statement boundary, when the program
3652stops.
3653
3654You might even find your program stopped in another thread after
3655continuing or even single-stepping. This happens whenever some other
3656thread runs into a breakpoint, a signal, or an exception before the
3657first thread completes whatever you requested.
3658
3659On some OSes, you can lock the OS scheduler and thus allow only a single
3660thread to run.
3661
3662@table @code
3663@item set scheduler-locking @var{mode}
3664Set the scheduler locking mode. If it is @code{off}, then there is no
3665locking and any thread may run at any time. If @code{on}, then only the
3666current thread may run when the inferior is resumed. The @code{step}
3667mode optimizes for single-stepping. It stops other threads from
3668``seizing the prompt'' by preempting the current thread while you are
3669stepping. Other threads will only rarely (or never) get a chance to run
d4f3574e 3670when you step. They are more likely to run when you @samp{next} over a
c906108c 3671function call, and they are completely free to run when you use commands
d4f3574e 3672like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
c906108c 3673thread hits a breakpoint during its timeslice, they will never steal the
2df3850c 3674@value{GDBN} prompt away from the thread that you are debugging.
c906108c
SS
3675
3676@item show scheduler-locking
3677Display the current scheduler locking mode.
3678@end table
3679
c906108c 3680
6d2ebf8b 3681@node Stack
c906108c
SS
3682@chapter Examining the Stack
3683
3684When your program has stopped, the first thing you need to know is where it
3685stopped and how it got there.
3686
3687@cindex call stack
5d161b24
DB
3688Each time your program performs a function call, information about the call
3689is generated.
3690That information includes the location of the call in your program,
3691the arguments of the call,
c906108c 3692and the local variables of the function being called.
5d161b24 3693The information is saved in a block of data called a @dfn{stack frame}.
c906108c
SS
3694The stack frames are allocated in a region of memory called the @dfn{call
3695stack}.
3696
3697When your program stops, the @value{GDBN} commands for examining the
3698stack allow you to see all of this information.
3699
3700@cindex selected frame
3701One of the stack frames is @dfn{selected} by @value{GDBN} and many
3702@value{GDBN} commands refer implicitly to the selected frame. In
3703particular, whenever you ask @value{GDBN} for the value of a variable in
3704your program, the value is found in the selected frame. There are
3705special @value{GDBN} commands to select whichever frame you are
3706interested in. @xref{Selection, ,Selecting a frame}.
3707
3708When your program stops, @value{GDBN} automatically selects the
5d161b24 3709currently executing frame and describes it briefly, similar to the
c906108c
SS
3710@code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3711
3712@menu
3713* Frames:: Stack frames
3714* Backtrace:: Backtraces
3715* Selection:: Selecting a frame
3716* Frame Info:: Information on a frame
c906108c
SS
3717
3718@end menu
3719
6d2ebf8b 3720@node Frames
c906108c
SS
3721@section Stack frames
3722
d4f3574e 3723@cindex frame, definition
c906108c
SS
3724@cindex stack frame
3725The call stack is divided up into contiguous pieces called @dfn{stack
3726frames}, or @dfn{frames} for short; each frame is the data associated
3727with one call to one function. The frame contains the arguments given
3728to the function, the function's local variables, and the address at
3729which the function is executing.
3730
3731@cindex initial frame
3732@cindex outermost frame
3733@cindex innermost frame
3734When your program is started, the stack has only one frame, that of the
3735function @code{main}. This is called the @dfn{initial} frame or the
3736@dfn{outermost} frame. Each time a function is called, a new frame is
3737made. Each time a function returns, the frame for that function invocation
3738is eliminated. If a function is recursive, there can be many frames for
3739the same function. The frame for the function in which execution is
3740actually occurring is called the @dfn{innermost} frame. This is the most
3741recently created of all the stack frames that still exist.
3742
3743@cindex frame pointer
3744Inside your program, stack frames are identified by their addresses. A
3745stack frame consists of many bytes, each of which has its own address; each
3746kind of computer has a convention for choosing one byte whose
3747address serves as the address of the frame. Usually this address is kept
3748in a register called the @dfn{frame pointer register} while execution is
3749going on in that frame.
3750
3751@cindex frame number
3752@value{GDBN} assigns numbers to all existing stack frames, starting with
3753zero for the innermost frame, one for the frame that called it,
3754and so on upward. These numbers do not really exist in your program;
3755they are assigned by @value{GDBN} to give you a way of designating stack
3756frames in @value{GDBN} commands.
3757
6d2ebf8b
SS
3758@c The -fomit-frame-pointer below perennially causes hbox overflow
3759@c underflow problems.
c906108c
SS
3760@cindex frameless execution
3761Some compilers provide a way to compile functions so that they operate
6d2ebf8b 3762without stack frames. (For example, the @value{GCC} option
474c8240 3763@smallexample
6d2ebf8b 3764@samp{-fomit-frame-pointer}
474c8240 3765@end smallexample
6d2ebf8b 3766generates functions without a frame.)
c906108c
SS
3767This is occasionally done with heavily used library functions to save
3768the frame setup time. @value{GDBN} has limited facilities for dealing
3769with these function invocations. If the innermost function invocation
3770has no stack frame, @value{GDBN} nevertheless regards it as though
3771it had a separate frame, which is numbered zero as usual, allowing
3772correct tracing of the function call chain. However, @value{GDBN} has
3773no provision for frameless functions elsewhere in the stack.
3774
3775@table @code
d4f3574e 3776@kindex frame@r{, command}
41afff9a 3777@cindex current stack frame
c906108c 3778@item frame @var{args}
5d161b24 3779The @code{frame} command allows you to move from one stack frame to another,
c906108c 3780and to print the stack frame you select. @var{args} may be either the
5d161b24
DB
3781address of the frame or the stack frame number. Without an argument,
3782@code{frame} prints the current stack frame.
c906108c
SS
3783
3784@kindex select-frame
41afff9a 3785@cindex selecting frame silently
c906108c
SS
3786@item select-frame
3787The @code{select-frame} command allows you to move from one stack frame
3788to another without printing the frame. This is the silent version of
3789@code{frame}.
3790@end table
3791
6d2ebf8b 3792@node Backtrace
c906108c
SS
3793@section Backtraces
3794
3795@cindex backtraces
3796@cindex tracebacks
3797@cindex stack traces
3798A backtrace is a summary of how your program got where it is. It shows one
3799line per frame, for many frames, starting with the currently executing
3800frame (frame zero), followed by its caller (frame one), and on up the
3801stack.
3802
3803@table @code
3804@kindex backtrace
41afff9a 3805@kindex bt @r{(@code{backtrace})}
c906108c
SS
3806@item backtrace
3807@itemx bt
3808Print a backtrace of the entire stack: one line per frame for all
3809frames in the stack.
3810
3811You can stop the backtrace at any time by typing the system interrupt
3812character, normally @kbd{C-c}.
3813
3814@item backtrace @var{n}
3815@itemx bt @var{n}
3816Similar, but print only the innermost @var{n} frames.
3817
3818@item backtrace -@var{n}
3819@itemx bt -@var{n}
3820Similar, but print only the outermost @var{n} frames.
3821@end table
3822
3823@kindex where
3824@kindex info stack
41afff9a 3825@kindex info s @r{(@code{info stack})}
c906108c
SS
3826The names @code{where} and @code{info stack} (abbreviated @code{info s})
3827are additional aliases for @code{backtrace}.
3828
3829Each line in the backtrace shows the frame number and the function name.
3830The program counter value is also shown---unless you use @code{set
3831print address off}. The backtrace also shows the source file name and
3832line number, as well as the arguments to the function. The program
3833counter value is omitted if it is at the beginning of the code for that
3834line number.
3835
3836Here is an example of a backtrace. It was made with the command
3837@samp{bt 3}, so it shows the innermost three frames.
3838
3839@smallexample
3840@group
5d161b24 3841#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
c906108c
SS
3842 at builtin.c:993
3843#1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3844#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3845 at macro.c:71
3846(More stack frames follow...)
3847@end group
3848@end smallexample
3849
3850@noindent
3851The display for frame zero does not begin with a program counter
3852value, indicating that your program has stopped at the beginning of the
3853code for line @code{993} of @code{builtin.c}.
3854
6d2ebf8b 3855@node Selection
c906108c
SS
3856@section Selecting a frame
3857
3858Most commands for examining the stack and other data in your program work on
3859whichever stack frame is selected at the moment. Here are the commands for
3860selecting a stack frame; all of them finish by printing a brief description
3861of the stack frame just selected.
3862
3863@table @code
d4f3574e 3864@kindex frame@r{, selecting}
41afff9a 3865@kindex f @r{(@code{frame})}
c906108c
SS
3866@item frame @var{n}
3867@itemx f @var{n}
3868Select frame number @var{n}. Recall that frame zero is the innermost
3869(currently executing) frame, frame one is the frame that called the
3870innermost one, and so on. The highest-numbered frame is the one for
3871@code{main}.
3872
3873@item frame @var{addr}
3874@itemx f @var{addr}
3875Select the frame at address @var{addr}. This is useful mainly if the
3876chaining of stack frames has been damaged by a bug, making it
3877impossible for @value{GDBN} to assign numbers properly to all frames. In
3878addition, this can be useful when your program has multiple stacks and
3879switches between them.
3880
c906108c
SS
3881On the SPARC architecture, @code{frame} needs two addresses to
3882select an arbitrary frame: a frame pointer and a stack pointer.
3883
3884On the MIPS and Alpha architecture, it needs two addresses: a stack
3885pointer and a program counter.
3886
3887On the 29k architecture, it needs three addresses: a register stack
3888pointer, a program counter, and a memory stack pointer.
3889@c note to future updaters: this is conditioned on a flag
3890@c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3891@c as of 27 Jan 1994.
c906108c
SS
3892
3893@kindex up
3894@item up @var{n}
3895Move @var{n} frames up the stack. For positive numbers @var{n}, this
3896advances toward the outermost frame, to higher frame numbers, to frames
3897that have existed longer. @var{n} defaults to one.
3898
3899@kindex down
41afff9a 3900@kindex do @r{(@code{down})}
c906108c
SS
3901@item down @var{n}
3902Move @var{n} frames down the stack. For positive numbers @var{n}, this
3903advances toward the innermost frame, to lower frame numbers, to frames
3904that were created more recently. @var{n} defaults to one. You may
3905abbreviate @code{down} as @code{do}.
3906@end table
3907
3908All of these commands end by printing two lines of output describing the
3909frame. The first line shows the frame number, the function name, the
3910arguments, and the source file and line number of execution in that
5d161b24 3911frame. The second line shows the text of that source line.
c906108c
SS
3912
3913@need 1000
3914For example:
3915
3916@smallexample
3917@group
3918(@value{GDBP}) up
3919#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3920 at env.c:10
392110 read_input_file (argv[i]);
3922@end group
3923@end smallexample
3924
3925After such a printout, the @code{list} command with no arguments
3926prints ten lines centered on the point of execution in the frame.
3927@xref{List, ,Printing source lines}.
3928
3929@table @code
3930@kindex down-silently
3931@kindex up-silently
3932@item up-silently @var{n}
3933@itemx down-silently @var{n}
3934These two commands are variants of @code{up} and @code{down},
3935respectively; they differ in that they do their work silently, without
3936causing display of the new frame. They are intended primarily for use
3937in @value{GDBN} command scripts, where the output might be unnecessary and
3938distracting.
3939@end table
3940
6d2ebf8b 3941@node Frame Info
c906108c
SS
3942@section Information about a frame
3943
3944There are several other commands to print information about the selected
3945stack frame.
3946
3947@table @code
3948@item frame
3949@itemx f
3950When used without any argument, this command does not change which
3951frame is selected, but prints a brief description of the currently
3952selected stack frame. It can be abbreviated @code{f}. With an
3953argument, this command is used to select a stack frame.
3954@xref{Selection, ,Selecting a frame}.
3955
3956@kindex info frame
41afff9a 3957@kindex info f @r{(@code{info frame})}
c906108c
SS
3958@item info frame
3959@itemx info f
3960This command prints a verbose description of the selected stack frame,
3961including:
3962
3963@itemize @bullet
5d161b24
DB
3964@item
3965the address of the frame
c906108c
SS
3966@item
3967the address of the next frame down (called by this frame)
3968@item
3969the address of the next frame up (caller of this frame)
3970@item
3971the language in which the source code corresponding to this frame is written
3972@item
3973the address of the frame's arguments
3974@item
d4f3574e
SS
3975the address of the frame's local variables
3976@item
c906108c
SS
3977the program counter saved in it (the address of execution in the caller frame)
3978@item
3979which registers were saved in the frame
3980@end itemize
3981
3982@noindent The verbose description is useful when
3983something has gone wrong that has made the stack format fail to fit
3984the usual conventions.
3985
3986@item info frame @var{addr}
3987@itemx info f @var{addr}
3988Print a verbose description of the frame at address @var{addr}, without
3989selecting that frame. The selected frame remains unchanged by this
3990command. This requires the same kind of address (more than one for some
3991architectures) that you specify in the @code{frame} command.
3992@xref{Selection, ,Selecting a frame}.
3993
3994@kindex info args
3995@item info args
3996Print the arguments of the selected frame, each on a separate line.
3997
3998@item info locals
3999@kindex info locals
4000Print the local variables of the selected frame, each on a separate
4001line. These are all variables (declared either static or automatic)
4002accessible at the point of execution of the selected frame.
4003
c906108c 4004@kindex info catch
d4f3574e
SS
4005@cindex catch exceptions, list active handlers
4006@cindex exception handlers, how to list
c906108c
SS
4007@item info catch
4008Print a list of all the exception handlers that are active in the
4009current stack frame at the current point of execution. To see other
4010exception handlers, visit the associated frame (using the @code{up},
4011@code{down}, or @code{frame} commands); then type @code{info catch}.
4012@xref{Set Catchpoints, , Setting catchpoints}.
53a5351d 4013
c906108c
SS
4014@end table
4015
c906108c 4016
6d2ebf8b 4017@node Source
c906108c
SS
4018@chapter Examining Source Files
4019
4020@value{GDBN} can print parts of your program's source, since the debugging
4021information recorded in the program tells @value{GDBN} what source files were
4022used to build it. When your program stops, @value{GDBN} spontaneously prints
4023the line where it stopped. Likewise, when you select a stack frame
4024(@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4025execution in that frame has stopped. You can print other portions of
4026source files by explicit command.
4027
7a292a7a 4028If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
d4f3574e 4029prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7a292a7a 4030@value{GDBN} under @sc{gnu} Emacs}.
c906108c
SS
4031
4032@menu
4033* List:: Printing source lines
c906108c 4034* Search:: Searching source files
c906108c
SS
4035* Source Path:: Specifying source directories
4036* Machine Code:: Source and machine code
4037@end menu
4038
6d2ebf8b 4039@node List
c906108c
SS
4040@section Printing source lines
4041
4042@kindex list
41afff9a 4043@kindex l @r{(@code{list})}
c906108c 4044To print lines from a source file, use the @code{list} command
5d161b24 4045(abbreviated @code{l}). By default, ten lines are printed.
c906108c
SS
4046There are several ways to specify what part of the file you want to print.
4047
4048Here are the forms of the @code{list} command most commonly used:
4049
4050@table @code
4051@item list @var{linenum}
4052Print lines centered around line number @var{linenum} in the
4053current source file.
4054
4055@item list @var{function}
4056Print lines centered around the beginning of function
4057@var{function}.
4058
4059@item list
4060Print more lines. If the last lines printed were printed with a
4061@code{list} command, this prints lines following the last lines
4062printed; however, if the last line printed was a solitary line printed
4063as part of displaying a stack frame (@pxref{Stack, ,Examining the
4064Stack}), this prints lines centered around that line.
4065
4066@item list -
4067Print lines just before the lines last printed.
4068@end table
4069
4070By default, @value{GDBN} prints ten source lines with any of these forms of
4071the @code{list} command. You can change this using @code{set listsize}:
4072
4073@table @code
4074@kindex set listsize
4075@item set listsize @var{count}
4076Make the @code{list} command display @var{count} source lines (unless
4077the @code{list} argument explicitly specifies some other number).
4078
4079@kindex show listsize
4080@item show listsize
4081Display the number of lines that @code{list} prints.
4082@end table
4083
4084Repeating a @code{list} command with @key{RET} discards the argument,
4085so it is equivalent to typing just @code{list}. This is more useful
4086than listing the same lines again. An exception is made for an
4087argument of @samp{-}; that argument is preserved in repetition so that
4088each repetition moves up in the source file.
4089
4090@cindex linespec
4091In general, the @code{list} command expects you to supply zero, one or two
4092@dfn{linespecs}. Linespecs specify source lines; there are several ways
d4f3574e 4093of writing them, but the effect is always to specify some source line.
c906108c
SS
4094Here is a complete description of the possible arguments for @code{list}:
4095
4096@table @code
4097@item list @var{linespec}
4098Print lines centered around the line specified by @var{linespec}.
4099
4100@item list @var{first},@var{last}
4101Print lines from @var{first} to @var{last}. Both arguments are
4102linespecs.
4103
4104@item list ,@var{last}
4105Print lines ending with @var{last}.
4106
4107@item list @var{first},
4108Print lines starting with @var{first}.
4109
4110@item list +
4111Print lines just after the lines last printed.
4112
4113@item list -
4114Print lines just before the lines last printed.
4115
4116@item list
4117As described in the preceding table.
4118@end table
4119
4120Here are the ways of specifying a single source line---all the
4121kinds of linespec.
4122
4123@table @code
4124@item @var{number}
4125Specifies line @var{number} of the current source file.
4126When a @code{list} command has two linespecs, this refers to
4127the same source file as the first linespec.
4128
4129@item +@var{offset}
4130Specifies the line @var{offset} lines after the last line printed.
4131When used as the second linespec in a @code{list} command that has
4132two, this specifies the line @var{offset} lines down from the
4133first linespec.
4134
4135@item -@var{offset}
4136Specifies the line @var{offset} lines before the last line printed.
4137
4138@item @var{filename}:@var{number}
4139Specifies line @var{number} in the source file @var{filename}.
4140
4141@item @var{function}
4142Specifies the line that begins the body of the function @var{function}.
4143For example: in C, this is the line with the open brace.
4144
4145@item @var{filename}:@var{function}
4146Specifies the line of the open-brace that begins the body of the
4147function @var{function} in the file @var{filename}. You only need the
4148file name with a function name to avoid ambiguity when there are
4149identically named functions in different source files.
4150
4151@item *@var{address}
4152Specifies the line containing the program address @var{address}.
4153@var{address} may be any expression.
4154@end table
4155
6d2ebf8b 4156@node Search
c906108c
SS
4157@section Searching source files
4158@cindex searching
4159@kindex reverse-search
4160
4161There are two commands for searching through the current source file for a
4162regular expression.
4163
4164@table @code
4165@kindex search
4166@kindex forward-search
4167@item forward-search @var{regexp}
4168@itemx search @var{regexp}
4169The command @samp{forward-search @var{regexp}} checks each line,
4170starting with the one following the last line listed, for a match for
5d161b24 4171@var{regexp}. It lists the line that is found. You can use the
c906108c
SS
4172synonym @samp{search @var{regexp}} or abbreviate the command name as
4173@code{fo}.
4174
4175@item reverse-search @var{regexp}
4176The command @samp{reverse-search @var{regexp}} checks each line, starting
4177with the one before the last line listed and going backward, for a match
4178for @var{regexp}. It lists the line that is found. You can abbreviate
4179this command as @code{rev}.
4180@end table
c906108c 4181
6d2ebf8b 4182@node Source Path
c906108c
SS
4183@section Specifying source directories
4184
4185@cindex source path
4186@cindex directories for source files
4187Executable programs sometimes do not record the directories of the source
4188files from which they were compiled, just the names. Even when they do,
4189the directories could be moved between the compilation and your debugging
4190session. @value{GDBN} has a list of directories to search for source files;
4191this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4192it tries all the directories in the list, in the order they are present
4193in the list, until it finds a file with the desired name. Note that
4194the executable search path is @emph{not} used for this purpose. Neither is
4195the current working directory, unless it happens to be in the source
4196path.
4197
4198If @value{GDBN} cannot find a source file in the source path, and the
4199object program records a directory, @value{GDBN} tries that directory
4200too. If the source path is empty, and there is no record of the
4201compilation directory, @value{GDBN} looks in the current directory as a
4202last resort.
4203
4204Whenever you reset or rearrange the source path, @value{GDBN} clears out
4205any information it has cached about where source files are found and where
4206each line is in the file.
4207
4208@kindex directory
4209@kindex dir
d4f3574e
SS
4210When you start @value{GDBN}, its source path includes only @samp{cdir}
4211and @samp{cwd}, in that order.
c906108c
SS
4212To add other directories, use the @code{directory} command.
4213
4214@table @code
4215@item directory @var{dirname} @dots{}
4216@item dir @var{dirname} @dots{}
4217Add directory @var{dirname} to the front of the source path. Several
d4f3574e
SS
4218directory names may be given to this command, separated by @samp{:}
4219(@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4220part of absolute file names) or
c906108c
SS
4221whitespace. You may specify a directory that is already in the source
4222path; this moves it forward, so @value{GDBN} searches it sooner.
4223
4224@kindex cdir
4225@kindex cwd
41afff9a
EZ
4226@vindex $cdir@r{, convenience variable}
4227@vindex $cwdr@r{, convenience variable}
c906108c
SS
4228@cindex compilation directory
4229@cindex current directory
4230@cindex working directory
4231@cindex directory, current
4232@cindex directory, compilation
4233You can use the string @samp{$cdir} to refer to the compilation
4234directory (if one is recorded), and @samp{$cwd} to refer to the current
4235working directory. @samp{$cwd} is not the same as @samp{.}---the former
4236tracks the current working directory as it changes during your @value{GDBN}
4237session, while the latter is immediately expanded to the current
4238directory at the time you add an entry to the source path.
4239
4240@item directory
4241Reset the source path to empty again. This requires confirmation.
4242
4243@c RET-repeat for @code{directory} is explicitly disabled, but since
4244@c repeating it would be a no-op we do not say that. (thanks to RMS)
4245
4246@item show directories
4247@kindex show directories
4248Print the source path: show which directories it contains.
4249@end table
4250
4251If your source path is cluttered with directories that are no longer of
4252interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4253versions of source. You can correct the situation as follows:
4254
4255@enumerate
4256@item
4257Use @code{directory} with no argument to reset the source path to empty.
4258
4259@item
4260Use @code{directory} with suitable arguments to reinstall the
4261directories you want in the source path. You can add all the
4262directories in one command.
4263@end enumerate
4264
6d2ebf8b 4265@node Machine Code
c906108c
SS
4266@section Source and machine code
4267
4268You can use the command @code{info line} to map source lines to program
4269addresses (and vice versa), and the command @code{disassemble} to display
4270a range of addresses as machine instructions. When run under @sc{gnu} Emacs
d4f3574e 4271mode, the @code{info line} command causes the arrow to point to the
5d161b24 4272line specified. Also, @code{info line} prints addresses in symbolic form as
c906108c
SS
4273well as hex.
4274
4275@table @code
4276@kindex info line
4277@item info line @var{linespec}
4278Print the starting and ending addresses of the compiled code for
4279source line @var{linespec}. You can specify source lines in any of
4280the ways understood by the @code{list} command (@pxref{List, ,Printing
4281source lines}).
4282@end table
4283
4284For example, we can use @code{info line} to discover the location of
4285the object code for the first line of function
4286@code{m4_changequote}:
4287
d4f3574e
SS
4288@c FIXME: I think this example should also show the addresses in
4289@c symbolic form, as they usually would be displayed.
c906108c 4290@smallexample
96a2c332 4291(@value{GDBP}) info line m4_changequote
c906108c
SS
4292Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4293@end smallexample
4294
4295@noindent
4296We can also inquire (using @code{*@var{addr}} as the form for
4297@var{linespec}) what source line covers a particular address:
4298@smallexample
4299(@value{GDBP}) info line *0x63ff
4300Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4301@end smallexample
4302
4303@cindex @code{$_} and @code{info line}
41afff9a 4304@kindex x@r{(examine), and} info line
c906108c
SS
4305After @code{info line}, the default address for the @code{x} command
4306is changed to the starting address of the line, so that @samp{x/i} is
4307sufficient to begin examining the machine code (@pxref{Memory,
4308,Examining memory}). Also, this address is saved as the value of the
4309convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4310variables}).
4311
4312@table @code
4313@kindex disassemble
4314@cindex assembly instructions
4315@cindex instructions, assembly
4316@cindex machine instructions
4317@cindex listing machine instructions
4318@item disassemble
4319This specialized command dumps a range of memory as machine
4320instructions. The default memory range is the function surrounding the
4321program counter of the selected frame. A single argument to this
4322command is a program counter value; @value{GDBN} dumps the function
4323surrounding this value. Two arguments specify a range of addresses
4324(first inclusive, second exclusive) to dump.
4325@end table
4326
c906108c
SS
4327The following example shows the disassembly of a range of addresses of
4328HP PA-RISC 2.0 code:
4329
4330@smallexample
4331(@value{GDBP}) disas 0x32c4 0x32e4
4332Dump of assembler code from 0x32c4 to 0x32e4:
43330x32c4 <main+204>: addil 0,dp
43340x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
43350x32cc <main+212>: ldil 0x3000,r31
43360x32d0 <main+216>: ble 0x3f8(sr4,r31)
43370x32d4 <main+220>: ldo 0(r31),rp
43380x32d8 <main+224>: addil -0x800,dp
43390x32dc <main+228>: ldo 0x588(r1),r26
43400x32e0 <main+232>: ldil 0x3000,r31
4341End of assembler dump.
4342@end smallexample
c906108c
SS
4343
4344Some architectures have more than one commonly-used set of instruction
4345mnemonics or other syntax.
4346
4347@table @code
d4f3574e 4348@kindex set disassembly-flavor
c906108c
SS
4349@cindex assembly instructions
4350@cindex instructions, assembly
4351@cindex machine instructions
4352@cindex listing machine instructions
d4f3574e
SS
4353@cindex Intel disassembly flavor
4354@cindex AT&T disassembly flavor
4355@item set disassembly-flavor @var{instruction-set}
c906108c
SS
4356Select the instruction set to use when disassembling the
4357program via the @code{disassemble} or @code{x/i} commands.
4358
4359Currently this command is only defined for the Intel x86 family. You
d4f3574e
SS
4360can set @var{instruction-set} to either @code{intel} or @code{att}.
4361The default is @code{att}, the AT&T flavor used by default by Unix
4362assemblers for x86-based targets.
c906108c
SS
4363@end table
4364
4365
6d2ebf8b 4366@node Data
c906108c
SS
4367@chapter Examining Data
4368
4369@cindex printing data
4370@cindex examining data
4371@kindex print
4372@kindex inspect
4373@c "inspect" is not quite a synonym if you are using Epoch, which we do not
4374@c document because it is nonstandard... Under Epoch it displays in a
4375@c different window or something like that.
4376The usual way to examine data in your program is with the @code{print}
7a292a7a
SS
4377command (abbreviated @code{p}), or its synonym @code{inspect}. It
4378evaluates and prints the value of an expression of the language your
4379program is written in (@pxref{Languages, ,Using @value{GDBN} with
4380Different Languages}).
c906108c
SS
4381
4382@table @code
d4f3574e
SS
4383@item print @var{expr}
4384@itemx print /@var{f} @var{expr}
4385@var{expr} is an expression (in the source language). By default the
4386value of @var{expr} is printed in a format appropriate to its data type;
c906108c 4387you can choose a different format by specifying @samp{/@var{f}}, where
d4f3574e 4388@var{f} is a letter specifying the format; see @ref{Output Formats,,Output
c906108c
SS
4389formats}.
4390
4391@item print
4392@itemx print /@var{f}
d4f3574e 4393If you omit @var{expr}, @value{GDBN} displays the last value again (from the
c906108c
SS
4394@dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4395conveniently inspect the same value in an alternative format.
4396@end table
4397
4398A more low-level way of examining data is with the @code{x} command.
4399It examines data in memory at a specified address and prints it in a
4400specified format. @xref{Memory, ,Examining memory}.
4401
7a292a7a 4402If you are interested in information about types, or about how the
d4f3574e
SS
4403fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4404command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7a292a7a 4405Table}.
c906108c
SS
4406
4407@menu
4408* Expressions:: Expressions
4409* Variables:: Program variables
4410* Arrays:: Artificial arrays
4411* Output Formats:: Output formats
4412* Memory:: Examining memory
4413* Auto Display:: Automatic display
4414* Print Settings:: Print settings
4415* Value History:: Value history
4416* Convenience Vars:: Convenience variables
4417* Registers:: Registers
c906108c 4418* Floating Point Hardware:: Floating point hardware
29e57380 4419* Memory Region Attributes:: Memory region attributes
16d9dec6 4420* Dump/Restore Files:: Copy between memory and a file
c906108c
SS
4421@end menu
4422
6d2ebf8b 4423@node Expressions
c906108c
SS
4424@section Expressions
4425
4426@cindex expressions
4427@code{print} and many other @value{GDBN} commands accept an expression and
4428compute its value. Any kind of constant, variable or operator defined
4429by the programming language you are using is valid in an expression in
e2e0bcd1
JB
4430@value{GDBN}. This includes conditional expressions, function calls,
4431casts, and string constants. It also includes preprocessor macros, if
4432you compiled your program to include this information; see
4433@ref{Compilation}.
c906108c 4434
d4f3574e
SS
4435@value{GDBN} supports array constants in expressions input by
4436the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5d161b24 4437you can use the command @code{print @{1, 2, 3@}} to build up an array in
d4f3574e 4438memory that is @code{malloc}ed in the target program.
c906108c 4439
c906108c
SS
4440Because C is so widespread, most of the expressions shown in examples in
4441this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4442Languages}, for information on how to use expressions in other
4443languages.
4444
4445In this section, we discuss operators that you can use in @value{GDBN}
4446expressions regardless of your programming language.
4447
4448Casts are supported in all languages, not just in C, because it is so
4449useful to cast a number into a pointer in order to examine a structure
4450at that address in memory.
4451@c FIXME: casts supported---Mod2 true?
c906108c
SS
4452
4453@value{GDBN} supports these operators, in addition to those common
4454to programming languages:
4455
4456@table @code
4457@item @@
4458@samp{@@} is a binary operator for treating parts of memory as arrays.
4459@xref{Arrays, ,Artificial arrays}, for more information.
4460
4461@item ::
4462@samp{::} allows you to specify a variable in terms of the file or
4463function where it is defined. @xref{Variables, ,Program variables}.
4464
4465@cindex @{@var{type}@}
4466@cindex type casting memory
4467@cindex memory, viewing as typed object
4468@cindex casts, to view memory
4469@item @{@var{type}@} @var{addr}
4470Refers to an object of type @var{type} stored at address @var{addr} in
4471memory. @var{addr} may be any expression whose value is an integer or
4472pointer (but parentheses are required around binary operators, just as in
4473a cast). This construct is allowed regardless of what kind of data is
4474normally supposed to reside at @var{addr}.
4475@end table
4476
6d2ebf8b 4477@node Variables
c906108c
SS
4478@section Program variables
4479
4480The most common kind of expression to use is the name of a variable
4481in your program.
4482
4483Variables in expressions are understood in the selected stack frame
4484(@pxref{Selection, ,Selecting a frame}); they must be either:
4485
4486@itemize @bullet
4487@item
4488global (or file-static)
4489@end itemize
4490
5d161b24 4491@noindent or
c906108c
SS
4492
4493@itemize @bullet
4494@item
4495visible according to the scope rules of the
4496programming language from the point of execution in that frame
5d161b24 4497@end itemize
c906108c
SS
4498
4499@noindent This means that in the function
4500
474c8240 4501@smallexample
c906108c
SS
4502foo (a)
4503 int a;
4504@{
4505 bar (a);
4506 @{
4507 int b = test ();
4508 bar (b);
4509 @}
4510@}
474c8240 4511@end smallexample
c906108c
SS
4512
4513@noindent
4514you can examine and use the variable @code{a} whenever your program is
4515executing within the function @code{foo}, but you can only use or
4516examine the variable @code{b} while your program is executing inside
4517the block where @code{b} is declared.
4518
4519@cindex variable name conflict
4520There is an exception: you can refer to a variable or function whose
4521scope is a single source file even if the current execution point is not
4522in this file. But it is possible to have more than one such variable or
4523function with the same name (in different source files). If that
4524happens, referring to that name has unpredictable effects. If you wish,
4525you can specify a static variable in a particular function or file,
4526using the colon-colon notation:
4527
d4f3574e 4528@cindex colon-colon, context for variables/functions
c906108c
SS
4529@iftex
4530@c info cannot cope with a :: index entry, but why deprive hard copy readers?
41afff9a 4531@cindex @code{::}, context for variables/functions
c906108c 4532@end iftex
474c8240 4533@smallexample
c906108c
SS
4534@var{file}::@var{variable}
4535@var{function}::@var{variable}
474c8240 4536@end smallexample
c906108c
SS
4537
4538@noindent
4539Here @var{file} or @var{function} is the name of the context for the
4540static @var{variable}. In the case of file names, you can use quotes to
4541make sure @value{GDBN} parses the file name as a single word---for example,
4542to print a global value of @code{x} defined in @file{f2.c}:
4543
474c8240 4544@smallexample
c906108c 4545(@value{GDBP}) p 'f2.c'::x
474c8240 4546@end smallexample
c906108c 4547
b37052ae 4548@cindex C@t{++} scope resolution
c906108c 4549This use of @samp{::} is very rarely in conflict with the very similar
b37052ae 4550use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
c906108c
SS
4551scope resolution operator in @value{GDBN} expressions.
4552@c FIXME: Um, so what happens in one of those rare cases where it's in
4553@c conflict?? --mew
c906108c
SS
4554
4555@cindex wrong values
4556@cindex variable values, wrong
4557@quotation
4558@emph{Warning:} Occasionally, a local variable may appear to have the
4559wrong value at certain points in a function---just after entry to a new
4560scope, and just before exit.
4561@end quotation
4562You may see this problem when you are stepping by machine instructions.
4563This is because, on most machines, it takes more than one instruction to
4564set up a stack frame (including local variable definitions); if you are
4565stepping by machine instructions, variables may appear to have the wrong
4566values until the stack frame is completely built. On exit, it usually
4567also takes more than one machine instruction to destroy a stack frame;
4568after you begin stepping through that group of instructions, local
4569variable definitions may be gone.
4570
4571This may also happen when the compiler does significant optimizations.
4572To be sure of always seeing accurate values, turn off all optimization
4573when compiling.
4574
d4f3574e
SS
4575@cindex ``No symbol "foo" in current context''
4576Another possible effect of compiler optimizations is to optimize
4577unused variables out of existence, or assign variables to registers (as
4578opposed to memory addresses). Depending on the support for such cases
4579offered by the debug info format used by the compiler, @value{GDBN}
4580might not be able to display values for such local variables. If that
4581happens, @value{GDBN} will print a message like this:
4582
474c8240 4583@smallexample
d4f3574e 4584No symbol "foo" in current context.
474c8240 4585@end smallexample
d4f3574e
SS
4586
4587To solve such problems, either recompile without optimizations, or use a
4588different debug info format, if the compiler supports several such
b37052ae 4589formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler usually
d4f3574e
SS
4590supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info
4591in a format that is superior to formats such as COFF. You may be able
96c405b3 4592to use DWARF2 (@samp{-gdwarf-2}), which is also an effective form for
d4f3574e
SS
4593debug info. See @ref{Debugging Options,,Options for Debugging Your
4594Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more
4595information.
4596
4597
6d2ebf8b 4598@node Arrays
c906108c
SS
4599@section Artificial arrays
4600
4601@cindex artificial array
41afff9a 4602@kindex @@@r{, referencing memory as an array}
c906108c
SS
4603It is often useful to print out several successive objects of the
4604same type in memory; a section of an array, or an array of
4605dynamically determined size for which only a pointer exists in the
4606program.
4607
4608You can do this by referring to a contiguous span of memory as an
4609@dfn{artificial array}, using the binary operator @samp{@@}. The left
4610operand of @samp{@@} should be the first element of the desired array
4611and be an individual object. The right operand should be the desired length
4612of the array. The result is an array value whose elements are all of
4613the type of the left argument. The first element is actually the left
4614argument; the second element comes from bytes of memory immediately
4615following those that hold the first element, and so on. Here is an
4616example. If a program says
4617
474c8240 4618@smallexample
c906108c 4619int *array = (int *) malloc (len * sizeof (int));
474c8240 4620@end smallexample
c906108c
SS
4621
4622@noindent
4623you can print the contents of @code{array} with
4624
474c8240 4625@smallexample
c906108c 4626p *array@@len
474c8240 4627@end smallexample
c906108c
SS
4628
4629The left operand of @samp{@@} must reside in memory. Array values made
4630with @samp{@@} in this way behave just like other arrays in terms of
4631subscripting, and are coerced to pointers when used in expressions.
4632Artificial arrays most often appear in expressions via the value history
4633(@pxref{Value History, ,Value history}), after printing one out.
4634
4635Another way to create an artificial array is to use a cast.
4636This re-interprets a value as if it were an array.
4637The value need not be in memory:
474c8240 4638@smallexample
c906108c
SS
4639(@value{GDBP}) p/x (short[2])0x12345678
4640$1 = @{0x1234, 0x5678@}
474c8240 4641@end smallexample
c906108c
SS
4642
4643As a convenience, if you leave the array length out (as in
c3f6f71d 4644@samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
c906108c 4645the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
474c8240 4646@smallexample
c906108c
SS
4647(@value{GDBP}) p/x (short[])0x12345678
4648$2 = @{0x1234, 0x5678@}
474c8240 4649@end smallexample
c906108c
SS
4650
4651Sometimes the artificial array mechanism is not quite enough; in
4652moderately complex data structures, the elements of interest may not
4653actually be adjacent---for example, if you are interested in the values
4654of pointers in an array. One useful work-around in this situation is
4655to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4656variables}) as a counter in an expression that prints the first
4657interesting value, and then repeat that expression via @key{RET}. For
4658instance, suppose you have an array @code{dtab} of pointers to
4659structures, and you are interested in the values of a field @code{fv}
4660in each structure. Here is an example of what you might type:
4661
474c8240 4662@smallexample
c906108c
SS
4663set $i = 0
4664p dtab[$i++]->fv
4665@key{RET}
4666@key{RET}
4667@dots{}
474c8240 4668@end smallexample
c906108c 4669
6d2ebf8b 4670@node Output Formats
c906108c
SS
4671@section Output formats
4672
4673@cindex formatted output
4674@cindex output formats
4675By default, @value{GDBN} prints a value according to its data type. Sometimes
4676this is not what you want. For example, you might want to print a number
4677in hex, or a pointer in decimal. Or you might want to view data in memory
4678at a certain address as a character string or as an instruction. To do
4679these things, specify an @dfn{output format} when you print a value.
4680
4681The simplest use of output formats is to say how to print a value
4682already computed. This is done by starting the arguments of the
4683@code{print} command with a slash and a format letter. The format
4684letters supported are:
4685
4686@table @code
4687@item x
4688Regard the bits of the value as an integer, and print the integer in
4689hexadecimal.
4690
4691@item d
4692Print as integer in signed decimal.
4693
4694@item u
4695Print as integer in unsigned decimal.
4696
4697@item o
4698Print as integer in octal.
4699
4700@item t
4701Print as integer in binary. The letter @samp{t} stands for ``two''.
4702@footnote{@samp{b} cannot be used because these format letters are also
4703used with the @code{x} command, where @samp{b} stands for ``byte'';
d4f3574e 4704see @ref{Memory,,Examining memory}.}
c906108c
SS
4705
4706@item a
4707@cindex unknown address, locating
3d67e040 4708@cindex locate address
c906108c
SS
4709Print as an address, both absolute in hexadecimal and as an offset from
4710the nearest preceding symbol. You can use this format used to discover
4711where (in what function) an unknown address is located:
4712
474c8240 4713@smallexample
c906108c
SS
4714(@value{GDBP}) p/a 0x54320
4715$3 = 0x54320 <_initialize_vx+396>
474c8240 4716@end smallexample
c906108c 4717
3d67e040
EZ
4718@noindent
4719The command @code{info symbol 0x54320} yields similar results.
4720@xref{Symbols, info symbol}.
4721
c906108c
SS
4722@item c
4723Regard as an integer and print it as a character constant.
4724
4725@item f
4726Regard the bits of the value as a floating point number and print
4727using typical floating point syntax.
4728@end table
4729
4730For example, to print the program counter in hex (@pxref{Registers}), type
4731
474c8240 4732@smallexample
c906108c 4733p/x $pc
474c8240 4734@end smallexample
c906108c
SS
4735
4736@noindent
4737Note that no space is required before the slash; this is because command
4738names in @value{GDBN} cannot contain a slash.
4739
4740To reprint the last value in the value history with a different format,
4741you can use the @code{print} command with just a format and no
4742expression. For example, @samp{p/x} reprints the last value in hex.
4743
6d2ebf8b 4744@node Memory
c906108c
SS
4745@section Examining memory
4746
4747You can use the command @code{x} (for ``examine'') to examine memory in
4748any of several formats, independently of your program's data types.
4749
4750@cindex examining memory
4751@table @code
41afff9a 4752@kindex x @r{(examine memory)}
c906108c
SS
4753@item x/@var{nfu} @var{addr}
4754@itemx x @var{addr}
4755@itemx x
4756Use the @code{x} command to examine memory.
4757@end table
4758
4759@var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4760much memory to display and how to format it; @var{addr} is an
4761expression giving the address where you want to start displaying memory.
4762If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4763Several commands set convenient defaults for @var{addr}.
4764
4765@table @r
4766@item @var{n}, the repeat count
4767The repeat count is a decimal integer; the default is 1. It specifies
4768how much memory (counting by units @var{u}) to display.
4769@c This really is **decimal**; unaffected by 'set radix' as of GDB
4770@c 4.1.2.
4771
4772@item @var{f}, the display format
4773The display format is one of the formats used by @code{print},
4774@samp{s} (null-terminated string), or @samp{i} (machine instruction).
4775The default is @samp{x} (hexadecimal) initially.
4776The default changes each time you use either @code{x} or @code{print}.
4777
4778@item @var{u}, the unit size
4779The unit size is any of
4780
4781@table @code
4782@item b
4783Bytes.
4784@item h
4785Halfwords (two bytes).
4786@item w
4787Words (four bytes). This is the initial default.
4788@item g
4789Giant words (eight bytes).
4790@end table
4791
4792Each time you specify a unit size with @code{x}, that size becomes the
4793default unit the next time you use @code{x}. (For the @samp{s} and
4794@samp{i} formats, the unit size is ignored and is normally not written.)
4795
4796@item @var{addr}, starting display address
4797@var{addr} is the address where you want @value{GDBN} to begin displaying
4798memory. The expression need not have a pointer value (though it may);
4799it is always interpreted as an integer address of a byte of memory.
4800@xref{Expressions, ,Expressions}, for more information on expressions. The default for
4801@var{addr} is usually just after the last address examined---but several
4802other commands also set the default address: @code{info breakpoints} (to
4803the address of the last breakpoint listed), @code{info line} (to the
4804starting address of a line), and @code{print} (if you use it to display
4805a value from memory).
4806@end table
4807
4808For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4809(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4810starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4811words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
d4f3574e 4812@pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
c906108c
SS
4813
4814Since the letters indicating unit sizes are all distinct from the
4815letters specifying output formats, you do not have to remember whether
4816unit size or format comes first; either order works. The output
4817specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4818(However, the count @var{n} must come first; @samp{wx4} does not work.)
4819
4820Even though the unit size @var{u} is ignored for the formats @samp{s}
4821and @samp{i}, you might still want to use a count @var{n}; for example,
4822@samp{3i} specifies that you want to see three machine instructions,
4823including any operands. The command @code{disassemble} gives an
d4f3574e 4824alternative way of inspecting machine instructions; see @ref{Machine
c906108c
SS
4825Code,,Source and machine code}.
4826
4827All the defaults for the arguments to @code{x} are designed to make it
4828easy to continue scanning memory with minimal specifications each time
4829you use @code{x}. For example, after you have inspected three machine
4830instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4831with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4832the repeat count @var{n} is used again; the other arguments default as
4833for successive uses of @code{x}.
4834
4835@cindex @code{$_}, @code{$__}, and value history
4836The addresses and contents printed by the @code{x} command are not saved
4837in the value history because there is often too much of them and they
4838would get in the way. Instead, @value{GDBN} makes these values available for
4839subsequent use in expressions as values of the convenience variables
4840@code{$_} and @code{$__}. After an @code{x} command, the last address
4841examined is available for use in expressions in the convenience variable
4842@code{$_}. The contents of that address, as examined, are available in
4843the convenience variable @code{$__}.
4844
4845If the @code{x} command has a repeat count, the address and contents saved
4846are from the last memory unit printed; this is not the same as the last
4847address printed if several units were printed on the last line of output.
4848
6d2ebf8b 4849@node Auto Display
c906108c
SS
4850@section Automatic display
4851@cindex automatic display
4852@cindex display of expressions
4853
4854If you find that you want to print the value of an expression frequently
4855(to see how it changes), you might want to add it to the @dfn{automatic
4856display list} so that @value{GDBN} prints its value each time your program stops.
4857Each expression added to the list is given a number to identify it;
4858to remove an expression from the list, you specify that number.
4859The automatic display looks like this:
4860
474c8240 4861@smallexample
c906108c
SS
48622: foo = 38
48633: bar[5] = (struct hack *) 0x3804
474c8240 4864@end smallexample
c906108c
SS
4865
4866@noindent
4867This display shows item numbers, expressions and their current values. As with
4868displays you request manually using @code{x} or @code{print}, you can
4869specify the output format you prefer; in fact, @code{display} decides
4870whether to use @code{print} or @code{x} depending on how elaborate your
4871format specification is---it uses @code{x} if you specify a unit size,
4872or one of the two formats (@samp{i} and @samp{s}) that are only
4873supported by @code{x}; otherwise it uses @code{print}.
4874
4875@table @code
4876@kindex display
d4f3574e
SS
4877@item display @var{expr}
4878Add the expression @var{expr} to the list of expressions to display
c906108c
SS
4879each time your program stops. @xref{Expressions, ,Expressions}.
4880
4881@code{display} does not repeat if you press @key{RET} again after using it.
4882
d4f3574e 4883@item display/@var{fmt} @var{expr}
c906108c 4884For @var{fmt} specifying only a display format and not a size or
d4f3574e 4885count, add the expression @var{expr} to the auto-display list but
c906108c
SS
4886arrange to display it each time in the specified format @var{fmt}.
4887@xref{Output Formats,,Output formats}.
4888
4889@item display/@var{fmt} @var{addr}
4890For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
4891number of units, add the expression @var{addr} as a memory address to
4892be examined each time your program stops. Examining means in effect
4893doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
4894@end table
4895
4896For example, @samp{display/i $pc} can be helpful, to see the machine
4897instruction about to be executed each time execution stops (@samp{$pc}
d4f3574e 4898is a common name for the program counter; @pxref{Registers, ,Registers}).
c906108c
SS
4899
4900@table @code
4901@kindex delete display
4902@kindex undisplay
4903@item undisplay @var{dnums}@dots{}
4904@itemx delete display @var{dnums}@dots{}
4905Remove item numbers @var{dnums} from the list of expressions to display.
4906
4907@code{undisplay} does not repeat if you press @key{RET} after using it.
4908(Otherwise you would just get the error @samp{No display number @dots{}}.)
4909
4910@kindex disable display
4911@item disable display @var{dnums}@dots{}
4912Disable the display of item numbers @var{dnums}. A disabled display
4913item is not printed automatically, but is not forgotten. It may be
4914enabled again later.
4915
4916@kindex enable display
4917@item enable display @var{dnums}@dots{}
4918Enable display of item numbers @var{dnums}. It becomes effective once
4919again in auto display of its expression, until you specify otherwise.
4920
4921@item display
4922Display the current values of the expressions on the list, just as is
4923done when your program stops.
4924
4925@kindex info display
4926@item info display
4927Print the list of expressions previously set up to display
4928automatically, each one with its item number, but without showing the
4929values. This includes disabled expressions, which are marked as such.
4930It also includes expressions which would not be displayed right now
4931because they refer to automatic variables not currently available.
4932@end table
4933
4934If a display expression refers to local variables, then it does not make
4935sense outside the lexical context for which it was set up. Such an
4936expression is disabled when execution enters a context where one of its
4937variables is not defined. For example, if you give the command
4938@code{display last_char} while inside a function with an argument
4939@code{last_char}, @value{GDBN} displays this argument while your program
4940continues to stop inside that function. When it stops elsewhere---where
4941there is no variable @code{last_char}---the display is disabled
4942automatically. The next time your program stops where @code{last_char}
4943is meaningful, you can enable the display expression once again.
4944
6d2ebf8b 4945@node Print Settings
c906108c
SS
4946@section Print settings
4947
4948@cindex format options
4949@cindex print settings
4950@value{GDBN} provides the following ways to control how arrays, structures,
4951and symbols are printed.
4952
4953@noindent
4954These settings are useful for debugging programs in any language:
4955
4956@table @code
4957@kindex set print address
4958@item set print address
4959@itemx set print address on
4960@value{GDBN} prints memory addresses showing the location of stack
4961traces, structure values, pointer values, breakpoints, and so forth,
4962even when it also displays the contents of those addresses. The default
4963is @code{on}. For example, this is what a stack frame display looks like with
4964@code{set print address on}:
4965
4966@smallexample
4967@group
4968(@value{GDBP}) f
4969#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
4970 at input.c:530
4971530 if (lquote != def_lquote)
4972@end group
4973@end smallexample
4974
4975@item set print address off
4976Do not print addresses when displaying their contents. For example,
4977this is the same stack frame displayed with @code{set print address off}:
4978
4979@smallexample
4980@group
4981(@value{GDBP}) set print addr off
4982(@value{GDBP}) f
4983#0 set_quotes (lq="<<", rq=">>") at input.c:530
4984530 if (lquote != def_lquote)
4985@end group
4986@end smallexample
4987
4988You can use @samp{set print address off} to eliminate all machine
4989dependent displays from the @value{GDBN} interface. For example, with
4990@code{print address off}, you should get the same text for backtraces on
4991all machines---whether or not they involve pointer arguments.
4992
4993@kindex show print address
4994@item show print address
4995Show whether or not addresses are to be printed.
4996@end table
4997
4998When @value{GDBN} prints a symbolic address, it normally prints the
4999closest earlier symbol plus an offset. If that symbol does not uniquely
5000identify the address (for example, it is a name whose scope is a single
5001source file), you may need to clarify. One way to do this is with
5002@code{info line}, for example @samp{info line *0x4537}. Alternately,
5003you can set @value{GDBN} to print the source file and line number when
5004it prints a symbolic address:
5005
5006@table @code
5007@kindex set print symbol-filename
5008@item set print symbol-filename on
5009Tell @value{GDBN} to print the source file name and line number of a
5010symbol in the symbolic form of an address.
5011
5012@item set print symbol-filename off
5013Do not print source file name and line number of a symbol. This is the
5014default.
5015
5016@kindex show print symbol-filename
5017@item show print symbol-filename
5018Show whether or not @value{GDBN} will print the source file name and
5019line number of a symbol in the symbolic form of an address.
5020@end table
5021
5022Another situation where it is helpful to show symbol filenames and line
5023numbers is when disassembling code; @value{GDBN} shows you the line
5024number and source file that corresponds to each instruction.
5025
5026Also, you may wish to see the symbolic form only if the address being
5027printed is reasonably close to the closest earlier symbol:
5028
5029@table @code
5030@kindex set print max-symbolic-offset
5031@item set print max-symbolic-offset @var{max-offset}
5032Tell @value{GDBN} to only display the symbolic form of an address if the
5033offset between the closest earlier symbol and the address is less than
5d161b24 5034@var{max-offset}. The default is 0, which tells @value{GDBN}
c906108c
SS
5035to always print the symbolic form of an address if any symbol precedes it.
5036
5037@kindex show print max-symbolic-offset
5038@item show print max-symbolic-offset
5039Ask how large the maximum offset is that @value{GDBN} prints in a
5040symbolic address.
5041@end table
5042
5043@cindex wild pointer, interpreting
5044@cindex pointer, finding referent
5045If you have a pointer and you are not sure where it points, try
5046@samp{set print symbol-filename on}. Then you can determine the name
5047and source file location of the variable where it points, using
5048@samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5049For example, here @value{GDBN} shows that a variable @code{ptt} points
5050at another variable @code{t}, defined in @file{hi2.c}:
5051
474c8240 5052@smallexample
c906108c
SS
5053(@value{GDBP}) set print symbol-filename on
5054(@value{GDBP}) p/a ptt
5055$4 = 0xe008 <t in hi2.c>
474c8240 5056@end smallexample
c906108c
SS
5057
5058@quotation
5059@emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5060does not show the symbol name and filename of the referent, even with
5061the appropriate @code{set print} options turned on.
5062@end quotation
5063
5064Other settings control how different kinds of objects are printed:
5065
5066@table @code
5067@kindex set print array
5068@item set print array
5069@itemx set print array on
5070Pretty print arrays. This format is more convenient to read,
5071but uses more space. The default is off.
5072
5073@item set print array off
5074Return to compressed format for arrays.
5075
5076@kindex show print array
5077@item show print array
5078Show whether compressed or pretty format is selected for displaying
5079arrays.
5080
5081@kindex set print elements
5082@item set print elements @var{number-of-elements}
5083Set a limit on how many elements of an array @value{GDBN} will print.
5084If @value{GDBN} is printing a large array, it stops printing after it has
5085printed the number of elements set by the @code{set print elements} command.
5086This limit also applies to the display of strings.
d4f3574e 5087When @value{GDBN} starts, this limit is set to 200.
c906108c
SS
5088Setting @var{number-of-elements} to zero means that the printing is unlimited.
5089
5090@kindex show print elements
5091@item show print elements
5092Display the number of elements of a large array that @value{GDBN} will print.
5093If the number is 0, then the printing is unlimited.
5094
5095@kindex set print null-stop
5096@item set print null-stop
5097Cause @value{GDBN} to stop printing the characters of an array when the first
d4f3574e 5098@sc{null} is encountered. This is useful when large arrays actually
c906108c 5099contain only short strings.
d4f3574e 5100The default is off.
c906108c
SS
5101
5102@kindex set print pretty
5103@item set print pretty on
5d161b24 5104Cause @value{GDBN} to print structures in an indented format with one member
c906108c
SS
5105per line, like this:
5106
5107@smallexample
5108@group
5109$1 = @{
5110 next = 0x0,
5111 flags = @{
5112 sweet = 1,
5113 sour = 1
5114 @},
5115 meat = 0x54 "Pork"
5116@}
5117@end group
5118@end smallexample
5119
5120@item set print pretty off
5121Cause @value{GDBN} to print structures in a compact format, like this:
5122
5123@smallexample
5124@group
5125$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5126meat = 0x54 "Pork"@}
5127@end group
5128@end smallexample
5129
5130@noindent
5131This is the default format.
5132
5133@kindex show print pretty
5134@item show print pretty
5135Show which format @value{GDBN} is using to print structures.
5136
5137@kindex set print sevenbit-strings
5138@item set print sevenbit-strings on
5139Print using only seven-bit characters; if this option is set,
5140@value{GDBN} displays any eight-bit characters (in strings or
5141character values) using the notation @code{\}@var{nnn}. This setting is
5142best if you are working in English (@sc{ascii}) and you use the
5143high-order bit of characters as a marker or ``meta'' bit.
5144
5145@item set print sevenbit-strings off
5146Print full eight-bit characters. This allows the use of more
5147international character sets, and is the default.
5148
5149@kindex show print sevenbit-strings
5150@item show print sevenbit-strings
5151Show whether or not @value{GDBN} is printing only seven-bit characters.
5152
5153@kindex set print union
5154@item set print union on
5d161b24 5155Tell @value{GDBN} to print unions which are contained in structures. This
c906108c
SS
5156is the default setting.
5157
5158@item set print union off
5159Tell @value{GDBN} not to print unions which are contained in structures.
5160
5161@kindex show print union
5162@item show print union
5163Ask @value{GDBN} whether or not it will print unions which are contained in
5164structures.
5165
5166For example, given the declarations
5167
5168@smallexample
5169typedef enum @{Tree, Bug@} Species;
5170typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5d161b24 5171typedef enum @{Caterpillar, Cocoon, Butterfly@}
c906108c
SS
5172 Bug_forms;
5173
5174struct thing @{
5175 Species it;
5176 union @{
5177 Tree_forms tree;
5178 Bug_forms bug;
5179 @} form;
5180@};
5181
5182struct thing foo = @{Tree, @{Acorn@}@};
5183@end smallexample
5184
5185@noindent
5186with @code{set print union on} in effect @samp{p foo} would print
5187
5188@smallexample
5189$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5190@end smallexample
5191
5192@noindent
5193and with @code{set print union off} in effect it would print
5194
5195@smallexample
5196$1 = @{it = Tree, form = @{...@}@}
5197@end smallexample
5198@end table
5199
c906108c
SS
5200@need 1000
5201@noindent
b37052ae 5202These settings are of interest when debugging C@t{++} programs:
c906108c
SS
5203
5204@table @code
5205@cindex demangling
5206@kindex set print demangle
5207@item set print demangle
5208@itemx set print demangle on
b37052ae 5209Print C@t{++} names in their source form rather than in the encoded
c906108c 5210(``mangled'') form passed to the assembler and linker for type-safe
d4f3574e 5211linkage. The default is on.
c906108c
SS
5212
5213@kindex show print demangle
5214@item show print demangle
b37052ae 5215Show whether C@t{++} names are printed in mangled or demangled form.
c906108c
SS
5216
5217@kindex set print asm-demangle
5218@item set print asm-demangle
5219@itemx set print asm-demangle on
b37052ae 5220Print C@t{++} names in their source form rather than their mangled form, even
c906108c
SS
5221in assembler code printouts such as instruction disassemblies.
5222The default is off.
5223
5224@kindex show print asm-demangle
5225@item show print asm-demangle
b37052ae 5226Show whether C@t{++} names in assembly listings are printed in mangled
c906108c
SS
5227or demangled form.
5228
5229@kindex set demangle-style
b37052ae
EZ
5230@cindex C@t{++} symbol decoding style
5231@cindex symbol decoding style, C@t{++}
c906108c
SS
5232@item set demangle-style @var{style}
5233Choose among several encoding schemes used by different compilers to
b37052ae 5234represent C@t{++} names. The choices for @var{style} are currently:
c906108c
SS
5235
5236@table @code
5237@item auto
5238Allow @value{GDBN} to choose a decoding style by inspecting your program.
5239
5240@item gnu
b37052ae 5241Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
c906108c 5242This is the default.
c906108c
SS
5243
5244@item hp
b37052ae 5245Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
c906108c
SS
5246
5247@item lucid
b37052ae 5248Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
c906108c
SS
5249
5250@item arm
b37052ae 5251Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
c906108c
SS
5252@strong{Warning:} this setting alone is not sufficient to allow
5253debugging @code{cfront}-generated executables. @value{GDBN} would
5254require further enhancement to permit that.
5255
5256@end table
5257If you omit @var{style}, you will see a list of possible formats.
5258
5259@kindex show demangle-style
5260@item show demangle-style
b37052ae 5261Display the encoding style currently in use for decoding C@t{++} symbols.
c906108c
SS
5262
5263@kindex set print object
5264@item set print object
5265@itemx set print object on
5266When displaying a pointer to an object, identify the @emph{actual}
5267(derived) type of the object rather than the @emph{declared} type, using
5268the virtual function table.
5269
5270@item set print object off
5271Display only the declared type of objects, without reference to the
5272virtual function table. This is the default setting.
5273
5274@kindex show print object
5275@item show print object
5276Show whether actual, or declared, object types are displayed.
5277
5278@kindex set print static-members
5279@item set print static-members
5280@itemx set print static-members on
b37052ae 5281Print static members when displaying a C@t{++} object. The default is on.
c906108c
SS
5282
5283@item set print static-members off
b37052ae 5284Do not print static members when displaying a C@t{++} object.
c906108c
SS
5285
5286@kindex show print static-members
5287@item show print static-members
b37052ae 5288Show whether C@t{++} static members are printed, or not.
c906108c
SS
5289
5290@c These don't work with HP ANSI C++ yet.
5291@kindex set print vtbl
5292@item set print vtbl
5293@itemx set print vtbl on
b37052ae 5294Pretty print C@t{++} virtual function tables. The default is off.
c906108c 5295(The @code{vtbl} commands do not work on programs compiled with the HP
b37052ae 5296ANSI C@t{++} compiler (@code{aCC}).)
c906108c
SS
5297
5298@item set print vtbl off
b37052ae 5299Do not pretty print C@t{++} virtual function tables.
c906108c
SS
5300
5301@kindex show print vtbl
5302@item show print vtbl
b37052ae 5303Show whether C@t{++} virtual function tables are pretty printed, or not.
c906108c 5304@end table
c906108c 5305
6d2ebf8b 5306@node Value History
c906108c
SS
5307@section Value history
5308
5309@cindex value history
5d161b24
DB
5310Values printed by the @code{print} command are saved in the @value{GDBN}
5311@dfn{value history}. This allows you to refer to them in other expressions.
5312Values are kept until the symbol table is re-read or discarded
5313(for example with the @code{file} or @code{symbol-file} commands).
5314When the symbol table changes, the value history is discarded,
5315since the values may contain pointers back to the types defined in the
c906108c
SS
5316symbol table.
5317
5318@cindex @code{$}
5319@cindex @code{$$}
5320@cindex history number
5321The values printed are given @dfn{history numbers} by which you can
5322refer to them. These are successive integers starting with one.
5323@code{print} shows you the history number assigned to a value by
5324printing @samp{$@var{num} = } before the value; here @var{num} is the
5325history number.
5326
5327To refer to any previous value, use @samp{$} followed by the value's
5328history number. The way @code{print} labels its output is designed to
5329remind you of this. Just @code{$} refers to the most recent value in
5330the history, and @code{$$} refers to the value before that.
5331@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5332is the value just prior to @code{$$}, @code{$$1} is equivalent to
5333@code{$$}, and @code{$$0} is equivalent to @code{$}.
5334
5335For example, suppose you have just printed a pointer to a structure and
5336want to see the contents of the structure. It suffices to type
5337
474c8240 5338@smallexample
c906108c 5339p *$
474c8240 5340@end smallexample
c906108c
SS
5341
5342If you have a chain of structures where the component @code{next} points
5343to the next one, you can print the contents of the next one with this:
5344
474c8240 5345@smallexample
c906108c 5346p *$.next
474c8240 5347@end smallexample
c906108c
SS
5348
5349@noindent
5350You can print successive links in the chain by repeating this
5351command---which you can do by just typing @key{RET}.
5352
5353Note that the history records values, not expressions. If the value of
5354@code{x} is 4 and you type these commands:
5355
474c8240 5356@smallexample
c906108c
SS
5357print x
5358set x=5
474c8240 5359@end smallexample
c906108c
SS
5360
5361@noindent
5362then the value recorded in the value history by the @code{print} command
5363remains 4 even though the value of @code{x} has changed.
5364
5365@table @code
5366@kindex show values
5367@item show values
5368Print the last ten values in the value history, with their item numbers.
5369This is like @samp{p@ $$9} repeated ten times, except that @code{show
5370values} does not change the history.
5371
5372@item show values @var{n}
5373Print ten history values centered on history item number @var{n}.
5374
5375@item show values +
5376Print ten history values just after the values last printed. If no more
5377values are available, @code{show values +} produces no display.
5378@end table
5379
5380Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5381same effect as @samp{show values +}.
5382
6d2ebf8b 5383@node Convenience Vars
c906108c
SS
5384@section Convenience variables
5385
5386@cindex convenience variables
5387@value{GDBN} provides @dfn{convenience variables} that you can use within
5388@value{GDBN} to hold on to a value and refer to it later. These variables
5389exist entirely within @value{GDBN}; they are not part of your program, and
5390setting a convenience variable has no direct effect on further execution
5391of your program. That is why you can use them freely.
5392
5393Convenience variables are prefixed with @samp{$}. Any name preceded by
5394@samp{$} can be used for a convenience variable, unless it is one of
d4f3574e 5395the predefined machine-specific register names (@pxref{Registers, ,Registers}).
c906108c
SS
5396(Value history references, in contrast, are @emph{numbers} preceded
5397by @samp{$}. @xref{Value History, ,Value history}.)
5398
5399You can save a value in a convenience variable with an assignment
5400expression, just as you would set a variable in your program.
5401For example:
5402
474c8240 5403@smallexample
c906108c 5404set $foo = *object_ptr
474c8240 5405@end smallexample
c906108c
SS
5406
5407@noindent
5408would save in @code{$foo} the value contained in the object pointed to by
5409@code{object_ptr}.
5410
5411Using a convenience variable for the first time creates it, but its
5412value is @code{void} until you assign a new value. You can alter the
5413value with another assignment at any time.
5414
5415Convenience variables have no fixed types. You can assign a convenience
5416variable any type of value, including structures and arrays, even if
5417that variable already has a value of a different type. The convenience
5418variable, when used as an expression, has the type of its current value.
5419
5420@table @code
5421@kindex show convenience
5422@item show convenience
5423Print a list of convenience variables used so far, and their values.
d4f3574e 5424Abbreviated @code{show conv}.
c906108c
SS
5425@end table
5426
5427One of the ways to use a convenience variable is as a counter to be
5428incremented or a pointer to be advanced. For example, to print
5429a field from successive elements of an array of structures:
5430
474c8240 5431@smallexample
c906108c
SS
5432set $i = 0
5433print bar[$i++]->contents
474c8240 5434@end smallexample
c906108c 5435
d4f3574e
SS
5436@noindent
5437Repeat that command by typing @key{RET}.
c906108c
SS
5438
5439Some convenience variables are created automatically by @value{GDBN} and given
5440values likely to be useful.
5441
5442@table @code
41afff9a 5443@vindex $_@r{, convenience variable}
c906108c
SS
5444@item $_
5445The variable @code{$_} is automatically set by the @code{x} command to
5446the last address examined (@pxref{Memory, ,Examining memory}). Other
5447commands which provide a default address for @code{x} to examine also
5448set @code{$_} to that address; these commands include @code{info line}
5449and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5450except when set by the @code{x} command, in which case it is a pointer
5451to the type of @code{$__}.
5452
41afff9a 5453@vindex $__@r{, convenience variable}
c906108c
SS
5454@item $__
5455The variable @code{$__} is automatically set by the @code{x} command
5456to the value found in the last address examined. Its type is chosen
5457to match the format in which the data was printed.
5458
5459@item $_exitcode
41afff9a 5460@vindex $_exitcode@r{, convenience variable}
c906108c
SS
5461The variable @code{$_exitcode} is automatically set to the exit code when
5462the program being debugged terminates.
5463@end table
5464
53a5351d
JM
5465On HP-UX systems, if you refer to a function or variable name that
5466begins with a dollar sign, @value{GDBN} searches for a user or system
5467name first, before it searches for a convenience variable.
c906108c 5468
6d2ebf8b 5469@node Registers
c906108c
SS
5470@section Registers
5471
5472@cindex registers
5473You can refer to machine register contents, in expressions, as variables
5474with names starting with @samp{$}. The names of registers are different
5475for each machine; use @code{info registers} to see the names used on
5476your machine.
5477
5478@table @code
5479@kindex info registers
5480@item info registers
5481Print the names and values of all registers except floating-point
5482registers (in the selected stack frame).
5483
5484@kindex info all-registers
5485@cindex floating point registers
5486@item info all-registers
5487Print the names and values of all registers, including floating-point
5488registers.
5489
5490@item info registers @var{regname} @dots{}
5491Print the @dfn{relativized} value of each specified register @var{regname}.
5d161b24
DB
5492As discussed in detail below, register values are normally relative to
5493the selected stack frame. @var{regname} may be any register name valid on
c906108c
SS
5494the machine you are using, with or without the initial @samp{$}.
5495@end table
5496
5497@value{GDBN} has four ``standard'' register names that are available (in
5498expressions) on most machines---whenever they do not conflict with an
5499architecture's canonical mnemonics for registers. The register names
5500@code{$pc} and @code{$sp} are used for the program counter register and
5501the stack pointer. @code{$fp} is used for a register that contains a
5502pointer to the current stack frame, and @code{$ps} is used for a
5503register that contains the processor status. For example,
5504you could print the program counter in hex with
5505
474c8240 5506@smallexample
c906108c 5507p/x $pc
474c8240 5508@end smallexample
c906108c
SS
5509
5510@noindent
5511or print the instruction to be executed next with
5512
474c8240 5513@smallexample
c906108c 5514x/i $pc
474c8240 5515@end smallexample
c906108c
SS
5516
5517@noindent
5518or add four to the stack pointer@footnote{This is a way of removing
5519one word from the stack, on machines where stacks grow downward in
5520memory (most machines, nowadays). This assumes that the innermost
5521stack frame is selected; setting @code{$sp} is not allowed when other
5522stack frames are selected. To pop entire frames off the stack,
5523regardless of machine architecture, use @code{return};
d4f3574e 5524see @ref{Returning, ,Returning from a function}.} with
c906108c 5525
474c8240 5526@smallexample
c906108c 5527set $sp += 4
474c8240 5528@end smallexample
c906108c
SS
5529
5530Whenever possible, these four standard register names are available on
5531your machine even though the machine has different canonical mnemonics,
5532so long as there is no conflict. The @code{info registers} command
5533shows the canonical names. For example, on the SPARC, @code{info
5534registers} displays the processor status register as @code{$psr} but you
d4f3574e
SS
5535can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5536is an alias for the @sc{eflags} register.
c906108c
SS
5537
5538@value{GDBN} always considers the contents of an ordinary register as an
5539integer when the register is examined in this way. Some machines have
5540special registers which can hold nothing but floating point; these
5541registers are considered to have floating point values. There is no way
5542to refer to the contents of an ordinary register as floating point value
5543(although you can @emph{print} it as a floating point value with
5544@samp{print/f $@var{regname}}).
5545
5546Some registers have distinct ``raw'' and ``virtual'' data formats. This
5547means that the data format in which the register contents are saved by
5548the operating system is not the same one that your program normally
5549sees. For example, the registers of the 68881 floating point
5550coprocessor are always saved in ``extended'' (raw) format, but all C
5551programs expect to work with ``double'' (virtual) format. In such
5d161b24 5552cases, @value{GDBN} normally works with the virtual format only (the format
c906108c
SS
5553that makes sense for your program), but the @code{info registers} command
5554prints the data in both formats.
5555
5556Normally, register values are relative to the selected stack frame
5557(@pxref{Selection, ,Selecting a frame}). This means that you get the
5558value that the register would contain if all stack frames farther in
5559were exited and their saved registers restored. In order to see the
5560true contents of hardware registers, you must select the innermost
5561frame (with @samp{frame 0}).
5562
5563However, @value{GDBN} must deduce where registers are saved, from the machine
5564code generated by your compiler. If some registers are not saved, or if
5565@value{GDBN} is unable to locate the saved registers, the selected stack
5566frame makes no difference.
5567
6d2ebf8b 5568@node Floating Point Hardware
c906108c
SS
5569@section Floating point hardware
5570@cindex floating point
5571
5572Depending on the configuration, @value{GDBN} may be able to give
5573you more information about the status of the floating point hardware.
5574
5575@table @code
5576@kindex info float
5577@item info float
5578Display hardware-dependent information about the floating
5579point unit. The exact contents and layout vary depending on the
5580floating point chip. Currently, @samp{info float} is supported on
5581the ARM and x86 machines.
5582@end table
c906108c 5583
29e57380 5584@node Memory Region Attributes
16d9dec6 5585@section Memory region attributes
29e57380
C
5586@cindex memory region attributes
5587
5588@dfn{Memory region attributes} allow you to describe special handling
5589required by regions of your target's memory. @value{GDBN} uses attributes
5590to determine whether to allow certain types of memory accesses; whether to
5591use specific width accesses; and whether to cache target memory.
5592
5593Defined memory regions can be individually enabled and disabled. When a
5594memory region is disabled, @value{GDBN} uses the default attributes when
5595accessing memory in that region. Similarly, if no memory regions have
5596been defined, @value{GDBN} uses the default attributes when accessing
5597all memory.
5598
5599When a memory region is defined, it is given a number to identify it;
5600to enable, disable, or remove a memory region, you specify that number.
5601
5602@table @code
5603@kindex mem
59649f2e 5604@item mem @var{address1} @var{address2} @var{attributes}@dots{}
29e57380
C
5605Define memory region bounded by @var{address1} and @var{address2}
5606with attributes @var{attributes}@dots{}.
5607
5608@kindex delete mem
5609@item delete mem @var{nums}@dots{}
59649f2e 5610Remove memory regions @var{nums}@dots{}.
29e57380
C
5611
5612@kindex disable mem
5613@item disable mem @var{nums}@dots{}
59649f2e 5614Disable memory regions @var{nums}@dots{}.
29e57380
C
5615A disabled memory region is not forgotten.
5616It may be enabled again later.
5617
5618@kindex enable mem
5619@item enable mem @var{nums}@dots{}
59649f2e 5620Enable memory regions @var{nums}@dots{}.
29e57380
C
5621
5622@kindex info mem
5623@item info mem
5624Print a table of all defined memory regions, with the following columns
5625for each region.
5626
5627@table @emph
5628@item Memory Region Number
5629@item Enabled or Disabled.
5630Enabled memory regions are marked with @samp{y}.
5631Disabled memory regions are marked with @samp{n}.
5632
5633@item Lo Address
5634The address defining the inclusive lower bound of the memory region.
5635
5636@item Hi Address
5637The address defining the exclusive upper bound of the memory region.
5638
5639@item Attributes
5640The list of attributes set for this memory region.
5641@end table
5642@end table
5643
5644
5645@subsection Attributes
5646
5647@subsubsection Memory Access Mode
5648The access mode attributes set whether @value{GDBN} may make read or
5649write accesses to a memory region.
5650
5651While these attributes prevent @value{GDBN} from performing invalid
5652memory accesses, they do nothing to prevent the target system, I/O DMA,
5653etc. from accessing memory.
5654
5655@table @code
5656@item ro
5657Memory is read only.
5658@item wo
5659Memory is write only.
5660@item rw
6ca652b0 5661Memory is read/write. This is the default.
29e57380
C
5662@end table
5663
5664@subsubsection Memory Access Size
5665The acccess size attributes tells @value{GDBN} to use specific sized
5666accesses in the memory region. Often memory mapped device registers
5667require specific sized accesses. If no access size attribute is
5668specified, @value{GDBN} may use accesses of any size.
5669
5670@table @code
5671@item 8
5672Use 8 bit memory accesses.
5673@item 16
5674Use 16 bit memory accesses.
5675@item 32
5676Use 32 bit memory accesses.
5677@item 64
5678Use 64 bit memory accesses.
5679@end table
5680
5681@c @subsubsection Hardware/Software Breakpoints
5682@c The hardware/software breakpoint attributes set whether @value{GDBN}
5683@c will use hardware or software breakpoints for the internal breakpoints
5684@c used by the step, next, finish, until, etc. commands.
5685@c
5686@c @table @code
5687@c @item hwbreak
5688@c Always use hardware breakpoints
5689@c @item swbreak (default)
5690@c @end table
5691
5692@subsubsection Data Cache
5693The data cache attributes set whether @value{GDBN} will cache target
5694memory. While this generally improves performance by reducing debug
5695protocol overhead, it can lead to incorrect results because @value{GDBN}
5696does not know about volatile variables or memory mapped device
5697registers.
5698
5699@table @code
5700@item cache
5701Enable @value{GDBN} to cache target memory.
6ca652b0
EZ
5702@item nocache
5703Disable @value{GDBN} from caching target memory. This is the default.
29e57380
C
5704@end table
5705
5706@c @subsubsection Memory Write Verification
5707@c The memory write verification attributes set whether @value{GDBN}
5708@c will re-reads data after each write to verify the write was successful.
5709@c
5710@c @table @code
5711@c @item verify
5712@c @item noverify (default)
5713@c @end table
5714
16d9dec6
MS
5715@node Dump/Restore Files
5716@section Copy between memory and a file
5717@cindex dump/restore files
5718@cindex append data to a file
5719@cindex dump data to a file
5720@cindex restore data from a file
5721@kindex dump
5722@kindex append
5723@kindex restore
5724
5725The commands @code{dump}, @code{append}, and @code{restore} are used
5726for copying data between target memory and a file. Data is written
5727into a file using @code{dump} or @code{append}, and restored from a
5728file into memory by using @code{restore}. Files may be binary, srec,
5729intel hex, or tekhex (but only binary files can be appended).
5730
5731@table @code
5732@kindex dump binary
5733@kindex append binary
5734@item dump binary memory @var{filename} @var{start_addr} @var{end_addr}
5735Dump contents of memory from @var{start_addr} to @var{end_addr} into
5736raw binary format file @var{filename}.
5737
5738@item append binary memory @var{filename} @var{start_addr} @var{end_addr}
5739Append contents of memory from @var{start_addr} to @var{end_addr} to
5740raw binary format file @var{filename}.
5741
5742@item dump binary value @var{filename} @var{expression}
5743Dump value of @var{expression} into raw binary format file @var{filename}.
5744
5745@item append binary memory @var{filename} @var{expression}
5746Append value of @var{expression} to raw binary format file @var{filename}.
5747
5748@kindex dump ihex
5749@item dump ihex memory @var{filename} @var{start_addr} @var{end_addr}
5750Dump contents of memory from @var{start_addr} to @var{end_addr} into
5751intel hex format file @var{filename}.
5752
5753@item dump ihex value @var{filename} @var{expression}
5754Dump value of @var{expression} into intel hex format file @var{filename}.
5755
5756@kindex dump srec
5757@item dump srec memory @var{filename} @var{start_addr} @var{end_addr}
5758Dump contents of memory from @var{start_addr} to @var{end_addr} into
5759srec format file @var{filename}.
5760
5761@item dump srec value @var{filename} @var{expression}
5762Dump value of @var{expression} into srec format file @var{filename}.
5763
5764@kindex dump tekhex
5765@item dump tekhex memory @var{filename} @var{start_addr} @var{end_addr}
5766Dump contents of memory from @var{start_addr} to @var{end_addr} into
5767tekhex format file @var{filename}.
5768
5769@item dump tekhex value @var{filename} @var{expression}
5770Dump value of @var{expression} into tekhex format file @var{filename}.
5771
5772@item restore @var{filename} @var{[binary]} @var{bias} @var{start} @var{end}
5773Restore the contents of file @var{filename} into memory. The @code{restore}
5774command can automatically recognize any known bfd file format, except for
5775raw binary. To restore a raw binary file you must use the optional argument
5776@var{binary} after the filename.
5777
5778If @var{bias} is non-zero, its value will be added to the addresses
5779contained in the file. Binary files always start at address zero, so
5780they will be restored at address @var{bias}. Other bfd files have
5781a built-in location; they will be restored at offset @var{bias}
5782from that location.
5783
5784If @var{start} and/or @var{end} are non-zero, then only data between
5785file offset @var{start} and file offset @var{end} will be restored.
5786These offsets are relative to the addresses in the file, before
5787the @var{bias} argument is applied.
5788
5789@end table
5790
e2e0bcd1
JB
5791@node Macros
5792@chapter C Preprocessor Macros
5793
5794Some languages, such as C and C++, provide a way to define and invoke
5795``preprocessor macros'' which expand into strings of tokens.
5796@value{GDBN} can evaluate expressions containing macro invocations, show
5797the result of macro expansion, and show a macro's definition, including
5798where it was defined.
5799
5800You may need to compile your program specially to provide @value{GDBN}
5801with information about preprocessor macros. Most compilers do not
5802include macros in their debugging information, even when you compile
5803with the @option{-g} flag. @xref{Compilation}.
5804
5805A program may define a macro at one point, remove that definition later,
5806and then provide a different definition after that. Thus, at different
5807points in the program, a macro may have different definitions, or have
5808no definition at all. If there is a current stack frame, @value{GDBN}
5809uses the macros in scope at that frame's source code line. Otherwise,
5810@value{GDBN} uses the macros in scope at the current listing location;
5811see @ref{List}.
5812
5813At the moment, @value{GDBN} does not support the @code{##}
5814token-splicing operator, the @code{#} stringification operator, or
5815variable-arity macros.
5816
5817Whenever @value{GDBN} evaluates an expression, it always expands any
5818macro invocations present in the expression. @value{GDBN} also provides
5819the following commands for working with macros explicitly.
5820
5821@table @code
5822
5823@kindex macro expand
5824@cindex macro expansion, showing the results of preprocessor
5825@cindex preprocessor macro expansion, showing the results of
5826@cindex expanding preprocessor macros
5827@item macro expand @var{expression}
5828@itemx macro exp @var{expression}
5829Show the results of expanding all preprocessor macro invocations in
5830@var{expression}. Since @value{GDBN} simply expands macros, but does
5831not parse the result, @var{expression} need not be a valid expression;
5832it can be any string of tokens.
5833
5834@kindex macro expand-once
5835@item macro expand-once @var{expression}
5836@itemx macro exp1 @var{expression}
5837@i{(This command is not yet implemented.)} Show the results of
5838expanding those preprocessor macro invocations that appear explicitly in
5839@var{expression}. Macro invocations appearing in that expansion are
5840left unchanged. This command allows you to see the effect of a
5841particular macro more clearly, without being confused by further
5842expansions. Since @value{GDBN} simply expands macros, but does not
5843parse the result, @var{expression} need not be a valid expression; it
5844can be any string of tokens.
5845
475b0867 5846@kindex info macro
e2e0bcd1
JB
5847@cindex macro definition, showing
5848@cindex definition, showing a macro's
475b0867 5849@item info macro @var{macro}
e2e0bcd1
JB
5850Show the definition of the macro named @var{macro}, and describe the
5851source location where that definition was established.
5852
5853@kindex macro define
5854@cindex user-defined macros
5855@cindex defining macros interactively
5856@cindex macros, user-defined
5857@item macro define @var{macro} @var{replacement-list}
5858@itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
5859@i{(This command is not yet implemented.)} Introduce a definition for a
5860preprocessor macro named @var{macro}, invocations of which are replaced
5861by the tokens given in @var{replacement-list}. The first form of this
5862command defines an ``object-like'' macro, which takes no arguments; the
5863second form defines a ``function-like'' macro, which takes the arguments
5864given in @var{arglist}.
5865
5866A definition introduced by this command is in scope in every expression
5867evaluated in @value{GDBN}, until it is removed with the @command{macro
5868undef} command, described below. The definition overrides all
5869definitions for @var{macro} present in the program being debugged, as
5870well as any previous user-supplied definition.
5871
5872@kindex macro undef
5873@item macro undef @var{macro}
5874@i{(This command is not yet implemented.)} Remove any user-supplied
5875definition for the macro named @var{macro}. This command only affects
5876definitions provided with the @command{macro define} command, described
5877above; it cannot remove definitions present in the program being
5878debugged.
5879
5880@end table
5881
5882@cindex macros, example of debugging with
5883Here is a transcript showing the above commands in action. First, we
5884show our source files:
5885
5886@smallexample
5887$ cat sample.c
5888#include <stdio.h>
5889#include "sample.h"
5890
5891#define M 42
5892#define ADD(x) (M + x)
5893
5894main ()
5895@{
5896#define N 28
5897 printf ("Hello, world!\n");
5898#undef N
5899 printf ("We're so creative.\n");
5900#define N 1729
5901 printf ("Goodbye, world!\n");
5902@}
5903$ cat sample.h
5904#define Q <
5905$
5906@end smallexample
5907
5908Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
5909We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
5910compiler includes information about preprocessor macros in the debugging
5911information.
5912
5913@smallexample
5914$ gcc -gdwarf-2 -g3 sample.c -o sample
5915$
5916@end smallexample
5917
5918Now, we start @value{GDBN} on our sample program:
5919
5920@smallexample
5921$ gdb -nw sample
5922GNU gdb 2002-05-06-cvs
5923Copyright 2002 Free Software Foundation, Inc.
5924GDB is free software, @dots{}
5925(gdb)
5926@end smallexample
5927
5928We can expand macros and examine their definitions, even when the
5929program is not running. @value{GDBN} uses the current listing position
5930to decide which macro definitions are in scope:
5931
5932@smallexample
5933(gdb) list main
59343
59354 #define M 42
59365 #define ADD(x) (M + x)
59376
59387 main ()
59398 @{
59409 #define N 28
594110 printf ("Hello, world!\n");
594211 #undef N
594312 printf ("We're so creative.\n");
475b0867 5944(gdb) info macro ADD
e2e0bcd1
JB
5945Defined at /home/jimb/gdb/macros/play/sample.c:5
5946#define ADD(x) (M + x)
475b0867 5947(gdb) info macro Q
e2e0bcd1
JB
5948Defined at /home/jimb/gdb/macros/play/sample.h:1
5949 included at /home/jimb/gdb/macros/play/sample.c:2
5950#define Q <
5951(gdb) macro expand ADD(1)
5952expands to: (42 + 1)
5953(gdb) macro expand-once ADD(1)
5954expands to: once (M + 1)
5955(gdb)
5956@end smallexample
5957
5958In the example above, note that @command{macro expand-once} expands only
5959the macro invocation explicit in the original text --- the invocation of
5960@code{ADD} --- but does not expand the invocation of the macro @code{M},
5961which was introduced by @code{ADD}.
5962
5963Once the program is running, GDB uses the macro definitions in force at
5964the source line of the current stack frame:
5965
5966@smallexample
5967(gdb) break main
5968Breakpoint 1 at 0x8048370: file sample.c, line 10.
5969(gdb) run
5970Starting program: /home/jimb/gdb/macros/play/sample
5971
5972Breakpoint 1, main () at sample.c:10
597310 printf ("Hello, world!\n");
5974(gdb)
5975@end smallexample
5976
5977At line 10, the definition of the macro @code{N} at line 9 is in force:
5978
5979@smallexample
475b0867 5980(gdb) info macro N
e2e0bcd1
JB
5981Defined at /home/jimb/gdb/macros/play/sample.c:9
5982#define N 28
5983(gdb) macro expand N Q M
5984expands to: 28 < 42
5985(gdb) print N Q M
5986$1 = 1
5987(gdb)
5988@end smallexample
5989
5990As we step over directives that remove @code{N}'s definition, and then
5991give it a new definition, @value{GDBN} finds the definition (or lack
5992thereof) in force at each point:
5993
5994@smallexample
5995(gdb) next
5996Hello, world!
599712 printf ("We're so creative.\n");
475b0867 5998(gdb) info macro N
e2e0bcd1
JB
5999The symbol `N' has no definition as a C/C++ preprocessor macro
6000at /home/jimb/gdb/macros/play/sample.c:12
6001(gdb) next
6002We're so creative.
600314 printf ("Goodbye, world!\n");
475b0867 6004(gdb) info macro N
e2e0bcd1
JB
6005Defined at /home/jimb/gdb/macros/play/sample.c:13
6006#define N 1729
6007(gdb) macro expand N Q M
6008expands to: 1729 < 42
6009(gdb) print N Q M
6010$2 = 0
6011(gdb)
6012@end smallexample
6013
6014
b37052ae
EZ
6015@node Tracepoints
6016@chapter Tracepoints
6017@c This chapter is based on the documentation written by Michael
6018@c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6019
6020@cindex tracepoints
6021In some applications, it is not feasible for the debugger to interrupt
6022the program's execution long enough for the developer to learn
6023anything helpful about its behavior. If the program's correctness
6024depends on its real-time behavior, delays introduced by a debugger
6025might cause the program to change its behavior drastically, or perhaps
6026fail, even when the code itself is correct. It is useful to be able
6027to observe the program's behavior without interrupting it.
6028
6029Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6030specify locations in the program, called @dfn{tracepoints}, and
6031arbitrary expressions to evaluate when those tracepoints are reached.
6032Later, using the @code{tfind} command, you can examine the values
6033those expressions had when the program hit the tracepoints. The
6034expressions may also denote objects in memory---structures or arrays,
6035for example---whose values @value{GDBN} should record; while visiting
6036a particular tracepoint, you may inspect those objects as if they were
6037in memory at that moment. However, because @value{GDBN} records these
6038values without interacting with you, it can do so quickly and
6039unobtrusively, hopefully not disturbing the program's behavior.
6040
6041The tracepoint facility is currently available only for remote
2c0069bb
EZ
6042targets. @xref{Targets}. In addition, your remote target must know how
6043to collect trace data. This functionality is implemented in the remote
6044stub; however, none of the stubs distributed with @value{GDBN} support
6045tracepoints as of this writing.
b37052ae
EZ
6046
6047This chapter describes the tracepoint commands and features.
6048
6049@menu
6050* Set Tracepoints::
6051* Analyze Collected Data::
6052* Tracepoint Variables::
6053@end menu
6054
6055@node Set Tracepoints
6056@section Commands to Set Tracepoints
6057
6058Before running such a @dfn{trace experiment}, an arbitrary number of
6059tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6060tracepoint has a number assigned to it by @value{GDBN}. Like with
6061breakpoints, tracepoint numbers are successive integers starting from
6062one. Many of the commands associated with tracepoints take the
6063tracepoint number as their argument, to identify which tracepoint to
6064work on.
6065
6066For each tracepoint, you can specify, in advance, some arbitrary set
6067of data that you want the target to collect in the trace buffer when
6068it hits that tracepoint. The collected data can include registers,
6069local variables, or global data. Later, you can use @value{GDBN}
6070commands to examine the values these data had at the time the
6071tracepoint was hit.
6072
6073This section describes commands to set tracepoints and associated
6074conditions and actions.
6075
6076@menu
6077* Create and Delete Tracepoints::
6078* Enable and Disable Tracepoints::
6079* Tracepoint Passcounts::
6080* Tracepoint Actions::
6081* Listing Tracepoints::
6082* Starting and Stopping Trace Experiment::
6083@end menu
6084
6085@node Create and Delete Tracepoints
6086@subsection Create and Delete Tracepoints
6087
6088@table @code
6089@cindex set tracepoint
6090@kindex trace
6091@item trace
6092The @code{trace} command is very similar to the @code{break} command.
6093Its argument can be a source line, a function name, or an address in
6094the target program. @xref{Set Breaks}. The @code{trace} command
6095defines a tracepoint, which is a point in the target program where the
6096debugger will briefly stop, collect some data, and then allow the
6097program to continue. Setting a tracepoint or changing its commands
6098doesn't take effect until the next @code{tstart} command; thus, you
6099cannot change the tracepoint attributes once a trace experiment is
6100running.
6101
6102Here are some examples of using the @code{trace} command:
6103
6104@smallexample
6105(@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6106
6107(@value{GDBP}) @b{trace +2} // 2 lines forward
6108
6109(@value{GDBP}) @b{trace my_function} // first source line of function
6110
6111(@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6112
6113(@value{GDBP}) @b{trace *0x2117c4} // an address
6114@end smallexample
6115
6116@noindent
6117You can abbreviate @code{trace} as @code{tr}.
6118
6119@vindex $tpnum
6120@cindex last tracepoint number
6121@cindex recent tracepoint number
6122@cindex tracepoint number
6123The convenience variable @code{$tpnum} records the tracepoint number
6124of the most recently set tracepoint.
6125
6126@kindex delete tracepoint
6127@cindex tracepoint deletion
6128@item delete tracepoint @r{[}@var{num}@r{]}
6129Permanently delete one or more tracepoints. With no argument, the
6130default is to delete all tracepoints.
6131
6132Examples:
6133
6134@smallexample
6135(@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6136
6137(@value{GDBP}) @b{delete trace} // remove all tracepoints
6138@end smallexample
6139
6140@noindent
6141You can abbreviate this command as @code{del tr}.
6142@end table
6143
6144@node Enable and Disable Tracepoints
6145@subsection Enable and Disable Tracepoints
6146
6147@table @code
6148@kindex disable tracepoint
6149@item disable tracepoint @r{[}@var{num}@r{]}
6150Disable tracepoint @var{num}, or all tracepoints if no argument
6151@var{num} is given. A disabled tracepoint will have no effect during
6152the next trace experiment, but it is not forgotten. You can re-enable
6153a disabled tracepoint using the @code{enable tracepoint} command.
6154
6155@kindex enable tracepoint
6156@item enable tracepoint @r{[}@var{num}@r{]}
6157Enable tracepoint @var{num}, or all tracepoints. The enabled
6158tracepoints will become effective the next time a trace experiment is
6159run.
6160@end table
6161
6162@node Tracepoint Passcounts
6163@subsection Tracepoint Passcounts
6164
6165@table @code
6166@kindex passcount
6167@cindex tracepoint pass count
6168@item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6169Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6170automatically stop a trace experiment. If a tracepoint's passcount is
6171@var{n}, then the trace experiment will be automatically stopped on
6172the @var{n}'th time that tracepoint is hit. If the tracepoint number
6173@var{num} is not specified, the @code{passcount} command sets the
6174passcount of the most recently defined tracepoint. If no passcount is
6175given, the trace experiment will run until stopped explicitly by the
6176user.
6177
6178Examples:
6179
6180@smallexample
6826cf00
EZ
6181(@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6182@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
b37052ae
EZ
6183
6184(@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6826cf00 6185@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
b37052ae
EZ
6186(@value{GDBP}) @b{trace foo}
6187(@value{GDBP}) @b{pass 3}
6188(@value{GDBP}) @b{trace bar}
6189(@value{GDBP}) @b{pass 2}
6190(@value{GDBP}) @b{trace baz}
6191(@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6826cf00
EZ
6192@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6193@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6194@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
b37052ae
EZ
6195@end smallexample
6196@end table
6197
6198@node Tracepoint Actions
6199@subsection Tracepoint Action Lists
6200
6201@table @code
6202@kindex actions
6203@cindex tracepoint actions
6204@item actions @r{[}@var{num}@r{]}
6205This command will prompt for a list of actions to be taken when the
6206tracepoint is hit. If the tracepoint number @var{num} is not
6207specified, this command sets the actions for the one that was most
6208recently defined (so that you can define a tracepoint and then say
6209@code{actions} without bothering about its number). You specify the
6210actions themselves on the following lines, one action at a time, and
6211terminate the actions list with a line containing just @code{end}. So
6212far, the only defined actions are @code{collect} and
6213@code{while-stepping}.
6214
6215@cindex remove actions from a tracepoint
6216To remove all actions from a tracepoint, type @samp{actions @var{num}}
6217and follow it immediately with @samp{end}.
6218
6219@smallexample
6220(@value{GDBP}) @b{collect @var{data}} // collect some data
6221
6826cf00 6222(@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
b37052ae 6223
6826cf00 6224(@value{GDBP}) @b{end} // signals the end of actions.
b37052ae
EZ
6225@end smallexample
6226
6227In the following example, the action list begins with @code{collect}
6228commands indicating the things to be collected when the tracepoint is
6229hit. Then, in order to single-step and collect additional data
6230following the tracepoint, a @code{while-stepping} command is used,
6231followed by the list of things to be collected while stepping. The
6232@code{while-stepping} command is terminated by its own separate
6233@code{end} command. Lastly, the action list is terminated by an
6234@code{end} command.
6235
6236@smallexample
6237(@value{GDBP}) @b{trace foo}
6238(@value{GDBP}) @b{actions}
6239Enter actions for tracepoint 1, one per line:
6240> collect bar,baz
6241> collect $regs
6242> while-stepping 12
6243 > collect $fp, $sp
6244 > end
6245end
6246@end smallexample
6247
6248@kindex collect @r{(tracepoints)}
6249@item collect @var{expr1}, @var{expr2}, @dots{}
6250Collect values of the given expressions when the tracepoint is hit.
6251This command accepts a comma-separated list of any valid expressions.
6252In addition to global, static, or local variables, the following
6253special arguments are supported:
6254
6255@table @code
6256@item $regs
6257collect all registers
6258
6259@item $args
6260collect all function arguments
6261
6262@item $locals
6263collect all local variables.
6264@end table
6265
6266You can give several consecutive @code{collect} commands, each one
6267with a single argument, or one @code{collect} command with several
6268arguments separated by commas: the effect is the same.
6269
f5c37c66
EZ
6270The command @code{info scope} (@pxref{Symbols, info scope}) is
6271particularly useful for figuring out what data to collect.
6272
b37052ae
EZ
6273@kindex while-stepping @r{(tracepoints)}
6274@item while-stepping @var{n}
6275Perform @var{n} single-step traces after the tracepoint, collecting
6276new data at each step. The @code{while-stepping} command is
6277followed by the list of what to collect while stepping (followed by
6278its own @code{end} command):
6279
6280@smallexample
6281> while-stepping 12
6282 > collect $regs, myglobal
6283 > end
6284>
6285@end smallexample
6286
6287@noindent
6288You may abbreviate @code{while-stepping} as @code{ws} or
6289@code{stepping}.
6290@end table
6291
6292@node Listing Tracepoints
6293@subsection Listing Tracepoints
6294
6295@table @code
6296@kindex info tracepoints
6297@cindex information about tracepoints
6298@item info tracepoints @r{[}@var{num}@r{]}
8a037dd7 6299Display information about the tracepoint @var{num}. If you don't specify
798c8bc6 6300a tracepoint number, displays information about all the tracepoints
b37052ae
EZ
6301defined so far. For each tracepoint, the following information is
6302shown:
6303
6304@itemize @bullet
6305@item
6306its number
6307@item
6308whether it is enabled or disabled
6309@item
6310its address
6311@item
6312its passcount as given by the @code{passcount @var{n}} command
6313@item
6314its step count as given by the @code{while-stepping @var{n}} command
6315@item
6316where in the source files is the tracepoint set
6317@item
6318its action list as given by the @code{actions} command
6319@end itemize
6320
6321@smallexample
6322(@value{GDBP}) @b{info trace}
6323Num Enb Address PassC StepC What
63241 y 0x002117c4 0 0 <gdb_asm>
6826cf00
EZ
63252 y 0x0020dc64 0 0 in g_test at g_test.c:1375
63263 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
b37052ae
EZ
6327(@value{GDBP})
6328@end smallexample
6329
6330@noindent
6331This command can be abbreviated @code{info tp}.
6332@end table
6333
6334@node Starting and Stopping Trace Experiment
6335@subsection Starting and Stopping Trace Experiment
6336
6337@table @code
6338@kindex tstart
6339@cindex start a new trace experiment
6340@cindex collected data discarded
6341@item tstart
6342This command takes no arguments. It starts the trace experiment, and
6343begins collecting data. This has the side effect of discarding all
6344the data collected in the trace buffer during the previous trace
6345experiment.
6346
6347@kindex tstop
6348@cindex stop a running trace experiment
6349@item tstop
6350This command takes no arguments. It ends the trace experiment, and
6351stops collecting data.
6352
6353@strong{Note:} a trace experiment and data collection may stop
6354automatically if any tracepoint's passcount is reached
6355(@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6356
6357@kindex tstatus
6358@cindex status of trace data collection
6359@cindex trace experiment, status of
6360@item tstatus
6361This command displays the status of the current trace data
6362collection.
6363@end table
6364
6365Here is an example of the commands we described so far:
6366
6367@smallexample
6368(@value{GDBP}) @b{trace gdb_c_test}
6369(@value{GDBP}) @b{actions}
6370Enter actions for tracepoint #1, one per line.
6371> collect $regs,$locals,$args
6372> while-stepping 11
6373 > collect $regs
6374 > end
6375> end
6376(@value{GDBP}) @b{tstart}
6377 [time passes @dots{}]
6378(@value{GDBP}) @b{tstop}
6379@end smallexample
6380
6381
6382@node Analyze Collected Data
6383@section Using the collected data
6384
6385After the tracepoint experiment ends, you use @value{GDBN} commands
6386for examining the trace data. The basic idea is that each tracepoint
6387collects a trace @dfn{snapshot} every time it is hit and another
6388snapshot every time it single-steps. All these snapshots are
6389consecutively numbered from zero and go into a buffer, and you can
6390examine them later. The way you examine them is to @dfn{focus} on a
6391specific trace snapshot. When the remote stub is focused on a trace
6392snapshot, it will respond to all @value{GDBN} requests for memory and
6393registers by reading from the buffer which belongs to that snapshot,
6394rather than from @emph{real} memory or registers of the program being
6395debugged. This means that @strong{all} @value{GDBN} commands
6396(@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6397behave as if we were currently debugging the program state as it was
6398when the tracepoint occurred. Any requests for data that are not in
6399the buffer will fail.
6400
6401@menu
6402* tfind:: How to select a trace snapshot
6403* tdump:: How to display all data for a snapshot
6404* save-tracepoints:: How to save tracepoints for a future run
6405@end menu
6406
6407@node tfind
6408@subsection @code{tfind @var{n}}
6409
6410@kindex tfind
6411@cindex select trace snapshot
6412@cindex find trace snapshot
6413The basic command for selecting a trace snapshot from the buffer is
6414@code{tfind @var{n}}, which finds trace snapshot number @var{n},
6415counting from zero. If no argument @var{n} is given, the next
6416snapshot is selected.
6417
6418Here are the various forms of using the @code{tfind} command.
6419
6420@table @code
6421@item tfind start
6422Find the first snapshot in the buffer. This is a synonym for
6423@code{tfind 0} (since 0 is the number of the first snapshot).
6424
6425@item tfind none
6426Stop debugging trace snapshots, resume @emph{live} debugging.
6427
6428@item tfind end
6429Same as @samp{tfind none}.
6430
6431@item tfind
6432No argument means find the next trace snapshot.
6433
6434@item tfind -
6435Find the previous trace snapshot before the current one. This permits
6436retracing earlier steps.
6437
6438@item tfind tracepoint @var{num}
6439Find the next snapshot associated with tracepoint @var{num}. Search
6440proceeds forward from the last examined trace snapshot. If no
6441argument @var{num} is given, it means find the next snapshot collected
6442for the same tracepoint as the current snapshot.
6443
6444@item tfind pc @var{addr}
6445Find the next snapshot associated with the value @var{addr} of the
6446program counter. Search proceeds forward from the last examined trace
6447snapshot. If no argument @var{addr} is given, it means find the next
6448snapshot with the same value of PC as the current snapshot.
6449
6450@item tfind outside @var{addr1}, @var{addr2}
6451Find the next snapshot whose PC is outside the given range of
6452addresses.
6453
6454@item tfind range @var{addr1}, @var{addr2}
6455Find the next snapshot whose PC is between @var{addr1} and
6456@var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6457
6458@item tfind line @r{[}@var{file}:@r{]}@var{n}
6459Find the next snapshot associated with the source line @var{n}. If
6460the optional argument @var{file} is given, refer to line @var{n} in
6461that source file. Search proceeds forward from the last examined
6462trace snapshot. If no argument @var{n} is given, it means find the
6463next line other than the one currently being examined; thus saying
6464@code{tfind line} repeatedly can appear to have the same effect as
6465stepping from line to line in a @emph{live} debugging session.
6466@end table
6467
6468The default arguments for the @code{tfind} commands are specifically
6469designed to make it easy to scan through the trace buffer. For
6470instance, @code{tfind} with no argument selects the next trace
6471snapshot, and @code{tfind -} with no argument selects the previous
6472trace snapshot. So, by giving one @code{tfind} command, and then
6473simply hitting @key{RET} repeatedly you can examine all the trace
6474snapshots in order. Or, by saying @code{tfind -} and then hitting
6475@key{RET} repeatedly you can examine the snapshots in reverse order.
6476The @code{tfind line} command with no argument selects the snapshot
6477for the next source line executed. The @code{tfind pc} command with
6478no argument selects the next snapshot with the same program counter
6479(PC) as the current frame. The @code{tfind tracepoint} command with
6480no argument selects the next trace snapshot collected by the same
6481tracepoint as the current one.
6482
6483In addition to letting you scan through the trace buffer manually,
6484these commands make it easy to construct @value{GDBN} scripts that
6485scan through the trace buffer and print out whatever collected data
6486you are interested in. Thus, if we want to examine the PC, FP, and SP
6487registers from each trace frame in the buffer, we can say this:
6488
6489@smallexample
6490(@value{GDBP}) @b{tfind start}
6491(@value{GDBP}) @b{while ($trace_frame != -1)}
6492> printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6493 $trace_frame, $pc, $sp, $fp
6494> tfind
6495> end
6496
6497Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6498Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6499Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6500Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6501Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6502Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6503Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6504Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6505Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6506Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6507Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6508@end smallexample
6509
6510Or, if we want to examine the variable @code{X} at each source line in
6511the buffer:
6512
6513@smallexample
6514(@value{GDBP}) @b{tfind start}
6515(@value{GDBP}) @b{while ($trace_frame != -1)}
6516> printf "Frame %d, X == %d\n", $trace_frame, X
6517> tfind line
6518> end
6519
6520Frame 0, X = 1
6521Frame 7, X = 2
6522Frame 13, X = 255
6523@end smallexample
6524
6525@node tdump
6526@subsection @code{tdump}
6527@kindex tdump
6528@cindex dump all data collected at tracepoint
6529@cindex tracepoint data, display
6530
6531This command takes no arguments. It prints all the data collected at
6532the current trace snapshot.
6533
6534@smallexample
6535(@value{GDBP}) @b{trace 444}
6536(@value{GDBP}) @b{actions}
6537Enter actions for tracepoint #2, one per line:
6538> collect $regs, $locals, $args, gdb_long_test
6539> end
6540
6541(@value{GDBP}) @b{tstart}
6542
6543(@value{GDBP}) @b{tfind line 444}
6544#0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6545at gdb_test.c:444
6546444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6547
6548(@value{GDBP}) @b{tdump}
6549Data collected at tracepoint 2, trace frame 1:
6550d0 0xc4aa0085 -995491707
6551d1 0x18 24
6552d2 0x80 128
6553d3 0x33 51
6554d4 0x71aea3d 119204413
6555d5 0x22 34
6556d6 0xe0 224
6557d7 0x380035 3670069
6558a0 0x19e24a 1696330
6559a1 0x3000668 50333288
6560a2 0x100 256
6561a3 0x322000 3284992
6562a4 0x3000698 50333336
6563a5 0x1ad3cc 1758156
6564fp 0x30bf3c 0x30bf3c
6565sp 0x30bf34 0x30bf34
6566ps 0x0 0
6567pc 0x20b2c8 0x20b2c8
6568fpcontrol 0x0 0
6569fpstatus 0x0 0
6570fpiaddr 0x0 0
6571p = 0x20e5b4 "gdb-test"
6572p1 = (void *) 0x11
6573p2 = (void *) 0x22
6574p3 = (void *) 0x33
6575p4 = (void *) 0x44
6576p5 = (void *) 0x55
6577p6 = (void *) 0x66
6578gdb_long_test = 17 '\021'
6579
6580(@value{GDBP})
6581@end smallexample
6582
6583@node save-tracepoints
6584@subsection @code{save-tracepoints @var{filename}}
6585@kindex save-tracepoints
6586@cindex save tracepoints for future sessions
6587
6588This command saves all current tracepoint definitions together with
6589their actions and passcounts, into a file @file{@var{filename}}
6590suitable for use in a later debugging session. To read the saved
6591tracepoint definitions, use the @code{source} command (@pxref{Command
6592Files}).
6593
6594@node Tracepoint Variables
6595@section Convenience Variables for Tracepoints
6596@cindex tracepoint variables
6597@cindex convenience variables for tracepoints
6598
6599@table @code
6600@vindex $trace_frame
6601@item (int) $trace_frame
6602The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6603snapshot is selected.
6604
6605@vindex $tracepoint
6606@item (int) $tracepoint
6607The tracepoint for the current trace snapshot.
6608
6609@vindex $trace_line
6610@item (int) $trace_line
6611The line number for the current trace snapshot.
6612
6613@vindex $trace_file
6614@item (char []) $trace_file
6615The source file for the current trace snapshot.
6616
6617@vindex $trace_func
6618@item (char []) $trace_func
6619The name of the function containing @code{$tracepoint}.
6620@end table
6621
6622Note: @code{$trace_file} is not suitable for use in @code{printf},
6623use @code{output} instead.
6624
6625Here's a simple example of using these convenience variables for
6626stepping through all the trace snapshots and printing some of their
6627data.
6628
6629@smallexample
6630(@value{GDBP}) @b{tfind start}
6631
6632(@value{GDBP}) @b{while $trace_frame != -1}
6633> output $trace_file
6634> printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
6635> tfind
6636> end
6637@end smallexample
6638
df0cd8c5
JB
6639@node Overlays
6640@chapter Debugging Programs That Use Overlays
6641@cindex overlays
6642
6643If your program is too large to fit completely in your target system's
6644memory, you can sometimes use @dfn{overlays} to work around this
6645problem. @value{GDBN} provides some support for debugging programs that
6646use overlays.
6647
6648@menu
6649* How Overlays Work:: A general explanation of overlays.
6650* Overlay Commands:: Managing overlays in @value{GDBN}.
6651* Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
6652 mapped by asking the inferior.
6653* Overlay Sample Program:: A sample program using overlays.
6654@end menu
6655
6656@node How Overlays Work
6657@section How Overlays Work
6658@cindex mapped overlays
6659@cindex unmapped overlays
6660@cindex load address, overlay's
6661@cindex mapped address
6662@cindex overlay area
6663
6664Suppose you have a computer whose instruction address space is only 64
6665kilobytes long, but which has much more memory which can be accessed by
6666other means: special instructions, segment registers, or memory
6667management hardware, for example. Suppose further that you want to
6668adapt a program which is larger than 64 kilobytes to run on this system.
6669
6670One solution is to identify modules of your program which are relatively
6671independent, and need not call each other directly; call these modules
6672@dfn{overlays}. Separate the overlays from the main program, and place
6673their machine code in the larger memory. Place your main program in
6674instruction memory, but leave at least enough space there to hold the
6675largest overlay as well.
6676
6677Now, to call a function located in an overlay, you must first copy that
6678overlay's machine code from the large memory into the space set aside
6679for it in the instruction memory, and then jump to its entry point
6680there.
6681
c928edc0
AC
6682@c NB: In the below the mapped area's size is greater or equal to the
6683@c size of all overlays. This is intentional to remind the developer
6684@c that overlays don't necessarily need to be the same size.
6685
474c8240 6686@smallexample
df0cd8c5 6687@group
c928edc0
AC
6688 Data Instruction Larger
6689Address Space Address Space Address Space
6690+-----------+ +-----------+ +-----------+
6691| | | | | |
6692+-----------+ +-----------+ +-----------+<-- overlay 1
6693| program | | main | .----| overlay 1 | load address
6694| variables | | program | | +-----------+
6695| and heap | | | | | |
6696+-----------+ | | | +-----------+<-- overlay 2
6697| | +-----------+ | | | load address
6698+-----------+ | | | .-| overlay 2 |
6699 | | | | | |
6700 mapped --->+-----------+ | | +-----------+
6701 address | | | | | |
6702 | overlay | <-' | | |
6703 | area | <---' +-----------+<-- overlay 3
6704 | | <---. | | load address
6705 +-----------+ `--| overlay 3 |
6706 | | | |
6707 +-----------+ | |
6708 +-----------+
6709 | |
6710 +-----------+
6711
6712 @anchor{A code overlay}A code overlay
df0cd8c5 6713@end group
474c8240 6714@end smallexample
df0cd8c5 6715
c928edc0
AC
6716The diagram (@pxref{A code overlay}) shows a system with separate data
6717and instruction address spaces. To map an overlay, the program copies
6718its code from the larger address space to the instruction address space.
6719Since the overlays shown here all use the same mapped address, only one
6720may be mapped at a time. For a system with a single address space for
6721data and instructions, the diagram would be similar, except that the
6722program variables and heap would share an address space with the main
6723program and the overlay area.
df0cd8c5
JB
6724
6725An overlay loaded into instruction memory and ready for use is called a
6726@dfn{mapped} overlay; its @dfn{mapped address} is its address in the
6727instruction memory. An overlay not present (or only partially present)
6728in instruction memory is called @dfn{unmapped}; its @dfn{load address}
6729is its address in the larger memory. The mapped address is also called
6730the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
6731called the @dfn{load memory address}, or @dfn{LMA}.
6732
6733Unfortunately, overlays are not a completely transparent way to adapt a
6734program to limited instruction memory. They introduce a new set of
6735global constraints you must keep in mind as you design your program:
6736
6737@itemize @bullet
6738
6739@item
6740Before calling or returning to a function in an overlay, your program
6741must make sure that overlay is actually mapped. Otherwise, the call or
6742return will transfer control to the right address, but in the wrong
6743overlay, and your program will probably crash.
6744
6745@item
6746If the process of mapping an overlay is expensive on your system, you
6747will need to choose your overlays carefully to minimize their effect on
6748your program's performance.
6749
6750@item
6751The executable file you load onto your system must contain each
6752overlay's instructions, appearing at the overlay's load address, not its
6753mapped address. However, each overlay's instructions must be relocated
6754and its symbols defined as if the overlay were at its mapped address.
6755You can use GNU linker scripts to specify different load and relocation
6756addresses for pieces of your program; see @ref{Overlay Description,,,
6757ld.info, Using ld: the GNU linker}.
6758
6759@item
6760The procedure for loading executable files onto your system must be able
6761to load their contents into the larger address space as well as the
6762instruction and data spaces.
6763
6764@end itemize
6765
6766The overlay system described above is rather simple, and could be
6767improved in many ways:
6768
6769@itemize @bullet
6770
6771@item
6772If your system has suitable bank switch registers or memory management
6773hardware, you could use those facilities to make an overlay's load area
6774contents simply appear at their mapped address in instruction space.
6775This would probably be faster than copying the overlay to its mapped
6776area in the usual way.
6777
6778@item
6779If your overlays are small enough, you could set aside more than one
6780overlay area, and have more than one overlay mapped at a time.
6781
6782@item
6783You can use overlays to manage data, as well as instructions. In
6784general, data overlays are even less transparent to your design than
6785code overlays: whereas code overlays only require care when you call or
6786return to functions, data overlays require care every time you access
6787the data. Also, if you change the contents of a data overlay, you
6788must copy its contents back out to its load address before you can copy a
6789different data overlay into the same mapped area.
6790
6791@end itemize
6792
6793
6794@node Overlay Commands
6795@section Overlay Commands
6796
6797To use @value{GDBN}'s overlay support, each overlay in your program must
6798correspond to a separate section of the executable file. The section's
6799virtual memory address and load memory address must be the overlay's
6800mapped and load addresses. Identifying overlays with sections allows
6801@value{GDBN} to determine the appropriate address of a function or
6802variable, depending on whether the overlay is mapped or not.
6803
6804@value{GDBN}'s overlay commands all start with the word @code{overlay};
6805you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
6806
6807@table @code
6808@item overlay off
6809@kindex overlay off
6810Disable @value{GDBN}'s overlay support. When overlay support is
6811disabled, @value{GDBN} assumes that all functions and variables are
6812always present at their mapped addresses. By default, @value{GDBN}'s
6813overlay support is disabled.
6814
6815@item overlay manual
6816@kindex overlay manual
6817@cindex manual overlay debugging
6818Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
6819relies on you to tell it which overlays are mapped, and which are not,
6820using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
6821commands described below.
6822
6823@item overlay map-overlay @var{overlay}
6824@itemx overlay map @var{overlay}
6825@kindex overlay map-overlay
6826@cindex map an overlay
6827Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
6828be the name of the object file section containing the overlay. When an
6829overlay is mapped, @value{GDBN} assumes it can find the overlay's
6830functions and variables at their mapped addresses. @value{GDBN} assumes
6831that any other overlays whose mapped ranges overlap that of
6832@var{overlay} are now unmapped.
6833
6834@item overlay unmap-overlay @var{overlay}
6835@itemx overlay unmap @var{overlay}
6836@kindex overlay unmap-overlay
6837@cindex unmap an overlay
6838Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
6839must be the name of the object file section containing the overlay.
6840When an overlay is unmapped, @value{GDBN} assumes it can find the
6841overlay's functions and variables at their load addresses.
6842
6843@item overlay auto
6844@kindex overlay auto
6845Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
6846consults a data structure the overlay manager maintains in the inferior
6847to see which overlays are mapped. For details, see @ref{Automatic
6848Overlay Debugging}.
6849
6850@item overlay load-target
6851@itemx overlay load
6852@kindex overlay load-target
6853@cindex reloading the overlay table
6854Re-read the overlay table from the inferior. Normally, @value{GDBN}
6855re-reads the table @value{GDBN} automatically each time the inferior
6856stops, so this command should only be necessary if you have changed the
6857overlay mapping yourself using @value{GDBN}. This command is only
6858useful when using automatic overlay debugging.
6859
6860@item overlay list-overlays
6861@itemx overlay list
6862@cindex listing mapped overlays
6863Display a list of the overlays currently mapped, along with their mapped
6864addresses, load addresses, and sizes.
6865
6866@end table
6867
6868Normally, when @value{GDBN} prints a code address, it includes the name
6869of the function the address falls in:
6870
474c8240 6871@smallexample
df0cd8c5
JB
6872(gdb) print main
6873$3 = @{int ()@} 0x11a0 <main>
474c8240 6874@end smallexample
df0cd8c5
JB
6875@noindent
6876When overlay debugging is enabled, @value{GDBN} recognizes code in
6877unmapped overlays, and prints the names of unmapped functions with
6878asterisks around them. For example, if @code{foo} is a function in an
6879unmapped overlay, @value{GDBN} prints it this way:
6880
474c8240 6881@smallexample
df0cd8c5
JB
6882(gdb) overlay list
6883No sections are mapped.
6884(gdb) print foo
6885$5 = @{int (int)@} 0x100000 <*foo*>
474c8240 6886@end smallexample
df0cd8c5
JB
6887@noindent
6888When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
6889name normally:
6890
474c8240 6891@smallexample
df0cd8c5
JB
6892(gdb) overlay list
6893Section .ov.foo.text, loaded at 0x100000 - 0x100034,
6894 mapped at 0x1016 - 0x104a
6895(gdb) print foo
6896$6 = @{int (int)@} 0x1016 <foo>
474c8240 6897@end smallexample
df0cd8c5
JB
6898
6899When overlay debugging is enabled, @value{GDBN} can find the correct
6900address for functions and variables in an overlay, whether or not the
6901overlay is mapped. This allows most @value{GDBN} commands, like
6902@code{break} and @code{disassemble}, to work normally, even on unmapped
6903code. However, @value{GDBN}'s breakpoint support has some limitations:
6904
6905@itemize @bullet
6906@item
6907@cindex breakpoints in overlays
6908@cindex overlays, setting breakpoints in
6909You can set breakpoints in functions in unmapped overlays, as long as
6910@value{GDBN} can write to the overlay at its load address.
6911@item
6912@value{GDBN} can not set hardware or simulator-based breakpoints in
6913unmapped overlays. However, if you set a breakpoint at the end of your
6914overlay manager (and tell @value{GDBN} which overlays are now mapped, if
6915you are using manual overlay management), @value{GDBN} will re-set its
6916breakpoints properly.
6917@end itemize
6918
6919
6920@node Automatic Overlay Debugging
6921@section Automatic Overlay Debugging
6922@cindex automatic overlay debugging
6923
6924@value{GDBN} can automatically track which overlays are mapped and which
6925are not, given some simple co-operation from the overlay manager in the
6926inferior. If you enable automatic overlay debugging with the
6927@code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
6928looks in the inferior's memory for certain variables describing the
6929current state of the overlays.
6930
6931Here are the variables your overlay manager must define to support
6932@value{GDBN}'s automatic overlay debugging:
6933
6934@table @asis
6935
6936@item @code{_ovly_table}:
6937This variable must be an array of the following structures:
6938
474c8240 6939@smallexample
df0cd8c5
JB
6940struct
6941@{
6942 /* The overlay's mapped address. */
6943 unsigned long vma;
6944
6945 /* The size of the overlay, in bytes. */
6946 unsigned long size;
6947
6948 /* The overlay's load address. */
6949 unsigned long lma;
6950
6951 /* Non-zero if the overlay is currently mapped;
6952 zero otherwise. */
6953 unsigned long mapped;
6954@}
474c8240 6955@end smallexample
df0cd8c5
JB
6956
6957@item @code{_novlys}:
6958This variable must be a four-byte signed integer, holding the total
6959number of elements in @code{_ovly_table}.
6960
6961@end table
6962
6963To decide whether a particular overlay is mapped or not, @value{GDBN}
6964looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
6965@code{lma} members equal the VMA and LMA of the overlay's section in the
6966executable file. When @value{GDBN} finds a matching entry, it consults
6967the entry's @code{mapped} member to determine whether the overlay is
6968currently mapped.
6969
81d46470 6970In addition, your overlay manager may define a function called
def71bfa 6971@code{_ovly_debug_event}. If this function is defined, @value{GDBN}
81d46470
MS
6972will silently set a breakpoint there. If the overlay manager then
6973calls this function whenever it has changed the overlay table, this
6974will enable @value{GDBN} to accurately keep track of which overlays
6975are in program memory, and update any breakpoints that may be set
6976in overlays. This will allow breakpoints to work even if the
6977overlays are kept in ROM or other non-writable memory while they
6978are not being executed.
df0cd8c5
JB
6979
6980@node Overlay Sample Program
6981@section Overlay Sample Program
6982@cindex overlay example program
6983
6984When linking a program which uses overlays, you must place the overlays
6985at their load addresses, while relocating them to run at their mapped
6986addresses. To do this, you must write a linker script (@pxref{Overlay
6987Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
6988since linker scripts are specific to a particular host system, target
6989architecture, and target memory layout, this manual cannot provide
6990portable sample code demonstrating @value{GDBN}'s overlay support.
6991
6992However, the @value{GDBN} source distribution does contain an overlaid
6993program, with linker scripts for a few systems, as part of its test
6994suite. The program consists of the following files from
6995@file{gdb/testsuite/gdb.base}:
6996
6997@table @file
6998@item overlays.c
6999The main program file.
7000@item ovlymgr.c
7001A simple overlay manager, used by @file{overlays.c}.
7002@item foo.c
7003@itemx bar.c
7004@itemx baz.c
7005@itemx grbx.c
7006Overlay modules, loaded and used by @file{overlays.c}.
7007@item d10v.ld
7008@itemx m32r.ld
7009Linker scripts for linking the test program on the @code{d10v-elf}
7010and @code{m32r-elf} targets.
7011@end table
7012
7013You can build the test program using the @code{d10v-elf} GCC
7014cross-compiler like this:
7015
474c8240 7016@smallexample
df0cd8c5
JB
7017$ d10v-elf-gcc -g -c overlays.c
7018$ d10v-elf-gcc -g -c ovlymgr.c
7019$ d10v-elf-gcc -g -c foo.c
7020$ d10v-elf-gcc -g -c bar.c
7021$ d10v-elf-gcc -g -c baz.c
7022$ d10v-elf-gcc -g -c grbx.c
7023$ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7024 baz.o grbx.o -Wl,-Td10v.ld -o overlays
474c8240 7025@end smallexample
df0cd8c5
JB
7026
7027The build process is identical for any other architecture, except that
7028you must substitute the appropriate compiler and linker script for the
7029target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7030
7031
6d2ebf8b 7032@node Languages
c906108c
SS
7033@chapter Using @value{GDBN} with Different Languages
7034@cindex languages
7035
c906108c
SS
7036Although programming languages generally have common aspects, they are
7037rarely expressed in the same manner. For instance, in ANSI C,
7038dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7039Modula-2, it is accomplished by @code{p^}. Values can also be
5d161b24 7040represented (and displayed) differently. Hex numbers in C appear as
c906108c 7041@samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
c906108c
SS
7042
7043@cindex working language
7044Language-specific information is built into @value{GDBN} for some languages,
7045allowing you to express operations like the above in your program's
7046native language, and allowing @value{GDBN} to output values in a manner
7047consistent with the syntax of your program's native language. The
7048language you use to build expressions is called the @dfn{working
7049language}.
7050
7051@menu
7052* Setting:: Switching between source languages
7053* Show:: Displaying the language
c906108c 7054* Checks:: Type and range checks
c906108c
SS
7055* Support:: Supported languages
7056@end menu
7057
6d2ebf8b 7058@node Setting
c906108c
SS
7059@section Switching between source languages
7060
7061There are two ways to control the working language---either have @value{GDBN}
7062set it automatically, or select it manually yourself. You can use the
7063@code{set language} command for either purpose. On startup, @value{GDBN}
7064defaults to setting the language automatically. The working language is
7065used to determine how expressions you type are interpreted, how values
7066are printed, etc.
7067
7068In addition to the working language, every source file that
7069@value{GDBN} knows about has its own working language. For some object
7070file formats, the compiler might indicate which language a particular
7071source file is in. However, most of the time @value{GDBN} infers the
7072language from the name of the file. The language of a source file
b37052ae 7073controls whether C@t{++} names are demangled---this way @code{backtrace} can
c906108c 7074show each frame appropriately for its own language. There is no way to
d4f3574e
SS
7075set the language of a source file from within @value{GDBN}, but you can
7076set the language associated with a filename extension. @xref{Show, ,
7077Displaying the language}.
c906108c
SS
7078
7079This is most commonly a problem when you use a program, such
5d161b24 7080as @code{cfront} or @code{f2c}, that generates C but is written in
c906108c
SS
7081another language. In that case, make the
7082program use @code{#line} directives in its C output; that way
7083@value{GDBN} will know the correct language of the source code of the original
7084program, and will display that source code, not the generated C code.
7085
7086@menu
7087* Filenames:: Filename extensions and languages.
7088* Manually:: Setting the working language manually
7089* Automatically:: Having @value{GDBN} infer the source language
7090@end menu
7091
6d2ebf8b 7092@node Filenames
c906108c
SS
7093@subsection List of filename extensions and languages
7094
7095If a source file name ends in one of the following extensions, then
7096@value{GDBN} infers that its language is the one indicated.
7097
7098@table @file
7099
7100@item .c
7101C source file
7102
7103@item .C
7104@itemx .cc
7105@itemx .cp
7106@itemx .cpp
7107@itemx .cxx
7108@itemx .c++
b37052ae 7109C@t{++} source file
c906108c
SS
7110
7111@item .f
7112@itemx .F
7113Fortran source file
7114
c906108c
SS
7115@item .ch
7116@itemx .c186
7117@itemx .c286
96a2c332 7118CHILL source file
c906108c 7119
c906108c
SS
7120@item .mod
7121Modula-2 source file
c906108c
SS
7122
7123@item .s
7124@itemx .S
7125Assembler source file. This actually behaves almost like C, but
7126@value{GDBN} does not skip over function prologues when stepping.
7127@end table
7128
7129In addition, you may set the language associated with a filename
7130extension. @xref{Show, , Displaying the language}.
7131
6d2ebf8b 7132@node Manually
c906108c
SS
7133@subsection Setting the working language
7134
7135If you allow @value{GDBN} to set the language automatically,
7136expressions are interpreted the same way in your debugging session and
7137your program.
7138
7139@kindex set language
7140If you wish, you may set the language manually. To do this, issue the
7141command @samp{set language @var{lang}}, where @var{lang} is the name of
5d161b24 7142a language, such as
c906108c 7143@code{c} or @code{modula-2}.
c906108c
SS
7144For a list of the supported languages, type @samp{set language}.
7145
c906108c
SS
7146Setting the language manually prevents @value{GDBN} from updating the working
7147language automatically. This can lead to confusion if you try
7148to debug a program when the working language is not the same as the
7149source language, when an expression is acceptable to both
7150languages---but means different things. For instance, if the current
7151source file were written in C, and @value{GDBN} was parsing Modula-2, a
7152command such as:
7153
474c8240 7154@smallexample
c906108c 7155print a = b + c
474c8240 7156@end smallexample
c906108c
SS
7157
7158@noindent
7159might not have the effect you intended. In C, this means to add
7160@code{b} and @code{c} and place the result in @code{a}. The result
7161printed would be the value of @code{a}. In Modula-2, this means to compare
7162@code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
c906108c 7163
6d2ebf8b 7164@node Automatically
c906108c
SS
7165@subsection Having @value{GDBN} infer the source language
7166
7167To have @value{GDBN} set the working language automatically, use
7168@samp{set language local} or @samp{set language auto}. @value{GDBN}
7169then infers the working language. That is, when your program stops in a
7170frame (usually by encountering a breakpoint), @value{GDBN} sets the
7171working language to the language recorded for the function in that
7172frame. If the language for a frame is unknown (that is, if the function
7173or block corresponding to the frame was defined in a source file that
7174does not have a recognized extension), the current working language is
7175not changed, and @value{GDBN} issues a warning.
7176
7177This may not seem necessary for most programs, which are written
7178entirely in one source language. However, program modules and libraries
7179written in one source language can be used by a main program written in
7180a different source language. Using @samp{set language auto} in this
7181case frees you from having to set the working language manually.
7182
6d2ebf8b 7183@node Show
c906108c 7184@section Displaying the language
c906108c
SS
7185
7186The following commands help you find out which language is the
7187working language, and also what language source files were written in.
7188
7189@kindex show language
d4f3574e
SS
7190@kindex info frame@r{, show the source language}
7191@kindex info source@r{, show the source language}
c906108c
SS
7192@table @code
7193@item show language
7194Display the current working language. This is the
7195language you can use with commands such as @code{print} to
7196build and compute expressions that may involve variables in your program.
7197
7198@item info frame
5d161b24 7199Display the source language for this frame. This language becomes the
c906108c 7200working language if you use an identifier from this frame.
5d161b24 7201@xref{Frame Info, ,Information about a frame}, to identify the other
c906108c
SS
7202information listed here.
7203
7204@item info source
7205Display the source language of this source file.
5d161b24 7206@xref{Symbols, ,Examining the Symbol Table}, to identify the other
c906108c
SS
7207information listed here.
7208@end table
7209
7210In unusual circumstances, you may have source files with extensions
7211not in the standard list. You can then set the extension associated
7212with a language explicitly:
7213
7214@kindex set extension-language
7215@kindex info extensions
7216@table @code
7217@item set extension-language @var{.ext} @var{language}
7218Set source files with extension @var{.ext} to be assumed to be in
7219the source language @var{language}.
7220
7221@item info extensions
7222List all the filename extensions and the associated languages.
7223@end table
7224
6d2ebf8b 7225@node Checks
c906108c
SS
7226@section Type and range checking
7227
7228@quotation
7229@emph{Warning:} In this release, the @value{GDBN} commands for type and range
7230checking are included, but they do not yet have any effect. This
7231section documents the intended facilities.
7232@end quotation
7233@c FIXME remove warning when type/range code added
7234
7235Some languages are designed to guard you against making seemingly common
7236errors through a series of compile- and run-time checks. These include
7237checking the type of arguments to functions and operators, and making
7238sure mathematical overflows are caught at run time. Checks such as
7239these help to ensure a program's correctness once it has been compiled
7240by eliminating type mismatches, and providing active checks for range
7241errors when your program is running.
7242
7243@value{GDBN} can check for conditions like the above if you wish.
7244Although @value{GDBN} does not check the statements in your program, it
7245can check expressions entered directly into @value{GDBN} for evaluation via
7246the @code{print} command, for example. As with the working language,
7247@value{GDBN} can also decide whether or not to check automatically based on
7248your program's source language. @xref{Support, ,Supported languages},
7249for the default settings of supported languages.
7250
7251@menu
7252* Type Checking:: An overview of type checking
7253* Range Checking:: An overview of range checking
7254@end menu
7255
7256@cindex type checking
7257@cindex checks, type
6d2ebf8b 7258@node Type Checking
c906108c
SS
7259@subsection An overview of type checking
7260
7261Some languages, such as Modula-2, are strongly typed, meaning that the
7262arguments to operators and functions have to be of the correct type,
7263otherwise an error occurs. These checks prevent type mismatch
7264errors from ever causing any run-time problems. For example,
7265
7266@smallexample
72671 + 2 @result{} 3
7268@exdent but
7269@error{} 1 + 2.3
7270@end smallexample
7271
7272The second example fails because the @code{CARDINAL} 1 is not
7273type-compatible with the @code{REAL} 2.3.
7274
5d161b24
DB
7275For the expressions you use in @value{GDBN} commands, you can tell the
7276@value{GDBN} type checker to skip checking;
7277to treat any mismatches as errors and abandon the expression;
7278or to only issue warnings when type mismatches occur,
c906108c
SS
7279but evaluate the expression anyway. When you choose the last of
7280these, @value{GDBN} evaluates expressions like the second example above, but
7281also issues a warning.
7282
5d161b24
DB
7283Even if you turn type checking off, there may be other reasons
7284related to type that prevent @value{GDBN} from evaluating an expression.
7285For instance, @value{GDBN} does not know how to add an @code{int} and
7286a @code{struct foo}. These particular type errors have nothing to do
7287with the language in use, and usually arise from expressions, such as
c906108c
SS
7288the one described above, which make little sense to evaluate anyway.
7289
7290Each language defines to what degree it is strict about type. For
7291instance, both Modula-2 and C require the arguments to arithmetical
7292operators to be numbers. In C, enumerated types and pointers can be
7293represented as numbers, so that they are valid arguments to mathematical
7294operators. @xref{Support, ,Supported languages}, for further
7295details on specific languages.
7296
7297@value{GDBN} provides some additional commands for controlling the type checker:
7298
d4f3574e 7299@kindex set check@r{, type}
c906108c
SS
7300@kindex set check type
7301@kindex show check type
7302@table @code
7303@item set check type auto
7304Set type checking on or off based on the current working language.
7305@xref{Support, ,Supported languages}, for the default settings for
7306each language.
7307
7308@item set check type on
7309@itemx set check type off
7310Set type checking on or off, overriding the default setting for the
7311current working language. Issue a warning if the setting does not
7312match the language default. If any type mismatches occur in
d4f3574e 7313evaluating an expression while type checking is on, @value{GDBN} prints a
c906108c
SS
7314message and aborts evaluation of the expression.
7315
7316@item set check type warn
7317Cause the type checker to issue warnings, but to always attempt to
7318evaluate the expression. Evaluating the expression may still
7319be impossible for other reasons. For example, @value{GDBN} cannot add
7320numbers and structures.
7321
7322@item show type
5d161b24 7323Show the current setting of the type checker, and whether or not @value{GDBN}
c906108c
SS
7324is setting it automatically.
7325@end table
7326
7327@cindex range checking
7328@cindex checks, range
6d2ebf8b 7329@node Range Checking
c906108c
SS
7330@subsection An overview of range checking
7331
7332In some languages (such as Modula-2), it is an error to exceed the
7333bounds of a type; this is enforced with run-time checks. Such range
7334checking is meant to ensure program correctness by making sure
7335computations do not overflow, or indices on an array element access do
7336not exceed the bounds of the array.
7337
7338For expressions you use in @value{GDBN} commands, you can tell
7339@value{GDBN} to treat range errors in one of three ways: ignore them,
7340always treat them as errors and abandon the expression, or issue
7341warnings but evaluate the expression anyway.
7342
7343A range error can result from numerical overflow, from exceeding an
7344array index bound, or when you type a constant that is not a member
7345of any type. Some languages, however, do not treat overflows as an
7346error. In many implementations of C, mathematical overflow causes the
7347result to ``wrap around'' to lower values---for example, if @var{m} is
7348the largest integer value, and @var{s} is the smallest, then
7349
474c8240 7350@smallexample
c906108c 7351@var{m} + 1 @result{} @var{s}
474c8240 7352@end smallexample
c906108c
SS
7353
7354This, too, is specific to individual languages, and in some cases
7355specific to individual compilers or machines. @xref{Support, ,
7356Supported languages}, for further details on specific languages.
7357
7358@value{GDBN} provides some additional commands for controlling the range checker:
7359
d4f3574e 7360@kindex set check@r{, range}
c906108c
SS
7361@kindex set check range
7362@kindex show check range
7363@table @code
7364@item set check range auto
7365Set range checking on or off based on the current working language.
7366@xref{Support, ,Supported languages}, for the default settings for
7367each language.
7368
7369@item set check range on
7370@itemx set check range off
7371Set range checking on or off, overriding the default setting for the
7372current working language. A warning is issued if the setting does not
c3f6f71d
JM
7373match the language default. If a range error occurs and range checking is on,
7374then a message is printed and evaluation of the expression is aborted.
c906108c
SS
7375
7376@item set check range warn
7377Output messages when the @value{GDBN} range checker detects a range error,
7378but attempt to evaluate the expression anyway. Evaluating the
7379expression may still be impossible for other reasons, such as accessing
7380memory that the process does not own (a typical example from many Unix
7381systems).
7382
7383@item show range
7384Show the current setting of the range checker, and whether or not it is
7385being set automatically by @value{GDBN}.
7386@end table
c906108c 7387
6d2ebf8b 7388@node Support
c906108c 7389@section Supported languages
c906108c 7390
b37052ae 7391@value{GDBN} supports C, C@t{++}, Fortran, Java, Chill, assembly, and Modula-2.
cce74817 7392@c This is false ...
c906108c
SS
7393Some @value{GDBN} features may be used in expressions regardless of the
7394language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7395and the @samp{@{type@}addr} construct (@pxref{Expressions,
7396,Expressions}) can be used with the constructs of any supported
7397language.
7398
7399The following sections detail to what degree each source language is
7400supported by @value{GDBN}. These sections are not meant to be language
7401tutorials or references, but serve only as a reference guide to what the
7402@value{GDBN} expression parser accepts, and what input and output
7403formats should look like for different languages. There are many good
7404books written on each of these languages; please look to these for a
7405language reference or tutorial.
7406
c906108c 7407@menu
b37052ae 7408* C:: C and C@t{++}
cce74817 7409* Modula-2:: Modula-2
104c1213 7410* Chill:: Chill
c906108c
SS
7411@end menu
7412
6d2ebf8b 7413@node C
b37052ae 7414@subsection C and C@t{++}
7a292a7a 7415
b37052ae
EZ
7416@cindex C and C@t{++}
7417@cindex expressions in C or C@t{++}
c906108c 7418
b37052ae 7419Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
c906108c
SS
7420to both languages. Whenever this is the case, we discuss those languages
7421together.
7422
41afff9a
EZ
7423@cindex C@t{++}
7424@cindex @code{g++}, @sc{gnu} C@t{++} compiler
b37052ae
EZ
7425@cindex @sc{gnu} C@t{++}
7426The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7427compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7428effectively, you must compile your C@t{++} programs with a supported
7429C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
c906108c
SS
7430compiler (@code{aCC}).
7431
b37052ae 7432For best results when using @sc{gnu} C@t{++}, use the stabs debugging
c906108c
SS
7433format. You can select that format explicitly with the @code{g++}
7434command-line options @samp{-gstabs} or @samp{-gstabs+}. See
7435@ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7436CC, gcc.info, Using @sc{gnu} CC}, for more information.
c906108c 7437
c906108c 7438@menu
b37052ae
EZ
7439* C Operators:: C and C@t{++} operators
7440* C Constants:: C and C@t{++} constants
7441* C plus plus expressions:: C@t{++} expressions
7442* C Defaults:: Default settings for C and C@t{++}
7443* C Checks:: C and C@t{++} type and range checks
c906108c 7444* Debugging C:: @value{GDBN} and C
b37052ae 7445* Debugging C plus plus:: @value{GDBN} features for C@t{++}
c906108c 7446@end menu
c906108c 7447
6d2ebf8b 7448@node C Operators
b37052ae 7449@subsubsection C and C@t{++} operators
7a292a7a 7450
b37052ae 7451@cindex C and C@t{++} operators
c906108c
SS
7452
7453Operators must be defined on values of specific types. For instance,
7454@code{+} is defined on numbers, but not on structures. Operators are
5d161b24 7455often defined on groups of types.
c906108c 7456
b37052ae 7457For the purposes of C and C@t{++}, the following definitions hold:
c906108c
SS
7458
7459@itemize @bullet
53a5351d 7460
c906108c 7461@item
c906108c 7462@emph{Integral types} include @code{int} with any of its storage-class
b37052ae 7463specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
c906108c
SS
7464
7465@item
d4f3574e
SS
7466@emph{Floating-point types} include @code{float}, @code{double}, and
7467@code{long double} (if supported by the target platform).
c906108c
SS
7468
7469@item
53a5351d 7470@emph{Pointer types} include all types defined as @code{(@var{type} *)}.
c906108c
SS
7471
7472@item
7473@emph{Scalar types} include all of the above.
53a5351d 7474
c906108c
SS
7475@end itemize
7476
7477@noindent
7478The following operators are supported. They are listed here
7479in order of increasing precedence:
7480
7481@table @code
7482@item ,
7483The comma or sequencing operator. Expressions in a comma-separated list
7484are evaluated from left to right, with the result of the entire
7485expression being the last expression evaluated.
7486
7487@item =
7488Assignment. The value of an assignment expression is the value
7489assigned. Defined on scalar types.
7490
7491@item @var{op}=
7492Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7493and translated to @w{@code{@var{a} = @var{a op b}}}.
d4f3574e 7494@w{@code{@var{op}=}} and @code{=} have the same precedence.
c906108c
SS
7495@var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7496@code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7497
7498@item ?:
7499The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7500of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7501integral type.
7502
7503@item ||
7504Logical @sc{or}. Defined on integral types.
7505
7506@item &&
7507Logical @sc{and}. Defined on integral types.
7508
7509@item |
7510Bitwise @sc{or}. Defined on integral types.
7511
7512@item ^
7513Bitwise exclusive-@sc{or}. Defined on integral types.
7514
7515@item &
7516Bitwise @sc{and}. Defined on integral types.
7517
7518@item ==@r{, }!=
7519Equality and inequality. Defined on scalar types. The value of these
7520expressions is 0 for false and non-zero for true.
7521
7522@item <@r{, }>@r{, }<=@r{, }>=
7523Less than, greater than, less than or equal, greater than or equal.
7524Defined on scalar types. The value of these expressions is 0 for false
7525and non-zero for true.
7526
7527@item <<@r{, }>>
7528left shift, and right shift. Defined on integral types.
7529
7530@item @@
7531The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7532
7533@item +@r{, }-
7534Addition and subtraction. Defined on integral types, floating-point types and
7535pointer types.
7536
7537@item *@r{, }/@r{, }%
7538Multiplication, division, and modulus. Multiplication and division are
7539defined on integral and floating-point types. Modulus is defined on
7540integral types.
7541
7542@item ++@r{, }--
7543Increment and decrement. When appearing before a variable, the
7544operation is performed before the variable is used in an expression;
7545when appearing after it, the variable's value is used before the
7546operation takes place.
7547
7548@item *
7549Pointer dereferencing. Defined on pointer types. Same precedence as
7550@code{++}.
7551
7552@item &
7553Address operator. Defined on variables. Same precedence as @code{++}.
7554
b37052ae
EZ
7555For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7556allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
c906108c 7557(or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
b37052ae 7558where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
c906108c 7559stored.
c906108c
SS
7560
7561@item -
7562Negative. Defined on integral and floating-point types. Same
7563precedence as @code{++}.
7564
7565@item !
7566Logical negation. Defined on integral types. Same precedence as
7567@code{++}.
7568
7569@item ~
7570Bitwise complement operator. Defined on integral types. Same precedence as
7571@code{++}.
7572
7573
7574@item .@r{, }->
7575Structure member, and pointer-to-structure member. For convenience,
7576@value{GDBN} regards the two as equivalent, choosing whether to dereference a
7577pointer based on the stored type information.
7578Defined on @code{struct} and @code{union} data.
7579
c906108c
SS
7580@item .*@r{, }->*
7581Dereferences of pointers to members.
c906108c
SS
7582
7583@item []
7584Array indexing. @code{@var{a}[@var{i}]} is defined as
7585@code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7586
7587@item ()
7588Function parameter list. Same precedence as @code{->}.
7589
c906108c 7590@item ::
b37052ae 7591C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7a292a7a 7592and @code{class} types.
c906108c
SS
7593
7594@item ::
7a292a7a
SS
7595Doubled colons also represent the @value{GDBN} scope operator
7596(@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7597above.
c906108c
SS
7598@end table
7599
c906108c
SS
7600If an operator is redefined in the user code, @value{GDBN} usually
7601attempts to invoke the redefined version instead of using the operator's
7602predefined meaning.
c906108c 7603
c906108c 7604@menu
5d161b24 7605* C Constants::
c906108c
SS
7606@end menu
7607
6d2ebf8b 7608@node C Constants
b37052ae 7609@subsubsection C and C@t{++} constants
c906108c 7610
b37052ae 7611@cindex C and C@t{++} constants
c906108c 7612
b37052ae 7613@value{GDBN} allows you to express the constants of C and C@t{++} in the
c906108c 7614following ways:
c906108c
SS
7615
7616@itemize @bullet
7617@item
7618Integer constants are a sequence of digits. Octal constants are
6ca652b0
EZ
7619specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
7620by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
c906108c
SS
7621@samp{l}, specifying that the constant should be treated as a
7622@code{long} value.
7623
7624@item
7625Floating point constants are a sequence of digits, followed by a decimal
7626point, followed by a sequence of digits, and optionally followed by an
7627exponent. An exponent is of the form:
7628@samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
7629sequence of digits. The @samp{+} is optional for positive exponents.
d4f3574e
SS
7630A floating-point constant may also end with a letter @samp{f} or
7631@samp{F}, specifying that the constant should be treated as being of
7632the @code{float} (as opposed to the default @code{double}) type; or with
7633a letter @samp{l} or @samp{L}, which specifies a @code{long double}
7634constant.
c906108c
SS
7635
7636@item
7637Enumerated constants consist of enumerated identifiers, or their
7638integral equivalents.
7639
7640@item
7641Character constants are a single character surrounded by single quotes
7642(@code{'}), or a number---the ordinal value of the corresponding character
d4f3574e 7643(usually its @sc{ascii} value). Within quotes, the single character may
c906108c
SS
7644be represented by a letter or by @dfn{escape sequences}, which are of
7645the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
7646of the character's ordinal value; or of the form @samp{\@var{x}}, where
7647@samp{@var{x}} is a predefined special character---for example,
7648@samp{\n} for newline.
7649
7650@item
96a2c332
SS
7651String constants are a sequence of character constants surrounded by
7652double quotes (@code{"}). Any valid character constant (as described
7653above) may appear. Double quotes within the string must be preceded by
7654a backslash, so for instance @samp{"a\"b'c"} is a string of five
7655characters.
c906108c
SS
7656
7657@item
7658Pointer constants are an integral value. You can also write pointers
7659to constants using the C operator @samp{&}.
7660
7661@item
7662Array constants are comma-separated lists surrounded by braces @samp{@{}
7663and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
7664integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
7665and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
7666@end itemize
7667
c906108c 7668@menu
5d161b24
DB
7669* C plus plus expressions::
7670* C Defaults::
7671* C Checks::
c906108c 7672
5d161b24 7673* Debugging C::
c906108c
SS
7674@end menu
7675
6d2ebf8b 7676@node C plus plus expressions
b37052ae
EZ
7677@subsubsection C@t{++} expressions
7678
7679@cindex expressions in C@t{++}
7680@value{GDBN} expression handling can interpret most C@t{++} expressions.
7681
7682@cindex C@t{++} support, not in @sc{coff}
7683@cindex @sc{coff} versus C@t{++}
7684@cindex C@t{++} and object formats
7685@cindex object formats and C@t{++}
7686@cindex a.out and C@t{++}
7687@cindex @sc{ecoff} and C@t{++}
7688@cindex @sc{xcoff} and C@t{++}
7689@cindex @sc{elf}/stabs and C@t{++}
7690@cindex @sc{elf}/@sc{dwarf} and C@t{++}
c906108c
SS
7691@c FIXME!! GDB may eventually be able to debug C++ using DWARF; check
7692@c periodically whether this has happened...
7693@quotation
b37052ae
EZ
7694@emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
7695proper compiler. Typically, C@t{++} debugging depends on the use of
c906108c
SS
7696additional debugging information in the symbol table, and thus requires
7697special support. In particular, if your compiler generates a.out, MIPS
7698@sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the
7699symbol table, these facilities are all available. (With @sc{gnu} CC,
7700you can use the @samp{-gstabs} option to request stabs debugging
7701extensions explicitly.) Where the object code format is standard
b37052ae 7702@sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C@t{++}
c906108c
SS
7703support in @value{GDBN} does @emph{not} work.
7704@end quotation
c906108c
SS
7705
7706@enumerate
7707
7708@cindex member functions
7709@item
7710Member function calls are allowed; you can use expressions like
7711
474c8240 7712@smallexample
c906108c 7713count = aml->GetOriginal(x, y)
474c8240 7714@end smallexample
c906108c 7715
41afff9a 7716@vindex this@r{, inside C@t{++} member functions}
b37052ae 7717@cindex namespace in C@t{++}
c906108c
SS
7718@item
7719While a member function is active (in the selected stack frame), your
7720expressions have the same namespace available as the member function;
7721that is, @value{GDBN} allows implicit references to the class instance
b37052ae 7722pointer @code{this} following the same rules as C@t{++}.
c906108c 7723
c906108c 7724@cindex call overloaded functions
d4f3574e 7725@cindex overloaded functions, calling
b37052ae 7726@cindex type conversions in C@t{++}
c906108c
SS
7727@item
7728You can call overloaded functions; @value{GDBN} resolves the function
d4f3574e 7729call to the right definition, with some restrictions. @value{GDBN} does not
c906108c
SS
7730perform overload resolution involving user-defined type conversions,
7731calls to constructors, or instantiations of templates that do not exist
7732in the program. It also cannot handle ellipsis argument lists or
7733default arguments.
7734
7735It does perform integral conversions and promotions, floating-point
7736promotions, arithmetic conversions, pointer conversions, conversions of
7737class objects to base classes, and standard conversions such as those of
7738functions or arrays to pointers; it requires an exact match on the
7739number of function arguments.
7740
7741Overload resolution is always performed, unless you have specified
7742@code{set overload-resolution off}. @xref{Debugging C plus plus,
b37052ae 7743,@value{GDBN} features for C@t{++}}.
c906108c 7744
d4f3574e 7745You must specify @code{set overload-resolution off} in order to use an
c906108c
SS
7746explicit function signature to call an overloaded function, as in
7747@smallexample
7748p 'foo(char,int)'('x', 13)
7749@end smallexample
d4f3574e 7750
c906108c 7751The @value{GDBN} command-completion facility can simplify this;
d4f3574e 7752see @ref{Completion, ,Command completion}.
c906108c 7753
c906108c
SS
7754@cindex reference declarations
7755@item
b37052ae
EZ
7756@value{GDBN} understands variables declared as C@t{++} references; you can use
7757them in expressions just as you do in C@t{++} source---they are automatically
c906108c
SS
7758dereferenced.
7759
7760In the parameter list shown when @value{GDBN} displays a frame, the values of
7761reference variables are not displayed (unlike other variables); this
7762avoids clutter, since references are often used for large structures.
7763The @emph{address} of a reference variable is always shown, unless
7764you have specified @samp{set print address off}.
7765
7766@item
b37052ae 7767@value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
c906108c
SS
7768expressions can use it just as expressions in your program do. Since
7769one scope may be defined in another, you can use @code{::} repeatedly if
7770necessary, for example in an expression like
7771@samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
b37052ae 7772resolving name scope by reference to source files, in both C and C@t{++}
c906108c
SS
7773debugging (@pxref{Variables, ,Program variables}).
7774@end enumerate
7775
b37052ae 7776In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
53a5351d
JM
7777calling virtual functions correctly, printing out virtual bases of
7778objects, calling functions in a base subobject, casting objects, and
7779invoking user-defined operators.
c906108c 7780
6d2ebf8b 7781@node C Defaults
b37052ae 7782@subsubsection C and C@t{++} defaults
7a292a7a 7783
b37052ae 7784@cindex C and C@t{++} defaults
c906108c 7785
c906108c
SS
7786If you allow @value{GDBN} to set type and range checking automatically, they
7787both default to @code{off} whenever the working language changes to
b37052ae 7788C or C@t{++}. This happens regardless of whether you or @value{GDBN}
c906108c 7789selects the working language.
c906108c
SS
7790
7791If you allow @value{GDBN} to set the language automatically, it
7792recognizes source files whose names end with @file{.c}, @file{.C}, or
7793@file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
b37052ae 7794these files, it sets the working language to C or C@t{++}.
c906108c
SS
7795@xref{Automatically, ,Having @value{GDBN} infer the source language},
7796for further details.
7797
c906108c
SS
7798@c Type checking is (a) primarily motivated by Modula-2, and (b)
7799@c unimplemented. If (b) changes, it might make sense to let this node
7800@c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
7a292a7a 7801
6d2ebf8b 7802@node C Checks
b37052ae 7803@subsubsection C and C@t{++} type and range checks
7a292a7a 7804
b37052ae 7805@cindex C and C@t{++} checks
c906108c 7806
b37052ae 7807By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
c906108c
SS
7808is not used. However, if you turn type checking on, @value{GDBN}
7809considers two variables type equivalent if:
7810
7811@itemize @bullet
7812@item
7813The two variables are structured and have the same structure, union, or
7814enumerated tag.
7815
7816@item
7817The two variables have the same type name, or types that have been
7818declared equivalent through @code{typedef}.
7819
7820@ignore
7821@c leaving this out because neither J Gilmore nor R Pesch understand it.
7822@c FIXME--beers?
7823@item
7824The two @code{struct}, @code{union}, or @code{enum} variables are
7825declared in the same declaration. (Note: this may not be true for all C
7826compilers.)
7827@end ignore
7828@end itemize
7829
7830Range checking, if turned on, is done on mathematical operations. Array
7831indices are not checked, since they are often used to index a pointer
7832that is not itself an array.
c906108c 7833
6d2ebf8b 7834@node Debugging C
c906108c 7835@subsubsection @value{GDBN} and C
c906108c
SS
7836
7837The @code{set print union} and @code{show print union} commands apply to
7838the @code{union} type. When set to @samp{on}, any @code{union} that is
7a292a7a
SS
7839inside a @code{struct} or @code{class} is also printed. Otherwise, it
7840appears as @samp{@{...@}}.
c906108c
SS
7841
7842The @code{@@} operator aids in the debugging of dynamic arrays, formed
7843with pointers and a memory allocation function. @xref{Expressions,
7844,Expressions}.
7845
c906108c 7846@menu
5d161b24 7847* Debugging C plus plus::
c906108c
SS
7848@end menu
7849
6d2ebf8b 7850@node Debugging C plus plus
b37052ae 7851@subsubsection @value{GDBN} features for C@t{++}
c906108c 7852
b37052ae 7853@cindex commands for C@t{++}
7a292a7a 7854
b37052ae
EZ
7855Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
7856designed specifically for use with C@t{++}. Here is a summary:
c906108c
SS
7857
7858@table @code
7859@cindex break in overloaded functions
7860@item @r{breakpoint menus}
7861When you want a breakpoint in a function whose name is overloaded,
7862@value{GDBN} breakpoint menus help you specify which function definition
7863you want. @xref{Breakpoint Menus,,Breakpoint menus}.
7864
b37052ae 7865@cindex overloading in C@t{++}
c906108c
SS
7866@item rbreak @var{regex}
7867Setting breakpoints using regular expressions is helpful for setting
7868breakpoints on overloaded functions that are not members of any special
7869classes.
7870@xref{Set Breaks, ,Setting breakpoints}.
7871
b37052ae 7872@cindex C@t{++} exception handling
c906108c
SS
7873@item catch throw
7874@itemx catch catch
b37052ae 7875Debug C@t{++} exception handling using these commands. @xref{Set
c906108c
SS
7876Catchpoints, , Setting catchpoints}.
7877
7878@cindex inheritance
7879@item ptype @var{typename}
7880Print inheritance relationships as well as other information for type
7881@var{typename}.
7882@xref{Symbols, ,Examining the Symbol Table}.
7883
b37052ae 7884@cindex C@t{++} symbol display
c906108c
SS
7885@item set print demangle
7886@itemx show print demangle
7887@itemx set print asm-demangle
7888@itemx show print asm-demangle
b37052ae
EZ
7889Control whether C@t{++} symbols display in their source form, both when
7890displaying code as C@t{++} source and when displaying disassemblies.
c906108c
SS
7891@xref{Print Settings, ,Print settings}.
7892
7893@item set print object
7894@itemx show print object
7895Choose whether to print derived (actual) or declared types of objects.
7896@xref{Print Settings, ,Print settings}.
7897
7898@item set print vtbl
7899@itemx show print vtbl
7900Control the format for printing virtual function tables.
7901@xref{Print Settings, ,Print settings}.
c906108c 7902(The @code{vtbl} commands do not work on programs compiled with the HP
b37052ae 7903ANSI C@t{++} compiler (@code{aCC}).)
c906108c
SS
7904
7905@kindex set overload-resolution
d4f3574e 7906@cindex overloaded functions, overload resolution
c906108c 7907@item set overload-resolution on
b37052ae 7908Enable overload resolution for C@t{++} expression evaluation. The default
c906108c
SS
7909is on. For overloaded functions, @value{GDBN} evaluates the arguments
7910and searches for a function whose signature matches the argument types,
b37052ae 7911using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
d4f3574e 7912expressions}, for details). If it cannot find a match, it emits a
c906108c
SS
7913message.
7914
7915@item set overload-resolution off
b37052ae 7916Disable overload resolution for C@t{++} expression evaluation. For
c906108c
SS
7917overloaded functions that are not class member functions, @value{GDBN}
7918chooses the first function of the specified name that it finds in the
7919symbol table, whether or not its arguments are of the correct type. For
7920overloaded functions that are class member functions, @value{GDBN}
7921searches for a function whose signature @emph{exactly} matches the
7922argument types.
c906108c
SS
7923
7924@item @r{Overloaded symbol names}
7925You can specify a particular definition of an overloaded symbol, using
b37052ae 7926the same notation that is used to declare such symbols in C@t{++}: type
c906108c
SS
7927@code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
7928also use the @value{GDBN} command-line word completion facilities to list the
7929available choices, or to finish the type list for you.
7930@xref{Completion,, Command completion}, for details on how to do this.
7931@end table
c906108c 7932
6d2ebf8b 7933@node Modula-2
c906108c 7934@subsection Modula-2
7a292a7a 7935
d4f3574e 7936@cindex Modula-2, @value{GDBN} support
c906108c
SS
7937
7938The extensions made to @value{GDBN} to support Modula-2 only support
7939output from the @sc{gnu} Modula-2 compiler (which is currently being
7940developed). Other Modula-2 compilers are not currently supported, and
7941attempting to debug executables produced by them is most likely
7942to give an error as @value{GDBN} reads in the executable's symbol
7943table.
7944
7945@cindex expressions in Modula-2
7946@menu
7947* M2 Operators:: Built-in operators
7948* Built-In Func/Proc:: Built-in functions and procedures
7949* M2 Constants:: Modula-2 constants
7950* M2 Defaults:: Default settings for Modula-2
7951* Deviations:: Deviations from standard Modula-2
7952* M2 Checks:: Modula-2 type and range checks
7953* M2 Scope:: The scope operators @code{::} and @code{.}
7954* GDB/M2:: @value{GDBN} and Modula-2
7955@end menu
7956
6d2ebf8b 7957@node M2 Operators
c906108c
SS
7958@subsubsection Operators
7959@cindex Modula-2 operators
7960
7961Operators must be defined on values of specific types. For instance,
7962@code{+} is defined on numbers, but not on structures. Operators are
7963often defined on groups of types. For the purposes of Modula-2, the
7964following definitions hold:
7965
7966@itemize @bullet
7967
7968@item
7969@emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
7970their subranges.
7971
7972@item
7973@emph{Character types} consist of @code{CHAR} and its subranges.
7974
7975@item
7976@emph{Floating-point types} consist of @code{REAL}.
7977
7978@item
7979@emph{Pointer types} consist of anything declared as @code{POINTER TO
7980@var{type}}.
7981
7982@item
7983@emph{Scalar types} consist of all of the above.
7984
7985@item
7986@emph{Set types} consist of @code{SET} and @code{BITSET} types.
7987
7988@item
7989@emph{Boolean types} consist of @code{BOOLEAN}.
7990@end itemize
7991
7992@noindent
7993The following operators are supported, and appear in order of
7994increasing precedence:
7995
7996@table @code
7997@item ,
7998Function argument or array index separator.
7999
8000@item :=
8001Assignment. The value of @var{var} @code{:=} @var{value} is
8002@var{value}.
8003
8004@item <@r{, }>
8005Less than, greater than on integral, floating-point, or enumerated
8006types.
8007
8008@item <=@r{, }>=
96a2c332 8009Less than or equal to, greater than or equal to
c906108c
SS
8010on integral, floating-point and enumerated types, or set inclusion on
8011set types. Same precedence as @code{<}.
8012
8013@item =@r{, }<>@r{, }#
8014Equality and two ways of expressing inequality, valid on scalar types.
8015Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8016available for inequality, since @code{#} conflicts with the script
8017comment character.
8018
8019@item IN
8020Set membership. Defined on set types and the types of their members.
8021Same precedence as @code{<}.
8022
8023@item OR
8024Boolean disjunction. Defined on boolean types.
8025
8026@item AND@r{, }&
d4f3574e 8027Boolean conjunction. Defined on boolean types.
c906108c
SS
8028
8029@item @@
8030The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8031
8032@item +@r{, }-
8033Addition and subtraction on integral and floating-point types, or union
8034and difference on set types.
8035
8036@item *
8037Multiplication on integral and floating-point types, or set intersection
8038on set types.
8039
8040@item /
8041Division on floating-point types, or symmetric set difference on set
8042types. Same precedence as @code{*}.
8043
8044@item DIV@r{, }MOD
8045Integer division and remainder. Defined on integral types. Same
8046precedence as @code{*}.
8047
8048@item -
8049Negative. Defined on @code{INTEGER} and @code{REAL} data.
8050
8051@item ^
8052Pointer dereferencing. Defined on pointer types.
8053
8054@item NOT
8055Boolean negation. Defined on boolean types. Same precedence as
8056@code{^}.
8057
8058@item .
8059@code{RECORD} field selector. Defined on @code{RECORD} data. Same
8060precedence as @code{^}.
8061
8062@item []
8063Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8064
8065@item ()
8066Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8067as @code{^}.
8068
8069@item ::@r{, }.
8070@value{GDBN} and Modula-2 scope operators.
8071@end table
8072
8073@quotation
8074@emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8075treats the use of the operator @code{IN}, or the use of operators
8076@code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8077@code{<=}, and @code{>=} on sets as an error.
8078@end quotation
8079
cb51c4e0 8080
6d2ebf8b 8081@node Built-In Func/Proc
c906108c 8082@subsubsection Built-in functions and procedures
cb51c4e0 8083@cindex Modula-2 built-ins
c906108c
SS
8084
8085Modula-2 also makes available several built-in procedures and functions.
8086In describing these, the following metavariables are used:
8087
8088@table @var
8089
8090@item a
8091represents an @code{ARRAY} variable.
8092
8093@item c
8094represents a @code{CHAR} constant or variable.
8095
8096@item i
8097represents a variable or constant of integral type.
8098
8099@item m
8100represents an identifier that belongs to a set. Generally used in the
8101same function with the metavariable @var{s}. The type of @var{s} should
8102be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8103
8104@item n
8105represents a variable or constant of integral or floating-point type.
8106
8107@item r
8108represents a variable or constant of floating-point type.
8109
8110@item t
8111represents a type.
8112
8113@item v
8114represents a variable.
8115
8116@item x
8117represents a variable or constant of one of many types. See the
8118explanation of the function for details.
8119@end table
8120
8121All Modula-2 built-in procedures also return a result, described below.
8122
8123@table @code
8124@item ABS(@var{n})
8125Returns the absolute value of @var{n}.
8126
8127@item CAP(@var{c})
8128If @var{c} is a lower case letter, it returns its upper case
c3f6f71d 8129equivalent, otherwise it returns its argument.
c906108c
SS
8130
8131@item CHR(@var{i})
8132Returns the character whose ordinal value is @var{i}.
8133
8134@item DEC(@var{v})
c3f6f71d 8135Decrements the value in the variable @var{v} by one. Returns the new value.
c906108c
SS
8136
8137@item DEC(@var{v},@var{i})
8138Decrements the value in the variable @var{v} by @var{i}. Returns the
8139new value.
8140
8141@item EXCL(@var{m},@var{s})
8142Removes the element @var{m} from the set @var{s}. Returns the new
8143set.
8144
8145@item FLOAT(@var{i})
8146Returns the floating point equivalent of the integer @var{i}.
8147
8148@item HIGH(@var{a})
8149Returns the index of the last member of @var{a}.
8150
8151@item INC(@var{v})
c3f6f71d 8152Increments the value in the variable @var{v} by one. Returns the new value.
c906108c
SS
8153
8154@item INC(@var{v},@var{i})
8155Increments the value in the variable @var{v} by @var{i}. Returns the
8156new value.
8157
8158@item INCL(@var{m},@var{s})
8159Adds the element @var{m} to the set @var{s} if it is not already
8160there. Returns the new set.
8161
8162@item MAX(@var{t})
8163Returns the maximum value of the type @var{t}.
8164
8165@item MIN(@var{t})
8166Returns the minimum value of the type @var{t}.
8167
8168@item ODD(@var{i})
8169Returns boolean TRUE if @var{i} is an odd number.
8170
8171@item ORD(@var{x})
8172Returns the ordinal value of its argument. For example, the ordinal
c3f6f71d
JM
8173value of a character is its @sc{ascii} value (on machines supporting the
8174@sc{ascii} character set). @var{x} must be of an ordered type, which include
c906108c
SS
8175integral, character and enumerated types.
8176
8177@item SIZE(@var{x})
8178Returns the size of its argument. @var{x} can be a variable or a type.
8179
8180@item TRUNC(@var{r})
8181Returns the integral part of @var{r}.
8182
8183@item VAL(@var{t},@var{i})
8184Returns the member of the type @var{t} whose ordinal value is @var{i}.
8185@end table
8186
8187@quotation
8188@emph{Warning:} Sets and their operations are not yet supported, so
8189@value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8190an error.
8191@end quotation
8192
8193@cindex Modula-2 constants
6d2ebf8b 8194@node M2 Constants
c906108c
SS
8195@subsubsection Constants
8196
8197@value{GDBN} allows you to express the constants of Modula-2 in the following
8198ways:
8199
8200@itemize @bullet
8201
8202@item
8203Integer constants are simply a sequence of digits. When used in an
8204expression, a constant is interpreted to be type-compatible with the
8205rest of the expression. Hexadecimal integers are specified by a
8206trailing @samp{H}, and octal integers by a trailing @samp{B}.
8207
8208@item
8209Floating point constants appear as a sequence of digits, followed by a
8210decimal point and another sequence of digits. An optional exponent can
8211then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8212@samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8213digits of the floating point constant must be valid decimal (base 10)
8214digits.
8215
8216@item
8217Character constants consist of a single character enclosed by a pair of
8218like quotes, either single (@code{'}) or double (@code{"}). They may
c3f6f71d 8219also be expressed by their ordinal value (their @sc{ascii} value, usually)
c906108c
SS
8220followed by a @samp{C}.
8221
8222@item
8223String constants consist of a sequence of characters enclosed by a
8224pair of like quotes, either single (@code{'}) or double (@code{"}).
8225Escape sequences in the style of C are also allowed. @xref{C
b37052ae 8226Constants, ,C and C@t{++} constants}, for a brief explanation of escape
c906108c
SS
8227sequences.
8228
8229@item
8230Enumerated constants consist of an enumerated identifier.
8231
8232@item
8233Boolean constants consist of the identifiers @code{TRUE} and
8234@code{FALSE}.
8235
8236@item
8237Pointer constants consist of integral values only.
8238
8239@item
8240Set constants are not yet supported.
8241@end itemize
8242
6d2ebf8b 8243@node M2 Defaults
c906108c
SS
8244@subsubsection Modula-2 defaults
8245@cindex Modula-2 defaults
8246
8247If type and range checking are set automatically by @value{GDBN}, they
8248both default to @code{on} whenever the working language changes to
d4f3574e 8249Modula-2. This happens regardless of whether you or @value{GDBN}
c906108c
SS
8250selected the working language.
8251
8252If you allow @value{GDBN} to set the language automatically, then entering
8253code compiled from a file whose name ends with @file{.mod} sets the
d4f3574e 8254working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
c906108c
SS
8255the language automatically}, for further details.
8256
6d2ebf8b 8257@node Deviations
c906108c
SS
8258@subsubsection Deviations from standard Modula-2
8259@cindex Modula-2, deviations from
8260
8261A few changes have been made to make Modula-2 programs easier to debug.
8262This is done primarily via loosening its type strictness:
8263
8264@itemize @bullet
8265@item
8266Unlike in standard Modula-2, pointer constants can be formed by
8267integers. This allows you to modify pointer variables during
8268debugging. (In standard Modula-2, the actual address contained in a
8269pointer variable is hidden from you; it can only be modified
8270through direct assignment to another pointer variable or expression that
8271returned a pointer.)
8272
8273@item
8274C escape sequences can be used in strings and characters to represent
8275non-printable characters. @value{GDBN} prints out strings with these
8276escape sequences embedded. Single non-printable characters are
8277printed using the @samp{CHR(@var{nnn})} format.
8278
8279@item
8280The assignment operator (@code{:=}) returns the value of its right-hand
8281argument.
8282
8283@item
8284All built-in procedures both modify @emph{and} return their argument.
8285@end itemize
8286
6d2ebf8b 8287@node M2 Checks
c906108c
SS
8288@subsubsection Modula-2 type and range checks
8289@cindex Modula-2 checks
8290
8291@quotation
8292@emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8293range checking.
8294@end quotation
8295@c FIXME remove warning when type/range checks added
8296
8297@value{GDBN} considers two Modula-2 variables type equivalent if:
8298
8299@itemize @bullet
8300@item
8301They are of types that have been declared equivalent via a @code{TYPE
8302@var{t1} = @var{t2}} statement
8303
8304@item
8305They have been declared on the same line. (Note: This is true of the
8306@sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8307@end itemize
8308
8309As long as type checking is enabled, any attempt to combine variables
8310whose types are not equivalent is an error.
8311
8312Range checking is done on all mathematical operations, assignment, array
8313index bounds, and all built-in functions and procedures.
8314
6d2ebf8b 8315@node M2 Scope
c906108c
SS
8316@subsubsection The scope operators @code{::} and @code{.}
8317@cindex scope
41afff9a 8318@cindex @code{.}, Modula-2 scope operator
c906108c
SS
8319@cindex colon, doubled as scope operator
8320@ifinfo
41afff9a 8321@vindex colon-colon@r{, in Modula-2}
c906108c
SS
8322@c Info cannot handle :: but TeX can.
8323@end ifinfo
8324@iftex
41afff9a 8325@vindex ::@r{, in Modula-2}
c906108c
SS
8326@end iftex
8327
8328There are a few subtle differences between the Modula-2 scope operator
8329(@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8330similar syntax:
8331
474c8240 8332@smallexample
c906108c
SS
8333
8334@var{module} . @var{id}
8335@var{scope} :: @var{id}
474c8240 8336@end smallexample
c906108c
SS
8337
8338@noindent
8339where @var{scope} is the name of a module or a procedure,
8340@var{module} the name of a module, and @var{id} is any declared
8341identifier within your program, except another module.
8342
8343Using the @code{::} operator makes @value{GDBN} search the scope
8344specified by @var{scope} for the identifier @var{id}. If it is not
8345found in the specified scope, then @value{GDBN} searches all scopes
8346enclosing the one specified by @var{scope}.
8347
8348Using the @code{.} operator makes @value{GDBN} search the current scope for
8349the identifier specified by @var{id} that was imported from the
8350definition module specified by @var{module}. With this operator, it is
8351an error if the identifier @var{id} was not imported from definition
8352module @var{module}, or if @var{id} is not an identifier in
8353@var{module}.
8354
6d2ebf8b 8355@node GDB/M2
c906108c
SS
8356@subsubsection @value{GDBN} and Modula-2
8357
8358Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8359Five subcommands of @code{set print} and @code{show print} apply
b37052ae 8360specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
c906108c 8361@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
b37052ae 8362apply to C@t{++}, and the last to the C @code{union} type, which has no direct
c906108c
SS
8363analogue in Modula-2.
8364
8365The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
d4f3574e 8366with any language, is not useful with Modula-2. Its
c906108c 8367intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
b37052ae 8368created in Modula-2 as they can in C or C@t{++}. However, because an
c906108c 8369address can be specified by an integral constant, the construct
d4f3574e 8370@samp{@{@var{type}@}@var{adrexp}} is still useful.
c906108c
SS
8371
8372@cindex @code{#} in Modula-2
8373In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8374interpreted as the beginning of a comment. Use @code{<>} instead.
c906108c 8375
6d2ebf8b 8376@node Chill
cce74817
JM
8377@subsection Chill
8378
8379The extensions made to @value{GDBN} to support Chill only support output
d4f3574e 8380from the @sc{gnu} Chill compiler. Other Chill compilers are not currently
cce74817
JM
8381supported, and attempting to debug executables produced by them is most
8382likely to give an error as @value{GDBN} reads in the executable's symbol
8383table.
8384
d4f3574e
SS
8385@c This used to say "... following Chill related topics ...", but since
8386@c menus are not shown in the printed manual, it would look awkward.
8387This section covers the Chill related topics and the features
cce74817
JM
8388of @value{GDBN} which support these topics.
8389
8390@menu
104c1213
JM
8391* How modes are displayed:: How modes are displayed
8392* Locations:: Locations and their accesses
cce74817 8393* Values and their Operations:: Values and their Operations
5d161b24 8394* Chill type and range checks::
53a5351d 8395* Chill defaults::
cce74817
JM
8396@end menu
8397
6d2ebf8b 8398@node How modes are displayed
cce74817
JM
8399@subsubsection How modes are displayed
8400
8401The Chill Datatype- (Mode) support of @value{GDBN} is directly related
d4f3574e 8402with the functionality of the @sc{gnu} Chill compiler, and therefore deviates
cce74817
JM
8403slightly from the standard specification of the Chill language. The
8404provided modes are:
d4f3574e
SS
8405
8406@c FIXME: this @table's contents effectively disable @code by using @r
8407@c on every @item. So why does it need @code?
cce74817
JM
8408@table @code
8409@item @r{@emph{Discrete modes:}}
8410@itemize @bullet
8411@item
8412@emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT,
8413UINT, LONG, ULONG},
8414@item
5d161b24 8415@emph{Boolean Mode} which is predefined by @code{BOOL},
cce74817 8416@item
5d161b24 8417@emph{Character Mode} which is predefined by @code{CHAR},
cce74817
JM
8418@item
8419@emph{Set Mode} which is displayed by the keyword @code{SET}.
8420@smallexample
8421(@value{GDBP}) ptype x
8422type = SET (karli = 10, susi = 20, fritzi = 100)
8423@end smallexample
8424If the type is an unnumbered set the set element values are omitted.
8425@item
6d2ebf8b
SS
8426@emph{Range Mode} which is displayed by
8427@smallexample
8428@code{type = <basemode>(<lower bound> : <upper bound>)}
8429@end smallexample
8430where @code{<lower bound>, <upper bound>} can be of any discrete literal
8431expression (e.g. set element names).
cce74817
JM
8432@end itemize
8433
8434@item @r{@emph{Powerset Mode:}}
8435A Powerset Mode is displayed by the keyword @code{POWERSET} followed by
d4f3574e 8436the member mode of the powerset. The member mode can be any discrete mode.
cce74817
JM
8437@smallexample
8438(@value{GDBP}) ptype x
8439type = POWERSET SET (egon, hugo, otto)
8440@end smallexample
8441
8442@item @r{@emph{Reference Modes:}}
8443@itemize @bullet
8444@item
d4f3574e 8445@emph{Bound Reference Mode} which is displayed by the keyword @code{REF}
cce74817
JM
8446followed by the mode name to which the reference is bound.
8447@item
8448@emph{Free Reference Mode} which is displayed by the keyword @code{PTR}.
8449@end itemize
8450
8451@item @r{@emph{Procedure mode}}
8452The procedure mode is displayed by @code{type = PROC(<parameter list>)
8453<return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter
d4f3574e
SS
8454list>} is a list of the parameter modes. @code{<return mode>} indicates
8455the mode of the result of the procedure if any. The exceptionlist lists
cce74817
JM
8456all possible exceptions which can be raised by the procedure.
8457
8458@ignore
8459@item @r{@emph{Instance mode}}
8460The instance mode is represented by a structure, which has a static
5d161b24 8461type, and is therefore not really of interest.
cce74817
JM
8462@end ignore
8463
5d161b24 8464@item @r{@emph{Synchronization Modes:}}
cce74817
JM
8465@itemize @bullet
8466@item
6d2ebf8b
SS
8467@emph{Event Mode} which is displayed by
8468@smallexample
8469@code{EVENT (<event length>)}
8470@end smallexample
cce74817
JM
8471where @code{(<event length>)} is optional.
8472@item
6d2ebf8b
SS
8473@emph{Buffer Mode} which is displayed by
8474@smallexample
8475@code{BUFFER (<buffer length>)<buffer element mode>}
8476@end smallexample
8477where @code{(<buffer length>)} is optional.
cce74817
JM
8478@end itemize
8479
5d161b24 8480@item @r{@emph{Timing Modes:}}
cce74817
JM
8481@itemize @bullet
8482@item
8483@emph{Duration Mode} which is predefined by @code{DURATION}
8484@item
8485@emph{Absolute Time Mode} which is predefined by @code{TIME}
8486@end itemize
8487
8488@item @r{@emph{Real Modes:}}
8489Real Modes are predefined with @code{REAL} and @code{LONG_REAL}.
8490
8491@item @r{@emph{String Modes:}}
8492@itemize @bullet
8493@item
6d2ebf8b
SS
8494@emph{Character String Mode} which is displayed by
8495@smallexample
8496@code{CHARS(<string length>)}
8497@end smallexample
8498followed by the keyword @code{VARYING} if the String Mode is a varying
8499mode
cce74817 8500@item
6d2ebf8b
SS
8501@emph{Bit String Mode} which is displayed by
8502@smallexample
8503@code{BOOLS(<string
8504length>)}
8505@end smallexample
cce74817
JM
8506@end itemize
8507
8508@item @r{@emph{Array Mode:}}
8509The Array Mode is displayed by the keyword @code{ARRAY(<range>)}
8510followed by the element mode (which may in turn be an array mode).
8511@smallexample
8512(@value{GDBP}) ptype x
5d161b24
DB
8513type = ARRAY (1:42)
8514 ARRAY (1:20)
cce74817
JM
8515 SET (karli = 10, susi = 20, fritzi = 100)
8516@end smallexample
8517
5d161b24 8518@item @r{@emph{Structure Mode}}
cce74817 8519The Structure mode is displayed by the keyword @code{STRUCT(<field
d4f3574e
SS
8520list>)}. The @code{<field list>} consists of names and modes of fields
8521of the structure. Variant structures have the keyword @code{CASE <field>
8522OF <variant fields> ESAC} in their field list. Since the current version
cce74817
JM
8523of the GNU Chill compiler doesn't implement tag processing (no runtime
8524checks of variant fields, and therefore no debugging info), the output
8525always displays all variant fields.
8526@smallexample
8527(@value{GDBP}) ptype str
8528type = STRUCT (
8529 as x,
8530 bs x,
8531 CASE bs OF
8532 (karli):
8533 cs a
8534 (ott):
8535 ds x
8536 ESAC
8537)
8538@end smallexample
8539@end table
8540
6d2ebf8b 8541@node Locations
cce74817
JM
8542@subsubsection Locations and their accesses
8543
8544A location in Chill is an object which can contain values.
8545
8546A value of a location is generally accessed by the (declared) name of
d4f3574e
SS
8547the location. The output conforms to the specification of values in
8548Chill programs. How values are specified
8549is the topic of the next section, @ref{Values and their Operations}.
cce74817
JM
8550
8551The pseudo-location @code{RESULT} (or @code{result}) can be used to
8552display or change the result of a currently-active procedure:
d4f3574e 8553
cce74817
JM
8554@smallexample
8555set result := EXPR
8556@end smallexample
d4f3574e
SS
8557
8558@noindent
8559This does the same as the Chill action @code{RESULT EXPR} (which
c3f6f71d 8560is not available in @value{GDBN}).
cce74817
JM
8561
8562Values of reference mode locations are printed by @code{PTR(<hex
8563value>)} in case of a free reference mode, and by @code{(REF <reference
d4f3574e 8564mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>}
cce74817
JM
8565represents the address where the reference points to. To access the
8566value of the location referenced by the pointer, use the dereference
d4f3574e 8567operator @samp{->}.
cce74817 8568
6d2ebf8b
SS
8569Values of procedure mode locations are displayed by
8570@smallexample
8571@code{@{ PROC
cce74817 8572(<argument modes> ) <return mode> @} <address> <name of procedure
6d2ebf8b
SS
8573location>}
8574@end smallexample
8575@code{<argument modes>} is a list of modes according to the parameter
8576specification of the procedure and @code{<address>} shows the address of
8577the entry point.
cce74817
JM
8578
8579@ignore
8580Locations of instance modes are displayed just like a structure with two
8581fields specifying the @emph{process type} and the @emph{copy number} of
8582the investigated instance location@footnote{This comes from the current
d4f3574e
SS
8583implementation of instances. They are implemented as a structure (no
8584na). The output should be something like @code{[<name of the process>;
8585<instance number>]}.}. The field names are @code{__proc_type} and
cce74817
JM
8586@code{__proc_copy}.
8587
8588Locations of synchronization modes are displayed like a structure with
8589the field name @code{__event_data} in case of a event mode location, and
8590like a structure with the field @code{__buffer_data} in case of a buffer
8591mode location (refer to previous paragraph).
8592
8593Structure Mode locations are printed by @code{[.<field name>: <value>,
d4f3574e 8594...]}. The @code{<field name>} corresponds to the structure mode
cce74817 8595definition and the layout of @code{<value>} varies depending of the mode
d4f3574e
SS
8596of the field. If the investigated structure mode location is of variant
8597structure mode, the variant parts of the structure are enclosed in curled
8598braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing
cce74817 8599on the same memory location and represent the current values of the
d4f3574e 8600memory location in their specific modes. Since no tag processing is done
cce74817 8601all variants are displayed. A variant field is printed by
d4f3574e 8602@code{(<variant name>) = .<field name>: <value>}. (who implements the
cce74817
JM
8603stuff ???)
8604@smallexample
8605(@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) =
8606[.cs: []], (susi) = [.ds: susi]}]
8607@end smallexample
8608@end ignore
8609
8610Substructures of string mode-, array mode- or structure mode-values
8611(e.g. array slices, fields of structure locations) are accessed using
d4f3574e
SS
8612certain operations which are described in the next section, @ref{Values
8613and their Operations}.
cce74817
JM
8614
8615A location value may be interpreted as having a different mode using the
d4f3574e
SS
8616location conversion. This mode conversion is written as @code{<mode
8617name>(<location>)}. The user has to consider that the sizes of the modes
8618have to be equal otherwise an error occurs. Furthermore, no range
8619checking of the location against the destination mode is performed, and
cce74817 8620therefore the result can be quite confusing.
d4f3574e 8621
cce74817
JM
8622@smallexample
8623(@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX
8624@end smallexample
8625
6d2ebf8b 8626@node Values and their Operations
cce74817
JM
8627@subsubsection Values and their Operations
8628
8629Values are used to alter locations, to investigate complex structures in
8630more detail or to filter relevant information out of a large amount of
d4f3574e
SS
8631data. There are several (mode dependent) operations defined which enable
8632such investigations. These operations are not only applicable to
cce74817 8633constant values but also to locations, which can become quite useful
d4f3574e 8634when debugging complex structures. During parsing the command line
cce74817
JM
8635(e.g. evaluating an expression) @value{GDBN} treats location names as
8636the values behind these locations.
8637
d4f3574e 8638This section describes how values have to be specified and which
cce74817
JM
8639operations are legal to be used with such values.
8640
8641@table @code
8642@item Literal Values
d4f3574e
SS
8643Literal values are specified in the same manner as in @sc{gnu} Chill programs.
8644For detailed specification refer to the @sc{gnu} Chill implementation Manual
cce74817 8645chapter 1.5.
d4f3574e
SS
8646@c FIXME: if the Chill Manual is a Texinfo documents, the above should
8647@c be converted to a @ref.
cce74817 8648
5d161b24 8649@ignore
cce74817
JM
8650@itemize @bullet
8651@item
8652@emph{Integer Literals} are specified in the same manner as in Chill
d4f3574e 8653programs (refer to the Chill Standard z200/88 chpt 5.2.4.2)
cce74817
JM
8654@item
8655@emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}.
8656@item
8657@emph{Character Literals} are defined by @code{'<character>'}. (e.g.
8658@code{'M'})
8659@item
8660@emph{Set Literals} are defined by a name which was specified in a set
d4f3574e 8661mode. The value delivered by a Set Literal is the set value. This is
b37052ae 8662comparable to an enumeration in C/C@t{++} language.
cce74817 8663@item
d4f3574e 8664@emph{Emptiness Literal} is predefined by @code{NULL}. The value of the
cce74817 8665emptiness literal delivers either the empty reference value, the empty
5d161b24 8666procedure value or the empty instance value.
cce74817
JM
8667
8668@item
8669@emph{Character String Literals} are defined by a sequence of characters
d4f3574e 8670enclosed in single- or double quotes. If a single- or double quote has
cce74817
JM
8671to be part of the string literal it has to be stuffed (specified twice).
8672@item
8673@emph{Bitstring Literals} are specified in the same manner as in Chill
8674programs (refer z200/88 chpt 5.2.4.8).
8675@item
8676@emph{Floating point literals} are specified in the same manner as in
d4f3574e 8677(gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5).
cce74817
JM
8678@end itemize
8679@end ignore
8680
8681@item Tuple Values
8682A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode
d4f3574e 8683name>} can be omitted if the mode of the tuple is unambiguous. This
cce74817
JM
8684unambiguity is derived from the context of a evaluated expression.
8685@code{<tuple>} can be one of the following:
d4f3574e 8686
cce74817
JM
8687@itemize @bullet
8688@item @emph{Powerset Tuple}
8689@item @emph{Array Tuple}
8690@item @emph{Structure Tuple}
8691Powerset tuples, array tuples and structure tuples are specified in the
d4f3574e 8692same manner as in Chill programs refer to z200/88 chpt 5.2.5.
cce74817
JM
8693@end itemize
8694
8695@item String Element Value
6d2ebf8b
SS
8696A string element value is specified by
8697@smallexample
8698@code{<string value>(<index>)}
8699@end smallexample
d4f3574e 8700where @code{<index>} is a integer expression. It delivers a character
cce74817
JM
8701value which is equivalent to the character indexed by @code{<index>} in
8702the string.
8703
8704@item String Slice Value
8705A string slice value is specified by @code{<string value>(<slice
8706spec>)}, where @code{<slice spec>} can be either a range of integer
8707expressions or specified by @code{<start expr> up <size>}.
8708@code{<size>} denotes the number of elements which the slice contains.
8709The delivered value is a string value, which is part of the specified
8710string.
8711
8712@item Array Element Values
8713An array element value is specified by @code{<array value>(<expr>)} and
8714delivers a array element value of the mode of the specified array.
8715
8716@item Array Slice Values
8717An array slice is specified by @code{<array value>(<slice spec>)}, where
8718@code{<slice spec>} can be either a range specified by expressions or by
d4f3574e
SS
8719@code{<start expr> up <size>}. @code{<size>} denotes the number of
8720arrayelements the slice contains. The delivered value is an array value
cce74817
JM
8721which is part of the specified array.
8722
8723@item Structure Field Values
8724A structure field value is derived by @code{<structure value>.<field
d4f3574e
SS
8725name>}, where @code{<field name>} indicates the name of a field specified
8726in the mode definition of the structure. The mode of the delivered value
cce74817
JM
8727corresponds to this mode definition in the structure definition.
8728
8729@item Procedure Call Value
8730The procedure call value is derived from the return value of the
8731procedure@footnote{If a procedure call is used for instance in an
8732expression, then this procedure is called with all its side
d4f3574e 8733effects. This can lead to confusing results if used carelessly.}.
cce74817 8734
d4f3574e 8735Values of duration mode locations are represented by @code{ULONG} literals.
cce74817 8736
6d2ebf8b
SS
8737Values of time mode locations appear as
8738@smallexample
8739@code{TIME(<secs>:<nsecs>)}
8740@end smallexample
8741
cce74817
JM
8742
8743@ignore
8744This is not implemented yet:
8745@item Built-in Value
8746@noindent
8747The following built in functions are provided:
d4f3574e 8748
cce74817
JM
8749@table @code
8750@item @code{ADDR()}
8751@item @code{NUM()}
8752@item @code{PRED()}
8753@item @code{SUCC()}
8754@item @code{ABS()}
8755@item @code{CARD()}
8756@item @code{MAX()}
8757@item @code{MIN()}
8758@item @code{SIZE()}
8759@item @code{UPPER()}
8760@item @code{LOWER()}
8761@item @code{LENGTH()}
8762@item @code{SIN()}
8763@item @code{COS()}
8764@item @code{TAN()}
8765@item @code{ARCSIN()}
8766@item @code{ARCCOS()}
8767@item @code{ARCTAN()}
8768@item @code{EXP()}
8769@item @code{LN()}
8770@item @code{LOG()}
8771@item @code{SQRT()}
8772@end table
8773
8774For a detailed description refer to the GNU Chill implementation manual
8775chapter 1.6.
8776@end ignore
8777
8778@item Zero-adic Operator Value
8779The zero-adic operator value is derived from the instance value for the
8780current active process.
8781
8782@item Expression Values
8783The value delivered by an expression is the result of the evaluation of
d4f3574e 8784the specified expression. If there are error conditions (mode
cce74817 8785incompatibility, etc.) the evaluation of expressions is aborted with a
d4f3574e 8786corresponding error message. Expressions may be parenthesised which
cce74817 8787causes the evaluation of this expression before any other expression
d4f3574e 8788which uses the result of the parenthesised expression. The following
cce74817 8789operators are supported by @value{GDBN}:
d4f3574e 8790
cce74817
JM
8791@table @code
8792@item @code{OR, ORIF, XOR}
d4f3574e
SS
8793@itemx @code{AND, ANDIF}
8794@itemx @code{NOT}
cce74817 8795Logical operators defined over operands of boolean mode.
d4f3574e 8796
cce74817
JM
8797@item @code{=, /=}
8798Equality and inequality operators defined over all modes.
d4f3574e 8799
cce74817 8800@item @code{>, >=}
d4f3574e 8801@itemx @code{<, <=}
cce74817 8802Relational operators defined over predefined modes.
d4f3574e 8803
cce74817 8804@item @code{+, -}
d4f3574e 8805@itemx @code{*, /, MOD, REM}
cce74817 8806Arithmetic operators defined over predefined modes.
d4f3574e 8807
cce74817
JM
8808@item @code{-}
8809Change sign operator.
d4f3574e 8810
cce74817
JM
8811@item @code{//}
8812String concatenation operator.
d4f3574e 8813
cce74817
JM
8814@item @code{()}
8815String repetition operator.
d4f3574e 8816
cce74817
JM
8817@item @code{->}
8818Referenced location operator which can be used either to take the
8819address of a location (@code{->loc}), or to dereference a reference
8820location (@code{loc->}).
d4f3574e 8821
cce74817 8822@item @code{OR, XOR}
d4f3574e
SS
8823@itemx @code{AND}
8824@itemx @code{NOT}
cce74817 8825Powerset and bitstring operators.
d4f3574e 8826
cce74817 8827@item @code{>, >=}
d4f3574e 8828@itemx @code{<, <=}
cce74817 8829Powerset inclusion operators.
d4f3574e 8830
cce74817
JM
8831@item @code{IN}
8832Membership operator.
8833@end table
8834@end table
8835
6d2ebf8b 8836@node Chill type and range checks
cce74817
JM
8837@subsubsection Chill type and range checks
8838
8839@value{GDBN} considers two Chill variables mode equivalent if the sizes
d4f3574e 8840of the two modes are equal. This rule applies recursively to more
cce74817 8841complex datatypes which means that complex modes are treated
d4f3574e 8842equivalent if all element modes (which also can be complex modes like
cce74817
JM
8843structures, arrays, etc.) have the same size.
8844
8845Range checking is done on all mathematical operations, assignment, array
8846index bounds and all built in procedures.
8847
8848Strong type checks are forced using the @value{GDBN} command @code{set
d4f3574e 8849check strong}. This enforces strong type and range checks on all
cce74817
JM
8850operations where Chill constructs are used (expressions, built in
8851functions, etc.) in respect to the semantics as defined in the z.200
8852language specification.
8853
cce74817
JM
8854All checks can be disabled by the @value{GDBN} command @code{set check
8855off}.
8856
5d161b24 8857@ignore
53a5351d 8858@c Deviations from the Chill Standard Z200/88
cce74817
JM
8859see last paragraph ?
8860@end ignore
8861
6d2ebf8b 8862@node Chill defaults
cce74817
JM
8863@subsubsection Chill defaults
8864
8865If type and range checking are set automatically by @value{GDBN}, they
8866both default to @code{on} whenever the working language changes to
d4f3574e 8867Chill. This happens regardless of whether you or @value{GDBN}
cce74817
JM
8868selected the working language.
8869
8870If you allow @value{GDBN} to set the language automatically, then entering
8871code compiled from a file whose name ends with @file{.ch} sets the
d4f3574e 8872working language to Chill. @xref{Automatically, ,Having @value{GDBN} set
cce74817
JM
8873the language automatically}, for further details.
8874
6d2ebf8b 8875@node Symbols
c906108c
SS
8876@chapter Examining the Symbol Table
8877
d4f3574e 8878The commands described in this chapter allow you to inquire about the
c906108c
SS
8879symbols (names of variables, functions and types) defined in your
8880program. This information is inherent in the text of your program and
8881does not change as your program executes. @value{GDBN} finds it in your
8882program's symbol table, in the file indicated when you started @value{GDBN}
8883(@pxref{File Options, ,Choosing files}), or by one of the
8884file-management commands (@pxref{Files, ,Commands to specify files}).
8885
8886@cindex symbol names
8887@cindex names of symbols
8888@cindex quoting names
8889Occasionally, you may need to refer to symbols that contain unusual
8890characters, which @value{GDBN} ordinarily treats as word delimiters. The
8891most frequent case is in referring to static variables in other
8892source files (@pxref{Variables,,Program variables}). File names
8893are recorded in object files as debugging symbols, but @value{GDBN} would
8894ordinarily parse a typical file name, like @file{foo.c}, as the three words
8895@samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8896@samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8897
474c8240 8898@smallexample
c906108c 8899p 'foo.c'::x
474c8240 8900@end smallexample
c906108c
SS
8901
8902@noindent
8903looks up the value of @code{x} in the scope of the file @file{foo.c}.
8904
8905@table @code
8906@kindex info address
b37052ae 8907@cindex address of a symbol
c906108c
SS
8908@item info address @var{symbol}
8909Describe where the data for @var{symbol} is stored. For a register
8910variable, this says which register it is kept in. For a non-register
8911local variable, this prints the stack-frame offset at which the variable
8912is always stored.
8913
8914Note the contrast with @samp{print &@var{symbol}}, which does not work
8915at all for a register variable, and for a stack local variable prints
8916the exact address of the current instantiation of the variable.
8917
3d67e040 8918@kindex info symbol
b37052ae 8919@cindex symbol from address
3d67e040
EZ
8920@item info symbol @var{addr}
8921Print the name of a symbol which is stored at the address @var{addr}.
8922If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8923nearest symbol and an offset from it:
8924
474c8240 8925@smallexample
3d67e040
EZ
8926(@value{GDBP}) info symbol 0x54320
8927_initialize_vx + 396 in section .text
474c8240 8928@end smallexample
3d67e040
EZ
8929
8930@noindent
8931This is the opposite of the @code{info address} command. You can use
8932it to find out the name of a variable or a function given its address.
8933
c906108c 8934@kindex whatis
d4f3574e
SS
8935@item whatis @var{expr}
8936Print the data type of expression @var{expr}. @var{expr} is not
c906108c
SS
8937actually evaluated, and any side-effecting operations (such as
8938assignments or function calls) inside it do not take place.
8939@xref{Expressions, ,Expressions}.
8940
8941@item whatis
8942Print the data type of @code{$}, the last value in the value history.
8943
8944@kindex ptype
8945@item ptype @var{typename}
8946Print a description of data type @var{typename}. @var{typename} may be
7a292a7a
SS
8947the name of a type, or for C code it may have the form @samp{class
8948@var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8949@var{union-tag}} or @samp{enum @var{enum-tag}}.
c906108c 8950
d4f3574e 8951@item ptype @var{expr}
c906108c 8952@itemx ptype
d4f3574e 8953Print a description of the type of expression @var{expr}. @code{ptype}
c906108c
SS
8954differs from @code{whatis} by printing a detailed description, instead
8955of just the name of the type.
8956
8957For example, for this variable declaration:
8958
474c8240 8959@smallexample
c906108c 8960struct complex @{double real; double imag;@} v;
474c8240 8961@end smallexample
c906108c
SS
8962
8963@noindent
8964the two commands give this output:
8965
474c8240 8966@smallexample
c906108c
SS
8967@group
8968(@value{GDBP}) whatis v
8969type = struct complex
8970(@value{GDBP}) ptype v
8971type = struct complex @{
8972 double real;
8973 double imag;
8974@}
8975@end group
474c8240 8976@end smallexample
c906108c
SS
8977
8978@noindent
8979As with @code{whatis}, using @code{ptype} without an argument refers to
8980the type of @code{$}, the last value in the value history.
8981
8982@kindex info types
8983@item info types @var{regexp}
8984@itemx info types
d4f3574e 8985Print a brief description of all types whose names match @var{regexp}
c906108c
SS
8986(or all types in your program, if you supply no argument). Each
8987complete typename is matched as though it were a complete line; thus,
8988@samp{i type value} gives information on all types in your program whose
d4f3574e 8989names include the string @code{value}, but @samp{i type ^value$} gives
c906108c
SS
8990information only on types whose complete name is @code{value}.
8991
8992This command differs from @code{ptype} in two ways: first, like
8993@code{whatis}, it does not print a detailed description; second, it
8994lists all source files where a type is defined.
8995
b37052ae
EZ
8996@kindex info scope
8997@cindex local variables
8998@item info scope @var{addr}
8999List all the variables local to a particular scope. This command
9000accepts a location---a function name, a source line, or an address
9001preceded by a @samp{*}, and prints all the variables local to the
9002scope defined by that location. For example:
9003
9004@smallexample
9005(@value{GDBP}) @b{info scope command_line_handler}
9006Scope for command_line_handler:
9007Symbol rl is an argument at stack/frame offset 8, length 4.
9008Symbol linebuffer is in static storage at address 0x150a18, length 4.
9009Symbol linelength is in static storage at address 0x150a1c, length 4.
9010Symbol p is a local variable in register $esi, length 4.
9011Symbol p1 is a local variable in register $ebx, length 4.
9012Symbol nline is a local variable in register $edx, length 4.
9013Symbol repeat is a local variable at frame offset -8, length 4.
9014@end smallexample
9015
f5c37c66
EZ
9016@noindent
9017This command is especially useful for determining what data to collect
9018during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9019collect}.
9020
c906108c
SS
9021@kindex info source
9022@item info source
919d772c
JB
9023Show information about the current source file---that is, the source file for
9024the function containing the current point of execution:
9025@itemize @bullet
9026@item
9027the name of the source file, and the directory containing it,
9028@item
9029the directory it was compiled in,
9030@item
9031its length, in lines,
9032@item
9033which programming language it is written in,
9034@item
9035whether the executable includes debugging information for that file, and
9036if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9037@item
9038whether the debugging information includes information about
9039preprocessor macros.
9040@end itemize
9041
c906108c
SS
9042
9043@kindex info sources
9044@item info sources
9045Print the names of all source files in your program for which there is
9046debugging information, organized into two lists: files whose symbols
9047have already been read, and files whose symbols will be read when needed.
9048
9049@kindex info functions
9050@item info functions
9051Print the names and data types of all defined functions.
9052
9053@item info functions @var{regexp}
9054Print the names and data types of all defined functions
9055whose names contain a match for regular expression @var{regexp}.
9056Thus, @samp{info fun step} finds all functions whose names
9057include @code{step}; @samp{info fun ^step} finds those whose names
1c5dfdad
MS
9058start with @code{step}. If a function name contains characters
9059that conflict with the regular expression language (eg.
9060@samp{operator*()}), they may be quoted with a backslash.
c906108c
SS
9061
9062@kindex info variables
9063@item info variables
9064Print the names and data types of all variables that are declared
6ca652b0 9065outside of functions (i.e.@: excluding local variables).
c906108c
SS
9066
9067@item info variables @var{regexp}
9068Print the names and data types of all variables (except for local
9069variables) whose names contain a match for regular expression
9070@var{regexp}.
9071
9072@ignore
9073This was never implemented.
9074@kindex info methods
9075@item info methods
9076@itemx info methods @var{regexp}
9077The @code{info methods} command permits the user to examine all defined
b37052ae
EZ
9078methods within C@t{++} program, or (with the @var{regexp} argument) a
9079specific set of methods found in the various C@t{++} classes. Many
9080C@t{++} classes provide a large number of methods. Thus, the output
c906108c
SS
9081from the @code{ptype} command can be overwhelming and hard to use. The
9082@code{info-methods} command filters the methods, printing only those
9083which match the regular-expression @var{regexp}.
9084@end ignore
9085
c906108c
SS
9086@cindex reloading symbols
9087Some systems allow individual object files that make up your program to
7a292a7a
SS
9088be replaced without stopping and restarting your program. For example,
9089in VxWorks you can simply recompile a defective object file and keep on
9090running. If you are running on one of these systems, you can allow
9091@value{GDBN} to reload the symbols for automatically relinked modules:
c906108c
SS
9092
9093@table @code
9094@kindex set symbol-reloading
9095@item set symbol-reloading on
9096Replace symbol definitions for the corresponding source file when an
9097object file with a particular name is seen again.
9098
9099@item set symbol-reloading off
6d2ebf8b
SS
9100Do not replace symbol definitions when encountering object files of the
9101same name more than once. This is the default state; if you are not
9102running on a system that permits automatic relinking of modules, you
9103should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9104may discard symbols when linking large programs, that may contain
9105several modules (from different directories or libraries) with the same
9106name.
c906108c
SS
9107
9108@kindex show symbol-reloading
9109@item show symbol-reloading
9110Show the current @code{on} or @code{off} setting.
9111@end table
c906108c 9112
c906108c
SS
9113@kindex set opaque-type-resolution
9114@item set opaque-type-resolution on
9115Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9116declared as a pointer to a @code{struct}, @code{class}, or
9117@code{union}---for example, @code{struct MyType *}---that is used in one
9118source file although the full declaration of @code{struct MyType} is in
9119another source file. The default is on.
9120
9121A change in the setting of this subcommand will not take effect until
9122the next time symbols for a file are loaded.
9123
9124@item set opaque-type-resolution off
9125Tell @value{GDBN} not to resolve opaque types. In this case, the type
9126is printed as follows:
9127@smallexample
9128@{<no data fields>@}
9129@end smallexample
9130
9131@kindex show opaque-type-resolution
9132@item show opaque-type-resolution
9133Show whether opaque types are resolved or not.
c906108c
SS
9134
9135@kindex maint print symbols
9136@cindex symbol dump
9137@kindex maint print psymbols
9138@cindex partial symbol dump
9139@item maint print symbols @var{filename}
9140@itemx maint print psymbols @var{filename}
9141@itemx maint print msymbols @var{filename}
9142Write a dump of debugging symbol data into the file @var{filename}.
9143These commands are used to debug the @value{GDBN} symbol-reading code. Only
9144symbols with debugging data are included. If you use @samp{maint print
9145symbols}, @value{GDBN} includes all the symbols for which it has already
9146collected full details: that is, @var{filename} reflects symbols for
9147only those files whose symbols @value{GDBN} has read. You can use the
9148command @code{info sources} to find out which files these are. If you
9149use @samp{maint print psymbols} instead, the dump shows information about
9150symbols that @value{GDBN} only knows partially---that is, symbols defined in
9151files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9152@samp{maint print msymbols} dumps just the minimal symbol information
9153required for each object file from which @value{GDBN} has read some symbols.
9154@xref{Files, ,Commands to specify files}, for a discussion of how
9155@value{GDBN} reads symbols (in the description of @code{symbol-file}).
9156@end table
9157
6d2ebf8b 9158@node Altering
c906108c
SS
9159@chapter Altering Execution
9160
9161Once you think you have found an error in your program, you might want to
9162find out for certain whether correcting the apparent error would lead to
9163correct results in the rest of the run. You can find the answer by
9164experiment, using the @value{GDBN} features for altering execution of the
9165program.
9166
9167For example, you can store new values into variables or memory
7a292a7a
SS
9168locations, give your program a signal, restart it at a different
9169address, or even return prematurely from a function.
c906108c
SS
9170
9171@menu
9172* Assignment:: Assignment to variables
9173* Jumping:: Continuing at a different address
c906108c 9174* Signaling:: Giving your program a signal
c906108c
SS
9175* Returning:: Returning from a function
9176* Calling:: Calling your program's functions
9177* Patching:: Patching your program
9178@end menu
9179
6d2ebf8b 9180@node Assignment
c906108c
SS
9181@section Assignment to variables
9182
9183@cindex assignment
9184@cindex setting variables
9185To alter the value of a variable, evaluate an assignment expression.
9186@xref{Expressions, ,Expressions}. For example,
9187
474c8240 9188@smallexample
c906108c 9189print x=4
474c8240 9190@end smallexample
c906108c
SS
9191
9192@noindent
9193stores the value 4 into the variable @code{x}, and then prints the
5d161b24 9194value of the assignment expression (which is 4).
c906108c
SS
9195@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9196information on operators in supported languages.
c906108c
SS
9197
9198@kindex set variable
9199@cindex variables, setting
9200If you are not interested in seeing the value of the assignment, use the
9201@code{set} command instead of the @code{print} command. @code{set} is
9202really the same as @code{print} except that the expression's value is
9203not printed and is not put in the value history (@pxref{Value History,
9204,Value history}). The expression is evaluated only for its effects.
9205
c906108c
SS
9206If the beginning of the argument string of the @code{set} command
9207appears identical to a @code{set} subcommand, use the @code{set
9208variable} command instead of just @code{set}. This command is identical
9209to @code{set} except for its lack of subcommands. For example, if your
9210program has a variable @code{width}, you get an error if you try to set
9211a new value with just @samp{set width=13}, because @value{GDBN} has the
9212command @code{set width}:
9213
474c8240 9214@smallexample
c906108c
SS
9215(@value{GDBP}) whatis width
9216type = double
9217(@value{GDBP}) p width
9218$4 = 13
9219(@value{GDBP}) set width=47
9220Invalid syntax in expression.
474c8240 9221@end smallexample
c906108c
SS
9222
9223@noindent
9224The invalid expression, of course, is @samp{=47}. In
9225order to actually set the program's variable @code{width}, use
9226
474c8240 9227@smallexample
c906108c 9228(@value{GDBP}) set var width=47
474c8240 9229@end smallexample
53a5351d 9230
c906108c
SS
9231Because the @code{set} command has many subcommands that can conflict
9232with the names of program variables, it is a good idea to use the
9233@code{set variable} command instead of just @code{set}. For example, if
9234your program has a variable @code{g}, you run into problems if you try
9235to set a new value with just @samp{set g=4}, because @value{GDBN} has
9236the command @code{set gnutarget}, abbreviated @code{set g}:
9237
474c8240 9238@smallexample
c906108c
SS
9239@group
9240(@value{GDBP}) whatis g
9241type = double
9242(@value{GDBP}) p g
9243$1 = 1
9244(@value{GDBP}) set g=4
2df3850c 9245(@value{GDBP}) p g
c906108c
SS
9246$2 = 1
9247(@value{GDBP}) r
9248The program being debugged has been started already.
9249Start it from the beginning? (y or n) y
9250Starting program: /home/smith/cc_progs/a.out
6d2ebf8b
SS
9251"/home/smith/cc_progs/a.out": can't open to read symbols:
9252 Invalid bfd target.
c906108c
SS
9253(@value{GDBP}) show g
9254The current BFD target is "=4".
9255@end group
474c8240 9256@end smallexample
c906108c
SS
9257
9258@noindent
9259The program variable @code{g} did not change, and you silently set the
9260@code{gnutarget} to an invalid value. In order to set the variable
9261@code{g}, use
9262
474c8240 9263@smallexample
c906108c 9264(@value{GDBP}) set var g=4
474c8240 9265@end smallexample
c906108c
SS
9266
9267@value{GDBN} allows more implicit conversions in assignments than C; you can
9268freely store an integer value into a pointer variable or vice versa,
9269and you can convert any structure to any other structure that is the
9270same length or shorter.
9271@comment FIXME: how do structs align/pad in these conversions?
9272@comment /doc@cygnus.com 18dec1990
9273
9274To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9275construct to generate a value of specified type at a specified address
9276(@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9277to memory location @code{0x83040} as an integer (which implies a certain size
9278and representation in memory), and
9279
474c8240 9280@smallexample
c906108c 9281set @{int@}0x83040 = 4
474c8240 9282@end smallexample
c906108c
SS
9283
9284@noindent
9285stores the value 4 into that memory location.
9286
6d2ebf8b 9287@node Jumping
c906108c
SS
9288@section Continuing at a different address
9289
9290Ordinarily, when you continue your program, you do so at the place where
9291it stopped, with the @code{continue} command. You can instead continue at
9292an address of your own choosing, with the following commands:
9293
9294@table @code
9295@kindex jump
9296@item jump @var{linespec}
9297Resume execution at line @var{linespec}. Execution stops again
9298immediately if there is a breakpoint there. @xref{List, ,Printing
9299source lines}, for a description of the different forms of
9300@var{linespec}. It is common practice to use the @code{tbreak} command
9301in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9302breakpoints}.
9303
9304The @code{jump} command does not change the current stack frame, or
9305the stack pointer, or the contents of any memory location or any
9306register other than the program counter. If line @var{linespec} is in
9307a different function from the one currently executing, the results may
9308be bizarre if the two functions expect different patterns of arguments or
9309of local variables. For this reason, the @code{jump} command requests
9310confirmation if the specified line is not in the function currently
9311executing. However, even bizarre results are predictable if you are
9312well acquainted with the machine-language code of your program.
9313
9314@item jump *@var{address}
9315Resume execution at the instruction at address @var{address}.
9316@end table
9317
c906108c 9318@c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
53a5351d
JM
9319On many systems, you can get much the same effect as the @code{jump}
9320command by storing a new value into the register @code{$pc}. The
9321difference is that this does not start your program running; it only
9322changes the address of where it @emph{will} run when you continue. For
9323example,
c906108c 9324
474c8240 9325@smallexample
c906108c 9326set $pc = 0x485
474c8240 9327@end smallexample
c906108c
SS
9328
9329@noindent
9330makes the next @code{continue} command or stepping command execute at
9331address @code{0x485}, rather than at the address where your program stopped.
9332@xref{Continuing and Stepping, ,Continuing and stepping}.
c906108c
SS
9333
9334The most common occasion to use the @code{jump} command is to back
9335up---perhaps with more breakpoints set---over a portion of a program
9336that has already executed, in order to examine its execution in more
9337detail.
9338
c906108c 9339@c @group
6d2ebf8b 9340@node Signaling
c906108c
SS
9341@section Giving your program a signal
9342
9343@table @code
9344@kindex signal
9345@item signal @var{signal}
9346Resume execution where your program stopped, but immediately give it the
9347signal @var{signal}. @var{signal} can be the name or the number of a
9348signal. For example, on many systems @code{signal 2} and @code{signal
9349SIGINT} are both ways of sending an interrupt signal.
9350
9351Alternatively, if @var{signal} is zero, continue execution without
9352giving a signal. This is useful when your program stopped on account of
9353a signal and would ordinary see the signal when resumed with the
9354@code{continue} command; @samp{signal 0} causes it to resume without a
9355signal.
9356
9357@code{signal} does not repeat when you press @key{RET} a second time
9358after executing the command.
9359@end table
9360@c @end group
9361
9362Invoking the @code{signal} command is not the same as invoking the
9363@code{kill} utility from the shell. Sending a signal with @code{kill}
9364causes @value{GDBN} to decide what to do with the signal depending on
9365the signal handling tables (@pxref{Signals}). The @code{signal} command
9366passes the signal directly to your program.
9367
c906108c 9368
6d2ebf8b 9369@node Returning
c906108c
SS
9370@section Returning from a function
9371
9372@table @code
9373@cindex returning from a function
9374@kindex return
9375@item return
9376@itemx return @var{expression}
9377You can cancel execution of a function call with the @code{return}
9378command. If you give an
9379@var{expression} argument, its value is used as the function's return
9380value.
9381@end table
9382
9383When you use @code{return}, @value{GDBN} discards the selected stack frame
9384(and all frames within it). You can think of this as making the
9385discarded frame return prematurely. If you wish to specify a value to
9386be returned, give that value as the argument to @code{return}.
9387
9388This pops the selected stack frame (@pxref{Selection, ,Selecting a
9389frame}), and any other frames inside of it, leaving its caller as the
9390innermost remaining frame. That frame becomes selected. The
9391specified value is stored in the registers used for returning values
9392of functions.
9393
9394The @code{return} command does not resume execution; it leaves the
9395program stopped in the state that would exist if the function had just
9396returned. In contrast, the @code{finish} command (@pxref{Continuing
9397and Stepping, ,Continuing and stepping}) resumes execution until the
9398selected stack frame returns naturally.
9399
6d2ebf8b 9400@node Calling
c906108c
SS
9401@section Calling program functions
9402
9403@cindex calling functions
9404@kindex call
9405@table @code
9406@item call @var{expr}
9407Evaluate the expression @var{expr} without displaying @code{void}
9408returned values.
9409@end table
9410
9411You can use this variant of the @code{print} command if you want to
9412execute a function from your program, but without cluttering the output
5d161b24
DB
9413with @code{void} returned values. If the result is not void, it
9414is printed and saved in the value history.
c906108c 9415
6d2ebf8b 9416@node Patching
c906108c 9417@section Patching programs
7a292a7a 9418
c906108c
SS
9419@cindex patching binaries
9420@cindex writing into executables
c906108c 9421@cindex writing into corefiles
c906108c 9422
7a292a7a
SS
9423By default, @value{GDBN} opens the file containing your program's
9424executable code (or the corefile) read-only. This prevents accidental
9425alterations to machine code; but it also prevents you from intentionally
9426patching your program's binary.
c906108c
SS
9427
9428If you'd like to be able to patch the binary, you can specify that
9429explicitly with the @code{set write} command. For example, you might
9430want to turn on internal debugging flags, or even to make emergency
9431repairs.
9432
9433@table @code
9434@kindex set write
9435@item set write on
9436@itemx set write off
7a292a7a
SS
9437If you specify @samp{set write on}, @value{GDBN} opens executable and
9438core files for both reading and writing; if you specify @samp{set write
c906108c
SS
9439off} (the default), @value{GDBN} opens them read-only.
9440
9441If you have already loaded a file, you must load it again (using the
7a292a7a
SS
9442@code{exec-file} or @code{core-file} command) after changing @code{set
9443write}, for your new setting to take effect.
c906108c
SS
9444
9445@item show write
9446@kindex show write
7a292a7a
SS
9447Display whether executable files and core files are opened for writing
9448as well as reading.
c906108c
SS
9449@end table
9450
6d2ebf8b 9451@node GDB Files
c906108c
SS
9452@chapter @value{GDBN} Files
9453
7a292a7a
SS
9454@value{GDBN} needs to know the file name of the program to be debugged,
9455both in order to read its symbol table and in order to start your
9456program. To debug a core dump of a previous run, you must also tell
9457@value{GDBN} the name of the core dump file.
c906108c
SS
9458
9459@menu
9460* Files:: Commands to specify files
9461* Symbol Errors:: Errors reading symbol files
9462@end menu
9463
6d2ebf8b 9464@node Files
c906108c 9465@section Commands to specify files
c906108c 9466
7a292a7a 9467@cindex symbol table
c906108c 9468@cindex core dump file
7a292a7a
SS
9469
9470You may want to specify executable and core dump file names. The usual
9471way to do this is at start-up time, using the arguments to
9472@value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9473Out of @value{GDBN}}).
c906108c
SS
9474
9475Occasionally it is necessary to change to a different file during a
9476@value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9477a file you want to use. In these situations the @value{GDBN} commands
9478to specify new files are useful.
9479
9480@table @code
9481@cindex executable file
9482@kindex file
9483@item file @var{filename}
9484Use @var{filename} as the program to be debugged. It is read for its
9485symbols and for the contents of pure memory. It is also the program
9486executed when you use the @code{run} command. If you do not specify a
5d161b24
DB
9487directory and the file is not found in the @value{GDBN} working directory,
9488@value{GDBN} uses the environment variable @code{PATH} as a list of
9489directories to search, just as the shell does when looking for a program
9490to run. You can change the value of this variable, for both @value{GDBN}
c906108c
SS
9491and your program, using the @code{path} command.
9492
6d2ebf8b 9493On systems with memory-mapped files, an auxiliary file named
c906108c
SS
9494@file{@var{filename}.syms} may hold symbol table information for
9495@var{filename}. If so, @value{GDBN} maps in the symbol table from
9496@file{@var{filename}.syms}, starting up more quickly. See the
9497descriptions of the file options @samp{-mapped} and @samp{-readnow}
9498(available on the command line, and with the commands @code{file},
5d161b24 9499@code{symbol-file}, or @code{add-symbol-file}, described below),
c906108c 9500for more information.
c906108c
SS
9501
9502@item file
9503@code{file} with no argument makes @value{GDBN} discard any information it
9504has on both executable file and the symbol table.
9505
9506@kindex exec-file
9507@item exec-file @r{[} @var{filename} @r{]}
9508Specify that the program to be run (but not the symbol table) is found
9509in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9510if necessary to locate your program. Omitting @var{filename} means to
9511discard information on the executable file.
9512
9513@kindex symbol-file
9514@item symbol-file @r{[} @var{filename} @r{]}
9515Read symbol table information from file @var{filename}. @code{PATH} is
9516searched when necessary. Use the @code{file} command to get both symbol
9517table and program to run from the same file.
9518
9519@code{symbol-file} with no argument clears out @value{GDBN} information on your
9520program's symbol table.
9521
5d161b24 9522The @code{symbol-file} command causes @value{GDBN} to forget the contents
c906108c
SS
9523of its convenience variables, the value history, and all breakpoints and
9524auto-display expressions. This is because they may contain pointers to
9525the internal data recording symbols and data types, which are part of
9526the old symbol table data being discarded inside @value{GDBN}.
9527
9528@code{symbol-file} does not repeat if you press @key{RET} again after
9529executing it once.
9530
9531When @value{GDBN} is configured for a particular environment, it
9532understands debugging information in whatever format is the standard
9533generated for that environment; you may use either a @sc{gnu} compiler, or
9534other compilers that adhere to the local conventions.
c906108c
SS
9535Best results are usually obtained from @sc{gnu} compilers; for example,
9536using @code{@value{GCC}} you can generate debugging information for
9537optimized code.
c906108c
SS
9538
9539For most kinds of object files, with the exception of old SVR3 systems
9540using COFF, the @code{symbol-file} command does not normally read the
9541symbol table in full right away. Instead, it scans the symbol table
9542quickly to find which source files and which symbols are present. The
9543details are read later, one source file at a time, as they are needed.
9544
9545The purpose of this two-stage reading strategy is to make @value{GDBN}
9546start up faster. For the most part, it is invisible except for
9547occasional pauses while the symbol table details for a particular source
9548file are being read. (The @code{set verbose} command can turn these
9549pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9550warnings and messages}.)
9551
c906108c
SS
9552We have not implemented the two-stage strategy for COFF yet. When the
9553symbol table is stored in COFF format, @code{symbol-file} reads the
9554symbol table data in full right away. Note that ``stabs-in-COFF''
9555still does the two-stage strategy, since the debug info is actually
9556in stabs format.
9557
9558@kindex readnow
9559@cindex reading symbols immediately
9560@cindex symbols, reading immediately
9561@kindex mapped
9562@cindex memory-mapped symbol file
9563@cindex saving symbol table
9564@item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9565@itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9566You can override the @value{GDBN} two-stage strategy for reading symbol
9567tables by using the @samp{-readnow} option with any of the commands that
9568load symbol table information, if you want to be sure @value{GDBN} has the
5d161b24 9569entire symbol table available.
c906108c 9570
c906108c
SS
9571If memory-mapped files are available on your system through the
9572@code{mmap} system call, you can use another option, @samp{-mapped}, to
9573cause @value{GDBN} to write the symbols for your program into a reusable
9574file. Future @value{GDBN} debugging sessions map in symbol information
9575from this auxiliary symbol file (if the program has not changed), rather
9576than spending time reading the symbol table from the executable
9577program. Using the @samp{-mapped} option has the same effect as
9578starting @value{GDBN} with the @samp{-mapped} command-line option.
9579
9580You can use both options together, to make sure the auxiliary symbol
9581file has all the symbol information for your program.
9582
9583The auxiliary symbol file for a program called @var{myprog} is called
9584@samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9585than the corresponding executable), @value{GDBN} always attempts to use
9586it when you debug @var{myprog}; no special options or commands are
9587needed.
9588
9589The @file{.syms} file is specific to the host machine where you run
9590@value{GDBN}. It holds an exact image of the internal @value{GDBN}
9591symbol table. It cannot be shared across multiple host platforms.
c906108c
SS
9592
9593@c FIXME: for now no mention of directories, since this seems to be in
9594@c flux. 13mar1992 status is that in theory GDB would look either in
9595@c current dir or in same dir as myprog; but issues like competing
9596@c GDB's, or clutter in system dirs, mean that in practice right now
9597@c only current dir is used. FFish says maybe a special GDB hierarchy
9598@c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9599@c files.
9600
9601@kindex core
9602@kindex core-file
9603@item core-file @r{[} @var{filename} @r{]}
9604Specify the whereabouts of a core dump file to be used as the ``contents
9605of memory''. Traditionally, core files contain only some parts of the
9606address space of the process that generated them; @value{GDBN} can access the
9607executable file itself for other parts.
9608
9609@code{core-file} with no argument specifies that no core file is
9610to be used.
9611
9612Note that the core file is ignored when your program is actually running
7a292a7a
SS
9613under @value{GDBN}. So, if you have been running your program and you
9614wish to debug a core file instead, you must kill the subprocess in which
9615the program is running. To do this, use the @code{kill} command
c906108c 9616(@pxref{Kill Process, ,Killing the child process}).
c906108c 9617
c906108c
SS
9618@kindex add-symbol-file
9619@cindex dynamic linking
9620@item add-symbol-file @var{filename} @var{address}
9621@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
17d9d558 9622@itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
96a2c332
SS
9623The @code{add-symbol-file} command reads additional symbol table
9624information from the file @var{filename}. You would use this command
9625when @var{filename} has been dynamically loaded (by some other means)
9626into the program that is running. @var{address} should be the memory
9627address at which the file has been loaded; @value{GDBN} cannot figure
d167840f
EZ
9628this out for itself. You can additionally specify an arbitrary number
9629of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9630section name and base address for that section. You can specify any
9631@var{address} as an expression.
c906108c
SS
9632
9633The symbol table of the file @var{filename} is added to the symbol table
9634originally read with the @code{symbol-file} command. You can use the
96a2c332
SS
9635@code{add-symbol-file} command any number of times; the new symbol data
9636thus read keeps adding to the old. To discard all old symbol data
9637instead, use the @code{symbol-file} command without any arguments.
c906108c 9638
17d9d558
JB
9639@cindex relocatable object files, reading symbols from
9640@cindex object files, relocatable, reading symbols from
9641@cindex reading symbols from relocatable object files
9642@cindex symbols, reading from relocatable object files
9643@cindex @file{.o} files, reading symbols from
9644Although @var{filename} is typically a shared library file, an
9645executable file, or some other object file which has been fully
9646relocated for loading into a process, you can also load symbolic
9647information from relocatable @file{.o} files, as long as:
9648
9649@itemize @bullet
9650@item
9651the file's symbolic information refers only to linker symbols defined in
9652that file, not to symbols defined by other object files,
9653@item
9654every section the file's symbolic information refers to has actually
9655been loaded into the inferior, as it appears in the file, and
9656@item
9657you can determine the address at which every section was loaded, and
9658provide these to the @code{add-symbol-file} command.
9659@end itemize
9660
9661@noindent
9662Some embedded operating systems, like Sun Chorus and VxWorks, can load
9663relocatable files into an already running program; such systems
9664typically make the requirements above easy to meet. However, it's
9665important to recognize that many native systems use complex link
9666procedures (@code{.linkonce} section factoring and C++ constructor table
9667assembly, for example) that make the requirements difficult to meet. In
9668general, one cannot assume that using @code{add-symbol-file} to read a
9669relocatable object file's symbolic information will have the same effect
9670as linking the relocatable object file into the program in the normal
9671way.
9672
c906108c
SS
9673@code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9674
9675You can use the @samp{-mapped} and @samp{-readnow} options just as with
9676the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9677table information for @var{filename}.
9678
9679@kindex add-shared-symbol-file
9680@item add-shared-symbol-file
9681The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
5d161b24
DB
9682operating system for the Motorola 88k. @value{GDBN} automatically looks for
9683shared libraries, however if @value{GDBN} does not find yours, you can run
c906108c 9684@code{add-shared-symbol-file}. It takes no arguments.
c906108c 9685
c906108c
SS
9686@kindex section
9687@item section
5d161b24
DB
9688The @code{section} command changes the base address of section SECTION of
9689the exec file to ADDR. This can be used if the exec file does not contain
9690section addresses, (such as in the a.out format), or when the addresses
9691specified in the file itself are wrong. Each section must be changed
d4f3574e
SS
9692separately. The @code{info files} command, described below, lists all
9693the sections and their addresses.
c906108c
SS
9694
9695@kindex info files
9696@kindex info target
9697@item info files
9698@itemx info target
7a292a7a
SS
9699@code{info files} and @code{info target} are synonymous; both print the
9700current target (@pxref{Targets, ,Specifying a Debugging Target}),
9701including the names of the executable and core dump files currently in
9702use by @value{GDBN}, and the files from which symbols were loaded. The
9703command @code{help target} lists all possible targets rather than
9704current ones.
9705
fe95c787
MS
9706@kindex maint info sections
9707@item maint info sections
9708Another command that can give you extra information about program sections
9709is @code{maint info sections}. In addition to the section information
9710displayed by @code{info files}, this command displays the flags and file
9711offset of each section in the executable and core dump files. In addition,
9712@code{maint info sections} provides the following command options (which
9713may be arbitrarily combined):
9714
9715@table @code
9716@item ALLOBJ
9717Display sections for all loaded object files, including shared libraries.
9718@item @var{sections}
6600abed 9719Display info only for named @var{sections}.
fe95c787
MS
9720@item @var{section-flags}
9721Display info only for sections for which @var{section-flags} are true.
9722The section flags that @value{GDBN} currently knows about are:
9723@table @code
9724@item ALLOC
9725Section will have space allocated in the process when loaded.
9726Set for all sections except those containing debug information.
9727@item LOAD
9728Section will be loaded from the file into the child process memory.
9729Set for pre-initialized code and data, clear for @code{.bss} sections.
9730@item RELOC
9731Section needs to be relocated before loading.
9732@item READONLY
9733Section cannot be modified by the child process.
9734@item CODE
9735Section contains executable code only.
6600abed 9736@item DATA
fe95c787
MS
9737Section contains data only (no executable code).
9738@item ROM
9739Section will reside in ROM.
9740@item CONSTRUCTOR
9741Section contains data for constructor/destructor lists.
9742@item HAS_CONTENTS
9743Section is not empty.
9744@item NEVER_LOAD
9745An instruction to the linker to not output the section.
9746@item COFF_SHARED_LIBRARY
9747A notification to the linker that the section contains
9748COFF shared library information.
9749@item IS_COMMON
9750Section contains common symbols.
9751@end table
9752@end table
6763aef9
MS
9753@kindex set trust-readonly-sections
9754@item set trust-readonly-sections on
9755Tell @value{GDBN} that readonly sections in your object file
6ca652b0 9756really are read-only (i.e.@: that their contents will not change).
6763aef9
MS
9757In that case, @value{GDBN} can fetch values from these sections
9758out of the object file, rather than from the target program.
9759For some targets (notably embedded ones), this can be a significant
9760enhancement to debugging performance.
9761
9762The default is off.
9763
9764@item set trust-readonly-sections off
15110bc3 9765Tell @value{GDBN} not to trust readonly sections. This means that
6763aef9
MS
9766the contents of the section might change while the program is running,
9767and must therefore be fetched from the target when needed.
c906108c
SS
9768@end table
9769
9770All file-specifying commands allow both absolute and relative file names
9771as arguments. @value{GDBN} always converts the file name to an absolute file
9772name and remembers it that way.
9773
c906108c 9774@cindex shared libraries
c906108c
SS
9775@value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9776libraries.
53a5351d 9777
c906108c
SS
9778@value{GDBN} automatically loads symbol definitions from shared libraries
9779when you use the @code{run} command, or when you examine a core file.
9780(Before you issue the @code{run} command, @value{GDBN} does not understand
9781references to a function in a shared library, however---unless you are
9782debugging a core file).
53a5351d
JM
9783
9784On HP-UX, if the program loads a library explicitly, @value{GDBN}
9785automatically loads the symbols at the time of the @code{shl_load} call.
9786
c906108c
SS
9787@c FIXME: some @value{GDBN} release may permit some refs to undef
9788@c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9789@c FIXME...lib; check this from time to time when updating manual
9790
b7209cb4
FF
9791There are times, however, when you may wish to not automatically load
9792symbol definitions from shared libraries, such as when they are
9793particularly large or there are many of them.
9794
9795To control the automatic loading of shared library symbols, use the
9796commands:
9797
9798@table @code
9799@kindex set auto-solib-add
9800@item set auto-solib-add @var{mode}
9801If @var{mode} is @code{on}, symbols from all shared object libraries
9802will be loaded automatically when the inferior begins execution, you
9803attach to an independently started inferior, or when the dynamic linker
9804informs @value{GDBN} that a new library has been loaded. If @var{mode}
9805is @code{off}, symbols must be loaded manually, using the
9806@code{sharedlibrary} command. The default value is @code{on}.
9807
9808@kindex show auto-solib-add
9809@item show auto-solib-add
9810Display the current autoloading mode.
9811@end table
9812
9813To explicitly load shared library symbols, use the @code{sharedlibrary}
9814command:
9815
c906108c
SS
9816@table @code
9817@kindex info sharedlibrary
9818@kindex info share
9819@item info share
9820@itemx info sharedlibrary
9821Print the names of the shared libraries which are currently loaded.
9822
9823@kindex sharedlibrary
9824@kindex share
9825@item sharedlibrary @var{regex}
9826@itemx share @var{regex}
c906108c
SS
9827Load shared object library symbols for files matching a
9828Unix regular expression.
9829As with files loaded automatically, it only loads shared libraries
9830required by your program for a core file or after typing @code{run}. If
9831@var{regex} is omitted all shared libraries required by your program are
9832loaded.
9833@end table
9834
b7209cb4
FF
9835On some systems, such as HP-UX systems, @value{GDBN} supports
9836autoloading shared library symbols until a limiting threshold size is
9837reached. This provides the benefit of allowing autoloading to remain on
9838by default, but avoids autoloading excessively large shared libraries,
9839up to a threshold that is initially set, but which you can modify if you
9840wish.
c906108c
SS
9841
9842Beyond that threshold, symbols from shared libraries must be explicitly
d4f3574e
SS
9843loaded. To load these symbols, use the command @code{sharedlibrary
9844@var{filename}}. The base address of the shared library is determined
c906108c
SS
9845automatically by @value{GDBN} and need not be specified.
9846
9847To display or set the threshold, use the commands:
9848
9849@table @code
b7209cb4
FF
9850@kindex set auto-solib-limit
9851@item set auto-solib-limit @var{threshold}
9852Set the autoloading size threshold, in an integral number of megabytes.
9853If @var{threshold} is nonzero and shared library autoloading is enabled,
9854symbols from all shared object libraries will be loaded until the total
9855size of the loaded shared library symbols exceeds this threshold.
c906108c 9856Otherwise, symbols must be loaded manually, using the
6ca652b0 9857@code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
b7209cb4 9858Mb).
c906108c 9859
b7209cb4
FF
9860@kindex show auto-solib-limit
9861@item show auto-solib-limit
c906108c
SS
9862Display the current autoloading size threshold, in megabytes.
9863@end table
c906108c 9864
6d2ebf8b 9865@node Symbol Errors
c906108c
SS
9866@section Errors reading symbol files
9867
9868While reading a symbol file, @value{GDBN} occasionally encounters problems,
9869such as symbol types it does not recognize, or known bugs in compiler
9870output. By default, @value{GDBN} does not notify you of such problems, since
9871they are relatively common and primarily of interest to people
9872debugging compilers. If you are interested in seeing information
9873about ill-constructed symbol tables, you can either ask @value{GDBN} to print
9874only one message about each such type of problem, no matter how many
9875times the problem occurs; or you can ask @value{GDBN} to print more messages,
9876to see how many times the problems occur, with the @code{set
9877complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
9878messages}).
9879
9880The messages currently printed, and their meanings, include:
9881
9882@table @code
9883@item inner block not inside outer block in @var{symbol}
9884
9885The symbol information shows where symbol scopes begin and end
9886(such as at the start of a function or a block of statements). This
9887error indicates that an inner scope block is not fully contained
9888in its outer scope blocks.
9889
9890@value{GDBN} circumvents the problem by treating the inner block as if it had
9891the same scope as the outer block. In the error message, @var{symbol}
9892may be shown as ``@code{(don't know)}'' if the outer block is not a
9893function.
9894
9895@item block at @var{address} out of order
9896
9897The symbol information for symbol scope blocks should occur in
9898order of increasing addresses. This error indicates that it does not
9899do so.
9900
9901@value{GDBN} does not circumvent this problem, and has trouble
9902locating symbols in the source file whose symbols it is reading. (You
9903can often determine what source file is affected by specifying
9904@code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
9905messages}.)
9906
9907@item bad block start address patched
9908
9909The symbol information for a symbol scope block has a start address
9910smaller than the address of the preceding source line. This is known
9911to occur in the SunOS 4.1.1 (and earlier) C compiler.
9912
9913@value{GDBN} circumvents the problem by treating the symbol scope block as
9914starting on the previous source line.
9915
9916@item bad string table offset in symbol @var{n}
9917
9918@cindex foo
9919Symbol number @var{n} contains a pointer into the string table which is
9920larger than the size of the string table.
9921
9922@value{GDBN} circumvents the problem by considering the symbol to have the
9923name @code{foo}, which may cause other problems if many symbols end up
9924with this name.
9925
9926@item unknown symbol type @code{0x@var{nn}}
9927
7a292a7a
SS
9928The symbol information contains new data types that @value{GDBN} does
9929not yet know how to read. @code{0x@var{nn}} is the symbol type of the
d4f3574e 9930uncomprehended information, in hexadecimal.
c906108c 9931
7a292a7a
SS
9932@value{GDBN} circumvents the error by ignoring this symbol information.
9933This usually allows you to debug your program, though certain symbols
c906108c 9934are not accessible. If you encounter such a problem and feel like
7a292a7a
SS
9935debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
9936on @code{complain}, then go up to the function @code{read_dbx_symtab}
9937and examine @code{*bufp} to see the symbol.
c906108c
SS
9938
9939@item stub type has NULL name
c906108c 9940
7a292a7a 9941@value{GDBN} could not find the full definition for a struct or class.
c906108c 9942
7a292a7a 9943@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
b37052ae 9944The symbol information for a C@t{++} member function is missing some
7a292a7a
SS
9945information that recent versions of the compiler should have output for
9946it.
c906108c
SS
9947
9948@item info mismatch between compiler and debugger
9949
9950@value{GDBN} could not parse a type specification output by the compiler.
7a292a7a 9951
c906108c
SS
9952@end table
9953
6d2ebf8b 9954@node Targets
c906108c 9955@chapter Specifying a Debugging Target
7a292a7a 9956
c906108c
SS
9957@cindex debugging target
9958@kindex target
9959
9960A @dfn{target} is the execution environment occupied by your program.
53a5351d
JM
9961
9962Often, @value{GDBN} runs in the same host environment as your program;
9963in that case, the debugging target is specified as a side effect when
9964you use the @code{file} or @code{core} commands. When you need more
c906108c
SS
9965flexibility---for example, running @value{GDBN} on a physically separate
9966host, or controlling a standalone system over a serial port or a
53a5351d
JM
9967realtime system over a TCP/IP connection---you can use the @code{target}
9968command to specify one of the target types configured for @value{GDBN}
9969(@pxref{Target Commands, ,Commands for managing targets}).
c906108c
SS
9970
9971@menu
9972* Active Targets:: Active targets
9973* Target Commands:: Commands for managing targets
c906108c
SS
9974* Byte Order:: Choosing target byte order
9975* Remote:: Remote debugging
96baa820 9976* KOD:: Kernel Object Display
c906108c
SS
9977
9978@end menu
9979
6d2ebf8b 9980@node Active Targets
c906108c 9981@section Active targets
7a292a7a 9982
c906108c
SS
9983@cindex stacking targets
9984@cindex active targets
9985@cindex multiple targets
9986
c906108c 9987There are three classes of targets: processes, core files, and
7a292a7a
SS
9988executable files. @value{GDBN} can work concurrently on up to three
9989active targets, one in each class. This allows you to (for example)
9990start a process and inspect its activity without abandoning your work on
9991a core file.
c906108c
SS
9992
9993For example, if you execute @samp{gdb a.out}, then the executable file
9994@code{a.out} is the only active target. If you designate a core file as
9995well---presumably from a prior run that crashed and coredumped---then
9996@value{GDBN} has two active targets and uses them in tandem, looking
9997first in the corefile target, then in the executable file, to satisfy
9998requests for memory addresses. (Typically, these two classes of target
9999are complementary, since core files contain only a program's
10000read-write memory---variables and so on---plus machine status, while
10001executable files contain only the program text and initialized data.)
c906108c
SS
10002
10003When you type @code{run}, your executable file becomes an active process
7a292a7a
SS
10004target as well. When a process target is active, all @value{GDBN}
10005commands requesting memory addresses refer to that target; addresses in
10006an active core file or executable file target are obscured while the
10007process target is active.
c906108c 10008
7a292a7a
SS
10009Use the @code{core-file} and @code{exec-file} commands to select a new
10010core file or executable target (@pxref{Files, ,Commands to specify
c906108c 10011files}). To specify as a target a process that is already running, use
7a292a7a
SS
10012the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10013process}).
c906108c 10014
6d2ebf8b 10015@node Target Commands
c906108c
SS
10016@section Commands for managing targets
10017
10018@table @code
10019@item target @var{type} @var{parameters}
7a292a7a
SS
10020Connects the @value{GDBN} host environment to a target machine or
10021process. A target is typically a protocol for talking to debugging
10022facilities. You use the argument @var{type} to specify the type or
10023protocol of the target machine.
c906108c
SS
10024
10025Further @var{parameters} are interpreted by the target protocol, but
10026typically include things like device names or host names to connect
10027with, process numbers, and baud rates.
c906108c
SS
10028
10029The @code{target} command does not repeat if you press @key{RET} again
10030after executing the command.
10031
10032@kindex help target
10033@item help target
10034Displays the names of all targets available. To display targets
10035currently selected, use either @code{info target} or @code{info files}
10036(@pxref{Files, ,Commands to specify files}).
10037
10038@item help target @var{name}
10039Describe a particular target, including any parameters necessary to
10040select it.
10041
10042@kindex set gnutarget
10043@item set gnutarget @var{args}
5d161b24 10044@value{GDBN} uses its own library BFD to read your files. @value{GDBN}
c906108c 10045knows whether it is reading an @dfn{executable},
5d161b24
DB
10046a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10047with the @code{set gnutarget} command. Unlike most @code{target} commands,
c906108c
SS
10048with @code{gnutarget} the @code{target} refers to a program, not a machine.
10049
d4f3574e 10050@quotation
c906108c
SS
10051@emph{Warning:} To specify a file format with @code{set gnutarget},
10052you must know the actual BFD name.
d4f3574e 10053@end quotation
c906108c 10054
d4f3574e
SS
10055@noindent
10056@xref{Files, , Commands to specify files}.
c906108c 10057
5d161b24 10058@kindex show gnutarget
c906108c
SS
10059@item show gnutarget
10060Use the @code{show gnutarget} command to display what file format
10061@code{gnutarget} is set to read. If you have not set @code{gnutarget},
10062@value{GDBN} will determine the file format for each file automatically,
10063and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10064@end table
10065
c906108c
SS
10066Here are some common targets (available, or not, depending on the GDB
10067configuration):
c906108c
SS
10068
10069@table @code
10070@kindex target exec
10071@item target exec @var{program}
10072An executable file. @samp{target exec @var{program}} is the same as
10073@samp{exec-file @var{program}}.
10074
c906108c
SS
10075@kindex target core
10076@item target core @var{filename}
10077A core dump file. @samp{target core @var{filename}} is the same as
10078@samp{core-file @var{filename}}.
c906108c
SS
10079
10080@kindex target remote
10081@item target remote @var{dev}
10082Remote serial target in GDB-specific protocol. The argument @var{dev}
10083specifies what serial device to use for the connection (e.g.
10084@file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
d4f3574e 10085supports the @code{load} command. This is only useful if you have
c906108c
SS
10086some other way of getting the stub to the target system, and you can put
10087it somewhere in memory where it won't get clobbered by the download.
10088
c906108c
SS
10089@kindex target sim
10090@item target sim
2df3850c 10091Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
104c1213 10092In general,
474c8240 10093@smallexample
104c1213
JM
10094 target sim
10095 load
10096 run
474c8240 10097@end smallexample
d4f3574e 10098@noindent
104c1213 10099works; however, you cannot assume that a specific memory map, device
d4f3574e 10100drivers, or even basic I/O is available, although some simulators do
104c1213
JM
10101provide these. For info about any processor-specific simulator details,
10102see the appropriate section in @ref{Embedded Processors, ,Embedded
10103Processors}.
10104
c906108c
SS
10105@end table
10106
104c1213 10107Some configurations may include these targets as well:
c906108c
SS
10108
10109@table @code
10110
c906108c
SS
10111@kindex target nrom
10112@item target nrom @var{dev}
10113NetROM ROM emulator. This target only supports downloading.
10114
c906108c
SS
10115@end table
10116
5d161b24 10117Different targets are available on different configurations of @value{GDBN};
c906108c 10118your configuration may have more or fewer targets.
c906108c
SS
10119
10120Many remote targets require you to download the executable's code
10121once you've successfully established a connection.
10122
10123@table @code
10124
10125@kindex load @var{filename}
10126@item load @var{filename}
c906108c
SS
10127Depending on what remote debugging facilities are configured into
10128@value{GDBN}, the @code{load} command may be available. Where it exists, it
10129is meant to make @var{filename} (an executable) available for debugging
10130on the remote system---by downloading, or dynamic linking, for example.
10131@code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10132the @code{add-symbol-file} command.
10133
10134If your @value{GDBN} does not have a @code{load} command, attempting to
10135execute it gets the error message ``@code{You can't do that when your
10136target is @dots{}}''
c906108c
SS
10137
10138The file is loaded at whatever address is specified in the executable.
10139For some object file formats, you can specify the load address when you
10140link the program; for other formats, like a.out, the object file format
10141specifies a fixed address.
10142@c FIXME! This would be a good place for an xref to the GNU linker doc.
10143
c906108c
SS
10144@code{load} does not repeat if you press @key{RET} again after using it.
10145@end table
10146
6d2ebf8b 10147@node Byte Order
c906108c 10148@section Choosing target byte order
7a292a7a 10149
c906108c
SS
10150@cindex choosing target byte order
10151@cindex target byte order
c906108c
SS
10152
10153Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10154offer the ability to run either big-endian or little-endian byte
10155orders. Usually the executable or symbol will include a bit to
10156designate the endian-ness, and you will not need to worry about
10157which to use. However, you may still find it useful to adjust
d4f3574e 10158@value{GDBN}'s idea of processor endian-ness manually.
c906108c
SS
10159
10160@table @code
10161@kindex set endian big
10162@item set endian big
10163Instruct @value{GDBN} to assume the target is big-endian.
10164
10165@kindex set endian little
10166@item set endian little
10167Instruct @value{GDBN} to assume the target is little-endian.
10168
10169@kindex set endian auto
10170@item set endian auto
10171Instruct @value{GDBN} to use the byte order associated with the
10172executable.
10173
10174@item show endian
10175Display @value{GDBN}'s current idea of the target byte order.
10176
10177@end table
10178
10179Note that these commands merely adjust interpretation of symbolic
10180data on the host, and that they have absolutely no effect on the
10181target system.
10182
6d2ebf8b 10183@node Remote
c906108c
SS
10184@section Remote debugging
10185@cindex remote debugging
10186
10187If you are trying to debug a program running on a machine that cannot run
5d161b24
DB
10188@value{GDBN} in the usual way, it is often useful to use remote debugging.
10189For example, you might use remote debugging on an operating system kernel,
c906108c
SS
10190or on a small system which does not have a general purpose operating system
10191powerful enough to run a full-featured debugger.
10192
10193Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10194to make this work with particular debugging targets. In addition,
5d161b24 10195@value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
c906108c
SS
10196but not specific to any particular target system) which you can use if you
10197write the remote stubs---the code that runs on the remote system to
10198communicate with @value{GDBN}.
10199
10200Other remote targets may be available in your
10201configuration of @value{GDBN}; use @code{help target} to list them.
c906108c 10202
6f05cf9f
AC
10203@node KOD
10204@section Kernel Object Display
10205
10206@cindex kernel object display
10207@cindex kernel object
10208@cindex KOD
10209
10210Some targets support kernel object display. Using this facility,
10211@value{GDBN} communicates specially with the underlying operating system
10212and can display information about operating system-level objects such as
10213mutexes and other synchronization objects. Exactly which objects can be
10214displayed is determined on a per-OS basis.
10215
10216Use the @code{set os} command to set the operating system. This tells
10217@value{GDBN} which kernel object display module to initialize:
10218
474c8240 10219@smallexample
6f05cf9f 10220(@value{GDBP}) set os cisco
474c8240 10221@end smallexample
6f05cf9f
AC
10222
10223If @code{set os} succeeds, @value{GDBN} will display some information
10224about the operating system, and will create a new @code{info} command
10225which can be used to query the target. The @code{info} command is named
10226after the operating system:
c906108c 10227
474c8240 10228@smallexample
6f05cf9f
AC
10229(@value{GDBP}) info cisco
10230List of Cisco Kernel Objects
10231Object Description
10232any Any and all objects
474c8240 10233@end smallexample
6f05cf9f
AC
10234
10235Further subcommands can be used to query about particular objects known
10236by the kernel.
10237
10238There is currently no way to determine whether a given operating system
10239is supported other than to try it.
10240
10241
10242@node Remote Debugging
10243@chapter Debugging remote programs
10244
6b2f586d
AC
10245@menu
10246* Server:: Using the gdbserver program
10247* NetWare:: Using the gdbserve.nlm program
10248* remote stub:: Implementing a remote stub
6b2f586d
AC
10249@end menu
10250
6f05cf9f
AC
10251@node Server
10252@section Using the @code{gdbserver} program
10253
10254@kindex gdbserver
10255@cindex remote connection without stubs
10256@code{gdbserver} is a control program for Unix-like systems, which
10257allows you to connect your program with a remote @value{GDBN} via
10258@code{target remote}---but without linking in the usual debugging stub.
10259
10260@code{gdbserver} is not a complete replacement for the debugging stubs,
10261because it requires essentially the same operating-system facilities
10262that @value{GDBN} itself does. In fact, a system that can run
10263@code{gdbserver} to connect to a remote @value{GDBN} could also run
10264@value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10265because it is a much smaller program than @value{GDBN} itself. It is
10266also easier to port than all of @value{GDBN}, so you may be able to get
10267started more quickly on a new system by using @code{gdbserver}.
10268Finally, if you develop code for real-time systems, you may find that
10269the tradeoffs involved in real-time operation make it more convenient to
10270do as much development work as possible on another system, for example
10271by cross-compiling. You can use @code{gdbserver} to make a similar
10272choice for debugging.
10273
10274@value{GDBN} and @code{gdbserver} communicate via either a serial line
10275or a TCP connection, using the standard @value{GDBN} remote serial
10276protocol.
10277
10278@table @emph
10279@item On the target machine,
10280you need to have a copy of the program you want to debug.
10281@code{gdbserver} does not need your program's symbol table, so you can
10282strip the program if necessary to save space. @value{GDBN} on the host
10283system does all the symbol handling.
10284
10285To use the server, you must tell it how to communicate with @value{GDBN};
56460a61 10286the name of your program; and the arguments for your program. The usual
6f05cf9f
AC
10287syntax is:
10288
10289@smallexample
10290target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10291@end smallexample
10292
10293@var{comm} is either a device name (to use a serial line) or a TCP
10294hostname and portnumber. For example, to debug Emacs with the argument
10295@samp{foo.txt} and communicate with @value{GDBN} over the serial port
10296@file{/dev/com1}:
10297
10298@smallexample
10299target> gdbserver /dev/com1 emacs foo.txt
10300@end smallexample
10301
10302@code{gdbserver} waits passively for the host @value{GDBN} to communicate
10303with it.
10304
10305To use a TCP connection instead of a serial line:
10306
10307@smallexample
10308target> gdbserver host:2345 emacs foo.txt
10309@end smallexample
10310
10311The only difference from the previous example is the first argument,
10312specifying that you are communicating with the host @value{GDBN} via
10313TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10314expect a TCP connection from machine @samp{host} to local TCP port 2345.
10315(Currently, the @samp{host} part is ignored.) You can choose any number
10316you want for the port number as long as it does not conflict with any
10317TCP ports already in use on the target system (for example, @code{23} is
10318reserved for @code{telnet}).@footnote{If you choose a port number that
10319conflicts with another service, @code{gdbserver} prints an error message
10320and exits.} You must use the same port number with the host @value{GDBN}
10321@code{target remote} command.
10322
56460a61
DJ
10323On some targets, @code{gdbserver} can also attach to running programs.
10324This is accomplished via the @code{--attach} argument. The syntax is:
10325
10326@smallexample
10327target> gdbserver @var{comm} --attach @var{pid}
10328@end smallexample
10329
10330@var{pid} is the process ID of a currently running process. It isn't necessary
10331to point @code{gdbserver} at a binary for the running process.
10332
6f05cf9f
AC
10333@item On the @value{GDBN} host machine,
10334you need an unstripped copy of your program, since @value{GDBN} needs
10335symbols and debugging information. Start up @value{GDBN} as usual,
10336using the name of the local copy of your program as the first argument.
10337(You may also need the @w{@samp{--baud}} option if the serial line is
10338running at anything other than 9600@dmn{bps}.) After that, use @code{target
10339remote} to establish communications with @code{gdbserver}. Its argument
10340is either a device name (usually a serial device, like
10341@file{/dev/ttyb}), or a TCP port descriptor in the form
10342@code{@var{host}:@var{PORT}}. For example:
10343
10344@smallexample
10345(@value{GDBP}) target remote /dev/ttyb
10346@end smallexample
10347
10348@noindent
10349communicates with the server via serial line @file{/dev/ttyb}, and
10350
10351@smallexample
10352(@value{GDBP}) target remote the-target:2345
10353@end smallexample
10354
10355@noindent
10356communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10357For TCP connections, you must start up @code{gdbserver} prior to using
10358the @code{target remote} command. Otherwise you may get an error whose
10359text depends on the host system, but which usually looks something like
10360@samp{Connection refused}.
10361@end table
10362
10363@node NetWare
10364@section Using the @code{gdbserve.nlm} program
10365
10366@kindex gdbserve.nlm
10367@code{gdbserve.nlm} is a control program for NetWare systems, which
10368allows you to connect your program with a remote @value{GDBN} via
10369@code{target remote}.
10370
10371@value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10372using the standard @value{GDBN} remote serial protocol.
10373
10374@table @emph
10375@item On the target machine,
10376you need to have a copy of the program you want to debug.
10377@code{gdbserve.nlm} does not need your program's symbol table, so you
10378can strip the program if necessary to save space. @value{GDBN} on the
10379host system does all the symbol handling.
10380
10381To use the server, you must tell it how to communicate with
10382@value{GDBN}; the name of your program; and the arguments for your
10383program. The syntax is:
10384
10385@smallexample
10386load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10387 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10388@end smallexample
10389
10390@var{board} and @var{port} specify the serial line; @var{baud} specifies
10391the baud rate used by the connection. @var{port} and @var{node} default
10392to 0, @var{baud} defaults to 9600@dmn{bps}.
10393
10394For example, to debug Emacs with the argument @samp{foo.txt}and
10395communicate with @value{GDBN} over serial port number 2 or board 1
10396using a 19200@dmn{bps} connection:
10397
10398@smallexample
10399load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10400@end smallexample
10401
10402@item On the @value{GDBN} host machine,
10403you need an unstripped copy of your program, since @value{GDBN} needs
10404symbols and debugging information. Start up @value{GDBN} as usual,
10405using the name of the local copy of your program as the first argument.
10406(You may also need the @w{@samp{--baud}} option if the serial line is
10407running at anything other than 9600@dmn{bps}. After that, use @code{target
10408remote} to establish communications with @code{gdbserve.nlm}. Its
10409argument is a device name (usually a serial device, like
10410@file{/dev/ttyb}). For example:
10411
10412@smallexample
10413(@value{GDBP}) target remote /dev/ttyb
10414@end smallexample
10415
10416@noindent
10417communications with the server via serial line @file{/dev/ttyb}.
10418@end table
10419
10420@node remote stub
10421@section Implementing a remote stub
7a292a7a 10422
8e04817f
AC
10423@cindex debugging stub, example
10424@cindex remote stub, example
10425@cindex stub example, remote debugging
10426The stub files provided with @value{GDBN} implement the target side of the
10427communication protocol, and the @value{GDBN} side is implemented in the
10428@value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10429these subroutines to communicate, and ignore the details. (If you're
10430implementing your own stub file, you can still ignore the details: start
10431with one of the existing stub files. @file{sparc-stub.c} is the best
10432organized, and therefore the easiest to read.)
10433
104c1213
JM
10434@cindex remote serial debugging, overview
10435To debug a program running on another machine (the debugging
10436@dfn{target} machine), you must first arrange for all the usual
10437prerequisites for the program to run by itself. For example, for a C
10438program, you need:
c906108c 10439
104c1213
JM
10440@enumerate
10441@item
10442A startup routine to set up the C runtime environment; these usually
10443have a name like @file{crt0}. The startup routine may be supplied by
10444your hardware supplier, or you may have to write your own.
96baa820 10445
5d161b24 10446@item
d4f3574e 10447A C subroutine library to support your program's
104c1213 10448subroutine calls, notably managing input and output.
96baa820 10449
104c1213
JM
10450@item
10451A way of getting your program to the other machine---for example, a
10452download program. These are often supplied by the hardware
10453manufacturer, but you may have to write your own from hardware
10454documentation.
10455@end enumerate
96baa820 10456
104c1213
JM
10457The next step is to arrange for your program to use a serial port to
10458communicate with the machine where @value{GDBN} is running (the @dfn{host}
10459machine). In general terms, the scheme looks like this:
96baa820 10460
104c1213
JM
10461@table @emph
10462@item On the host,
10463@value{GDBN} already understands how to use this protocol; when everything
10464else is set up, you can simply use the @samp{target remote} command
10465(@pxref{Targets,,Specifying a Debugging Target}).
10466
10467@item On the target,
10468you must link with your program a few special-purpose subroutines that
10469implement the @value{GDBN} remote serial protocol. The file containing these
10470subroutines is called a @dfn{debugging stub}.
10471
10472On certain remote targets, you can use an auxiliary program
10473@code{gdbserver} instead of linking a stub into your program.
10474@xref{Server,,Using the @code{gdbserver} program}, for details.
10475@end table
96baa820 10476
104c1213
JM
10477The debugging stub is specific to the architecture of the remote
10478machine; for example, use @file{sparc-stub.c} to debug programs on
10479@sc{sparc} boards.
96baa820 10480
104c1213
JM
10481@cindex remote serial stub list
10482These working remote stubs are distributed with @value{GDBN}:
96baa820 10483
104c1213
JM
10484@table @code
10485
10486@item i386-stub.c
41afff9a 10487@cindex @file{i386-stub.c}
104c1213
JM
10488@cindex Intel
10489@cindex i386
10490For Intel 386 and compatible architectures.
10491
10492@item m68k-stub.c
41afff9a 10493@cindex @file{m68k-stub.c}
104c1213
JM
10494@cindex Motorola 680x0
10495@cindex m680x0
10496For Motorola 680x0 architectures.
10497
10498@item sh-stub.c
41afff9a 10499@cindex @file{sh-stub.c}
104c1213
JM
10500@cindex Hitachi
10501@cindex SH
10502For Hitachi SH architectures.
10503
10504@item sparc-stub.c
41afff9a 10505@cindex @file{sparc-stub.c}
104c1213
JM
10506@cindex Sparc
10507For @sc{sparc} architectures.
10508
10509@item sparcl-stub.c
41afff9a 10510@cindex @file{sparcl-stub.c}
104c1213
JM
10511@cindex Fujitsu
10512@cindex SparcLite
10513For Fujitsu @sc{sparclite} architectures.
10514
10515@end table
10516
10517The @file{README} file in the @value{GDBN} distribution may list other
10518recently added stubs.
10519
10520@menu
10521* Stub Contents:: What the stub can do for you
10522* Bootstrapping:: What you must do for the stub
10523* Debug Session:: Putting it all together
104c1213
JM
10524@end menu
10525
6d2ebf8b 10526@node Stub Contents
6f05cf9f 10527@subsection What the stub can do for you
104c1213
JM
10528
10529@cindex remote serial stub
10530The debugging stub for your architecture supplies these three
10531subroutines:
10532
10533@table @code
10534@item set_debug_traps
10535@kindex set_debug_traps
10536@cindex remote serial stub, initialization
10537This routine arranges for @code{handle_exception} to run when your
10538program stops. You must call this subroutine explicitly near the
10539beginning of your program.
10540
10541@item handle_exception
10542@kindex handle_exception
10543@cindex remote serial stub, main routine
10544This is the central workhorse, but your program never calls it
10545explicitly---the setup code arranges for @code{handle_exception} to
10546run when a trap is triggered.
10547
10548@code{handle_exception} takes control when your program stops during
10549execution (for example, on a breakpoint), and mediates communications
10550with @value{GDBN} on the host machine. This is where the communications
10551protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
d4f3574e 10552representative on the target machine. It begins by sending summary
104c1213
JM
10553information on the state of your program, then continues to execute,
10554retrieving and transmitting any information @value{GDBN} needs, until you
10555execute a @value{GDBN} command that makes your program resume; at that point,
10556@code{handle_exception} returns control to your own code on the target
5d161b24 10557machine.
104c1213
JM
10558
10559@item breakpoint
10560@cindex @code{breakpoint} subroutine, remote
10561Use this auxiliary subroutine to make your program contain a
10562breakpoint. Depending on the particular situation, this may be the only
10563way for @value{GDBN} to get control. For instance, if your target
10564machine has some sort of interrupt button, you won't need to call this;
10565pressing the interrupt button transfers control to
10566@code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10567simply receiving characters on the serial port may also trigger a trap;
10568again, in that situation, you don't need to call @code{breakpoint} from
10569your own program---simply running @samp{target remote} from the host
5d161b24 10570@value{GDBN} session gets control.
104c1213
JM
10571
10572Call @code{breakpoint} if none of these is true, or if you simply want
10573to make certain your program stops at a predetermined point for the
10574start of your debugging session.
10575@end table
10576
6d2ebf8b 10577@node Bootstrapping
6f05cf9f 10578@subsection What you must do for the stub
104c1213
JM
10579
10580@cindex remote stub, support routines
10581The debugging stubs that come with @value{GDBN} are set up for a particular
10582chip architecture, but they have no information about the rest of your
10583debugging target machine.
10584
10585First of all you need to tell the stub how to communicate with the
10586serial port.
10587
10588@table @code
10589@item int getDebugChar()
10590@kindex getDebugChar
10591Write this subroutine to read a single character from the serial port.
10592It may be identical to @code{getchar} for your target system; a
10593different name is used to allow you to distinguish the two if you wish.
10594
10595@item void putDebugChar(int)
10596@kindex putDebugChar
10597Write this subroutine to write a single character to the serial port.
5d161b24 10598It may be identical to @code{putchar} for your target system; a
104c1213
JM
10599different name is used to allow you to distinguish the two if you wish.
10600@end table
10601
10602@cindex control C, and remote debugging
10603@cindex interrupting remote targets
10604If you want @value{GDBN} to be able to stop your program while it is
10605running, you need to use an interrupt-driven serial driver, and arrange
10606for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10607character). That is the character which @value{GDBN} uses to tell the
10608remote system to stop.
10609
10610Getting the debugging target to return the proper status to @value{GDBN}
10611probably requires changes to the standard stub; one quick and dirty way
10612is to just execute a breakpoint instruction (the ``dirty'' part is that
10613@value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10614
10615Other routines you need to supply are:
10616
10617@table @code
10618@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10619@kindex exceptionHandler
10620Write this function to install @var{exception_address} in the exception
10621handling tables. You need to do this because the stub does not have any
10622way of knowing what the exception handling tables on your target system
10623are like (for example, the processor's table might be in @sc{rom},
10624containing entries which point to a table in @sc{ram}).
10625@var{exception_number} is the exception number which should be changed;
10626its meaning is architecture-dependent (for example, different numbers
10627might represent divide by zero, misaligned access, etc). When this
10628exception occurs, control should be transferred directly to
10629@var{exception_address}, and the processor state (stack, registers,
10630and so on) should be just as it is when a processor exception occurs. So if
10631you want to use a jump instruction to reach @var{exception_address}, it
10632should be a simple jump, not a jump to subroutine.
10633
10634For the 386, @var{exception_address} should be installed as an interrupt
10635gate so that interrupts are masked while the handler runs. The gate
10636should be at privilege level 0 (the most privileged level). The
10637@sc{sparc} and 68k stubs are able to mask interrupts themselves without
10638help from @code{exceptionHandler}.
10639
10640@item void flush_i_cache()
10641@kindex flush_i_cache
d4f3574e 10642On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
104c1213
JM
10643instruction cache, if any, on your target machine. If there is no
10644instruction cache, this subroutine may be a no-op.
10645
10646On target machines that have instruction caches, @value{GDBN} requires this
10647function to make certain that the state of your program is stable.
10648@end table
10649
10650@noindent
10651You must also make sure this library routine is available:
10652
10653@table @code
10654@item void *memset(void *, int, int)
10655@kindex memset
10656This is the standard library function @code{memset} that sets an area of
10657memory to a known value. If you have one of the free versions of
10658@code{libc.a}, @code{memset} can be found there; otherwise, you must
10659either obtain it from your hardware manufacturer, or write your own.
10660@end table
10661
10662If you do not use the GNU C compiler, you may need other standard
10663library subroutines as well; this varies from one stub to another,
10664but in general the stubs are likely to use any of the common library
d4f3574e 10665subroutines which @code{@value{GCC}} generates as inline code.
104c1213
JM
10666
10667
6d2ebf8b 10668@node Debug Session
6f05cf9f 10669@subsection Putting it all together
104c1213
JM
10670
10671@cindex remote serial debugging summary
10672In summary, when your program is ready to debug, you must follow these
10673steps.
10674
10675@enumerate
10676@item
6d2ebf8b 10677Make sure you have defined the supporting low-level routines
104c1213
JM
10678(@pxref{Bootstrapping,,What you must do for the stub}):
10679@display
10680@code{getDebugChar}, @code{putDebugChar},
10681@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
10682@end display
10683
10684@item
10685Insert these lines near the top of your program:
10686
474c8240 10687@smallexample
104c1213
JM
10688set_debug_traps();
10689breakpoint();
474c8240 10690@end smallexample
104c1213
JM
10691
10692@item
10693For the 680x0 stub only, you need to provide a variable called
10694@code{exceptionHook}. Normally you just use:
10695
474c8240 10696@smallexample
104c1213 10697void (*exceptionHook)() = 0;
474c8240 10698@end smallexample
104c1213 10699
d4f3574e 10700@noindent
104c1213 10701but if before calling @code{set_debug_traps}, you set it to point to a
598ca718 10702function in your program, that function is called when
104c1213
JM
10703@code{@value{GDBN}} continues after stopping on a trap (for example, bus
10704error). The function indicated by @code{exceptionHook} is called with
10705one parameter: an @code{int} which is the exception number.
10706
10707@item
10708Compile and link together: your program, the @value{GDBN} debugging stub for
10709your target architecture, and the supporting subroutines.
10710
10711@item
10712Make sure you have a serial connection between your target machine and
10713the @value{GDBN} host, and identify the serial port on the host.
10714
10715@item
10716@c The "remote" target now provides a `load' command, so we should
10717@c document that. FIXME.
10718Download your program to your target machine (or get it there by
10719whatever means the manufacturer provides), and start it.
10720
10721@item
10722To start remote debugging, run @value{GDBN} on the host machine, and specify
10723as an executable file the program that is running in the remote machine.
10724This tells @value{GDBN} how to find your program's symbols and the contents
10725of its pure text.
10726
d4f3574e 10727@item
104c1213 10728@cindex serial line, @code{target remote}
d4f3574e 10729Establish communication using the @code{target remote} command.
104c1213
JM
10730Its argument specifies how to communicate with the target
10731machine---either via a devicename attached to a direct serial line, or a
9db8d71f 10732TCP or UDP port (usually to a terminal server which in turn has a serial line
104c1213
JM
10733to the target). For example, to use a serial line connected to the
10734device named @file{/dev/ttyb}:
10735
474c8240 10736@smallexample
104c1213 10737target remote /dev/ttyb
474c8240 10738@end smallexample
104c1213
JM
10739
10740@cindex TCP port, @code{target remote}
10741To use a TCP connection, use an argument of the form
9db8d71f
DJ
10742@code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10743For example, to connect to port 2828 on a
104c1213
JM
10744terminal server named @code{manyfarms}:
10745
474c8240 10746@smallexample
104c1213 10747target remote manyfarms:2828
474c8240 10748@end smallexample
a2bea4c3
CV
10749
10750If your remote target is actually running on the same machine as
10751your debugger session (e.g.@: a simulator of your target running on
10752the same host), you can omit the hostname. For example, to connect
10753to port 1234 on your local machine:
10754
474c8240 10755@smallexample
a2bea4c3 10756target remote :1234
474c8240 10757@end smallexample
a2bea4c3
CV
10758@noindent
10759
10760Note that the colon is still required here.
9db8d71f
DJ
10761
10762@cindex UDP port, @code{target remote}
10763To use a UDP connection, use an argument of the form
10764@code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10765on a terminal server named @code{manyfarms}:
10766
10767@smallexample
10768target remote udp:manyfarms:2828
10769@end smallexample
10770
10771When using a UDP connection for remote debugging, you should keep in mind
10772that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10773busy or unreliable networks, which will cause havoc with your debugging
10774session.
10775
104c1213
JM
10776@end enumerate
10777
10778Now you can use all the usual commands to examine and change data and to
10779step and continue the remote program.
10780
10781To resume the remote program and stop debugging it, use the @code{detach}
10782command.
10783
10784@cindex interrupting remote programs
10785@cindex remote programs, interrupting
10786Whenever @value{GDBN} is waiting for the remote program, if you type the
10787interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10788program. This may or may not succeed, depending in part on the hardware
10789and the serial drivers the remote system uses. If you type the
10790interrupt character once again, @value{GDBN} displays this prompt:
10791
474c8240 10792@smallexample
104c1213
JM
10793Interrupted while waiting for the program.
10794Give up (and stop debugging it)? (y or n)
474c8240 10795@end smallexample
104c1213
JM
10796
10797If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10798(If you decide you want to try again later, you can use @samp{target
10799remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10800goes back to waiting.
10801
104c1213 10802
8e04817f
AC
10803@node Configurations
10804@chapter Configuration-Specific Information
104c1213 10805
8e04817f
AC
10806While nearly all @value{GDBN} commands are available for all native and
10807cross versions of the debugger, there are some exceptions. This chapter
10808describes things that are only available in certain configurations.
104c1213 10809
8e04817f
AC
10810There are three major categories of configurations: native
10811configurations, where the host and target are the same, embedded
10812operating system configurations, which are usually the same for several
10813different processor architectures, and bare embedded processors, which
10814are quite different from each other.
104c1213 10815
8e04817f
AC
10816@menu
10817* Native::
10818* Embedded OS::
10819* Embedded Processors::
10820* Architectures::
10821@end menu
104c1213 10822
8e04817f
AC
10823@node Native
10824@section Native
104c1213 10825
8e04817f
AC
10826This section describes details specific to particular native
10827configurations.
6cf7e474 10828
8e04817f
AC
10829@menu
10830* HP-UX:: HP-UX
10831* SVR4 Process Information:: SVR4 process information
10832* DJGPP Native:: Features specific to the DJGPP port
78c47bea 10833* Cygwin Native:: Features specific to the Cygwin port
8e04817f 10834@end menu
6cf7e474 10835
8e04817f
AC
10836@node HP-UX
10837@subsection HP-UX
104c1213 10838
8e04817f
AC
10839On HP-UX systems, if you refer to a function or variable name that
10840begins with a dollar sign, @value{GDBN} searches for a user or system
10841name first, before it searches for a convenience variable.
104c1213 10842
8e04817f
AC
10843@node SVR4 Process Information
10844@subsection SVR4 process information
104c1213 10845
8e04817f
AC
10846@kindex /proc
10847@cindex process image
104c1213 10848
8e04817f
AC
10849Many versions of SVR4 provide a facility called @samp{/proc} that can be
10850used to examine the image of a running process using file-system
10851subroutines. If @value{GDBN} is configured for an operating system with
10852this facility, the command @code{info proc} is available to report on
10853several kinds of information about the process running your program.
10854@code{info proc} works only on SVR4 systems that include the
10855@code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
10856and Unixware, but not HP-UX or Linux, for example.
104c1213 10857
8e04817f
AC
10858@table @code
10859@kindex info proc
10860@item info proc
10861Summarize available information about the process.
6cf7e474 10862
8e04817f
AC
10863@kindex info proc mappings
10864@item info proc mappings
10865Report on the address ranges accessible in the program, with information
10866on whether your program may read, write, or execute each range.
10867@ignore
10868@comment These sub-options of 'info proc' were not included when
10869@comment procfs.c was re-written. Keep their descriptions around
10870@comment against the day when someone finds the time to put them back in.
10871@kindex info proc times
10872@item info proc times
10873Starting time, user CPU time, and system CPU time for your program and
10874its children.
6cf7e474 10875
8e04817f
AC
10876@kindex info proc id
10877@item info proc id
10878Report on the process IDs related to your program: its own process ID,
10879the ID of its parent, the process group ID, and the session ID.
104c1213 10880
8e04817f
AC
10881@kindex info proc status
10882@item info proc status
10883General information on the state of the process. If the process is
10884stopped, this report includes the reason for stopping, and any signal
10885received.
d4f3574e 10886
8e04817f
AC
10887@item info proc all
10888Show all the above information about the process.
10889@end ignore
10890@end table
104c1213 10891
8e04817f
AC
10892@node DJGPP Native
10893@subsection Features for Debugging @sc{djgpp} Programs
10894@cindex @sc{djgpp} debugging
10895@cindex native @sc{djgpp} debugging
10896@cindex MS-DOS-specific commands
104c1213 10897
8e04817f
AC
10898@sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
10899MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
10900that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
10901top of real-mode DOS systems and their emulations.
104c1213 10902
8e04817f
AC
10903@value{GDBN} supports native debugging of @sc{djgpp} programs, and
10904defines a few commands specific to the @sc{djgpp} port. This
10905subsection describes those commands.
104c1213 10906
8e04817f
AC
10907@table @code
10908@kindex info dos
10909@item info dos
10910This is a prefix of @sc{djgpp}-specific commands which print
10911information about the target system and important OS structures.
f1251bdd 10912
8e04817f
AC
10913@kindex sysinfo
10914@cindex MS-DOS system info
10915@cindex free memory information (MS-DOS)
10916@item info dos sysinfo
10917This command displays assorted information about the underlying
10918platform: the CPU type and features, the OS version and flavor, the
10919DPMI version, and the available conventional and DPMI memory.
104c1213 10920
8e04817f
AC
10921@cindex GDT
10922@cindex LDT
10923@cindex IDT
10924@cindex segment descriptor tables
10925@cindex descriptor tables display
10926@item info dos gdt
10927@itemx info dos ldt
10928@itemx info dos idt
10929These 3 commands display entries from, respectively, Global, Local,
10930and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
10931tables are data structures which store a descriptor for each segment
10932that is currently in use. The segment's selector is an index into a
10933descriptor table; the table entry for that index holds the
10934descriptor's base address and limit, and its attributes and access
10935rights.
104c1213 10936
8e04817f
AC
10937A typical @sc{djgpp} program uses 3 segments: a code segment, a data
10938segment (used for both data and the stack), and a DOS segment (which
10939allows access to DOS/BIOS data structures and absolute addresses in
10940conventional memory). However, the DPMI host will usually define
10941additional segments in order to support the DPMI environment.
d4f3574e 10942
8e04817f
AC
10943@cindex garbled pointers
10944These commands allow to display entries from the descriptor tables.
10945Without an argument, all entries from the specified table are
10946displayed. An argument, which should be an integer expression, means
10947display a single entry whose index is given by the argument. For
10948example, here's a convenient way to display information about the
10949debugged program's data segment:
104c1213 10950
8e04817f
AC
10951@smallexample
10952@exdent @code{(@value{GDBP}) info dos ldt $ds}
10953@exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
10954@end smallexample
104c1213 10955
8e04817f
AC
10956@noindent
10957This comes in handy when you want to see whether a pointer is outside
10958the data segment's limit (i.e.@: @dfn{garbled}).
104c1213 10959
8e04817f
AC
10960@cindex page tables display (MS-DOS)
10961@item info dos pde
10962@itemx info dos pte
10963These two commands display entries from, respectively, the Page
10964Directory and the Page Tables. Page Directories and Page Tables are
10965data structures which control how virtual memory addresses are mapped
10966into physical addresses. A Page Table includes an entry for every
10967page of memory that is mapped into the program's address space; there
10968may be several Page Tables, each one holding up to 4096 entries. A
10969Page Directory has up to 4096 entries, one each for every Page Table
10970that is currently in use.
104c1213 10971
8e04817f
AC
10972Without an argument, @kbd{info dos pde} displays the entire Page
10973Directory, and @kbd{info dos pte} displays all the entries in all of
10974the Page Tables. An argument, an integer expression, given to the
10975@kbd{info dos pde} command means display only that entry from the Page
10976Directory table. An argument given to the @kbd{info dos pte} command
10977means display entries from a single Page Table, the one pointed to by
10978the specified entry in the Page Directory.
104c1213 10979
8e04817f
AC
10980@cindex direct memory access (DMA) on MS-DOS
10981These commands are useful when your program uses @dfn{DMA} (Direct
10982Memory Access), which needs physical addresses to program the DMA
10983controller.
104c1213 10984
8e04817f 10985These commands are supported only with some DPMI servers.
104c1213 10986
8e04817f
AC
10987@cindex physical address from linear address
10988@item info dos address-pte @var{addr}
10989This command displays the Page Table entry for a specified linear
10990address. The argument linear address @var{addr} should already have the
10991appropriate segment's base address added to it, because this command
10992accepts addresses which may belong to @emph{any} segment. For
10993example, here's how to display the Page Table entry for the page where
10994the variable @code{i} is stored:
104c1213 10995
8e04817f
AC
10996@smallexample
10997@exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
10998@exdent @code{Page Table entry for address 0x11a00d30:}
10999@exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11000@end smallexample
104c1213 11001
8e04817f
AC
11002@noindent
11003This says that @code{i} is stored at offset @code{0xd30} from the page
11004whose physical base address is @code{0x02698000}, and prints all the
11005attributes of that page.
104c1213 11006
8e04817f
AC
11007Note that you must cast the addresses of variables to a @code{char *},
11008since otherwise the value of @code{__djgpp_base_address}, the base
11009address of all variables and functions in a @sc{djgpp} program, will
11010be added using the rules of C pointer arithmetics: if @code{i} is
11011declared an @code{int}, @value{GDBN} will add 4 times the value of
11012@code{__djgpp_base_address} to the address of @code{i}.
104c1213 11013
8e04817f
AC
11014Here's another example, it displays the Page Table entry for the
11015transfer buffer:
104c1213 11016
8e04817f
AC
11017@smallexample
11018@exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11019@exdent @code{Page Table entry for address 0x29110:}
11020@exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11021@end smallexample
104c1213 11022
8e04817f
AC
11023@noindent
11024(The @code{+ 3} offset is because the transfer buffer's address is the
110253rd member of the @code{_go32_info_block} structure.) The output of
11026this command clearly shows that addresses in conventional memory are
11027mapped 1:1, i.e.@: the physical and linear addresses are identical.
104c1213 11028
8e04817f
AC
11029This command is supported only with some DPMI servers.
11030@end table
104c1213 11031
78c47bea
PM
11032@node Cygwin Native
11033@subsection Features for Debugging MS Windows PE executables
11034@cindex MS Windows debugging
11035@cindex native Cygwin debugging
11036@cindex Cygwin-specific commands
11037
11038@value{GDBN} supports native debugging of MS Windows programs, and
11039defines a few commands specific to the Cygwin port. This
11040subsection describes those commands.
11041
11042@table @code
11043@kindex info w32
11044@item info w32
11045This is a prefix of MS Windows specific commands which print
11046information about the target system and important OS structures.
11047
11048@item info w32 selector
11049This command displays information returned by
11050the Win32 API @code{GetThreadSelectorEntry} function.
11051It takes an optional argument that is evaluated to
11052a long value to give the information about this given selector.
11053Without argument, this command displays information
11054about the the six segment registers.
11055
11056@kindex info dll
11057@item info dll
11058This is a Cygwin specific alias of info shared.
11059
11060@kindex dll-symbols
11061@item dll-symbols
11062This command loads symbols from a dll similarly to
11063add-sym command but without the need to specify a base address.
11064
11065@kindex set new-console
11066@item set new-console @var{mode}
11067If @var{mode} is @code{on} the debuggee will
11068be started in a new console on next start.
11069If @var{mode} is @code{off}i, the debuggee will
11070be started in the same console as the debugger.
11071
11072@kindex show new-console
11073@item show new-console
11074Displays whether a new console is used
11075when the debuggee is started.
11076
11077@kindex set new-group
11078@item set new-group @var{mode}
11079This boolean value controls whether the debuggee should
11080start a new group or stay in the same group as the debugger.
11081This affects the way the Windows OS handles
11082Ctrl-C.
11083
11084@kindex show new-group
11085@item show new-group
11086Displays current value of new-group boolean.
11087
11088@kindex set debugevents
11089@item set debugevents
11090This boolean value adds debug output concerning events seen by the debugger.
11091
11092@kindex set debugexec
11093@item set debugexec
11094This boolean value adds debug output concerning execute events
11095seen by the debugger.
11096
11097@kindex set debugexceptions
11098@item set debugexceptions
11099This boolean value adds debug ouptut concerning exception events
11100seen by the debugger.
11101
11102@kindex set debugmemory
11103@item set debugmemory
11104This boolean value adds debug ouptut concerning memory events
11105seen by the debugger.
11106
11107@kindex set shell
11108@item set shell
11109This boolean values specifies whether the debuggee is called
11110via a shell or directly (default value is on).
11111
11112@kindex show shell
11113@item show shell
11114Displays if the debuggee will be started with a shell.
11115
11116@end table
11117
8e04817f
AC
11118@node Embedded OS
11119@section Embedded Operating Systems
104c1213 11120
8e04817f
AC
11121This section describes configurations involving the debugging of
11122embedded operating systems that are available for several different
11123architectures.
d4f3574e 11124
8e04817f
AC
11125@menu
11126* VxWorks:: Using @value{GDBN} with VxWorks
11127@end menu
104c1213 11128
8e04817f
AC
11129@value{GDBN} includes the ability to debug programs running on
11130various real-time operating systems.
104c1213 11131
8e04817f
AC
11132@node VxWorks
11133@subsection Using @value{GDBN} with VxWorks
104c1213 11134
8e04817f 11135@cindex VxWorks
104c1213 11136
8e04817f 11137@table @code
104c1213 11138
8e04817f
AC
11139@kindex target vxworks
11140@item target vxworks @var{machinename}
11141A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11142is the target system's machine name or IP address.
104c1213 11143
8e04817f 11144@end table
104c1213 11145
8e04817f
AC
11146On VxWorks, @code{load} links @var{filename} dynamically on the
11147current target system as well as adding its symbols in @value{GDBN}.
104c1213 11148
8e04817f
AC
11149@value{GDBN} enables developers to spawn and debug tasks running on networked
11150VxWorks targets from a Unix host. Already-running tasks spawned from
11151the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11152both the Unix host and on the VxWorks target. The program
11153@code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11154installed with the name @code{vxgdb}, to distinguish it from a
11155@value{GDBN} for debugging programs on the host itself.)
104c1213 11156
8e04817f
AC
11157@table @code
11158@item VxWorks-timeout @var{args}
11159@kindex vxworks-timeout
11160All VxWorks-based targets now support the option @code{vxworks-timeout}.
11161This option is set by the user, and @var{args} represents the number of
11162seconds @value{GDBN} waits for responses to rpc's. You might use this if
11163your VxWorks target is a slow software simulator or is on the far side
11164of a thin network line.
11165@end table
104c1213 11166
8e04817f
AC
11167The following information on connecting to VxWorks was current when
11168this manual was produced; newer releases of VxWorks may use revised
11169procedures.
104c1213 11170
8e04817f
AC
11171@kindex INCLUDE_RDB
11172To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11173to include the remote debugging interface routines in the VxWorks
11174library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11175VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11176kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11177source debugging task @code{tRdbTask} when VxWorks is booted. For more
11178information on configuring and remaking VxWorks, see the manufacturer's
11179manual.
11180@c VxWorks, see the @cite{VxWorks Programmer's Guide}.
104c1213 11181
8e04817f
AC
11182Once you have included @file{rdb.a} in your VxWorks system image and set
11183your Unix execution search path to find @value{GDBN}, you are ready to
11184run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11185@code{vxgdb}, depending on your installation).
104c1213 11186
8e04817f 11187@value{GDBN} comes up showing the prompt:
104c1213 11188
474c8240 11189@smallexample
8e04817f 11190(vxgdb)
474c8240 11191@end smallexample
104c1213 11192
8e04817f
AC
11193@menu
11194* VxWorks Connection:: Connecting to VxWorks
11195* VxWorks Download:: VxWorks download
11196* VxWorks Attach:: Running tasks
11197@end menu
104c1213 11198
8e04817f
AC
11199@node VxWorks Connection
11200@subsubsection Connecting to VxWorks
104c1213 11201
8e04817f
AC
11202The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11203network. To connect to a target whose host name is ``@code{tt}'', type:
104c1213 11204
474c8240 11205@smallexample
8e04817f 11206(vxgdb) target vxworks tt
474c8240 11207@end smallexample
104c1213 11208
8e04817f
AC
11209@need 750
11210@value{GDBN} displays messages like these:
104c1213 11211
8e04817f
AC
11212@smallexample
11213Attaching remote machine across net...
11214Connected to tt.
11215@end smallexample
104c1213 11216
8e04817f
AC
11217@need 1000
11218@value{GDBN} then attempts to read the symbol tables of any object modules
11219loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11220these files by searching the directories listed in the command search
11221path (@pxref{Environment, ,Your program's environment}); if it fails
11222to find an object file, it displays a message such as:
5d161b24 11223
474c8240 11224@smallexample
8e04817f 11225prog.o: No such file or directory.
474c8240 11226@end smallexample
104c1213 11227
8e04817f
AC
11228When this happens, add the appropriate directory to the search path with
11229the @value{GDBN} command @code{path}, and execute the @code{target}
11230command again.
104c1213 11231
8e04817f
AC
11232@node VxWorks Download
11233@subsubsection VxWorks download
104c1213 11234
8e04817f
AC
11235@cindex download to VxWorks
11236If you have connected to the VxWorks target and you want to debug an
11237object that has not yet been loaded, you can use the @value{GDBN}
11238@code{load} command to download a file from Unix to VxWorks
11239incrementally. The object file given as an argument to the @code{load}
11240command is actually opened twice: first by the VxWorks target in order
11241to download the code, then by @value{GDBN} in order to read the symbol
11242table. This can lead to problems if the current working directories on
11243the two systems differ. If both systems have NFS mounted the same
11244filesystems, you can avoid these problems by using absolute paths.
11245Otherwise, it is simplest to set the working directory on both systems
11246to the directory in which the object file resides, and then to reference
11247the file by its name, without any path. For instance, a program
11248@file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11249and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11250program, type this on VxWorks:
104c1213 11251
474c8240 11252@smallexample
8e04817f 11253-> cd "@var{vxpath}/vw/demo/rdb"
474c8240 11254@end smallexample
104c1213 11255
8e04817f
AC
11256@noindent
11257Then, in @value{GDBN}, type:
104c1213 11258
474c8240 11259@smallexample
8e04817f
AC
11260(vxgdb) cd @var{hostpath}/vw/demo/rdb
11261(vxgdb) load prog.o
474c8240 11262@end smallexample
104c1213 11263
8e04817f 11264@value{GDBN} displays a response similar to this:
104c1213 11265
8e04817f
AC
11266@smallexample
11267Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11268@end smallexample
104c1213 11269
8e04817f
AC
11270You can also use the @code{load} command to reload an object module
11271after editing and recompiling the corresponding source file. Note that
11272this makes @value{GDBN} delete all currently-defined breakpoints,
11273auto-displays, and convenience variables, and to clear the value
11274history. (This is necessary in order to preserve the integrity of
11275debugger's data structures that reference the target system's symbol
11276table.)
104c1213 11277
8e04817f
AC
11278@node VxWorks Attach
11279@subsubsection Running tasks
104c1213
JM
11280
11281@cindex running VxWorks tasks
11282You can also attach to an existing task using the @code{attach} command as
11283follows:
11284
474c8240 11285@smallexample
104c1213 11286(vxgdb) attach @var{task}
474c8240 11287@end smallexample
104c1213
JM
11288
11289@noindent
11290where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11291or suspended when you attach to it. Running tasks are suspended at
11292the time of attachment.
11293
6d2ebf8b 11294@node Embedded Processors
104c1213
JM
11295@section Embedded Processors
11296
11297This section goes into details specific to particular embedded
11298configurations.
11299
7d86b5d5 11300
104c1213 11301@menu
104c1213
JM
11302* ARM:: ARM
11303* H8/300:: Hitachi H8/300
11304* H8/500:: Hitachi H8/500
11305* i960:: Intel i960
11306* M32R/D:: Mitsubishi M32R/D
11307* M68K:: Motorola M68K
11308* M88K:: Motorola M88K
11309* MIPS Embedded:: MIPS Embedded
11310* PA:: HP PA Embedded
11311* PowerPC: PowerPC
11312* SH:: Hitachi SH
11313* Sparclet:: Tsqware Sparclet
11314* Sparclite:: Fujitsu Sparclite
11315* ST2000:: Tandem ST2000
11316* Z8000:: Zilog Z8000
11317@end menu
11318
6d2ebf8b 11319@node ARM
104c1213
JM
11320@subsection ARM
11321
11322@table @code
11323
8e04817f
AC
11324@kindex target rdi
11325@item target rdi @var{dev}
11326ARM Angel monitor, via RDI library interface to ADP protocol. You may
11327use this target to communicate with both boards running the Angel
11328monitor, or with the EmbeddedICE JTAG debug device.
11329
11330@kindex target rdp
11331@item target rdp @var{dev}
11332ARM Demon monitor.
11333
11334@end table
11335
11336@node H8/300
11337@subsection Hitachi H8/300
11338
11339@table @code
11340
11341@kindex target hms@r{, with H8/300}
11342@item target hms @var{dev}
11343A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11344Use special commands @code{device} and @code{speed} to control the serial
11345line and the communications speed used.
11346
11347@kindex target e7000@r{, with H8/300}
11348@item target e7000 @var{dev}
11349E7000 emulator for Hitachi H8 and SH.
11350
11351@kindex target sh3@r{, with H8/300}
11352@kindex target sh3e@r{, with H8/300}
11353@item target sh3 @var{dev}
11354@itemx target sh3e @var{dev}
11355Hitachi SH-3 and SH-3E target systems.
11356
11357@end table
11358
11359@cindex download to H8/300 or H8/500
11360@cindex H8/300 or H8/500 download
11361@cindex download to Hitachi SH
11362@cindex Hitachi SH download
11363When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11364board, the @code{load} command downloads your program to the Hitachi
11365board and also opens it as the current executable target for
11366@value{GDBN} on your host (like the @code{file} command).
11367
11368@value{GDBN} needs to know these things to talk to your
11369Hitachi SH, H8/300, or H8/500:
11370
11371@enumerate
11372@item
11373that you want to use @samp{target hms}, the remote debugging interface
11374for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11375emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11376the default when @value{GDBN} is configured specifically for the Hitachi SH,
11377H8/300, or H8/500.)
11378
11379@item
11380what serial device connects your host to your Hitachi board (the first
11381serial device available on your host is the default).
11382
11383@item
11384what speed to use over the serial device.
11385@end enumerate
11386
11387@menu
11388* Hitachi Boards:: Connecting to Hitachi boards.
11389* Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11390* Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11391@end menu
11392
11393@node Hitachi Boards
11394@subsubsection Connecting to Hitachi boards
11395
11396@c only for Unix hosts
11397@kindex device
11398@cindex serial device, Hitachi micros
11399Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11400need to explicitly set the serial device. The default @var{port} is the
11401first available port on your host. This is only necessary on Unix
11402hosts, where it is typically something like @file{/dev/ttya}.
11403
11404@kindex speed
11405@cindex serial line speed, Hitachi micros
11406@code{@value{GDBN}} has another special command to set the communications
11407speed: @samp{speed @var{bps}}. This command also is only used from Unix
11408hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11409the DOS @code{mode} command (for instance,
11410@w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11411
11412The @samp{device} and @samp{speed} commands are available only when you
11413use a Unix host to debug your Hitachi microprocessor programs. If you
11414use a DOS host,
11415@value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11416called @code{asynctsr} to communicate with the development board
11417through a PC serial port. You must also use the DOS @code{mode} command
11418to set up the serial port on the DOS side.
11419
11420The following sample session illustrates the steps needed to start a
11421program under @value{GDBN} control on an H8/300. The example uses a
11422sample H8/300 program called @file{t.x}. The procedure is the same for
11423the Hitachi SH and the H8/500.
11424
11425First hook up your development board. In this example, we use a
11426board attached to serial port @code{COM2}; if you use a different serial
11427port, substitute its name in the argument of the @code{mode} command.
11428When you call @code{asynctsr}, the auxiliary comms program used by the
11429debugger, you give it just the numeric part of the serial port's name;
11430for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11431@code{COM2}.
11432
474c8240 11433@smallexample
8e04817f
AC
11434C:\H8300\TEST> asynctsr 2
11435C:\H8300\TEST> mode com2:9600,n,8,1,p
11436
11437Resident portion of MODE loaded
11438
11439COM2: 9600, n, 8, 1, p
11440
474c8240 11441@end smallexample
8e04817f
AC
11442
11443@quotation
11444@emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11445@code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11446disable it, or even boot without it, to use @code{asynctsr} to control
11447your development board.
11448@end quotation
11449
11450@kindex target hms@r{, and serial protocol}
11451Now that serial communications are set up, and the development board is
11452connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11453the name of your program as the argument. @code{@value{GDBN}} prompts
11454you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11455commands to begin your debugging session: @samp{target hms} to specify
11456cross-debugging to the Hitachi board, and the @code{load} command to
11457download your program to the board. @code{load} displays the names of
11458the program's sections, and a @samp{*} for each 2K of data downloaded.
11459(If you want to refresh @value{GDBN} data on symbols or on the
11460executable file without downloading, use the @value{GDBN} commands
11461@code{file} or @code{symbol-file}. These commands, and @code{load}
11462itself, are described in @ref{Files,,Commands to specify files}.)
11463
11464@smallexample
11465(eg-C:\H8300\TEST) @value{GDBP} t.x
11466@value{GDBN} is free software and you are welcome to distribute copies
11467 of it under certain conditions; type "show copying" to see
11468 the conditions.
11469There is absolutely no warranty for @value{GDBN}; type "show warranty"
11470for details.
11471@value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11472(@value{GDBP}) target hms
11473Connected to remote H8/300 HMS system.
11474(@value{GDBP}) load t.x
11475.text : 0x8000 .. 0xabde ***********
11476.data : 0xabde .. 0xad30 *
11477.stack : 0xf000 .. 0xf014 *
11478@end smallexample
11479
11480At this point, you're ready to run or debug your program. From here on,
11481you can use all the usual @value{GDBN} commands. The @code{break} command
11482sets breakpoints; the @code{run} command starts your program;
11483@code{print} or @code{x} display data; the @code{continue} command
11484resumes execution after stopping at a breakpoint. You can use the
11485@code{help} command at any time to find out more about @value{GDBN} commands.
11486
11487Remember, however, that @emph{operating system} facilities aren't
11488available on your development board; for example, if your program hangs,
11489you can't send an interrupt---but you can press the @sc{reset} switch!
11490
11491Use the @sc{reset} button on the development board
11492@itemize @bullet
11493@item
11494to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11495no way to pass an interrupt signal to the development board); and
11496
11497@item
11498to return to the @value{GDBN} command prompt after your program finishes
11499normally. The communications protocol provides no other way for @value{GDBN}
11500to detect program completion.
11501@end itemize
11502
11503In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11504development board as a ``normal exit'' of your program.
11505
11506@node Hitachi ICE
11507@subsubsection Using the E7000 in-circuit emulator
11508
11509@kindex target e7000@r{, with Hitachi ICE}
11510You can use the E7000 in-circuit emulator to develop code for either the
11511Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11512e7000} command to connect @value{GDBN} to your E7000:
11513
11514@table @code
11515@item target e7000 @var{port} @var{speed}
11516Use this form if your E7000 is connected to a serial port. The
11517@var{port} argument identifies what serial port to use (for example,
11518@samp{com2}). The third argument is the line speed in bits per second
11519(for example, @samp{9600}).
11520
11521@item target e7000 @var{hostname}
11522If your E7000 is installed as a host on a TCP/IP network, you can just
11523specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11524@end table
11525
11526@node Hitachi Special
11527@subsubsection Special @value{GDBN} commands for Hitachi micros
11528
11529Some @value{GDBN} commands are available only for the H8/300:
11530
11531@table @code
11532
11533@kindex set machine
11534@kindex show machine
11535@item set machine h8300
11536@itemx set machine h8300h
11537Condition @value{GDBN} for one of the two variants of the H8/300
11538architecture with @samp{set machine}. You can use @samp{show machine}
11539to check which variant is currently in effect.
104c1213
JM
11540
11541@end table
11542
8e04817f
AC
11543@node H8/500
11544@subsection H8/500
104c1213
JM
11545
11546@table @code
11547
8e04817f
AC
11548@kindex set memory @var{mod}
11549@cindex memory models, H8/500
11550@item set memory @var{mod}
11551@itemx show memory
11552Specify which H8/500 memory model (@var{mod}) you are using with
11553@samp{set memory}; check which memory model is in effect with @samp{show
11554memory}. The accepted values for @var{mod} are @code{small},
11555@code{big}, @code{medium}, and @code{compact}.
104c1213 11556
8e04817f 11557@end table
104c1213 11558
8e04817f
AC
11559@node i960
11560@subsection Intel i960
104c1213 11561
8e04817f 11562@table @code
104c1213 11563
8e04817f
AC
11564@kindex target mon960
11565@item target mon960 @var{dev}
11566MON960 monitor for Intel i960.
104c1213 11567
8e04817f
AC
11568@kindex target nindy
11569@item target nindy @var{devicename}
11570An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
11571the name of the serial device to use for the connection, e.g.
11572@file{/dev/ttya}.
104c1213 11573
8e04817f
AC
11574@end table
11575
11576@cindex Nindy
11577@cindex i960
11578@dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
11579@value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
11580tell @value{GDBN} how to connect to the 960 in several ways:
11581
11582@itemize @bullet
104c1213 11583@item
8e04817f
AC
11584Through command line options specifying serial port, version of the
11585Nindy protocol, and communications speed;
104c1213
JM
11586
11587@item
8e04817f 11588By responding to a prompt on startup;
104c1213
JM
11589
11590@item
8e04817f
AC
11591By using the @code{target} command at any point during your @value{GDBN}
11592session. @xref{Target Commands, ,Commands for managing targets}.
11593
11594@end itemize
11595
11596@cindex download to Nindy-960
11597With the Nindy interface to an Intel 960 board, @code{load}
11598downloads @var{filename} to the 960 as well as adding its symbols in
11599@value{GDBN}.
11600
11601@menu
11602* Nindy Startup:: Startup with Nindy
11603* Nindy Options:: Options for Nindy
11604* Nindy Reset:: Nindy reset command
11605@end menu
11606
11607@node Nindy Startup
11608@subsubsection Startup with Nindy
11609
11610If you simply start @code{@value{GDBP}} without using any command-line
11611options, you are prompted for what serial port to use, @emph{before} you
11612reach the ordinary @value{GDBN} prompt:
11613
474c8240 11614@smallexample
8e04817f 11615Attach /dev/ttyNN -- specify NN, or "quit" to quit:
474c8240 11616@end smallexample
8e04817f
AC
11617
11618@noindent
11619Respond to the prompt with whatever suffix (after @samp{/dev/tty})
11620identifies the serial port you want to use. You can, if you choose,
11621simply start up with no Nindy connection by responding to the prompt
11622with an empty line. If you do this and later wish to attach to Nindy,
11623use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
11624
11625@node Nindy Options
11626@subsubsection Options for Nindy
11627
11628These are the startup options for beginning your @value{GDBN} session with a
11629Nindy-960 board attached:
11630
11631@table @code
11632@item -r @var{port}
11633Specify the serial port name of a serial interface to be used to connect
11634to the target system. This option is only available when @value{GDBN} is
11635configured for the Intel 960 target architecture. You may specify
11636@var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
11637device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
11638suffix for a specific @code{tty} (e.g. @samp{-r a}).
11639
11640@item -O
11641(An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
11642the ``old'' Nindy monitor protocol to connect to the target system.
11643This option is only available when @value{GDBN} is configured for the Intel 960
11644target architecture.
11645
11646@quotation
11647@emph{Warning:} if you specify @samp{-O}, but are actually trying to
11648connect to a target system that expects the newer protocol, the connection
11649fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
11650attempts to reconnect at several different line speeds. You can abort
11651this process with an interrupt.
11652@end quotation
11653
11654@item -brk
11655Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
11656system, in an attempt to reset it, before connecting to a Nindy target.
11657
11658@quotation
11659@emph{Warning:} Many target systems do not have the hardware that this
11660requires; it only works with a few boards.
11661@end quotation
11662@end table
11663
11664The standard @samp{-b} option controls the line speed used on the serial
11665port.
11666
11667@c @group
11668@node Nindy Reset
11669@subsubsection Nindy reset command
11670
11671@table @code
11672@item reset
11673@kindex reset
11674For a Nindy target, this command sends a ``break'' to the remote target
11675system; this is only useful if the target has been equipped with a
11676circuit to perform a hard reset (or some other interesting action) when
11677a break is detected.
11678@end table
11679@c @end group
11680
11681@node M32R/D
11682@subsection Mitsubishi M32R/D
11683
11684@table @code
11685
11686@kindex target m32r
11687@item target m32r @var{dev}
11688Mitsubishi M32R/D ROM monitor.
11689
11690@end table
11691
11692@node M68K
11693@subsection M68k
11694
11695The Motorola m68k configuration includes ColdFire support, and
11696target command for the following ROM monitors.
11697
11698@table @code
11699
11700@kindex target abug
11701@item target abug @var{dev}
11702ABug ROM monitor for M68K.
11703
11704@kindex target cpu32bug
11705@item target cpu32bug @var{dev}
11706CPU32BUG monitor, running on a CPU32 (M68K) board.
11707
11708@kindex target dbug
11709@item target dbug @var{dev}
11710dBUG ROM monitor for Motorola ColdFire.
11711
11712@kindex target est
11713@item target est @var{dev}
11714EST-300 ICE monitor, running on a CPU32 (M68K) board.
11715
11716@kindex target rom68k
11717@item target rom68k @var{dev}
11718ROM 68K monitor, running on an M68K IDP board.
11719
11720@end table
11721
11722If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will
11723instead have only a single special target command:
11724
11725@table @code
11726
11727@kindex target es1800
11728@item target es1800 @var{dev}
11729ES-1800 emulator for M68K.
11730
11731@end table
11732
11733[context?]
11734
11735@table @code
11736
11737@kindex target rombug
11738@item target rombug @var{dev}
11739ROMBUG ROM monitor for OS/9000.
11740
11741@end table
11742
11743@node M88K
11744@subsection M88K
11745
11746@table @code
11747
11748@kindex target bug
11749@item target bug @var{dev}
11750BUG monitor, running on a MVME187 (m88k) board.
11751
11752@end table
11753
11754@node MIPS Embedded
11755@subsection MIPS Embedded
11756
11757@cindex MIPS boards
11758@value{GDBN} can use the MIPS remote debugging protocol to talk to a
11759MIPS board attached to a serial line. This is available when
11760you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
104c1213 11761
8e04817f
AC
11762@need 1000
11763Use these @value{GDBN} commands to specify the connection to your target board:
104c1213 11764
8e04817f
AC
11765@table @code
11766@item target mips @var{port}
11767@kindex target mips @var{port}
11768To run a program on the board, start up @code{@value{GDBP}} with the
11769name of your program as the argument. To connect to the board, use the
11770command @samp{target mips @var{port}}, where @var{port} is the name of
11771the serial port connected to the board. If the program has not already
11772been downloaded to the board, you may use the @code{load} command to
11773download it. You can then use all the usual @value{GDBN} commands.
104c1213 11774
8e04817f
AC
11775For example, this sequence connects to the target board through a serial
11776port, and loads and runs a program called @var{prog} through the
11777debugger:
104c1213 11778
474c8240 11779@smallexample
8e04817f
AC
11780host$ @value{GDBP} @var{prog}
11781@value{GDBN} is free software and @dots{}
11782(@value{GDBP}) target mips /dev/ttyb
11783(@value{GDBP}) load @var{prog}
11784(@value{GDBP}) run
474c8240 11785@end smallexample
104c1213 11786
8e04817f
AC
11787@item target mips @var{hostname}:@var{portnumber}
11788On some @value{GDBN} host configurations, you can specify a TCP
11789connection (for instance, to a serial line managed by a terminal
11790concentrator) instead of a serial port, using the syntax
11791@samp{@var{hostname}:@var{portnumber}}.
104c1213 11792
8e04817f
AC
11793@item target pmon @var{port}
11794@kindex target pmon @var{port}
11795PMON ROM monitor.
104c1213 11796
8e04817f
AC
11797@item target ddb @var{port}
11798@kindex target ddb @var{port}
11799NEC's DDB variant of PMON for Vr4300.
104c1213 11800
8e04817f
AC
11801@item target lsi @var{port}
11802@kindex target lsi @var{port}
11803LSI variant of PMON.
104c1213 11804
8e04817f
AC
11805@kindex target r3900
11806@item target r3900 @var{dev}
11807Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
104c1213 11808
8e04817f
AC
11809@kindex target array
11810@item target array @var{dev}
11811Array Tech LSI33K RAID controller board.
104c1213 11812
8e04817f 11813@end table
104c1213 11814
104c1213 11815
8e04817f
AC
11816@noindent
11817@value{GDBN} also supports these special commands for MIPS targets:
104c1213 11818
8e04817f
AC
11819@table @code
11820@item set processor @var{args}
11821@itemx show processor
11822@kindex set processor @var{args}
11823@kindex show processor
11824Use the @code{set processor} command to set the type of MIPS
11825processor when you want to access processor-type-specific registers.
11826For example, @code{set processor @var{r3041}} tells @value{GDBN}
11827to use the CPU registers appropriate for the 3041 chip.
11828Use the @code{show processor} command to see what MIPS processor @value{GDBN}
11829is using. Use the @code{info reg} command to see what registers
11830@value{GDBN} is using.
104c1213 11831
8e04817f
AC
11832@item set mipsfpu double
11833@itemx set mipsfpu single
11834@itemx set mipsfpu none
11835@itemx show mipsfpu
11836@kindex set mipsfpu
11837@kindex show mipsfpu
11838@cindex MIPS remote floating point
11839@cindex floating point, MIPS remote
11840If your target board does not support the MIPS floating point
11841coprocessor, you should use the command @samp{set mipsfpu none} (if you
11842need this, you may wish to put the command in your @value{GDBN} init
11843file). This tells @value{GDBN} how to find the return value of
11844functions which return floating point values. It also allows
11845@value{GDBN} to avoid saving the floating point registers when calling
11846functions on the board. If you are using a floating point coprocessor
11847with only single precision floating point support, as on the @sc{r4650}
11848processor, use the command @samp{set mipsfpu single}. The default
11849double precision floating point coprocessor may be selected using
11850@samp{set mipsfpu double}.
104c1213 11851
8e04817f
AC
11852In previous versions the only choices were double precision or no
11853floating point, so @samp{set mipsfpu on} will select double precision
11854and @samp{set mipsfpu off} will select no floating point.
104c1213 11855
8e04817f
AC
11856As usual, you can inquire about the @code{mipsfpu} variable with
11857@samp{show mipsfpu}.
104c1213 11858
8e04817f
AC
11859@item set remotedebug @var{n}
11860@itemx show remotedebug
11861@kindex set remotedebug@r{, MIPS protocol}
11862@kindex show remotedebug@r{, MIPS protocol}
11863@cindex @code{remotedebug}, MIPS protocol
11864@cindex MIPS @code{remotedebug} protocol
11865@c FIXME! For this to be useful, you must know something about the MIPS
11866@c FIXME...protocol. Where is it described?
11867You can see some debugging information about communications with the board
11868by setting the @code{remotedebug} variable. If you set it to @code{1} using
11869@samp{set remotedebug 1}, every packet is displayed. If you set it
11870to @code{2}, every character is displayed. You can check the current value
11871at any time with the command @samp{show remotedebug}.
104c1213 11872
8e04817f
AC
11873@item set timeout @var{seconds}
11874@itemx set retransmit-timeout @var{seconds}
11875@itemx show timeout
11876@itemx show retransmit-timeout
11877@cindex @code{timeout}, MIPS protocol
11878@cindex @code{retransmit-timeout}, MIPS protocol
11879@kindex set timeout
11880@kindex show timeout
11881@kindex set retransmit-timeout
11882@kindex show retransmit-timeout
11883You can control the timeout used while waiting for a packet, in the MIPS
11884remote protocol, with the @code{set timeout @var{seconds}} command. The
11885default is 5 seconds. Similarly, you can control the timeout used while
11886waiting for an acknowledgement of a packet with the @code{set
11887retransmit-timeout @var{seconds}} command. The default is 3 seconds.
11888You can inspect both values with @code{show timeout} and @code{show
11889retransmit-timeout}. (These commands are @emph{only} available when
11890@value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
104c1213 11891
8e04817f
AC
11892The timeout set by @code{set timeout} does not apply when @value{GDBN}
11893is waiting for your program to stop. In that case, @value{GDBN} waits
11894forever because it has no way of knowing how long the program is going
11895to run before stopping.
11896@end table
104c1213 11897
8e04817f
AC
11898@node PowerPC
11899@subsection PowerPC
104c1213
JM
11900
11901@table @code
104c1213 11902
8e04817f
AC
11903@kindex target dink32
11904@item target dink32 @var{dev}
11905DINK32 ROM monitor.
104c1213 11906
8e04817f
AC
11907@kindex target ppcbug
11908@item target ppcbug @var{dev}
11909@kindex target ppcbug1
11910@item target ppcbug1 @var{dev}
11911PPCBUG ROM monitor for PowerPC.
104c1213 11912
8e04817f
AC
11913@kindex target sds
11914@item target sds @var{dev}
11915SDS monitor, running on a PowerPC board (such as Motorola's ADS).
11916
11917@end table
11918
11919@node PA
11920@subsection HP PA Embedded
104c1213
JM
11921
11922@table @code
11923
8e04817f
AC
11924@kindex target op50n
11925@item target op50n @var{dev}
11926OP50N monitor, running on an OKI HPPA board.
11927
11928@kindex target w89k
11929@item target w89k @var{dev}
11930W89K monitor, running on a Winbond HPPA board.
104c1213
JM
11931
11932@end table
11933
8e04817f
AC
11934@node SH
11935@subsection Hitachi SH
104c1213
JM
11936
11937@table @code
11938
8e04817f
AC
11939@kindex target hms@r{, with Hitachi SH}
11940@item target hms @var{dev}
11941A Hitachi SH board attached via serial line to your host. Use special
11942commands @code{device} and @code{speed} to control the serial line and
11943the communications speed used.
104c1213 11944
8e04817f
AC
11945@kindex target e7000@r{, with Hitachi SH}
11946@item target e7000 @var{dev}
11947E7000 emulator for Hitachi SH.
104c1213 11948
8e04817f
AC
11949@kindex target sh3@r{, with SH}
11950@kindex target sh3e@r{, with SH}
11951@item target sh3 @var{dev}
11952@item target sh3e @var{dev}
11953Hitachi SH-3 and SH-3E target systems.
104c1213 11954
8e04817f 11955@end table
104c1213 11956
8e04817f
AC
11957@node Sparclet
11958@subsection Tsqware Sparclet
104c1213 11959
8e04817f
AC
11960@cindex Sparclet
11961
11962@value{GDBN} enables developers to debug tasks running on
11963Sparclet targets from a Unix host.
11964@value{GDBN} uses code that runs on
11965both the Unix host and on the Sparclet target. The program
11966@code{@value{GDBP}} is installed and executed on the Unix host.
104c1213 11967
8e04817f
AC
11968@table @code
11969@item remotetimeout @var{args}
11970@kindex remotetimeout
11971@value{GDBN} supports the option @code{remotetimeout}.
11972This option is set by the user, and @var{args} represents the number of
11973seconds @value{GDBN} waits for responses.
104c1213
JM
11974@end table
11975
8e04817f
AC
11976@cindex compiling, on Sparclet
11977When compiling for debugging, include the options @samp{-g} to get debug
11978information and @samp{-Ttext} to relocate the program to where you wish to
11979load it on the target. You may also want to add the options @samp{-n} or
11980@samp{-N} in order to reduce the size of the sections. Example:
104c1213 11981
474c8240 11982@smallexample
8e04817f 11983sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
474c8240 11984@end smallexample
104c1213 11985
8e04817f 11986You can use @code{objdump} to verify that the addresses are what you intended:
104c1213 11987
474c8240 11988@smallexample
8e04817f 11989sparclet-aout-objdump --headers --syms prog
474c8240 11990@end smallexample
104c1213 11991
8e04817f
AC
11992@cindex running, on Sparclet
11993Once you have set
11994your Unix execution search path to find @value{GDBN}, you are ready to
11995run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
11996(or @code{sparclet-aout-gdb}, depending on your installation).
104c1213 11997
8e04817f
AC
11998@value{GDBN} comes up showing the prompt:
11999
474c8240 12000@smallexample
8e04817f 12001(gdbslet)
474c8240 12002@end smallexample
104c1213
JM
12003
12004@menu
8e04817f
AC
12005* Sparclet File:: Setting the file to debug
12006* Sparclet Connection:: Connecting to Sparclet
12007* Sparclet Download:: Sparclet download
12008* Sparclet Execution:: Running and debugging
104c1213
JM
12009@end menu
12010
8e04817f
AC
12011@node Sparclet File
12012@subsubsection Setting file to debug
104c1213 12013
8e04817f 12014The @value{GDBN} command @code{file} lets you choose with program to debug.
104c1213 12015
474c8240 12016@smallexample
8e04817f 12017(gdbslet) file prog
474c8240 12018@end smallexample
104c1213 12019
8e04817f
AC
12020@need 1000
12021@value{GDBN} then attempts to read the symbol table of @file{prog}.
12022@value{GDBN} locates
12023the file by searching the directories listed in the command search
12024path.
12025If the file was compiled with debug information (option "-g"), source
12026files will be searched as well.
12027@value{GDBN} locates
12028the source files by searching the directories listed in the directory search
12029path (@pxref{Environment, ,Your program's environment}).
12030If it fails
12031to find a file, it displays a message such as:
104c1213 12032
474c8240 12033@smallexample
8e04817f 12034prog: No such file or directory.
474c8240 12035@end smallexample
104c1213 12036
8e04817f
AC
12037When this happens, add the appropriate directories to the search paths with
12038the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12039@code{target} command again.
104c1213 12040
8e04817f
AC
12041@node Sparclet Connection
12042@subsubsection Connecting to Sparclet
104c1213 12043
8e04817f
AC
12044The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12045To connect to a target on serial port ``@code{ttya}'', type:
104c1213 12046
474c8240 12047@smallexample
8e04817f
AC
12048(gdbslet) target sparclet /dev/ttya
12049Remote target sparclet connected to /dev/ttya
12050main () at ../prog.c:3
474c8240 12051@end smallexample
104c1213 12052
8e04817f
AC
12053@need 750
12054@value{GDBN} displays messages like these:
104c1213 12055
474c8240 12056@smallexample
8e04817f 12057Connected to ttya.
474c8240 12058@end smallexample
104c1213 12059
8e04817f
AC
12060@node Sparclet Download
12061@subsubsection Sparclet download
104c1213 12062
8e04817f
AC
12063@cindex download to Sparclet
12064Once connected to the Sparclet target,
12065you can use the @value{GDBN}
12066@code{load} command to download the file from the host to the target.
12067The file name and load offset should be given as arguments to the @code{load}
12068command.
12069Since the file format is aout, the program must be loaded to the starting
12070address. You can use @code{objdump} to find out what this value is. The load
12071offset is an offset which is added to the VMA (virtual memory address)
12072of each of the file's sections.
12073For instance, if the program
12074@file{prog} was linked to text address 0x1201000, with data at 0x12010160
12075and bss at 0x12010170, in @value{GDBN}, type:
104c1213 12076
474c8240 12077@smallexample
8e04817f
AC
12078(gdbslet) load prog 0x12010000
12079Loading section .text, size 0xdb0 vma 0x12010000
474c8240 12080@end smallexample
104c1213 12081
8e04817f
AC
12082If the code is loaded at a different address then what the program was linked
12083to, you may need to use the @code{section} and @code{add-symbol-file} commands
12084to tell @value{GDBN} where to map the symbol table.
12085
12086@node Sparclet Execution
12087@subsubsection Running and debugging
12088
12089@cindex running and debugging Sparclet programs
12090You can now begin debugging the task using @value{GDBN}'s execution control
12091commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12092manual for the list of commands.
12093
474c8240 12094@smallexample
8e04817f
AC
12095(gdbslet) b main
12096Breakpoint 1 at 0x12010000: file prog.c, line 3.
12097(gdbslet) run
12098Starting program: prog
12099Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
121003 char *symarg = 0;
12101(gdbslet) step
121024 char *execarg = "hello!";
12103(gdbslet)
474c8240 12104@end smallexample
8e04817f
AC
12105
12106@node Sparclite
12107@subsection Fujitsu Sparclite
104c1213
JM
12108
12109@table @code
12110
8e04817f
AC
12111@kindex target sparclite
12112@item target sparclite @var{dev}
12113Fujitsu sparclite boards, used only for the purpose of loading.
12114You must use an additional command to debug the program.
12115For example: target remote @var{dev} using @value{GDBN} standard
12116remote protocol.
104c1213
JM
12117
12118@end table
12119
8e04817f
AC
12120@node ST2000
12121@subsection Tandem ST2000
104c1213 12122
8e04817f
AC
12123@value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12124STDBUG protocol.
104c1213 12125
8e04817f
AC
12126To connect your ST2000 to the host system, see the manufacturer's
12127manual. Once the ST2000 is physically attached, you can run:
104c1213 12128
474c8240 12129@smallexample
8e04817f 12130target st2000 @var{dev} @var{speed}
474c8240 12131@end smallexample
104c1213 12132
8e04817f
AC
12133@noindent
12134to establish it as your debugging environment. @var{dev} is normally
12135the name of a serial device, such as @file{/dev/ttya}, connected to the
12136ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12137connection (for example, to a serial line attached via a terminal
12138concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
104c1213 12139
8e04817f
AC
12140The @code{load} and @code{attach} commands are @emph{not} defined for
12141this target; you must load your program into the ST2000 as you normally
12142would for standalone operation. @value{GDBN} reads debugging information
12143(such as symbols) from a separate, debugging version of the program
12144available on your host computer.
12145@c FIXME!! This is terribly vague; what little content is here is
12146@c basically hearsay.
104c1213 12147
8e04817f
AC
12148@cindex ST2000 auxiliary commands
12149These auxiliary @value{GDBN} commands are available to help you with the ST2000
12150environment:
104c1213 12151
8e04817f
AC
12152@table @code
12153@item st2000 @var{command}
12154@kindex st2000 @var{cmd}
12155@cindex STDBUG commands (ST2000)
12156@cindex commands to STDBUG (ST2000)
12157Send a @var{command} to the STDBUG monitor. See the manufacturer's
12158manual for available commands.
104c1213 12159
8e04817f
AC
12160@item connect
12161@cindex connect (to STDBUG)
12162Connect the controlling terminal to the STDBUG command monitor. When
12163you are done interacting with STDBUG, typing either of two character
12164sequences gets you back to the @value{GDBN} command prompt:
12165@kbd{@key{RET}~.} (Return, followed by tilde and period) or
12166@kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
104c1213
JM
12167@end table
12168
8e04817f
AC
12169@node Z8000
12170@subsection Zilog Z8000
104c1213 12171
8e04817f
AC
12172@cindex Z8000
12173@cindex simulator, Z8000
12174@cindex Zilog Z8000 simulator
104c1213 12175
8e04817f
AC
12176When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12177a Z8000 simulator.
12178
12179For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12180unsegmented variant of the Z8000 architecture) or the Z8001 (the
12181segmented variant). The simulator recognizes which architecture is
12182appropriate by inspecting the object code.
104c1213 12183
8e04817f
AC
12184@table @code
12185@item target sim @var{args}
12186@kindex sim
12187@kindex target sim@r{, with Z8000}
12188Debug programs on a simulated CPU. If the simulator supports setup
12189options, specify them via @var{args}.
104c1213
JM
12190@end table
12191
8e04817f
AC
12192@noindent
12193After specifying this target, you can debug programs for the simulated
12194CPU in the same style as programs for your host computer; use the
12195@code{file} command to load a new program image, the @code{run} command
12196to run your program, and so on.
12197
12198As well as making available all the usual machine registers
12199(@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12200additional items of information as specially named registers:
104c1213
JM
12201
12202@table @code
12203
8e04817f
AC
12204@item cycles
12205Counts clock-ticks in the simulator.
104c1213 12206
8e04817f
AC
12207@item insts
12208Counts instructions run in the simulator.
104c1213 12209
8e04817f
AC
12210@item time
12211Execution time in 60ths of a second.
104c1213 12212
8e04817f 12213@end table
104c1213 12214
8e04817f
AC
12215You can refer to these values in @value{GDBN} expressions with the usual
12216conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12217conditional breakpoint that suspends only after at least 5000
12218simulated clock ticks.
104c1213 12219
8e04817f
AC
12220@node Architectures
12221@section Architectures
104c1213 12222
8e04817f
AC
12223This section describes characteristics of architectures that affect
12224all uses of @value{GDBN} with the architecture, both native and cross.
104c1213 12225
8e04817f
AC
12226@menu
12227* A29K::
12228* Alpha::
12229* MIPS::
12230@end menu
104c1213 12231
8e04817f
AC
12232@node A29K
12233@subsection A29K
104c1213
JM
12234
12235@table @code
104c1213 12236
8e04817f
AC
12237@kindex set rstack_high_address
12238@cindex AMD 29K register stack
12239@cindex register stack, AMD29K
12240@item set rstack_high_address @var{address}
12241On AMD 29000 family processors, registers are saved in a separate
12242@dfn{register stack}. There is no way for @value{GDBN} to determine the
12243extent of this stack. Normally, @value{GDBN} just assumes that the
12244stack is ``large enough''. This may result in @value{GDBN} referencing
12245memory locations that do not exist. If necessary, you can get around
12246this problem by specifying the ending address of the register stack with
12247the @code{set rstack_high_address} command. The argument should be an
12248address, which you probably want to precede with @samp{0x} to specify in
12249hexadecimal.
104c1213 12250
8e04817f
AC
12251@kindex show rstack_high_address
12252@item show rstack_high_address
12253Display the current limit of the register stack, on AMD 29000 family
12254processors.
104c1213 12255
8e04817f 12256@end table
104c1213 12257
8e04817f
AC
12258@node Alpha
12259@subsection Alpha
104c1213 12260
8e04817f 12261See the following section.
104c1213 12262
8e04817f
AC
12263@node MIPS
12264@subsection MIPS
104c1213 12265
8e04817f
AC
12266@cindex stack on Alpha
12267@cindex stack on MIPS
12268@cindex Alpha stack
12269@cindex MIPS stack
12270Alpha- and MIPS-based computers use an unusual stack frame, which
12271sometimes requires @value{GDBN} to search backward in the object code to
12272find the beginning of a function.
104c1213 12273
8e04817f
AC
12274@cindex response time, MIPS debugging
12275To improve response time (especially for embedded applications, where
12276@value{GDBN} may be restricted to a slow serial line for this search)
12277you may want to limit the size of this search, using one of these
12278commands:
104c1213 12279
8e04817f
AC
12280@table @code
12281@cindex @code{heuristic-fence-post} (Alpha, MIPS)
12282@item set heuristic-fence-post @var{limit}
12283Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12284search for the beginning of a function. A value of @var{0} (the
12285default) means there is no limit. However, except for @var{0}, the
12286larger the limit the more bytes @code{heuristic-fence-post} must search
12287and therefore the longer it takes to run.
104c1213 12288
8e04817f
AC
12289@item show heuristic-fence-post
12290Display the current limit.
12291@end table
104c1213
JM
12292
12293@noindent
8e04817f
AC
12294These commands are available @emph{only} when @value{GDBN} is configured
12295for debugging programs on Alpha or MIPS processors.
104c1213 12296
104c1213 12297
8e04817f
AC
12298@node Controlling GDB
12299@chapter Controlling @value{GDBN}
12300
12301You can alter the way @value{GDBN} interacts with you by using the
12302@code{set} command. For commands controlling how @value{GDBN} displays
12303data, see @ref{Print Settings, ,Print settings}. Other settings are
12304described here.
12305
12306@menu
12307* Prompt:: Prompt
12308* Editing:: Command editing
12309* History:: Command history
12310* Screen Size:: Screen size
12311* Numbers:: Numbers
12312* Messages/Warnings:: Optional warnings and messages
12313* Debugging Output:: Optional messages about internal happenings
12314@end menu
12315
12316@node Prompt
12317@section Prompt
104c1213 12318
8e04817f 12319@cindex prompt
104c1213 12320
8e04817f
AC
12321@value{GDBN} indicates its readiness to read a command by printing a string
12322called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12323can change the prompt string with the @code{set prompt} command. For
12324instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12325the prompt in one of the @value{GDBN} sessions so that you can always tell
12326which one you are talking to.
104c1213 12327
8e04817f
AC
12328@emph{Note:} @code{set prompt} does not add a space for you after the
12329prompt you set. This allows you to set a prompt which ends in a space
12330or a prompt that does not.
104c1213 12331
8e04817f
AC
12332@table @code
12333@kindex set prompt
12334@item set prompt @var{newprompt}
12335Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
104c1213 12336
8e04817f
AC
12337@kindex show prompt
12338@item show prompt
12339Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
104c1213
JM
12340@end table
12341
8e04817f
AC
12342@node Editing
12343@section Command editing
12344@cindex readline
12345@cindex command line editing
104c1213 12346
8e04817f
AC
12347@value{GDBN} reads its input commands via the @dfn{readline} interface. This
12348@sc{gnu} library provides consistent behavior for programs which provide a
12349command line interface to the user. Advantages are @sc{gnu} Emacs-style
12350or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12351substitution, and a storage and recall of command history across
12352debugging sessions.
104c1213 12353
8e04817f
AC
12354You may control the behavior of command line editing in @value{GDBN} with the
12355command @code{set}.
104c1213 12356
8e04817f
AC
12357@table @code
12358@kindex set editing
12359@cindex editing
12360@item set editing
12361@itemx set editing on
12362Enable command line editing (enabled by default).
104c1213 12363
8e04817f
AC
12364@item set editing off
12365Disable command line editing.
104c1213 12366
8e04817f
AC
12367@kindex show editing
12368@item show editing
12369Show whether command line editing is enabled.
104c1213
JM
12370@end table
12371
8e04817f
AC
12372@node History
12373@section Command history
12374
12375@value{GDBN} can keep track of the commands you type during your
12376debugging sessions, so that you can be certain of precisely what
12377happened. Use these commands to manage the @value{GDBN} command
12378history facility.
104c1213
JM
12379
12380@table @code
8e04817f
AC
12381@cindex history substitution
12382@cindex history file
12383@kindex set history filename
12384@kindex GDBHISTFILE
12385@item set history filename @var{fname}
12386Set the name of the @value{GDBN} command history file to @var{fname}.
12387This is the file where @value{GDBN} reads an initial command history
12388list, and where it writes the command history from this session when it
12389exits. You can access this list through history expansion or through
12390the history command editing characters listed below. This file defaults
12391to the value of the environment variable @code{GDBHISTFILE}, or to
12392@file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12393is not set.
104c1213 12394
8e04817f
AC
12395@cindex history save
12396@kindex set history save
12397@item set history save
12398@itemx set history save on
12399Record command history in a file, whose name may be specified with the
12400@code{set history filename} command. By default, this option is disabled.
104c1213 12401
8e04817f
AC
12402@item set history save off
12403Stop recording command history in a file.
104c1213 12404
8e04817f
AC
12405@cindex history size
12406@kindex set history size
12407@item set history size @var{size}
12408Set the number of commands which @value{GDBN} keeps in its history list.
12409This defaults to the value of the environment variable
12410@code{HISTSIZE}, or to 256 if this variable is not set.
104c1213
JM
12411@end table
12412
8e04817f
AC
12413@cindex history expansion
12414History expansion assigns special meaning to the character @kbd{!}.
12415@ifset have-readline-appendices
12416@xref{Event Designators}.
12417@end ifset
12418
12419Since @kbd{!} is also the logical not operator in C, history expansion
12420is off by default. If you decide to enable history expansion with the
12421@code{set history expansion on} command, you may sometimes need to
12422follow @kbd{!} (when it is used as logical not, in an expression) with
12423a space or a tab to prevent it from being expanded. The readline
12424history facilities do not attempt substitution on the strings
12425@kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12426
12427The commands to control history expansion are:
104c1213
JM
12428
12429@table @code
8e04817f
AC
12430@kindex set history expansion
12431@item set history expansion on
12432@itemx set history expansion
12433Enable history expansion. History expansion is off by default.
104c1213 12434
8e04817f
AC
12435@item set history expansion off
12436Disable history expansion.
104c1213 12437
8e04817f
AC
12438The readline code comes with more complete documentation of
12439editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12440or @code{vi} may wish to read it.
12441@ifset have-readline-appendices
12442@xref{Command Line Editing}.
12443@end ifset
104c1213 12444
8e04817f
AC
12445@c @group
12446@kindex show history
12447@item show history
12448@itemx show history filename
12449@itemx show history save
12450@itemx show history size
12451@itemx show history expansion
12452These commands display the state of the @value{GDBN} history parameters.
12453@code{show history} by itself displays all four states.
12454@c @end group
12455@end table
12456
12457@table @code
12458@kindex shows
12459@item show commands
12460Display the last ten commands in the command history.
104c1213 12461
8e04817f
AC
12462@item show commands @var{n}
12463Print ten commands centered on command number @var{n}.
12464
12465@item show commands +
12466Print ten commands just after the commands last printed.
104c1213
JM
12467@end table
12468
8e04817f
AC
12469@node Screen Size
12470@section Screen size
12471@cindex size of screen
12472@cindex pauses in output
104c1213 12473
8e04817f
AC
12474Certain commands to @value{GDBN} may produce large amounts of
12475information output to the screen. To help you read all of it,
12476@value{GDBN} pauses and asks you for input at the end of each page of
12477output. Type @key{RET} when you want to continue the output, or @kbd{q}
12478to discard the remaining output. Also, the screen width setting
12479determines when to wrap lines of output. Depending on what is being
12480printed, @value{GDBN} tries to break the line at a readable place,
12481rather than simply letting it overflow onto the following line.
12482
12483Normally @value{GDBN} knows the size of the screen from the terminal
12484driver software. For example, on Unix @value{GDBN} uses the termcap data base
12485together with the value of the @code{TERM} environment variable and the
12486@code{stty rows} and @code{stty cols} settings. If this is not correct,
12487you can override it with the @code{set height} and @code{set
12488width} commands:
12489
12490@table @code
12491@kindex set height
12492@kindex set width
12493@kindex show width
12494@kindex show height
12495@item set height @var{lpp}
12496@itemx show height
12497@itemx set width @var{cpl}
12498@itemx show width
12499These @code{set} commands specify a screen height of @var{lpp} lines and
12500a screen width of @var{cpl} characters. The associated @code{show}
12501commands display the current settings.
104c1213 12502
8e04817f
AC
12503If you specify a height of zero lines, @value{GDBN} does not pause during
12504output no matter how long the output is. This is useful if output is to a
12505file or to an editor buffer.
104c1213 12506
8e04817f
AC
12507Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12508from wrapping its output.
104c1213
JM
12509@end table
12510
8e04817f
AC
12511@node Numbers
12512@section Numbers
12513@cindex number representation
12514@cindex entering numbers
104c1213 12515
8e04817f
AC
12516You can always enter numbers in octal, decimal, or hexadecimal in
12517@value{GDBN} by the usual conventions: octal numbers begin with
12518@samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12519begin with @samp{0x}. Numbers that begin with none of these are, by
12520default, entered in base 10; likewise, the default display for
12521numbers---when no particular format is specified---is base 10. You can
12522change the default base for both input and output with the @code{set
12523radix} command.
104c1213 12524
8e04817f
AC
12525@table @code
12526@kindex set input-radix
12527@item set input-radix @var{base}
12528Set the default base for numeric input. Supported choices
12529for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12530specified either unambiguously or using the current default radix; for
12531example, any of
104c1213 12532
8e04817f
AC
12533@smallexample
12534set radix 012
12535set radix 10.
12536set radix 0xa
12537@end smallexample
104c1213 12538
8e04817f
AC
12539@noindent
12540sets the base to decimal. On the other hand, @samp{set radix 10}
12541leaves the radix unchanged no matter what it was.
104c1213 12542
8e04817f
AC
12543@kindex set output-radix
12544@item set output-radix @var{base}
12545Set the default base for numeric display. Supported choices
12546for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12547specified either unambiguously or using the current default radix.
104c1213 12548
8e04817f
AC
12549@kindex show input-radix
12550@item show input-radix
12551Display the current default base for numeric input.
104c1213 12552
8e04817f
AC
12553@kindex show output-radix
12554@item show output-radix
12555Display the current default base for numeric display.
12556@end table
104c1213 12557
8e04817f
AC
12558@node Messages/Warnings
12559@section Optional warnings and messages
104c1213 12560
8e04817f
AC
12561By default, @value{GDBN} is silent about its inner workings. If you are
12562running on a slow machine, you may want to use the @code{set verbose}
12563command. This makes @value{GDBN} tell you when it does a lengthy
12564internal operation, so you will not think it has crashed.
104c1213 12565
8e04817f
AC
12566Currently, the messages controlled by @code{set verbose} are those
12567which announce that the symbol table for a source file is being read;
12568see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
104c1213 12569
8e04817f
AC
12570@table @code
12571@kindex set verbose
12572@item set verbose on
12573Enables @value{GDBN} output of certain informational messages.
104c1213 12574
8e04817f
AC
12575@item set verbose off
12576Disables @value{GDBN} output of certain informational messages.
104c1213 12577
8e04817f
AC
12578@kindex show verbose
12579@item show verbose
12580Displays whether @code{set verbose} is on or off.
12581@end table
104c1213 12582
8e04817f
AC
12583By default, if @value{GDBN} encounters bugs in the symbol table of an
12584object file, it is silent; but if you are debugging a compiler, you may
12585find this information useful (@pxref{Symbol Errors, ,Errors reading
12586symbol files}).
104c1213 12587
8e04817f 12588@table @code
104c1213 12589
8e04817f
AC
12590@kindex set complaints
12591@item set complaints @var{limit}
12592Permits @value{GDBN} to output @var{limit} complaints about each type of
12593unusual symbols before becoming silent about the problem. Set
12594@var{limit} to zero to suppress all complaints; set it to a large number
12595to prevent complaints from being suppressed.
104c1213 12596
8e04817f
AC
12597@kindex show complaints
12598@item show complaints
12599Displays how many symbol complaints @value{GDBN} is permitted to produce.
104c1213 12600
8e04817f 12601@end table
104c1213 12602
8e04817f
AC
12603By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
12604lot of stupid questions to confirm certain commands. For example, if
12605you try to run a program which is already running:
104c1213 12606
474c8240 12607@smallexample
8e04817f
AC
12608(@value{GDBP}) run
12609The program being debugged has been started already.
12610Start it from the beginning? (y or n)
474c8240 12611@end smallexample
104c1213 12612
8e04817f
AC
12613If you are willing to unflinchingly face the consequences of your own
12614commands, you can disable this ``feature'':
104c1213 12615
8e04817f 12616@table @code
104c1213 12617
8e04817f
AC
12618@kindex set confirm
12619@cindex flinching
12620@cindex confirmation
12621@cindex stupid questions
12622@item set confirm off
12623Disables confirmation requests.
104c1213 12624
8e04817f
AC
12625@item set confirm on
12626Enables confirmation requests (the default).
104c1213 12627
8e04817f
AC
12628@kindex show confirm
12629@item show confirm
12630Displays state of confirmation requests.
12631
12632@end table
104c1213 12633
8e04817f
AC
12634@node Debugging Output
12635@section Optional messages about internal happenings
104c1213 12636@table @code
8e04817f
AC
12637@kindex set debug arch
12638@item set debug arch
12639Turns on or off display of gdbarch debugging info. The default is off
12640@kindex show debug arch
12641@item show debug arch
12642Displays the current state of displaying gdbarch debugging info.
12643@kindex set debug event
12644@item set debug event
12645Turns on or off display of @value{GDBN} event debugging info. The
12646default is off.
12647@kindex show debug event
12648@item show debug event
12649Displays the current state of displaying @value{GDBN} event debugging
12650info.
12651@kindex set debug expression
12652@item set debug expression
12653Turns on or off display of @value{GDBN} expression debugging info. The
12654default is off.
12655@kindex show debug expression
12656@item show debug expression
12657Displays the current state of displaying @value{GDBN} expression
12658debugging info.
12659@kindex set debug overload
12660@item set debug overload
12661Turns on or off display of @value{GDBN} C@t{++} overload debugging
12662info. This includes info such as ranking of functions, etc. The default
12663is off.
12664@kindex show debug overload
12665@item show debug overload
12666Displays the current state of displaying @value{GDBN} C@t{++} overload
12667debugging info.
12668@kindex set debug remote
12669@cindex packets, reporting on stdout
12670@cindex serial connections, debugging
12671@item set debug remote
12672Turns on or off display of reports on all packets sent back and forth across
12673the serial line to the remote machine. The info is printed on the
12674@value{GDBN} standard output stream. The default is off.
12675@kindex show debug remote
12676@item show debug remote
12677Displays the state of display of remote packets.
12678@kindex set debug serial
12679@item set debug serial
12680Turns on or off display of @value{GDBN} serial debugging info. The
12681default is off.
12682@kindex show debug serial
12683@item show debug serial
12684Displays the current state of displaying @value{GDBN} serial debugging
12685info.
12686@kindex set debug target
12687@item set debug target
12688Turns on or off display of @value{GDBN} target debugging info. This info
12689includes what is going on at the target level of GDB, as it happens. The
12690default is off.
12691@kindex show debug target
12692@item show debug target
12693Displays the current state of displaying @value{GDBN} target debugging
12694info.
12695@kindex set debug varobj
12696@item set debug varobj
12697Turns on or off display of @value{GDBN} variable object debugging
12698info. The default is off.
12699@kindex show debug varobj
12700@item show debug varobj
12701Displays the current state of displaying @value{GDBN} variable object
12702debugging info.
12703@end table
104c1213 12704
8e04817f
AC
12705@node Sequences
12706@chapter Canned Sequences of Commands
104c1213 12707
8e04817f
AC
12708Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
12709command lists}), @value{GDBN} provides two ways to store sequences of
12710commands for execution as a unit: user-defined commands and command
12711files.
104c1213 12712
8e04817f
AC
12713@menu
12714* Define:: User-defined commands
12715* Hooks:: User-defined command hooks
12716* Command Files:: Command files
12717* Output:: Commands for controlled output
12718@end menu
104c1213 12719
8e04817f
AC
12720@node Define
12721@section User-defined commands
104c1213 12722
8e04817f
AC
12723@cindex user-defined command
12724A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
12725which you assign a new name as a command. This is done with the
12726@code{define} command. User commands may accept up to 10 arguments
12727separated by whitespace. Arguments are accessed within the user command
12728via @var{$arg0@dots{}$arg9}. A trivial example:
104c1213 12729
8e04817f
AC
12730@smallexample
12731define adder
12732 print $arg0 + $arg1 + $arg2
12733@end smallexample
104c1213
JM
12734
12735@noindent
8e04817f 12736To execute the command use:
104c1213 12737
8e04817f
AC
12738@smallexample
12739adder 1 2 3
12740@end smallexample
104c1213 12741
8e04817f
AC
12742@noindent
12743This defines the command @code{adder}, which prints the sum of
12744its three arguments. Note the arguments are text substitutions, so they may
12745reference variables, use complex expressions, or even perform inferior
12746functions calls.
104c1213
JM
12747
12748@table @code
104c1213 12749
8e04817f
AC
12750@kindex define
12751@item define @var{commandname}
12752Define a command named @var{commandname}. If there is already a command
12753by that name, you are asked to confirm that you want to redefine it.
104c1213 12754
8e04817f
AC
12755The definition of the command is made up of other @value{GDBN} command lines,
12756which are given following the @code{define} command. The end of these
12757commands is marked by a line containing @code{end}.
104c1213 12758
8e04817f
AC
12759@kindex if
12760@kindex else
12761@item if
12762Takes a single argument, which is an expression to evaluate.
12763It is followed by a series of commands that are executed
12764only if the expression is true (nonzero).
12765There can then optionally be a line @code{else}, followed
12766by a series of commands that are only executed if the expression
12767was false. The end of the list is marked by a line containing @code{end}.
104c1213 12768
8e04817f
AC
12769@kindex while
12770@item while
12771The syntax is similar to @code{if}: the command takes a single argument,
12772which is an expression to evaluate, and must be followed by the commands to
12773execute, one per line, terminated by an @code{end}.
12774The commands are executed repeatedly as long as the expression
12775evaluates to true.
104c1213 12776
8e04817f
AC
12777@kindex document
12778@item document @var{commandname}
12779Document the user-defined command @var{commandname}, so that it can be
12780accessed by @code{help}. The command @var{commandname} must already be
12781defined. This command reads lines of documentation just as @code{define}
12782reads the lines of the command definition, ending with @code{end}.
12783After the @code{document} command is finished, @code{help} on command
12784@var{commandname} displays the documentation you have written.
104c1213 12785
8e04817f
AC
12786You may use the @code{document} command again to change the
12787documentation of a command. Redefining the command with @code{define}
12788does not change the documentation.
104c1213 12789
8e04817f
AC
12790@kindex help user-defined
12791@item help user-defined
12792List all user-defined commands, with the first line of the documentation
12793(if any) for each.
104c1213 12794
8e04817f
AC
12795@kindex show user
12796@item show user
12797@itemx show user @var{commandname}
12798Display the @value{GDBN} commands used to define @var{commandname} (but
12799not its documentation). If no @var{commandname} is given, display the
12800definitions for all user-defined commands.
104c1213 12801
20f01a46
DH
12802@kindex show max-user-call-depth
12803@kindex set max-user-call-depth
12804@item show max-user-call-depth
5ca0cb28
DH
12805@itemx set max-user-call-depth
12806The value of @code{max-user-call-depth} controls how many recursion
12807levels are allowed in user-defined commands before GDB suspects an
12808infinite recursion and aborts the command.
20f01a46 12809
104c1213
JM
12810@end table
12811
8e04817f
AC
12812When user-defined commands are executed, the
12813commands of the definition are not printed. An error in any command
12814stops execution of the user-defined command.
104c1213 12815
8e04817f
AC
12816If used interactively, commands that would ask for confirmation proceed
12817without asking when used inside a user-defined command. Many @value{GDBN}
12818commands that normally print messages to say what they are doing omit the
12819messages when used in a user-defined command.
104c1213 12820
8e04817f
AC
12821@node Hooks
12822@section User-defined command hooks
12823@cindex command hooks
12824@cindex hooks, for commands
12825@cindex hooks, pre-command
104c1213 12826
8e04817f
AC
12827@kindex hook
12828@kindex hook-
12829You may define @dfn{hooks}, which are a special kind of user-defined
12830command. Whenever you run the command @samp{foo}, if the user-defined
12831command @samp{hook-foo} exists, it is executed (with no arguments)
12832before that command.
104c1213 12833
8e04817f
AC
12834@cindex hooks, post-command
12835@kindex hookpost
12836@kindex hookpost-
12837A hook may also be defined which is run after the command you executed.
12838Whenever you run the command @samp{foo}, if the user-defined command
12839@samp{hookpost-foo} exists, it is executed (with no arguments) after
12840that command. Post-execution hooks may exist simultaneously with
12841pre-execution hooks, for the same command.
104c1213 12842
8e04817f
AC
12843It is valid for a hook to call the command which it hooks. If this
12844occurs, the hook is not re-executed, thereby avoiding infinte recursion.
104c1213 12845
8e04817f
AC
12846@c It would be nice if hookpost could be passed a parameter indicating
12847@c if the command it hooks executed properly or not. FIXME!
104c1213 12848
8e04817f
AC
12849@kindex stop@r{, a pseudo-command}
12850In addition, a pseudo-command, @samp{stop} exists. Defining
12851(@samp{hook-stop}) makes the associated commands execute every time
12852execution stops in your program: before breakpoint commands are run,
12853displays are printed, or the stack frame is printed.
104c1213 12854
8e04817f
AC
12855For example, to ignore @code{SIGALRM} signals while
12856single-stepping, but treat them normally during normal execution,
12857you could define:
104c1213 12858
474c8240 12859@smallexample
8e04817f
AC
12860define hook-stop
12861handle SIGALRM nopass
12862end
104c1213 12863
8e04817f
AC
12864define hook-run
12865handle SIGALRM pass
12866end
104c1213 12867
8e04817f
AC
12868define hook-continue
12869handle SIGLARM pass
12870end
474c8240 12871@end smallexample
104c1213 12872
8e04817f
AC
12873As a further example, to hook at the begining and end of the @code{echo}
12874command, and to add extra text to the beginning and end of the message,
12875you could define:
104c1213 12876
474c8240 12877@smallexample
8e04817f
AC
12878define hook-echo
12879echo <<<---
12880end
104c1213 12881
8e04817f
AC
12882define hookpost-echo
12883echo --->>>\n
12884end
104c1213 12885
8e04817f
AC
12886(@value{GDBP}) echo Hello World
12887<<<---Hello World--->>>
12888(@value{GDBP})
104c1213 12889
474c8240 12890@end smallexample
104c1213 12891
8e04817f
AC
12892You can define a hook for any single-word command in @value{GDBN}, but
12893not for command aliases; you should define a hook for the basic command
12894name, e.g. @code{backtrace} rather than @code{bt}.
12895@c FIXME! So how does Joe User discover whether a command is an alias
12896@c or not?
12897If an error occurs during the execution of your hook, execution of
12898@value{GDBN} commands stops and @value{GDBN} issues a prompt
12899(before the command that you actually typed had a chance to run).
104c1213 12900
8e04817f
AC
12901If you try to define a hook which does not match any known command, you
12902get a warning from the @code{define} command.
c906108c 12903
8e04817f
AC
12904@node Command Files
12905@section Command files
c906108c 12906
8e04817f
AC
12907@cindex command files
12908A command file for @value{GDBN} is a file of lines that are @value{GDBN}
12909commands. Comments (lines starting with @kbd{#}) may also be included.
12910An empty line in a command file does nothing; it does not mean to repeat
12911the last command, as it would from the terminal.
c906108c 12912
8e04817f
AC
12913@cindex init file
12914@cindex @file{.gdbinit}
12915@cindex @file{gdb.ini}
12916When you start @value{GDBN}, it automatically executes commands from its
12917@dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
12918port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
12919limitations of file names imposed by DOS filesystems.}.
12920During startup, @value{GDBN} does the following:
c906108c 12921
8e04817f
AC
12922@enumerate
12923@item
12924Reads the init file (if any) in your home directory@footnote{On
12925DOS/Windows systems, the home directory is the one pointed to by the
12926@code{HOME} environment variable.}.
c906108c 12927
8e04817f
AC
12928@item
12929Processes command line options and operands.
c906108c 12930
8e04817f
AC
12931@item
12932Reads the init file (if any) in the current working directory.
c906108c 12933
8e04817f
AC
12934@item
12935Reads command files specified by the @samp{-x} option.
12936@end enumerate
c906108c 12937
8e04817f
AC
12938The init file in your home directory can set options (such as @samp{set
12939complaints}) that affect subsequent processing of command line options
12940and operands. Init files are not executed if you use the @samp{-nx}
12941option (@pxref{Mode Options, ,Choosing modes}).
c906108c 12942
8e04817f
AC
12943@cindex init file name
12944On some configurations of @value{GDBN}, the init file is known by a
12945different name (these are typically environments where a specialized
12946form of @value{GDBN} may need to coexist with other forms, hence a
12947different name for the specialized version's init file). These are the
12948environments with special init file names:
c906108c 12949
8e04817f
AC
12950@cindex @file{.vxgdbinit}
12951@itemize @bullet
12952@item
12953VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
c906108c 12954
8e04817f
AC
12955@cindex @file{.os68gdbinit}
12956@item
12957OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
c906108c 12958
8e04817f
AC
12959@cindex @file{.esgdbinit}
12960@item
12961ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
12962@end itemize
c906108c 12963
8e04817f
AC
12964You can also request the execution of a command file with the
12965@code{source} command:
c906108c 12966
8e04817f
AC
12967@table @code
12968@kindex source
12969@item source @var{filename}
12970Execute the command file @var{filename}.
c906108c
SS
12971@end table
12972
8e04817f
AC
12973The lines in a command file are executed sequentially. They are not
12974printed as they are executed. An error in any command terminates execution
12975of the command file.
c906108c 12976
8e04817f
AC
12977Commands that would ask for confirmation if used interactively proceed
12978without asking when used in a command file. Many @value{GDBN} commands that
12979normally print messages to say what they are doing omit the messages
12980when called from command files.
c906108c 12981
8e04817f
AC
12982@value{GDBN} also accepts command input from standard input. In this
12983mode, normal output goes to standard output and error output goes to
12984standard error. Errors in a command file supplied on standard input do
12985not terminate execution of the command file --- execution continues with
12986the next command.
c906108c 12987
474c8240 12988@smallexample
8e04817f 12989gdb < cmds > log 2>&1
474c8240 12990@end smallexample
c906108c 12991
8e04817f
AC
12992(The syntax above will vary depending on the shell used.) This example
12993will execute commands from the file @file{cmds}. All output and errors
12994would be directed to @file{log}.
c906108c 12995
8e04817f
AC
12996@node Output
12997@section Commands for controlled output
c906108c 12998
8e04817f
AC
12999During the execution of a command file or a user-defined command, normal
13000@value{GDBN} output is suppressed; the only output that appears is what is
13001explicitly printed by the commands in the definition. This section
13002describes three commands useful for generating exactly the output you
13003want.
c906108c
SS
13004
13005@table @code
8e04817f
AC
13006@kindex echo
13007@item echo @var{text}
13008@c I do not consider backslash-space a standard C escape sequence
13009@c because it is not in ANSI.
13010Print @var{text}. Nonprinting characters can be included in
13011@var{text} using C escape sequences, such as @samp{\n} to print a
13012newline. @strong{No newline is printed unless you specify one.}
13013In addition to the standard C escape sequences, a backslash followed
13014by a space stands for a space. This is useful for displaying a
13015string with spaces at the beginning or the end, since leading and
13016trailing spaces are otherwise trimmed from all arguments.
13017To print @samp{@w{ }and foo =@w{ }}, use the command
13018@samp{echo \@w{ }and foo = \@w{ }}.
c906108c 13019
8e04817f
AC
13020A backslash at the end of @var{text} can be used, as in C, to continue
13021the command onto subsequent lines. For example,
c906108c 13022
474c8240 13023@smallexample
8e04817f
AC
13024echo This is some text\n\
13025which is continued\n\
13026onto several lines.\n
474c8240 13027@end smallexample
c906108c 13028
8e04817f 13029produces the same output as
c906108c 13030
474c8240 13031@smallexample
8e04817f
AC
13032echo This is some text\n
13033echo which is continued\n
13034echo onto several lines.\n
474c8240 13035@end smallexample
c906108c 13036
8e04817f
AC
13037@kindex output
13038@item output @var{expression}
13039Print the value of @var{expression} and nothing but that value: no
13040newlines, no @samp{$@var{nn} = }. The value is not entered in the
13041value history either. @xref{Expressions, ,Expressions}, for more information
13042on expressions.
c906108c 13043
8e04817f
AC
13044@item output/@var{fmt} @var{expression}
13045Print the value of @var{expression} in format @var{fmt}. You can use
13046the same formats as for @code{print}. @xref{Output Formats,,Output
13047formats}, for more information.
c906108c 13048
8e04817f
AC
13049@kindex printf
13050@item printf @var{string}, @var{expressions}@dots{}
13051Print the values of the @var{expressions} under the control of
13052@var{string}. The @var{expressions} are separated by commas and may be
13053either numbers or pointers. Their values are printed as specified by
13054@var{string}, exactly as if your program were to execute the C
13055subroutine
13056@c FIXME: the above implies that at least all ANSI C formats are
13057@c supported, but it isn't true: %E and %G don't work (or so it seems).
13058@c Either this is a bug, or the manual should document what formats are
13059@c supported.
c906108c 13060
474c8240 13061@smallexample
8e04817f 13062printf (@var{string}, @var{expressions}@dots{});
474c8240 13063@end smallexample
c906108c 13064
8e04817f 13065For example, you can print two values in hex like this:
c906108c 13066
8e04817f
AC
13067@smallexample
13068printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13069@end smallexample
c906108c 13070
8e04817f
AC
13071The only backslash-escape sequences that you can use in the format
13072string are the simple ones that consist of backslash followed by a
13073letter.
c906108c
SS
13074@end table
13075
8e04817f
AC
13076@node TUI
13077@chapter @value{GDBN} Text User Interface
13078@cindex TUI
c906108c 13079
8e04817f
AC
13080@menu
13081* TUI Overview:: TUI overview
13082* TUI Keys:: TUI key bindings
13083* TUI Commands:: TUI specific commands
13084* TUI Configuration:: TUI configuration variables
13085@end menu
c906108c 13086
8e04817f
AC
13087The @value{GDBN} Text User Interface, TUI in short,
13088is a terminal interface which uses the @code{curses} library
13089to show the source file, the assembly output, the program registers
13090and @value{GDBN} commands in separate text windows.
13091The TUI is available only when @value{GDBN} is configured
13092with the @code{--enable-tui} configure option (@pxref{Configure Options}).
c906108c 13093
8e04817f
AC
13094@node TUI Overview
13095@section TUI overview
c906108c 13096
8e04817f
AC
13097The TUI has two display modes that can be switched while
13098@value{GDBN} runs:
c906108c 13099
8e04817f
AC
13100@itemize @bullet
13101@item
13102A curses (or TUI) mode in which it displays several text
13103windows on the terminal.
c906108c 13104
8e04817f
AC
13105@item
13106A standard mode which corresponds to the @value{GDBN} configured without
13107the TUI.
13108@end itemize
c906108c 13109
8e04817f
AC
13110In the TUI mode, @value{GDBN} can display several text window
13111on the terminal:
c906108c 13112
8e04817f
AC
13113@table @emph
13114@item command
13115This window is the @value{GDBN} command window with the @value{GDBN}
13116prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13117managed using readline but through the TUI. The @emph{command}
13118window is always visible.
c906108c 13119
8e04817f
AC
13120@item source
13121The source window shows the source file of the program. The current
13122line as well as active breakpoints are displayed in this window.
13123The current program position is shown with the @samp{>} marker and
13124active breakpoints are shown with @samp{*} markers.
c906108c 13125
8e04817f
AC
13126@item assembly
13127The assembly window shows the disassembly output of the program.
c906108c 13128
8e04817f
AC
13129@item register
13130This window shows the processor registers. It detects when
13131a register is changed and when this is the case, registers that have
13132changed are highlighted.
c906108c 13133
c906108c
SS
13134@end table
13135
8e04817f
AC
13136The source, assembly and register windows are attached to the thread
13137and the frame position. They are updated when the current thread
13138changes, when the frame changes or when the program counter changes.
13139These three windows are arranged by the TUI according to several
13140layouts. The layout defines which of these three windows are visible.
13141The following layouts are available:
c906108c 13142
8e04817f
AC
13143@itemize @bullet
13144@item
13145source
2df3850c 13146
8e04817f
AC
13147@item
13148assembly
13149
13150@item
13151source and assembly
13152
13153@item
13154source and registers
c906108c 13155
8e04817f
AC
13156@item
13157assembly and registers
2df3850c 13158
8e04817f 13159@end itemize
c906108c 13160
8e04817f
AC
13161@node TUI Keys
13162@section TUI Key Bindings
13163@cindex TUI key bindings
c906108c 13164
8e04817f
AC
13165The TUI installs several key bindings in the readline keymaps
13166(@pxref{Command Line Editing}).
13167They allow to leave or enter in the TUI mode or they operate
13168directly on the TUI layout and windows. The following key bindings
13169are installed for both TUI mode and the @value{GDBN} standard mode.
c906108c 13170
8e04817f
AC
13171@table @kbd
13172@kindex C-x C-a
13173@item C-x C-a
13174@kindex C-x a
13175@itemx C-x a
13176@kindex C-x A
13177@itemx C-x A
13178Enter or leave the TUI mode. When the TUI mode is left,
13179the curses window management is left and @value{GDBN} operates using
13180its standard mode writing on the terminal directly. When the TUI
13181mode is entered, the control is given back to the curses windows.
13182The screen is then refreshed.
c906108c 13183
8e04817f
AC
13184@kindex C-x 1
13185@item C-x 1
13186Use a TUI layout with only one window. The layout will
13187either be @samp{source} or @samp{assembly}. When the TUI mode
13188is not active, it will switch to the TUI mode.
2df3850c 13189
8e04817f 13190Think of this key binding as the Emacs @kbd{C-x 1} binding.
c906108c 13191
8e04817f
AC
13192@kindex C-x 2
13193@item C-x 2
13194Use a TUI layout with at least two windows. When the current
13195layout shows already two windows, a next layout with two windows is used.
13196When a new layout is chosen, one window will always be common to the
13197previous layout and the new one.
c906108c 13198
8e04817f 13199Think of it as the Emacs @kbd{C-x 2} binding.
2df3850c 13200
c906108c
SS
13201@end table
13202
8e04817f 13203The following key bindings are handled only by the TUI mode:
5d161b24 13204
8e04817f
AC
13205@table @key
13206@kindex PgUp
13207@item PgUp
13208Scroll the active window one page up.
c906108c 13209
8e04817f
AC
13210@kindex PgDn
13211@item PgDn
13212Scroll the active window one page down.
c906108c 13213
8e04817f
AC
13214@kindex Up
13215@item Up
13216Scroll the active window one line up.
c906108c 13217
8e04817f
AC
13218@kindex Down
13219@item Down
13220Scroll the active window one line down.
c906108c 13221
8e04817f
AC
13222@kindex Left
13223@item Left
13224Scroll the active window one column left.
c906108c 13225
8e04817f
AC
13226@kindex Right
13227@item Right
13228Scroll the active window one column right.
c906108c 13229
8e04817f
AC
13230@kindex C-L
13231@item C-L
13232Refresh the screen.
c906108c 13233
8e04817f 13234@end table
c906108c 13235
8e04817f
AC
13236In the TUI mode, the arrow keys are used by the active window
13237for scrolling. This means they are not available for readline. It is
13238necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13239@key{C-b} and @key{C-f}.
13240
13241@node TUI Commands
13242@section TUI specific commands
13243@cindex TUI commands
13244
13245The TUI has specific commands to control the text windows.
13246These commands are always available, that is they do not depend on
13247the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13248is in the standard mode, using these commands will automatically switch
13249in the TUI mode.
c906108c
SS
13250
13251@table @code
8e04817f
AC
13252@item layout next
13253@kindex layout next
13254Display the next layout.
2df3850c 13255
8e04817f
AC
13256@item layout prev
13257@kindex layout prev
13258Display the previous layout.
c906108c 13259
8e04817f
AC
13260@item layout src
13261@kindex layout src
13262Display the source window only.
c906108c 13263
8e04817f
AC
13264@item layout asm
13265@kindex layout asm
13266Display the assembly window only.
c906108c 13267
8e04817f
AC
13268@item layout split
13269@kindex layout split
13270Display the source and assembly window.
c906108c 13271
8e04817f
AC
13272@item layout regs
13273@kindex layout regs
13274Display the register window together with the source or assembly window.
13275
13276@item focus next | prev | src | asm | regs | split
13277@kindex focus
13278Set the focus to the named window.
13279This command allows to change the active window so that scrolling keys
13280can be affected to another window.
c906108c 13281
8e04817f
AC
13282@item refresh
13283@kindex refresh
13284Refresh the screen. This is similar to using @key{C-L} key.
c906108c 13285
8e04817f
AC
13286@item update
13287@kindex update
13288Update the source window and the current execution point.
c906108c 13289
8e04817f
AC
13290@item winheight @var{name} +@var{count}
13291@itemx winheight @var{name} -@var{count}
13292@kindex winheight
13293Change the height of the window @var{name} by @var{count}
13294lines. Positive counts increase the height, while negative counts
13295decrease it.
2df3850c 13296
c906108c
SS
13297@end table
13298
8e04817f
AC
13299@node TUI Configuration
13300@section TUI configuration variables
13301@cindex TUI configuration variables
c906108c 13302
8e04817f
AC
13303The TUI has several configuration variables that control the
13304appearance of windows on the terminal.
c906108c 13305
8e04817f
AC
13306@table @code
13307@item set tui border-kind @var{kind}
13308@kindex set tui border-kind
13309Select the border appearance for the source, assembly and register windows.
13310The possible values are the following:
13311@table @code
13312@item space
13313Use a space character to draw the border.
c906108c 13314
8e04817f
AC
13315@item ascii
13316Use ascii characters + - and | to draw the border.
c906108c 13317
8e04817f
AC
13318@item acs
13319Use the Alternate Character Set to draw the border. The border is
13320drawn using character line graphics if the terminal supports them.
c78b4128 13321
8e04817f 13322@end table
c78b4128 13323
8e04817f
AC
13324@item set tui active-border-mode @var{mode}
13325@kindex set tui active-border-mode
13326Select the attributes to display the border of the active window.
13327The possible values are @code{normal}, @code{standout}, @code{reverse},
13328@code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
c78b4128 13329
8e04817f
AC
13330@item set tui border-mode @var{mode}
13331@kindex set tui border-mode
13332Select the attributes to display the border of other windows.
13333The @var{mode} can be one of the following:
13334@table @code
13335@item normal
13336Use normal attributes to display the border.
c906108c 13337
8e04817f
AC
13338@item standout
13339Use standout mode.
c906108c 13340
8e04817f
AC
13341@item reverse
13342Use reverse video mode.
c906108c 13343
8e04817f
AC
13344@item half
13345Use half bright mode.
c906108c 13346
8e04817f
AC
13347@item half-standout
13348Use half bright and standout mode.
c906108c 13349
8e04817f
AC
13350@item bold
13351Use extra bright or bold mode.
c78b4128 13352
8e04817f
AC
13353@item bold-standout
13354Use extra bright or bold and standout mode.
c78b4128 13355
8e04817f 13356@end table
c78b4128 13357
8e04817f 13358@end table
c78b4128 13359
8e04817f
AC
13360@node Emacs
13361@chapter Using @value{GDBN} under @sc{gnu} Emacs
c78b4128 13362
8e04817f
AC
13363@cindex Emacs
13364@cindex @sc{gnu} Emacs
13365A special interface allows you to use @sc{gnu} Emacs to view (and
13366edit) the source files for the program you are debugging with
13367@value{GDBN}.
c906108c 13368
8e04817f
AC
13369To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13370executable file you want to debug as an argument. This command starts
13371@value{GDBN} as a subprocess of Emacs, with input and output through a newly
13372created Emacs buffer.
13373@c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
c906108c 13374
8e04817f
AC
13375Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13376things:
c906108c 13377
8e04817f
AC
13378@itemize @bullet
13379@item
13380All ``terminal'' input and output goes through the Emacs buffer.
13381@end itemize
c906108c 13382
8e04817f
AC
13383This applies both to @value{GDBN} commands and their output, and to the input
13384and output done by the program you are debugging.
bf0184be 13385
8e04817f
AC
13386This is useful because it means that you can copy the text of previous
13387commands and input them again; you can even use parts of the output
13388in this way.
bf0184be 13389
8e04817f
AC
13390All the facilities of Emacs' Shell mode are available for interacting
13391with your program. In particular, you can send signals the usual
13392way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13393stop.
bf0184be 13394
8e04817f 13395@itemize @bullet
bf0184be 13396@item
8e04817f
AC
13397@value{GDBN} displays source code through Emacs.
13398@end itemize
bf0184be 13399
8e04817f
AC
13400Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13401source file for that frame and puts an arrow (@samp{=>}) at the
13402left margin of the current line. Emacs uses a separate buffer for
13403source display, and splits the screen to show both your @value{GDBN} session
13404and the source.
bf0184be 13405
8e04817f
AC
13406Explicit @value{GDBN} @code{list} or search commands still produce output as
13407usual, but you probably have no reason to use them from Emacs.
c906108c 13408
8e04817f
AC
13409@quotation
13410@emph{Warning:} If the directory where your program resides is not your
13411current directory, it can be easy to confuse Emacs about the location of
13412the source files, in which case the auxiliary display buffer does not
13413appear to show your source. @value{GDBN} can find programs by searching your
13414environment's @code{PATH} variable, so the @value{GDBN} input and output
13415session proceeds normally; but Emacs does not get enough information
13416back from @value{GDBN} to locate the source files in this situation. To
13417avoid this problem, either start @value{GDBN} mode from the directory where
13418your program resides, or specify an absolute file name when prompted for the
13419@kbd{M-x gdb} argument.
c906108c 13420
8e04817f
AC
13421A similar confusion can result if you use the @value{GDBN} @code{file} command to
13422switch to debugging a program in some other location, from an existing
13423@value{GDBN} buffer in Emacs.
13424@end quotation
13425
13426By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
13427you need to call @value{GDBN} by a different name (for example, if you keep
13428several configurations around, with different names) you can set the
13429Emacs variable @code{gdb-command-name}; for example,
13430
474c8240 13431@smallexample
8e04817f 13432(setq gdb-command-name "mygdb")
474c8240 13433@end smallexample
8e04817f
AC
13434
13435@noindent
13436(preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
13437in your @file{.emacs} file) makes Emacs call the program named
13438``@code{mygdb}'' instead.
13439
13440In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
13441addition to the standard Shell mode commands:
c906108c 13442
8e04817f
AC
13443@table @kbd
13444@item C-h m
13445Describe the features of Emacs' @value{GDBN} Mode.
c906108c 13446
8e04817f
AC
13447@item M-s
13448Execute to another source line, like the @value{GDBN} @code{step} command; also
13449update the display window to show the current file and location.
c906108c 13450
8e04817f
AC
13451@item M-n
13452Execute to next source line in this function, skipping all function
13453calls, like the @value{GDBN} @code{next} command. Then update the display window
13454to show the current file and location.
c906108c 13455
8e04817f
AC
13456@item M-i
13457Execute one instruction, like the @value{GDBN} @code{stepi} command; update
13458display window accordingly.
c906108c 13459
8e04817f
AC
13460@item M-x gdb-nexti
13461Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
13462display window accordingly.
c906108c 13463
8e04817f
AC
13464@item C-c C-f
13465Execute until exit from the selected stack frame, like the @value{GDBN}
13466@code{finish} command.
c906108c 13467
8e04817f
AC
13468@item M-c
13469Continue execution of your program, like the @value{GDBN} @code{continue}
13470command.
b433d00b 13471
8e04817f 13472@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
b433d00b 13473
8e04817f
AC
13474@item M-u
13475Go up the number of frames indicated by the numeric argument
13476(@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
13477like the @value{GDBN} @code{up} command.
b433d00b 13478
8e04817f 13479@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
c906108c 13480
8e04817f
AC
13481@item M-d
13482Go down the number of frames indicated by the numeric argument, like the
13483@value{GDBN} @code{down} command.
c906108c 13484
8e04817f 13485@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
c906108c 13486
8e04817f
AC
13487@item C-x &
13488Read the number where the cursor is positioned, and insert it at the end
13489of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
13490around an address that was displayed earlier, type @kbd{disassemble};
13491then move the cursor to the address display, and pick up the
13492argument for @code{disassemble} by typing @kbd{C-x &}.
c906108c 13493
8e04817f
AC
13494You can customize this further by defining elements of the list
13495@code{gdb-print-command}; once it is defined, you can format or
13496otherwise process numbers picked up by @kbd{C-x &} before they are
13497inserted. A numeric argument to @kbd{C-x &} indicates that you
13498wish special formatting, and also acts as an index to pick an element of the
13499list. If the list element is a string, the number to be inserted is
13500formatted using the Emacs function @code{format}; otherwise the number
13501is passed as an argument to the corresponding list element.
13502@end table
c906108c 13503
8e04817f
AC
13504In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
13505tells @value{GDBN} to set a breakpoint on the source line point is on.
c906108c 13506
8e04817f
AC
13507If you accidentally delete the source-display buffer, an easy way to get
13508it back is to type the command @code{f} in the @value{GDBN} buffer, to
13509request a frame display; when you run under Emacs, this recreates
13510the source buffer if necessary to show you the context of the current
13511frame.
c906108c 13512
8e04817f
AC
13513The source files displayed in Emacs are in ordinary Emacs buffers
13514which are visiting the source files in the usual way. You can edit
13515the files with these buffers if you wish; but keep in mind that @value{GDBN}
13516communicates with Emacs in terms of line numbers. If you add or
13517delete lines from the text, the line numbers that @value{GDBN} knows cease
13518to correspond properly with the code.
c906108c 13519
8e04817f
AC
13520@c The following dropped because Epoch is nonstandard. Reactivate
13521@c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
13522@ignore
13523@kindex Emacs Epoch environment
13524@kindex Epoch
13525@kindex inspect
c906108c 13526
8e04817f
AC
13527Version 18 of @sc{gnu} Emacs has a built-in window system
13528called the @code{epoch}
13529environment. Users of this environment can use a new command,
13530@code{inspect} which performs identically to @code{print} except that
13531each value is printed in its own window.
13532@end ignore
c906108c 13533
8e04817f
AC
13534@include annotate.texi
13535@include gdbmi.texinfo
c906108c 13536
8e04817f
AC
13537@node GDB Bugs
13538@chapter Reporting Bugs in @value{GDBN}
13539@cindex bugs in @value{GDBN}
13540@cindex reporting bugs in @value{GDBN}
c906108c 13541
8e04817f 13542Your bug reports play an essential role in making @value{GDBN} reliable.
c906108c 13543
8e04817f
AC
13544Reporting a bug may help you by bringing a solution to your problem, or it
13545may not. But in any case the principal function of a bug report is to help
13546the entire community by making the next version of @value{GDBN} work better. Bug
13547reports are your contribution to the maintenance of @value{GDBN}.
c906108c 13548
8e04817f
AC
13549In order for a bug report to serve its purpose, you must include the
13550information that enables us to fix the bug.
c4555f82
SC
13551
13552@menu
8e04817f
AC
13553* Bug Criteria:: Have you found a bug?
13554* Bug Reporting:: How to report bugs
c4555f82
SC
13555@end menu
13556
8e04817f
AC
13557@node Bug Criteria
13558@section Have you found a bug?
13559@cindex bug criteria
c4555f82 13560
8e04817f 13561If you are not sure whether you have found a bug, here are some guidelines:
c4555f82
SC
13562
13563@itemize @bullet
8e04817f
AC
13564@cindex fatal signal
13565@cindex debugger crash
13566@cindex crash of debugger
c4555f82 13567@item
8e04817f
AC
13568If the debugger gets a fatal signal, for any input whatever, that is a
13569@value{GDBN} bug. Reliable debuggers never crash.
13570
13571@cindex error on valid input
13572@item
13573If @value{GDBN} produces an error message for valid input, that is a
13574bug. (Note that if you're cross debugging, the problem may also be
13575somewhere in the connection to the target.)
c4555f82 13576
8e04817f 13577@cindex invalid input
c4555f82 13578@item
8e04817f
AC
13579If @value{GDBN} does not produce an error message for invalid input,
13580that is a bug. However, you should note that your idea of
13581``invalid input'' might be our idea of ``an extension'' or ``support
13582for traditional practice''.
13583
13584@item
13585If you are an experienced user of debugging tools, your suggestions
13586for improvement of @value{GDBN} are welcome in any case.
c4555f82
SC
13587@end itemize
13588
8e04817f
AC
13589@node Bug Reporting
13590@section How to report bugs
13591@cindex bug reports
13592@cindex @value{GDBN} bugs, reporting
13593
13594A number of companies and individuals offer support for @sc{gnu} products.
13595If you obtained @value{GDBN} from a support organization, we recommend you
13596contact that organization first.
13597
13598You can find contact information for many support companies and
13599individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
13600distribution.
13601@c should add a web page ref...
13602
129188f6
AC
13603In any event, we also recommend that you submit bug reports for
13604@value{GDBN}. The prefered method is to submit them directly using
13605@uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
13606page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
13607be used.
8e04817f
AC
13608
13609@strong{Do not send bug reports to @samp{info-gdb}, or to
13610@samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
13611not want to receive bug reports. Those that do have arranged to receive
13612@samp{bug-gdb}.
13613
13614The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
13615serves as a repeater. The mailing list and the newsgroup carry exactly
13616the same messages. Often people think of posting bug reports to the
13617newsgroup instead of mailing them. This appears to work, but it has one
13618problem which can be crucial: a newsgroup posting often lacks a mail
13619path back to the sender. Thus, if we need to ask for more information,
13620we may be unable to reach you. For this reason, it is better to send
13621bug reports to the mailing list.
c4555f82 13622
8e04817f
AC
13623The fundamental principle of reporting bugs usefully is this:
13624@strong{report all the facts}. If you are not sure whether to state a
13625fact or leave it out, state it!
c4555f82 13626
8e04817f
AC
13627Often people omit facts because they think they know what causes the
13628problem and assume that some details do not matter. Thus, you might
13629assume that the name of the variable you use in an example does not matter.
13630Well, probably it does not, but one cannot be sure. Perhaps the bug is a
13631stray memory reference which happens to fetch from the location where that
13632name is stored in memory; perhaps, if the name were different, the contents
13633of that location would fool the debugger into doing the right thing despite
13634the bug. Play it safe and give a specific, complete example. That is the
13635easiest thing for you to do, and the most helpful.
c4555f82 13636
8e04817f
AC
13637Keep in mind that the purpose of a bug report is to enable us to fix the
13638bug. It may be that the bug has been reported previously, but neither
13639you nor we can know that unless your bug report is complete and
13640self-contained.
c4555f82 13641
8e04817f
AC
13642Sometimes people give a few sketchy facts and ask, ``Does this ring a
13643bell?'' Those bug reports are useless, and we urge everyone to
13644@emph{refuse to respond to them} except to chide the sender to report
13645bugs properly.
13646
13647To enable us to fix the bug, you should include all these things:
c4555f82
SC
13648
13649@itemize @bullet
13650@item
8e04817f
AC
13651The version of @value{GDBN}. @value{GDBN} announces it if you start
13652with no arguments; you can also print it at any time using @code{show
13653version}.
c4555f82 13654
8e04817f
AC
13655Without this, we will not know whether there is any point in looking for
13656the bug in the current version of @value{GDBN}.
c4555f82
SC
13657
13658@item
8e04817f
AC
13659The type of machine you are using, and the operating system name and
13660version number.
c4555f82
SC
13661
13662@item
8e04817f
AC
13663What compiler (and its version) was used to compile @value{GDBN}---e.g.
13664``@value{GCC}--2.8.1''.
c4555f82
SC
13665
13666@item
8e04817f
AC
13667What compiler (and its version) was used to compile the program you are
13668debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
13669C Compiler''. For GCC, you can say @code{gcc --version} to get this
13670information; for other compilers, see the documentation for those
13671compilers.
c4555f82 13672
8e04817f
AC
13673@item
13674The command arguments you gave the compiler to compile your example and
13675observe the bug. For example, did you use @samp{-O}? To guarantee
13676you will not omit something important, list them all. A copy of the
13677Makefile (or the output from make) is sufficient.
c4555f82 13678
8e04817f
AC
13679If we were to try to guess the arguments, we would probably guess wrong
13680and then we might not encounter the bug.
c4555f82 13681
8e04817f
AC
13682@item
13683A complete input script, and all necessary source files, that will
13684reproduce the bug.
c4555f82 13685
8e04817f
AC
13686@item
13687A description of what behavior you observe that you believe is
13688incorrect. For example, ``It gets a fatal signal.''
c4555f82 13689
8e04817f
AC
13690Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
13691will certainly notice it. But if the bug is incorrect output, we might
13692not notice unless it is glaringly wrong. You might as well not give us
13693a chance to make a mistake.
c4555f82 13694
8e04817f
AC
13695Even if the problem you experience is a fatal signal, you should still
13696say so explicitly. Suppose something strange is going on, such as, your
13697copy of @value{GDBN} is out of synch, or you have encountered a bug in
13698the C library on your system. (This has happened!) Your copy might
13699crash and ours would not. If you told us to expect a crash, then when
13700ours fails to crash, we would know that the bug was not happening for
13701us. If you had not told us to expect a crash, then we would not be able
13702to draw any conclusion from our observations.
c4555f82 13703
8e04817f
AC
13704@item
13705If you wish to suggest changes to the @value{GDBN} source, send us context
13706diffs. If you even discuss something in the @value{GDBN} source, refer to
13707it by context, not by line number.
c4555f82 13708
8e04817f
AC
13709The line numbers in our development sources will not match those in your
13710sources. Your line numbers would convey no useful information to us.
c4555f82 13711
8e04817f 13712@end itemize
c4555f82 13713
8e04817f 13714Here are some things that are not necessary:
c4555f82 13715
8e04817f
AC
13716@itemize @bullet
13717@item
13718A description of the envelope of the bug.
c4555f82 13719
8e04817f
AC
13720Often people who encounter a bug spend a lot of time investigating
13721which changes to the input file will make the bug go away and which
13722changes will not affect it.
c4555f82 13723
8e04817f
AC
13724This is often time consuming and not very useful, because the way we
13725will find the bug is by running a single example under the debugger
13726with breakpoints, not by pure deduction from a series of examples.
13727We recommend that you save your time for something else.
c4555f82 13728
8e04817f
AC
13729Of course, if you can find a simpler example to report @emph{instead}
13730of the original one, that is a convenience for us. Errors in the
13731output will be easier to spot, running under the debugger will take
13732less time, and so on.
c4555f82 13733
8e04817f
AC
13734However, simplification is not vital; if you do not want to do this,
13735report the bug anyway and send us the entire test case you used.
c4555f82 13736
8e04817f
AC
13737@item
13738A patch for the bug.
c4555f82 13739
8e04817f
AC
13740A patch for the bug does help us if it is a good one. But do not omit
13741the necessary information, such as the test case, on the assumption that
13742a patch is all we need. We might see problems with your patch and decide
13743to fix the problem another way, or we might not understand it at all.
c4555f82 13744
8e04817f
AC
13745Sometimes with a program as complicated as @value{GDBN} it is very hard to
13746construct an example that will make the program follow a certain path
13747through the code. If you do not send us the example, we will not be able
13748to construct one, so we will not be able to verify that the bug is fixed.
c4555f82 13749
8e04817f
AC
13750And if we cannot understand what bug you are trying to fix, or why your
13751patch should be an improvement, we will not install it. A test case will
13752help us to understand.
c4555f82 13753
8e04817f
AC
13754@item
13755A guess about what the bug is or what it depends on.
c4555f82 13756
8e04817f
AC
13757Such guesses are usually wrong. Even we cannot guess right about such
13758things without first using the debugger to find the facts.
13759@end itemize
c4555f82 13760
8e04817f
AC
13761@c The readline documentation is distributed with the readline code
13762@c and consists of the two following files:
13763@c rluser.texinfo
13764@c inc-hist.texinfo
13765@c Use -I with makeinfo to point to the appropriate directory,
13766@c environment var TEXINPUTS with TeX.
13767@include rluser.texinfo
13768@include inc-hist.texinfo
c4555f82 13769
c4555f82 13770
8e04817f
AC
13771@node Formatting Documentation
13772@appendix Formatting Documentation
c4555f82 13773
8e04817f
AC
13774@cindex @value{GDBN} reference card
13775@cindex reference card
13776The @value{GDBN} 4 release includes an already-formatted reference card, ready
13777for printing with PostScript or Ghostscript, in the @file{gdb}
13778subdirectory of the main source directory@footnote{In
13779@file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
13780release.}. If you can use PostScript or Ghostscript with your printer,
13781you can print the reference card immediately with @file{refcard.ps}.
c4555f82 13782
8e04817f
AC
13783The release also includes the source for the reference card. You
13784can format it, using @TeX{}, by typing:
c4555f82 13785
474c8240 13786@smallexample
8e04817f 13787make refcard.dvi
474c8240 13788@end smallexample
c4555f82 13789
8e04817f
AC
13790The @value{GDBN} reference card is designed to print in @dfn{landscape}
13791mode on US ``letter'' size paper;
13792that is, on a sheet 11 inches wide by 8.5 inches
13793high. You will need to specify this form of printing as an option to
13794your @sc{dvi} output program.
c4555f82 13795
8e04817f 13796@cindex documentation
c4555f82 13797
8e04817f
AC
13798All the documentation for @value{GDBN} comes as part of the machine-readable
13799distribution. The documentation is written in Texinfo format, which is
13800a documentation system that uses a single source file to produce both
13801on-line information and a printed manual. You can use one of the Info
13802formatting commands to create the on-line version of the documentation
13803and @TeX{} (or @code{texi2roff}) to typeset the printed version.
c4555f82 13804
8e04817f
AC
13805@value{GDBN} includes an already formatted copy of the on-line Info
13806version of this manual in the @file{gdb} subdirectory. The main Info
13807file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
13808subordinate files matching @samp{gdb.info*} in the same directory. If
13809necessary, you can print out these files, or read them with any editor;
13810but they are easier to read using the @code{info} subsystem in @sc{gnu}
13811Emacs or the standalone @code{info} program, available as part of the
13812@sc{gnu} Texinfo distribution.
c4555f82 13813
8e04817f
AC
13814If you want to format these Info files yourself, you need one of the
13815Info formatting programs, such as @code{texinfo-format-buffer} or
13816@code{makeinfo}.
c4555f82 13817
8e04817f
AC
13818If you have @code{makeinfo} installed, and are in the top level
13819@value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
13820version @value{GDBVN}), you can make the Info file by typing:
c4555f82 13821
474c8240 13822@smallexample
8e04817f
AC
13823cd gdb
13824make gdb.info
474c8240 13825@end smallexample
c4555f82 13826
8e04817f
AC
13827If you want to typeset and print copies of this manual, you need @TeX{},
13828a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
13829Texinfo definitions file.
c4555f82 13830
8e04817f
AC
13831@TeX{} is a typesetting program; it does not print files directly, but
13832produces output files called @sc{dvi} files. To print a typeset
13833document, you need a program to print @sc{dvi} files. If your system
13834has @TeX{} installed, chances are it has such a program. The precise
13835command to use depends on your system; @kbd{lpr -d} is common; another
13836(for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
13837require a file name without any extension or a @samp{.dvi} extension.
c4555f82 13838
8e04817f
AC
13839@TeX{} also requires a macro definitions file called
13840@file{texinfo.tex}. This file tells @TeX{} how to typeset a document
13841written in Texinfo format. On its own, @TeX{} cannot either read or
13842typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
13843and is located in the @file{gdb-@var{version-number}/texinfo}
13844directory.
c4555f82 13845
8e04817f
AC
13846If you have @TeX{} and a @sc{dvi} printer program installed, you can
13847typeset and print this manual. First switch to the the @file{gdb}
13848subdirectory of the main source directory (for example, to
13849@file{gdb-@value{GDBVN}/gdb}) and type:
c4555f82 13850
474c8240 13851@smallexample
8e04817f 13852make gdb.dvi
474c8240 13853@end smallexample
c4555f82 13854
8e04817f 13855Then give @file{gdb.dvi} to your @sc{dvi} printing program.
c4555f82 13856
8e04817f
AC
13857@node Installing GDB
13858@appendix Installing @value{GDBN}
13859@cindex configuring @value{GDBN}
13860@cindex installation
c4555f82 13861
8e04817f
AC
13862@value{GDBN} comes with a @code{configure} script that automates the process
13863of preparing @value{GDBN} for installation; you can then use @code{make} to
13864build the @code{gdb} program.
13865@iftex
13866@c irrelevant in info file; it's as current as the code it lives with.
13867@footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
13868look at the @file{README} file in the sources; we may have improved the
13869installation procedures since publishing this manual.}
13870@end iftex
c4555f82 13871
8e04817f
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13872The @value{GDBN} distribution includes all the source code you need for
13873@value{GDBN} in a single directory, whose name is usually composed by
13874appending the version number to @samp{gdb}.
c4555f82 13875
8e04817f
AC
13876For example, the @value{GDBN} version @value{GDBVN} distribution is in the
13877@file{gdb-@value{GDBVN}} directory. That directory contains:
c4555f82 13878
8e04817f
AC
13879@table @code
13880@item gdb-@value{GDBVN}/configure @r{(and supporting files)}
13881script for configuring @value{GDBN} and all its supporting libraries
c4555f82 13882
8e04817f
AC
13883@item gdb-@value{GDBVN}/gdb
13884the source specific to @value{GDBN} itself
c4555f82 13885
8e04817f
AC
13886@item gdb-@value{GDBVN}/bfd
13887source for the Binary File Descriptor library
c906108c 13888
8e04817f
AC
13889@item gdb-@value{GDBVN}/include
13890@sc{gnu} include files
c906108c 13891
8e04817f
AC
13892@item gdb-@value{GDBVN}/libiberty
13893source for the @samp{-liberty} free software library
c906108c 13894
8e04817f
AC
13895@item gdb-@value{GDBVN}/opcodes
13896source for the library of opcode tables and disassemblers
c906108c 13897
8e04817f
AC
13898@item gdb-@value{GDBVN}/readline
13899source for the @sc{gnu} command-line interface
c906108c 13900
8e04817f
AC
13901@item gdb-@value{GDBVN}/glob
13902source for the @sc{gnu} filename pattern-matching subroutine
c906108c 13903
8e04817f
AC
13904@item gdb-@value{GDBVN}/mmalloc
13905source for the @sc{gnu} memory-mapped malloc package
13906@end table
c906108c 13907
8e04817f
AC
13908The simplest way to configure and build @value{GDBN} is to run @code{configure}
13909from the @file{gdb-@var{version-number}} source directory, which in
13910this example is the @file{gdb-@value{GDBVN}} directory.
c906108c 13911
8e04817f
AC
13912First switch to the @file{gdb-@var{version-number}} source directory
13913if you are not already in it; then run @code{configure}. Pass the
13914identifier for the platform on which @value{GDBN} will run as an
13915argument.
c906108c 13916
8e04817f 13917For example:
c906108c 13918
474c8240 13919@smallexample
8e04817f
AC
13920cd gdb-@value{GDBVN}
13921./configure @var{host}
13922make
474c8240 13923@end smallexample
c906108c 13924
8e04817f
AC
13925@noindent
13926where @var{host} is an identifier such as @samp{sun4} or
13927@samp{decstation}, that identifies the platform where @value{GDBN} will run.
13928(You can often leave off @var{host}; @code{configure} tries to guess the
13929correct value by examining your system.)
c906108c 13930
8e04817f
AC
13931Running @samp{configure @var{host}} and then running @code{make} builds the
13932@file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
13933libraries, then @code{gdb} itself. The configured source files, and the
13934binaries, are left in the corresponding source directories.
c906108c 13935
8e04817f
AC
13936@need 750
13937@code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
13938system does not recognize this automatically when you run a different
13939shell, you may need to run @code{sh} on it explicitly:
c906108c 13940
474c8240 13941@smallexample
8e04817f 13942sh configure @var{host}
474c8240 13943@end smallexample
c906108c 13944
8e04817f
AC
13945If you run @code{configure} from a directory that contains source
13946directories for multiple libraries or programs, such as the
13947@file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
13948creates configuration files for every directory level underneath (unless
13949you tell it not to, with the @samp{--norecursion} option).
13950
13951You can run the @code{configure} script from any of the
13952subordinate directories in the @value{GDBN} distribution if you only want to
13953configure that subdirectory, but be sure to specify a path to it.
c906108c 13954
8e04817f
AC
13955For example, with version @value{GDBVN}, type the following to configure only
13956the @code{bfd} subdirectory:
c906108c 13957
474c8240 13958@smallexample
8e04817f
AC
13959@group
13960cd gdb-@value{GDBVN}/bfd
13961../configure @var{host}
13962@end group
474c8240 13963@end smallexample
c906108c 13964
8e04817f
AC
13965You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
13966However, you should make sure that the shell on your path (named by
13967the @samp{SHELL} environment variable) is publicly readable. Remember
13968that @value{GDBN} uses the shell to start your program---some systems refuse to
13969let @value{GDBN} debug child processes whose programs are not readable.
c906108c 13970
8e04817f
AC
13971@menu
13972* Separate Objdir:: Compiling @value{GDBN} in another directory
13973* Config Names:: Specifying names for hosts and targets
13974* Configure Options:: Summary of options for configure
13975@end menu
c906108c 13976
8e04817f
AC
13977@node Separate Objdir
13978@section Compiling @value{GDBN} in another directory
c906108c 13979
8e04817f
AC
13980If you want to run @value{GDBN} versions for several host or target machines,
13981you need a different @code{gdb} compiled for each combination of
13982host and target. @code{configure} is designed to make this easy by
13983allowing you to generate each configuration in a separate subdirectory,
13984rather than in the source directory. If your @code{make} program
13985handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
13986@code{make} in each of these directories builds the @code{gdb}
13987program specified there.
c906108c 13988
8e04817f
AC
13989To build @code{gdb} in a separate directory, run @code{configure}
13990with the @samp{--srcdir} option to specify where to find the source.
13991(You also need to specify a path to find @code{configure}
13992itself from your working directory. If the path to @code{configure}
13993would be the same as the argument to @samp{--srcdir}, you can leave out
13994the @samp{--srcdir} option; it is assumed.)
c906108c 13995
8e04817f
AC
13996For example, with version @value{GDBVN}, you can build @value{GDBN} in a
13997separate directory for a Sun 4 like this:
c906108c 13998
474c8240 13999@smallexample
8e04817f
AC
14000@group
14001cd gdb-@value{GDBVN}
14002mkdir ../gdb-sun4
14003cd ../gdb-sun4
14004../gdb-@value{GDBVN}/configure sun4
14005make
14006@end group
474c8240 14007@end smallexample
c906108c 14008
8e04817f
AC
14009When @code{configure} builds a configuration using a remote source
14010directory, it creates a tree for the binaries with the same structure
14011(and using the same names) as the tree under the source directory. In
14012the example, you'd find the Sun 4 library @file{libiberty.a} in the
14013directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
14014@file{gdb-sun4/gdb}.
c906108c 14015
8e04817f
AC
14016One popular reason to build several @value{GDBN} configurations in separate
14017directories is to configure @value{GDBN} for cross-compiling (where
14018@value{GDBN} runs on one machine---the @dfn{host}---while debugging
14019programs that run on another machine---the @dfn{target}).
14020You specify a cross-debugging target by
14021giving the @samp{--target=@var{target}} option to @code{configure}.
c906108c 14022
8e04817f
AC
14023When you run @code{make} to build a program or library, you must run
14024it in a configured directory---whatever directory you were in when you
14025called @code{configure} (or one of its subdirectories).
c906108c 14026
8e04817f
AC
14027The @code{Makefile} that @code{configure} generates in each source
14028directory also runs recursively. If you type @code{make} in a source
14029directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
14030directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
14031will build all the required libraries, and then build GDB.
c906108c 14032
8e04817f
AC
14033When you have multiple hosts or targets configured in separate
14034directories, you can run @code{make} on them in parallel (for example,
14035if they are NFS-mounted on each of the hosts); they will not interfere
14036with each other.
c906108c 14037
8e04817f
AC
14038@node Config Names
14039@section Specifying names for hosts and targets
c906108c 14040
8e04817f
AC
14041The specifications used for hosts and targets in the @code{configure}
14042script are based on a three-part naming scheme, but some short predefined
14043aliases are also supported. The full naming scheme encodes three pieces
14044of information in the following pattern:
c906108c 14045
474c8240 14046@smallexample
8e04817f 14047@var{architecture}-@var{vendor}-@var{os}
474c8240 14048@end smallexample
c906108c 14049
8e04817f
AC
14050For example, you can use the alias @code{sun4} as a @var{host} argument,
14051or as the value for @var{target} in a @code{--target=@var{target}}
14052option. The equivalent full name is @samp{sparc-sun-sunos4}.
c906108c 14053
8e04817f
AC
14054The @code{configure} script accompanying @value{GDBN} does not provide
14055any query facility to list all supported host and target names or
14056aliases. @code{configure} calls the Bourne shell script
14057@code{config.sub} to map abbreviations to full names; you can read the
14058script, if you wish, or you can use it to test your guesses on
14059abbreviations---for example:
c906108c 14060
8e04817f
AC
14061@smallexample
14062% sh config.sub i386-linux
14063i386-pc-linux-gnu
14064% sh config.sub alpha-linux
14065alpha-unknown-linux-gnu
14066% sh config.sub hp9k700
14067hppa1.1-hp-hpux
14068% sh config.sub sun4
14069sparc-sun-sunos4.1.1
14070% sh config.sub sun3
14071m68k-sun-sunos4.1.1
14072% sh config.sub i986v
14073Invalid configuration `i986v': machine `i986v' not recognized
14074@end smallexample
c906108c 14075
8e04817f
AC
14076@noindent
14077@code{config.sub} is also distributed in the @value{GDBN} source
14078directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
d700128c 14079
8e04817f
AC
14080@node Configure Options
14081@section @code{configure} options
c906108c 14082
8e04817f
AC
14083Here is a summary of the @code{configure} options and arguments that
14084are most often useful for building @value{GDBN}. @code{configure} also has
14085several other options not listed here. @inforef{What Configure
14086Does,,configure.info}, for a full explanation of @code{configure}.
c906108c 14087
474c8240 14088@smallexample
8e04817f
AC
14089configure @r{[}--help@r{]}
14090 @r{[}--prefix=@var{dir}@r{]}
14091 @r{[}--exec-prefix=@var{dir}@r{]}
14092 @r{[}--srcdir=@var{dirname}@r{]}
14093 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
14094 @r{[}--target=@var{target}@r{]}
14095 @var{host}
474c8240 14096@end smallexample
c906108c 14097
8e04817f
AC
14098@noindent
14099You may introduce options with a single @samp{-} rather than
14100@samp{--} if you prefer; but you may abbreviate option names if you use
14101@samp{--}.
c906108c 14102
8e04817f
AC
14103@table @code
14104@item --help
14105Display a quick summary of how to invoke @code{configure}.
c906108c 14106
8e04817f
AC
14107@item --prefix=@var{dir}
14108Configure the source to install programs and files under directory
14109@file{@var{dir}}.
c906108c 14110
8e04817f
AC
14111@item --exec-prefix=@var{dir}
14112Configure the source to install programs under directory
14113@file{@var{dir}}.
c906108c 14114
8e04817f
AC
14115@c avoid splitting the warning from the explanation:
14116@need 2000
14117@item --srcdir=@var{dirname}
14118@strong{Warning: using this option requires @sc{gnu} @code{make}, or another
14119@code{make} that implements the @code{VPATH} feature.}@*
14120Use this option to make configurations in directories separate from the
14121@value{GDBN} source directories. Among other things, you can use this to
14122build (or maintain) several configurations simultaneously, in separate
14123directories. @code{configure} writes configuration specific files in
14124the current directory, but arranges for them to use the source in the
14125directory @var{dirname}. @code{configure} creates directories under
14126the working directory in parallel to the source directories below
14127@var{dirname}.
c906108c 14128
8e04817f
AC
14129@item --norecursion
14130Configure only the directory level where @code{configure} is executed; do not
14131propagate configuration to subdirectories.
c906108c 14132
8e04817f
AC
14133@item --target=@var{target}
14134Configure @value{GDBN} for cross-debugging programs running on the specified
14135@var{target}. Without this option, @value{GDBN} is configured to debug
14136programs that run on the same machine (@var{host}) as @value{GDBN} itself.
c906108c 14137
8e04817f 14138There is no convenient way to generate a list of all available targets.
c906108c 14139
8e04817f
AC
14140@item @var{host} @dots{}
14141Configure @value{GDBN} to run on the specified @var{host}.
c906108c 14142
8e04817f
AC
14143There is no convenient way to generate a list of all available hosts.
14144@end table
c906108c 14145
8e04817f
AC
14146There are many other options available as well, but they are generally
14147needed for special purposes only.
c906108c 14148
8e04817f
AC
14149@node Maintenance Commands
14150@appendix Maintenance Commands
14151@cindex maintenance commands
14152@cindex internal commands
c906108c 14153
8e04817f
AC
14154In addition to commands intended for @value{GDBN} users, @value{GDBN}
14155includes a number of commands intended for @value{GDBN} developers.
14156These commands are provided here for reference.
c906108c 14157
8e04817f
AC
14158@table @code
14159@kindex maint info breakpoints
14160@item @anchor{maint info breakpoints}maint info breakpoints
14161Using the same format as @samp{info breakpoints}, display both the
14162breakpoints you've set explicitly, and those @value{GDBN} is using for
14163internal purposes. Internal breakpoints are shown with negative
14164breakpoint numbers. The type column identifies what kind of breakpoint
14165is shown:
c906108c 14166
8e04817f
AC
14167@table @code
14168@item breakpoint
14169Normal, explicitly set breakpoint.
c906108c 14170
8e04817f
AC
14171@item watchpoint
14172Normal, explicitly set watchpoint.
c906108c 14173
8e04817f
AC
14174@item longjmp
14175Internal breakpoint, used to handle correctly stepping through
14176@code{longjmp} calls.
c906108c 14177
8e04817f
AC
14178@item longjmp resume
14179Internal breakpoint at the target of a @code{longjmp}.
c906108c 14180
8e04817f
AC
14181@item until
14182Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
c906108c 14183
8e04817f
AC
14184@item finish
14185Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
c906108c 14186
8e04817f
AC
14187@item shlib events
14188Shared library events.
c906108c 14189
8e04817f 14190@end table
c906108c 14191
8e04817f 14192@end table
c906108c 14193
c906108c 14194
e0ce93ac 14195@node Remote Protocol
8e04817f 14196@appendix @value{GDBN} Remote Serial Protocol
c906108c 14197
8e04817f
AC
14198There may be occasions when you need to know something about the
14199protocol---for example, if there is only one serial port to your target
14200machine, you might want your program to do something special if it
14201recognizes a packet meant for @value{GDBN}.
c906108c 14202
8e04817f
AC
14203In the examples below, @samp{<-} and @samp{->} are used to indicate
14204transmitted and received data respectfully.
c906108c 14205
8e04817f
AC
14206@cindex protocol, @value{GDBN} remote serial
14207@cindex serial protocol, @value{GDBN} remote
14208@cindex remote serial protocol
14209All @value{GDBN} commands and responses (other than acknowledgments) are
14210sent as a @var{packet}. A @var{packet} is introduced with the character
14211@samp{$}, the actual @var{packet-data}, and the terminating character
14212@samp{#} followed by a two-digit @var{checksum}:
c906108c 14213
474c8240 14214@smallexample
8e04817f 14215@code{$}@var{packet-data}@code{#}@var{checksum}
474c8240 14216@end smallexample
8e04817f 14217@noindent
c906108c 14218
8e04817f
AC
14219@cindex checksum, for @value{GDBN} remote
14220@noindent
14221The two-digit @var{checksum} is computed as the modulo 256 sum of all
14222characters between the leading @samp{$} and the trailing @samp{#} (an
14223eight bit unsigned checksum).
c906108c 14224
8e04817f
AC
14225Implementors should note that prior to @value{GDBN} 5.0 the protocol
14226specification also included an optional two-digit @var{sequence-id}:
c906108c 14227
474c8240 14228@smallexample
8e04817f 14229@code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
474c8240 14230@end smallexample
c906108c 14231
8e04817f
AC
14232@cindex sequence-id, for @value{GDBN} remote
14233@noindent
14234That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
14235has never output @var{sequence-id}s. Stubs that handle packets added
14236since @value{GDBN} 5.0 must not accept @var{sequence-id}.
c906108c 14237
8e04817f
AC
14238@cindex acknowledgment, for @value{GDBN} remote
14239When either the host or the target machine receives a packet, the first
14240response expected is an acknowledgment: either @samp{+} (to indicate
14241the package was received correctly) or @samp{-} (to request
14242retransmission):
c906108c 14243
474c8240 14244@smallexample
8e04817f
AC
14245<- @code{$}@var{packet-data}@code{#}@var{checksum}
14246-> @code{+}
474c8240 14247@end smallexample
8e04817f 14248@noindent
53a5351d 14249
8e04817f
AC
14250The host (@value{GDBN}) sends @var{command}s, and the target (the
14251debugging stub incorporated in your program) sends a @var{response}. In
14252the case of step and continue @var{command}s, the response is only sent
14253when the operation has completed (the target has again stopped).
c906108c 14254
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AC
14255@var{packet-data} consists of a sequence of characters with the
14256exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
14257exceptions).
c906108c 14258
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AC
14259Fields within the packet should be separated using @samp{,} @samp{;} or
14260@samp{:}. Except where otherwise noted all numbers are represented in
14261HEX with leading zeros suppressed.
c906108c 14262
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14263Implementors should note that prior to @value{GDBN} 5.0, the character
14264@samp{:} could not appear as the third character in a packet (as it
14265would potentially conflict with the @var{sequence-id}).
c906108c 14266
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AC
14267Response @var{data} can be run-length encoded to save space. A @samp{*}
14268means that the next character is an @sc{ascii} encoding giving a repeat count
14269which stands for that many repetitions of the character preceding the
14270@samp{*}. The encoding is @code{n+29}, yielding a printable character
14271where @code{n >=3} (which is where rle starts to win). The printable
14272characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
14273value greater than 126 should not be used.
c906108c 14274
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AC
14275Some remote systems have used a different run-length encoding mechanism
14276loosely refered to as the cisco encoding. Following the @samp{*}
14277character are two hex digits that indicate the size of the packet.
c906108c 14278
8e04817f 14279So:
474c8240 14280@smallexample
8e04817f 14281"@code{0* }"
474c8240 14282@end smallexample
8e04817f
AC
14283@noindent
14284means the same as "0000".
c906108c 14285
8e04817f
AC
14286The error response returned for some packets includes a two character
14287error number. That number is not well defined.
c906108c 14288
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14289For any @var{command} not supported by the stub, an empty response
14290(@samp{$#00}) should be returned. That way it is possible to extend the
14291protocol. A newer @value{GDBN} can tell if a packet is supported based
14292on that response.
c906108c 14293
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AC
14294A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
14295@samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
14296optional.
c906108c 14297
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14298Below is a complete list of all currently defined @var{command}s and
14299their corresponding response @var{data}:
14300@page
14301@multitable @columnfractions .30 .30 .40
14302@item Packet
14303@tab Request
14304@tab Description
c906108c 14305
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AC
14306@item extended mode
14307@tab @code{!}
14308@tab
14309Enable extended mode. In extended mode, the remote server is made
14310persistent. The @samp{R} packet is used to restart the program being
14311debugged.
c906108c 14312@item
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AC
14313@tab reply @samp{OK}
14314@tab
14315The remote target both supports and has enabled extended mode.
c906108c 14316
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14317@item last signal
14318@tab @code{?}
14319@tab
14320Indicate the reason the target halted. The reply is the same as for step
14321and continue.
14322@item
14323@tab reply
14324@tab see below
c906108c
SS
14325
14326
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14327@item reserved
14328@tab @code{a}
14329@tab Reserved for future use
c906108c 14330
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14331@item set program arguments @strong{(reserved)}
14332@tab @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,...}
14333@tab
14334@item
14335@tab
14336@tab
14337Initialized @samp{argv[]} array passed into program. @var{arglen}
14338specifies the number of bytes in the hex encoded byte stream @var{arg}.
14339See @file{gdbserver} for more details.
14340@item
14341@tab reply @code{OK}
14342@item
14343@tab reply @code{E}@var{NN}
c906108c 14344
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14345@item set baud @strong{(deprecated)}
14346@tab @code{b}@var{baud}
14347@tab
14348Change the serial line speed to @var{baud}. JTC: @emph{When does the
14349transport layer state change? When it's received, or after the ACK is
14350transmitted. In either case, there are problems if the command or the
14351acknowledgment packet is dropped.} Stan: @emph{If people really wanted
14352to add something like this, and get it working for the first time, they
14353ought to modify ser-unix.c to send some kind of out-of-band message to a
14354specially-setup stub and have the switch happen "in between" packets, so
14355that from remote protocol's point of view, nothing actually
14356happened.}
c906108c 14357
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14358@item set breakpoint @strong{(deprecated)}
14359@tab @code{B}@var{addr},@var{mode}
14360@tab
14361Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
14362breakpoint at @var{addr}. @emph{This has been replaced by the @samp{Z} and
14363@samp{z} packets.}
c906108c 14364
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14365@item continue
14366@tab @code{c}@var{addr}
14367@tab
14368@var{addr} is address to resume. If @var{addr} is omitted, resume at
14369current address.
14370@item
14371@tab reply
14372@tab see below
c906108c 14373
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AC
14374@item continue with signal
14375@tab @code{C}@var{sig}@code{;}@var{addr}
14376@tab
14377Continue with signal @var{sig} (hex signal number). If
14378@code{;}@var{addr} is omitted, resume at same address.
14379@item
14380@tab reply
14381@tab see below
c906108c 14382
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AC
14383@item toggle debug @strong{(deprecated)}
14384@tab @code{d}
14385@tab
14386toggle debug flag.
c906108c 14387
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14388@item detach
14389@tab @code{D}
14390@tab
14391Detach @value{GDBN} from the remote system. Sent to the remote target before
14392@value{GDBN} disconnects.
14393@item
14394@tab reply @emph{no response}
14395@tab
14396@value{GDBN} does not check for any response after sending this packet.
c906108c 14397
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14398@item reserved
14399@tab @code{e}
14400@tab Reserved for future use
c906108c 14401
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14402@item reserved
14403@tab @code{E}
14404@tab Reserved for future use
c906108c 14405
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AC
14406@item reserved
14407@tab @code{f}
14408@tab Reserved for future use
c906108c 14409
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AC
14410@item reserved
14411@tab @code{F}
14412@tab Reserved for future use
c906108c 14413
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14414@item read registers
14415@tab @code{g}
14416@tab Read general registers.
14417@item
14418@tab reply @var{XX...}
14419@tab
14420Each byte of register data is described by two hex digits. The bytes
14421with the register are transmitted in target byte order. The size of
14422each register and their position within the @samp{g} @var{packet} are
14423determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE} and
14424@var{REGISTER_NAME} macros. The specification of several standard
14425@code{g} packets is specified below.
14426@item
14427@tab @code{E}@var{NN}
14428@tab for an error.
c906108c 14429
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14430@item write regs
14431@tab @code{G}@var{XX...}
14432@tab
14433See @samp{g} for a description of the @var{XX...} data.
14434@item
14435@tab reply @code{OK}
14436@tab for success
14437@item
14438@tab reply @code{E}@var{NN}
14439@tab for an error
c906108c 14440
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14441@item reserved
14442@tab @code{h}
14443@tab Reserved for future use
c906108c 14444
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14445@item set thread
14446@tab @code{H}@var{c}@var{t...}
14447@tab
14448Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
14449@samp{G}, et.al.). @var{c} = @samp{c} for thread used in step and
14450continue; @var{t...} can be -1 for all threads. @var{c} = @samp{g} for
14451thread used in other operations. If zero, pick a thread, any thread.
14452@item
14453@tab reply @code{OK}
14454@tab for success
14455@item
14456@tab reply @code{E}@var{NN}
14457@tab for an error
c906108c 14458
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14459@c FIXME: JTC:
14460@c 'H': How restrictive (or permissive) is the thread model. If a
14461@c thread is selected and stopped, are other threads allowed
14462@c to continue to execute? As I mentioned above, I think the
14463@c semantics of each command when a thread is selected must be
14464@c described. For example:
14465@c
14466@c 'g': If the stub supports threads and a specific thread is
14467@c selected, returns the register block from that thread;
14468@c otherwise returns current registers.
14469@c
14470@c 'G' If the stub supports threads and a specific thread is
14471@c selected, sets the registers of the register block of
14472@c that thread; otherwise sets current registers.
c906108c 14473
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AC
14474@item cycle step @strong{(draft)}
14475@tab @code{i}@var{addr}@code{,}@var{nnn}
14476@tab
14477Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
14478present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
14479step starting at that address.
c906108c 14480
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AC
14481@item signal then cycle step @strong{(reserved)}
14482@tab @code{I}
14483@tab
14484See @samp{i} and @samp{S} for likely syntax and semantics.
c906108c 14485
8e04817f
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14486@item reserved
14487@tab @code{j}
14488@tab Reserved for future use
c906108c 14489
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AC
14490@item reserved
14491@tab @code{J}
14492@tab Reserved for future use
c906108c 14493
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AC
14494@item kill request
14495@tab @code{k}
14496@tab
ac282366 14497FIXME: @emph{There is no description of how to operate when a specific
6ca652b0 14498thread context has been selected (i.e.@: does 'k' kill only that thread?)}.
c906108c 14499
8e04817f
AC
14500@item reserved
14501@tab @code{l}
14502@tab Reserved for future use
c906108c 14503
8e04817f
AC
14504@item reserved
14505@tab @code{L}
14506@tab Reserved for future use
c906108c 14507
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AC
14508@item read memory
14509@tab @code{m}@var{addr}@code{,}@var{length}
14510@tab
14511Read @var{length} bytes of memory starting at address @var{addr}.
14512Neither @value{GDBN} nor the stub assume that sized memory transfers are assumed
14513using word alligned accesses. FIXME: @emph{A word aligned memory
14514transfer mechanism is needed.}
14515@item
14516@tab reply @var{XX...}
14517@tab
14518@var{XX...} is mem contents. Can be fewer bytes than requested if able
14519to read only part of the data. Neither @value{GDBN} nor the stub assume that
14520sized memory transfers are assumed using word alligned accesses. FIXME:
14521@emph{A word aligned memory transfer mechanism is needed.}
14522@item
14523@tab reply @code{E}@var{NN}
14524@tab @var{NN} is errno
c906108c 14525
8e04817f
AC
14526@item write mem
14527@tab @code{M}@var{addr},@var{length}@code{:}@var{XX...}
14528@tab
14529Write @var{length} bytes of memory starting at address @var{addr}.
14530@var{XX...} is the data.
14531@item
14532@tab reply @code{OK}
14533@tab for success
14534@item
14535@tab reply @code{E}@var{NN}
14536@tab
14537for an error (this includes the case where only part of the data was
14538written).
c906108c 14539
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AC
14540@item reserved
14541@tab @code{n}
14542@tab Reserved for future use
c906108c 14543
8e04817f
AC
14544@item reserved
14545@tab @code{N}
14546@tab Reserved for future use
c906108c 14547
8e04817f
AC
14548@item reserved
14549@tab @code{o}
14550@tab Reserved for future use
c906108c 14551
8e04817f
AC
14552@item reserved
14553@tab @code{O}
14554@tab Reserved for future use
c906108c 14555
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AC
14556@item read reg @strong{(reserved)}
14557@tab @code{p}@var{n...}
14558@tab
14559See write register.
14560@item
14561@tab return @var{r....}
14562@tab The hex encoded value of the register in target byte order.
c906108c 14563
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AC
14564@item write reg
14565@tab @code{P}@var{n...}@code{=}@var{r...}
14566@tab
14567Write register @var{n...} with value @var{r...}, which contains two hex
14568digits for each byte in the register (target byte order).
14569@item
14570@tab reply @code{OK}
14571@tab for success
14572@item
14573@tab reply @code{E}@var{NN}
14574@tab for an error
c906108c 14575
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AC
14576@item general query
14577@tab @code{q}@var{query}
14578@tab
14579Request info about @var{query}. In general @value{GDBN} queries
14580have a leading upper case letter. Custom vendor queries should use a
14581company prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may
14582optionally be followed by a @samp{,} or @samp{;} separated list. Stubs
14583must ensure that they match the full @var{query} name.
14584@item
14585@tab reply @code{XX...}
14586@tab Hex encoded data from query. The reply can not be empty.
14587@item
14588@tab reply @code{E}@var{NN}
14589@tab error reply
14590@item
14591@tab reply @samp{}
14592@tab Indicating an unrecognized @var{query}.
c906108c 14593
8e04817f
AC
14594@item general set
14595@tab @code{Q}@var{var}@code{=}@var{val}
14596@tab
14597Set value of @var{var} to @var{val}. See @samp{q} for a discussing of
14598naming conventions.
c906108c 14599
8e04817f
AC
14600@item reset @strong{(deprecated)}
14601@tab @code{r}
14602@tab
14603Reset the entire system.
c906108c 14604
8e04817f
AC
14605@item remote restart
14606@tab @code{R}@var{XX}
14607@tab
14608Restart the program being debugged. @var{XX}, while needed, is ignored.
14609This packet is only available in extended mode.
14610@item
14611@tab
14612no reply
14613@tab
14614The @samp{R} packet has no reply.
c906108c 14615
8e04817f
AC
14616@item step
14617@tab @code{s}@var{addr}
14618@tab
14619@var{addr} is address to resume. If @var{addr} is omitted, resume at
14620same address.
14621@item
14622@tab reply
14623@tab see below
c906108c 14624
8e04817f
AC
14625@item step with signal
14626@tab @code{S}@var{sig}@code{;}@var{addr}
14627@tab
14628Like @samp{C} but step not continue.
14629@item
14630@tab reply
14631@tab see below
c906108c 14632
8e04817f
AC
14633@item search
14634@tab @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM}
14635@tab
14636Search backwards starting at address @var{addr} for a match with pattern
14637@var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4
14638bytes. @var{addr} must be at least 3 digits.
c906108c 14639
8e04817f
AC
14640@item thread alive
14641@tab @code{T}@var{XX}
14642@tab Find out if the thread XX is alive.
14643@item
14644@tab reply @code{OK}
14645@tab thread is still alive
14646@item
14647@tab reply @code{E}@var{NN}
14648@tab thread is dead
c906108c 14649
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AC
14650@item reserved
14651@tab @code{u}
14652@tab Reserved for future use
c906108c 14653
8e04817f
AC
14654@item reserved
14655@tab @code{U}
14656@tab Reserved for future use
c906108c 14657
8e04817f
AC
14658@item reserved
14659@tab @code{v}
14660@tab Reserved for future use
c906108c 14661
8e04817f
AC
14662@item reserved
14663@tab @code{V}
14664@tab Reserved for future use
c906108c 14665
8e04817f
AC
14666@item reserved
14667@tab @code{w}
14668@tab Reserved for future use
c906108c 14669
8e04817f
AC
14670@item reserved
14671@tab @code{W}
14672@tab Reserved for future use
c906108c 14673
8e04817f
AC
14674@item reserved
14675@tab @code{x}
14676@tab Reserved for future use
c906108c 14677
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AC
14678@item write mem (binary)
14679@tab @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX...}
14680@tab
14681@var{addr} is address, @var{length} is number of bytes, @var{XX...} is
14682binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
14683escaped using @code{0x7d}.
14684@item
14685@tab reply @code{OK}
14686@tab for success
14687@item
14688@tab reply @code{E}@var{NN}
14689@tab for an error
c906108c 14690
8e04817f
AC
14691@item reserved
14692@tab @code{y}
14693@tab Reserved for future use
c906108c 14694
8e04817f
AC
14695@item reserved
14696@tab @code{Y}
14697@tab Reserved for future use
c906108c 14698
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AC
14699@item remove break or watchpoint @strong{(draft)}
14700@tab @code{z}@var{t}@code{,}@var{addr}@code{,}@var{length}
14701@tab
14702See @samp{Z}.
c906108c 14703
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AC
14704@item insert break or watchpoint @strong{(draft)}
14705@tab @code{Z}@var{t}@code{,}@var{addr}@code{,}@var{length}
14706@tab
14707@var{t} is type: @samp{0} - software breakpoint, @samp{1} - hardware
14708breakpoint, @samp{2} - write watchpoint, @samp{3} - read watchpoint,
14709@samp{4} - access watchpoint; @var{addr} is address; @var{length} is in
14710bytes. For a software breakpoint, @var{length} specifies the size of
14711the instruction to be patched. For hardware breakpoints and watchpoints
14712@var{length} specifies the memory region to be monitored. To avoid
14713potential problems with duplicate packets, the operations should be
14714implemented in an idempotent way.
14715@item
14716@tab reply @code{E}@var{NN}
14717@tab for an error
14718@item
14719@tab reply @code{OK}
14720@tab for success
14721@item
14722@tab @samp{}
14723@tab If not supported.
c906108c 14724
8e04817f
AC
14725@item reserved
14726@tab <other>
14727@tab Reserved for future use
c906108c 14728
8e04817f 14729@end multitable
c906108c 14730
8e04817f
AC
14731The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
14732receive any of the below as a reply. In the case of the @samp{C},
14733@samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
14734when the target halts. In the below the exact meaning of @samp{signal
14735number} is poorly defined. In general one of the UNIX signal numbering
14736conventions is used.
c906108c 14737
8e04817f 14738@multitable @columnfractions .4 .6
c906108c 14739
8e04817f
AC
14740@item @code{S}@var{AA}
14741@tab @var{AA} is the signal number
c906108c 14742
8e04817f
AC
14743@item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
14744@tab
14745@var{AA} = two hex digit signal number; @var{n...} = register number
14746(hex), @var{r...} = target byte ordered register contents, size defined
14747by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
14748thread process ID, this is a hex integer; @var{n...} = other string not
14749starting with valid hex digit. @value{GDBN} should ignore this
14750@var{n...}, @var{r...} pair and go on to the next. This way we can
14751extend the protocol.
c906108c 14752
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AC
14753@item @code{W}@var{AA}
14754@tab
14755The process exited, and @var{AA} is the exit status. This is only
14756applicable for certains sorts of targets.
c906108c 14757
8e04817f
AC
14758@item @code{X}@var{AA}
14759@tab
14760The process terminated with signal @var{AA}.
c906108c 14761
8e04817f
AC
14762@item @code{N}@var{AA}@code{;}@var{t...}@code{;}@var{d...}@code{;}@var{b...} @strong{(obsolete)}
14763@tab
14764@var{AA} = signal number; @var{t...} = address of symbol "_start";
14765@var{d...} = base of data section; @var{b...} = base of bss section.
14766@emph{Note: only used by Cisco Systems targets. The difference between
14767this reply and the "qOffsets" query is that the 'N' packet may arrive
14768spontaneously whereas the 'qOffsets' is a query initiated by the host
14769debugger.}
c906108c 14770
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AC
14771@item @code{O}@var{XX...}
14772@tab
14773@var{XX...} is hex encoding of @sc{ascii} data. This can happen at any time
14774while the program is running and the debugger should continue to wait
14775for 'W', 'T', etc.
c906108c 14776
8e04817f 14777@end multitable
c906108c 14778
8e04817f 14779The following set and query packets have already been defined.
c906108c 14780
8e04817f 14781@multitable @columnfractions .2 .2 .6
c906108c 14782
8e04817f
AC
14783@item current thread
14784@tab @code{q}@code{C}
14785@tab Return the current thread id.
14786@item
14787@tab reply @code{QC}@var{pid}
14788@tab
14789Where @var{pid} is a HEX encoded 16 bit process id.
14790@item
14791@tab reply *
14792@tab Any other reply implies the old pid.
c906108c 14793
8e04817f
AC
14794@item all thread ids
14795@tab @code{q}@code{fThreadInfo}
14796@item
14797@tab @code{q}@code{sThreadInfo}
14798@tab
14799Obtain a list of active thread ids from the target (OS). Since there
14800may be too many active threads to fit into one reply packet, this query
14801works iteratively: it may require more than one query/reply sequence to
14802obtain the entire list of threads. The first query of the sequence will
14803be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
14804sequence will be the @code{qs}@code{ThreadInfo} query.
14805@item
14806@tab
14807@tab NOTE: replaces the @code{qL} query (see below).
14808@item
14809@tab reply @code{m}@var{<id>}
14810@tab A single thread id
14811@item
14812@tab reply @code{m}@var{<id>},@var{<id>...}
14813@tab a comma-separated list of thread ids
14814@item
14815@tab reply @code{l}
14816@tab (lower case 'el') denotes end of list.
14817@item
14818@tab
14819@tab
14820In response to each query, the target will reply with a list of one
14821or more thread ids, in big-endian hex, separated by commas. GDB will
14822respond to each reply with a request for more thread ids (using the
14823@code{qs} form of the query), until the target responds with @code{l}
14824(lower-case el, for @code{'last'}).
c906108c 14825
8e04817f
AC
14826@item extra thread info
14827@tab @code{q}@code{ThreadExtraInfo}@code{,}@var{id}
14828@tab
14829@item
14830@tab
14831@tab
14832Where @var{<id>} is a thread-id in big-endian hex.
14833Obtain a printable string description of a thread's attributes from
14834the target OS. This string may contain anything that the target OS
14835thinks is interesting for @value{GDBN} to tell the user about the thread.
14836The string is displayed in @value{GDBN}'s @samp{info threads} display.
14837Some examples of possible thread extra info strings are "Runnable", or
14838"Blocked on Mutex".
14839@item
14840@tab reply @var{XX...}
14841@tab
14842Where @var{XX...} is a hex encoding of @sc{ascii} data, comprising the
14843printable string containing the extra information about the thread's
14844attributes.
c906108c 14845
8e04817f
AC
14846@item query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
14847@tab @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread}
14848@tab
14849@item
14850@tab
14851@tab
14852Obtain thread information from RTOS. Where: @var{startflag} (one hex
14853digit) is one to indicate the first query and zero to indicate a
14854subsequent query; @var{threadcount} (two hex digits) is the maximum
14855number of threads the response packet can contain; and @var{nextthread}
14856(eight hex digits), for subsequent queries (@var{startflag} is zero), is
14857returned in the response as @var{argthread}.
14858@item
14859@tab
14860@tab NOTE: this query is replaced by the @code{q}@code{fThreadInfo}
14861query (see above).
14862@item
14863@tab reply @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread...}
14864@tab
14865@item
14866@tab
14867@tab
14868Where: @var{count} (two hex digits) is the number of threads being
14869returned; @var{done} (one hex digit) is zero to indicate more threads
14870and one indicates no further threads; @var{argthreadid} (eight hex
14871digits) is @var{nextthread} from the request packet; @var{thread...} is
14872a sequence of thread IDs from the target. @var{threadid} (eight hex
14873digits). See @code{remote.c:parse_threadlist_response()}.
c906108c 14874
8e04817f
AC
14875@item compute CRC of memory block
14876@tab @code{q}@code{CRC:}@var{addr}@code{,}@var{length}
14877@tab
14878@item
14879@tab reply @code{E}@var{NN}
14880@tab An error (such as memory fault)
14881@item
14882@tab reply @code{C}@var{CRC32}
14883@tab A 32 bit cyclic redundancy check of the specified memory region.
c906108c 14884
8e04817f
AC
14885@item query sect offs
14886@tab @code{q}@code{Offsets}
14887@tab
14888Get section offsets that the target used when re-locating the downloaded
14889image. @emph{Note: while a @code{Bss} offset is included in the
14890response, @value{GDBN} ignores this and instead applies the @code{Data}
14891offset to the @code{Bss} section.}
14892@item
14893@tab reply @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
c906108c 14894
8e04817f
AC
14895@item thread info request
14896@tab @code{q}@code{P}@var{mode}@var{threadid}
14897@tab
14898@item
14899@tab
14900@tab
14901Returns information on @var{threadid}. Where: @var{mode} is a hex
14902encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
14903@item
14904@tab reply *
14905@tab
14906See @code{remote.c:remote_unpack_thread_info_response()}.
c906108c 14907
8e04817f
AC
14908@item remote command
14909@tab @code{q}@code{Rcmd,}@var{COMMAND}
14910@tab
14911@item
14912@tab
14913@tab
14914@var{COMMAND} (hex encoded) is passed to the local interpreter for
14915execution. Invalid commands should be reported using the output string.
14916Before the final result packet, the target may also respond with a
14917number of intermediate @code{O}@var{OUTPUT} console output
14918packets. @emph{Implementors should note that providing access to a
14919stubs's interpreter may have security implications}.
14920@item
14921@tab reply @code{OK}
14922@tab
14923A command response with no output.
14924@item
14925@tab reply @var{OUTPUT}
14926@tab
14927A command response with the hex encoded output string @var{OUTPUT}.
14928@item
14929@tab reply @code{E}@var{NN}
14930@tab
14931Indicate a badly formed request.
c906108c 14932
8e04817f
AC
14933@item
14934@tab reply @samp{}
14935@tab
14936When @samp{q}@samp{Rcmd} is not recognized.
c906108c 14937
8e04817f
AC
14938@item symbol lookup
14939@tab @code{qSymbol::}
14940@tab
14941Notify the target that @value{GDBN} is prepared to serve symbol lookup
14942requests. Accept requests from the target for the values of symbols.
14943@item
14944@tab
14945@tab
14946@item
14947@tab reply @code{OK}
14948@tab
14949The target does not need to look up any (more) symbols.
14950@item
14951@tab reply @code{qSymbol:}@var{sym_name}
14952@tab
14953@sp 2
14954@noindent
14955The target requests the value of symbol @var{sym_name} (hex encoded).
14956@value{GDBN} may provide the value by using the
14957@code{qSymbol:}@var{sym_value}:@var{sym_name}
14958message, described below.
5d161b24 14959
8e04817f
AC
14960@item symbol value
14961@tab @code{qSymbol:}@var{sym_value}:@var{sym_name}
14962@tab
14963@sp 1
14964@noindent
14965Set the value of SYM_NAME to SYM_VALUE.
14966@item
14967@tab
14968@tab
14969@var{sym_name} (hex encoded) is the name of a symbol whose value
14970the target has previously requested.
14971@item
14972@tab
14973@tab
14974@var{sym_value} (hex) is the value for symbol @var{sym_name}.
14975If @value{GDBN} cannot supply a value for @var{sym_name}, then this
14976field will be empty.
14977@item
14978@tab reply @code{OK}
14979@tab
14980The target does not need to look up any (more) symbols.
14981@item
14982@tab reply @code{qSymbol:}@var{sym_name}
14983@tab
14984@sp 2
14985@noindent
14986The target requests the value of a new symbol @var{sym_name} (hex encoded).
14987@value{GDBN} will continue to supply the values of symbols (if available),
14988until the target ceases to request them.
eb12ee30 14989
8e04817f 14990@end multitable
eb12ee30 14991
8e04817f
AC
14992The following @samp{g}/@samp{G} packets have previously been defined.
14993In the below, some thirty-two bit registers are transferred as sixty-four
14994bits. Those registers should be zero/sign extended (which?) to fill the
14995space allocated. Register bytes are transfered in target byte order.
14996The two nibbles within a register byte are transfered most-significant -
14997least-significant.
eb12ee30 14998
8e04817f 14999@multitable @columnfractions .5 .5
eb12ee30 15000
8e04817f
AC
15001@item MIPS32
15002@tab
15003All registers are transfered as thirty-two bit quantities in the order:
1500432 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
15005registers; fsr; fir; fp.
eb12ee30 15006
8e04817f
AC
15007@item MIPS64
15008@tab
15009All registers are transfered as sixty-four bit quantities (including
15010thirty-two bit registers such as @code{sr}). The ordering is the same
15011as @code{MIPS32}.
eb12ee30 15012
8e04817f 15013@end multitable
eb12ee30 15014
8e04817f
AC
15015Example sequence of a target being re-started. Notice how the restart
15016does not get any direct output:
eb12ee30 15017
474c8240 15018@smallexample
8e04817f
AC
15019<- @code{R00}
15020-> @code{+}
15021@emph{target restarts}
15022<- @code{?}
15023-> @code{+}
15024-> @code{T001:1234123412341234}
15025<- @code{+}
474c8240 15026@end smallexample
eb12ee30 15027
8e04817f 15028Example sequence of a target being stepped by a single instruction:
eb12ee30 15029
474c8240 15030@smallexample
8e04817f
AC
15031<- @code{G1445...}
15032-> @code{+}
15033<- @code{s}
15034-> @code{+}
15035@emph{time passes}
15036-> @code{T001:1234123412341234}
15037<- @code{+}
15038<- @code{g}
15039-> @code{+}
15040-> @code{1455...}
15041<- @code{+}
474c8240 15042@end smallexample
eb12ee30 15043
aab4e0ec 15044@include gpl.texi
eb12ee30 15045
6826cf00
EZ
15046@include fdl.texi
15047
6d2ebf8b 15048@node Index
c906108c
SS
15049@unnumbered Index
15050
15051@printindex cp
15052
15053@tex
15054% I think something like @colophon should be in texinfo. In the
15055% meantime:
15056\long\def\colophon{\hbox to0pt{}\vfill
15057\centerline{The body of this manual is set in}
15058\centerline{\fontname\tenrm,}
15059\centerline{with headings in {\bf\fontname\tenbf}}
15060\centerline{and examples in {\tt\fontname\tentt}.}
15061\centerline{{\it\fontname\tenit\/},}
15062\centerline{{\bf\fontname\tenbf}, and}
15063\centerline{{\sl\fontname\tensl\/}}
15064\centerline{are used for emphasis.}\vfill}
15065\page\colophon
15066% Blame: doc@cygnus.com, 1991.
15067@end tex
15068
c906108c 15069@bye
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