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diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo deleted file mode 100644 index ed1fbc4134a..00000000000 --- a/gdb/doc/gdb.texinfo +++ /dev/null @@ -1,14877 +0,0 @@ -\input texinfo @c -*-texinfo-*- -@c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, -@c 1999, 2000, 2001, 2002 -@c Free Software Foundation, Inc. -@c -@c %**start of header -@c makeinfo ignores cmds prev to setfilename, so its arg cannot make use -@c of @set vars. However, you can override filename with makeinfo -o. -@setfilename gdb.info -@c -@include gdb-cfg.texi -@c -@settitle Debugging with @value{GDBN} -@setchapternewpage odd -@c %**end of header - -@iftex -@c @smallbook -@c @cropmarks -@end iftex - -@finalout -@syncodeindex ky cp - -@c readline appendices use @vindex, @findex and @ftable, -@c annotate.texi and gdbmi use @findex. -@syncodeindex vr cp -@syncodeindex fn cp - -@c !!set GDB manual's edition---not the same as GDB version! -@set EDITION Ninth - -@c !!set GDB manual's revision date -@set DATE December 2001 - -@c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER. - -@c This is a dir.info fragment to support semi-automated addition of -@c manuals to an info tree. -@dircategory Programming & development tools. -@direntry -* Gdb: (gdb). The @sc{gnu} debugger. -@end direntry - -@ifinfo -This file documents the @sc{gnu} debugger @value{GDBN}. - - -This is the @value{EDITION} Edition, @value{DATE}, -of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger} -for @value{GDBN} Version @value{GDBVN}. - -Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@* - 1999, 2000, 2001, 2002 Free Software Foundation, Inc. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.1 or -any later version published by the Free Software Foundation; with the -Invariant Sections being ``Free Software'' and ``Free Software Needs -Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' -and with the Back-Cover Texts as in (a) below. - -(a) The Free Software Foundation's Back-Cover Text is: ``You have -freedom to copy and modify this GNU Manual, like GNU software. Copies -published by the Free Software Foundation raise funds for GNU -development.'' -@end ifinfo - -@titlepage -@title Debugging with @value{GDBN} -@subtitle The @sc{gnu} Source-Level Debugger -@sp 1 -@subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN} -@subtitle @value{DATE} -@author Richard Stallman, Roland Pesch, Stan Shebs, et al. -@page -@tex -{\parskip=0pt -\hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par -\hfill {\it Debugging with @value{GDBN}}\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex - -@vskip 0pt plus 1filll -Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, -1996, 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc. -@sp 2 -Published by the Free Software Foundation @* -59 Temple Place - Suite 330, @* -Boston, MA 02111-1307 USA @* -ISBN 1-882114-77-9 @* - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.1 or -any later version published by the Free Software Foundation; with the -Invariant Sections being ``Free Software'' and ``Free Software Needs -Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' -and with the Back-Cover Texts as in (a) below. - -(a) The Free Software Foundation's Back-Cover Text is: ``You have -freedom to copy and modify this GNU Manual, like GNU software. Copies -published by the Free Software Foundation raise funds for GNU -development.'' -@end titlepage -@page - -@ifnottex -@node Top, Summary, (dir), (dir) - -@top Debugging with @value{GDBN} - -This file describes @value{GDBN}, the @sc{gnu} symbolic debugger. - -This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version -@value{GDBVN}. - -Copyright (C) 1988-2002 Free Software Foundation, Inc. - -@menu -* Summary:: Summary of @value{GDBN} -* Sample Session:: A sample @value{GDBN} session - -* Invocation:: Getting in and out of @value{GDBN} -* Commands:: @value{GDBN} commands -* Running:: Running programs under @value{GDBN} -* Stopping:: Stopping and continuing -* Stack:: Examining the stack -* Source:: Examining source files -* Data:: Examining data -* Tracepoints:: Debugging remote targets non-intrusively -* Overlays:: Debugging programs that use overlays - -* Languages:: Using @value{GDBN} with different languages - -* Symbols:: Examining the symbol table -* Altering:: Altering execution -* GDB Files:: @value{GDBN} files -* Targets:: Specifying a debugging target -* Remote Debugging:: Debugging remote programs -* Configurations:: Configuration-specific information -* Controlling GDB:: Controlling @value{GDBN} -* Sequences:: Canned sequences of commands -* TUI:: @value{GDBN} Text User Interface -* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs -* Annotations:: @value{GDBN}'s annotation interface. -* GDB/MI:: @value{GDBN}'s Machine Interface. - -* GDB Bugs:: Reporting bugs in @value{GDBN} -* Formatting Documentation:: How to format and print @value{GDBN} documentation - -* Command Line Editing:: Command Line Editing -* Using History Interactively:: Using History Interactively -* Installing GDB:: Installing GDB -* Maintenance Commands:: Maintenance Commands -* Remote Protocol:: GDB Remote Serial Protocol -* GNU Free Documentation License:: The license for this documentation -* Index:: Index -@end menu - -@end ifnottex - -@contents - -@node Summary -@unnumbered Summary of @value{GDBN} - -The purpose of a debugger such as @value{GDBN} is to allow you to see what is -going on ``inside'' another program while it executes---or what another -program was doing at the moment it crashed. - -@value{GDBN} can do four main kinds of things (plus other things in support of -these) to help you catch bugs in the act: - -@itemize @bullet -@item -Start your program, specifying anything that might affect its behavior. - -@item -Make your program stop on specified conditions. - -@item -Examine what has happened, when your program has stopped. - -@item -Change things in your program, so you can experiment with correcting the -effects of one bug and go on to learn about another. -@end itemize - -You can use @value{GDBN} to debug programs written in C and C++. -For more information, see @ref{Support,,Supported languages}. -For more information, see @ref{C,,C and C++}. - -@cindex Chill -@cindex Modula-2 -Support for Modula-2 and Chill is partial. For information on Modula-2, -see @ref{Modula-2,,Modula-2}. For information on Chill, see @ref{Chill}. - -@cindex Pascal -Debugging Pascal programs which use sets, subranges, file variables, or -nested functions does not currently work. @value{GDBN} does not support -entering expressions, printing values, or similar features using Pascal -syntax. - -@cindex Fortran -@value{GDBN} can be used to debug programs written in Fortran, although -it may be necessary to refer to some variables with a trailing -underscore. - -@menu -* Free Software:: Freely redistributable software -* Contributors:: Contributors to GDB -@end menu - -@node Free Software -@unnumberedsec Free software - -@value{GDBN} is @dfn{free software}, protected by the @sc{gnu} -General Public License -(GPL). The GPL gives you the freedom to copy or adapt a licensed -program---but every person getting a copy also gets with it the -freedom to modify that copy (which means that they must get access to -the source code), and the freedom to distribute further copies. -Typical software companies use copyrights to limit your freedoms; the -Free Software Foundation uses the GPL to preserve these freedoms. - -Fundamentally, the General Public License is a license which says that -you have these freedoms and that you cannot take these freedoms away -from anyone else. - -@unnumberedsec Free Software Needs Free Documentation - -The biggest deficiency in the free software community today is not in -the software---it is the lack of good free documentation that we can -include with the free software. Many of our most important -programs do not come with free reference manuals and free introductory -texts. Documentation is an essential part of any software package; -when an important free software package does not come with a free -manual and a free tutorial, that is a major gap. We have many such -gaps today. - -Consider Perl, for instance. The tutorial manuals that people -normally use are non-free. How did this come about? Because the -authors of those manuals published them with restrictive terms---no -copying, no modification, source files not available---which exclude -them from the free software world. - -That wasn't the first time this sort of thing happened, and it was far -from the last. Many times we have heard a GNU user eagerly describe a -manual that he is writing, his intended contribution to the community, -only to learn that he had ruined everything by signing a publication -contract to make it non-free. - -Free documentation, like free software, is a matter of freedom, not -price. The problem with the non-free manual is not that publishers -charge a price for printed copies---that in itself is fine. (The Free -Software Foundation sells printed copies of manuals, too.) The -problem is the restrictions on the use of the manual. Free manuals -are available in source code form, and give you permission to copy and -modify. Non-free manuals do not allow this. - -The criteria of freedom for a free manual are roughly the same as for -free software. Redistribution (including the normal kinds of -commercial redistribution) must be permitted, so that the manual can -accompany every copy of the program, both on-line and on paper. - -Permission for modification of the technical content is crucial too. -When people modify the software, adding or changing features, if they -are conscientious they will change the manual too---so they can -provide accurate and clear documentation for the modified program. A -manual that leaves you no choice but to write a new manual to document -a changed version of the program is not really available to our -community. - -Some kinds of limits on the way modification is handled are -acceptable. For example, requirements to preserve the original -author's copyright notice, the distribution terms, or the list of -authors, are ok. It is also no problem to require modified versions -to include notice that they were modified. Even entire sections that -may not be deleted or changed are acceptable, as long as they deal -with nontechnical topics (like this one). These kinds of restrictions -are acceptable because they don't obstruct the community's normal use -of the manual. - -However, it must be possible to modify all the @emph{technical} -content of the manual, and then distribute the result in all the usual -media, through all the usual channels. Otherwise, the restrictions -obstruct the use of the manual, it is not free, and we need another -manual to replace it. - -Please spread the word about this issue. Our community continues to -lose manuals to proprietary publishing. If we spread the word that -free software needs free reference manuals and free tutorials, perhaps -the next person who wants to contribute by writing documentation will -realize, before it is too late, that only free manuals contribute to -the free software community. - -If you are writing documentation, please insist on publishing it under -the GNU Free Documentation License or another free documentation -license. Remember that this decision requires your approval---you -don't have to let the publisher decide. Some commercial publishers -will use a free license if you insist, but they will not propose the -option; it is up to you to raise the issue and say firmly that this is -what you want. If the publisher you are dealing with refuses, please -try other publishers. If you're not sure whether a proposed license -is free, write to @email{licensing@@gnu.org}. - -You can encourage commercial publishers to sell more free, copylefted -manuals and tutorials by buying them, and particularly by buying -copies from the publishers that paid for their writing or for major -improvements. Meanwhile, try to avoid buying non-free documentation -at all. Check the distribution terms of a manual before you buy it, -and insist that whoever seeks your business must respect your freedom. -Check the history of the book, and try to reward the publishers that -have paid or pay the authors to work on it. - -The Free Software Foundation maintains a list of free documentation -published by other publishers, at -@url{http://www.fsf.org/doc/other-free-books.html}. - -@node Contributors -@unnumberedsec Contributors to @value{GDBN} - -Richard Stallman was the original author of @value{GDBN}, and of many -other @sc{gnu} programs. Many others have contributed to its -development. This section attempts to credit major contributors. One -of the virtues of free software is that everyone is free to contribute -to it; with regret, we cannot actually acknowledge everyone here. The -file @file{ChangeLog} in the @value{GDBN} distribution approximates a -blow-by-blow account. - -Changes much prior to version 2.0 are lost in the mists of time. - -@quotation -@emph{Plea:} Additions to this section are particularly welcome. If you -or your friends (or enemies, to be evenhanded) have been unfairly -omitted from this list, we would like to add your names! -@end quotation - -So that they may not regard their many labors as thankless, we -particularly thank those who shepherded @value{GDBN} through major -releases: -Andrew Cagney (releases 5.0 and 5.1); -Jim Blandy (release 4.18); -Jason Molenda (release 4.17); -Stan Shebs (release 4.14); -Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9); -Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4); -John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); -Jim Kingdon (releases 3.5, 3.4, and 3.3); -and Randy Smith (releases 3.2, 3.1, and 3.0). - -Richard Stallman, assisted at various times by Peter TerMaat, Chris -Hanson, and Richard Mlynarik, handled releases through 2.8. - -Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support -in @value{GDBN}, with significant additional contributions from Per -Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++} -demangler. Early work on C@t{++} was by Peter TerMaat (who also did -much general update work leading to release 3.0). - -@value{GDBN} uses the BFD subroutine library to examine multiple -object-file formats; BFD was a joint project of David V. -Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. - -David Johnson wrote the original COFF support; Pace Willison did -the original support for encapsulated COFF. - -Brent Benson of Harris Computer Systems contributed DWARF2 support. - -Adam de Boor and Bradley Davis contributed the ISI Optimum V support. -Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS -support. -Jean-Daniel Fekete contributed Sun 386i support. -Chris Hanson improved the HP9000 support. -Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support. -David Johnson contributed Encore Umax support. -Jyrki Kuoppala contributed Altos 3068 support. -Jeff Law contributed HP PA and SOM support. -Keith Packard contributed NS32K support. -Doug Rabson contributed Acorn Risc Machine support. -Bob Rusk contributed Harris Nighthawk CX-UX support. -Chris Smith contributed Convex support (and Fortran debugging). -Jonathan Stone contributed Pyramid support. -Michael Tiemann contributed SPARC support. -Tim Tucker contributed support for the Gould NP1 and Gould Powernode. -Pace Willison contributed Intel 386 support. -Jay Vosburgh contributed Symmetry support. - -Andreas Schwab contributed M68K Linux support. - -Rich Schaefer and Peter Schauer helped with support of SunOS shared -libraries. - -Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree -about several machine instruction sets. - -Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop -remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM -contributed remote debugging modules for the i960, VxWorks, A29K UDI, -and RDI targets, respectively. - -Brian Fox is the author of the readline libraries providing -command-line editing and command history. - -Andrew Beers of SUNY Buffalo wrote the language-switching code, the -Modula-2 support, and contributed the Languages chapter of this manual. - -Fred Fish wrote most of the support for Unix System Vr4. -He also enhanced the command-completion support to cover C@t{++} overloaded -symbols. - -Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and -Super-H processors. - -NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors. - -Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors. - -Toshiba sponsored the support for the TX39 Mips processor. - -Matsushita sponsored the support for the MN10200 and MN10300 processors. - -Fujitsu sponsored the support for SPARClite and FR30 processors. - -Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware -watchpoints. - -Michael Snyder added support for tracepoints. - -Stu Grossman wrote gdbserver. - -Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made -nearly innumerable bug fixes and cleanups throughout @value{GDBN}. - -The following people at the Hewlett-Packard Company contributed -support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0 -(narrow mode), HP's implementation of kernel threads, HP's aC@t{++} -compiler, and the terminal user interface: Ben Krepp, Richard Title, -John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve -Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific -information in this manual. - -DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project. -Robert Hoehne made significant contributions to the DJGPP port. - -Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its -development since 1991. Cygnus engineers who have worked on @value{GDBN} -fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin -Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim -Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler, -Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek -Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In -addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton, -JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug -Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff -Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner, -Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin -Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela -Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David -Zuhn have made contributions both large and small. - - -@node Sample Session -@chapter A Sample @value{GDBN} Session - -You can use this manual at your leisure to read all about @value{GDBN}. -However, a handful of commands are enough to get started using the -debugger. This chapter illustrates those commands. - -@iftex -In this sample session, we emphasize user input like this: @b{input}, -to make it easier to pick out from the surrounding output. -@end iftex - -@c FIXME: this example may not be appropriate for some configs, where -@c FIXME...primary interest is in remote use. - -One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro -processor) exhibits the following bug: sometimes, when we change its -quote strings from the default, the commands used to capture one macro -definition within another stop working. In the following short @code{m4} -session, we define a macro @code{foo} which expands to @code{0000}; we -then use the @code{m4} built-in @code{defn} to define @code{bar} as the -same thing. However, when we change the open quote string to -@code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same -procedure fails to define a new synonym @code{baz}: - -@smallexample -$ @b{cd gnu/m4} -$ @b{./m4} -@b{define(foo,0000)} - -@b{foo} -0000 -@b{define(bar,defn(`foo'))} - -@b{bar} -0000 -@b{changequote(<QUOTE>,<UNQUOTE>)} - -@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} -@b{baz} -@b{C-d} -m4: End of input: 0: fatal error: EOF in string -@end smallexample - -@noindent -Let us use @value{GDBN} to try to see what is going on. - -@smallexample -$ @b{@value{GDBP} m4} -@c FIXME: this falsifies the exact text played out, to permit smallbook -@c FIXME... format to come out better. -@value{GDBN} is free software and you are welcome to distribute copies - of it under certain conditions; type "show copying" to see - the conditions. -There is absolutely no warranty for @value{GDBN}; type "show warranty" - for details. - -@value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc... -(@value{GDBP}) -@end smallexample - -@noindent -@value{GDBN} reads only enough symbol data to know where to find the -rest when needed; as a result, the first prompt comes up very quickly. -We now tell @value{GDBN} to use a narrower display width than usual, so -that examples fit in this manual. - -@smallexample -(@value{GDBP}) @b{set width 70} -@end smallexample - -@noindent -We need to see how the @code{m4} built-in @code{changequote} works. -Having looked at the source, we know the relevant subroutine is -@code{m4_changequote}, so we set a breakpoint there with the @value{GDBN} -@code{break} command. - -@smallexample -(@value{GDBP}) @b{break m4_changequote} -Breakpoint 1 at 0x62f4: file builtin.c, line 879. -@end smallexample - -@noindent -Using the @code{run} command, we start @code{m4} running under @value{GDBN} -control; as long as control does not reach the @code{m4_changequote} -subroutine, the program runs as usual: - -@smallexample -(@value{GDBP}) @b{run} -Starting program: /work/Editorial/gdb/gnu/m4/m4 -@b{define(foo,0000)} - -@b{foo} -0000 -@end smallexample - -@noindent -To trigger the breakpoint, we call @code{changequote}. @value{GDBN} -suspends execution of @code{m4}, displaying information about the -context where it stops. - -@smallexample -@b{changequote(<QUOTE>,<UNQUOTE>)} - -Breakpoint 1, m4_changequote (argc=3, argv=0x33c70) - at builtin.c:879 -879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3)) -@end smallexample - -@noindent -Now we use the command @code{n} (@code{next}) to advance execution to -the next line of the current function. - -@smallexample -(@value{GDBP}) @b{n} -882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\ - : nil, -@end smallexample - -@noindent -@code{set_quotes} looks like a promising subroutine. We can go into it -by using the command @code{s} (@code{step}) instead of @code{next}. -@code{step} goes to the next line to be executed in @emph{any} -subroutine, so it steps into @code{set_quotes}. - -@smallexample -(@value{GDBP}) @b{s} -set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -530 if (lquote != def_lquote) -@end smallexample - -@noindent -The display that shows the subroutine where @code{m4} is now -suspended (and its arguments) is called a stack frame display. It -shows a summary of the stack. We can use the @code{backtrace} -command (which can also be spelled @code{bt}), to see where we are -in the stack as a whole: the @code{backtrace} command displays a -stack frame for each active subroutine. - -@smallexample -(@value{GDBP}) @b{bt} -#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -#1 0x6344 in m4_changequote (argc=3, argv=0x33c70) - at builtin.c:882 -#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242 -#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30) - at macro.c:71 -#4 0x79dc in expand_input () at macro.c:40 -#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195 -@end smallexample - -@noindent -We step through a few more lines to see what happens. The first two -times, we can use @samp{s}; the next two times we use @code{n} to avoid -falling into the @code{xstrdup} subroutine. - -@smallexample -(@value{GDBP}) @b{s} -0x3b5c 532 if (rquote != def_rquote) -(@value{GDBP}) @b{s} -0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \ -def_lquote : xstrdup(lq); -(@value{GDBP}) @b{n} -536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ - : xstrdup(rq); -(@value{GDBP}) @b{n} -538 len_lquote = strlen(rquote); -@end smallexample - -@noindent -The last line displayed looks a little odd; we can examine the variables -@code{lquote} and @code{rquote} to see if they are in fact the new left -and right quotes we specified. We use the command @code{p} -(@code{print}) to see their values. - -@smallexample -(@value{GDBP}) @b{p lquote} -$1 = 0x35d40 "<QUOTE>" -(@value{GDBP}) @b{p rquote} -$2 = 0x35d50 "<UNQUOTE>" -@end smallexample - -@noindent -@code{lquote} and @code{rquote} are indeed the new left and right quotes. -To look at some context, we can display ten lines of source -surrounding the current line with the @code{l} (@code{list}) command. - -@smallexample -(@value{GDBP}) @b{l} -533 xfree(rquote); -534 -535 lquote = (lq == nil || *lq == '\0') ? def_lquote\ - : xstrdup (lq); -536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ - : xstrdup (rq); -537 -538 len_lquote = strlen(rquote); -539 len_rquote = strlen(lquote); -540 @} -541 -542 void -@end smallexample - -@noindent -Let us step past the two lines that set @code{len_lquote} and -@code{len_rquote}, and then examine the values of those variables. - -@smallexample -(@value{GDBP}) @b{n} -539 len_rquote = strlen(lquote); -(@value{GDBP}) @b{n} -540 @} -(@value{GDBP}) @b{p len_lquote} -$3 = 9 -(@value{GDBP}) @b{p len_rquote} -$4 = 7 -@end smallexample - -@noindent -That certainly looks wrong, assuming @code{len_lquote} and -@code{len_rquote} are meant to be the lengths of @code{lquote} and -@code{rquote} respectively. We can set them to better values using -the @code{p} command, since it can print the value of -any expression---and that expression can include subroutine calls and -assignments. - -@smallexample -(@value{GDBP}) @b{p len_lquote=strlen(lquote)} -$5 = 7 -(@value{GDBP}) @b{p len_rquote=strlen(rquote)} -$6 = 9 -@end smallexample - -@noindent -Is that enough to fix the problem of using the new quotes with the -@code{m4} built-in @code{defn}? We can allow @code{m4} to continue -executing with the @code{c} (@code{continue}) command, and then try the -example that caused trouble initially: - -@smallexample -(@value{GDBP}) @b{c} -Continuing. - -@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} - -baz -0000 -@end smallexample - -@noindent -Success! The new quotes now work just as well as the default ones. The -problem seems to have been just the two typos defining the wrong -lengths. We allow @code{m4} exit by giving it an EOF as input: - -@smallexample -@b{C-d} -Program exited normally. -@end smallexample - -@noindent -The message @samp{Program exited normally.} is from @value{GDBN}; it -indicates @code{m4} has finished executing. We can end our @value{GDBN} -session with the @value{GDBN} @code{quit} command. - -@smallexample -(@value{GDBP}) @b{quit} -@end smallexample - -@node Invocation -@chapter Getting In and Out of @value{GDBN} - -This chapter discusses how to start @value{GDBN}, and how to get out of it. -The essentials are: -@itemize @bullet -@item -type @samp{@value{GDBP}} to start @value{GDBN}. -@item -type @kbd{quit} or @kbd{C-d} to exit. -@end itemize - -@menu -* Invoking GDB:: How to start @value{GDBN} -* Quitting GDB:: How to quit @value{GDBN} -* Shell Commands:: How to use shell commands inside @value{GDBN} -@end menu - -@node Invoking GDB -@section Invoking @value{GDBN} - -Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started, -@value{GDBN} reads commands from the terminal until you tell it to exit. - -You can also run @code{@value{GDBP}} with a variety of arguments and options, -to specify more of your debugging environment at the outset. - -The command-line options described here are designed -to cover a variety of situations; in some environments, some of these -options may effectively be unavailable. - -The most usual way to start @value{GDBN} is with one argument, -specifying an executable program: - -@example -@value{GDBP} @var{program} -@end example - -@noindent -You can also start with both an executable program and a core file -specified: - -@example -@value{GDBP} @var{program} @var{core} -@end example - -You can, instead, specify a process ID as a second argument, if you want -to debug a running process: - -@example -@value{GDBP} @var{program} 1234 -@end example - -@noindent -would attach @value{GDBN} to process @code{1234} (unless you also have a file -named @file{1234}; @value{GDBN} does check for a core file first). - -Taking advantage of the second command-line argument requires a fairly -complete operating system; when you use @value{GDBN} as a remote -debugger attached to a bare board, there may not be any notion of -``process'', and there is often no way to get a core dump. @value{GDBN} -will warn you if it is unable to attach or to read core dumps. - -You can optionally have @code{@value{GDBP}} pass any arguments after the -executable file to the inferior using @code{--args}. This option stops -option processing. -@example -gdb --args gcc -O2 -c foo.c -@end example -This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set -@code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}. - -You can run @code{@value{GDBP}} without printing the front material, which describes -@value{GDBN}'s non-warranty, by specifying @code{-silent}: - -@smallexample -@value{GDBP} -silent -@end smallexample - -@noindent -You can further control how @value{GDBN} starts up by using command-line -options. @value{GDBN} itself can remind you of the options available. - -@noindent -Type - -@example -@value{GDBP} -help -@end example - -@noindent -to display all available options and briefly describe their use -(@samp{@value{GDBP} -h} is a shorter equivalent). - -All options and command line arguments you give are processed -in sequential order. The order makes a difference when the -@samp{-x} option is used. - - -@menu -* File Options:: Choosing files -* Mode Options:: Choosing modes -@end menu - -@node File Options -@subsection Choosing files - -When @value{GDBN} starts, it reads any arguments other than options as -specifying an executable file and core file (or process ID). This is -the same as if the arguments were specified by the @samp{-se} and -@samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the -first argument that does not have an associated option flag as -equivalent to the @samp{-se} option followed by that argument; and the -second argument that does not have an associated option flag, if any, as -equivalent to the @samp{-c}/@samp{-p} option followed by that argument.) -If the second argument begins with a decimal digit, @value{GDBN} will -first attempt to attach to it as a process, and if that fails, attempt -to open it as a corefile. If you have a corefile whose name begins with -a digit, you can prevent @value{GDBN} from treating it as a pid by -prefixing it with @file{./}, eg. @file{./12345}. - -If @value{GDBN} has not been configured to included core file support, -such as for most embedded targets, then it will complain about a second -argument and ignore it. - -Many options have both long and short forms; both are shown in the -following list. @value{GDBN} also recognizes the long forms if you truncate -them, so long as enough of the option is present to be unambiguous. -(If you prefer, you can flag option arguments with @samp{--} rather -than @samp{-}, though we illustrate the more usual convention.) - -@c NOTE: the @cindex entries here use double dashes ON PURPOSE. This -@c way, both those who look for -foo and --foo in the index, will find -@c it. - -@table @code -@item -symbols @var{file} -@itemx -s @var{file} -@cindex @code{--symbols} -@cindex @code{-s} -Read symbol table from file @var{file}. - -@item -exec @var{file} -@itemx -e @var{file} -@cindex @code{--exec} -@cindex @code{-e} -Use file @var{file} as the executable file to execute when appropriate, -and for examining pure data in conjunction with a core dump. - -@item -se @var{file} -@cindex @code{--se} -Read symbol table from file @var{file} and use it as the executable -file. - -@item -core @var{file} -@itemx -c @var{file} -@cindex @code{--core} -@cindex @code{-c} -Use file @var{file} as a core dump to examine. - -@item -c @var{number} -@item -pid @var{number} -@itemx -p @var{number} -@cindex @code{--pid} -@cindex @code{-p} -Connect to process ID @var{number}, as with the @code{attach} command. -If there is no such process, @value{GDBN} will attempt to open a core -file named @var{number}. - -@item -command @var{file} -@itemx -x @var{file} -@cindex @code{--command} -@cindex @code{-x} -Execute @value{GDBN} commands from file @var{file}. @xref{Command -Files,, Command files}. - -@item -directory @var{directory} -@itemx -d @var{directory} -@cindex @code{--directory} -@cindex @code{-d} -Add @var{directory} to the path to search for source files. - -@item -m -@itemx -mapped -@cindex @code{--mapped} -@cindex @code{-m} -@emph{Warning: this option depends on operating system facilities that are not -supported on all systems.}@* -If memory-mapped files are available on your system through the @code{mmap} -system call, you can use this option -to have @value{GDBN} write the symbols from your -program into a reusable file in the current directory. If the program you are debugging is -called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}. -Future @value{GDBN} debugging sessions notice the presence of this file, -and can quickly map in symbol information from it, rather than reading -the symbol table from the executable program. - -The @file{.syms} file is specific to the host machine where @value{GDBN} -is run. It holds an exact image of the internal @value{GDBN} symbol -table. It cannot be shared across multiple host platforms. - -@item -r -@itemx -readnow -@cindex @code{--readnow} -@cindex @code{-r} -Read each symbol file's entire symbol table immediately, rather than -the default, which is to read it incrementally as it is needed. -This makes startup slower, but makes future operations faster. - -@end table - -You typically combine the @code{-mapped} and @code{-readnow} options in -order to build a @file{.syms} file that contains complete symbol -information. (@xref{Files,,Commands to specify files}, for information -on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing -but build a @file{.syms} file for future use is: - -@example -gdb -batch -nx -mapped -readnow programname -@end example - -@node Mode Options -@subsection Choosing modes - -You can run @value{GDBN} in various alternative modes---for example, in -batch mode or quiet mode. - -@table @code -@item -nx -@itemx -n -@cindex @code{--nx} -@cindex @code{-n} -Do not execute commands found in any initialization files. Normally, -@value{GDBN} executes the commands in these files after all the command -options and arguments have been processed. @xref{Command Files,,Command -files}. - -@item -quiet -@itemx -silent -@itemx -q -@cindex @code{--quiet} -@cindex @code{--silent} -@cindex @code{-q} -``Quiet''. Do not print the introductory and copyright messages. These -messages are also suppressed in batch mode. - -@item -batch -@cindex @code{--batch} -Run in batch mode. Exit with status @code{0} after processing all the -command files specified with @samp{-x} (and all commands from -initialization files, if not inhibited with @samp{-n}). Exit with -nonzero status if an error occurs in executing the @value{GDBN} commands -in the command files. - -Batch mode may be useful for running @value{GDBN} as a filter, for -example to download and run a program on another computer; in order to -make this more useful, the message - -@example -Program exited normally. -@end example - -@noindent -(which is ordinarily issued whenever a program running under -@value{GDBN} control terminates) is not issued when running in batch -mode. - -@item -nowindows -@itemx -nw -@cindex @code{--nowindows} -@cindex @code{-nw} -``No windows''. If @value{GDBN} comes with a graphical user interface -(GUI) built in, then this option tells @value{GDBN} to only use the command-line -interface. If no GUI is available, this option has no effect. - -@item -windows -@itemx -w -@cindex @code{--windows} -@cindex @code{-w} -If @value{GDBN} includes a GUI, then this option requires it to be -used if possible. - -@item -cd @var{directory} -@cindex @code{--cd} -Run @value{GDBN} using @var{directory} as its working directory, -instead of the current directory. - -@item -fullname -@itemx -f -@cindex @code{--fullname} -@cindex @code{-f} -@sc{gnu} Emacs sets this option when it runs @value{GDBN} as a -subprocess. It tells @value{GDBN} to output the full file name and line -number in a standard, recognizable fashion each time a stack frame is -displayed (which includes each time your program stops). This -recognizable format looks like two @samp{\032} characters, followed by -the file name, line number and character position separated by colons, -and a newline. The Emacs-to-@value{GDBN} interface program uses the two -@samp{\032} characters as a signal to display the source code for the -frame. - -@item -epoch -@cindex @code{--epoch} -The Epoch Emacs-@value{GDBN} interface sets this option when it runs -@value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print -routines so as to allow Epoch to display values of expressions in a -separate window. - -@item -annotate @var{level} -@cindex @code{--annotate} -This option sets the @dfn{annotation level} inside @value{GDBN}. Its -effect is identical to using @samp{set annotate @var{level}} -(@pxref{Annotations}). -Annotation level controls how much information does @value{GDBN} print -together with its prompt, values of expressions, source lines, and other -types of output. Level 0 is the normal, level 1 is for use when -@value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the -maximum annotation suitable for programs that control @value{GDBN}. - -@item -async -@cindex @code{--async} -Use the asynchronous event loop for the command-line interface. -@value{GDBN} processes all events, such as user keyboard input, via a -special event loop. This allows @value{GDBN} to accept and process user -commands in parallel with the debugged process being -run@footnote{@value{GDBN} built with @sc{djgpp} tools for -MS-DOS/MS-Windows supports this mode of operation, but the event loop is -suspended when the debuggee runs.}, so you don't need to wait for -control to return to @value{GDBN} before you type the next command. -(@emph{Note:} as of version 5.1, the target side of the asynchronous -operation is not yet in place, so @samp{-async} does not work fully -yet.) -@c FIXME: when the target side of the event loop is done, the above NOTE -@c should be removed. - -When the standard input is connected to a terminal device, @value{GDBN} -uses the asynchronous event loop by default, unless disabled by the -@samp{-noasync} option. - -@item -noasync -@cindex @code{--noasync} -Disable the asynchronous event loop for the command-line interface. - -@item --args -@cindex @code{--args} -Change interpretation of command line so that arguments following the -executable file are passed as command line arguments to the inferior. -This option stops option processing. - -@item -baud @var{bps} -@itemx -b @var{bps} -@cindex @code{--baud} -@cindex @code{-b} -Set the line speed (baud rate or bits per second) of any serial -interface used by @value{GDBN} for remote debugging. - -@item -tty @var{device} -@itemx -t @var{device} -@cindex @code{--tty} -@cindex @code{-t} -Run using @var{device} for your program's standard input and output. -@c FIXME: kingdon thinks there is more to -tty. Investigate. - -@c resolve the situation of these eventually -@item -tui -@cindex @code{--tui} -Activate the Terminal User Interface when starting. -The Terminal User Interface manages several text windows on the terminal, -showing source, assembly, registers and @value{GDBN} command outputs -(@pxref{TUI, ,@value{GDBN} Text User Interface}). -Do not use this option if you run @value{GDBN} from Emacs -(@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}). - -@c @item -xdb -@c @cindex @code{--xdb} -@c Run in XDB compatibility mode, allowing the use of certain XDB commands. -@c For information, see the file @file{xdb_trans.html}, which is usually -@c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX -@c systems. - -@item -interpreter @var{interp} -@cindex @code{--interpreter} -Use the interpreter @var{interp} for interface with the controlling -program or device. This option is meant to be set by programs which -communicate with @value{GDBN} using it as a back end. - -@samp{--interpreter=mi} (or @samp{--interpreter=mi1}) causes -@value{GDBN} to use the @dfn{gdb/mi interface} (@pxref{GDB/MI, , The -@sc{gdb/mi} Interface}). The older @sc{gdb/mi} interface, included in -@value{GDBN} version 5.0 can be selected with @samp{--interpreter=mi0}. - -@item -write -@cindex @code{--write} -Open the executable and core files for both reading and writing. This -is equivalent to the @samp{set write on} command inside @value{GDBN} -(@pxref{Patching}). - -@item -statistics -@cindex @code{--statistics} -This option causes @value{GDBN} to print statistics about time and -memory usage after it completes each command and returns to the prompt. - -@item -version -@cindex @code{--version} -This option causes @value{GDBN} to print its version number and -no-warranty blurb, and exit. - -@end table - -@node Quitting GDB -@section Quitting @value{GDBN} -@cindex exiting @value{GDBN} -@cindex leaving @value{GDBN} - -@table @code -@kindex quit @r{[}@var{expression}@r{]} -@kindex q @r{(@code{quit})} -@item quit @r{[}@var{expression}@r{]} -@itemx q -To exit @value{GDBN}, use the @code{quit} command (abbreviated -@code{q}), or type an end-of-file character (usually @kbd{C-d}). If you -do not supply @var{expression}, @value{GDBN} will terminate normally; -otherwise it will terminate using the result of @var{expression} as the -error code. -@end table - -@cindex interrupt -An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather -terminates the action of any @value{GDBN} command that is in progress and -returns to @value{GDBN} command level. It is safe to type the interrupt -character at any time because @value{GDBN} does not allow it to take effect -until a time when it is safe. - -If you have been using @value{GDBN} to control an attached process or -device, you can release it with the @code{detach} command -(@pxref{Attach, ,Debugging an already-running process}). - -@node Shell Commands -@section Shell commands - -If you need to execute occasional shell commands during your -debugging session, there is no need to leave or suspend @value{GDBN}; you can -just use the @code{shell} command. - -@table @code -@kindex shell -@cindex shell escape -@item shell @var{command string} -Invoke a standard shell to execute @var{command string}. -If it exists, the environment variable @code{SHELL} determines which -shell to run. Otherwise @value{GDBN} uses the default shell -(@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.). -@end table - -The utility @code{make} is often needed in development environments. -You do not have to use the @code{shell} command for this purpose in -@value{GDBN}: - -@table @code -@kindex make -@cindex calling make -@item make @var{make-args} -Execute the @code{make} program with the specified -arguments. This is equivalent to @samp{shell make @var{make-args}}. -@end table - -@node Commands -@chapter @value{GDBN} Commands - -You can abbreviate a @value{GDBN} command to the first few letters of the command -name, if that abbreviation is unambiguous; and you can repeat certain -@value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB} -key to get @value{GDBN} to fill out the rest of a word in a command (or to -show you the alternatives available, if there is more than one possibility). - -@menu -* Command Syntax:: How to give commands to @value{GDBN} -* Completion:: Command completion -* Help:: How to ask @value{GDBN} for help -@end menu - -@node Command Syntax -@section Command syntax - -A @value{GDBN} command is a single line of input. There is no limit on -how long it can be. It starts with a command name, which is followed by -arguments whose meaning depends on the command name. For example, the -command @code{step} accepts an argument which is the number of times to -step, as in @samp{step 5}. You can also use the @code{step} command -with no arguments. Some commands do not allow any arguments. - -@cindex abbreviation -@value{GDBN} command names may always be truncated if that abbreviation is -unambiguous. Other possible command abbreviations are listed in the -documentation for individual commands. In some cases, even ambiguous -abbreviations are allowed; for example, @code{s} is specially defined as -equivalent to @code{step} even though there are other commands whose -names start with @code{s}. You can test abbreviations by using them as -arguments to the @code{help} command. - -@cindex repeating commands -@kindex RET @r{(repeat last command)} -A blank line as input to @value{GDBN} (typing just @key{RET}) means to -repeat the previous command. Certain commands (for example, @code{run}) -will not repeat this way; these are commands whose unintentional -repetition might cause trouble and which you are unlikely to want to -repeat. - -The @code{list} and @code{x} commands, when you repeat them with -@key{RET}, construct new arguments rather than repeating -exactly as typed. This permits easy scanning of source or memory. - -@value{GDBN} can also use @key{RET} in another way: to partition lengthy -output, in a way similar to the common utility @code{more} -(@pxref{Screen Size,,Screen size}). Since it is easy to press one -@key{RET} too many in this situation, @value{GDBN} disables command -repetition after any command that generates this sort of display. - -@kindex # @r{(a comment)} -@cindex comment -Any text from a @kbd{#} to the end of the line is a comment; it does -nothing. This is useful mainly in command files (@pxref{Command -Files,,Command files}). - -@cindex repeating command sequences -@kindex C-o @r{(operate-and-get-next)} -The @kbd{C-o} binding is useful for repeating a complex sequence of -commands. This command accepts the current line, like @kbd{RET}, and -then fetches the next line relative to the current line from the history -for editing. - -@node Completion -@section Command completion - -@cindex completion -@cindex word completion -@value{GDBN} can fill in the rest of a word in a command for you, if there is -only one possibility; it can also show you what the valid possibilities -are for the next word in a command, at any time. This works for @value{GDBN} -commands, @value{GDBN} subcommands, and the names of symbols in your program. - -Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest -of a word. If there is only one possibility, @value{GDBN} fills in the -word, and waits for you to finish the command (or press @key{RET} to -enter it). For example, if you type - -@c FIXME "@key" does not distinguish its argument sufficiently to permit -@c complete accuracy in these examples; space introduced for clarity. -@c If texinfo enhancements make it unnecessary, it would be nice to -@c replace " @key" by "@key" in the following... -@example -(@value{GDBP}) info bre @key{TAB} -@end example - -@noindent -@value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is -the only @code{info} subcommand beginning with @samp{bre}: - -@example -(@value{GDBP}) info breakpoints -@end example - -@noindent -You can either press @key{RET} at this point, to run the @code{info -breakpoints} command, or backspace and enter something else, if -@samp{breakpoints} does not look like the command you expected. (If you -were sure you wanted @code{info breakpoints} in the first place, you -might as well just type @key{RET} immediately after @samp{info bre}, -to exploit command abbreviations rather than command completion). - -If there is more than one possibility for the next word when you press -@key{TAB}, @value{GDBN} sounds a bell. You can either supply more -characters and try again, or just press @key{TAB} a second time; -@value{GDBN} displays all the possible completions for that word. For -example, you might want to set a breakpoint on a subroutine whose name -begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN} -just sounds the bell. Typing @key{TAB} again displays all the -function names in your program that begin with those characters, for -example: - -@example -(@value{GDBP}) b make_ @key{TAB} -@exdent @value{GDBN} sounds bell; press @key{TAB} again, to see: -make_a_section_from_file make_environ -make_abs_section make_function_type -make_blockvector make_pointer_type -make_cleanup make_reference_type -make_command make_symbol_completion_list -(@value{GDBP}) b make_ -@end example - -@noindent -After displaying the available possibilities, @value{GDBN} copies your -partial input (@samp{b make_} in the example) so you can finish the -command. - -If you just want to see the list of alternatives in the first place, you -can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?} -means @kbd{@key{META} ?}. You can type this either by holding down a -key designated as the @key{META} shift on your keyboard (if there is -one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}. - -@cindex quotes in commands -@cindex completion of quoted strings -Sometimes the string you need, while logically a ``word'', may contain -parentheses or other characters that @value{GDBN} normally excludes from -its notion of a word. To permit word completion to work in this -situation, you may enclose words in @code{'} (single quote marks) in -@value{GDBN} commands. - -The most likely situation where you might need this is in typing the -name of a C@t{++} function. This is because C@t{++} allows function -overloading (multiple definitions of the same function, distinguished -by argument type). For example, when you want to set a breakpoint you -may need to distinguish whether you mean the version of @code{name} -that takes an @code{int} parameter, @code{name(int)}, or the version -that takes a @code{float} parameter, @code{name(float)}. To use the -word-completion facilities in this situation, type a single quote -@code{'} at the beginning of the function name. This alerts -@value{GDBN} that it may need to consider more information than usual -when you press @key{TAB} or @kbd{M-?} to request word completion: - -@example -(@value{GDBP}) b 'bubble( @kbd{M-?} -bubble(double,double) bubble(int,int) -(@value{GDBP}) b 'bubble( -@end example - -In some cases, @value{GDBN} can tell that completing a name requires using -quotes. When this happens, @value{GDBN} inserts the quote for you (while -completing as much as it can) if you do not type the quote in the first -place: - -@example -(@value{GDBP}) b bub @key{TAB} -@exdent @value{GDBN} alters your input line to the following, and rings a bell: -(@value{GDBP}) b 'bubble( -@end example - -@noindent -In general, @value{GDBN} can tell that a quote is needed (and inserts it) if -you have not yet started typing the argument list when you ask for -completion on an overloaded symbol. - -For more information about overloaded functions, see @ref{C plus plus -expressions, ,C@t{++} expressions}. You can use the command @code{set -overload-resolution off} to disable overload resolution; -see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}. - - -@node Help -@section Getting help -@cindex online documentation -@kindex help - -You can always ask @value{GDBN} itself for information on its commands, -using the command @code{help}. - -@table @code -@kindex h @r{(@code{help})} -@item help -@itemx h -You can use @code{help} (abbreviated @code{h}) with no arguments to -display a short list of named classes of commands: - -@smallexample -(@value{GDBP}) help -List of classes of commands: - -aliases -- Aliases of other commands -breakpoints -- Making program stop at certain points -data -- Examining data -files -- Specifying and examining files -internals -- Maintenance commands -obscure -- Obscure features -running -- Running the program -stack -- Examining the stack -status -- Status inquiries -support -- Support facilities -tracepoints -- Tracing of program execution without@* - stopping the program -user-defined -- User-defined commands - -Type "help" followed by a class name for a list of -commands in that class. -Type "help" followed by command name for full -documentation. -Command name abbreviations are allowed if unambiguous. -(@value{GDBP}) -@end smallexample -@c the above line break eliminates huge line overfull... - -@item help @var{class} -Using one of the general help classes as an argument, you can get a -list of the individual commands in that class. For example, here is the -help display for the class @code{status}: - -@smallexample -(@value{GDBP}) help status -Status inquiries. - -List of commands: - -@c Line break in "show" line falsifies real output, but needed -@c to fit in smallbook page size. -info -- Generic command for showing things - about the program being debugged -show -- Generic command for showing things - about the debugger - -Type "help" followed by command name for full -documentation. -Command name abbreviations are allowed if unambiguous. -(@value{GDBP}) -@end smallexample - -@item help @var{command} -With a command name as @code{help} argument, @value{GDBN} displays a -short paragraph on how to use that command. - -@kindex apropos -@item apropos @var{args} -The @code{apropos @var{args}} command searches through all of the @value{GDBN} -commands, and their documentation, for the regular expression specified in -@var{args}. It prints out all matches found. For example: - -@smallexample -apropos reload -@end smallexample - -@noindent -results in: - -@smallexample -@c @group -set symbol-reloading -- Set dynamic symbol table reloading - multiple times in one run -show symbol-reloading -- Show dynamic symbol table reloading - multiple times in one run -@c @end group -@end smallexample - -@kindex complete -@item complete @var{args} -The @code{complete @var{args}} command lists all the possible completions -for the beginning of a command. Use @var{args} to specify the beginning of the -command you want completed. For example: - -@smallexample -complete i -@end smallexample - -@noindent results in: - -@smallexample -@group -if -ignore -info -inspect -@end group -@end smallexample - -@noindent This is intended for use by @sc{gnu} Emacs. -@end table - -In addition to @code{help}, you can use the @value{GDBN} commands @code{info} -and @code{show} to inquire about the state of your program, or the state -of @value{GDBN} itself. Each command supports many topics of inquiry; this -manual introduces each of them in the appropriate context. The listings -under @code{info} and under @code{show} in the Index point to -all the sub-commands. @xref{Index}. - -@c @group -@table @code -@kindex info -@kindex i @r{(@code{info})} -@item info -This command (abbreviated @code{i}) is for describing the state of your -program. For example, you can list the arguments given to your program -with @code{info args}, list the registers currently in use with @code{info -registers}, or list the breakpoints you have set with @code{info breakpoints}. -You can get a complete list of the @code{info} sub-commands with -@w{@code{help info}}. - -@kindex set -@item set -You can assign the result of an expression to an environment variable with -@code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with -@code{set prompt $}. - -@kindex show -@item show -In contrast to @code{info}, @code{show} is for describing the state of -@value{GDBN} itself. -You can change most of the things you can @code{show}, by using the -related command @code{set}; for example, you can control what number -system is used for displays with @code{set radix}, or simply inquire -which is currently in use with @code{show radix}. - -@kindex info set -To display all the settable parameters and their current -values, you can use @code{show} with no arguments; you may also use -@code{info set}. Both commands produce the same display. -@c FIXME: "info set" violates the rule that "info" is for state of -@c FIXME...program. Ck w/ GNU: "info set" to be called something else, -@c FIXME...or change desc of rule---eg "state of prog and debugging session"? -@end table -@c @end group - -Here are three miscellaneous @code{show} subcommands, all of which are -exceptional in lacking corresponding @code{set} commands: - -@table @code -@kindex show version -@cindex version number -@item show version -Show what version of @value{GDBN} is running. You should include this -information in @value{GDBN} bug-reports. If multiple versions of -@value{GDBN} are in use at your site, you may need to determine which -version of @value{GDBN} you are running; as @value{GDBN} evolves, new -commands are introduced, and old ones may wither away. Also, many -system vendors ship variant versions of @value{GDBN}, and there are -variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well. -The version number is the same as the one announced when you start -@value{GDBN}. - -@kindex show copying -@item show copying -Display information about permission for copying @value{GDBN}. - -@kindex show warranty -@item show warranty -Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty, -if your version of @value{GDBN} comes with one. - -@end table - -@node Running -@chapter Running Programs Under @value{GDBN} - -When you run a program under @value{GDBN}, you must first generate -debugging information when you compile it. - -You may start @value{GDBN} with its arguments, if any, in an environment -of your choice. If you are doing native debugging, you may redirect -your program's input and output, debug an already running process, or -kill a child process. - -@menu -* Compilation:: Compiling for debugging -* Starting:: Starting your program -* Arguments:: Your program's arguments -* Environment:: Your program's environment - -* Working Directory:: Your program's working directory -* Input/Output:: Your program's input and output -* Attach:: Debugging an already-running process -* Kill Process:: Killing the child process - -* Threads:: Debugging programs with multiple threads -* Processes:: Debugging programs with multiple processes -@end menu - -@node Compilation -@section Compiling for debugging - -In order to debug a program effectively, you need to generate -debugging information when you compile it. This debugging information -is stored in the object file; it describes the data type of each -variable or function and the correspondence between source line numbers -and addresses in the executable code. - -To request debugging information, specify the @samp{-g} option when you run -the compiler. - -Many C compilers are unable to handle the @samp{-g} and @samp{-O} -options together. Using those compilers, you cannot generate optimized -executables containing debugging information. - -@value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or -without @samp{-O}, making it possible to debug optimized code. We -recommend that you @emph{always} use @samp{-g} whenever you compile a -program. You may think your program is correct, but there is no sense -in pushing your luck. - -@cindex optimized code, debugging -@cindex debugging optimized code -When you debug a program compiled with @samp{-g -O}, remember that the -optimizer is rearranging your code; the debugger shows you what is -really there. Do not be too surprised when the execution path does not -exactly match your source file! An extreme example: if you define a -variable, but never use it, @value{GDBN} never sees that -variable---because the compiler optimizes it out of existence. - -Some things do not work as well with @samp{-g -O} as with just -@samp{-g}, particularly on machines with instruction scheduling. If in -doubt, recompile with @samp{-g} alone, and if this fixes the problem, -please report it to us as a bug (including a test case!). - -Older versions of the @sc{gnu} C compiler permitted a variant option -@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this -format; if your @sc{gnu} C compiler has this option, do not use it. - -@need 2000 -@node Starting -@section Starting your program -@cindex starting -@cindex running - -@table @code -@kindex run -@kindex r @r{(@code{run})} -@item run -@itemx r -Use the @code{run} command to start your program under @value{GDBN}. -You must first specify the program name (except on VxWorks) with an -argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of -@value{GDBN}}), or by using the @code{file} or @code{exec-file} command -(@pxref{Files, ,Commands to specify files}). - -@end table - -If you are running your program in an execution environment that -supports processes, @code{run} creates an inferior process and makes -that process run your program. (In environments without processes, -@code{run} jumps to the start of your program.) - -The execution of a program is affected by certain information it -receives from its superior. @value{GDBN} provides ways to specify this -information, which you must do @emph{before} starting your program. (You -can change it after starting your program, but such changes only affect -your program the next time you start it.) This information may be -divided into four categories: - -@table @asis -@item The @emph{arguments.} -Specify the arguments to give your program as the arguments of the -@code{run} command. If a shell is available on your target, the shell -is used to pass the arguments, so that you may use normal conventions -(such as wildcard expansion or variable substitution) in describing -the arguments. -In Unix systems, you can control which shell is used with the -@code{SHELL} environment variable. -@xref{Arguments, ,Your program's arguments}. - -@item The @emph{environment.} -Your program normally inherits its environment from @value{GDBN}, but you can -use the @value{GDBN} commands @code{set environment} and @code{unset -environment} to change parts of the environment that affect -your program. @xref{Environment, ,Your program's environment}. - -@item The @emph{working directory.} -Your program inherits its working directory from @value{GDBN}. You can set -the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}. -@xref{Working Directory, ,Your program's working directory}. - -@item The @emph{standard input and output.} -Your program normally uses the same device for standard input and -standard output as @value{GDBN} is using. You can redirect input and output -in the @code{run} command line, or you can use the @code{tty} command to -set a different device for your program. -@xref{Input/Output, ,Your program's input and output}. - -@cindex pipes -@emph{Warning:} While input and output redirection work, you cannot use -pipes to pass the output of the program you are debugging to another -program; if you attempt this, @value{GDBN} is likely to wind up debugging the -wrong program. -@end table - -When you issue the @code{run} command, your program begins to execute -immediately. @xref{Stopping, ,Stopping and continuing}, for discussion -of how to arrange for your program to stop. Once your program has -stopped, you may call functions in your program, using the @code{print} -or @code{call} commands. @xref{Data, ,Examining Data}. - -If the modification time of your symbol file has changed since the last -time @value{GDBN} read its symbols, @value{GDBN} discards its symbol -table, and reads it again. When it does this, @value{GDBN} tries to retain -your current breakpoints. - -@node Arguments -@section Your program's arguments - -@cindex arguments (to your program) -The arguments to your program can be specified by the arguments of the -@code{run} command. -They are passed to a shell, which expands wildcard characters and -performs redirection of I/O, and thence to your program. Your -@code{SHELL} environment variable (if it exists) specifies what shell -@value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses -the default shell (@file{/bin/sh} on Unix). - -On non-Unix systems, the program is usually invoked directly by -@value{GDBN}, which emulates I/O redirection via the appropriate system -calls, and the wildcard characters are expanded by the startup code of -the program, not by the shell. - -@code{run} with no arguments uses the same arguments used by the previous -@code{run}, or those set by the @code{set args} command. - -@table @code -@kindex set args -@item set args -Specify the arguments to be used the next time your program is run. If -@code{set args} has no arguments, @code{run} executes your program -with no arguments. Once you have run your program with arguments, -using @code{set args} before the next @code{run} is the only way to run -it again without arguments. - -@kindex show args -@item show args -Show the arguments to give your program when it is started. -@end table - -@node Environment -@section Your program's environment - -@cindex environment (of your program) -The @dfn{environment} consists of a set of environment variables and -their values. Environment variables conventionally record such things as -your user name, your home directory, your terminal type, and your search -path for programs to run. Usually you set up environment variables with -the shell and they are inherited by all the other programs you run. When -debugging, it can be useful to try running your program with a modified -environment without having to start @value{GDBN} over again. - -@table @code -@kindex path -@item path @var{directory} -Add @var{directory} to the front of the @code{PATH} environment variable -(the search path for executables) that will be passed to your program. -The value of @code{PATH} used by @value{GDBN} does not change. -You may specify several directory names, separated by whitespace or by a -system-dependent separator character (@samp{:} on Unix, @samp{;} on -MS-DOS and MS-Windows). If @var{directory} is already in the path, it -is moved to the front, so it is searched sooner. - -You can use the string @samp{$cwd} to refer to whatever is the current -working directory at the time @value{GDBN} searches the path. If you -use @samp{.} instead, it refers to the directory where you executed the -@code{path} command. @value{GDBN} replaces @samp{.} in the -@var{directory} argument (with the current path) before adding -@var{directory} to the search path. -@c 'path' is explicitly nonrepeatable, but RMS points out it is silly to -@c document that, since repeating it would be a no-op. - -@kindex show paths -@item show paths -Display the list of search paths for executables (the @code{PATH} -environment variable). - -@kindex show environment -@item show environment @r{[}@var{varname}@r{]} -Print the value of environment variable @var{varname} to be given to -your program when it starts. If you do not supply @var{varname}, -print the names and values of all environment variables to be given to -your program. You can abbreviate @code{environment} as @code{env}. - -@kindex set environment -@item set environment @var{varname} @r{[}=@var{value}@r{]} -Set environment variable @var{varname} to @var{value}. The value -changes for your program only, not for @value{GDBN} itself. @var{value} may -be any string; the values of environment variables are just strings, and -any interpretation is supplied by your program itself. The @var{value} -parameter is optional; if it is eliminated, the variable is set to a -null value. -@c "any string" here does not include leading, trailing -@c blanks. Gnu asks: does anyone care? - -For example, this command: - -@example -set env USER = foo -@end example - -@noindent -tells the debugged program, when subsequently run, that its user is named -@samp{foo}. (The spaces around @samp{=} are used for clarity here; they -are not actually required.) - -@kindex unset environment -@item unset environment @var{varname} -Remove variable @var{varname} from the environment to be passed to your -program. This is different from @samp{set env @var{varname} =}; -@code{unset environment} removes the variable from the environment, -rather than assigning it an empty value. -@end table - -@emph{Warning:} On Unix systems, @value{GDBN} runs your program using -the shell indicated -by your @code{SHELL} environment variable if it exists (or -@code{/bin/sh} if not). If your @code{SHELL} variable names a shell -that runs an initialization file---such as @file{.cshrc} for C-shell, or -@file{.bashrc} for BASH---any variables you set in that file affect -your program. You may wish to move setting of environment variables to -files that are only run when you sign on, such as @file{.login} or -@file{.profile}. - -@node Working Directory -@section Your program's working directory - -@cindex working directory (of your program) -Each time you start your program with @code{run}, it inherits its -working directory from the current working directory of @value{GDBN}. -The @value{GDBN} working directory is initially whatever it inherited -from its parent process (typically the shell), but you can specify a new -working directory in @value{GDBN} with the @code{cd} command. - -The @value{GDBN} working directory also serves as a default for the commands -that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to -specify files}. - -@table @code -@kindex cd -@item cd @var{directory} -Set the @value{GDBN} working directory to @var{directory}. - -@kindex pwd -@item pwd -Print the @value{GDBN} working directory. -@end table - -@node Input/Output -@section Your program's input and output - -@cindex redirection -@cindex i/o -@cindex terminal -By default, the program you run under @value{GDBN} does input and output to -the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal -to its own terminal modes to interact with you, but it records the terminal -modes your program was using and switches back to them when you continue -running your program. - -@table @code -@kindex info terminal -@item info terminal -Displays information recorded by @value{GDBN} about the terminal modes your -program is using. -@end table - -You can redirect your program's input and/or output using shell -redirection with the @code{run} command. For example, - -@example -run > outfile -@end example - -@noindent -starts your program, diverting its output to the file @file{outfile}. - -@kindex tty -@cindex controlling terminal -Another way to specify where your program should do input and output is -with the @code{tty} command. This command accepts a file name as -argument, and causes this file to be the default for future @code{run} -commands. It also resets the controlling terminal for the child -process, for future @code{run} commands. For example, - -@example -tty /dev/ttyb -@end example - -@noindent -directs that processes started with subsequent @code{run} commands -default to do input and output on the terminal @file{/dev/ttyb} and have -that as their controlling terminal. - -An explicit redirection in @code{run} overrides the @code{tty} command's -effect on the input/output device, but not its effect on the controlling -terminal. - -When you use the @code{tty} command or redirect input in the @code{run} -command, only the input @emph{for your program} is affected. The input -for @value{GDBN} still comes from your terminal. - -@node Attach -@section Debugging an already-running process -@kindex attach -@cindex attach - -@table @code -@item attach @var{process-id} -This command attaches to a running process---one that was started -outside @value{GDBN}. (@code{info files} shows your active -targets.) The command takes as argument a process ID. The usual way to -find out the process-id of a Unix process is with the @code{ps} utility, -or with the @samp{jobs -l} shell command. - -@code{attach} does not repeat if you press @key{RET} a second time after -executing the command. -@end table - -To use @code{attach}, your program must be running in an environment -which supports processes; for example, @code{attach} does not work for -programs on bare-board targets that lack an operating system. You must -also have permission to send the process a signal. - -When you use @code{attach}, the debugger finds the program running in -the process first by looking in the current working directory, then (if -the program is not found) by using the source file search path -(@pxref{Source Path, ,Specifying source directories}). You can also use -the @code{file} command to load the program. @xref{Files, ,Commands to -Specify Files}. - -The first thing @value{GDBN} does after arranging to debug the specified -process is to stop it. You can examine and modify an attached process -with all the @value{GDBN} commands that are ordinarily available when -you start processes with @code{run}. You can insert breakpoints; you -can step and continue; you can modify storage. If you would rather the -process continue running, you may use the @code{continue} command after -attaching @value{GDBN} to the process. - -@table @code -@kindex detach -@item detach -When you have finished debugging the attached process, you can use the -@code{detach} command to release it from @value{GDBN} control. Detaching -the process continues its execution. After the @code{detach} command, -that process and @value{GDBN} become completely independent once more, and you -are ready to @code{attach} another process or start one with @code{run}. -@code{detach} does not repeat if you press @key{RET} again after -executing the command. -@end table - -If you exit @value{GDBN} or use the @code{run} command while you have an -attached process, you kill that process. By default, @value{GDBN} asks -for confirmation if you try to do either of these things; you can -control whether or not you need to confirm by using the @code{set -confirm} command (@pxref{Messages/Warnings, ,Optional warnings and -messages}). - -@node Kill Process -@section Killing the child process - -@table @code -@kindex kill -@item kill -Kill the child process in which your program is running under @value{GDBN}. -@end table - -This command is useful if you wish to debug a core dump instead of a -running process. @value{GDBN} ignores any core dump file while your program -is running. - -On some operating systems, a program cannot be executed outside @value{GDBN} -while you have breakpoints set on it inside @value{GDBN}. You can use the -@code{kill} command in this situation to permit running your program -outside the debugger. - -The @code{kill} command is also useful if you wish to recompile and -relink your program, since on many systems it is impossible to modify an -executable file while it is running in a process. In this case, when you -next type @code{run}, @value{GDBN} notices that the file has changed, and -reads the symbol table again (while trying to preserve your current -breakpoint settings). - -@node Threads -@section Debugging programs with multiple threads - -@cindex threads of execution -@cindex multiple threads -@cindex switching threads -In some operating systems, such as HP-UX and Solaris, a single program -may have more than one @dfn{thread} of execution. The precise semantics -of threads differ from one operating system to another, but in general -the threads of a single program are akin to multiple processes---except -that they share one address space (that is, they can all examine and -modify the same variables). On the other hand, each thread has its own -registers and execution stack, and perhaps private memory. - -@value{GDBN} provides these facilities for debugging multi-thread -programs: - -@itemize @bullet -@item automatic notification of new threads -@item @samp{thread @var{threadno}}, a command to switch among threads -@item @samp{info threads}, a command to inquire about existing threads -@item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}}, -a command to apply a command to a list of threads -@item thread-specific breakpoints -@end itemize - -@quotation -@emph{Warning:} These facilities are not yet available on every -@value{GDBN} configuration where the operating system supports threads. -If your @value{GDBN} does not support threads, these commands have no -effect. For example, a system without thread support shows no output -from @samp{info threads}, and always rejects the @code{thread} command, -like this: - -@smallexample -(@value{GDBP}) info threads -(@value{GDBP}) thread 1 -Thread ID 1 not known. Use the "info threads" command to -see the IDs of currently known threads. -@end smallexample -@c FIXME to implementors: how hard would it be to say "sorry, this GDB -@c doesn't support threads"? -@end quotation - -@cindex focus of debugging -@cindex current thread -The @value{GDBN} thread debugging facility allows you to observe all -threads while your program runs---but whenever @value{GDBN} takes -control, one thread in particular is always the focus of debugging. -This thread is called the @dfn{current thread}. Debugging commands show -program information from the perspective of the current thread. - -@cindex @code{New} @var{systag} message -@cindex thread identifier (system) -@c FIXME-implementors!! It would be more helpful if the [New...] message -@c included GDB's numeric thread handle, so you could just go to that -@c thread without first checking `info threads'. -Whenever @value{GDBN} detects a new thread in your program, it displays -the target system's identification for the thread with a message in the -form @samp{[New @var{systag}]}. @var{systag} is a thread identifier -whose form varies depending on the particular system. For example, on -LynxOS, you might see - -@example -[New process 35 thread 27] -@end example - -@noindent -when @value{GDBN} notices a new thread. In contrast, on an SGI system, -the @var{systag} is simply something like @samp{process 368}, with no -further qualifier. - -@c FIXME!! (1) Does the [New...] message appear even for the very first -@c thread of a program, or does it only appear for the -@c second---i.e.@: when it becomes obvious we have a multithread -@c program? -@c (2) *Is* there necessarily a first thread always? Or do some -@c multithread systems permit starting a program with multiple -@c threads ab initio? - -@cindex thread number -@cindex thread identifier (GDB) -For debugging purposes, @value{GDBN} associates its own thread -number---always a single integer---with each thread in your program. - -@table @code -@kindex info threads -@item info threads -Display a summary of all threads currently in your -program. @value{GDBN} displays for each thread (in this order): - -@enumerate -@item the thread number assigned by @value{GDBN} - -@item the target system's thread identifier (@var{systag}) - -@item the current stack frame summary for that thread -@end enumerate - -@noindent -An asterisk @samp{*} to the left of the @value{GDBN} thread number -indicates the current thread. - -For example, -@end table -@c end table here to get a little more width for example - -@smallexample -(@value{GDBP}) info threads - 3 process 35 thread 27 0x34e5 in sigpause () - 2 process 35 thread 23 0x34e5 in sigpause () -* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8) - at threadtest.c:68 -@end smallexample - -On HP-UX systems: - -@cindex thread number -@cindex thread identifier (GDB) -For debugging purposes, @value{GDBN} associates its own thread -number---a small integer assigned in thread-creation order---with each -thread in your program. - -@cindex @code{New} @var{systag} message, on HP-UX -@cindex thread identifier (system), on HP-UX -@c FIXME-implementors!! It would be more helpful if the [New...] message -@c included GDB's numeric thread handle, so you could just go to that -@c thread without first checking `info threads'. -Whenever @value{GDBN} detects a new thread in your program, it displays -both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the -form @samp{[New @var{systag}]}. @var{systag} is a thread identifier -whose form varies depending on the particular system. For example, on -HP-UX, you see - -@example -[New thread 2 (system thread 26594)] -@end example - -@noindent -when @value{GDBN} notices a new thread. - -@table @code -@kindex info threads -@item info threads -Display a summary of all threads currently in your -program. @value{GDBN} displays for each thread (in this order): - -@enumerate -@item the thread number assigned by @value{GDBN} - -@item the target system's thread identifier (@var{systag}) - -@item the current stack frame summary for that thread -@end enumerate - -@noindent -An asterisk @samp{*} to the left of the @value{GDBN} thread number -indicates the current thread. - -For example, -@end table -@c end table here to get a little more width for example - -@example -(@value{GDBP}) info threads - * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@* - at quicksort.c:137 - 2 system thread 26606 0x7b0030d8 in __ksleep () \@* - from /usr/lib/libc.2 - 1 system thread 27905 0x7b003498 in _brk () \@* - from /usr/lib/libc.2 -@end example - -@table @code -@kindex thread @var{threadno} -@item thread @var{threadno} -Make thread number @var{threadno} the current thread. The command -argument @var{threadno} is the internal @value{GDBN} thread number, as -shown in the first field of the @samp{info threads} display. -@value{GDBN} responds by displaying the system identifier of the thread -you selected, and its current stack frame summary: - -@smallexample -@c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one -(@value{GDBP}) thread 2 -[Switching to process 35 thread 23] -0x34e5 in sigpause () -@end smallexample - -@noindent -As with the @samp{[New @dots{}]} message, the form of the text after -@samp{Switching to} depends on your system's conventions for identifying -threads. - -@kindex thread apply -@item thread apply [@var{threadno}] [@var{all}] @var{args} -The @code{thread apply} command allows you to apply a command to one or -more threads. Specify the numbers of the threads that you want affected -with the command argument @var{threadno}. @var{threadno} is the internal -@value{GDBN} thread number, as shown in the first field of the @samp{info -threads} display. To apply a command to all threads, use -@code{thread apply all} @var{args}. -@end table - -@cindex automatic thread selection -@cindex switching threads automatically -@cindex threads, automatic switching -Whenever @value{GDBN} stops your program, due to a breakpoint or a -signal, it automatically selects the thread where that breakpoint or -signal happened. @value{GDBN} alerts you to the context switch with a -message of the form @samp{[Switching to @var{systag}]} to identify the -thread. - -@xref{Thread Stops,,Stopping and starting multi-thread programs}, for -more information about how @value{GDBN} behaves when you stop and start -programs with multiple threads. - -@xref{Set Watchpoints,,Setting watchpoints}, for information about -watchpoints in programs with multiple threads. - -@node Processes -@section Debugging programs with multiple processes - -@cindex fork, debugging programs which call -@cindex multiple processes -@cindex processes, multiple -On most systems, @value{GDBN} has no special support for debugging -programs which create additional processes using the @code{fork} -function. When a program forks, @value{GDBN} will continue to debug the -parent process and the child process will run unimpeded. If you have -set a breakpoint in any code which the child then executes, the child -will get a @code{SIGTRAP} signal which (unless it catches the signal) -will cause it to terminate. - -However, if you want to debug the child process there is a workaround -which isn't too painful. Put a call to @code{sleep} in the code which -the child process executes after the fork. It may be useful to sleep -only if a certain environment variable is set, or a certain file exists, -so that the delay need not occur when you don't want to run @value{GDBN} -on the child. While the child is sleeping, use the @code{ps} program to -get its process ID. Then tell @value{GDBN} (a new invocation of -@value{GDBN} if you are also debugging the parent process) to attach to -the child process (@pxref{Attach}). From that point on you can debug -the child process just like any other process which you attached to. - -On HP-UX (11.x and later only?), @value{GDBN} provides support for -debugging programs that create additional processes using the -@code{fork} or @code{vfork} function. - -By default, when a program forks, @value{GDBN} will continue to debug -the parent process and the child process will run unimpeded. - -If you want to follow the child process instead of the parent process, -use the command @w{@code{set follow-fork-mode}}. - -@table @code -@kindex set follow-fork-mode -@item set follow-fork-mode @var{mode} -Set the debugger response to a program call of @code{fork} or -@code{vfork}. A call to @code{fork} or @code{vfork} creates a new -process. The @var{mode} can be: - -@table @code -@item parent -The original process is debugged after a fork. The child process runs -unimpeded. This is the default. - -@item child -The new process is debugged after a fork. The parent process runs -unimpeded. - -@item ask -The debugger will ask for one of the above choices. -@end table - -@item show follow-fork-mode -Display the current debugger response to a @code{fork} or @code{vfork} call. -@end table - -If you ask to debug a child process and a @code{vfork} is followed by an -@code{exec}, @value{GDBN} executes the new target up to the first -breakpoint in the new target. If you have a breakpoint set on -@code{main} in your original program, the breakpoint will also be set on -the child process's @code{main}. - -When a child process is spawned by @code{vfork}, you cannot debug the -child or parent until an @code{exec} call completes. - -If you issue a @code{run} command to @value{GDBN} after an @code{exec} -call executes, the new target restarts. To restart the parent process, -use the @code{file} command with the parent executable name as its -argument. - -You can use the @code{catch} command to make @value{GDBN} stop whenever -a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set -Catchpoints, ,Setting catchpoints}. - -@node Stopping -@chapter Stopping and Continuing - -The principal purposes of using a debugger are so that you can stop your -program before it terminates; or so that, if your program runs into -trouble, you can investigate and find out why. - -Inside @value{GDBN}, your program may stop for any of several reasons, -such as a signal, a breakpoint, or reaching a new line after a -@value{GDBN} command such as @code{step}. You may then examine and -change variables, set new breakpoints or remove old ones, and then -continue execution. Usually, the messages shown by @value{GDBN} provide -ample explanation of the status of your program---but you can also -explicitly request this information at any time. - -@table @code -@kindex info program -@item info program -Display information about the status of your program: whether it is -running or not, what process it is, and why it stopped. -@end table - -@menu -* Breakpoints:: Breakpoints, watchpoints, and catchpoints -* Continuing and Stepping:: Resuming execution -* Signals:: Signals -* Thread Stops:: Stopping and starting multi-thread programs -@end menu - -@node Breakpoints -@section Breakpoints, watchpoints, and catchpoints - -@cindex breakpoints -A @dfn{breakpoint} makes your program stop whenever a certain point in -the program is reached. For each breakpoint, you can add conditions to -control in finer detail whether your program stops. You can set -breakpoints with the @code{break} command and its variants (@pxref{Set -Breaks, ,Setting breakpoints}), to specify the place where your program -should stop by line number, function name or exact address in the -program. - -In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set -breakpoints in shared libraries before the executable is run. There is -a minor limitation on HP-UX systems: you must wait until the executable -is run in order to set breakpoints in shared library routines that are -not called directly by the program (for example, routines that are -arguments in a @code{pthread_create} call). - -@cindex watchpoints -@cindex memory tracing -@cindex breakpoint on memory address -@cindex breakpoint on variable modification -A @dfn{watchpoint} is a special breakpoint that stops your program -when the value of an expression changes. You must use a different -command to set watchpoints (@pxref{Set Watchpoints, ,Setting -watchpoints}), but aside from that, you can manage a watchpoint like -any other breakpoint: you enable, disable, and delete both breakpoints -and watchpoints using the same commands. - -You can arrange to have values from your program displayed automatically -whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,, -Automatic display}. - -@cindex catchpoints -@cindex breakpoint on events -A @dfn{catchpoint} is another special breakpoint that stops your program -when a certain kind of event occurs, such as the throwing of a C@t{++} -exception or the loading of a library. As with watchpoints, you use a -different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting -catchpoints}), but aside from that, you can manage a catchpoint like any -other breakpoint. (To stop when your program receives a signal, use the -@code{handle} command; see @ref{Signals, ,Signals}.) - -@cindex breakpoint numbers -@cindex numbers for breakpoints -@value{GDBN} assigns a number to each breakpoint, watchpoint, or -catchpoint when you create it; these numbers are successive integers -starting with one. In many of the commands for controlling various -features of breakpoints you use the breakpoint number to say which -breakpoint you want to change. Each breakpoint may be @dfn{enabled} or -@dfn{disabled}; if disabled, it has no effect on your program until you -enable it again. - -@cindex breakpoint ranges -@cindex ranges of breakpoints -Some @value{GDBN} commands accept a range of breakpoints on which to -operate. A breakpoint range is either a single breakpoint number, like -@samp{5}, or two such numbers, in increasing order, separated by a -hyphen, like @samp{5-7}. When a breakpoint range is given to a command, -all breakpoint in that range are operated on. - -@menu -* Set Breaks:: Setting breakpoints -* Set Watchpoints:: Setting watchpoints -* Set Catchpoints:: Setting catchpoints -* Delete Breaks:: Deleting breakpoints -* Disabling:: Disabling breakpoints -* Conditions:: Break conditions -* Break Commands:: Breakpoint command lists -* Breakpoint Menus:: Breakpoint menus -* Error in Breakpoints:: ``Cannot insert breakpoints'' -@end menu - -@node Set Breaks -@subsection Setting breakpoints - -@c FIXME LMB what does GDB do if no code on line of breakpt? -@c consider in particular declaration with/without initialization. -@c -@c FIXME 2 is there stuff on this already? break at fun start, already init? - -@kindex break -@kindex b @r{(@code{break})} -@vindex $bpnum@r{, convenience variable} -@cindex latest breakpoint -Breakpoints are set with the @code{break} command (abbreviated -@code{b}). The debugger convenience variable @samp{$bpnum} records the -number of the breakpoint you've set most recently; see @ref{Convenience -Vars,, Convenience variables}, for a discussion of what you can do with -convenience variables. - -You have several ways to say where the breakpoint should go. - -@table @code -@item break @var{function} -Set a breakpoint at entry to function @var{function}. -When using source languages that permit overloading of symbols, such as -C@t{++}, @var{function} may refer to more than one possible place to break. -@xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation. - -@item break +@var{offset} -@itemx break -@var{offset} -Set a breakpoint some number of lines forward or back from the position -at which execution stopped in the currently selected @dfn{stack frame}. -(@xref{Frames, ,Frames}, for a description of stack frames.) - -@item break @var{linenum} -Set a breakpoint at line @var{linenum} in the current source file. -The current source file is the last file whose source text was printed. -The breakpoint will stop your program just before it executes any of the -code on that line. - -@item break @var{filename}:@var{linenum} -Set a breakpoint at line @var{linenum} in source file @var{filename}. - -@item break @var{filename}:@var{function} -Set a breakpoint at entry to function @var{function} found in file -@var{filename}. Specifying a file name as well as a function name is -superfluous except when multiple files contain similarly named -functions. - -@item break *@var{address} -Set a breakpoint at address @var{address}. You can use this to set -breakpoints in parts of your program which do not have debugging -information or source files. - -@item break -When called without any arguments, @code{break} sets a breakpoint at -the next instruction to be executed in the selected stack frame -(@pxref{Stack, ,Examining the Stack}). In any selected frame but the -innermost, this makes your program stop as soon as control -returns to that frame. This is similar to the effect of a -@code{finish} command in the frame inside the selected frame---except -that @code{finish} does not leave an active breakpoint. If you use -@code{break} without an argument in the innermost frame, @value{GDBN} stops -the next time it reaches the current location; this may be useful -inside loops. - -@value{GDBN} normally ignores breakpoints when it resumes execution, until at -least one instruction has been executed. If it did not do this, you -would be unable to proceed past a breakpoint without first disabling the -breakpoint. This rule applies whether or not the breakpoint already -existed when your program stopped. - -@item break @dots{} if @var{cond} -Set a breakpoint with condition @var{cond}; evaluate the expression -@var{cond} each time the breakpoint is reached, and stop only if the -value is nonzero---that is, if @var{cond} evaluates as true. -@samp{@dots{}} stands for one of the possible arguments described -above (or no argument) specifying where to break. @xref{Conditions, -,Break conditions}, for more information on breakpoint conditions. - -@kindex tbreak -@item tbreak @var{args} -Set a breakpoint enabled only for one stop. @var{args} are the -same as for the @code{break} command, and the breakpoint is set in the same -way, but the breakpoint is automatically deleted after the first time your -program stops there. @xref{Disabling, ,Disabling breakpoints}. - -@kindex hbreak -@item hbreak @var{args} -Set a hardware-assisted breakpoint. @var{args} are the same as for the -@code{break} command and the breakpoint is set in the same way, but the -breakpoint requires hardware support and some target hardware may not -have this support. The main purpose of this is EPROM/ROM code -debugging, so you can set a breakpoint at an instruction without -changing the instruction. This can be used with the new trap-generation -provided by SPARClite DSU and some x86-based targets. These targets -will generate traps when a program accesses some data or instruction -address that is assigned to the debug registers. However the hardware -breakpoint registers can take a limited number of breakpoints. For -example, on the DSU, only two data breakpoints can be set at a time, and -@value{GDBN} will reject this command if more than two are used. Delete -or disable unused hardware breakpoints before setting new ones -(@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}. - -@kindex thbreak -@item thbreak @var{args} -Set a hardware-assisted breakpoint enabled only for one stop. @var{args} -are the same as for the @code{hbreak} command and the breakpoint is set in -the same way. However, like the @code{tbreak} command, -the breakpoint is automatically deleted after the -first time your program stops there. Also, like the @code{hbreak} -command, the breakpoint requires hardware support and some target hardware -may not have this support. @xref{Disabling, ,Disabling breakpoints}. -See also @ref{Conditions, ,Break conditions}. - -@kindex rbreak -@cindex regular expression -@item rbreak @var{regex} -Set breakpoints on all functions matching the regular expression -@var{regex}. This command sets an unconditional breakpoint on all -matches, printing a list of all breakpoints it set. Once these -breakpoints are set, they are treated just like the breakpoints set with -the @code{break} command. You can delete them, disable them, or make -them conditional the same way as any other breakpoint. - -The syntax of the regular expression is the standard one used with tools -like @file{grep}. Note that this is different from the syntax used by -shells, so for instance @code{foo*} matches all functions that include -an @code{fo} followed by zero or more @code{o}s. There is an implicit -@code{.*} leading and trailing the regular expression you supply, so to -match only functions that begin with @code{foo}, use @code{^foo}. - -When debugging C@t{++} programs, @code{rbreak} is useful for setting -breakpoints on overloaded functions that are not members of any special -classes. - -@kindex info breakpoints -@cindex @code{$_} and @code{info breakpoints} -@item info breakpoints @r{[}@var{n}@r{]} -@itemx info break @r{[}@var{n}@r{]} -@itemx info watchpoints @r{[}@var{n}@r{]} -Print a table of all breakpoints, watchpoints, and catchpoints set and -not deleted, with the following columns for each breakpoint: - -@table @emph -@item Breakpoint Numbers -@item Type -Breakpoint, watchpoint, or catchpoint. -@item Disposition -Whether the breakpoint is marked to be disabled or deleted when hit. -@item Enabled or Disabled -Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints -that are not enabled. -@item Address -Where the breakpoint is in your program, as a memory address. -@item What -Where the breakpoint is in the source for your program, as a file and -line number. -@end table - -@noindent -If a breakpoint is conditional, @code{info break} shows the condition on -the line following the affected breakpoint; breakpoint commands, if any, -are listed after that. - -@noindent -@code{info break} with a breakpoint -number @var{n} as argument lists only that breakpoint. The -convenience variable @code{$_} and the default examining-address for -the @code{x} command are set to the address of the last breakpoint -listed (@pxref{Memory, ,Examining memory}). - -@noindent -@code{info break} displays a count of the number of times the breakpoint -has been hit. This is especially useful in conjunction with the -@code{ignore} command. You can ignore a large number of breakpoint -hits, look at the breakpoint info to see how many times the breakpoint -was hit, and then run again, ignoring one less than that number. This -will get you quickly to the last hit of that breakpoint. -@end table - -@value{GDBN} allows you to set any number of breakpoints at the same place in -your program. There is nothing silly or meaningless about this. When -the breakpoints are conditional, this is even useful -(@pxref{Conditions, ,Break conditions}). - -@cindex negative breakpoint numbers -@cindex internal @value{GDBN} breakpoints -@value{GDBN} itself sometimes sets breakpoints in your program for -special purposes, such as proper handling of @code{longjmp} (in C -programs). These internal breakpoints are assigned negative numbers, -starting with @code{-1}; @samp{info breakpoints} does not display them. -You can see these breakpoints with the @value{GDBN} maintenance command -@samp{maint info breakpoints} (@pxref{maint info breakpoints}). - - -@node Set Watchpoints -@subsection Setting watchpoints - -@cindex setting watchpoints -@cindex software watchpoints -@cindex hardware watchpoints -You can use a watchpoint to stop execution whenever the value of an -expression changes, without having to predict a particular place where -this may happen. - -Depending on your system, watchpoints may be implemented in software or -hardware. @value{GDBN} does software watchpointing by single-stepping your -program and testing the variable's value each time, which is hundreds of -times slower than normal execution. (But this may still be worth it, to -catch errors where you have no clue what part of your program is the -culprit.) - -On some systems, such as HP-UX, Linux and some other x86-based targets, -@value{GDBN} includes support for -hardware watchpoints, which do not slow down the running of your -program. - -@table @code -@kindex watch -@item watch @var{expr} -Set a watchpoint for an expression. @value{GDBN} will break when @var{expr} -is written into by the program and its value changes. - -@kindex rwatch -@item rwatch @var{expr} -Set a watchpoint that will break when watch @var{expr} is read by the program. - -@kindex awatch -@item awatch @var{expr} -Set a watchpoint that will break when @var{expr} is either read or written into -by the program. - -@kindex info watchpoints -@item info watchpoints -This command prints a list of watchpoints, breakpoints, and catchpoints; -it is the same as @code{info break}. -@end table - -@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware -watchpoints execute very quickly, and the debugger reports a change in -value at the exact instruction where the change occurs. If @value{GDBN} -cannot set a hardware watchpoint, it sets a software watchpoint, which -executes more slowly and reports the change in value at the next -statement, not the instruction, after the change occurs. - -When you issue the @code{watch} command, @value{GDBN} reports - -@example -Hardware watchpoint @var{num}: @var{expr} -@end example - -@noindent -if it was able to set a hardware watchpoint. - -Currently, the @code{awatch} and @code{rwatch} commands can only set -hardware watchpoints, because accesses to data that don't change the -value of the watched expression cannot be detected without examining -every instruction as it is being executed, and @value{GDBN} does not do -that currently. If @value{GDBN} finds that it is unable to set a -hardware breakpoint with the @code{awatch} or @code{rwatch} command, it -will print a message like this: - -@smallexample -Expression cannot be implemented with read/access watchpoint. -@end smallexample - -Sometimes, @value{GDBN} cannot set a hardware watchpoint because the -data type of the watched expression is wider than what a hardware -watchpoint on the target machine can handle. For example, some systems -can only watch regions that are up to 4 bytes wide; on such systems you -cannot set hardware watchpoints for an expression that yields a -double-precision floating-point number (which is typically 8 bytes -wide). As a work-around, it might be possible to break the large region -into a series of smaller ones and watch them with separate watchpoints. - -If you set too many hardware watchpoints, @value{GDBN} might be unable -to insert all of them when you resume the execution of your program. -Since the precise number of active watchpoints is unknown until such -time as the program is about to be resumed, @value{GDBN} might not be -able to warn you about this when you set the watchpoints, and the -warning will be printed only when the program is resumed: - -@smallexample -Hardware watchpoint @var{num}: Could not insert watchpoint -@end smallexample - -@noindent -If this happens, delete or disable some of the watchpoints. - -The SPARClite DSU will generate traps when a program accesses some data -or instruction address that is assigned to the debug registers. For the -data addresses, DSU facilitates the @code{watch} command. However the -hardware breakpoint registers can only take two data watchpoints, and -both watchpoints must be the same kind. For example, you can set two -watchpoints with @code{watch} commands, two with @code{rwatch} commands, -@strong{or} two with @code{awatch} commands, but you cannot set one -watchpoint with one command and the other with a different command. -@value{GDBN} will reject the command if you try to mix watchpoints. -Delete or disable unused watchpoint commands before setting new ones. - -If you call a function interactively using @code{print} or @code{call}, -any watchpoints you have set will be inactive until @value{GDBN} reaches another -kind of breakpoint or the call completes. - -@value{GDBN} automatically deletes watchpoints that watch local -(automatic) variables, or expressions that involve such variables, when -they go out of scope, that is, when the execution leaves the block in -which these variables were defined. In particular, when the program -being debugged terminates, @emph{all} local variables go out of scope, -and so only watchpoints that watch global variables remain set. If you -rerun the program, you will need to set all such watchpoints again. One -way of doing that would be to set a code breakpoint at the entry to the -@code{main} function and when it breaks, set all the watchpoints. - -@quotation -@cindex watchpoints and threads -@cindex threads and watchpoints -@emph{Warning:} In multi-thread programs, watchpoints have only limited -usefulness. With the current watchpoint implementation, @value{GDBN} -can only watch the value of an expression @emph{in a single thread}. If -you are confident that the expression can only change due to the current -thread's activity (and if you are also confident that no other thread -can become current), then you can use watchpoints as usual. However, -@value{GDBN} may not notice when a non-current thread's activity changes -the expression. - -@c FIXME: this is almost identical to the previous paragraph. -@emph{HP-UX Warning:} In multi-thread programs, software watchpoints -have only limited usefulness. If @value{GDBN} creates a software -watchpoint, it can only watch the value of an expression @emph{in a -single thread}. If you are confident that the expression can only -change due to the current thread's activity (and if you are also -confident that no other thread can become current), then you can use -software watchpoints as usual. However, @value{GDBN} may not notice -when a non-current thread's activity changes the expression. (Hardware -watchpoints, in contrast, watch an expression in all threads.) -@end quotation - -@node Set Catchpoints -@subsection Setting catchpoints -@cindex catchpoints, setting -@cindex exception handlers -@cindex event handling - -You can use @dfn{catchpoints} to cause the debugger to stop for certain -kinds of program events, such as C@t{++} exceptions or the loading of a -shared library. Use the @code{catch} command to set a catchpoint. - -@table @code -@kindex catch -@item catch @var{event} -Stop when @var{event} occurs. @var{event} can be any of the following: -@table @code -@item throw -@kindex catch throw -The throwing of a C@t{++} exception. - -@item catch -@kindex catch catch -The catching of a C@t{++} exception. - -@item exec -@kindex catch exec -A call to @code{exec}. This is currently only available for HP-UX. - -@item fork -@kindex catch fork -A call to @code{fork}. This is currently only available for HP-UX. - -@item vfork -@kindex catch vfork -A call to @code{vfork}. This is currently only available for HP-UX. - -@item load -@itemx load @var{libname} -@kindex catch load -The dynamic loading of any shared library, or the loading of the library -@var{libname}. This is currently only available for HP-UX. - -@item unload -@itemx unload @var{libname} -@kindex catch unload -The unloading of any dynamically loaded shared library, or the unloading -of the library @var{libname}. This is currently only available for HP-UX. -@end table - -@item tcatch @var{event} -Set a catchpoint that is enabled only for one stop. The catchpoint is -automatically deleted after the first time the event is caught. - -@end table - -Use the @code{info break} command to list the current catchpoints. - -There are currently some limitations to C@t{++} exception handling -(@code{catch throw} and @code{catch catch}) in @value{GDBN}: - -@itemize @bullet -@item -If you call a function interactively, @value{GDBN} normally returns -control to you when the function has finished executing. If the call -raises an exception, however, the call may bypass the mechanism that -returns control to you and cause your program either to abort or to -simply continue running until it hits a breakpoint, catches a signal -that @value{GDBN} is listening for, or exits. This is the case even if -you set a catchpoint for the exception; catchpoints on exceptions are -disabled within interactive calls. - -@item -You cannot raise an exception interactively. - -@item -You cannot install an exception handler interactively. -@end itemize - -@cindex raise exceptions -Sometimes @code{catch} is not the best way to debug exception handling: -if you need to know exactly where an exception is raised, it is better to -stop @emph{before} the exception handler is called, since that way you -can see the stack before any unwinding takes place. If you set a -breakpoint in an exception handler instead, it may not be easy to find -out where the exception was raised. - -To stop just before an exception handler is called, you need some -knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are -raised by calling a library function named @code{__raise_exception} -which has the following ANSI C interface: - -@example - /* @var{addr} is where the exception identifier is stored. - @var{id} is the exception identifier. */ - void __raise_exception (void **addr, void *id); -@end example - -@noindent -To make the debugger catch all exceptions before any stack -unwinding takes place, set a breakpoint on @code{__raise_exception} -(@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}). - -With a conditional breakpoint (@pxref{Conditions, ,Break conditions}) -that depends on the value of @var{id}, you can stop your program when -a specific exception is raised. You can use multiple conditional -breakpoints to stop your program when any of a number of exceptions are -raised. - - -@node Delete Breaks -@subsection Deleting breakpoints - -@cindex clearing breakpoints, watchpoints, catchpoints -@cindex deleting breakpoints, watchpoints, catchpoints -It is often necessary to eliminate a breakpoint, watchpoint, or -catchpoint once it has done its job and you no longer want your program -to stop there. This is called @dfn{deleting} the breakpoint. A -breakpoint that has been deleted no longer exists; it is forgotten. - -With the @code{clear} command you can delete breakpoints according to -where they are in your program. With the @code{delete} command you can -delete individual breakpoints, watchpoints, or catchpoints by specifying -their breakpoint numbers. - -It is not necessary to delete a breakpoint to proceed past it. @value{GDBN} -automatically ignores breakpoints on the first instruction to be executed -when you continue execution without changing the execution address. - -@table @code -@kindex clear -@item clear -Delete any breakpoints at the next instruction to be executed in the -selected stack frame (@pxref{Selection, ,Selecting a frame}). When -the innermost frame is selected, this is a good way to delete a -breakpoint where your program just stopped. - -@item clear @var{function} -@itemx clear @var{filename}:@var{function} -Delete any breakpoints set at entry to the function @var{function}. - -@item clear @var{linenum} -@itemx clear @var{filename}:@var{linenum} -Delete any breakpoints set at or within the code of the specified line. - -@cindex delete breakpoints -@kindex delete -@kindex d @r{(@code{delete})} -@item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} -Delete the breakpoints, watchpoints, or catchpoints of the breakpoint -ranges specified as arguments. If no argument is specified, delete all -breakpoints (@value{GDBN} asks confirmation, unless you have @code{set -confirm off}). You can abbreviate this command as @code{d}. -@end table - -@node Disabling -@subsection Disabling breakpoints - -@kindex disable breakpoints -@kindex enable breakpoints -Rather than deleting a breakpoint, watchpoint, or catchpoint, you might -prefer to @dfn{disable} it. This makes the breakpoint inoperative as if -it had been deleted, but remembers the information on the breakpoint so -that you can @dfn{enable} it again later. - -You disable and enable breakpoints, watchpoints, and catchpoints with -the @code{enable} and @code{disable} commands, optionally specifying one -or more breakpoint numbers as arguments. Use @code{info break} or -@code{info watch} to print a list of breakpoints, watchpoints, and -catchpoints if you do not know which numbers to use. - -A breakpoint, watchpoint, or catchpoint can have any of four different -states of enablement: - -@itemize @bullet -@item -Enabled. The breakpoint stops your program. A breakpoint set -with the @code{break} command starts out in this state. -@item -Disabled. The breakpoint has no effect on your program. -@item -Enabled once. The breakpoint stops your program, but then becomes -disabled. -@item -Enabled for deletion. The breakpoint stops your program, but -immediately after it does so it is deleted permanently. A breakpoint -set with the @code{tbreak} command starts out in this state. -@end itemize - -You can use the following commands to enable or disable breakpoints, -watchpoints, and catchpoints: - -@table @code -@kindex disable breakpoints -@kindex disable -@kindex dis @r{(@code{disable})} -@item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} -Disable the specified breakpoints---or all breakpoints, if none are -listed. A disabled breakpoint has no effect but is not forgotten. All -options such as ignore-counts, conditions and commands are remembered in -case the breakpoint is enabled again later. You may abbreviate -@code{disable} as @code{dis}. - -@kindex enable breakpoints -@kindex enable -@item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} -Enable the specified breakpoints (or all defined breakpoints). They -become effective once again in stopping your program. - -@item enable @r{[}breakpoints@r{]} once @var{range}@dots{} -Enable the specified breakpoints temporarily. @value{GDBN} disables any -of these breakpoints immediately after stopping your program. - -@item enable @r{[}breakpoints@r{]} delete @var{range}@dots{} -Enable the specified breakpoints to work once, then die. @value{GDBN} -deletes any of these breakpoints as soon as your program stops there. -@end table - -@c FIXME: I think the following ``Except for [...] @code{tbreak}'' is -@c confusing: tbreak is also initially enabled. -Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks, -,Setting breakpoints}), breakpoints that you set are initially enabled; -subsequently, they become disabled or enabled only when you use one of -the commands above. (The command @code{until} can set and delete a -breakpoint of its own, but it does not change the state of your other -breakpoints; see @ref{Continuing and Stepping, ,Continuing and -stepping}.) - -@node Conditions -@subsection Break conditions -@cindex conditional breakpoints -@cindex breakpoint conditions - -@c FIXME what is scope of break condition expr? Context where wanted? -@c in particular for a watchpoint? -The simplest sort of breakpoint breaks every time your program reaches a -specified place. You can also specify a @dfn{condition} for a -breakpoint. A condition is just a Boolean expression in your -programming language (@pxref{Expressions, ,Expressions}). A breakpoint with -a condition evaluates the expression each time your program reaches it, -and your program stops only if the condition is @emph{true}. - -This is the converse of using assertions for program validation; in that -situation, you want to stop when the assertion is violated---that is, -when the condition is false. In C, if you want to test an assertion expressed -by the condition @var{assert}, you should set the condition -@samp{! @var{assert}} on the appropriate breakpoint. - -Conditions are also accepted for watchpoints; you may not need them, -since a watchpoint is inspecting the value of an expression anyhow---but -it might be simpler, say, to just set a watchpoint on a variable name, -and specify a condition that tests whether the new value is an interesting -one. - -Break conditions can have side effects, and may even call functions in -your program. This can be useful, for example, to activate functions -that log program progress, or to use your own print functions to -format special data structures. The effects are completely predictable -unless there is another enabled breakpoint at the same address. (In -that case, @value{GDBN} might see the other breakpoint first and stop your -program without checking the condition of this one.) Note that -breakpoint commands are usually more convenient and flexible than break -conditions for the -purpose of performing side effects when a breakpoint is reached -(@pxref{Break Commands, ,Breakpoint command lists}). - -Break conditions can be specified when a breakpoint is set, by using -@samp{if} in the arguments to the @code{break} command. @xref{Set -Breaks, ,Setting breakpoints}. They can also be changed at any time -with the @code{condition} command. - -You can also use the @code{if} keyword with the @code{watch} command. -The @code{catch} command does not recognize the @code{if} keyword; -@code{condition} is the only way to impose a further condition on a -catchpoint. - -@table @code -@kindex condition -@item condition @var{bnum} @var{expression} -Specify @var{expression} as the break condition for breakpoint, -watchpoint, or catchpoint number @var{bnum}. After you set a condition, -breakpoint @var{bnum} stops your program only if the value of -@var{expression} is true (nonzero, in C). When you use -@code{condition}, @value{GDBN} checks @var{expression} immediately for -syntactic correctness, and to determine whether symbols in it have -referents in the context of your breakpoint. If @var{expression} uses -symbols not referenced in the context of the breakpoint, @value{GDBN} -prints an error message: - -@example -No symbol "foo" in current context. -@end example - -@noindent -@value{GDBN} does -not actually evaluate @var{expression} at the time the @code{condition} -command (or a command that sets a breakpoint with a condition, like -@code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}. - -@item condition @var{bnum} -Remove the condition from breakpoint number @var{bnum}. It becomes -an ordinary unconditional breakpoint. -@end table - -@cindex ignore count (of breakpoint) -A special case of a breakpoint condition is to stop only when the -breakpoint has been reached a certain number of times. This is so -useful that there is a special way to do it, using the @dfn{ignore -count} of the breakpoint. Every breakpoint has an ignore count, which -is an integer. Most of the time, the ignore count is zero, and -therefore has no effect. But if your program reaches a breakpoint whose -ignore count is positive, then instead of stopping, it just decrements -the ignore count by one and continues. As a result, if the ignore count -value is @var{n}, the breakpoint does not stop the next @var{n} times -your program reaches it. - -@table @code -@kindex ignore -@item ignore @var{bnum} @var{count} -Set the ignore count of breakpoint number @var{bnum} to @var{count}. -The next @var{count} times the breakpoint is reached, your program's -execution does not stop; other than to decrement the ignore count, @value{GDBN} -takes no action. - -To make the breakpoint stop the next time it is reached, specify -a count of zero. - -When you use @code{continue} to resume execution of your program from a -breakpoint, you can specify an ignore count directly as an argument to -@code{continue}, rather than using @code{ignore}. @xref{Continuing and -Stepping,,Continuing and stepping}. - -If a breakpoint has a positive ignore count and a condition, the -condition is not checked. Once the ignore count reaches zero, -@value{GDBN} resumes checking the condition. - -You could achieve the effect of the ignore count with a condition such -as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that -is decremented each time. @xref{Convenience Vars, ,Convenience -variables}. -@end table - -Ignore counts apply to breakpoints, watchpoints, and catchpoints. - - -@node Break Commands -@subsection Breakpoint command lists - -@cindex breakpoint commands -You can give any breakpoint (or watchpoint or catchpoint) a series of -commands to execute when your program stops due to that breakpoint. For -example, you might want to print the values of certain expressions, or -enable other breakpoints. - -@table @code -@kindex commands -@kindex end -@item commands @r{[}@var{bnum}@r{]} -@itemx @dots{} @var{command-list} @dots{} -@itemx end -Specify a list of commands for breakpoint number @var{bnum}. The commands -themselves appear on the following lines. Type a line containing just -@code{end} to terminate the commands. - -To remove all commands from a breakpoint, type @code{commands} and -follow it immediately with @code{end}; that is, give no commands. - -With no @var{bnum} argument, @code{commands} refers to the last -breakpoint, watchpoint, or catchpoint set (not to the breakpoint most -recently encountered). -@end table - -Pressing @key{RET} as a means of repeating the last @value{GDBN} command is -disabled within a @var{command-list}. - -You can use breakpoint commands to start your program up again. Simply -use the @code{continue} command, or @code{step}, or any other command -that resumes execution. - -Any other commands in the command list, after a command that resumes -execution, are ignored. This is because any time you resume execution -(even with a simple @code{next} or @code{step}), you may encounter -another breakpoint---which could have its own command list, leading to -ambiguities about which list to execute. - -@kindex silent -If the first command you specify in a command list is @code{silent}, the -usual message about stopping at a breakpoint is not printed. This may -be desirable for breakpoints that are to print a specific message and -then continue. If none of the remaining commands print anything, you -see no sign that the breakpoint was reached. @code{silent} is -meaningful only at the beginning of a breakpoint command list. - -The commands @code{echo}, @code{output}, and @code{printf} allow you to -print precisely controlled output, and are often useful in silent -breakpoints. @xref{Output, ,Commands for controlled output}. - -For example, here is how you could use breakpoint commands to print the -value of @code{x} at entry to @code{foo} whenever @code{x} is positive. - -@example -break foo if x>0 -commands -silent -printf "x is %d\n",x -cont -end -@end example - -One application for breakpoint commands is to compensate for one bug so -you can test for another. Put a breakpoint just after the erroneous line -of code, give it a condition to detect the case in which something -erroneous has been done, and give it commands to assign correct values -to any variables that need them. End with the @code{continue} command -so that your program does not stop, and start with the @code{silent} -command so that no output is produced. Here is an example: - -@example -break 403 -commands -silent -set x = y + 4 -cont -end -@end example - -@node Breakpoint Menus -@subsection Breakpoint menus -@cindex overloading -@cindex symbol overloading - -Some programming languages (notably C@t{++}) permit a single function name -to be defined several times, for application in different contexts. -This is called @dfn{overloading}. When a function name is overloaded, -@samp{break @var{function}} is not enough to tell @value{GDBN} where you want -a breakpoint. If you realize this is a problem, you can use -something like @samp{break @var{function}(@var{types})} to specify which -particular version of the function you want. Otherwise, @value{GDBN} offers -you a menu of numbered choices for different possible breakpoints, and -waits for your selection with the prompt @samp{>}. The first two -options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1} -sets a breakpoint at each definition of @var{function}, and typing -@kbd{0} aborts the @code{break} command without setting any new -breakpoints. - -For example, the following session excerpt shows an attempt to set a -breakpoint at the overloaded symbol @code{String::after}. -We choose three particular definitions of that function name: - -@c FIXME! This is likely to change to show arg type lists, at least -@smallexample -@group -(@value{GDBP}) b String::after -[0] cancel -[1] all -[2] file:String.cc; line number:867 -[3] file:String.cc; line number:860 -[4] file:String.cc; line number:875 -[5] file:String.cc; line number:853 -[6] file:String.cc; line number:846 -[7] file:String.cc; line number:735 -> 2 4 6 -Breakpoint 1 at 0xb26c: file String.cc, line 867. -Breakpoint 2 at 0xb344: file String.cc, line 875. -Breakpoint 3 at 0xafcc: file String.cc, line 846. -Multiple breakpoints were set. -Use the "delete" command to delete unwanted - breakpoints. -(@value{GDBP}) -@end group -@end smallexample - -@c @ifclear BARETARGET -@node Error in Breakpoints -@subsection ``Cannot insert breakpoints'' -@c -@c FIXME!! 14/6/95 Is there a real example of this? Let's use it. -@c -Under some operating systems, breakpoints cannot be used in a program if -any other process is running that program. In this situation, -attempting to run or continue a program with a breakpoint causes -@value{GDBN} to print an error message: - -@example -Cannot insert breakpoints. -The same program may be running in another process. -@end example - -When this happens, you have three ways to proceed: - -@enumerate -@item -Remove or disable the breakpoints, then continue. - -@item -Suspend @value{GDBN}, and copy the file containing your program to a new -name. Resume @value{GDBN} and use the @code{exec-file} command to specify -that @value{GDBN} should run your program under that name. -Then start your program again. - -@item -Relink your program so that the text segment is nonsharable, using the -linker option @samp{-N}. The operating system limitation may not apply -to nonsharable executables. -@end enumerate -@c @end ifclear - -A similar message can be printed if you request too many active -hardware-assisted breakpoints and watchpoints: - -@c FIXME: the precise wording of this message may change; the relevant -@c source change is not committed yet (Sep 3, 1999). -@smallexample -Stopped; cannot insert breakpoints. -You may have requested too many hardware breakpoints and watchpoints. -@end smallexample - -@noindent -This message is printed when you attempt to resume the program, since -only then @value{GDBN} knows exactly how many hardware breakpoints and -watchpoints it needs to insert. - -When this message is printed, you need to disable or remove some of the -hardware-assisted breakpoints and watchpoints, and then continue. - - -@node Continuing and Stepping -@section Continuing and stepping - -@cindex stepping -@cindex continuing -@cindex resuming execution -@dfn{Continuing} means resuming program execution until your program -completes normally. In contrast, @dfn{stepping} means executing just -one more ``step'' of your program, where ``step'' may mean either one -line of source code, or one machine instruction (depending on what -particular command you use). Either when continuing or when stepping, -your program may stop even sooner, due to a breakpoint or a signal. (If -it stops due to a signal, you may want to use @code{handle}, or use -@samp{signal 0} to resume execution. @xref{Signals, ,Signals}.) - -@table @code -@kindex continue -@kindex c @r{(@code{continue})} -@kindex fg @r{(resume foreground execution)} -@item continue @r{[}@var{ignore-count}@r{]} -@itemx c @r{[}@var{ignore-count}@r{]} -@itemx fg @r{[}@var{ignore-count}@r{]} -Resume program execution, at the address where your program last stopped; -any breakpoints set at that address are bypassed. The optional argument -@var{ignore-count} allows you to specify a further number of times to -ignore a breakpoint at this location; its effect is like that of -@code{ignore} (@pxref{Conditions, ,Break conditions}). - -The argument @var{ignore-count} is meaningful only when your program -stopped due to a breakpoint. At other times, the argument to -@code{continue} is ignored. - -The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the -debugged program is deemed to be the foreground program) are provided -purely for convenience, and have exactly the same behavior as -@code{continue}. -@end table - -To resume execution at a different place, you can use @code{return} -(@pxref{Returning, ,Returning from a function}) to go back to the -calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a -different address}) to go to an arbitrary location in your program. - -A typical technique for using stepping is to set a breakpoint -(@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the -beginning of the function or the section of your program where a problem -is believed to lie, run your program until it stops at that breakpoint, -and then step through the suspect area, examining the variables that are -interesting, until you see the problem happen. - -@table @code -@kindex step -@kindex s @r{(@code{step})} -@item step -Continue running your program until control reaches a different source -line, then stop it and return control to @value{GDBN}. This command is -abbreviated @code{s}. - -@quotation -@c "without debugging information" is imprecise; actually "without line -@c numbers in the debugging information". (gcc -g1 has debugging info but -@c not line numbers). But it seems complex to try to make that -@c distinction here. -@emph{Warning:} If you use the @code{step} command while control is -within a function that was compiled without debugging information, -execution proceeds until control reaches a function that does have -debugging information. Likewise, it will not step into a function which -is compiled without debugging information. To step through functions -without debugging information, use the @code{stepi} command, described -below. -@end quotation - -The @code{step} command only stops at the first instruction of a source -line. This prevents the multiple stops that could otherwise occur in -@code{switch} statements, @code{for} loops, etc. @code{step} continues -to stop if a function that has debugging information is called within -the line. In other words, @code{step} @emph{steps inside} any functions -called within the line. - -Also, the @code{step} command only enters a function if there is line -number information for the function. Otherwise it acts like the -@code{next} command. This avoids problems when using @code{cc -gl} -on MIPS machines. Previously, @code{step} entered subroutines if there -was any debugging information about the routine. - -@item step @var{count} -Continue running as in @code{step}, but do so @var{count} times. If a -breakpoint is reached, or a signal not related to stepping occurs before -@var{count} steps, stepping stops right away. - -@kindex next -@kindex n @r{(@code{next})} -@item next @r{[}@var{count}@r{]} -Continue to the next source line in the current (innermost) stack frame. -This is similar to @code{step}, but function calls that appear within -the line of code are executed without stopping. Execution stops when -control reaches a different line of code at the original stack level -that was executing when you gave the @code{next} command. This command -is abbreviated @code{n}. - -An argument @var{count} is a repeat count, as for @code{step}. - - -@c FIX ME!! Do we delete this, or is there a way it fits in with -@c the following paragraph? --- Vctoria -@c -@c @code{next} within a function that lacks debugging information acts like -@c @code{step}, but any function calls appearing within the code of the -@c function are executed without stopping. - -The @code{next} command only stops at the first instruction of a -source line. This prevents multiple stops that could otherwise occur in -@code{switch} statements, @code{for} loops, etc. - -@kindex set step-mode -@item set step-mode -@cindex functions without line info, and stepping -@cindex stepping into functions with no line info -@itemx set step-mode on -The @code{set step-mode on} command causes the @code{step} command to -stop at the first instruction of a function which contains no debug line -information rather than stepping over it. - -This is useful in cases where you may be interested in inspecting the -machine instructions of a function which has no symbolic info and do not -want @value{GDBN} to automatically skip over this function. - -@item set step-mode off -Causes the @code{step} command to step over any functions which contains no -debug information. This is the default. - -@kindex finish -@item finish -Continue running until just after function in the selected stack frame -returns. Print the returned value (if any). - -Contrast this with the @code{return} command (@pxref{Returning, -,Returning from a function}). - -@kindex until -@kindex u @r{(@code{until})} -@item until -@itemx u -Continue running until a source line past the current line, in the -current stack frame, is reached. This command is used to avoid single -stepping through a loop more than once. It is like the @code{next} -command, except that when @code{until} encounters a jump, it -automatically continues execution until the program counter is greater -than the address of the jump. - -This means that when you reach the end of a loop after single stepping -though it, @code{until} makes your program continue execution until it -exits the loop. In contrast, a @code{next} command at the end of a loop -simply steps back to the beginning of the loop, which forces you to step -through the next iteration. - -@code{until} always stops your program if it attempts to exit the current -stack frame. - -@code{until} may produce somewhat counterintuitive results if the order -of machine code does not match the order of the source lines. For -example, in the following excerpt from a debugging session, the @code{f} -(@code{frame}) command shows that execution is stopped at line -@code{206}; yet when we use @code{until}, we get to line @code{195}: - -@example -(@value{GDBP}) f -#0 main (argc=4, argv=0xf7fffae8) at m4.c:206 -206 expand_input(); -(@value{GDBP}) until -195 for ( ; argc > 0; NEXTARG) @{ -@end example - -This happened because, for execution efficiency, the compiler had -generated code for the loop closure test at the end, rather than the -start, of the loop---even though the test in a C @code{for}-loop is -written before the body of the loop. The @code{until} command appeared -to step back to the beginning of the loop when it advanced to this -expression; however, it has not really gone to an earlier -statement---not in terms of the actual machine code. - -@code{until} with no argument works by means of single -instruction stepping, and hence is slower than @code{until} with an -argument. - -@item until @var{location} -@itemx u @var{location} -Continue running your program until either the specified location is -reached, or the current stack frame returns. @var{location} is any of -the forms of argument acceptable to @code{break} (@pxref{Set Breaks, -,Setting breakpoints}). This form of the command uses breakpoints, -and hence is quicker than @code{until} without an argument. - -@kindex stepi -@kindex si @r{(@code{stepi})} -@item stepi -@itemx stepi @var{arg} -@itemx si -Execute one machine instruction, then stop and return to the debugger. - -It is often useful to do @samp{display/i $pc} when stepping by machine -instructions. This makes @value{GDBN} automatically display the next -instruction to be executed, each time your program stops. @xref{Auto -Display,, Automatic display}. - -An argument is a repeat count, as in @code{step}. - -@need 750 -@kindex nexti -@kindex ni @r{(@code{nexti})} -@item nexti -@itemx nexti @var{arg} -@itemx ni -Execute one machine instruction, but if it is a function call, -proceed until the function returns. - -An argument is a repeat count, as in @code{next}. -@end table - -@node Signals -@section Signals -@cindex signals - -A signal is an asynchronous event that can happen in a program. The -operating system defines the possible kinds of signals, and gives each -kind a name and a number. For example, in Unix @code{SIGINT} is the -signal a program gets when you type an interrupt character (often @kbd{C-c}); -@code{SIGSEGV} is the signal a program gets from referencing a place in -memory far away from all the areas in use; @code{SIGALRM} occurs when -the alarm clock timer goes off (which happens only if your program has -requested an alarm). - -@cindex fatal signals -Some signals, including @code{SIGALRM}, are a normal part of the -functioning of your program. Others, such as @code{SIGSEGV}, indicate -errors; these signals are @dfn{fatal} (they kill your program immediately) if the -program has not specified in advance some other way to handle the signal. -@code{SIGINT} does not indicate an error in your program, but it is normally -fatal so it can carry out the purpose of the interrupt: to kill the program. - -@value{GDBN} has the ability to detect any occurrence of a signal in your -program. You can tell @value{GDBN} in advance what to do for each kind of -signal. - -@cindex handling signals -Normally, @value{GDBN} is set up to let the non-erroneous signals like -@code{SIGALRM} be silently passed to your program -(so as not to interfere with their role in the program's functioning) -but to stop your program immediately whenever an error signal happens. -You can change these settings with the @code{handle} command. - -@table @code -@kindex info signals -@item info signals -@itemx info handle -Print a table of all the kinds of signals and how @value{GDBN} has been told to -handle each one. You can use this to see the signal numbers of all -the defined types of signals. - -@code{info handle} is an alias for @code{info signals}. - -@kindex handle -@item handle @var{signal} @var{keywords}@dots{} -Change the way @value{GDBN} handles signal @var{signal}. @var{signal} -can be the number of a signal or its name (with or without the -@samp{SIG} at the beginning); a list of signal numbers of the form -@samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the -known signals. The @var{keywords} say what change to make. -@end table - -@c @group -The keywords allowed by the @code{handle} command can be abbreviated. -Their full names are: - -@table @code -@item nostop -@value{GDBN} should not stop your program when this signal happens. It may -still print a message telling you that the signal has come in. - -@item stop -@value{GDBN} should stop your program when this signal happens. This implies -the @code{print} keyword as well. - -@item print -@value{GDBN} should print a message when this signal happens. - -@item noprint -@value{GDBN} should not mention the occurrence of the signal at all. This -implies the @code{nostop} keyword as well. - -@item pass -@itemx noignore -@value{GDBN} should allow your program to see this signal; your program -can handle the signal, or else it may terminate if the signal is fatal -and not handled. @code{pass} and @code{noignore} are synonyms. - -@item nopass -@itemx ignore -@value{GDBN} should not allow your program to see this signal. -@code{nopass} and @code{ignore} are synonyms. -@end table -@c @end group - -When a signal stops your program, the signal is not visible to the -program until you -continue. Your program sees the signal then, if @code{pass} is in -effect for the signal in question @emph{at that time}. In other words, -after @value{GDBN} reports a signal, you can use the @code{handle} -command with @code{pass} or @code{nopass} to control whether your -program sees that signal when you continue. - -The default is set to @code{nostop}, @code{noprint}, @code{pass} for -non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and -@code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the -erroneous signals. - -You can also use the @code{signal} command to prevent your program from -seeing a signal, or cause it to see a signal it normally would not see, -or to give it any signal at any time. For example, if your program stopped -due to some sort of memory reference error, you might store correct -values into the erroneous variables and continue, hoping to see more -execution; but your program would probably terminate immediately as -a result of the fatal signal once it saw the signal. To prevent this, -you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your -program a signal}. - -@node Thread Stops -@section Stopping and starting multi-thread programs - -When your program has multiple threads (@pxref{Threads,, Debugging -programs with multiple threads}), you can choose whether to set -breakpoints on all threads, or on a particular thread. - -@table @code -@cindex breakpoints and threads -@cindex thread breakpoints -@kindex break @dots{} thread @var{threadno} -@item break @var{linespec} thread @var{threadno} -@itemx break @var{linespec} thread @var{threadno} if @dots{} -@var{linespec} specifies source lines; there are several ways of -writing them, but the effect is always to specify some source line. - -Use the qualifier @samp{thread @var{threadno}} with a breakpoint command -to specify that you only want @value{GDBN} to stop the program when a -particular thread reaches this breakpoint. @var{threadno} is one of the -numeric thread identifiers assigned by @value{GDBN}, shown in the first -column of the @samp{info threads} display. - -If you do not specify @samp{thread @var{threadno}} when you set a -breakpoint, the breakpoint applies to @emph{all} threads of your -program. - -You can use the @code{thread} qualifier on conditional breakpoints as -well; in this case, place @samp{thread @var{threadno}} before the -breakpoint condition, like this: - -@smallexample -(@value{GDBP}) break frik.c:13 thread 28 if bartab > lim -@end smallexample - -@end table - -@cindex stopped threads -@cindex threads, stopped -Whenever your program stops under @value{GDBN} for any reason, -@emph{all} threads of execution stop, not just the current thread. This -allows you to examine the overall state of the program, including -switching between threads, without worrying that things may change -underfoot. - -@cindex continuing threads -@cindex threads, continuing -Conversely, whenever you restart the program, @emph{all} threads start -executing. @emph{This is true even when single-stepping} with commands -like @code{step} or @code{next}. - -In particular, @value{GDBN} cannot single-step all threads in lockstep. -Since thread scheduling is up to your debugging target's operating -system (not controlled by @value{GDBN}), other threads may -execute more than one statement while the current thread completes a -single step. Moreover, in general other threads stop in the middle of a -statement, rather than at a clean statement boundary, when the program -stops. - -You might even find your program stopped in another thread after -continuing or even single-stepping. This happens whenever some other -thread runs into a breakpoint, a signal, or an exception before the -first thread completes whatever you requested. - -On some OSes, you can lock the OS scheduler and thus allow only a single -thread to run. - -@table @code -@item set scheduler-locking @var{mode} -Set the scheduler locking mode. If it is @code{off}, then there is no -locking and any thread may run at any time. If @code{on}, then only the -current thread may run when the inferior is resumed. The @code{step} -mode optimizes for single-stepping. It stops other threads from -``seizing the prompt'' by preempting the current thread while you are -stepping. Other threads will only rarely (or never) get a chance to run -when you step. They are more likely to run when you @samp{next} over a -function call, and they are completely free to run when you use commands -like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another -thread hits a breakpoint during its timeslice, they will never steal the -@value{GDBN} prompt away from the thread that you are debugging. - -@item show scheduler-locking -Display the current scheduler locking mode. -@end table - - -@node Stack -@chapter Examining the Stack - -When your program has stopped, the first thing you need to know is where it -stopped and how it got there. - -@cindex call stack -Each time your program performs a function call, information about the call -is generated. -That information includes the location of the call in your program, -the arguments of the call, -and the local variables of the function being called. -The information is saved in a block of data called a @dfn{stack frame}. -The stack frames are allocated in a region of memory called the @dfn{call -stack}. - -When your program stops, the @value{GDBN} commands for examining the -stack allow you to see all of this information. - -@cindex selected frame -One of the stack frames is @dfn{selected} by @value{GDBN} and many -@value{GDBN} commands refer implicitly to the selected frame. In -particular, whenever you ask @value{GDBN} for the value of a variable in -your program, the value is found in the selected frame. There are -special @value{GDBN} commands to select whichever frame you are -interested in. @xref{Selection, ,Selecting a frame}. - -When your program stops, @value{GDBN} automatically selects the -currently executing frame and describes it briefly, similar to the -@code{frame} command (@pxref{Frame Info, ,Information about a frame}). - -@menu -* Frames:: Stack frames -* Backtrace:: Backtraces -* Selection:: Selecting a frame -* Frame Info:: Information on a frame - -@end menu - -@node Frames -@section Stack frames - -@cindex frame, definition -@cindex stack frame -The call stack is divided up into contiguous pieces called @dfn{stack -frames}, or @dfn{frames} for short; each frame is the data associated -with one call to one function. The frame contains the arguments given -to the function, the function's local variables, and the address at -which the function is executing. - -@cindex initial frame -@cindex outermost frame -@cindex innermost frame -When your program is started, the stack has only one frame, that of the -function @code{main}. This is called the @dfn{initial} frame or the -@dfn{outermost} frame. Each time a function is called, a new frame is -made. Each time a function returns, the frame for that function invocation -is eliminated. If a function is recursive, there can be many frames for -the same function. The frame for the function in which execution is -actually occurring is called the @dfn{innermost} frame. This is the most -recently created of all the stack frames that still exist. - -@cindex frame pointer -Inside your program, stack frames are identified by their addresses. A -stack frame consists of many bytes, each of which has its own address; each -kind of computer has a convention for choosing one byte whose -address serves as the address of the frame. Usually this address is kept -in a register called the @dfn{frame pointer register} while execution is -going on in that frame. - -@cindex frame number -@value{GDBN} assigns numbers to all existing stack frames, starting with -zero for the innermost frame, one for the frame that called it, -and so on upward. These numbers do not really exist in your program; -they are assigned by @value{GDBN} to give you a way of designating stack -frames in @value{GDBN} commands. - -@c The -fomit-frame-pointer below perennially causes hbox overflow -@c underflow problems. -@cindex frameless execution -Some compilers provide a way to compile functions so that they operate -without stack frames. (For example, the @value{GCC} option -@example -@samp{-fomit-frame-pointer} -@end example -generates functions without a frame.) -This is occasionally done with heavily used library functions to save -the frame setup time. @value{GDBN} has limited facilities for dealing -with these function invocations. If the innermost function invocation -has no stack frame, @value{GDBN} nevertheless regards it as though -it had a separate frame, which is numbered zero as usual, allowing -correct tracing of the function call chain. However, @value{GDBN} has -no provision for frameless functions elsewhere in the stack. - -@table @code -@kindex frame@r{, command} -@cindex current stack frame -@item frame @var{args} -The @code{frame} command allows you to move from one stack frame to another, -and to print the stack frame you select. @var{args} may be either the -address of the frame or the stack frame number. Without an argument, -@code{frame} prints the current stack frame. - -@kindex select-frame -@cindex selecting frame silently -@item select-frame -The @code{select-frame} command allows you to move from one stack frame -to another without printing the frame. This is the silent version of -@code{frame}. -@end table - -@node Backtrace -@section Backtraces - -@cindex backtraces -@cindex tracebacks -@cindex stack traces -A backtrace is a summary of how your program got where it is. It shows one -line per frame, for many frames, starting with the currently executing -frame (frame zero), followed by its caller (frame one), and on up the -stack. - -@table @code -@kindex backtrace -@kindex bt @r{(@code{backtrace})} -@item backtrace -@itemx bt -Print a backtrace of the entire stack: one line per frame for all -frames in the stack. - -You can stop the backtrace at any time by typing the system interrupt -character, normally @kbd{C-c}. - -@item backtrace @var{n} -@itemx bt @var{n} -Similar, but print only the innermost @var{n} frames. - -@item backtrace -@var{n} -@itemx bt -@var{n} -Similar, but print only the outermost @var{n} frames. -@end table - -@kindex where -@kindex info stack -@kindex info s @r{(@code{info stack})} -The names @code{where} and @code{info stack} (abbreviated @code{info s}) -are additional aliases for @code{backtrace}. - -Each line in the backtrace shows the frame number and the function name. -The program counter value is also shown---unless you use @code{set -print address off}. The backtrace also shows the source file name and -line number, as well as the arguments to the function. The program -counter value is omitted if it is at the beginning of the code for that -line number. - -Here is an example of a backtrace. It was made with the command -@samp{bt 3}, so it shows the innermost three frames. - -@smallexample -@group -#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) - at builtin.c:993 -#1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242 -#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08) - at macro.c:71 -(More stack frames follow...) -@end group -@end smallexample - -@noindent -The display for frame zero does not begin with a program counter -value, indicating that your program has stopped at the beginning of the -code for line @code{993} of @code{builtin.c}. - -@node Selection -@section Selecting a frame - -Most commands for examining the stack and other data in your program work on -whichever stack frame is selected at the moment. Here are the commands for -selecting a stack frame; all of them finish by printing a brief description -of the stack frame just selected. - -@table @code -@kindex frame@r{, selecting} -@kindex f @r{(@code{frame})} -@item frame @var{n} -@itemx f @var{n} -Select frame number @var{n}. Recall that frame zero is the innermost -(currently executing) frame, frame one is the frame that called the -innermost one, and so on. The highest-numbered frame is the one for -@code{main}. - -@item frame @var{addr} -@itemx f @var{addr} -Select the frame at address @var{addr}. This is useful mainly if the -chaining of stack frames has been damaged by a bug, making it -impossible for @value{GDBN} to assign numbers properly to all frames. In -addition, this can be useful when your program has multiple stacks and -switches between them. - -On the SPARC architecture, @code{frame} needs two addresses to -select an arbitrary frame: a frame pointer and a stack pointer. - -On the MIPS and Alpha architecture, it needs two addresses: a stack -pointer and a program counter. - -On the 29k architecture, it needs three addresses: a register stack -pointer, a program counter, and a memory stack pointer. -@c note to future updaters: this is conditioned on a flag -@c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date -@c as of 27 Jan 1994. - -@kindex up -@item up @var{n} -Move @var{n} frames up the stack. For positive numbers @var{n}, this -advances toward the outermost frame, to higher frame numbers, to frames -that have existed longer. @var{n} defaults to one. - -@kindex down -@kindex do @r{(@code{down})} -@item down @var{n} -Move @var{n} frames down the stack. For positive numbers @var{n}, this -advances toward the innermost frame, to lower frame numbers, to frames -that were created more recently. @var{n} defaults to one. You may -abbreviate @code{down} as @code{do}. -@end table - -All of these commands end by printing two lines of output describing the -frame. The first line shows the frame number, the function name, the -arguments, and the source file and line number of execution in that -frame. The second line shows the text of that source line. - -@need 1000 -For example: - -@smallexample -@group -(@value{GDBP}) up -#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) - at env.c:10 -10 read_input_file (argv[i]); -@end group -@end smallexample - -After such a printout, the @code{list} command with no arguments -prints ten lines centered on the point of execution in the frame. -@xref{List, ,Printing source lines}. - -@table @code -@kindex down-silently -@kindex up-silently -@item up-silently @var{n} -@itemx down-silently @var{n} -These two commands are variants of @code{up} and @code{down}, -respectively; they differ in that they do their work silently, without -causing display of the new frame. They are intended primarily for use -in @value{GDBN} command scripts, where the output might be unnecessary and -distracting. -@end table - -@node Frame Info -@section Information about a frame - -There are several other commands to print information about the selected -stack frame. - -@table @code -@item frame -@itemx f -When used without any argument, this command does not change which -frame is selected, but prints a brief description of the currently -selected stack frame. It can be abbreviated @code{f}. With an -argument, this command is used to select a stack frame. -@xref{Selection, ,Selecting a frame}. - -@kindex info frame -@kindex info f @r{(@code{info frame})} -@item info frame -@itemx info f -This command prints a verbose description of the selected stack frame, -including: - -@itemize @bullet -@item -the address of the frame -@item -the address of the next frame down (called by this frame) -@item -the address of the next frame up (caller of this frame) -@item -the language in which the source code corresponding to this frame is written -@item -the address of the frame's arguments -@item -the address of the frame's local variables -@item -the program counter saved in it (the address of execution in the caller frame) -@item -which registers were saved in the frame -@end itemize - -@noindent The verbose description is useful when -something has gone wrong that has made the stack format fail to fit -the usual conventions. - -@item info frame @var{addr} -@itemx info f @var{addr} -Print a verbose description of the frame at address @var{addr}, without -selecting that frame. The selected frame remains unchanged by this -command. This requires the same kind of address (more than one for some -architectures) that you specify in the @code{frame} command. -@xref{Selection, ,Selecting a frame}. - -@kindex info args -@item info args -Print the arguments of the selected frame, each on a separate line. - -@item info locals -@kindex info locals -Print the local variables of the selected frame, each on a separate -line. These are all variables (declared either static or automatic) -accessible at the point of execution of the selected frame. - -@kindex info catch -@cindex catch exceptions, list active handlers -@cindex exception handlers, how to list -@item info catch -Print a list of all the exception handlers that are active in the -current stack frame at the current point of execution. To see other -exception handlers, visit the associated frame (using the @code{up}, -@code{down}, or @code{frame} commands); then type @code{info catch}. -@xref{Set Catchpoints, , Setting catchpoints}. - -@end table - - -@node Source -@chapter Examining Source Files - -@value{GDBN} can print parts of your program's source, since the debugging -information recorded in the program tells @value{GDBN} what source files were -used to build it. When your program stops, @value{GDBN} spontaneously prints -the line where it stopped. Likewise, when you select a stack frame -(@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where -execution in that frame has stopped. You can print other portions of -source files by explicit command. - -If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may -prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using -@value{GDBN} under @sc{gnu} Emacs}. - -@menu -* List:: Printing source lines -* Search:: Searching source files -* Source Path:: Specifying source directories -* Machine Code:: Source and machine code -@end menu - -@node List -@section Printing source lines - -@kindex list -@kindex l @r{(@code{list})} -To print lines from a source file, use the @code{list} command -(abbreviated @code{l}). By default, ten lines are printed. -There are several ways to specify what part of the file you want to print. - -Here are the forms of the @code{list} command most commonly used: - -@table @code -@item list @var{linenum} -Print lines centered around line number @var{linenum} in the -current source file. - -@item list @var{function} -Print lines centered around the beginning of function -@var{function}. - -@item list -Print more lines. If the last lines printed were printed with a -@code{list} command, this prints lines following the last lines -printed; however, if the last line printed was a solitary line printed -as part of displaying a stack frame (@pxref{Stack, ,Examining the -Stack}), this prints lines centered around that line. - -@item list - -Print lines just before the lines last printed. -@end table - -By default, @value{GDBN} prints ten source lines with any of these forms of -the @code{list} command. You can change this using @code{set listsize}: - -@table @code -@kindex set listsize -@item set listsize @var{count} -Make the @code{list} command display @var{count} source lines (unless -the @code{list} argument explicitly specifies some other number). - -@kindex show listsize -@item show listsize -Display the number of lines that @code{list} prints. -@end table - -Repeating a @code{list} command with @key{RET} discards the argument, -so it is equivalent to typing just @code{list}. This is more useful -than listing the same lines again. An exception is made for an -argument of @samp{-}; that argument is preserved in repetition so that -each repetition moves up in the source file. - -@cindex linespec -In general, the @code{list} command expects you to supply zero, one or two -@dfn{linespecs}. Linespecs specify source lines; there are several ways -of writing them, but the effect is always to specify some source line. -Here is a complete description of the possible arguments for @code{list}: - -@table @code -@item list @var{linespec} -Print lines centered around the line specified by @var{linespec}. - -@item list @var{first},@var{last} -Print lines from @var{first} to @var{last}. Both arguments are -linespecs. - -@item list ,@var{last} -Print lines ending with @var{last}. - -@item list @var{first}, -Print lines starting with @var{first}. - -@item list + -Print lines just after the lines last printed. - -@item list - -Print lines just before the lines last printed. - -@item list -As described in the preceding table. -@end table - -Here are the ways of specifying a single source line---all the -kinds of linespec. - -@table @code -@item @var{number} -Specifies line @var{number} of the current source file. -When a @code{list} command has two linespecs, this refers to -the same source file as the first linespec. - -@item +@var{offset} -Specifies the line @var{offset} lines after the last line printed. -When used as the second linespec in a @code{list} command that has -two, this specifies the line @var{offset} lines down from the -first linespec. - -@item -@var{offset} -Specifies the line @var{offset} lines before the last line printed. - -@item @var{filename}:@var{number} -Specifies line @var{number} in the source file @var{filename}. - -@item @var{function} -Specifies the line that begins the body of the function @var{function}. -For example: in C, this is the line with the open brace. - -@item @var{filename}:@var{function} -Specifies the line of the open-brace that begins the body of the -function @var{function} in the file @var{filename}. You only need the -file name with a function name to avoid ambiguity when there are -identically named functions in different source files. - -@item *@var{address} -Specifies the line containing the program address @var{address}. -@var{address} may be any expression. -@end table - -@node Search -@section Searching source files -@cindex searching -@kindex reverse-search - -There are two commands for searching through the current source file for a -regular expression. - -@table @code -@kindex search -@kindex forward-search -@item forward-search @var{regexp} -@itemx search @var{regexp} -The command @samp{forward-search @var{regexp}} checks each line, -starting with the one following the last line listed, for a match for -@var{regexp}. It lists the line that is found. You can use the -synonym @samp{search @var{regexp}} or abbreviate the command name as -@code{fo}. - -@item reverse-search @var{regexp} -The command @samp{reverse-search @var{regexp}} checks each line, starting -with the one before the last line listed and going backward, for a match -for @var{regexp}. It lists the line that is found. You can abbreviate -this command as @code{rev}. -@end table - -@node Source Path -@section Specifying source directories - -@cindex source path -@cindex directories for source files -Executable programs sometimes do not record the directories of the source -files from which they were compiled, just the names. Even when they do, -the directories could be moved between the compilation and your debugging -session. @value{GDBN} has a list of directories to search for source files; -this is called the @dfn{source path}. Each time @value{GDBN} wants a source file, -it tries all the directories in the list, in the order they are present -in the list, until it finds a file with the desired name. Note that -the executable search path is @emph{not} used for this purpose. Neither is -the current working directory, unless it happens to be in the source -path. - -If @value{GDBN} cannot find a source file in the source path, and the -object program records a directory, @value{GDBN} tries that directory -too. If the source path is empty, and there is no record of the -compilation directory, @value{GDBN} looks in the current directory as a -last resort. - -Whenever you reset or rearrange the source path, @value{GDBN} clears out -any information it has cached about where source files are found and where -each line is in the file. - -@kindex directory -@kindex dir -When you start @value{GDBN}, its source path includes only @samp{cdir} -and @samp{cwd}, in that order. -To add other directories, use the @code{directory} command. - -@table @code -@item directory @var{dirname} @dots{} -@item dir @var{dirname} @dots{} -Add directory @var{dirname} to the front of the source path. Several -directory names may be given to this command, separated by @samp{:} -(@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as -part of absolute file names) or -whitespace. You may specify a directory that is already in the source -path; this moves it forward, so @value{GDBN} searches it sooner. - -@kindex cdir -@kindex cwd -@vindex $cdir@r{, convenience variable} -@vindex $cwdr@r{, convenience variable} -@cindex compilation directory -@cindex current directory -@cindex working directory -@cindex directory, current -@cindex directory, compilation -You can use the string @samp{$cdir} to refer to the compilation -directory (if one is recorded), and @samp{$cwd} to refer to the current -working directory. @samp{$cwd} is not the same as @samp{.}---the former -tracks the current working directory as it changes during your @value{GDBN} -session, while the latter is immediately expanded to the current -directory at the time you add an entry to the source path. - -@item directory -Reset the source path to empty again. This requires confirmation. - -@c RET-repeat for @code{directory} is explicitly disabled, but since -@c repeating it would be a no-op we do not say that. (thanks to RMS) - -@item show directories -@kindex show directories -Print the source path: show which directories it contains. -@end table - -If your source path is cluttered with directories that are no longer of -interest, @value{GDBN} may sometimes cause confusion by finding the wrong -versions of source. You can correct the situation as follows: - -@enumerate -@item -Use @code{directory} with no argument to reset the source path to empty. - -@item -Use @code{directory} with suitable arguments to reinstall the -directories you want in the source path. You can add all the -directories in one command. -@end enumerate - -@node Machine Code -@section Source and machine code - -You can use the command @code{info line} to map source lines to program -addresses (and vice versa), and the command @code{disassemble} to display -a range of addresses as machine instructions. When run under @sc{gnu} Emacs -mode, the @code{info line} command causes the arrow to point to the -line specified. Also, @code{info line} prints addresses in symbolic form as -well as hex. - -@table @code -@kindex info line -@item info line @var{linespec} -Print the starting and ending addresses of the compiled code for -source line @var{linespec}. You can specify source lines in any of -the ways understood by the @code{list} command (@pxref{List, ,Printing -source lines}). -@end table - -For example, we can use @code{info line} to discover the location of -the object code for the first line of function -@code{m4_changequote}: - -@c FIXME: I think this example should also show the addresses in -@c symbolic form, as they usually would be displayed. -@smallexample -(@value{GDBP}) info line m4_changequote -Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. -@end smallexample - -@noindent -We can also inquire (using @code{*@var{addr}} as the form for -@var{linespec}) what source line covers a particular address: -@smallexample -(@value{GDBP}) info line *0x63ff -Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. -@end smallexample - -@cindex @code{$_} and @code{info line} -@kindex x@r{(examine), and} info line -After @code{info line}, the default address for the @code{x} command -is changed to the starting address of the line, so that @samp{x/i} is -sufficient to begin examining the machine code (@pxref{Memory, -,Examining memory}). Also, this address is saved as the value of the -convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience -variables}). - -@table @code -@kindex disassemble -@cindex assembly instructions -@cindex instructions, assembly -@cindex machine instructions -@cindex listing machine instructions -@item disassemble -This specialized command dumps a range of memory as machine -instructions. The default memory range is the function surrounding the -program counter of the selected frame. A single argument to this -command is a program counter value; @value{GDBN} dumps the function -surrounding this value. Two arguments specify a range of addresses -(first inclusive, second exclusive) to dump. -@end table - -The following example shows the disassembly of a range of addresses of -HP PA-RISC 2.0 code: - -@smallexample -(@value{GDBP}) disas 0x32c4 0x32e4 -Dump of assembler code from 0x32c4 to 0x32e4: -0x32c4 <main+204>: addil 0,dp -0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26 -0x32cc <main+212>: ldil 0x3000,r31 -0x32d0 <main+216>: ble 0x3f8(sr4,r31) -0x32d4 <main+220>: ldo 0(r31),rp -0x32d8 <main+224>: addil -0x800,dp -0x32dc <main+228>: ldo 0x588(r1),r26 -0x32e0 <main+232>: ldil 0x3000,r31 -End of assembler dump. -@end smallexample - -Some architectures have more than one commonly-used set of instruction -mnemonics or other syntax. - -@table @code -@kindex set disassembly-flavor -@cindex assembly instructions -@cindex instructions, assembly -@cindex machine instructions -@cindex listing machine instructions -@cindex Intel disassembly flavor -@cindex AT&T disassembly flavor -@item set disassembly-flavor @var{instruction-set} -Select the instruction set to use when disassembling the -program via the @code{disassemble} or @code{x/i} commands. - -Currently this command is only defined for the Intel x86 family. You -can set @var{instruction-set} to either @code{intel} or @code{att}. -The default is @code{att}, the AT&T flavor used by default by Unix -assemblers for x86-based targets. -@end table - - -@node Data -@chapter Examining Data - -@cindex printing data -@cindex examining data -@kindex print -@kindex inspect -@c "inspect" is not quite a synonym if you are using Epoch, which we do not -@c document because it is nonstandard... Under Epoch it displays in a -@c different window or something like that. -The usual way to examine data in your program is with the @code{print} -command (abbreviated @code{p}), or its synonym @code{inspect}. It -evaluates and prints the value of an expression of the language your -program is written in (@pxref{Languages, ,Using @value{GDBN} with -Different Languages}). - -@table @code -@item print @var{expr} -@itemx print /@var{f} @var{expr} -@var{expr} is an expression (in the source language). By default the -value of @var{expr} is printed in a format appropriate to its data type; -you can choose a different format by specifying @samp{/@var{f}}, where -@var{f} is a letter specifying the format; see @ref{Output Formats,,Output -formats}. - -@item print -@itemx print /@var{f} -If you omit @var{expr}, @value{GDBN} displays the last value again (from the -@dfn{value history}; @pxref{Value History, ,Value history}). This allows you to -conveniently inspect the same value in an alternative format. -@end table - -A more low-level way of examining data is with the @code{x} command. -It examines data in memory at a specified address and prints it in a -specified format. @xref{Memory, ,Examining memory}. - -If you are interested in information about types, or about how the -fields of a struct or a class are declared, use the @code{ptype @var{exp}} -command rather than @code{print}. @xref{Symbols, ,Examining the Symbol -Table}. - -@menu -* Expressions:: Expressions -* Variables:: Program variables -* Arrays:: Artificial arrays -* Output Formats:: Output formats -* Memory:: Examining memory -* Auto Display:: Automatic display -* Print Settings:: Print settings -* Value History:: Value history -* Convenience Vars:: Convenience variables -* Registers:: Registers -* Floating Point Hardware:: Floating point hardware -* Memory Region Attributes:: Memory region attributes -@end menu - -@node Expressions -@section Expressions - -@cindex expressions -@code{print} and many other @value{GDBN} commands accept an expression and -compute its value. Any kind of constant, variable or operator defined -by the programming language you are using is valid in an expression in -@value{GDBN}. This includes conditional expressions, function calls, casts -and string constants. It unfortunately does not include symbols defined -by preprocessor @code{#define} commands. - -@value{GDBN} supports array constants in expressions input by -the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example, -you can use the command @code{print @{1, 2, 3@}} to build up an array in -memory that is @code{malloc}ed in the target program. - -Because C is so widespread, most of the expressions shown in examples in -this manual are in C. @xref{Languages, , Using @value{GDBN} with Different -Languages}, for information on how to use expressions in other -languages. - -In this section, we discuss operators that you can use in @value{GDBN} -expressions regardless of your programming language. - -Casts are supported in all languages, not just in C, because it is so -useful to cast a number into a pointer in order to examine a structure -at that address in memory. -@c FIXME: casts supported---Mod2 true? - -@value{GDBN} supports these operators, in addition to those common -to programming languages: - -@table @code -@item @@ -@samp{@@} is a binary operator for treating parts of memory as arrays. -@xref{Arrays, ,Artificial arrays}, for more information. - -@item :: -@samp{::} allows you to specify a variable in terms of the file or -function where it is defined. @xref{Variables, ,Program variables}. - -@cindex @{@var{type}@} -@cindex type casting memory -@cindex memory, viewing as typed object -@cindex casts, to view memory -@item @{@var{type}@} @var{addr} -Refers to an object of type @var{type} stored at address @var{addr} in -memory. @var{addr} may be any expression whose value is an integer or -pointer (but parentheses are required around binary operators, just as in -a cast). This construct is allowed regardless of what kind of data is -normally supposed to reside at @var{addr}. -@end table - -@node Variables -@section Program variables - -The most common kind of expression to use is the name of a variable -in your program. - -Variables in expressions are understood in the selected stack frame -(@pxref{Selection, ,Selecting a frame}); they must be either: - -@itemize @bullet -@item -global (or file-static) -@end itemize - -@noindent or - -@itemize @bullet -@item -visible according to the scope rules of the -programming language from the point of execution in that frame -@end itemize - -@noindent This means that in the function - -@example -foo (a) - int a; -@{ - bar (a); - @{ - int b = test (); - bar (b); - @} -@} -@end example - -@noindent -you can examine and use the variable @code{a} whenever your program is -executing within the function @code{foo}, but you can only use or -examine the variable @code{b} while your program is executing inside -the block where @code{b} is declared. - -@cindex variable name conflict -There is an exception: you can refer to a variable or function whose -scope is a single source file even if the current execution point is not -in this file. But it is possible to have more than one such variable or -function with the same name (in different source files). If that -happens, referring to that name has unpredictable effects. If you wish, -you can specify a static variable in a particular function or file, -using the colon-colon notation: - -@cindex colon-colon, context for variables/functions -@iftex -@c info cannot cope with a :: index entry, but why deprive hard copy readers? -@cindex @code{::}, context for variables/functions -@end iftex -@example -@var{file}::@var{variable} -@var{function}::@var{variable} -@end example - -@noindent -Here @var{file} or @var{function} is the name of the context for the -static @var{variable}. In the case of file names, you can use quotes to -make sure @value{GDBN} parses the file name as a single word---for example, -to print a global value of @code{x} defined in @file{f2.c}: - -@example -(@value{GDBP}) p 'f2.c'::x -@end example - -@cindex C@t{++} scope resolution -This use of @samp{::} is very rarely in conflict with the very similar -use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++} -scope resolution operator in @value{GDBN} expressions. -@c FIXME: Um, so what happens in one of those rare cases where it's in -@c conflict?? --mew - -@cindex wrong values -@cindex variable values, wrong -@quotation -@emph{Warning:} Occasionally, a local variable may appear to have the -wrong value at certain points in a function---just after entry to a new -scope, and just before exit. -@end quotation -You may see this problem when you are stepping by machine instructions. -This is because, on most machines, it takes more than one instruction to -set up a stack frame (including local variable definitions); if you are -stepping by machine instructions, variables may appear to have the wrong -values until the stack frame is completely built. On exit, it usually -also takes more than one machine instruction to destroy a stack frame; -after you begin stepping through that group of instructions, local -variable definitions may be gone. - -This may also happen when the compiler does significant optimizations. -To be sure of always seeing accurate values, turn off all optimization -when compiling. - -@cindex ``No symbol "foo" in current context'' -Another possible effect of compiler optimizations is to optimize -unused variables out of existence, or assign variables to registers (as -opposed to memory addresses). Depending on the support for such cases -offered by the debug info format used by the compiler, @value{GDBN} -might not be able to display values for such local variables. If that -happens, @value{GDBN} will print a message like this: - -@example -No symbol "foo" in current context. -@end example - -To solve such problems, either recompile without optimizations, or use a -different debug info format, if the compiler supports several such -formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler usually -supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info -in a format that is superior to formats such as COFF. You may be able -to use DWARF2 (@samp{-gdwarf-2}), which is also an effective form for -debug info. See @ref{Debugging Options,,Options for Debugging Your -Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more -information. - - -@node Arrays -@section Artificial arrays - -@cindex artificial array -@kindex @@@r{, referencing memory as an array} -It is often useful to print out several successive objects of the -same type in memory; a section of an array, or an array of -dynamically determined size for which only a pointer exists in the -program. - -You can do this by referring to a contiguous span of memory as an -@dfn{artificial array}, using the binary operator @samp{@@}. The left -operand of @samp{@@} should be the first element of the desired array -and be an individual object. The right operand should be the desired length -of the array. The result is an array value whose elements are all of -the type of the left argument. The first element is actually the left -argument; the second element comes from bytes of memory immediately -following those that hold the first element, and so on. Here is an -example. If a program says - -@example -int *array = (int *) malloc (len * sizeof (int)); -@end example - -@noindent -you can print the contents of @code{array} with - -@example -p *array@@len -@end example - -The left operand of @samp{@@} must reside in memory. Array values made -with @samp{@@} in this way behave just like other arrays in terms of -subscripting, and are coerced to pointers when used in expressions. -Artificial arrays most often appear in expressions via the value history -(@pxref{Value History, ,Value history}), after printing one out. - -Another way to create an artificial array is to use a cast. -This re-interprets a value as if it were an array. -The value need not be in memory: -@example -(@value{GDBP}) p/x (short[2])0x12345678 -$1 = @{0x1234, 0x5678@} -@end example - -As a convenience, if you leave the array length out (as in -@samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill -the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}: -@example -(@value{GDBP}) p/x (short[])0x12345678 -$2 = @{0x1234, 0x5678@} -@end example - -Sometimes the artificial array mechanism is not quite enough; in -moderately complex data structures, the elements of interest may not -actually be adjacent---for example, if you are interested in the values -of pointers in an array. One useful work-around in this situation is -to use a convenience variable (@pxref{Convenience Vars, ,Convenience -variables}) as a counter in an expression that prints the first -interesting value, and then repeat that expression via @key{RET}. For -instance, suppose you have an array @code{dtab} of pointers to -structures, and you are interested in the values of a field @code{fv} -in each structure. Here is an example of what you might type: - -@example -set $i = 0 -p dtab[$i++]->fv -@key{RET} -@key{RET} -@dots{} -@end example - -@node Output Formats -@section Output formats - -@cindex formatted output -@cindex output formats -By default, @value{GDBN} prints a value according to its data type. Sometimes -this is not what you want. For example, you might want to print a number -in hex, or a pointer in decimal. Or you might want to view data in memory -at a certain address as a character string or as an instruction. To do -these things, specify an @dfn{output format} when you print a value. - -The simplest use of output formats is to say how to print a value -already computed. This is done by starting the arguments of the -@code{print} command with a slash and a format letter. The format -letters supported are: - -@table @code -@item x -Regard the bits of the value as an integer, and print the integer in -hexadecimal. - -@item d -Print as integer in signed decimal. - -@item u -Print as integer in unsigned decimal. - -@item o -Print as integer in octal. - -@item t -Print as integer in binary. The letter @samp{t} stands for ``two''. -@footnote{@samp{b} cannot be used because these format letters are also -used with the @code{x} command, where @samp{b} stands for ``byte''; -see @ref{Memory,,Examining memory}.} - -@item a -@cindex unknown address, locating -@cindex locate address -Print as an address, both absolute in hexadecimal and as an offset from -the nearest preceding symbol. You can use this format used to discover -where (in what function) an unknown address is located: - -@example -(@value{GDBP}) p/a 0x54320 -$3 = 0x54320 <_initialize_vx+396> -@end example - -@noindent -The command @code{info symbol 0x54320} yields similar results. -@xref{Symbols, info symbol}. - -@item c -Regard as an integer and print it as a character constant. - -@item f -Regard the bits of the value as a floating point number and print -using typical floating point syntax. -@end table - -For example, to print the program counter in hex (@pxref{Registers}), type - -@example -p/x $pc -@end example - -@noindent -Note that no space is required before the slash; this is because command -names in @value{GDBN} cannot contain a slash. - -To reprint the last value in the value history with a different format, -you can use the @code{print} command with just a format and no -expression. For example, @samp{p/x} reprints the last value in hex. - -@node Memory -@section Examining memory - -You can use the command @code{x} (for ``examine'') to examine memory in -any of several formats, independently of your program's data types. - -@cindex examining memory -@table @code -@kindex x @r{(examine memory)} -@item x/@var{nfu} @var{addr} -@itemx x @var{addr} -@itemx x -Use the @code{x} command to examine memory. -@end table - -@var{n}, @var{f}, and @var{u} are all optional parameters that specify how -much memory to display and how to format it; @var{addr} is an -expression giving the address where you want to start displaying memory. -If you use defaults for @var{nfu}, you need not type the slash @samp{/}. -Several commands set convenient defaults for @var{addr}. - -@table @r -@item @var{n}, the repeat count -The repeat count is a decimal integer; the default is 1. It specifies -how much memory (counting by units @var{u}) to display. -@c This really is **decimal**; unaffected by 'set radix' as of GDB -@c 4.1.2. - -@item @var{f}, the display format -The display format is one of the formats used by @code{print}, -@samp{s} (null-terminated string), or @samp{i} (machine instruction). -The default is @samp{x} (hexadecimal) initially. -The default changes each time you use either @code{x} or @code{print}. - -@item @var{u}, the unit size -The unit size is any of - -@table @code -@item b -Bytes. -@item h -Halfwords (two bytes). -@item w -Words (four bytes). This is the initial default. -@item g -Giant words (eight bytes). -@end table - -Each time you specify a unit size with @code{x}, that size becomes the -default unit the next time you use @code{x}. (For the @samp{s} and -@samp{i} formats, the unit size is ignored and is normally not written.) - -@item @var{addr}, starting display address -@var{addr} is the address where you want @value{GDBN} to begin displaying -memory. The expression need not have a pointer value (though it may); -it is always interpreted as an integer address of a byte of memory. -@xref{Expressions, ,Expressions}, for more information on expressions. The default for -@var{addr} is usually just after the last address examined---but several -other commands also set the default address: @code{info breakpoints} (to -the address of the last breakpoint listed), @code{info line} (to the -starting address of a line), and @code{print} (if you use it to display -a value from memory). -@end table - -For example, @samp{x/3uh 0x54320} is a request to display three halfwords -(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}), -starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four -words (@samp{w}) of memory above the stack pointer (here, @samp{$sp}; -@pxref{Registers, ,Registers}) in hexadecimal (@samp{x}). - -Since the letters indicating unit sizes are all distinct from the -letters specifying output formats, you do not have to remember whether -unit size or format comes first; either order works. The output -specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. -(However, the count @var{n} must come first; @samp{wx4} does not work.) - -Even though the unit size @var{u} is ignored for the formats @samp{s} -and @samp{i}, you might still want to use a count @var{n}; for example, -@samp{3i} specifies that you want to see three machine instructions, -including any operands. The command @code{disassemble} gives an -alternative way of inspecting machine instructions; see @ref{Machine -Code,,Source and machine code}. - -All the defaults for the arguments to @code{x} are designed to make it -easy to continue scanning memory with minimal specifications each time -you use @code{x}. For example, after you have inspected three machine -instructions with @samp{x/3i @var{addr}}, you can inspect the next seven -with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command, -the repeat count @var{n} is used again; the other arguments default as -for successive uses of @code{x}. - -@cindex @code{$_}, @code{$__}, and value history -The addresses and contents printed by the @code{x} command are not saved -in the value history because there is often too much of them and they -would get in the way. Instead, @value{GDBN} makes these values available for -subsequent use in expressions as values of the convenience variables -@code{$_} and @code{$__}. After an @code{x} command, the last address -examined is available for use in expressions in the convenience variable -@code{$_}. The contents of that address, as examined, are available in -the convenience variable @code{$__}. - -If the @code{x} command has a repeat count, the address and contents saved -are from the last memory unit printed; this is not the same as the last -address printed if several units were printed on the last line of output. - -@node Auto Display -@section Automatic display -@cindex automatic display -@cindex display of expressions - -If you find that you want to print the value of an expression frequently -(to see how it changes), you might want to add it to the @dfn{automatic -display list} so that @value{GDBN} prints its value each time your program stops. -Each expression added to the list is given a number to identify it; -to remove an expression from the list, you specify that number. -The automatic display looks like this: - -@example -2: foo = 38 -3: bar[5] = (struct hack *) 0x3804 -@end example - -@noindent -This display shows item numbers, expressions and their current values. As with -displays you request manually using @code{x} or @code{print}, you can -specify the output format you prefer; in fact, @code{display} decides -whether to use @code{print} or @code{x} depending on how elaborate your -format specification is---it uses @code{x} if you specify a unit size, -or one of the two formats (@samp{i} and @samp{s}) that are only -supported by @code{x}; otherwise it uses @code{print}. - -@table @code -@kindex display -@item display @var{expr} -Add the expression @var{expr} to the list of expressions to display -each time your program stops. @xref{Expressions, ,Expressions}. - -@code{display} does not repeat if you press @key{RET} again after using it. - -@item display/@var{fmt} @var{expr} -For @var{fmt} specifying only a display format and not a size or -count, add the expression @var{expr} to the auto-display list but -arrange to display it each time in the specified format @var{fmt}. -@xref{Output Formats,,Output formats}. - -@item display/@var{fmt} @var{addr} -For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a -number of units, add the expression @var{addr} as a memory address to -be examined each time your program stops. Examining means in effect -doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}. -@end table - -For example, @samp{display/i $pc} can be helpful, to see the machine -instruction about to be executed each time execution stops (@samp{$pc} -is a common name for the program counter; @pxref{Registers, ,Registers}). - -@table @code -@kindex delete display -@kindex undisplay -@item undisplay @var{dnums}@dots{} -@itemx delete display @var{dnums}@dots{} -Remove item numbers @var{dnums} from the list of expressions to display. - -@code{undisplay} does not repeat if you press @key{RET} after using it. -(Otherwise you would just get the error @samp{No display number @dots{}}.) - -@kindex disable display -@item disable display @var{dnums}@dots{} -Disable the display of item numbers @var{dnums}. A disabled display -item is not printed automatically, but is not forgotten. It may be -enabled again later. - -@kindex enable display -@item enable display @var{dnums}@dots{} -Enable display of item numbers @var{dnums}. It becomes effective once -again in auto display of its expression, until you specify otherwise. - -@item display -Display the current values of the expressions on the list, just as is -done when your program stops. - -@kindex info display -@item info display -Print the list of expressions previously set up to display -automatically, each one with its item number, but without showing the -values. This includes disabled expressions, which are marked as such. -It also includes expressions which would not be displayed right now -because they refer to automatic variables not currently available. -@end table - -If a display expression refers to local variables, then it does not make -sense outside the lexical context for which it was set up. Such an -expression is disabled when execution enters a context where one of its -variables is not defined. For example, if you give the command -@code{display last_char} while inside a function with an argument -@code{last_char}, @value{GDBN} displays this argument while your program -continues to stop inside that function. When it stops elsewhere---where -there is no variable @code{last_char}---the display is disabled -automatically. The next time your program stops where @code{last_char} -is meaningful, you can enable the display expression once again. - -@node Print Settings -@section Print settings - -@cindex format options -@cindex print settings -@value{GDBN} provides the following ways to control how arrays, structures, -and symbols are printed. - -@noindent -These settings are useful for debugging programs in any language: - -@table @code -@kindex set print address -@item set print address -@itemx set print address on -@value{GDBN} prints memory addresses showing the location of stack -traces, structure values, pointer values, breakpoints, and so forth, -even when it also displays the contents of those addresses. The default -is @code{on}. For example, this is what a stack frame display looks like with -@code{set print address on}: - -@smallexample -@group -(@value{GDBP}) f -#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") - at input.c:530 -530 if (lquote != def_lquote) -@end group -@end smallexample - -@item set print address off -Do not print addresses when displaying their contents. For example, -this is the same stack frame displayed with @code{set print address off}: - -@smallexample -@group -(@value{GDBP}) set print addr off -(@value{GDBP}) f -#0 set_quotes (lq="<<", rq=">>") at input.c:530 -530 if (lquote != def_lquote) -@end group -@end smallexample - -You can use @samp{set print address off} to eliminate all machine -dependent displays from the @value{GDBN} interface. For example, with -@code{print address off}, you should get the same text for backtraces on -all machines---whether or not they involve pointer arguments. - -@kindex show print address -@item show print address -Show whether or not addresses are to be printed. -@end table - -When @value{GDBN} prints a symbolic address, it normally prints the -closest earlier symbol plus an offset. If that symbol does not uniquely -identify the address (for example, it is a name whose scope is a single -source file), you may need to clarify. One way to do this is with -@code{info line}, for example @samp{info line *0x4537}. Alternately, -you can set @value{GDBN} to print the source file and line number when -it prints a symbolic address: - -@table @code -@kindex set print symbol-filename -@item set print symbol-filename on -Tell @value{GDBN} to print the source file name and line number of a -symbol in the symbolic form of an address. - -@item set print symbol-filename off -Do not print source file name and line number of a symbol. This is the -default. - -@kindex show print symbol-filename -@item show print symbol-filename -Show whether or not @value{GDBN} will print the source file name and -line number of a symbol in the symbolic form of an address. -@end table - -Another situation where it is helpful to show symbol filenames and line -numbers is when disassembling code; @value{GDBN} shows you the line -number and source file that corresponds to each instruction. - -Also, you may wish to see the symbolic form only if the address being -printed is reasonably close to the closest earlier symbol: - -@table @code -@kindex set print max-symbolic-offset -@item set print max-symbolic-offset @var{max-offset} -Tell @value{GDBN} to only display the symbolic form of an address if the -offset between the closest earlier symbol and the address is less than -@var{max-offset}. The default is 0, which tells @value{GDBN} -to always print the symbolic form of an address if any symbol precedes it. - -@kindex show print max-symbolic-offset -@item show print max-symbolic-offset -Ask how large the maximum offset is that @value{GDBN} prints in a -symbolic address. -@end table - -@cindex wild pointer, interpreting -@cindex pointer, finding referent -If you have a pointer and you are not sure where it points, try -@samp{set print symbol-filename on}. Then you can determine the name -and source file location of the variable where it points, using -@samp{p/a @var{pointer}}. This interprets the address in symbolic form. -For example, here @value{GDBN} shows that a variable @code{ptt} points -at another variable @code{t}, defined in @file{hi2.c}: - -@example -(@value{GDBP}) set print symbol-filename on -(@value{GDBP}) p/a ptt -$4 = 0xe008 <t in hi2.c> -@end example - -@quotation -@emph{Warning:} For pointers that point to a local variable, @samp{p/a} -does not show the symbol name and filename of the referent, even with -the appropriate @code{set print} options turned on. -@end quotation - -Other settings control how different kinds of objects are printed: - -@table @code -@kindex set print array -@item set print array -@itemx set print array on -Pretty print arrays. This format is more convenient to read, -but uses more space. The default is off. - -@item set print array off -Return to compressed format for arrays. - -@kindex show print array -@item show print array -Show whether compressed or pretty format is selected for displaying -arrays. - -@kindex set print elements -@item set print elements @var{number-of-elements} -Set a limit on how many elements of an array @value{GDBN} will print. -If @value{GDBN} is printing a large array, it stops printing after it has -printed the number of elements set by the @code{set print elements} command. -This limit also applies to the display of strings. -When @value{GDBN} starts, this limit is set to 200. -Setting @var{number-of-elements} to zero means that the printing is unlimited. - -@kindex show print elements -@item show print elements -Display the number of elements of a large array that @value{GDBN} will print. -If the number is 0, then the printing is unlimited. - -@kindex set print null-stop -@item set print null-stop -Cause @value{GDBN} to stop printing the characters of an array when the first -@sc{null} is encountered. This is useful when large arrays actually -contain only short strings. -The default is off. - -@kindex set print pretty -@item set print pretty on -Cause @value{GDBN} to print structures in an indented format with one member -per line, like this: - -@smallexample -@group -$1 = @{ - next = 0x0, - flags = @{ - sweet = 1, - sour = 1 - @}, - meat = 0x54 "Pork" -@} -@end group -@end smallexample - -@item set print pretty off -Cause @value{GDBN} to print structures in a compact format, like this: - -@smallexample -@group -$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \ -meat = 0x54 "Pork"@} -@end group -@end smallexample - -@noindent -This is the default format. - -@kindex show print pretty -@item show print pretty -Show which format @value{GDBN} is using to print structures. - -@kindex set print sevenbit-strings -@item set print sevenbit-strings on -Print using only seven-bit characters; if this option is set, -@value{GDBN} displays any eight-bit characters (in strings or -character values) using the notation @code{\}@var{nnn}. This setting is -best if you are working in English (@sc{ascii}) and you use the -high-order bit of characters as a marker or ``meta'' bit. - -@item set print sevenbit-strings off -Print full eight-bit characters. This allows the use of more -international character sets, and is the default. - -@kindex show print sevenbit-strings -@item show print sevenbit-strings -Show whether or not @value{GDBN} is printing only seven-bit characters. - -@kindex set print union -@item set print union on -Tell @value{GDBN} to print unions which are contained in structures. This -is the default setting. - -@item set print union off -Tell @value{GDBN} not to print unions which are contained in structures. - -@kindex show print union -@item show print union -Ask @value{GDBN} whether or not it will print unions which are contained in -structures. - -For example, given the declarations - -@smallexample -typedef enum @{Tree, Bug@} Species; -typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms; -typedef enum @{Caterpillar, Cocoon, Butterfly@} - Bug_forms; - -struct thing @{ - Species it; - union @{ - Tree_forms tree; - Bug_forms bug; - @} form; -@}; - -struct thing foo = @{Tree, @{Acorn@}@}; -@end smallexample - -@noindent -with @code{set print union on} in effect @samp{p foo} would print - -@smallexample -$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@} -@end smallexample - -@noindent -and with @code{set print union off} in effect it would print - -@smallexample -$1 = @{it = Tree, form = @{...@}@} -@end smallexample -@end table - -@need 1000 -@noindent -These settings are of interest when debugging C@t{++} programs: - -@table @code -@cindex demangling -@kindex set print demangle -@item set print demangle -@itemx set print demangle on -Print C@t{++} names in their source form rather than in the encoded -(``mangled'') form passed to the assembler and linker for type-safe -linkage. The default is on. - -@kindex show print demangle -@item show print demangle -Show whether C@t{++} names are printed in mangled or demangled form. - -@kindex set print asm-demangle -@item set print asm-demangle -@itemx set print asm-demangle on -Print C@t{++} names in their source form rather than their mangled form, even -in assembler code printouts such as instruction disassemblies. -The default is off. - -@kindex show print asm-demangle -@item show print asm-demangle -Show whether C@t{++} names in assembly listings are printed in mangled -or demangled form. - -@kindex set demangle-style -@cindex C@t{++} symbol decoding style -@cindex symbol decoding style, C@t{++} -@item set demangle-style @var{style} -Choose among several encoding schemes used by different compilers to -represent C@t{++} names. The choices for @var{style} are currently: - -@table @code -@item auto -Allow @value{GDBN} to choose a decoding style by inspecting your program. - -@item gnu -Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm. -This is the default. - -@item hp -Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm. - -@item lucid -Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm. - -@item arm -Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}. -@strong{Warning:} this setting alone is not sufficient to allow -debugging @code{cfront}-generated executables. @value{GDBN} would -require further enhancement to permit that. - -@end table -If you omit @var{style}, you will see a list of possible formats. - -@kindex show demangle-style -@item show demangle-style -Display the encoding style currently in use for decoding C@t{++} symbols. - -@kindex set print object -@item set print object -@itemx set print object on -When displaying a pointer to an object, identify the @emph{actual} -(derived) type of the object rather than the @emph{declared} type, using -the virtual function table. - -@item set print object off -Display only the declared type of objects, without reference to the -virtual function table. This is the default setting. - -@kindex show print object -@item show print object -Show whether actual, or declared, object types are displayed. - -@kindex set print static-members -@item set print static-members -@itemx set print static-members on -Print static members when displaying a C@t{++} object. The default is on. - -@item set print static-members off -Do not print static members when displaying a C@t{++} object. - -@kindex show print static-members -@item show print static-members -Show whether C@t{++} static members are printed, or not. - -@c These don't work with HP ANSI C++ yet. -@kindex set print vtbl -@item set print vtbl -@itemx set print vtbl on -Pretty print C@t{++} virtual function tables. The default is off. -(The @code{vtbl} commands do not work on programs compiled with the HP -ANSI C@t{++} compiler (@code{aCC}).) - -@item set print vtbl off -Do not pretty print C@t{++} virtual function tables. - -@kindex show print vtbl -@item show print vtbl -Show whether C@t{++} virtual function tables are pretty printed, or not. -@end table - -@node Value History -@section Value history - -@cindex value history -Values printed by the @code{print} command are saved in the @value{GDBN} -@dfn{value history}. This allows you to refer to them in other expressions. -Values are kept until the symbol table is re-read or discarded -(for example with the @code{file} or @code{symbol-file} commands). -When the symbol table changes, the value history is discarded, -since the values may contain pointers back to the types defined in the -symbol table. - -@cindex @code{$} -@cindex @code{$$} -@cindex history number -The values printed are given @dfn{history numbers} by which you can -refer to them. These are successive integers starting with one. -@code{print} shows you the history number assigned to a value by -printing @samp{$@var{num} = } before the value; here @var{num} is the -history number. - -To refer to any previous value, use @samp{$} followed by the value's -history number. The way @code{print} labels its output is designed to -remind you of this. Just @code{$} refers to the most recent value in -the history, and @code{$$} refers to the value before that. -@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2} -is the value just prior to @code{$$}, @code{$$1} is equivalent to -@code{$$}, and @code{$$0} is equivalent to @code{$}. - -For example, suppose you have just printed a pointer to a structure and -want to see the contents of the structure. It suffices to type - -@example -p *$ -@end example - -If you have a chain of structures where the component @code{next} points -to the next one, you can print the contents of the next one with this: - -@example -p *$.next -@end example - -@noindent -You can print successive links in the chain by repeating this -command---which you can do by just typing @key{RET}. - -Note that the history records values, not expressions. If the value of -@code{x} is 4 and you type these commands: - -@example -print x -set x=5 -@end example - -@noindent -then the value recorded in the value history by the @code{print} command -remains 4 even though the value of @code{x} has changed. - -@table @code -@kindex show values -@item show values -Print the last ten values in the value history, with their item numbers. -This is like @samp{p@ $$9} repeated ten times, except that @code{show -values} does not change the history. - -@item show values @var{n} -Print ten history values centered on history item number @var{n}. - -@item show values + -Print ten history values just after the values last printed. If no more -values are available, @code{show values +} produces no display. -@end table - -Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the -same effect as @samp{show values +}. - -@node Convenience Vars -@section Convenience variables - -@cindex convenience variables -@value{GDBN} provides @dfn{convenience variables} that you can use within -@value{GDBN} to hold on to a value and refer to it later. These variables -exist entirely within @value{GDBN}; they are not part of your program, and -setting a convenience variable has no direct effect on further execution -of your program. That is why you can use them freely. - -Convenience variables are prefixed with @samp{$}. Any name preceded by -@samp{$} can be used for a convenience variable, unless it is one of -the predefined machine-specific register names (@pxref{Registers, ,Registers}). -(Value history references, in contrast, are @emph{numbers} preceded -by @samp{$}. @xref{Value History, ,Value history}.) - -You can save a value in a convenience variable with an assignment -expression, just as you would set a variable in your program. -For example: - -@example -set $foo = *object_ptr -@end example - -@noindent -would save in @code{$foo} the value contained in the object pointed to by -@code{object_ptr}. - -Using a convenience variable for the first time creates it, but its -value is @code{void} until you assign a new value. You can alter the -value with another assignment at any time. - -Convenience variables have no fixed types. You can assign a convenience -variable any type of value, including structures and arrays, even if -that variable already has a value of a different type. The convenience -variable, when used as an expression, has the type of its current value. - -@table @code -@kindex show convenience -@item show convenience -Print a list of convenience variables used so far, and their values. -Abbreviated @code{show conv}. -@end table - -One of the ways to use a convenience variable is as a counter to be -incremented or a pointer to be advanced. For example, to print -a field from successive elements of an array of structures: - -@example -set $i = 0 -print bar[$i++]->contents -@end example - -@noindent -Repeat that command by typing @key{RET}. - -Some convenience variables are created automatically by @value{GDBN} and given -values likely to be useful. - -@table @code -@vindex $_@r{, convenience variable} -@item $_ -The variable @code{$_} is automatically set by the @code{x} command to -the last address examined (@pxref{Memory, ,Examining memory}). Other -commands which provide a default address for @code{x} to examine also -set @code{$_} to that address; these commands include @code{info line} -and @code{info breakpoint}. The type of @code{$_} is @code{void *} -except when set by the @code{x} command, in which case it is a pointer -to the type of @code{$__}. - -@vindex $__@r{, convenience variable} -@item $__ -The variable @code{$__} is automatically set by the @code{x} command -to the value found in the last address examined. Its type is chosen -to match the format in which the data was printed. - -@item $_exitcode -@vindex $_exitcode@r{, convenience variable} -The variable @code{$_exitcode} is automatically set to the exit code when -the program being debugged terminates. -@end table - -On HP-UX systems, if you refer to a function or variable name that -begins with a dollar sign, @value{GDBN} searches for a user or system -name first, before it searches for a convenience variable. - -@node Registers -@section Registers - -@cindex registers -You can refer to machine register contents, in expressions, as variables -with names starting with @samp{$}. The names of registers are different -for each machine; use @code{info registers} to see the names used on -your machine. - -@table @code -@kindex info registers -@item info registers -Print the names and values of all registers except floating-point -registers (in the selected stack frame). - -@kindex info all-registers -@cindex floating point registers -@item info all-registers -Print the names and values of all registers, including floating-point -registers. - -@item info registers @var{regname} @dots{} -Print the @dfn{relativized} value of each specified register @var{regname}. -As discussed in detail below, register values are normally relative to -the selected stack frame. @var{regname} may be any register name valid on -the machine you are using, with or without the initial @samp{$}. -@end table - -@value{GDBN} has four ``standard'' register names that are available (in -expressions) on most machines---whenever they do not conflict with an -architecture's canonical mnemonics for registers. The register names -@code{$pc} and @code{$sp} are used for the program counter register and -the stack pointer. @code{$fp} is used for a register that contains a -pointer to the current stack frame, and @code{$ps} is used for a -register that contains the processor status. For example, -you could print the program counter in hex with - -@example -p/x $pc -@end example - -@noindent -or print the instruction to be executed next with - -@example -x/i $pc -@end example - -@noindent -or add four to the stack pointer@footnote{This is a way of removing -one word from the stack, on machines where stacks grow downward in -memory (most machines, nowadays). This assumes that the innermost -stack frame is selected; setting @code{$sp} is not allowed when other -stack frames are selected. To pop entire frames off the stack, -regardless of machine architecture, use @code{return}; -see @ref{Returning, ,Returning from a function}.} with - -@example -set $sp += 4 -@end example - -Whenever possible, these four standard register names are available on -your machine even though the machine has different canonical mnemonics, -so long as there is no conflict. The @code{info registers} command -shows the canonical names. For example, on the SPARC, @code{info -registers} displays the processor status register as @code{$psr} but you -can also refer to it as @code{$ps}; and on x86-based machines @code{$ps} -is an alias for the @sc{eflags} register. - -@value{GDBN} always considers the contents of an ordinary register as an -integer when the register is examined in this way. Some machines have -special registers which can hold nothing but floating point; these -registers are considered to have floating point values. There is no way -to refer to the contents of an ordinary register as floating point value -(although you can @emph{print} it as a floating point value with -@samp{print/f $@var{regname}}). - -Some registers have distinct ``raw'' and ``virtual'' data formats. This -means that the data format in which the register contents are saved by -the operating system is not the same one that your program normally -sees. For example, the registers of the 68881 floating point -coprocessor are always saved in ``extended'' (raw) format, but all C -programs expect to work with ``double'' (virtual) format. In such -cases, @value{GDBN} normally works with the virtual format only (the format -that makes sense for your program), but the @code{info registers} command -prints the data in both formats. - -Normally, register values are relative to the selected stack frame -(@pxref{Selection, ,Selecting a frame}). This means that you get the -value that the register would contain if all stack frames farther in -were exited and their saved registers restored. In order to see the -true contents of hardware registers, you must select the innermost -frame (with @samp{frame 0}). - -However, @value{GDBN} must deduce where registers are saved, from the machine -code generated by your compiler. If some registers are not saved, or if -@value{GDBN} is unable to locate the saved registers, the selected stack -frame makes no difference. - -@node Floating Point Hardware -@section Floating point hardware -@cindex floating point - -Depending on the configuration, @value{GDBN} may be able to give -you more information about the status of the floating point hardware. - -@table @code -@kindex info float -@item info float -Display hardware-dependent information about the floating -point unit. The exact contents and layout vary depending on the -floating point chip. Currently, @samp{info float} is supported on -the ARM and x86 machines. -@end table - -@node Memory Region Attributes -@section Memory Region Attributes -@cindex memory region attributes - -@dfn{Memory region attributes} allow you to describe special handling -required by regions of your target's memory. @value{GDBN} uses attributes -to determine whether to allow certain types of memory accesses; whether to -use specific width accesses; and whether to cache target memory. - -Defined memory regions can be individually enabled and disabled. When a -memory region is disabled, @value{GDBN} uses the default attributes when -accessing memory in that region. Similarly, if no memory regions have -been defined, @value{GDBN} uses the default attributes when accessing -all memory. - -When a memory region is defined, it is given a number to identify it; -to enable, disable, or remove a memory region, you specify that number. - -@table @code -@kindex mem -@item mem @var{address1} @var{address2} @var{attributes}@dots{} -Define memory region bounded by @var{address1} and @var{address2} -with attributes @var{attributes}@dots{}. - -@kindex delete mem -@item delete mem @var{nums}@dots{} -Remove memory regions @var{nums}@dots{}. - -@kindex disable mem -@item disable mem @var{nums}@dots{} -Disable memory regions @var{nums}@dots{}. -A disabled memory region is not forgotten. -It may be enabled again later. - -@kindex enable mem -@item enable mem @var{nums}@dots{} -Enable memory regions @var{nums}@dots{}. - -@kindex info mem -@item info mem -Print a table of all defined memory regions, with the following columns -for each region. - -@table @emph -@item Memory Region Number -@item Enabled or Disabled. -Enabled memory regions are marked with @samp{y}. -Disabled memory regions are marked with @samp{n}. - -@item Lo Address -The address defining the inclusive lower bound of the memory region. - -@item Hi Address -The address defining the exclusive upper bound of the memory region. - -@item Attributes -The list of attributes set for this memory region. -@end table -@end table - - -@subsection Attributes - -@subsubsection Memory Access Mode -The access mode attributes set whether @value{GDBN} may make read or -write accesses to a memory region. - -While these attributes prevent @value{GDBN} from performing invalid -memory accesses, they do nothing to prevent the target system, I/O DMA, -etc. from accessing memory. - -@table @code -@item ro -Memory is read only. -@item wo -Memory is write only. -@item rw -Memory is read/write. This is the default. -@end table - -@subsubsection Memory Access Size -The acccess size attributes tells @value{GDBN} to use specific sized -accesses in the memory region. Often memory mapped device registers -require specific sized accesses. If no access size attribute is -specified, @value{GDBN} may use accesses of any size. - -@table @code -@item 8 -Use 8 bit memory accesses. -@item 16 -Use 16 bit memory accesses. -@item 32 -Use 32 bit memory accesses. -@item 64 -Use 64 bit memory accesses. -@end table - -@c @subsubsection Hardware/Software Breakpoints -@c The hardware/software breakpoint attributes set whether @value{GDBN} -@c will use hardware or software breakpoints for the internal breakpoints -@c used by the step, next, finish, until, etc. commands. -@c -@c @table @code -@c @item hwbreak -@c Always use hardware breakpoints -@c @item swbreak (default) -@c @end table - -@subsubsection Data Cache -The data cache attributes set whether @value{GDBN} will cache target -memory. While this generally improves performance by reducing debug -protocol overhead, it can lead to incorrect results because @value{GDBN} -does not know about volatile variables or memory mapped device -registers. - -@table @code -@item cache -Enable @value{GDBN} to cache target memory. -@item nocache -Disable @value{GDBN} from caching target memory. This is the default. -@end table - -@c @subsubsection Memory Write Verification -@c The memory write verification attributes set whether @value{GDBN} -@c will re-reads data after each write to verify the write was successful. -@c -@c @table @code -@c @item verify -@c @item noverify (default) -@c @end table - -@node Tracepoints -@chapter Tracepoints -@c This chapter is based on the documentation written by Michael -@c Snyder, David Taylor, Jim Blandy, and Elena Zannoni. - -@cindex tracepoints -In some applications, it is not feasible for the debugger to interrupt -the program's execution long enough for the developer to learn -anything helpful about its behavior. If the program's correctness -depends on its real-time behavior, delays introduced by a debugger -might cause the program to change its behavior drastically, or perhaps -fail, even when the code itself is correct. It is useful to be able -to observe the program's behavior without interrupting it. - -Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can -specify locations in the program, called @dfn{tracepoints}, and -arbitrary expressions to evaluate when those tracepoints are reached. -Later, using the @code{tfind} command, you can examine the values -those expressions had when the program hit the tracepoints. The -expressions may also denote objects in memory---structures or arrays, -for example---whose values @value{GDBN} should record; while visiting -a particular tracepoint, you may inspect those objects as if they were -in memory at that moment. However, because @value{GDBN} records these -values without interacting with you, it can do so quickly and -unobtrusively, hopefully not disturbing the program's behavior. - -The tracepoint facility is currently available only for remote -targets. @xref{Targets}. In addition, your remote target must know how -to collect trace data. This functionality is implemented in the remote -stub; however, none of the stubs distributed with @value{GDBN} support -tracepoints as of this writing. - -This chapter describes the tracepoint commands and features. - -@menu -* Set Tracepoints:: -* Analyze Collected Data:: -* Tracepoint Variables:: -@end menu - -@node Set Tracepoints -@section Commands to Set Tracepoints - -Before running such a @dfn{trace experiment}, an arbitrary number of -tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a -tracepoint has a number assigned to it by @value{GDBN}. Like with -breakpoints, tracepoint numbers are successive integers starting from -one. Many of the commands associated with tracepoints take the -tracepoint number as their argument, to identify which tracepoint to -work on. - -For each tracepoint, you can specify, in advance, some arbitrary set -of data that you want the target to collect in the trace buffer when -it hits that tracepoint. The collected data can include registers, -local variables, or global data. Later, you can use @value{GDBN} -commands to examine the values these data had at the time the -tracepoint was hit. - -This section describes commands to set tracepoints and associated -conditions and actions. - -@menu -* Create and Delete Tracepoints:: -* Enable and Disable Tracepoints:: -* Tracepoint Passcounts:: -* Tracepoint Actions:: -* Listing Tracepoints:: -* Starting and Stopping Trace Experiment:: -@end menu - -@node Create and Delete Tracepoints -@subsection Create and Delete Tracepoints - -@table @code -@cindex set tracepoint -@kindex trace -@item trace -The @code{trace} command is very similar to the @code{break} command. -Its argument can be a source line, a function name, or an address in -the target program. @xref{Set Breaks}. The @code{trace} command -defines a tracepoint, which is a point in the target program where the -debugger will briefly stop, collect some data, and then allow the -program to continue. Setting a tracepoint or changing its commands -doesn't take effect until the next @code{tstart} command; thus, you -cannot change the tracepoint attributes once a trace experiment is -running. - -Here are some examples of using the @code{trace} command: - -@smallexample -(@value{GDBP}) @b{trace foo.c:121} // a source file and line number - -(@value{GDBP}) @b{trace +2} // 2 lines forward - -(@value{GDBP}) @b{trace my_function} // first source line of function - -(@value{GDBP}) @b{trace *my_function} // EXACT start address of function - -(@value{GDBP}) @b{trace *0x2117c4} // an address -@end smallexample - -@noindent -You can abbreviate @code{trace} as @code{tr}. - -@vindex $tpnum -@cindex last tracepoint number -@cindex recent tracepoint number -@cindex tracepoint number -The convenience variable @code{$tpnum} records the tracepoint number -of the most recently set tracepoint. - -@kindex delete tracepoint -@cindex tracepoint deletion -@item delete tracepoint @r{[}@var{num}@r{]} -Permanently delete one or more tracepoints. With no argument, the -default is to delete all tracepoints. - -Examples: - -@smallexample -(@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints - -(@value{GDBP}) @b{delete trace} // remove all tracepoints -@end smallexample - -@noindent -You can abbreviate this command as @code{del tr}. -@end table - -@node Enable and Disable Tracepoints -@subsection Enable and Disable Tracepoints - -@table @code -@kindex disable tracepoint -@item disable tracepoint @r{[}@var{num}@r{]} -Disable tracepoint @var{num}, or all tracepoints if no argument -@var{num} is given. A disabled tracepoint will have no effect during -the next trace experiment, but it is not forgotten. You can re-enable -a disabled tracepoint using the @code{enable tracepoint} command. - -@kindex enable tracepoint -@item enable tracepoint @r{[}@var{num}@r{]} -Enable tracepoint @var{num}, or all tracepoints. The enabled -tracepoints will become effective the next time a trace experiment is -run. -@end table - -@node Tracepoint Passcounts -@subsection Tracepoint Passcounts - -@table @code -@kindex passcount -@cindex tracepoint pass count -@item passcount @r{[}@var{n} @r{[}@var{num}@r{]]} -Set the @dfn{passcount} of a tracepoint. The passcount is a way to -automatically stop a trace experiment. If a tracepoint's passcount is -@var{n}, then the trace experiment will be automatically stopped on -the @var{n}'th time that tracepoint is hit. If the tracepoint number -@var{num} is not specified, the @code{passcount} command sets the -passcount of the most recently defined tracepoint. If no passcount is -given, the trace experiment will run until stopped explicitly by the -user. - -Examples: - -@smallexample -(@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2} - -(@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.} -(@value{GDBP}) @b{trace foo} -(@value{GDBP}) @b{pass 3} -(@value{GDBP}) @b{trace bar} -(@value{GDBP}) @b{pass 2} -(@value{GDBP}) @b{trace baz} -(@value{GDBP}) @b{pass 1} // Stop tracing when foo has been -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has} -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times} -@exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.} -@end smallexample -@end table - -@node Tracepoint Actions -@subsection Tracepoint Action Lists - -@table @code -@kindex actions -@cindex tracepoint actions -@item actions @r{[}@var{num}@r{]} -This command will prompt for a list of actions to be taken when the -tracepoint is hit. If the tracepoint number @var{num} is not -specified, this command sets the actions for the one that was most -recently defined (so that you can define a tracepoint and then say -@code{actions} without bothering about its number). You specify the -actions themselves on the following lines, one action at a time, and -terminate the actions list with a line containing just @code{end}. So -far, the only defined actions are @code{collect} and -@code{while-stepping}. - -@cindex remove actions from a tracepoint -To remove all actions from a tracepoint, type @samp{actions @var{num}} -and follow it immediately with @samp{end}. - -@smallexample -(@value{GDBP}) @b{collect @var{data}} // collect some data - -(@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data - -(@value{GDBP}) @b{end} // signals the end of actions. -@end smallexample - -In the following example, the action list begins with @code{collect} -commands indicating the things to be collected when the tracepoint is -hit. Then, in order to single-step and collect additional data -following the tracepoint, a @code{while-stepping} command is used, -followed by the list of things to be collected while stepping. The -@code{while-stepping} command is terminated by its own separate -@code{end} command. Lastly, the action list is terminated by an -@code{end} command. - -@smallexample -(@value{GDBP}) @b{trace foo} -(@value{GDBP}) @b{actions} -Enter actions for tracepoint 1, one per line: -> collect bar,baz -> collect $regs -> while-stepping 12 - > collect $fp, $sp - > end -end -@end smallexample - -@kindex collect @r{(tracepoints)} -@item collect @var{expr1}, @var{expr2}, @dots{} -Collect values of the given expressions when the tracepoint is hit. -This command accepts a comma-separated list of any valid expressions. -In addition to global, static, or local variables, the following -special arguments are supported: - -@table @code -@item $regs -collect all registers - -@item $args -collect all function arguments - -@item $locals -collect all local variables. -@end table - -You can give several consecutive @code{collect} commands, each one -with a single argument, or one @code{collect} command with several -arguments separated by commas: the effect is the same. - -The command @code{info scope} (@pxref{Symbols, info scope}) is -particularly useful for figuring out what data to collect. - -@kindex while-stepping @r{(tracepoints)} -@item while-stepping @var{n} -Perform @var{n} single-step traces after the tracepoint, collecting -new data at each step. The @code{while-stepping} command is -followed by the list of what to collect while stepping (followed by -its own @code{end} command): - -@smallexample -> while-stepping 12 - > collect $regs, myglobal - > end -> -@end smallexample - -@noindent -You may abbreviate @code{while-stepping} as @code{ws} or -@code{stepping}. -@end table - -@node Listing Tracepoints -@subsection Listing Tracepoints - -@table @code -@kindex info tracepoints -@cindex information about tracepoints -@item info tracepoints @r{[}@var{num}@r{]} -Display information about the tracepoint @var{num}. If you don't specify -a tracepoint number, displays information about all the tracepoints -defined so far. For each tracepoint, the following information is -shown: - -@itemize @bullet -@item -its number -@item -whether it is enabled or disabled -@item -its address -@item -its passcount as given by the @code{passcount @var{n}} command -@item -its step count as given by the @code{while-stepping @var{n}} command -@item -where in the source files is the tracepoint set -@item -its action list as given by the @code{actions} command -@end itemize - -@smallexample -(@value{GDBP}) @b{info trace} -Num Enb Address PassC StepC What -1 y 0x002117c4 0 0 <gdb_asm> -2 y 0x0020dc64 0 0 in g_test at g_test.c:1375 -3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41 -(@value{GDBP}) -@end smallexample - -@noindent -This command can be abbreviated @code{info tp}. -@end table - -@node Starting and Stopping Trace Experiment -@subsection Starting and Stopping Trace Experiment - -@table @code -@kindex tstart -@cindex start a new trace experiment -@cindex collected data discarded -@item tstart -This command takes no arguments. It starts the trace experiment, and -begins collecting data. This has the side effect of discarding all -the data collected in the trace buffer during the previous trace -experiment. - -@kindex tstop -@cindex stop a running trace experiment -@item tstop -This command takes no arguments. It ends the trace experiment, and -stops collecting data. - -@strong{Note:} a trace experiment and data collection may stop -automatically if any tracepoint's passcount is reached -(@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full. - -@kindex tstatus -@cindex status of trace data collection -@cindex trace experiment, status of -@item tstatus -This command displays the status of the current trace data -collection. -@end table - -Here is an example of the commands we described so far: - -@smallexample -(@value{GDBP}) @b{trace gdb_c_test} -(@value{GDBP}) @b{actions} -Enter actions for tracepoint #1, one per line. -> collect $regs,$locals,$args -> while-stepping 11 - > collect $regs - > end -> end -(@value{GDBP}) @b{tstart} - [time passes @dots{}] -(@value{GDBP}) @b{tstop} -@end smallexample - - -@node Analyze Collected Data -@section Using the collected data - -After the tracepoint experiment ends, you use @value{GDBN} commands -for examining the trace data. The basic idea is that each tracepoint -collects a trace @dfn{snapshot} every time it is hit and another -snapshot every time it single-steps. All these snapshots are -consecutively numbered from zero and go into a buffer, and you can -examine them later. The way you examine them is to @dfn{focus} on a -specific trace snapshot. When the remote stub is focused on a trace -snapshot, it will respond to all @value{GDBN} requests for memory and -registers by reading from the buffer which belongs to that snapshot, -rather than from @emph{real} memory or registers of the program being -debugged. This means that @strong{all} @value{GDBN} commands -(@code{print}, @code{info registers}, @code{backtrace}, etc.) will -behave as if we were currently debugging the program state as it was -when the tracepoint occurred. Any requests for data that are not in -the buffer will fail. - -@menu -* tfind:: How to select a trace snapshot -* tdump:: How to display all data for a snapshot -* save-tracepoints:: How to save tracepoints for a future run -@end menu - -@node tfind -@subsection @code{tfind @var{n}} - -@kindex tfind -@cindex select trace snapshot -@cindex find trace snapshot -The basic command for selecting a trace snapshot from the buffer is -@code{tfind @var{n}}, which finds trace snapshot number @var{n}, -counting from zero. If no argument @var{n} is given, the next -snapshot is selected. - -Here are the various forms of using the @code{tfind} command. - -@table @code -@item tfind start -Find the first snapshot in the buffer. This is a synonym for -@code{tfind 0} (since 0 is the number of the first snapshot). - -@item tfind none -Stop debugging trace snapshots, resume @emph{live} debugging. - -@item tfind end -Same as @samp{tfind none}. - -@item tfind -No argument means find the next trace snapshot. - -@item tfind - -Find the previous trace snapshot before the current one. This permits -retracing earlier steps. - -@item tfind tracepoint @var{num} -Find the next snapshot associated with tracepoint @var{num}. Search -proceeds forward from the last examined trace snapshot. If no -argument @var{num} is given, it means find the next snapshot collected -for the same tracepoint as the current snapshot. - -@item tfind pc @var{addr} -Find the next snapshot associated with the value @var{addr} of the -program counter. Search proceeds forward from the last examined trace -snapshot. If no argument @var{addr} is given, it means find the next -snapshot with the same value of PC as the current snapshot. - -@item tfind outside @var{addr1}, @var{addr2} -Find the next snapshot whose PC is outside the given range of -addresses. - -@item tfind range @var{addr1}, @var{addr2} -Find the next snapshot whose PC is between @var{addr1} and -@var{addr2}. @c FIXME: Is the range inclusive or exclusive? - -@item tfind line @r{[}@var{file}:@r{]}@var{n} -Find the next snapshot associated with the source line @var{n}. If -the optional argument @var{file} is given, refer to line @var{n} in -that source file. Search proceeds forward from the last examined -trace snapshot. If no argument @var{n} is given, it means find the -next line other than the one currently being examined; thus saying -@code{tfind line} repeatedly can appear to have the same effect as -stepping from line to line in a @emph{live} debugging session. -@end table - -The default arguments for the @code{tfind} commands are specifically -designed to make it easy to scan through the trace buffer. For -instance, @code{tfind} with no argument selects the next trace -snapshot, and @code{tfind -} with no argument selects the previous -trace snapshot. So, by giving one @code{tfind} command, and then -simply hitting @key{RET} repeatedly you can examine all the trace -snapshots in order. Or, by saying @code{tfind -} and then hitting -@key{RET} repeatedly you can examine the snapshots in reverse order. -The @code{tfind line} command with no argument selects the snapshot -for the next source line executed. The @code{tfind pc} command with -no argument selects the next snapshot with the same program counter -(PC) as the current frame. The @code{tfind tracepoint} command with -no argument selects the next trace snapshot collected by the same -tracepoint as the current one. - -In addition to letting you scan through the trace buffer manually, -these commands make it easy to construct @value{GDBN} scripts that -scan through the trace buffer and print out whatever collected data -you are interested in. Thus, if we want to examine the PC, FP, and SP -registers from each trace frame in the buffer, we can say this: - -@smallexample -(@value{GDBP}) @b{tfind start} -(@value{GDBP}) @b{while ($trace_frame != -1)} -> printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \ - $trace_frame, $pc, $sp, $fp -> tfind -> end - -Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44 -Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44 -Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44 -Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44 -Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44 -Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44 -Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44 -Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44 -Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44 -Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44 -Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14 -@end smallexample - -Or, if we want to examine the variable @code{X} at each source line in -the buffer: - -@smallexample -(@value{GDBP}) @b{tfind start} -(@value{GDBP}) @b{while ($trace_frame != -1)} -> printf "Frame %d, X == %d\n", $trace_frame, X -> tfind line -> end - -Frame 0, X = 1 -Frame 7, X = 2 -Frame 13, X = 255 -@end smallexample - -@node tdump -@subsection @code{tdump} -@kindex tdump -@cindex dump all data collected at tracepoint -@cindex tracepoint data, display - -This command takes no arguments. It prints all the data collected at -the current trace snapshot. - -@smallexample -(@value{GDBP}) @b{trace 444} -(@value{GDBP}) @b{actions} -Enter actions for tracepoint #2, one per line: -> collect $regs, $locals, $args, gdb_long_test -> end - -(@value{GDBP}) @b{tstart} - -(@value{GDBP}) @b{tfind line 444} -#0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66) -at gdb_test.c:444 -444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", ) - -(@value{GDBP}) @b{tdump} -Data collected at tracepoint 2, trace frame 1: -d0 0xc4aa0085 -995491707 -d1 0x18 24 -d2 0x80 128 -d3 0x33 51 -d4 0x71aea3d 119204413 -d5 0x22 34 -d6 0xe0 224 -d7 0x380035 3670069 -a0 0x19e24a 1696330 -a1 0x3000668 50333288 -a2 0x100 256 -a3 0x322000 3284992 -a4 0x3000698 50333336 -a5 0x1ad3cc 1758156 -fp 0x30bf3c 0x30bf3c -sp 0x30bf34 0x30bf34 -ps 0x0 0 -pc 0x20b2c8 0x20b2c8 -fpcontrol 0x0 0 -fpstatus 0x0 0 -fpiaddr 0x0 0 -p = 0x20e5b4 "gdb-test" -p1 = (void *) 0x11 -p2 = (void *) 0x22 -p3 = (void *) 0x33 -p4 = (void *) 0x44 -p5 = (void *) 0x55 -p6 = (void *) 0x66 -gdb_long_test = 17 '\021' - -(@value{GDBP}) -@end smallexample - -@node save-tracepoints -@subsection @code{save-tracepoints @var{filename}} -@kindex save-tracepoints -@cindex save tracepoints for future sessions - -This command saves all current tracepoint definitions together with -their actions and passcounts, into a file @file{@var{filename}} -suitable for use in a later debugging session. To read the saved -tracepoint definitions, use the @code{source} command (@pxref{Command -Files}). - -@node Tracepoint Variables -@section Convenience Variables for Tracepoints -@cindex tracepoint variables -@cindex convenience variables for tracepoints - -@table @code -@vindex $trace_frame -@item (int) $trace_frame -The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no -snapshot is selected. - -@vindex $tracepoint -@item (int) $tracepoint -The tracepoint for the current trace snapshot. - -@vindex $trace_line -@item (int) $trace_line -The line number for the current trace snapshot. - -@vindex $trace_file -@item (char []) $trace_file -The source file for the current trace snapshot. - -@vindex $trace_func -@item (char []) $trace_func -The name of the function containing @code{$tracepoint}. -@end table - -Note: @code{$trace_file} is not suitable for use in @code{printf}, -use @code{output} instead. - -Here's a simple example of using these convenience variables for -stepping through all the trace snapshots and printing some of their -data. - -@smallexample -(@value{GDBP}) @b{tfind start} - -(@value{GDBP}) @b{while $trace_frame != -1} -> output $trace_file -> printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint -> tfind -> end -@end smallexample - -@node Overlays -@chapter Debugging Programs That Use Overlays -@cindex overlays - -If your program is too large to fit completely in your target system's -memory, you can sometimes use @dfn{overlays} to work around this -problem. @value{GDBN} provides some support for debugging programs that -use overlays. - -@menu -* How Overlays Work:: A general explanation of overlays. -* Overlay Commands:: Managing overlays in @value{GDBN}. -* Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are - mapped by asking the inferior. -* Overlay Sample Program:: A sample program using overlays. -@end menu - -@node How Overlays Work -@section How Overlays Work -@cindex mapped overlays -@cindex unmapped overlays -@cindex load address, overlay's -@cindex mapped address -@cindex overlay area - -Suppose you have a computer whose instruction address space is only 64 -kilobytes long, but which has much more memory which can be accessed by -other means: special instructions, segment registers, or memory -management hardware, for example. Suppose further that you want to -adapt a program which is larger than 64 kilobytes to run on this system. - -One solution is to identify modules of your program which are relatively -independent, and need not call each other directly; call these modules -@dfn{overlays}. Separate the overlays from the main program, and place -their machine code in the larger memory. Place your main program in -instruction memory, but leave at least enough space there to hold the -largest overlay as well. - -Now, to call a function located in an overlay, you must first copy that -overlay's machine code from the large memory into the space set aside -for it in the instruction memory, and then jump to its entry point -there. - -@c NB: In the below the mapped area's size is greater or equal to the -@c size of all overlays. This is intentional to remind the developer -@c that overlays don't necessarily need to be the same size. - -@example -@group - Data Instruction Larger -Address Space Address Space Address Space -+-----------+ +-----------+ +-----------+ -| | | | | | -+-----------+ +-----------+ +-----------+<-- overlay 1 -| program | | main | .----| overlay 1 | load address -| variables | | program | | +-----------+ -| and heap | | | | | | -+-----------+ | | | +-----------+<-- overlay 2 -| | +-----------+ | | | load address -+-----------+ | | | .-| overlay 2 | - | | | | | | - mapped --->+-----------+ | | +-----------+ - address | | | | | | - | overlay | <-' | | | - | area | <---' +-----------+<-- overlay 3 - | | <---. | | load address - +-----------+ `--| overlay 3 | - | | | | - +-----------+ | | - +-----------+ - | | - +-----------+ - - @anchor{A code overlay}A code overlay -@end group -@end example - -The diagram (@pxref{A code overlay}) shows a system with separate data -and instruction address spaces. To map an overlay, the program copies -its code from the larger address space to the instruction address space. -Since the overlays shown here all use the same mapped address, only one -may be mapped at a time. For a system with a single address space for -data and instructions, the diagram would be similar, except that the -program variables and heap would share an address space with the main -program and the overlay area. - -An overlay loaded into instruction memory and ready for use is called a -@dfn{mapped} overlay; its @dfn{mapped address} is its address in the -instruction memory. An overlay not present (or only partially present) -in instruction memory is called @dfn{unmapped}; its @dfn{load address} -is its address in the larger memory. The mapped address is also called -the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also -called the @dfn{load memory address}, or @dfn{LMA}. - -Unfortunately, overlays are not a completely transparent way to adapt a -program to limited instruction memory. They introduce a new set of -global constraints you must keep in mind as you design your program: - -@itemize @bullet - -@item -Before calling or returning to a function in an overlay, your program -must make sure that overlay is actually mapped. Otherwise, the call or -return will transfer control to the right address, but in the wrong -overlay, and your program will probably crash. - -@item -If the process of mapping an overlay is expensive on your system, you -will need to choose your overlays carefully to minimize their effect on -your program's performance. - -@item -The executable file you load onto your system must contain each -overlay's instructions, appearing at the overlay's load address, not its -mapped address. However, each overlay's instructions must be relocated -and its symbols defined as if the overlay were at its mapped address. -You can use GNU linker scripts to specify different load and relocation -addresses for pieces of your program; see @ref{Overlay Description,,, -ld.info, Using ld: the GNU linker}. - -@item -The procedure for loading executable files onto your system must be able -to load their contents into the larger address space as well as the -instruction and data spaces. - -@end itemize - -The overlay system described above is rather simple, and could be -improved in many ways: - -@itemize @bullet - -@item -If your system has suitable bank switch registers or memory management -hardware, you could use those facilities to make an overlay's load area -contents simply appear at their mapped address in instruction space. -This would probably be faster than copying the overlay to its mapped -area in the usual way. - -@item -If your overlays are small enough, you could set aside more than one -overlay area, and have more than one overlay mapped at a time. - -@item -You can use overlays to manage data, as well as instructions. In -general, data overlays are even less transparent to your design than -code overlays: whereas code overlays only require care when you call or -return to functions, data overlays require care every time you access -the data. Also, if you change the contents of a data overlay, you -must copy its contents back out to its load address before you can copy a -different data overlay into the same mapped area. - -@end itemize - - -@node Overlay Commands -@section Overlay Commands - -To use @value{GDBN}'s overlay support, each overlay in your program must -correspond to a separate section of the executable file. The section's -virtual memory address and load memory address must be the overlay's -mapped and load addresses. Identifying overlays with sections allows -@value{GDBN} to determine the appropriate address of a function or -variable, depending on whether the overlay is mapped or not. - -@value{GDBN}'s overlay commands all start with the word @code{overlay}; -you can abbreviate this as @code{ov} or @code{ovly}. The commands are: - -@table @code -@item overlay off -@kindex overlay off -Disable @value{GDBN}'s overlay support. When overlay support is -disabled, @value{GDBN} assumes that all functions and variables are -always present at their mapped addresses. By default, @value{GDBN}'s -overlay support is disabled. - -@item overlay manual -@kindex overlay manual -@cindex manual overlay debugging -Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN} -relies on you to tell it which overlays are mapped, and which are not, -using the @code{overlay map-overlay} and @code{overlay unmap-overlay} -commands described below. - -@item overlay map-overlay @var{overlay} -@itemx overlay map @var{overlay} -@kindex overlay map-overlay -@cindex map an overlay -Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must -be the name of the object file section containing the overlay. When an -overlay is mapped, @value{GDBN} assumes it can find the overlay's -functions and variables at their mapped addresses. @value{GDBN} assumes -that any other overlays whose mapped ranges overlap that of -@var{overlay} are now unmapped. - -@item overlay unmap-overlay @var{overlay} -@itemx overlay unmap @var{overlay} -@kindex overlay unmap-overlay -@cindex unmap an overlay -Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay} -must be the name of the object file section containing the overlay. -When an overlay is unmapped, @value{GDBN} assumes it can find the -overlay's functions and variables at their load addresses. - -@item overlay auto -@kindex overlay auto -Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN} -consults a data structure the overlay manager maintains in the inferior -to see which overlays are mapped. For details, see @ref{Automatic -Overlay Debugging}. - -@item overlay load-target -@itemx overlay load -@kindex overlay load-target -@cindex reloading the overlay table -Re-read the overlay table from the inferior. Normally, @value{GDBN} -re-reads the table @value{GDBN} automatically each time the inferior -stops, so this command should only be necessary if you have changed the -overlay mapping yourself using @value{GDBN}. This command is only -useful when using automatic overlay debugging. - -@item overlay list-overlays -@itemx overlay list -@cindex listing mapped overlays -Display a list of the overlays currently mapped, along with their mapped -addresses, load addresses, and sizes. - -@end table - -Normally, when @value{GDBN} prints a code address, it includes the name -of the function the address falls in: - -@example -(gdb) print main -$3 = @{int ()@} 0x11a0 <main> -@end example -@noindent -When overlay debugging is enabled, @value{GDBN} recognizes code in -unmapped overlays, and prints the names of unmapped functions with -asterisks around them. For example, if @code{foo} is a function in an -unmapped overlay, @value{GDBN} prints it this way: - -@example -(gdb) overlay list -No sections are mapped. -(gdb) print foo -$5 = @{int (int)@} 0x100000 <*foo*> -@end example -@noindent -When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's -name normally: - -@example -(gdb) overlay list -Section .ov.foo.text, loaded at 0x100000 - 0x100034, - mapped at 0x1016 - 0x104a -(gdb) print foo -$6 = @{int (int)@} 0x1016 <foo> -@end example - -When overlay debugging is enabled, @value{GDBN} can find the correct -address for functions and variables in an overlay, whether or not the -overlay is mapped. This allows most @value{GDBN} commands, like -@code{break} and @code{disassemble}, to work normally, even on unmapped -code. However, @value{GDBN}'s breakpoint support has some limitations: - -@itemize @bullet -@item -@cindex breakpoints in overlays -@cindex overlays, setting breakpoints in -You can set breakpoints in functions in unmapped overlays, as long as -@value{GDBN} can write to the overlay at its load address. -@item -@value{GDBN} can not set hardware or simulator-based breakpoints in -unmapped overlays. However, if you set a breakpoint at the end of your -overlay manager (and tell @value{GDBN} which overlays are now mapped, if -you are using manual overlay management), @value{GDBN} will re-set its -breakpoints properly. -@end itemize - - -@node Automatic Overlay Debugging -@section Automatic Overlay Debugging -@cindex automatic overlay debugging - -@value{GDBN} can automatically track which overlays are mapped and which -are not, given some simple co-operation from the overlay manager in the -inferior. If you enable automatic overlay debugging with the -@code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN} -looks in the inferior's memory for certain variables describing the -current state of the overlays. - -Here are the variables your overlay manager must define to support -@value{GDBN}'s automatic overlay debugging: - -@table @asis - -@item @code{_ovly_table}: -This variable must be an array of the following structures: - -@example -struct -@{ - /* The overlay's mapped address. */ - unsigned long vma; - - /* The size of the overlay, in bytes. */ - unsigned long size; - - /* The overlay's load address. */ - unsigned long lma; - - /* Non-zero if the overlay is currently mapped; - zero otherwise. */ - unsigned long mapped; -@} -@end example - -@item @code{_novlys}: -This variable must be a four-byte signed integer, holding the total -number of elements in @code{_ovly_table}. - -@end table - -To decide whether a particular overlay is mapped or not, @value{GDBN} -looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and -@code{lma} members equal the VMA and LMA of the overlay's section in the -executable file. When @value{GDBN} finds a matching entry, it consults -the entry's @code{mapped} member to determine whether the overlay is -currently mapped. - -In addition, your overlay manager may define a function called -@code{_ovly_debug_event}. If this function is defined, @value{GDBN} -will silently set a breakpoint there. If the overlay manager then -calls this function whenever it has changed the overlay table, this -will enable @value{GDBN} to accurately keep track of which overlays -are in program memory, and update any breakpoints that may be set -in overlays. This will allow breakpoints to work even if the -overlays are kept in ROM or other non-writable memory while they -are not being executed. - -@node Overlay Sample Program -@section Overlay Sample Program -@cindex overlay example program - -When linking a program which uses overlays, you must place the overlays -at their load addresses, while relocating them to run at their mapped -addresses. To do this, you must write a linker script (@pxref{Overlay -Description,,, ld.info, Using ld: the GNU linker}). Unfortunately, -since linker scripts are specific to a particular host system, target -architecture, and target memory layout, this manual cannot provide -portable sample code demonstrating @value{GDBN}'s overlay support. - -However, the @value{GDBN} source distribution does contain an overlaid -program, with linker scripts for a few systems, as part of its test -suite. The program consists of the following files from -@file{gdb/testsuite/gdb.base}: - -@table @file -@item overlays.c -The main program file. -@item ovlymgr.c -A simple overlay manager, used by @file{overlays.c}. -@item foo.c -@itemx bar.c -@itemx baz.c -@itemx grbx.c -Overlay modules, loaded and used by @file{overlays.c}. -@item d10v.ld -@itemx m32r.ld -Linker scripts for linking the test program on the @code{d10v-elf} -and @code{m32r-elf} targets. -@end table - -You can build the test program using the @code{d10v-elf} GCC -cross-compiler like this: - -@example -$ d10v-elf-gcc -g -c overlays.c -$ d10v-elf-gcc -g -c ovlymgr.c -$ d10v-elf-gcc -g -c foo.c -$ d10v-elf-gcc -g -c bar.c -$ d10v-elf-gcc -g -c baz.c -$ d10v-elf-gcc -g -c grbx.c -$ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \ - baz.o grbx.o -Wl,-Td10v.ld -o overlays -@end example - -The build process is identical for any other architecture, except that -you must substitute the appropriate compiler and linker script for the -target system for @code{d10v-elf-gcc} and @code{d10v.ld}. - - -@node Languages -@chapter Using @value{GDBN} with Different Languages -@cindex languages - -Although programming languages generally have common aspects, they are -rarely expressed in the same manner. For instance, in ANSI C, -dereferencing a pointer @code{p} is accomplished by @code{*p}, but in -Modula-2, it is accomplished by @code{p^}. Values can also be -represented (and displayed) differently. Hex numbers in C appear as -@samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}. - -@cindex working language -Language-specific information is built into @value{GDBN} for some languages, -allowing you to express operations like the above in your program's -native language, and allowing @value{GDBN} to output values in a manner -consistent with the syntax of your program's native language. The -language you use to build expressions is called the @dfn{working -language}. - -@menu -* Setting:: Switching between source languages -* Show:: Displaying the language -* Checks:: Type and range checks -* Support:: Supported languages -@end menu - -@node Setting -@section Switching between source languages - -There are two ways to control the working language---either have @value{GDBN} -set it automatically, or select it manually yourself. You can use the -@code{set language} command for either purpose. On startup, @value{GDBN} -defaults to setting the language automatically. The working language is -used to determine how expressions you type are interpreted, how values -are printed, etc. - -In addition to the working language, every source file that -@value{GDBN} knows about has its own working language. For some object -file formats, the compiler might indicate which language a particular -source file is in. However, most of the time @value{GDBN} infers the -language from the name of the file. The language of a source file -controls whether C@t{++} names are demangled---this way @code{backtrace} can -show each frame appropriately for its own language. There is no way to -set the language of a source file from within @value{GDBN}, but you can -set the language associated with a filename extension. @xref{Show, , -Displaying the language}. - -This is most commonly a problem when you use a program, such -as @code{cfront} or @code{f2c}, that generates C but is written in -another language. In that case, make the -program use @code{#line} directives in its C output; that way -@value{GDBN} will know the correct language of the source code of the original -program, and will display that source code, not the generated C code. - -@menu -* Filenames:: Filename extensions and languages. -* Manually:: Setting the working language manually -* Automatically:: Having @value{GDBN} infer the source language -@end menu - -@node Filenames -@subsection List of filename extensions and languages - -If a source file name ends in one of the following extensions, then -@value{GDBN} infers that its language is the one indicated. - -@table @file - -@item .c -C source file - -@item .C -@itemx .cc -@itemx .cp -@itemx .cpp -@itemx .cxx -@itemx .c++ -C@t{++} source file - -@item .f -@itemx .F -Fortran source file - -@item .ch -@itemx .c186 -@itemx .c286 -CHILL source file - -@item .mod -Modula-2 source file - -@item .s -@itemx .S -Assembler source file. This actually behaves almost like C, but -@value{GDBN} does not skip over function prologues when stepping. -@end table - -In addition, you may set the language associated with a filename -extension. @xref{Show, , Displaying the language}. - -@node Manually -@subsection Setting the working language - -If you allow @value{GDBN} to set the language automatically, -expressions are interpreted the same way in your debugging session and -your program. - -@kindex set language -If you wish, you may set the language manually. To do this, issue the -command @samp{set language @var{lang}}, where @var{lang} is the name of -a language, such as -@code{c} or @code{modula-2}. -For a list of the supported languages, type @samp{set language}. - -Setting the language manually prevents @value{GDBN} from updating the working -language automatically. This can lead to confusion if you try -to debug a program when the working language is not the same as the -source language, when an expression is acceptable to both -languages---but means different things. For instance, if the current -source file were written in C, and @value{GDBN} was parsing Modula-2, a -command such as: - -@example -print a = b + c -@end example - -@noindent -might not have the effect you intended. In C, this means to add -@code{b} and @code{c} and place the result in @code{a}. The result -printed would be the value of @code{a}. In Modula-2, this means to compare -@code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value. - -@node Automatically -@subsection Having @value{GDBN} infer the source language - -To have @value{GDBN} set the working language automatically, use -@samp{set language local} or @samp{set language auto}. @value{GDBN} -then infers the working language. That is, when your program stops in a -frame (usually by encountering a breakpoint), @value{GDBN} sets the -working language to the language recorded for the function in that -frame. If the language for a frame is unknown (that is, if the function -or block corresponding to the frame was defined in a source file that -does not have a recognized extension), the current working language is -not changed, and @value{GDBN} issues a warning. - -This may not seem necessary for most programs, which are written -entirely in one source language. However, program modules and libraries -written in one source language can be used by a main program written in -a different source language. Using @samp{set language auto} in this -case frees you from having to set the working language manually. - -@node Show -@section Displaying the language - -The following commands help you find out which language is the -working language, and also what language source files were written in. - -@kindex show language -@kindex info frame@r{, show the source language} -@kindex info source@r{, show the source language} -@table @code -@item show language -Display the current working language. This is the -language you can use with commands such as @code{print} to -build and compute expressions that may involve variables in your program. - -@item info frame -Display the source language for this frame. This language becomes the -working language if you use an identifier from this frame. -@xref{Frame Info, ,Information about a frame}, to identify the other -information listed here. - -@item info source -Display the source language of this source file. -@xref{Symbols, ,Examining the Symbol Table}, to identify the other -information listed here. -@end table - -In unusual circumstances, you may have source files with extensions -not in the standard list. You can then set the extension associated -with a language explicitly: - -@kindex set extension-language -@kindex info extensions -@table @code -@item set extension-language @var{.ext} @var{language} -Set source files with extension @var{.ext} to be assumed to be in -the source language @var{language}. - -@item info extensions -List all the filename extensions and the associated languages. -@end table - -@node Checks -@section Type and range checking - -@quotation -@emph{Warning:} In this release, the @value{GDBN} commands for type and range -checking are included, but they do not yet have any effect. This -section documents the intended facilities. -@end quotation -@c FIXME remove warning when type/range code added - -Some languages are designed to guard you against making seemingly common -errors through a series of compile- and run-time checks. These include -checking the type of arguments to functions and operators, and making -sure mathematical overflows are caught at run time. Checks such as -these help to ensure a program's correctness once it has been compiled -by eliminating type mismatches, and providing active checks for range -errors when your program is running. - -@value{GDBN} can check for conditions like the above if you wish. -Although @value{GDBN} does not check the statements in your program, it -can check expressions entered directly into @value{GDBN} for evaluation via -the @code{print} command, for example. As with the working language, -@value{GDBN} can also decide whether or not to check automatically based on -your program's source language. @xref{Support, ,Supported languages}, -for the default settings of supported languages. - -@menu -* Type Checking:: An overview of type checking -* Range Checking:: An overview of range checking -@end menu - -@cindex type checking -@cindex checks, type -@node Type Checking -@subsection An overview of type checking - -Some languages, such as Modula-2, are strongly typed, meaning that the -arguments to operators and functions have to be of the correct type, -otherwise an error occurs. These checks prevent type mismatch -errors from ever causing any run-time problems. For example, - -@smallexample -1 + 2 @result{} 3 -@exdent but -@error{} 1 + 2.3 -@end smallexample - -The second example fails because the @code{CARDINAL} 1 is not -type-compatible with the @code{REAL} 2.3. - -For the expressions you use in @value{GDBN} commands, you can tell the -@value{GDBN} type checker to skip checking; -to treat any mismatches as errors and abandon the expression; -or to only issue warnings when type mismatches occur, -but evaluate the expression anyway. When you choose the last of -these, @value{GDBN} evaluates expressions like the second example above, but -also issues a warning. - -Even if you turn type checking off, there may be other reasons -related to type that prevent @value{GDBN} from evaluating an expression. -For instance, @value{GDBN} does not know how to add an @code{int} and -a @code{struct foo}. These particular type errors have nothing to do -with the language in use, and usually arise from expressions, such as -the one described above, which make little sense to evaluate anyway. - -Each language defines to what degree it is strict about type. For -instance, both Modula-2 and C require the arguments to arithmetical -operators to be numbers. In C, enumerated types and pointers can be -represented as numbers, so that they are valid arguments to mathematical -operators. @xref{Support, ,Supported languages}, for further -details on specific languages. - -@value{GDBN} provides some additional commands for controlling the type checker: - -@kindex set check@r{, type} -@kindex set check type -@kindex show check type -@table @code -@item set check type auto -Set type checking on or off based on the current working language. -@xref{Support, ,Supported languages}, for the default settings for -each language. - -@item set check type on -@itemx set check type off -Set type checking on or off, overriding the default setting for the -current working language. Issue a warning if the setting does not -match the language default. If any type mismatches occur in -evaluating an expression while type checking is on, @value{GDBN} prints a -message and aborts evaluation of the expression. - -@item set check type warn -Cause the type checker to issue warnings, but to always attempt to -evaluate the expression. Evaluating the expression may still -be impossible for other reasons. For example, @value{GDBN} cannot add -numbers and structures. - -@item show type -Show the current setting of the type checker, and whether or not @value{GDBN} -is setting it automatically. -@end table - -@cindex range checking -@cindex checks, range -@node Range Checking -@subsection An overview of range checking - -In some languages (such as Modula-2), it is an error to exceed the -bounds of a type; this is enforced with run-time checks. Such range -checking is meant to ensure program correctness by making sure -computations do not overflow, or indices on an array element access do -not exceed the bounds of the array. - -For expressions you use in @value{GDBN} commands, you can tell -@value{GDBN} to treat range errors in one of three ways: ignore them, -always treat them as errors and abandon the expression, or issue -warnings but evaluate the expression anyway. - -A range error can result from numerical overflow, from exceeding an -array index bound, or when you type a constant that is not a member -of any type. Some languages, however, do not treat overflows as an -error. In many implementations of C, mathematical overflow causes the -result to ``wrap around'' to lower values---for example, if @var{m} is -the largest integer value, and @var{s} is the smallest, then - -@example -@var{m} + 1 @result{} @var{s} -@end example - -This, too, is specific to individual languages, and in some cases -specific to individual compilers or machines. @xref{Support, , -Supported languages}, for further details on specific languages. - -@value{GDBN} provides some additional commands for controlling the range checker: - -@kindex set check@r{, range} -@kindex set check range -@kindex show check range -@table @code -@item set check range auto -Set range checking on or off based on the current working language. -@xref{Support, ,Supported languages}, for the default settings for -each language. - -@item set check range on -@itemx set check range off -Set range checking on or off, overriding the default setting for the -current working language. A warning is issued if the setting does not -match the language default. If a range error occurs and range checking is on, -then a message is printed and evaluation of the expression is aborted. - -@item set check range warn -Output messages when the @value{GDBN} range checker detects a range error, -but attempt to evaluate the expression anyway. Evaluating the -expression may still be impossible for other reasons, such as accessing -memory that the process does not own (a typical example from many Unix -systems). - -@item show range -Show the current setting of the range checker, and whether or not it is -being set automatically by @value{GDBN}. -@end table - -@node Support -@section Supported languages - -@value{GDBN} supports C, C@t{++}, Fortran, Java, Chill, assembly, and Modula-2. -@c This is false ... -Some @value{GDBN} features may be used in expressions regardless of the -language you use: the @value{GDBN} @code{@@} and @code{::} operators, -and the @samp{@{type@}addr} construct (@pxref{Expressions, -,Expressions}) can be used with the constructs of any supported -language. - -The following sections detail to what degree each source language is -supported by @value{GDBN}. These sections are not meant to be language -tutorials or references, but serve only as a reference guide to what the -@value{GDBN} expression parser accepts, and what input and output -formats should look like for different languages. There are many good -books written on each of these languages; please look to these for a -language reference or tutorial. - -@menu -* C:: C and C@t{++} -* Modula-2:: Modula-2 -* Chill:: Chill -@end menu - -@node C -@subsection C and C@t{++} - -@cindex C and C@t{++} -@cindex expressions in C or C@t{++} - -Since C and C@t{++} are so closely related, many features of @value{GDBN} apply -to both languages. Whenever this is the case, we discuss those languages -together. - -@cindex C@t{++} -@cindex @code{g++}, @sc{gnu} C@t{++} compiler -@cindex @sc{gnu} C@t{++} -The C@t{++} debugging facilities are jointly implemented by the C@t{++} -compiler and @value{GDBN}. Therefore, to debug your C@t{++} code -effectively, you must compile your C@t{++} programs with a supported -C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++} -compiler (@code{aCC}). - -For best results when using @sc{gnu} C@t{++}, use the stabs debugging -format. You can select that format explicitly with the @code{g++} -command-line options @samp{-gstabs} or @samp{-gstabs+}. See -@ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu} -CC, gcc.info, Using @sc{gnu} CC}, for more information. - -@menu -* C Operators:: C and C@t{++} operators -* C Constants:: C and C@t{++} constants -* C plus plus expressions:: C@t{++} expressions -* C Defaults:: Default settings for C and C@t{++} -* C Checks:: C and C@t{++} type and range checks -* Debugging C:: @value{GDBN} and C -* Debugging C plus plus:: @value{GDBN} features for C@t{++} -@end menu - -@node C Operators -@subsubsection C and C@t{++} operators - -@cindex C and C@t{++} operators - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on structures. Operators are -often defined on groups of types. - -For the purposes of C and C@t{++}, the following definitions hold: - -@itemize @bullet - -@item -@emph{Integral types} include @code{int} with any of its storage-class -specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}. - -@item -@emph{Floating-point types} include @code{float}, @code{double}, and -@code{long double} (if supported by the target platform). - -@item -@emph{Pointer types} include all types defined as @code{(@var{type} *)}. - -@item -@emph{Scalar types} include all of the above. - -@end itemize - -@noindent -The following operators are supported. They are listed here -in order of increasing precedence: - -@table @code -@item , -The comma or sequencing operator. Expressions in a comma-separated list -are evaluated from left to right, with the result of the entire -expression being the last expression evaluated. - -@item = -Assignment. The value of an assignment expression is the value -assigned. Defined on scalar types. - -@item @var{op}= -Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}}, -and translated to @w{@code{@var{a} = @var{a op b}}}. -@w{@code{@var{op}=}} and @code{=} have the same precedence. -@var{op} is any one of the operators @code{|}, @code{^}, @code{&}, -@code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}. - -@item ?: -The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought -of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an -integral type. - -@item || -Logical @sc{or}. Defined on integral types. - -@item && -Logical @sc{and}. Defined on integral types. - -@item | -Bitwise @sc{or}. Defined on integral types. - -@item ^ -Bitwise exclusive-@sc{or}. Defined on integral types. - -@item & -Bitwise @sc{and}. Defined on integral types. - -@item ==@r{, }!= -Equality and inequality. Defined on scalar types. The value of these -expressions is 0 for false and non-zero for true. - -@item <@r{, }>@r{, }<=@r{, }>= -Less than, greater than, less than or equal, greater than or equal. -Defined on scalar types. The value of these expressions is 0 for false -and non-zero for true. - -@item <<@r{, }>> -left shift, and right shift. Defined on integral types. - -@item @@ -The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). - -@item +@r{, }- -Addition and subtraction. Defined on integral types, floating-point types and -pointer types. - -@item *@r{, }/@r{, }% -Multiplication, division, and modulus. Multiplication and division are -defined on integral and floating-point types. Modulus is defined on -integral types. - -@item ++@r{, }-- -Increment and decrement. When appearing before a variable, the -operation is performed before the variable is used in an expression; -when appearing after it, the variable's value is used before the -operation takes place. - -@item * -Pointer dereferencing. Defined on pointer types. Same precedence as -@code{++}. - -@item & -Address operator. Defined on variables. Same precedence as @code{++}. - -For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is -allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})} -(or, if you prefer, simply @samp{&&@var{ref}}) to examine the address -where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is -stored. - -@item - -Negative. Defined on integral and floating-point types. Same -precedence as @code{++}. - -@item ! -Logical negation. Defined on integral types. Same precedence as -@code{++}. - -@item ~ -Bitwise complement operator. Defined on integral types. Same precedence as -@code{++}. - - -@item .@r{, }-> -Structure member, and pointer-to-structure member. For convenience, -@value{GDBN} regards the two as equivalent, choosing whether to dereference a -pointer based on the stored type information. -Defined on @code{struct} and @code{union} data. - -@item .*@r{, }->* -Dereferences of pointers to members. - -@item [] -Array indexing. @code{@var{a}[@var{i}]} is defined as -@code{*(@var{a}+@var{i})}. Same precedence as @code{->}. - -@item () -Function parameter list. Same precedence as @code{->}. - -@item :: -C@t{++} scope resolution operator. Defined on @code{struct}, @code{union}, -and @code{class} types. - -@item :: -Doubled colons also represent the @value{GDBN} scope operator -(@pxref{Expressions, ,Expressions}). Same precedence as @code{::}, -above. -@end table - -If an operator is redefined in the user code, @value{GDBN} usually -attempts to invoke the redefined version instead of using the operator's -predefined meaning. - -@menu -* C Constants:: -@end menu - -@node C Constants -@subsubsection C and C@t{++} constants - -@cindex C and C@t{++} constants - -@value{GDBN} allows you to express the constants of C and C@t{++} in the -following ways: - -@itemize @bullet -@item -Integer constants are a sequence of digits. Octal constants are -specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants -by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter -@samp{l}, specifying that the constant should be treated as a -@code{long} value. - -@item -Floating point constants are a sequence of digits, followed by a decimal -point, followed by a sequence of digits, and optionally followed by an -exponent. An exponent is of the form: -@samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another -sequence of digits. The @samp{+} is optional for positive exponents. -A floating-point constant may also end with a letter @samp{f} or -@samp{F}, specifying that the constant should be treated as being of -the @code{float} (as opposed to the default @code{double}) type; or with -a letter @samp{l} or @samp{L}, which specifies a @code{long double} -constant. - -@item -Enumerated constants consist of enumerated identifiers, or their -integral equivalents. - -@item -Character constants are a single character surrounded by single quotes -(@code{'}), or a number---the ordinal value of the corresponding character -(usually its @sc{ascii} value). Within quotes, the single character may -be represented by a letter or by @dfn{escape sequences}, which are of -the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation -of the character's ordinal value; or of the form @samp{\@var{x}}, where -@samp{@var{x}} is a predefined special character---for example, -@samp{\n} for newline. - -@item -String constants are a sequence of character constants surrounded by -double quotes (@code{"}). Any valid character constant (as described -above) may appear. Double quotes within the string must be preceded by -a backslash, so for instance @samp{"a\"b'c"} is a string of five -characters. - -@item -Pointer constants are an integral value. You can also write pointers -to constants using the C operator @samp{&}. - -@item -Array constants are comma-separated lists surrounded by braces @samp{@{} -and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of -integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array, -and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers. -@end itemize - -@menu -* C plus plus expressions:: -* C Defaults:: -* C Checks:: - -* Debugging C:: -@end menu - -@node C plus plus expressions -@subsubsection C@t{++} expressions - -@cindex expressions in C@t{++} -@value{GDBN} expression handling can interpret most C@t{++} expressions. - -@cindex C@t{++} support, not in @sc{coff} -@cindex @sc{coff} versus C@t{++} -@cindex C@t{++} and object formats -@cindex object formats and C@t{++} -@cindex a.out and C@t{++} -@cindex @sc{ecoff} and C@t{++} -@cindex @sc{xcoff} and C@t{++} -@cindex @sc{elf}/stabs and C@t{++} -@cindex @sc{elf}/@sc{dwarf} and C@t{++} -@c FIXME!! GDB may eventually be able to debug C++ using DWARF; check -@c periodically whether this has happened... -@quotation -@emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the -proper compiler. Typically, C@t{++} debugging depends on the use of -additional debugging information in the symbol table, and thus requires -special support. In particular, if your compiler generates a.out, MIPS -@sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the -symbol table, these facilities are all available. (With @sc{gnu} CC, -you can use the @samp{-gstabs} option to request stabs debugging -extensions explicitly.) Where the object code format is standard -@sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C@t{++} -support in @value{GDBN} does @emph{not} work. -@end quotation - -@enumerate - -@cindex member functions -@item -Member function calls are allowed; you can use expressions like - -@example -count = aml->GetOriginal(x, y) -@end example - -@vindex this@r{, inside C@t{++} member functions} -@cindex namespace in C@t{++} -@item -While a member function is active (in the selected stack frame), your -expressions have the same namespace available as the member function; -that is, @value{GDBN} allows implicit references to the class instance -pointer @code{this} following the same rules as C@t{++}. - -@cindex call overloaded functions -@cindex overloaded functions, calling -@cindex type conversions in C@t{++} -@item -You can call overloaded functions; @value{GDBN} resolves the function -call to the right definition, with some restrictions. @value{GDBN} does not -perform overload resolution involving user-defined type conversions, -calls to constructors, or instantiations of templates that do not exist -in the program. It also cannot handle ellipsis argument lists or -default arguments. - -It does perform integral conversions and promotions, floating-point -promotions, arithmetic conversions, pointer conversions, conversions of -class objects to base classes, and standard conversions such as those of -functions or arrays to pointers; it requires an exact match on the -number of function arguments. - -Overload resolution is always performed, unless you have specified -@code{set overload-resolution off}. @xref{Debugging C plus plus, -,@value{GDBN} features for C@t{++}}. - -You must specify @code{set overload-resolution off} in order to use an -explicit function signature to call an overloaded function, as in -@smallexample -p 'foo(char,int)'('x', 13) -@end smallexample - -The @value{GDBN} command-completion facility can simplify this; -see @ref{Completion, ,Command completion}. - -@cindex reference declarations -@item -@value{GDBN} understands variables declared as C@t{++} references; you can use -them in expressions just as you do in C@t{++} source---they are automatically -dereferenced. - -In the parameter list shown when @value{GDBN} displays a frame, the values of -reference variables are not displayed (unlike other variables); this -avoids clutter, since references are often used for large structures. -The @emph{address} of a reference variable is always shown, unless -you have specified @samp{set print address off}. - -@item -@value{GDBN} supports the C@t{++} name resolution operator @code{::}---your -expressions can use it just as expressions in your program do. Since -one scope may be defined in another, you can use @code{::} repeatedly if -necessary, for example in an expression like -@samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows -resolving name scope by reference to source files, in both C and C@t{++} -debugging (@pxref{Variables, ,Program variables}). -@end enumerate - -In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports -calling virtual functions correctly, printing out virtual bases of -objects, calling functions in a base subobject, casting objects, and -invoking user-defined operators. - -@node C Defaults -@subsubsection C and C@t{++} defaults - -@cindex C and C@t{++} defaults - -If you allow @value{GDBN} to set type and range checking automatically, they -both default to @code{off} whenever the working language changes to -C or C@t{++}. This happens regardless of whether you or @value{GDBN} -selects the working language. - -If you allow @value{GDBN} to set the language automatically, it -recognizes source files whose names end with @file{.c}, @file{.C}, or -@file{.cc}, etc, and when @value{GDBN} enters code compiled from one of -these files, it sets the working language to C or C@t{++}. -@xref{Automatically, ,Having @value{GDBN} infer the source language}, -for further details. - -@c Type checking is (a) primarily motivated by Modula-2, and (b) -@c unimplemented. If (b) changes, it might make sense to let this node -@c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93. - -@node C Checks -@subsubsection C and C@t{++} type and range checks - -@cindex C and C@t{++} checks - -By default, when @value{GDBN} parses C or C@t{++} expressions, type checking -is not used. However, if you turn type checking on, @value{GDBN} -considers two variables type equivalent if: - -@itemize @bullet -@item -The two variables are structured and have the same structure, union, or -enumerated tag. - -@item -The two variables have the same type name, or types that have been -declared equivalent through @code{typedef}. - -@ignore -@c leaving this out because neither J Gilmore nor R Pesch understand it. -@c FIXME--beers? -@item -The two @code{struct}, @code{union}, or @code{enum} variables are -declared in the same declaration. (Note: this may not be true for all C -compilers.) -@end ignore -@end itemize - -Range checking, if turned on, is done on mathematical operations. Array -indices are not checked, since they are often used to index a pointer -that is not itself an array. - -@node Debugging C -@subsubsection @value{GDBN} and C - -The @code{set print union} and @code{show print union} commands apply to -the @code{union} type. When set to @samp{on}, any @code{union} that is -inside a @code{struct} or @code{class} is also printed. Otherwise, it -appears as @samp{@{...@}}. - -The @code{@@} operator aids in the debugging of dynamic arrays, formed -with pointers and a memory allocation function. @xref{Expressions, -,Expressions}. - -@menu -* Debugging C plus plus:: -@end menu - -@node Debugging C plus plus -@subsubsection @value{GDBN} features for C@t{++} - -@cindex commands for C@t{++} - -Some @value{GDBN} commands are particularly useful with C@t{++}, and some are -designed specifically for use with C@t{++}. Here is a summary: - -@table @code -@cindex break in overloaded functions -@item @r{breakpoint menus} -When you want a breakpoint in a function whose name is overloaded, -@value{GDBN} breakpoint menus help you specify which function definition -you want. @xref{Breakpoint Menus,,Breakpoint menus}. - -@cindex overloading in C@t{++} -@item rbreak @var{regex} -Setting breakpoints using regular expressions is helpful for setting -breakpoints on overloaded functions that are not members of any special -classes. -@xref{Set Breaks, ,Setting breakpoints}. - -@cindex C@t{++} exception handling -@item catch throw -@itemx catch catch -Debug C@t{++} exception handling using these commands. @xref{Set -Catchpoints, , Setting catchpoints}. - -@cindex inheritance -@item ptype @var{typename} -Print inheritance relationships as well as other information for type -@var{typename}. -@xref{Symbols, ,Examining the Symbol Table}. - -@cindex C@t{++} symbol display -@item set print demangle -@itemx show print demangle -@itemx set print asm-demangle -@itemx show print asm-demangle -Control whether C@t{++} symbols display in their source form, both when -displaying code as C@t{++} source and when displaying disassemblies. -@xref{Print Settings, ,Print settings}. - -@item set print object -@itemx show print object -Choose whether to print derived (actual) or declared types of objects. -@xref{Print Settings, ,Print settings}. - -@item set print vtbl -@itemx show print vtbl -Control the format for printing virtual function tables. -@xref{Print Settings, ,Print settings}. -(The @code{vtbl} commands do not work on programs compiled with the HP -ANSI C@t{++} compiler (@code{aCC}).) - -@kindex set overload-resolution -@cindex overloaded functions, overload resolution -@item set overload-resolution on -Enable overload resolution for C@t{++} expression evaluation. The default -is on. For overloaded functions, @value{GDBN} evaluates the arguments -and searches for a function whose signature matches the argument types, -using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++} -expressions}, for details). If it cannot find a match, it emits a -message. - -@item set overload-resolution off -Disable overload resolution for C@t{++} expression evaluation. For -overloaded functions that are not class member functions, @value{GDBN} -chooses the first function of the specified name that it finds in the -symbol table, whether or not its arguments are of the correct type. For -overloaded functions that are class member functions, @value{GDBN} -searches for a function whose signature @emph{exactly} matches the -argument types. - -@item @r{Overloaded symbol names} -You can specify a particular definition of an overloaded symbol, using -the same notation that is used to declare such symbols in C@t{++}: type -@code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can -also use the @value{GDBN} command-line word completion facilities to list the -available choices, or to finish the type list for you. -@xref{Completion,, Command completion}, for details on how to do this. -@end table - -@node Modula-2 -@subsection Modula-2 - -@cindex Modula-2, @value{GDBN} support - -The extensions made to @value{GDBN} to support Modula-2 only support -output from the @sc{gnu} Modula-2 compiler (which is currently being -developed). Other Modula-2 compilers are not currently supported, and -attempting to debug executables produced by them is most likely -to give an error as @value{GDBN} reads in the executable's symbol -table. - -@cindex expressions in Modula-2 -@menu -* M2 Operators:: Built-in operators -* Built-In Func/Proc:: Built-in functions and procedures -* M2 Constants:: Modula-2 constants -* M2 Defaults:: Default settings for Modula-2 -* Deviations:: Deviations from standard Modula-2 -* M2 Checks:: Modula-2 type and range checks -* M2 Scope:: The scope operators @code{::} and @code{.} -* GDB/M2:: @value{GDBN} and Modula-2 -@end menu - -@node M2 Operators -@subsubsection Operators -@cindex Modula-2 operators - -Operators must be defined on values of specific types. For instance, -@code{+} is defined on numbers, but not on structures. Operators are -often defined on groups of types. For the purposes of Modula-2, the -following definitions hold: - -@itemize @bullet - -@item -@emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and -their subranges. - -@item -@emph{Character types} consist of @code{CHAR} and its subranges. - -@item -@emph{Floating-point types} consist of @code{REAL}. - -@item -@emph{Pointer types} consist of anything declared as @code{POINTER TO -@var{type}}. - -@item -@emph{Scalar types} consist of all of the above. - -@item -@emph{Set types} consist of @code{SET} and @code{BITSET} types. - -@item -@emph{Boolean types} consist of @code{BOOLEAN}. -@end itemize - -@noindent -The following operators are supported, and appear in order of -increasing precedence: - -@table @code -@item , -Function argument or array index separator. - -@item := -Assignment. The value of @var{var} @code{:=} @var{value} is -@var{value}. - -@item <@r{, }> -Less than, greater than on integral, floating-point, or enumerated -types. - -@item <=@r{, }>= -Less than or equal to, greater than or equal to -on integral, floating-point and enumerated types, or set inclusion on -set types. Same precedence as @code{<}. - -@item =@r{, }<>@r{, }# -Equality and two ways of expressing inequality, valid on scalar types. -Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is -available for inequality, since @code{#} conflicts with the script -comment character. - -@item IN -Set membership. Defined on set types and the types of their members. -Same precedence as @code{<}. - -@item OR -Boolean disjunction. Defined on boolean types. - -@item AND@r{, }& -Boolean conjunction. Defined on boolean types. - -@item @@ -The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). - -@item +@r{, }- -Addition and subtraction on integral and floating-point types, or union -and difference on set types. - -@item * -Multiplication on integral and floating-point types, or set intersection -on set types. - -@item / -Division on floating-point types, or symmetric set difference on set -types. Same precedence as @code{*}. - -@item DIV@r{, }MOD -Integer division and remainder. Defined on integral types. Same -precedence as @code{*}. - -@item - -Negative. Defined on @code{INTEGER} and @code{REAL} data. - -@item ^ -Pointer dereferencing. Defined on pointer types. - -@item NOT -Boolean negation. Defined on boolean types. Same precedence as -@code{^}. - -@item . -@code{RECORD} field selector. Defined on @code{RECORD} data. Same -precedence as @code{^}. - -@item [] -Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}. - -@item () -Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence -as @code{^}. - -@item ::@r{, }. -@value{GDBN} and Modula-2 scope operators. -@end table - -@quotation -@emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN} -treats the use of the operator @code{IN}, or the use of operators -@code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#}, -@code{<=}, and @code{>=} on sets as an error. -@end quotation - - -@node Built-In Func/Proc -@subsubsection Built-in functions and procedures -@cindex Modula-2 built-ins - -Modula-2 also makes available several built-in procedures and functions. -In describing these, the following metavariables are used: - -@table @var - -@item a -represents an @code{ARRAY} variable. - -@item c -represents a @code{CHAR} constant or variable. - -@item i -represents a variable or constant of integral type. - -@item m -represents an identifier that belongs to a set. Generally used in the -same function with the metavariable @var{s}. The type of @var{s} should -be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}). - -@item n -represents a variable or constant of integral or floating-point type. - -@item r -represents a variable or constant of floating-point type. - -@item t -represents a type. - -@item v -represents a variable. - -@item x -represents a variable or constant of one of many types. See the -explanation of the function for details. -@end table - -All Modula-2 built-in procedures also return a result, described below. - -@table @code -@item ABS(@var{n}) -Returns the absolute value of @var{n}. - -@item CAP(@var{c}) -If @var{c} is a lower case letter, it returns its upper case -equivalent, otherwise it returns its argument. - -@item CHR(@var{i}) -Returns the character whose ordinal value is @var{i}. - -@item DEC(@var{v}) -Decrements the value in the variable @var{v} by one. Returns the new value. - -@item DEC(@var{v},@var{i}) -Decrements the value in the variable @var{v} by @var{i}. Returns the -new value. - -@item EXCL(@var{m},@var{s}) -Removes the element @var{m} from the set @var{s}. Returns the new -set. - -@item FLOAT(@var{i}) -Returns the floating point equivalent of the integer @var{i}. - -@item HIGH(@var{a}) -Returns the index of the last member of @var{a}. - -@item INC(@var{v}) -Increments the value in the variable @var{v} by one. Returns the new value. - -@item INC(@var{v},@var{i}) -Increments the value in the variable @var{v} by @var{i}. Returns the -new value. - -@item INCL(@var{m},@var{s}) -Adds the element @var{m} to the set @var{s} if it is not already -there. Returns the new set. - -@item MAX(@var{t}) -Returns the maximum value of the type @var{t}. - -@item MIN(@var{t}) -Returns the minimum value of the type @var{t}. - -@item ODD(@var{i}) -Returns boolean TRUE if @var{i} is an odd number. - -@item ORD(@var{x}) -Returns the ordinal value of its argument. For example, the ordinal -value of a character is its @sc{ascii} value (on machines supporting the -@sc{ascii} character set). @var{x} must be of an ordered type, which include -integral, character and enumerated types. - -@item SIZE(@var{x}) -Returns the size of its argument. @var{x} can be a variable or a type. - -@item TRUNC(@var{r}) -Returns the integral part of @var{r}. - -@item VAL(@var{t},@var{i}) -Returns the member of the type @var{t} whose ordinal value is @var{i}. -@end table - -@quotation -@emph{Warning:} Sets and their operations are not yet supported, so -@value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as -an error. -@end quotation - -@cindex Modula-2 constants -@node M2 Constants -@subsubsection Constants - -@value{GDBN} allows you to express the constants of Modula-2 in the following -ways: - -@itemize @bullet - -@item -Integer constants are simply a sequence of digits. When used in an -expression, a constant is interpreted to be type-compatible with the -rest of the expression. Hexadecimal integers are specified by a -trailing @samp{H}, and octal integers by a trailing @samp{B}. - -@item -Floating point constants appear as a sequence of digits, followed by a -decimal point and another sequence of digits. An optional exponent can -then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where -@samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the -digits of the floating point constant must be valid decimal (base 10) -digits. - -@item -Character constants consist of a single character enclosed by a pair of -like quotes, either single (@code{'}) or double (@code{"}). They may -also be expressed by their ordinal value (their @sc{ascii} value, usually) -followed by a @samp{C}. - -@item -String constants consist of a sequence of characters enclosed by a -pair of like quotes, either single (@code{'}) or double (@code{"}). -Escape sequences in the style of C are also allowed. @xref{C -Constants, ,C and C@t{++} constants}, for a brief explanation of escape -sequences. - -@item -Enumerated constants consist of an enumerated identifier. - -@item -Boolean constants consist of the identifiers @code{TRUE} and -@code{FALSE}. - -@item -Pointer constants consist of integral values only. - -@item -Set constants are not yet supported. -@end itemize - -@node M2 Defaults -@subsubsection Modula-2 defaults -@cindex Modula-2 defaults - -If type and range checking are set automatically by @value{GDBN}, they -both default to @code{on} whenever the working language changes to -Modula-2. This happens regardless of whether you or @value{GDBN} -selected the working language. - -If you allow @value{GDBN} to set the language automatically, then entering -code compiled from a file whose name ends with @file{.mod} sets the -working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set -the language automatically}, for further details. - -@node Deviations -@subsubsection Deviations from standard Modula-2 -@cindex Modula-2, deviations from - -A few changes have been made to make Modula-2 programs easier to debug. -This is done primarily via loosening its type strictness: - -@itemize @bullet -@item -Unlike in standard Modula-2, pointer constants can be formed by -integers. This allows you to modify pointer variables during -debugging. (In standard Modula-2, the actual address contained in a -pointer variable is hidden from you; it can only be modified -through direct assignment to another pointer variable or expression that -returned a pointer.) - -@item -C escape sequences can be used in strings and characters to represent -non-printable characters. @value{GDBN} prints out strings with these -escape sequences embedded. Single non-printable characters are -printed using the @samp{CHR(@var{nnn})} format. - -@item -The assignment operator (@code{:=}) returns the value of its right-hand -argument. - -@item -All built-in procedures both modify @emph{and} return their argument. -@end itemize - -@node M2 Checks -@subsubsection Modula-2 type and range checks -@cindex Modula-2 checks - -@quotation -@emph{Warning:} in this release, @value{GDBN} does not yet perform type or -range checking. -@end quotation -@c FIXME remove warning when type/range checks added - -@value{GDBN} considers two Modula-2 variables type equivalent if: - -@itemize @bullet -@item -They are of types that have been declared equivalent via a @code{TYPE -@var{t1} = @var{t2}} statement - -@item -They have been declared on the same line. (Note: This is true of the -@sc{gnu} Modula-2 compiler, but it may not be true of other compilers.) -@end itemize - -As long as type checking is enabled, any attempt to combine variables -whose types are not equivalent is an error. - -Range checking is done on all mathematical operations, assignment, array -index bounds, and all built-in functions and procedures. - -@node M2 Scope -@subsubsection The scope operators @code{::} and @code{.} -@cindex scope -@cindex @code{.}, Modula-2 scope operator -@cindex colon, doubled as scope operator -@ifinfo -@vindex colon-colon@r{, in Modula-2} -@c Info cannot handle :: but TeX can. -@end ifinfo -@iftex -@vindex ::@r{, in Modula-2} -@end iftex - -There are a few subtle differences between the Modula-2 scope operator -(@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have -similar syntax: - -@example - -@var{module} . @var{id} -@var{scope} :: @var{id} -@end example - -@noindent -where @var{scope} is the name of a module or a procedure, -@var{module} the name of a module, and @var{id} is any declared -identifier within your program, except another module. - -Using the @code{::} operator makes @value{GDBN} search the scope -specified by @var{scope} for the identifier @var{id}. If it is not -found in the specified scope, then @value{GDBN} searches all scopes -enclosing the one specified by @var{scope}. - -Using the @code{.} operator makes @value{GDBN} search the current scope for -the identifier specified by @var{id} that was imported from the -definition module specified by @var{module}. With this operator, it is -an error if the identifier @var{id} was not imported from definition -module @var{module}, or if @var{id} is not an identifier in -@var{module}. - -@node GDB/M2 -@subsubsection @value{GDBN} and Modula-2 - -Some @value{GDBN} commands have little use when debugging Modula-2 programs. -Five subcommands of @code{set print} and @code{show print} apply -specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle}, -@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four -apply to C@t{++}, and the last to the C @code{union} type, which has no direct -analogue in Modula-2. - -The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available -with any language, is not useful with Modula-2. Its -intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be -created in Modula-2 as they can in C or C@t{++}. However, because an -address can be specified by an integral constant, the construct -@samp{@{@var{type}@}@var{adrexp}} is still useful. - -@cindex @code{#} in Modula-2 -In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is -interpreted as the beginning of a comment. Use @code{<>} instead. - -@node Chill -@subsection Chill - -The extensions made to @value{GDBN} to support Chill only support output -from the @sc{gnu} Chill compiler. Other Chill compilers are not currently -supported, and attempting to debug executables produced by them is most -likely to give an error as @value{GDBN} reads in the executable's symbol -table. - -@c This used to say "... following Chill related topics ...", but since -@c menus are not shown in the printed manual, it would look awkward. -This section covers the Chill related topics and the features -of @value{GDBN} which support these topics. - -@menu -* How modes are displayed:: How modes are displayed -* Locations:: Locations and their accesses -* Values and their Operations:: Values and their Operations -* Chill type and range checks:: -* Chill defaults:: -@end menu - -@node How modes are displayed -@subsubsection How modes are displayed - -The Chill Datatype- (Mode) support of @value{GDBN} is directly related -with the functionality of the @sc{gnu} Chill compiler, and therefore deviates -slightly from the standard specification of the Chill language. The -provided modes are: - -@c FIXME: this @table's contents effectively disable @code by using @r -@c on every @item. So why does it need @code? -@table @code -@item @r{@emph{Discrete modes:}} -@itemize @bullet -@item -@emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT, -UINT, LONG, ULONG}, -@item -@emph{Boolean Mode} which is predefined by @code{BOOL}, -@item -@emph{Character Mode} which is predefined by @code{CHAR}, -@item -@emph{Set Mode} which is displayed by the keyword @code{SET}. -@smallexample -(@value{GDBP}) ptype x -type = SET (karli = 10, susi = 20, fritzi = 100) -@end smallexample -If the type is an unnumbered set the set element values are omitted. -@item -@emph{Range Mode} which is displayed by -@smallexample -@code{type = <basemode>(<lower bound> : <upper bound>)} -@end smallexample -where @code{<lower bound>, <upper bound>} can be of any discrete literal -expression (e.g. set element names). -@end itemize - -@item @r{@emph{Powerset Mode:}} -A Powerset Mode is displayed by the keyword @code{POWERSET} followed by -the member mode of the powerset. The member mode can be any discrete mode. -@smallexample -(@value{GDBP}) ptype x -type = POWERSET SET (egon, hugo, otto) -@end smallexample - -@item @r{@emph{Reference Modes:}} -@itemize @bullet -@item -@emph{Bound Reference Mode} which is displayed by the keyword @code{REF} -followed by the mode name to which the reference is bound. -@item -@emph{Free Reference Mode} which is displayed by the keyword @code{PTR}. -@end itemize - -@item @r{@emph{Procedure mode}} -The procedure mode is displayed by @code{type = PROC(<parameter list>) -<return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter -list>} is a list of the parameter modes. @code{<return mode>} indicates -the mode of the result of the procedure if any. The exceptionlist lists -all possible exceptions which can be raised by the procedure. - -@ignore -@item @r{@emph{Instance mode}} -The instance mode is represented by a structure, which has a static -type, and is therefore not really of interest. -@end ignore - -@item @r{@emph{Synchronization Modes:}} -@itemize @bullet -@item -@emph{Event Mode} which is displayed by -@smallexample -@code{EVENT (<event length>)} -@end smallexample -where @code{(<event length>)} is optional. -@item -@emph{Buffer Mode} which is displayed by -@smallexample -@code{BUFFER (<buffer length>)<buffer element mode>} -@end smallexample -where @code{(<buffer length>)} is optional. -@end itemize - -@item @r{@emph{Timing Modes:}} -@itemize @bullet -@item -@emph{Duration Mode} which is predefined by @code{DURATION} -@item -@emph{Absolute Time Mode} which is predefined by @code{TIME} -@end itemize - -@item @r{@emph{Real Modes:}} -Real Modes are predefined with @code{REAL} and @code{LONG_REAL}. - -@item @r{@emph{String Modes:}} -@itemize @bullet -@item -@emph{Character String Mode} which is displayed by -@smallexample -@code{CHARS(<string length>)} -@end smallexample -followed by the keyword @code{VARYING} if the String Mode is a varying -mode -@item -@emph{Bit String Mode} which is displayed by -@smallexample -@code{BOOLS(<string -length>)} -@end smallexample -@end itemize - -@item @r{@emph{Array Mode:}} -The Array Mode is displayed by the keyword @code{ARRAY(<range>)} -followed by the element mode (which may in turn be an array mode). -@smallexample -(@value{GDBP}) ptype x -type = ARRAY (1:42) - ARRAY (1:20) - SET (karli = 10, susi = 20, fritzi = 100) -@end smallexample - -@item @r{@emph{Structure Mode}} -The Structure mode is displayed by the keyword @code{STRUCT(<field -list>)}. The @code{<field list>} consists of names and modes of fields -of the structure. Variant structures have the keyword @code{CASE <field> -OF <variant fields> ESAC} in their field list. Since the current version -of the GNU Chill compiler doesn't implement tag processing (no runtime -checks of variant fields, and therefore no debugging info), the output -always displays all variant fields. -@smallexample -(@value{GDBP}) ptype str -type = STRUCT ( - as x, - bs x, - CASE bs OF - (karli): - cs a - (ott): - ds x - ESAC -) -@end smallexample -@end table - -@node Locations -@subsubsection Locations and their accesses - -A location in Chill is an object which can contain values. - -A value of a location is generally accessed by the (declared) name of -the location. The output conforms to the specification of values in -Chill programs. How values are specified -is the topic of the next section, @ref{Values and their Operations}. - -The pseudo-location @code{RESULT} (or @code{result}) can be used to -display or change the result of a currently-active procedure: - -@smallexample -set result := EXPR -@end smallexample - -@noindent -This does the same as the Chill action @code{RESULT EXPR} (which -is not available in @value{GDBN}). - -Values of reference mode locations are printed by @code{PTR(<hex -value>)} in case of a free reference mode, and by @code{(REF <reference -mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>} -represents the address where the reference points to. To access the -value of the location referenced by the pointer, use the dereference -operator @samp{->}. - -Values of procedure mode locations are displayed by -@smallexample -@code{@{ PROC -(<argument modes> ) <return mode> @} <address> <name of procedure -location>} -@end smallexample -@code{<argument modes>} is a list of modes according to the parameter -specification of the procedure and @code{<address>} shows the address of -the entry point. - -@ignore -Locations of instance modes are displayed just like a structure with two -fields specifying the @emph{process type} and the @emph{copy number} of -the investigated instance location@footnote{This comes from the current -implementation of instances. They are implemented as a structure (no -na). The output should be something like @code{[<name of the process>; -<instance number>]}.}. The field names are @code{__proc_type} and -@code{__proc_copy}. - -Locations of synchronization modes are displayed like a structure with -the field name @code{__event_data} in case of a event mode location, and -like a structure with the field @code{__buffer_data} in case of a buffer -mode location (refer to previous paragraph). - -Structure Mode locations are printed by @code{[.<field name>: <value>, -...]}. The @code{<field name>} corresponds to the structure mode -definition and the layout of @code{<value>} varies depending of the mode -of the field. If the investigated structure mode location is of variant -structure mode, the variant parts of the structure are enclosed in curled -braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing -on the same memory location and represent the current values of the -memory location in their specific modes. Since no tag processing is done -all variants are displayed. A variant field is printed by -@code{(<variant name>) = .<field name>: <value>}. (who implements the -stuff ???) -@smallexample -(@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) = -[.cs: []], (susi) = [.ds: susi]}] -@end smallexample -@end ignore - -Substructures of string mode-, array mode- or structure mode-values -(e.g. array slices, fields of structure locations) are accessed using -certain operations which are described in the next section, @ref{Values -and their Operations}. - -A location value may be interpreted as having a different mode using the -location conversion. This mode conversion is written as @code{<mode -name>(<location>)}. The user has to consider that the sizes of the modes -have to be equal otherwise an error occurs. Furthermore, no range -checking of the location against the destination mode is performed, and -therefore the result can be quite confusing. - -@smallexample -(@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX -@end smallexample - -@node Values and their Operations -@subsubsection Values and their Operations - -Values are used to alter locations, to investigate complex structures in -more detail or to filter relevant information out of a large amount of -data. There are several (mode dependent) operations defined which enable -such investigations. These operations are not only applicable to -constant values but also to locations, which can become quite useful -when debugging complex structures. During parsing the command line -(e.g. evaluating an expression) @value{GDBN} treats location names as -the values behind these locations. - -This section describes how values have to be specified and which -operations are legal to be used with such values. - -@table @code -@item Literal Values -Literal values are specified in the same manner as in @sc{gnu} Chill programs. -For detailed specification refer to the @sc{gnu} Chill implementation Manual -chapter 1.5. -@c FIXME: if the Chill Manual is a Texinfo documents, the above should -@c be converted to a @ref. - -@ignore -@itemize @bullet -@item -@emph{Integer Literals} are specified in the same manner as in Chill -programs (refer to the Chill Standard z200/88 chpt 5.2.4.2) -@item -@emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}. -@item -@emph{Character Literals} are defined by @code{'<character>'}. (e.g. -@code{'M'}) -@item -@emph{Set Literals} are defined by a name which was specified in a set -mode. The value delivered by a Set Literal is the set value. This is -comparable to an enumeration in C/C@t{++} language. -@item -@emph{Emptiness Literal} is predefined by @code{NULL}. The value of the -emptiness literal delivers either the empty reference value, the empty -procedure value or the empty instance value. - -@item -@emph{Character String Literals} are defined by a sequence of characters -enclosed in single- or double quotes. If a single- or double quote has -to be part of the string literal it has to be stuffed (specified twice). -@item -@emph{Bitstring Literals} are specified in the same manner as in Chill -programs (refer z200/88 chpt 5.2.4.8). -@item -@emph{Floating point literals} are specified in the same manner as in -(gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5). -@end itemize -@end ignore - -@item Tuple Values -A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode -name>} can be omitted if the mode of the tuple is unambiguous. This -unambiguity is derived from the context of a evaluated expression. -@code{<tuple>} can be one of the following: - -@itemize @bullet -@item @emph{Powerset Tuple} -@item @emph{Array Tuple} -@item @emph{Structure Tuple} -Powerset tuples, array tuples and structure tuples are specified in the -same manner as in Chill programs refer to z200/88 chpt 5.2.5. -@end itemize - -@item String Element Value -A string element value is specified by -@smallexample -@code{<string value>(<index>)} -@end smallexample -where @code{<index>} is a integer expression. It delivers a character -value which is equivalent to the character indexed by @code{<index>} in -the string. - -@item String Slice Value -A string slice value is specified by @code{<string value>(<slice -spec>)}, where @code{<slice spec>} can be either a range of integer -expressions or specified by @code{<start expr> up <size>}. -@code{<size>} denotes the number of elements which the slice contains. -The delivered value is a string value, which is part of the specified -string. - -@item Array Element Values -An array element value is specified by @code{<array value>(<expr>)} and -delivers a array element value of the mode of the specified array. - -@item Array Slice Values -An array slice is specified by @code{<array value>(<slice spec>)}, where -@code{<slice spec>} can be either a range specified by expressions or by -@code{<start expr> up <size>}. @code{<size>} denotes the number of -arrayelements the slice contains. The delivered value is an array value -which is part of the specified array. - -@item Structure Field Values -A structure field value is derived by @code{<structure value>.<field -name>}, where @code{<field name>} indicates the name of a field specified -in the mode definition of the structure. The mode of the delivered value -corresponds to this mode definition in the structure definition. - -@item Procedure Call Value -The procedure call value is derived from the return value of the -procedure@footnote{If a procedure call is used for instance in an -expression, then this procedure is called with all its side -effects. This can lead to confusing results if used carelessly.}. - -Values of duration mode locations are represented by @code{ULONG} literals. - -Values of time mode locations appear as -@smallexample -@code{TIME(<secs>:<nsecs>)} -@end smallexample - - -@ignore -This is not implemented yet: -@item Built-in Value -@noindent -The following built in functions are provided: - -@table @code -@item @code{ADDR()} -@item @code{NUM()} -@item @code{PRED()} -@item @code{SUCC()} -@item @code{ABS()} -@item @code{CARD()} -@item @code{MAX()} -@item @code{MIN()} -@item @code{SIZE()} -@item @code{UPPER()} -@item @code{LOWER()} -@item @code{LENGTH()} -@item @code{SIN()} -@item @code{COS()} -@item @code{TAN()} -@item @code{ARCSIN()} -@item @code{ARCCOS()} -@item @code{ARCTAN()} -@item @code{EXP()} -@item @code{LN()} -@item @code{LOG()} -@item @code{SQRT()} -@end table - -For a detailed description refer to the GNU Chill implementation manual -chapter 1.6. -@end ignore - -@item Zero-adic Operator Value -The zero-adic operator value is derived from the instance value for the -current active process. - -@item Expression Values -The value delivered by an expression is the result of the evaluation of -the specified expression. If there are error conditions (mode -incompatibility, etc.) the evaluation of expressions is aborted with a -corresponding error message. Expressions may be parenthesised which -causes the evaluation of this expression before any other expression -which uses the result of the parenthesised expression. The following -operators are supported by @value{GDBN}: - -@table @code -@item @code{OR, ORIF, XOR} -@itemx @code{AND, ANDIF} -@itemx @code{NOT} -Logical operators defined over operands of boolean mode. - -@item @code{=, /=} -Equality and inequality operators defined over all modes. - -@item @code{>, >=} -@itemx @code{<, <=} -Relational operators defined over predefined modes. - -@item @code{+, -} -@itemx @code{*, /, MOD, REM} -Arithmetic operators defined over predefined modes. - -@item @code{-} -Change sign operator. - -@item @code{//} -String concatenation operator. - -@item @code{()} -String repetition operator. - -@item @code{->} -Referenced location operator which can be used either to take the -address of a location (@code{->loc}), or to dereference a reference -location (@code{loc->}). - -@item @code{OR, XOR} -@itemx @code{AND} -@itemx @code{NOT} -Powerset and bitstring operators. - -@item @code{>, >=} -@itemx @code{<, <=} -Powerset inclusion operators. - -@item @code{IN} -Membership operator. -@end table -@end table - -@node Chill type and range checks -@subsubsection Chill type and range checks - -@value{GDBN} considers two Chill variables mode equivalent if the sizes -of the two modes are equal. This rule applies recursively to more -complex datatypes which means that complex modes are treated -equivalent if all element modes (which also can be complex modes like -structures, arrays, etc.) have the same size. - -Range checking is done on all mathematical operations, assignment, array -index bounds and all built in procedures. - -Strong type checks are forced using the @value{GDBN} command @code{set -check strong}. This enforces strong type and range checks on all -operations where Chill constructs are used (expressions, built in -functions, etc.) in respect to the semantics as defined in the z.200 -language specification. - -All checks can be disabled by the @value{GDBN} command @code{set check -off}. - -@ignore -@c Deviations from the Chill Standard Z200/88 -see last paragraph ? -@end ignore - -@node Chill defaults -@subsubsection Chill defaults - -If type and range checking are set automatically by @value{GDBN}, they -both default to @code{on} whenever the working language changes to -Chill. This happens regardless of whether you or @value{GDBN} -selected the working language. - -If you allow @value{GDBN} to set the language automatically, then entering -code compiled from a file whose name ends with @file{.ch} sets the -working language to Chill. @xref{Automatically, ,Having @value{GDBN} set -the language automatically}, for further details. - -@node Symbols -@chapter Examining the Symbol Table - -The commands described in this chapter allow you to inquire about the -symbols (names of variables, functions and types) defined in your -program. This information is inherent in the text of your program and -does not change as your program executes. @value{GDBN} finds it in your -program's symbol table, in the file indicated when you started @value{GDBN} -(@pxref{File Options, ,Choosing files}), or by one of the -file-management commands (@pxref{Files, ,Commands to specify files}). - -@cindex symbol names -@cindex names of symbols -@cindex quoting names -Occasionally, you may need to refer to symbols that contain unusual -characters, which @value{GDBN} ordinarily treats as word delimiters. The -most frequent case is in referring to static variables in other -source files (@pxref{Variables,,Program variables}). File names -are recorded in object files as debugging symbols, but @value{GDBN} would -ordinarily parse a typical file name, like @file{foo.c}, as the three words -@samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize -@samp{foo.c} as a single symbol, enclose it in single quotes; for example, - -@example -p 'foo.c'::x -@end example - -@noindent -looks up the value of @code{x} in the scope of the file @file{foo.c}. - -@table @code -@kindex info address -@cindex address of a symbol -@item info address @var{symbol} -Describe where the data for @var{symbol} is stored. For a register -variable, this says which register it is kept in. For a non-register -local variable, this prints the stack-frame offset at which the variable -is always stored. - -Note the contrast with @samp{print &@var{symbol}}, which does not work -at all for a register variable, and for a stack local variable prints -the exact address of the current instantiation of the variable. - -@kindex info symbol -@cindex symbol from address -@item info symbol @var{addr} -Print the name of a symbol which is stored at the address @var{addr}. -If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the -nearest symbol and an offset from it: - -@example -(@value{GDBP}) info symbol 0x54320 -_initialize_vx + 396 in section .text -@end example - -@noindent -This is the opposite of the @code{info address} command. You can use -it to find out the name of a variable or a function given its address. - -@kindex whatis -@item whatis @var{expr} -Print the data type of expression @var{expr}. @var{expr} is not -actually evaluated, and any side-effecting operations (such as -assignments or function calls) inside it do not take place. -@xref{Expressions, ,Expressions}. - -@item whatis -Print the data type of @code{$}, the last value in the value history. - -@kindex ptype -@item ptype @var{typename} -Print a description of data type @var{typename}. @var{typename} may be -the name of a type, or for C code it may have the form @samp{class -@var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union -@var{union-tag}} or @samp{enum @var{enum-tag}}. - -@item ptype @var{expr} -@itemx ptype -Print a description of the type of expression @var{expr}. @code{ptype} -differs from @code{whatis} by printing a detailed description, instead -of just the name of the type. - -For example, for this variable declaration: - -@example -struct complex @{double real; double imag;@} v; -@end example - -@noindent -the two commands give this output: - -@example -@group -(@value{GDBP}) whatis v -type = struct complex -(@value{GDBP}) ptype v -type = struct complex @{ - double real; - double imag; -@} -@end group -@end example - -@noindent -As with @code{whatis}, using @code{ptype} without an argument refers to -the type of @code{$}, the last value in the value history. - -@kindex info types -@item info types @var{regexp} -@itemx info types -Print a brief description of all types whose names match @var{regexp} -(or all types in your program, if you supply no argument). Each -complete typename is matched as though it were a complete line; thus, -@samp{i type value} gives information on all types in your program whose -names include the string @code{value}, but @samp{i type ^value$} gives -information only on types whose complete name is @code{value}. - -This command differs from @code{ptype} in two ways: first, like -@code{whatis}, it does not print a detailed description; second, it -lists all source files where a type is defined. - -@kindex info scope -@cindex local variables -@item info scope @var{addr} -List all the variables local to a particular scope. This command -accepts a location---a function name, a source line, or an address -preceded by a @samp{*}, and prints all the variables local to the -scope defined by that location. For example: - -@smallexample -(@value{GDBP}) @b{info scope command_line_handler} -Scope for command_line_handler: -Symbol rl is an argument at stack/frame offset 8, length 4. -Symbol linebuffer is in static storage at address 0x150a18, length 4. -Symbol linelength is in static storage at address 0x150a1c, length 4. -Symbol p is a local variable in register $esi, length 4. -Symbol p1 is a local variable in register $ebx, length 4. -Symbol nline is a local variable in register $edx, length 4. -Symbol repeat is a local variable at frame offset -8, length 4. -@end smallexample - -@noindent -This command is especially useful for determining what data to collect -during a @dfn{trace experiment}, see @ref{Tracepoint Actions, -collect}. - -@kindex info source -@item info source -Show the name of the current source file---that is, the source file for -the function containing the current point of execution---and the language -it was written in. - -@kindex info sources -@item info sources -Print the names of all source files in your program for which there is -debugging information, organized into two lists: files whose symbols -have already been read, and files whose symbols will be read when needed. - -@kindex info functions -@item info functions -Print the names and data types of all defined functions. - -@item info functions @var{regexp} -Print the names and data types of all defined functions -whose names contain a match for regular expression @var{regexp}. -Thus, @samp{info fun step} finds all functions whose names -include @code{step}; @samp{info fun ^step} finds those whose names -start with @code{step}. If a function name contains characters -that conflict with the regular expression language (eg. -@samp{operator*()}), they may be quoted with a backslash. - -@kindex info variables -@item info variables -Print the names and data types of all variables that are declared -outside of functions (i.e.@: excluding local variables). - -@item info variables @var{regexp} -Print the names and data types of all variables (except for local -variables) whose names contain a match for regular expression -@var{regexp}. - -@ignore -This was never implemented. -@kindex info methods -@item info methods -@itemx info methods @var{regexp} -The @code{info methods} command permits the user to examine all defined -methods within C@t{++} program, or (with the @var{regexp} argument) a -specific set of methods found in the various C@t{++} classes. Many -C@t{++} classes provide a large number of methods. Thus, the output -from the @code{ptype} command can be overwhelming and hard to use. The -@code{info-methods} command filters the methods, printing only those -which match the regular-expression @var{regexp}. -@end ignore - -@cindex reloading symbols -Some systems allow individual object files that make up your program to -be replaced without stopping and restarting your program. For example, -in VxWorks you can simply recompile a defective object file and keep on -running. If you are running on one of these systems, you can allow -@value{GDBN} to reload the symbols for automatically relinked modules: - -@table @code -@kindex set symbol-reloading -@item set symbol-reloading on -Replace symbol definitions for the corresponding source file when an -object file with a particular name is seen again. - -@item set symbol-reloading off -Do not replace symbol definitions when encountering object files of the -same name more than once. This is the default state; if you are not -running on a system that permits automatic relinking of modules, you -should leave @code{symbol-reloading} off, since otherwise @value{GDBN} -may discard symbols when linking large programs, that may contain -several modules (from different directories or libraries) with the same -name. - -@kindex show symbol-reloading -@item show symbol-reloading -Show the current @code{on} or @code{off} setting. -@end table - -@kindex set opaque-type-resolution -@item set opaque-type-resolution on -Tell @value{GDBN} to resolve opaque types. An opaque type is a type -declared as a pointer to a @code{struct}, @code{class}, or -@code{union}---for example, @code{struct MyType *}---that is used in one -source file although the full declaration of @code{struct MyType} is in -another source file. The default is on. - -A change in the setting of this subcommand will not take effect until -the next time symbols for a file are loaded. - -@item set opaque-type-resolution off -Tell @value{GDBN} not to resolve opaque types. In this case, the type -is printed as follows: -@smallexample -@{<no data fields>@} -@end smallexample - -@kindex show opaque-type-resolution -@item show opaque-type-resolution -Show whether opaque types are resolved or not. - -@kindex maint print symbols -@cindex symbol dump -@kindex maint print psymbols -@cindex partial symbol dump -@item maint print symbols @var{filename} -@itemx maint print psymbols @var{filename} -@itemx maint print msymbols @var{filename} -Write a dump of debugging symbol data into the file @var{filename}. -These commands are used to debug the @value{GDBN} symbol-reading code. Only -symbols with debugging data are included. If you use @samp{maint print -symbols}, @value{GDBN} includes all the symbols for which it has already -collected full details: that is, @var{filename} reflects symbols for -only those files whose symbols @value{GDBN} has read. You can use the -command @code{info sources} to find out which files these are. If you -use @samp{maint print psymbols} instead, the dump shows information about -symbols that @value{GDBN} only knows partially---that is, symbols defined in -files that @value{GDBN} has skimmed, but not yet read completely. Finally, -@samp{maint print msymbols} dumps just the minimal symbol information -required for each object file from which @value{GDBN} has read some symbols. -@xref{Files, ,Commands to specify files}, for a discussion of how -@value{GDBN} reads symbols (in the description of @code{symbol-file}). -@end table - -@node Altering -@chapter Altering Execution - -Once you think you have found an error in your program, you might want to -find out for certain whether correcting the apparent error would lead to -correct results in the rest of the run. You can find the answer by -experiment, using the @value{GDBN} features for altering execution of the -program. - -For example, you can store new values into variables or memory -locations, give your program a signal, restart it at a different -address, or even return prematurely from a function. - -@menu -* Assignment:: Assignment to variables -* Jumping:: Continuing at a different address -* Signaling:: Giving your program a signal -* Returning:: Returning from a function -* Calling:: Calling your program's functions -* Patching:: Patching your program -@end menu - -@node Assignment -@section Assignment to variables - -@cindex assignment -@cindex setting variables -To alter the value of a variable, evaluate an assignment expression. -@xref{Expressions, ,Expressions}. For example, - -@example -print x=4 -@end example - -@noindent -stores the value 4 into the variable @code{x}, and then prints the -value of the assignment expression (which is 4). -@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more -information on operators in supported languages. - -@kindex set variable -@cindex variables, setting -If you are not interested in seeing the value of the assignment, use the -@code{set} command instead of the @code{print} command. @code{set} is -really the same as @code{print} except that the expression's value is -not printed and is not put in the value history (@pxref{Value History, -,Value history}). The expression is evaluated only for its effects. - -If the beginning of the argument string of the @code{set} command -appears identical to a @code{set} subcommand, use the @code{set -variable} command instead of just @code{set}. This command is identical -to @code{set} except for its lack of subcommands. For example, if your -program has a variable @code{width}, you get an error if you try to set -a new value with just @samp{set width=13}, because @value{GDBN} has the -command @code{set width}: - -@example -(@value{GDBP}) whatis width -type = double -(@value{GDBP}) p width -$4 = 13 -(@value{GDBP}) set width=47 -Invalid syntax in expression. -@end example - -@noindent -The invalid expression, of course, is @samp{=47}. In -order to actually set the program's variable @code{width}, use - -@example -(@value{GDBP}) set var width=47 -@end example - -Because the @code{set} command has many subcommands that can conflict -with the names of program variables, it is a good idea to use the -@code{set variable} command instead of just @code{set}. For example, if -your program has a variable @code{g}, you run into problems if you try -to set a new value with just @samp{set g=4}, because @value{GDBN} has -the command @code{set gnutarget}, abbreviated @code{set g}: - -@example -@group -(@value{GDBP}) whatis g -type = double -(@value{GDBP}) p g -$1 = 1 -(@value{GDBP}) set g=4 -(@value{GDBP}) p g -$2 = 1 -(@value{GDBP}) r -The program being debugged has been started already. -Start it from the beginning? (y or n) y -Starting program: /home/smith/cc_progs/a.out -"/home/smith/cc_progs/a.out": can't open to read symbols: - Invalid bfd target. -(@value{GDBP}) show g -The current BFD target is "=4". -@end group -@end example - -@noindent -The program variable @code{g} did not change, and you silently set the -@code{gnutarget} to an invalid value. In order to set the variable -@code{g}, use - -@example -(@value{GDBP}) set var g=4 -@end example - -@value{GDBN} allows more implicit conversions in assignments than C; you can -freely store an integer value into a pointer variable or vice versa, -and you can convert any structure to any other structure that is the -same length or shorter. -@comment FIXME: how do structs align/pad in these conversions? -@comment /doc@cygnus.com 18dec1990 - -To store values into arbitrary places in memory, use the @samp{@{@dots{}@}} -construct to generate a value of specified type at a specified address -(@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers -to memory location @code{0x83040} as an integer (which implies a certain size -and representation in memory), and - -@example -set @{int@}0x83040 = 4 -@end example - -@noindent -stores the value 4 into that memory location. - -@node Jumping -@section Continuing at a different address - -Ordinarily, when you continue your program, you do so at the place where -it stopped, with the @code{continue} command. You can instead continue at -an address of your own choosing, with the following commands: - -@table @code -@kindex jump -@item jump @var{linespec} -Resume execution at line @var{linespec}. Execution stops again -immediately if there is a breakpoint there. @xref{List, ,Printing -source lines}, for a description of the different forms of -@var{linespec}. It is common practice to use the @code{tbreak} command -in conjunction with @code{jump}. @xref{Set Breaks, ,Setting -breakpoints}. - -The @code{jump} command does not change the current stack frame, or -the stack pointer, or the contents of any memory location or any -register other than the program counter. If line @var{linespec} is in -a different function from the one currently executing, the results may -be bizarre if the two functions expect different patterns of arguments or -of local variables. For this reason, the @code{jump} command requests -confirmation if the specified line is not in the function currently -executing. However, even bizarre results are predictable if you are -well acquainted with the machine-language code of your program. - -@item jump *@var{address} -Resume execution at the instruction at address @var{address}. -@end table - -@c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt. -On many systems, you can get much the same effect as the @code{jump} -command by storing a new value into the register @code{$pc}. The -difference is that this does not start your program running; it only -changes the address of where it @emph{will} run when you continue. For -example, - -@example -set $pc = 0x485 -@end example - -@noindent -makes the next @code{continue} command or stepping command execute at -address @code{0x485}, rather than at the address where your program stopped. -@xref{Continuing and Stepping, ,Continuing and stepping}. - -The most common occasion to use the @code{jump} command is to back -up---perhaps with more breakpoints set---over a portion of a program -that has already executed, in order to examine its execution in more -detail. - -@c @group -@node Signaling -@section Giving your program a signal - -@table @code -@kindex signal -@item signal @var{signal} -Resume execution where your program stopped, but immediately give it the -signal @var{signal}. @var{signal} can be the name or the number of a -signal. For example, on many systems @code{signal 2} and @code{signal -SIGINT} are both ways of sending an interrupt signal. - -Alternatively, if @var{signal} is zero, continue execution without -giving a signal. This is useful when your program stopped on account of -a signal and would ordinary see the signal when resumed with the -@code{continue} command; @samp{signal 0} causes it to resume without a -signal. - -@code{signal} does not repeat when you press @key{RET} a second time -after executing the command. -@end table -@c @end group - -Invoking the @code{signal} command is not the same as invoking the -@code{kill} utility from the shell. Sending a signal with @code{kill} -causes @value{GDBN} to decide what to do with the signal depending on -the signal handling tables (@pxref{Signals}). The @code{signal} command -passes the signal directly to your program. - - -@node Returning -@section Returning from a function - -@table @code -@cindex returning from a function -@kindex return -@item return -@itemx return @var{expression} -You can cancel execution of a function call with the @code{return} -command. If you give an -@var{expression} argument, its value is used as the function's return -value. -@end table - -When you use @code{return}, @value{GDBN} discards the selected stack frame -(and all frames within it). You can think of this as making the -discarded frame return prematurely. If you wish to specify a value to -be returned, give that value as the argument to @code{return}. - -This pops the selected stack frame (@pxref{Selection, ,Selecting a -frame}), and any other frames inside of it, leaving its caller as the -innermost remaining frame. That frame becomes selected. The -specified value is stored in the registers used for returning values -of functions. - -The @code{return} command does not resume execution; it leaves the -program stopped in the state that would exist if the function had just -returned. In contrast, the @code{finish} command (@pxref{Continuing -and Stepping, ,Continuing and stepping}) resumes execution until the -selected stack frame returns naturally. - -@node Calling -@section Calling program functions - -@cindex calling functions -@kindex call -@table @code -@item call @var{expr} -Evaluate the expression @var{expr} without displaying @code{void} -returned values. -@end table - -You can use this variant of the @code{print} command if you want to -execute a function from your program, but without cluttering the output -with @code{void} returned values. If the result is not void, it -is printed and saved in the value history. - -@c OBSOLETE For the A29K, a user-controlled variable @code{call_scratch_address}, -@c OBSOLETE specifies the location of a scratch area to be used when @value{GDBN} -@c OBSOLETE calls a function in the target. This is necessary because the usual -@c OBSOLETE method of putting the scratch area on the stack does not work in systems -@c OBSOLETE that have separate instruction and data spaces. - -@node Patching -@section Patching programs - -@cindex patching binaries -@cindex writing into executables -@cindex writing into corefiles - -By default, @value{GDBN} opens the file containing your program's -executable code (or the corefile) read-only. This prevents accidental -alterations to machine code; but it also prevents you from intentionally -patching your program's binary. - -If you'd like to be able to patch the binary, you can specify that -explicitly with the @code{set write} command. For example, you might -want to turn on internal debugging flags, or even to make emergency -repairs. - -@table @code -@kindex set write -@item set write on -@itemx set write off -If you specify @samp{set write on}, @value{GDBN} opens executable and -core files for both reading and writing; if you specify @samp{set write -off} (the default), @value{GDBN} opens them read-only. - -If you have already loaded a file, you must load it again (using the -@code{exec-file} or @code{core-file} command) after changing @code{set -write}, for your new setting to take effect. - -@item show write -@kindex show write -Display whether executable files and core files are opened for writing -as well as reading. -@end table - -@node GDB Files -@chapter @value{GDBN} Files - -@value{GDBN} needs to know the file name of the program to be debugged, -both in order to read its symbol table and in order to start your -program. To debug a core dump of a previous run, you must also tell -@value{GDBN} the name of the core dump file. - -@menu -* Files:: Commands to specify files -* Symbol Errors:: Errors reading symbol files -@end menu - -@node Files -@section Commands to specify files - -@cindex symbol table -@cindex core dump file - -You may want to specify executable and core dump file names. The usual -way to do this is at start-up time, using the arguments to -@value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and -Out of @value{GDBN}}). - -Occasionally it is necessary to change to a different file during a -@value{GDBN} session. Or you may run @value{GDBN} and forget to specify -a file you want to use. In these situations the @value{GDBN} commands -to specify new files are useful. - -@table @code -@cindex executable file -@kindex file -@item file @var{filename} -Use @var{filename} as the program to be debugged. It is read for its -symbols and for the contents of pure memory. It is also the program -executed when you use the @code{run} command. If you do not specify a -directory and the file is not found in the @value{GDBN} working directory, -@value{GDBN} uses the environment variable @code{PATH} as a list of -directories to search, just as the shell does when looking for a program -to run. You can change the value of this variable, for both @value{GDBN} -and your program, using the @code{path} command. - -On systems with memory-mapped files, an auxiliary file named -@file{@var{filename}.syms} may hold symbol table information for -@var{filename}. If so, @value{GDBN} maps in the symbol table from -@file{@var{filename}.syms}, starting up more quickly. See the -descriptions of the file options @samp{-mapped} and @samp{-readnow} -(available on the command line, and with the commands @code{file}, -@code{symbol-file}, or @code{add-symbol-file}, described below), -for more information. - -@item file -@code{file} with no argument makes @value{GDBN} discard any information it -has on both executable file and the symbol table. - -@kindex exec-file -@item exec-file @r{[} @var{filename} @r{]} -Specify that the program to be run (but not the symbol table) is found -in @var{filename}. @value{GDBN} searches the environment variable @code{PATH} -if necessary to locate your program. Omitting @var{filename} means to -discard information on the executable file. - -@kindex symbol-file -@item symbol-file @r{[} @var{filename} @r{]} -Read symbol table information from file @var{filename}. @code{PATH} is -searched when necessary. Use the @code{file} command to get both symbol -table and program to run from the same file. - -@code{symbol-file} with no argument clears out @value{GDBN} information on your -program's symbol table. - -The @code{symbol-file} command causes @value{GDBN} to forget the contents -of its convenience variables, the value history, and all breakpoints and -auto-display expressions. This is because they may contain pointers to -the internal data recording symbols and data types, which are part of -the old symbol table data being discarded inside @value{GDBN}. - -@code{symbol-file} does not repeat if you press @key{RET} again after -executing it once. - -When @value{GDBN} is configured for a particular environment, it -understands debugging information in whatever format is the standard -generated for that environment; you may use either a @sc{gnu} compiler, or -other compilers that adhere to the local conventions. -Best results are usually obtained from @sc{gnu} compilers; for example, -using @code{@value{GCC}} you can generate debugging information for -optimized code. - -For most kinds of object files, with the exception of old SVR3 systems -using COFF, the @code{symbol-file} command does not normally read the -symbol table in full right away. Instead, it scans the symbol table -quickly to find which source files and which symbols are present. The -details are read later, one source file at a time, as they are needed. - -The purpose of this two-stage reading strategy is to make @value{GDBN} -start up faster. For the most part, it is invisible except for -occasional pauses while the symbol table details for a particular source -file are being read. (The @code{set verbose} command can turn these -pauses into messages if desired. @xref{Messages/Warnings, ,Optional -warnings and messages}.) - -We have not implemented the two-stage strategy for COFF yet. When the -symbol table is stored in COFF format, @code{symbol-file} reads the -symbol table data in full right away. Note that ``stabs-in-COFF'' -still does the two-stage strategy, since the debug info is actually -in stabs format. - -@kindex readnow -@cindex reading symbols immediately -@cindex symbols, reading immediately -@kindex mapped -@cindex memory-mapped symbol file -@cindex saving symbol table -@item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]} -@itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]} -You can override the @value{GDBN} two-stage strategy for reading symbol -tables by using the @samp{-readnow} option with any of the commands that -load symbol table information, if you want to be sure @value{GDBN} has the -entire symbol table available. - -If memory-mapped files are available on your system through the -@code{mmap} system call, you can use another option, @samp{-mapped}, to -cause @value{GDBN} to write the symbols for your program into a reusable -file. Future @value{GDBN} debugging sessions map in symbol information -from this auxiliary symbol file (if the program has not changed), rather -than spending time reading the symbol table from the executable -program. Using the @samp{-mapped} option has the same effect as -starting @value{GDBN} with the @samp{-mapped} command-line option. - -You can use both options together, to make sure the auxiliary symbol -file has all the symbol information for your program. - -The auxiliary symbol file for a program called @var{myprog} is called -@samp{@var{myprog}.syms}. Once this file exists (so long as it is newer -than the corresponding executable), @value{GDBN} always attempts to use -it when you debug @var{myprog}; no special options or commands are -needed. - -The @file{.syms} file is specific to the host machine where you run -@value{GDBN}. It holds an exact image of the internal @value{GDBN} -symbol table. It cannot be shared across multiple host platforms. - -@c FIXME: for now no mention of directories, since this seems to be in -@c flux. 13mar1992 status is that in theory GDB would look either in -@c current dir or in same dir as myprog; but issues like competing -@c GDB's, or clutter in system dirs, mean that in practice right now -@c only current dir is used. FFish says maybe a special GDB hierarchy -@c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol -@c files. - -@kindex core -@kindex core-file -@item core-file @r{[} @var{filename} @r{]} -Specify the whereabouts of a core dump file to be used as the ``contents -of memory''. Traditionally, core files contain only some parts of the -address space of the process that generated them; @value{GDBN} can access the -executable file itself for other parts. - -@code{core-file} with no argument specifies that no core file is -to be used. - -Note that the core file is ignored when your program is actually running -under @value{GDBN}. So, if you have been running your program and you -wish to debug a core file instead, you must kill the subprocess in which -the program is running. To do this, use the @code{kill} command -(@pxref{Kill Process, ,Killing the child process}). - -@kindex add-symbol-file -@cindex dynamic linking -@item add-symbol-file @var{filename} @var{address} -@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]} -@itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{} -The @code{add-symbol-file} command reads additional symbol table -information from the file @var{filename}. You would use this command -when @var{filename} has been dynamically loaded (by some other means) -into the program that is running. @var{address} should be the memory -address at which the file has been loaded; @value{GDBN} cannot figure -this out for itself. You can additionally specify an arbitrary number -of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit -section name and base address for that section. You can specify any -@var{address} as an expression. - -The symbol table of the file @var{filename} is added to the symbol table -originally read with the @code{symbol-file} command. You can use the -@code{add-symbol-file} command any number of times; the new symbol data -thus read keeps adding to the old. To discard all old symbol data -instead, use the @code{symbol-file} command without any arguments. - -@cindex relocatable object files, reading symbols from -@cindex object files, relocatable, reading symbols from -@cindex reading symbols from relocatable object files -@cindex symbols, reading from relocatable object files -@cindex @file{.o} files, reading symbols from -Although @var{filename} is typically a shared library file, an -executable file, or some other object file which has been fully -relocated for loading into a process, you can also load symbolic -information from relocatable @file{.o} files, as long as: - -@itemize @bullet -@item -the file's symbolic information refers only to linker symbols defined in -that file, not to symbols defined by other object files, -@item -every section the file's symbolic information refers to has actually -been loaded into the inferior, as it appears in the file, and -@item -you can determine the address at which every section was loaded, and -provide these to the @code{add-symbol-file} command. -@end itemize - -@noindent -Some embedded operating systems, like Sun Chorus and VxWorks, can load -relocatable files into an already running program; such systems -typically make the requirements above easy to meet. However, it's -important to recognize that many native systems use complex link -procedures (@code{.linkonce} section factoring and C++ constructor table -assembly, for example) that make the requirements difficult to meet. In -general, one cannot assume that using @code{add-symbol-file} to read a -relocatable object file's symbolic information will have the same effect -as linking the relocatable object file into the program in the normal -way. - -@code{add-symbol-file} does not repeat if you press @key{RET} after using it. - -You can use the @samp{-mapped} and @samp{-readnow} options just as with -the @code{symbol-file} command, to change how @value{GDBN} manages the symbol -table information for @var{filename}. - -@kindex add-shared-symbol-file -@item add-shared-symbol-file -The @code{add-shared-symbol-file} command can be used only under Harris' CXUX -operating system for the Motorola 88k. @value{GDBN} automatically looks for -shared libraries, however if @value{GDBN} does not find yours, you can run -@code{add-shared-symbol-file}. It takes no arguments. - -@kindex section -@item section -The @code{section} command changes the base address of section SECTION of -the exec file to ADDR. This can be used if the exec file does not contain -section addresses, (such as in the a.out format), or when the addresses -specified in the file itself are wrong. Each section must be changed -separately. The @code{info files} command, described below, lists all -the sections and their addresses. - -@kindex info files -@kindex info target -@item info files -@itemx info target -@code{info files} and @code{info target} are synonymous; both print the -current target (@pxref{Targets, ,Specifying a Debugging Target}), -including the names of the executable and core dump files currently in -use by @value{GDBN}, and the files from which symbols were loaded. The -command @code{help target} lists all possible targets rather than -current ones. - -@kindex maint info sections -@item maint info sections -Another command that can give you extra information about program sections -is @code{maint info sections}. In addition to the section information -displayed by @code{info files}, this command displays the flags and file -offset of each section in the executable and core dump files. In addition, -@code{maint info sections} provides the following command options (which -may be arbitrarily combined): - -@table @code -@item ALLOBJ -Display sections for all loaded object files, including shared libraries. -@item @var{sections} -Display info only for named @var{sections}. -@item @var{section-flags} -Display info only for sections for which @var{section-flags} are true. -The section flags that @value{GDBN} currently knows about are: -@table @code -@item ALLOC -Section will have space allocated in the process when loaded. -Set for all sections except those containing debug information. -@item LOAD -Section will be loaded from the file into the child process memory. -Set for pre-initialized code and data, clear for @code{.bss} sections. -@item RELOC -Section needs to be relocated before loading. -@item READONLY -Section cannot be modified by the child process. -@item CODE -Section contains executable code only. -@item DATA -Section contains data only (no executable code). -@item ROM -Section will reside in ROM. -@item CONSTRUCTOR -Section contains data for constructor/destructor lists. -@item HAS_CONTENTS -Section is not empty. -@item NEVER_LOAD -An instruction to the linker to not output the section. -@item COFF_SHARED_LIBRARY -A notification to the linker that the section contains -COFF shared library information. -@item IS_COMMON -Section contains common symbols. -@end table -@end table -@kindex set trust-readonly-sections -@item set trust-readonly-sections on -Tell @value{GDBN} that readonly sections in your object file -really are read-only (i.e.@: that their contents will not change). -In that case, @value{GDBN} can fetch values from these sections -out of the object file, rather than from the target program. -For some targets (notably embedded ones), this can be a significant -enhancement to debugging performance. - -The default is off. - -@item set trust-readonly-sections off -Tell @value{GDBN} not to trust readonly sections. This means that -the contents of the section might change while the program is running, -and must therefore be fetched from the target when needed. -@end table - -All file-specifying commands allow both absolute and relative file names -as arguments. @value{GDBN} always converts the file name to an absolute file -name and remembers it that way. - -@cindex shared libraries -@value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared -libraries. - -@value{GDBN} automatically loads symbol definitions from shared libraries -when you use the @code{run} command, or when you examine a core file. -(Before you issue the @code{run} command, @value{GDBN} does not understand -references to a function in a shared library, however---unless you are -debugging a core file). - -On HP-UX, if the program loads a library explicitly, @value{GDBN} -automatically loads the symbols at the time of the @code{shl_load} call. - -@c FIXME: some @value{GDBN} release may permit some refs to undef -@c FIXME...symbols---eg in a break cmd---assuming they are from a shared -@c FIXME...lib; check this from time to time when updating manual - -There are times, however, when you may wish to not automatically load -symbol definitions from shared libraries, such as when they are -particularly large or there are many of them. - -To control the automatic loading of shared library symbols, use the -commands: - -@table @code -@kindex set auto-solib-add -@item set auto-solib-add @var{mode} -If @var{mode} is @code{on}, symbols from all shared object libraries -will be loaded automatically when the inferior begins execution, you -attach to an independently started inferior, or when the dynamic linker -informs @value{GDBN} that a new library has been loaded. If @var{mode} -is @code{off}, symbols must be loaded manually, using the -@code{sharedlibrary} command. The default value is @code{on}. - -@kindex show auto-solib-add -@item show auto-solib-add -Display the current autoloading mode. -@end table - -To explicitly load shared library symbols, use the @code{sharedlibrary} -command: - -@table @code -@kindex info sharedlibrary -@kindex info share -@item info share -@itemx info sharedlibrary -Print the names of the shared libraries which are currently loaded. - -@kindex sharedlibrary -@kindex share -@item sharedlibrary @var{regex} -@itemx share @var{regex} -Load shared object library symbols for files matching a -Unix regular expression. -As with files loaded automatically, it only loads shared libraries -required by your program for a core file or after typing @code{run}. If -@var{regex} is omitted all shared libraries required by your program are -loaded. -@end table - -On some systems, such as HP-UX systems, @value{GDBN} supports -autoloading shared library symbols until a limiting threshold size is -reached. This provides the benefit of allowing autoloading to remain on -by default, but avoids autoloading excessively large shared libraries, -up to a threshold that is initially set, but which you can modify if you -wish. - -Beyond that threshold, symbols from shared libraries must be explicitly -loaded. To load these symbols, use the command @code{sharedlibrary -@var{filename}}. The base address of the shared library is determined -automatically by @value{GDBN} and need not be specified. - -To display or set the threshold, use the commands: - -@table @code -@kindex set auto-solib-limit -@item set auto-solib-limit @var{threshold} -Set the autoloading size threshold, in an integral number of megabytes. -If @var{threshold} is nonzero and shared library autoloading is enabled, -symbols from all shared object libraries will be loaded until the total -size of the loaded shared library symbols exceeds this threshold. -Otherwise, symbols must be loaded manually, using the -@code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100 -Mb). - -@kindex show auto-solib-limit -@item show auto-solib-limit -Display the current autoloading size threshold, in megabytes. -@end table - -@node Symbol Errors -@section Errors reading symbol files - -While reading a symbol file, @value{GDBN} occasionally encounters problems, -such as symbol types it does not recognize, or known bugs in compiler -output. By default, @value{GDBN} does not notify you of such problems, since -they are relatively common and primarily of interest to people -debugging compilers. If you are interested in seeing information -about ill-constructed symbol tables, you can either ask @value{GDBN} to print -only one message about each such type of problem, no matter how many -times the problem occurs; or you can ask @value{GDBN} to print more messages, -to see how many times the problems occur, with the @code{set -complaints} command (@pxref{Messages/Warnings, ,Optional warnings and -messages}). - -The messages currently printed, and their meanings, include: - -@table @code -@item inner block not inside outer block in @var{symbol} - -The symbol information shows where symbol scopes begin and end -(such as at the start of a function or a block of statements). This -error indicates that an inner scope block is not fully contained -in its outer scope blocks. - -@value{GDBN} circumvents the problem by treating the inner block as if it had -the same scope as the outer block. In the error message, @var{symbol} -may be shown as ``@code{(don't know)}'' if the outer block is not a -function. - -@item block at @var{address} out of order - -The symbol information for symbol scope blocks should occur in -order of increasing addresses. This error indicates that it does not -do so. - -@value{GDBN} does not circumvent this problem, and has trouble -locating symbols in the source file whose symbols it is reading. (You -can often determine what source file is affected by specifying -@code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and -messages}.) - -@item bad block start address patched - -The symbol information for a symbol scope block has a start address -smaller than the address of the preceding source line. This is known -to occur in the SunOS 4.1.1 (and earlier) C compiler. - -@value{GDBN} circumvents the problem by treating the symbol scope block as -starting on the previous source line. - -@item bad string table offset in symbol @var{n} - -@cindex foo -Symbol number @var{n} contains a pointer into the string table which is -larger than the size of the string table. - -@value{GDBN} circumvents the problem by considering the symbol to have the -name @code{foo}, which may cause other problems if many symbols end up -with this name. - -@item unknown symbol type @code{0x@var{nn}} - -The symbol information contains new data types that @value{GDBN} does -not yet know how to read. @code{0x@var{nn}} is the symbol type of the -uncomprehended information, in hexadecimal. - -@value{GDBN} circumvents the error by ignoring this symbol information. -This usually allows you to debug your program, though certain symbols -are not accessible. If you encounter such a problem and feel like -debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint -on @code{complain}, then go up to the function @code{read_dbx_symtab} -and examine @code{*bufp} to see the symbol. - -@item stub type has NULL name - -@value{GDBN} could not find the full definition for a struct or class. - -@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{} -The symbol information for a C@t{++} member function is missing some -information that recent versions of the compiler should have output for -it. - -@item info mismatch between compiler and debugger - -@value{GDBN} could not parse a type specification output by the compiler. - -@end table - -@node Targets -@chapter Specifying a Debugging Target - -@cindex debugging target -@kindex target - -A @dfn{target} is the execution environment occupied by your program. - -Often, @value{GDBN} runs in the same host environment as your program; -in that case, the debugging target is specified as a side effect when -you use the @code{file} or @code{core} commands. When you need more -flexibility---for example, running @value{GDBN} on a physically separate -host, or controlling a standalone system over a serial port or a -realtime system over a TCP/IP connection---you can use the @code{target} -command to specify one of the target types configured for @value{GDBN} -(@pxref{Target Commands, ,Commands for managing targets}). - -@menu -* Active Targets:: Active targets -* Target Commands:: Commands for managing targets -* Byte Order:: Choosing target byte order -* Remote:: Remote debugging -* KOD:: Kernel Object Display - -@end menu - -@node Active Targets -@section Active targets - -@cindex stacking targets -@cindex active targets -@cindex multiple targets - -There are three classes of targets: processes, core files, and -executable files. @value{GDBN} can work concurrently on up to three -active targets, one in each class. This allows you to (for example) -start a process and inspect its activity without abandoning your work on -a core file. - -For example, if you execute @samp{gdb a.out}, then the executable file -@code{a.out} is the only active target. If you designate a core file as -well---presumably from a prior run that crashed and coredumped---then -@value{GDBN} has two active targets and uses them in tandem, looking -first in the corefile target, then in the executable file, to satisfy -requests for memory addresses. (Typically, these two classes of target -are complementary, since core files contain only a program's -read-write memory---variables and so on---plus machine status, while -executable files contain only the program text and initialized data.) - -When you type @code{run}, your executable file becomes an active process -target as well. When a process target is active, all @value{GDBN} -commands requesting memory addresses refer to that target; addresses in -an active core file or executable file target are obscured while the -process target is active. - -Use the @code{core-file} and @code{exec-file} commands to select a new -core file or executable target (@pxref{Files, ,Commands to specify -files}). To specify as a target a process that is already running, use -the @code{attach} command (@pxref{Attach, ,Debugging an already-running -process}). - -@node Target Commands -@section Commands for managing targets - -@table @code -@item target @var{type} @var{parameters} -Connects the @value{GDBN} host environment to a target machine or -process. A target is typically a protocol for talking to debugging -facilities. You use the argument @var{type} to specify the type or -protocol of the target machine. - -Further @var{parameters} are interpreted by the target protocol, but -typically include things like device names or host names to connect -with, process numbers, and baud rates. - -The @code{target} command does not repeat if you press @key{RET} again -after executing the command. - -@kindex help target -@item help target -Displays the names of all targets available. To display targets -currently selected, use either @code{info target} or @code{info files} -(@pxref{Files, ,Commands to specify files}). - -@item help target @var{name} -Describe a particular target, including any parameters necessary to -select it. - -@kindex set gnutarget -@item set gnutarget @var{args} -@value{GDBN} uses its own library BFD to read your files. @value{GDBN} -knows whether it is reading an @dfn{executable}, -a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format -with the @code{set gnutarget} command. Unlike most @code{target} commands, -with @code{gnutarget} the @code{target} refers to a program, not a machine. - -@quotation -@emph{Warning:} To specify a file format with @code{set gnutarget}, -you must know the actual BFD name. -@end quotation - -@noindent -@xref{Files, , Commands to specify files}. - -@kindex show gnutarget -@item show gnutarget -Use the @code{show gnutarget} command to display what file format -@code{gnutarget} is set to read. If you have not set @code{gnutarget}, -@value{GDBN} will determine the file format for each file automatically, -and @code{show gnutarget} displays @samp{The current BDF target is "auto"}. -@end table - -Here are some common targets (available, or not, depending on the GDB -configuration): - -@table @code -@kindex target exec -@item target exec @var{program} -An executable file. @samp{target exec @var{program}} is the same as -@samp{exec-file @var{program}}. - -@kindex target core -@item target core @var{filename} -A core dump file. @samp{target core @var{filename}} is the same as -@samp{core-file @var{filename}}. - -@kindex target remote -@item target remote @var{dev} -Remote serial target in GDB-specific protocol. The argument @var{dev} -specifies what serial device to use for the connection (e.g. -@file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote} -supports the @code{load} command. This is only useful if you have -some other way of getting the stub to the target system, and you can put -it somewhere in memory where it won't get clobbered by the download. - -@kindex target sim -@item target sim -Builtin CPU simulator. @value{GDBN} includes simulators for most architectures. -In general, -@example - target sim - load - run -@end example -@noindent -works; however, you cannot assume that a specific memory map, device -drivers, or even basic I/O is available, although some simulators do -provide these. For info about any processor-specific simulator details, -see the appropriate section in @ref{Embedded Processors, ,Embedded -Processors}. - -@end table - -Some configurations may include these targets as well: - -@table @code - -@kindex target nrom -@item target nrom @var{dev} -NetROM ROM emulator. This target only supports downloading. - -@end table - -Different targets are available on different configurations of @value{GDBN}; -your configuration may have more or fewer targets. - -Many remote targets require you to download the executable's code -once you've successfully established a connection. - -@table @code - -@kindex load @var{filename} -@item load @var{filename} -Depending on what remote debugging facilities are configured into -@value{GDBN}, the @code{load} command may be available. Where it exists, it -is meant to make @var{filename} (an executable) available for debugging -on the remote system---by downloading, or dynamic linking, for example. -@code{load} also records the @var{filename} symbol table in @value{GDBN}, like -the @code{add-symbol-file} command. - -If your @value{GDBN} does not have a @code{load} command, attempting to -execute it gets the error message ``@code{You can't do that when your -target is @dots{}}'' - -The file is loaded at whatever address is specified in the executable. -For some object file formats, you can specify the load address when you -link the program; for other formats, like a.out, the object file format -specifies a fixed address. -@c FIXME! This would be a good place for an xref to the GNU linker doc. - -@code{load} does not repeat if you press @key{RET} again after using it. -@end table - -@node Byte Order -@section Choosing target byte order - -@cindex choosing target byte order -@cindex target byte order - -Some types of processors, such as the MIPS, PowerPC, and Hitachi SH, -offer the ability to run either big-endian or little-endian byte -orders. Usually the executable or symbol will include a bit to -designate the endian-ness, and you will not need to worry about -which to use. However, you may still find it useful to adjust -@value{GDBN}'s idea of processor endian-ness manually. - -@table @code -@kindex set endian big -@item set endian big -Instruct @value{GDBN} to assume the target is big-endian. - -@kindex set endian little -@item set endian little -Instruct @value{GDBN} to assume the target is little-endian. - -@kindex set endian auto -@item set endian auto -Instruct @value{GDBN} to use the byte order associated with the -executable. - -@item show endian -Display @value{GDBN}'s current idea of the target byte order. - -@end table - -Note that these commands merely adjust interpretation of symbolic -data on the host, and that they have absolutely no effect on the -target system. - -@node Remote -@section Remote debugging -@cindex remote debugging - -If you are trying to debug a program running on a machine that cannot run -@value{GDBN} in the usual way, it is often useful to use remote debugging. -For example, you might use remote debugging on an operating system kernel, -or on a small system which does not have a general purpose operating system -powerful enough to run a full-featured debugger. - -Some configurations of @value{GDBN} have special serial or TCP/IP interfaces -to make this work with particular debugging targets. In addition, -@value{GDBN} comes with a generic serial protocol (specific to @value{GDBN}, -but not specific to any particular target system) which you can use if you -write the remote stubs---the code that runs on the remote system to -communicate with @value{GDBN}. - -Other remote targets may be available in your -configuration of @value{GDBN}; use @code{help target} to list them. - -@node KOD -@section Kernel Object Display - -@cindex kernel object display -@cindex kernel object -@cindex KOD - -Some targets support kernel object display. Using this facility, -@value{GDBN} communicates specially with the underlying operating system -and can display information about operating system-level objects such as -mutexes and other synchronization objects. Exactly which objects can be -displayed is determined on a per-OS basis. - -Use the @code{set os} command to set the operating system. This tells -@value{GDBN} which kernel object display module to initialize: - -@example -(@value{GDBP}) set os cisco -@end example - -If @code{set os} succeeds, @value{GDBN} will display some information -about the operating system, and will create a new @code{info} command -which can be used to query the target. The @code{info} command is named -after the operating system: - -@example -(@value{GDBP}) info cisco -List of Cisco Kernel Objects -Object Description -any Any and all objects -@end example - -Further subcommands can be used to query about particular objects known -by the kernel. - -There is currently no way to determine whether a given operating system -is supported other than to try it. - - -@node Remote Debugging -@chapter Debugging remote programs - -@menu -* Server:: Using the gdbserver program -* NetWare:: Using the gdbserve.nlm program -* remote stub:: Implementing a remote stub -@end menu - -@node Server -@section Using the @code{gdbserver} program - -@kindex gdbserver -@cindex remote connection without stubs -@code{gdbserver} is a control program for Unix-like systems, which -allows you to connect your program with a remote @value{GDBN} via -@code{target remote}---but without linking in the usual debugging stub. - -@code{gdbserver} is not a complete replacement for the debugging stubs, -because it requires essentially the same operating-system facilities -that @value{GDBN} itself does. In fact, a system that can run -@code{gdbserver} to connect to a remote @value{GDBN} could also run -@value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless, -because it is a much smaller program than @value{GDBN} itself. It is -also easier to port than all of @value{GDBN}, so you may be able to get -started more quickly on a new system by using @code{gdbserver}. -Finally, if you develop code for real-time systems, you may find that -the tradeoffs involved in real-time operation make it more convenient to -do as much development work as possible on another system, for example -by cross-compiling. You can use @code{gdbserver} to make a similar -choice for debugging. - -@value{GDBN} and @code{gdbserver} communicate via either a serial line -or a TCP connection, using the standard @value{GDBN} remote serial -protocol. - -@table @emph -@item On the target machine, -you need to have a copy of the program you want to debug. -@code{gdbserver} does not need your program's symbol table, so you can -strip the program if necessary to save space. @value{GDBN} on the host -system does all the symbol handling. - -To use the server, you must tell it how to communicate with @value{GDBN}; -the name of your program; and the arguments for your program. The -syntax is: - -@smallexample -target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ] -@end smallexample - -@var{comm} is either a device name (to use a serial line) or a TCP -hostname and portnumber. For example, to debug Emacs with the argument -@samp{foo.txt} and communicate with @value{GDBN} over the serial port -@file{/dev/com1}: - -@smallexample -target> gdbserver /dev/com1 emacs foo.txt -@end smallexample - -@code{gdbserver} waits passively for the host @value{GDBN} to communicate -with it. - -To use a TCP connection instead of a serial line: - -@smallexample -target> gdbserver host:2345 emacs foo.txt -@end smallexample - -The only difference from the previous example is the first argument, -specifying that you are communicating with the host @value{GDBN} via -TCP. The @samp{host:2345} argument means that @code{gdbserver} is to -expect a TCP connection from machine @samp{host} to local TCP port 2345. -(Currently, the @samp{host} part is ignored.) You can choose any number -you want for the port number as long as it does not conflict with any -TCP ports already in use on the target system (for example, @code{23} is -reserved for @code{telnet}).@footnote{If you choose a port number that -conflicts with another service, @code{gdbserver} prints an error message -and exits.} You must use the same port number with the host @value{GDBN} -@code{target remote} command. - -@item On the @value{GDBN} host machine, -you need an unstripped copy of your program, since @value{GDBN} needs -symbols and debugging information. Start up @value{GDBN} as usual, -using the name of the local copy of your program as the first argument. -(You may also need the @w{@samp{--baud}} option if the serial line is -running at anything other than 9600@dmn{bps}.) After that, use @code{target -remote} to establish communications with @code{gdbserver}. Its argument -is either a device name (usually a serial device, like -@file{/dev/ttyb}), or a TCP port descriptor in the form -@code{@var{host}:@var{PORT}}. For example: - -@smallexample -(@value{GDBP}) target remote /dev/ttyb -@end smallexample - -@noindent -communicates with the server via serial line @file{/dev/ttyb}, and - -@smallexample -(@value{GDBP}) target remote the-target:2345 -@end smallexample - -@noindent -communicates via a TCP connection to port 2345 on host @w{@file{the-target}}. -For TCP connections, you must start up @code{gdbserver} prior to using -the @code{target remote} command. Otherwise you may get an error whose -text depends on the host system, but which usually looks something like -@samp{Connection refused}. -@end table - -@node NetWare -@section Using the @code{gdbserve.nlm} program - -@kindex gdbserve.nlm -@code{gdbserve.nlm} is a control program for NetWare systems, which -allows you to connect your program with a remote @value{GDBN} via -@code{target remote}. - -@value{GDBN} and @code{gdbserve.nlm} communicate via a serial line, -using the standard @value{GDBN} remote serial protocol. - -@table @emph -@item On the target machine, -you need to have a copy of the program you want to debug. -@code{gdbserve.nlm} does not need your program's symbol table, so you -can strip the program if necessary to save space. @value{GDBN} on the -host system does all the symbol handling. - -To use the server, you must tell it how to communicate with -@value{GDBN}; the name of your program; and the arguments for your -program. The syntax is: - -@smallexample -load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ] - [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ] -@end smallexample - -@var{board} and @var{port} specify the serial line; @var{baud} specifies -the baud rate used by the connection. @var{port} and @var{node} default -to 0, @var{baud} defaults to 9600@dmn{bps}. - -For example, to debug Emacs with the argument @samp{foo.txt}and -communicate with @value{GDBN} over serial port number 2 or board 1 -using a 19200@dmn{bps} connection: - -@smallexample -load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt -@end smallexample - -@item On the @value{GDBN} host machine, -you need an unstripped copy of your program, since @value{GDBN} needs -symbols and debugging information. Start up @value{GDBN} as usual, -using the name of the local copy of your program as the first argument. -(You may also need the @w{@samp{--baud}} option if the serial line is -running at anything other than 9600@dmn{bps}. After that, use @code{target -remote} to establish communications with @code{gdbserve.nlm}. Its -argument is a device name (usually a serial device, like -@file{/dev/ttyb}). For example: - -@smallexample -(@value{GDBP}) target remote /dev/ttyb -@end smallexample - -@noindent -communications with the server via serial line @file{/dev/ttyb}. -@end table - -@node remote stub -@section Implementing a remote stub - -@cindex debugging stub, example -@cindex remote stub, example -@cindex stub example, remote debugging -The stub files provided with @value{GDBN} implement the target side of the -communication protocol, and the @value{GDBN} side is implemented in the -@value{GDBN} source file @file{remote.c}. Normally, you can simply allow -these subroutines to communicate, and ignore the details. (If you're -implementing your own stub file, you can still ignore the details: start -with one of the existing stub files. @file{sparc-stub.c} is the best -organized, and therefore the easiest to read.) - -@cindex remote serial debugging, overview -To debug a program running on another machine (the debugging -@dfn{target} machine), you must first arrange for all the usual -prerequisites for the program to run by itself. For example, for a C -program, you need: - -@enumerate -@item -A startup routine to set up the C runtime environment; these usually -have a name like @file{crt0}. The startup routine may be supplied by -your hardware supplier, or you may have to write your own. - -@item -A C subroutine library to support your program's -subroutine calls, notably managing input and output. - -@item -A way of getting your program to the other machine---for example, a -download program. These are often supplied by the hardware -manufacturer, but you may have to write your own from hardware -documentation. -@end enumerate - -The next step is to arrange for your program to use a serial port to -communicate with the machine where @value{GDBN} is running (the @dfn{host} -machine). In general terms, the scheme looks like this: - -@table @emph -@item On the host, -@value{GDBN} already understands how to use this protocol; when everything -else is set up, you can simply use the @samp{target remote} command -(@pxref{Targets,,Specifying a Debugging Target}). - -@item On the target, -you must link with your program a few special-purpose subroutines that -implement the @value{GDBN} remote serial protocol. The file containing these -subroutines is called a @dfn{debugging stub}. - -On certain remote targets, you can use an auxiliary program -@code{gdbserver} instead of linking a stub into your program. -@xref{Server,,Using the @code{gdbserver} program}, for details. -@end table - -The debugging stub is specific to the architecture of the remote -machine; for example, use @file{sparc-stub.c} to debug programs on -@sc{sparc} boards. - -@cindex remote serial stub list -These working remote stubs are distributed with @value{GDBN}: - -@table @code - -@item i386-stub.c -@cindex @file{i386-stub.c} -@cindex Intel -@cindex i386 -For Intel 386 and compatible architectures. - -@item m68k-stub.c -@cindex @file{m68k-stub.c} -@cindex Motorola 680x0 -@cindex m680x0 -For Motorola 680x0 architectures. - -@item sh-stub.c -@cindex @file{sh-stub.c} -@cindex Hitachi -@cindex SH -For Hitachi SH architectures. - -@item sparc-stub.c -@cindex @file{sparc-stub.c} -@cindex Sparc -For @sc{sparc} architectures. - -@item sparcl-stub.c -@cindex @file{sparcl-stub.c} -@cindex Fujitsu -@cindex SparcLite -For Fujitsu @sc{sparclite} architectures. - -@end table - -The @file{README} file in the @value{GDBN} distribution may list other -recently added stubs. - -@menu -* Stub Contents:: What the stub can do for you -* Bootstrapping:: What you must do for the stub -* Debug Session:: Putting it all together -@end menu - -@node Stub Contents -@subsection What the stub can do for you - -@cindex remote serial stub -The debugging stub for your architecture supplies these three -subroutines: - -@table @code -@item set_debug_traps -@kindex set_debug_traps -@cindex remote serial stub, initialization -This routine arranges for @code{handle_exception} to run when your -program stops. You must call this subroutine explicitly near the -beginning of your program. - -@item handle_exception -@kindex handle_exception -@cindex remote serial stub, main routine -This is the central workhorse, but your program never calls it -explicitly---the setup code arranges for @code{handle_exception} to -run when a trap is triggered. - -@code{handle_exception} takes control when your program stops during -execution (for example, on a breakpoint), and mediates communications -with @value{GDBN} on the host machine. This is where the communications -protocol is implemented; @code{handle_exception} acts as the @value{GDBN} -representative on the target machine. It begins by sending summary -information on the state of your program, then continues to execute, -retrieving and transmitting any information @value{GDBN} needs, until you -execute a @value{GDBN} command that makes your program resume; at that point, -@code{handle_exception} returns control to your own code on the target -machine. - -@item breakpoint -@cindex @code{breakpoint} subroutine, remote -Use this auxiliary subroutine to make your program contain a -breakpoint. Depending on the particular situation, this may be the only -way for @value{GDBN} to get control. For instance, if your target -machine has some sort of interrupt button, you won't need to call this; -pressing the interrupt button transfers control to -@code{handle_exception}---in effect, to @value{GDBN}. On some machines, -simply receiving characters on the serial port may also trigger a trap; -again, in that situation, you don't need to call @code{breakpoint} from -your own program---simply running @samp{target remote} from the host -@value{GDBN} session gets control. - -Call @code{breakpoint} if none of these is true, or if you simply want -to make certain your program stops at a predetermined point for the -start of your debugging session. -@end table - -@node Bootstrapping -@subsection What you must do for the stub - -@cindex remote stub, support routines -The debugging stubs that come with @value{GDBN} are set up for a particular -chip architecture, but they have no information about the rest of your -debugging target machine. - -First of all you need to tell the stub how to communicate with the -serial port. - -@table @code -@item int getDebugChar() -@kindex getDebugChar -Write this subroutine to read a single character from the serial port. -It may be identical to @code{getchar} for your target system; a -different name is used to allow you to distinguish the two if you wish. - -@item void putDebugChar(int) -@kindex putDebugChar -Write this subroutine to write a single character to the serial port. -It may be identical to @code{putchar} for your target system; a -different name is used to allow you to distinguish the two if you wish. -@end table - -@cindex control C, and remote debugging -@cindex interrupting remote targets -If you want @value{GDBN} to be able to stop your program while it is -running, you need to use an interrupt-driven serial driver, and arrange -for it to stop when it receives a @code{^C} (@samp{\003}, the control-C -character). That is the character which @value{GDBN} uses to tell the -remote system to stop. - -Getting the debugging target to return the proper status to @value{GDBN} -probably requires changes to the standard stub; one quick and dirty way -is to just execute a breakpoint instruction (the ``dirty'' part is that -@value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}). - -Other routines you need to supply are: - -@table @code -@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address}) -@kindex exceptionHandler -Write this function to install @var{exception_address} in the exception -handling tables. You need to do this because the stub does not have any -way of knowing what the exception handling tables on your target system -are like (for example, the processor's table might be in @sc{rom}, -containing entries which point to a table in @sc{ram}). -@var{exception_number} is the exception number which should be changed; -its meaning is architecture-dependent (for example, different numbers -might represent divide by zero, misaligned access, etc). When this -exception occurs, control should be transferred directly to -@var{exception_address}, and the processor state (stack, registers, -and so on) should be just as it is when a processor exception occurs. So if -you want to use a jump instruction to reach @var{exception_address}, it -should be a simple jump, not a jump to subroutine. - -For the 386, @var{exception_address} should be installed as an interrupt -gate so that interrupts are masked while the handler runs. The gate -should be at privilege level 0 (the most privileged level). The -@sc{sparc} and 68k stubs are able to mask interrupts themselves without -help from @code{exceptionHandler}. - -@item void flush_i_cache() -@kindex flush_i_cache -On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the -instruction cache, if any, on your target machine. If there is no -instruction cache, this subroutine may be a no-op. - -On target machines that have instruction caches, @value{GDBN} requires this -function to make certain that the state of your program is stable. -@end table - -@noindent -You must also make sure this library routine is available: - -@table @code -@item void *memset(void *, int, int) -@kindex memset -This is the standard library function @code{memset} that sets an area of -memory to a known value. If you have one of the free versions of -@code{libc.a}, @code{memset} can be found there; otherwise, you must -either obtain it from your hardware manufacturer, or write your own. -@end table - -If you do not use the GNU C compiler, you may need other standard -library subroutines as well; this varies from one stub to another, -but in general the stubs are likely to use any of the common library -subroutines which @code{@value{GCC}} generates as inline code. - - -@node Debug Session -@subsection Putting it all together - -@cindex remote serial debugging summary -In summary, when your program is ready to debug, you must follow these -steps. - -@enumerate -@item -Make sure you have defined the supporting low-level routines -(@pxref{Bootstrapping,,What you must do for the stub}): -@display -@code{getDebugChar}, @code{putDebugChar}, -@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}. -@end display - -@item -Insert these lines near the top of your program: - -@example -set_debug_traps(); -breakpoint(); -@end example - -@item -For the 680x0 stub only, you need to provide a variable called -@code{exceptionHook}. Normally you just use: - -@example -void (*exceptionHook)() = 0; -@end example - -@noindent -but if before calling @code{set_debug_traps}, you set it to point to a -function in your program, that function is called when -@code{@value{GDBN}} continues after stopping on a trap (for example, bus -error). The function indicated by @code{exceptionHook} is called with -one parameter: an @code{int} which is the exception number. - -@item -Compile and link together: your program, the @value{GDBN} debugging stub for -your target architecture, and the supporting subroutines. - -@item -Make sure you have a serial connection between your target machine and -the @value{GDBN} host, and identify the serial port on the host. - -@item -@c The "remote" target now provides a `load' command, so we should -@c document that. FIXME. -Download your program to your target machine (or get it there by -whatever means the manufacturer provides), and start it. - -@item -To start remote debugging, run @value{GDBN} on the host machine, and specify -as an executable file the program that is running in the remote machine. -This tells @value{GDBN} how to find your program's symbols and the contents -of its pure text. - -@item -@cindex serial line, @code{target remote} -Establish communication using the @code{target remote} command. -Its argument specifies how to communicate with the target -machine---either via a devicename attached to a direct serial line, or a -TCP port (usually to a terminal server which in turn has a serial line -to the target). For example, to use a serial line connected to the -device named @file{/dev/ttyb}: - -@example -target remote /dev/ttyb -@end example - -@cindex TCP port, @code{target remote} -To use a TCP connection, use an argument of the form -@code{@var{host}:port}. For example, to connect to port 2828 on a -terminal server named @code{manyfarms}: - -@example -target remote manyfarms:2828 -@end example - -If your remote target is actually running on the same machine as -your debugger session (e.g.@: a simulator of your target running on -the same host), you can omit the hostname. For example, to connect -to port 1234 on your local machine: - -@example -target remote :1234 -@end example -@noindent - -Note that the colon is still required here. -@end enumerate - -Now you can use all the usual commands to examine and change data and to -step and continue the remote program. - -To resume the remote program and stop debugging it, use the @code{detach} -command. - -@cindex interrupting remote programs -@cindex remote programs, interrupting -Whenever @value{GDBN} is waiting for the remote program, if you type the -interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the -program. This may or may not succeed, depending in part on the hardware -and the serial drivers the remote system uses. If you type the -interrupt character once again, @value{GDBN} displays this prompt: - -@example -Interrupted while waiting for the program. -Give up (and stop debugging it)? (y or n) -@end example - -If you type @kbd{y}, @value{GDBN} abandons the remote debugging session. -(If you decide you want to try again later, you can use @samp{target -remote} again to connect once more.) If you type @kbd{n}, @value{GDBN} -goes back to waiting. - - -@node Configurations -@chapter Configuration-Specific Information - -While nearly all @value{GDBN} commands are available for all native and -cross versions of the debugger, there are some exceptions. This chapter -describes things that are only available in certain configurations. - -There are three major categories of configurations: native -configurations, where the host and target are the same, embedded -operating system configurations, which are usually the same for several -different processor architectures, and bare embedded processors, which -are quite different from each other. - -@menu -* Native:: -* Embedded OS:: -* Embedded Processors:: -* Architectures:: -@end menu - -@node Native -@section Native - -This section describes details specific to particular native -configurations. - -@menu -* HP-UX:: HP-UX -* SVR4 Process Information:: SVR4 process information -* DJGPP Native:: Features specific to the DJGPP port -@end menu - -@node HP-UX -@subsection HP-UX - -On HP-UX systems, if you refer to a function or variable name that -begins with a dollar sign, @value{GDBN} searches for a user or system -name first, before it searches for a convenience variable. - -@node SVR4 Process Information -@subsection SVR4 process information - -@kindex /proc -@cindex process image - -Many versions of SVR4 provide a facility called @samp{/proc} that can be -used to examine the image of a running process using file-system -subroutines. If @value{GDBN} is configured for an operating system with -this facility, the command @code{info proc} is available to report on -several kinds of information about the process running your program. -@code{info proc} works only on SVR4 systems that include the -@code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix, -and Unixware, but not HP-UX or Linux, for example. - -@table @code -@kindex info proc -@item info proc -Summarize available information about the process. - -@kindex info proc mappings -@item info proc mappings -Report on the address ranges accessible in the program, with information -on whether your program may read, write, or execute each range. -@ignore -@comment These sub-options of 'info proc' were not included when -@comment procfs.c was re-written. Keep their descriptions around -@comment against the day when someone finds the time to put them back in. -@kindex info proc times -@item info proc times -Starting time, user CPU time, and system CPU time for your program and -its children. - -@kindex info proc id -@item info proc id -Report on the process IDs related to your program: its own process ID, -the ID of its parent, the process group ID, and the session ID. - -@kindex info proc status -@item info proc status -General information on the state of the process. If the process is -stopped, this report includes the reason for stopping, and any signal -received. - -@item info proc all -Show all the above information about the process. -@end ignore -@end table - -@node DJGPP Native -@subsection Features for Debugging @sc{djgpp} Programs -@cindex @sc{djgpp} debugging -@cindex native @sc{djgpp} debugging -@cindex MS-DOS-specific commands - -@sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and -MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs -that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on -top of real-mode DOS systems and their emulations. - -@value{GDBN} supports native debugging of @sc{djgpp} programs, and -defines a few commands specific to the @sc{djgpp} port. This -subsection describes those commands. - -@table @code -@kindex info dos -@item info dos -This is a prefix of @sc{djgpp}-specific commands which print -information about the target system and important OS structures. - -@kindex sysinfo -@cindex MS-DOS system info -@cindex free memory information (MS-DOS) -@item info dos sysinfo -This command displays assorted information about the underlying -platform: the CPU type and features, the OS version and flavor, the -DPMI version, and the available conventional and DPMI memory. - -@cindex GDT -@cindex LDT -@cindex IDT -@cindex segment descriptor tables -@cindex descriptor tables display -@item info dos gdt -@itemx info dos ldt -@itemx info dos idt -These 3 commands display entries from, respectively, Global, Local, -and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor -tables are data structures which store a descriptor for each segment -that is currently in use. The segment's selector is an index into a -descriptor table; the table entry for that index holds the -descriptor's base address and limit, and its attributes and access -rights. - -A typical @sc{djgpp} program uses 3 segments: a code segment, a data -segment (used for both data and the stack), and a DOS segment (which -allows access to DOS/BIOS data structures and absolute addresses in -conventional memory). However, the DPMI host will usually define -additional segments in order to support the DPMI environment. - -@cindex garbled pointers -These commands allow to display entries from the descriptor tables. -Without an argument, all entries from the specified table are -displayed. An argument, which should be an integer expression, means -display a single entry whose index is given by the argument. For -example, here's a convenient way to display information about the -debugged program's data segment: - -@smallexample -@exdent @code{(@value{GDBP}) info dos ldt $ds} -@exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)} -@end smallexample - -@noindent -This comes in handy when you want to see whether a pointer is outside -the data segment's limit (i.e.@: @dfn{garbled}). - -@cindex page tables display (MS-DOS) -@item info dos pde -@itemx info dos pte -These two commands display entries from, respectively, the Page -Directory and the Page Tables. Page Directories and Page Tables are -data structures which control how virtual memory addresses are mapped -into physical addresses. A Page Table includes an entry for every -page of memory that is mapped into the program's address space; there -may be several Page Tables, each one holding up to 4096 entries. A -Page Directory has up to 4096 entries, one each for every Page Table -that is currently in use. - -Without an argument, @kbd{info dos pde} displays the entire Page -Directory, and @kbd{info dos pte} displays all the entries in all of -the Page Tables. An argument, an integer expression, given to the -@kbd{info dos pde} command means display only that entry from the Page -Directory table. An argument given to the @kbd{info dos pte} command -means display entries from a single Page Table, the one pointed to by -the specified entry in the Page Directory. - -@cindex direct memory access (DMA) on MS-DOS -These commands are useful when your program uses @dfn{DMA} (Direct -Memory Access), which needs physical addresses to program the DMA -controller. - -These commands are supported only with some DPMI servers. - -@cindex physical address from linear address -@item info dos address-pte @var{addr} -This command displays the Page Table entry for a specified linear -address. The argument linear address @var{addr} should already have the -appropriate segment's base address added to it, because this command -accepts addresses which may belong to @emph{any} segment. For -example, here's how to display the Page Table entry for the page where -the variable @code{i} is stored: - -@smallexample -@exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i} -@exdent @code{Page Table entry for address 0x11a00d30:} -@exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30} -@end smallexample - -@noindent -This says that @code{i} is stored at offset @code{0xd30} from the page -whose physical base address is @code{0x02698000}, and prints all the -attributes of that page. - -Note that you must cast the addresses of variables to a @code{char *}, -since otherwise the value of @code{__djgpp_base_address}, the base -address of all variables and functions in a @sc{djgpp} program, will -be added using the rules of C pointer arithmetics: if @code{i} is -declared an @code{int}, @value{GDBN} will add 4 times the value of -@code{__djgpp_base_address} to the address of @code{i}. - -Here's another example, it displays the Page Table entry for the -transfer buffer: - -@smallexample -@exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)} -@exdent @code{Page Table entry for address 0x29110:} -@exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110} -@end smallexample - -@noindent -(The @code{+ 3} offset is because the transfer buffer's address is the -3rd member of the @code{_go32_info_block} structure.) The output of -this command clearly shows that addresses in conventional memory are -mapped 1:1, i.e.@: the physical and linear addresses are identical. - -This command is supported only with some DPMI servers. -@end table - -@node Embedded OS -@section Embedded Operating Systems - -This section describes configurations involving the debugging of -embedded operating systems that are available for several different -architectures. - -@menu -* VxWorks:: Using @value{GDBN} with VxWorks -@end menu - -@value{GDBN} includes the ability to debug programs running on -various real-time operating systems. - -@node VxWorks -@subsection Using @value{GDBN} with VxWorks - -@cindex VxWorks - -@table @code - -@kindex target vxworks -@item target vxworks @var{machinename} -A VxWorks system, attached via TCP/IP. The argument @var{machinename} -is the target system's machine name or IP address. - -@end table - -On VxWorks, @code{load} links @var{filename} dynamically on the -current target system as well as adding its symbols in @value{GDBN}. - -@value{GDBN} enables developers to spawn and debug tasks running on networked -VxWorks targets from a Unix host. Already-running tasks spawned from -the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on -both the Unix host and on the VxWorks target. The program -@code{@value{GDBP}} is installed and executed on the Unix host. (It may be -installed with the name @code{vxgdb}, to distinguish it from a -@value{GDBN} for debugging programs on the host itself.) - -@table @code -@item VxWorks-timeout @var{args} -@kindex vxworks-timeout -All VxWorks-based targets now support the option @code{vxworks-timeout}. -This option is set by the user, and @var{args} represents the number of -seconds @value{GDBN} waits for responses to rpc's. You might use this if -your VxWorks target is a slow software simulator or is on the far side -of a thin network line. -@end table - -The following information on connecting to VxWorks was current when -this manual was produced; newer releases of VxWorks may use revised -procedures. - -@kindex INCLUDE_RDB -To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel -to include the remote debugging interface routines in the VxWorks -library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the -VxWorks configuration file @file{configAll.h} and rebuild your VxWorks -kernel. The resulting kernel contains @file{rdb.a}, and spawns the -source debugging task @code{tRdbTask} when VxWorks is booted. For more -information on configuring and remaking VxWorks, see the manufacturer's -manual. -@c VxWorks, see the @cite{VxWorks Programmer's Guide}. - -Once you have included @file{rdb.a} in your VxWorks system image and set -your Unix execution search path to find @value{GDBN}, you are ready to -run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or -@code{vxgdb}, depending on your installation). - -@value{GDBN} comes up showing the prompt: - -@example -(vxgdb) -@end example - -@menu -* VxWorks Connection:: Connecting to VxWorks -* VxWorks Download:: VxWorks download -* VxWorks Attach:: Running tasks -@end menu - -@node VxWorks Connection -@subsubsection Connecting to VxWorks - -The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the -network. To connect to a target whose host name is ``@code{tt}'', type: - -@example -(vxgdb) target vxworks tt -@end example - -@need 750 -@value{GDBN} displays messages like these: - -@smallexample -Attaching remote machine across net... -Connected to tt. -@end smallexample - -@need 1000 -@value{GDBN} then attempts to read the symbol tables of any object modules -loaded into the VxWorks target since it was last booted. @value{GDBN} locates -these files by searching the directories listed in the command search -path (@pxref{Environment, ,Your program's environment}); if it fails -to find an object file, it displays a message such as: - -@example -prog.o: No such file or directory. -@end example - -When this happens, add the appropriate directory to the search path with -the @value{GDBN} command @code{path}, and execute the @code{target} -command again. - -@node VxWorks Download -@subsubsection VxWorks download - -@cindex download to VxWorks -If you have connected to the VxWorks target and you want to debug an -object that has not yet been loaded, you can use the @value{GDBN} -@code{load} command to download a file from Unix to VxWorks -incrementally. The object file given as an argument to the @code{load} -command is actually opened twice: first by the VxWorks target in order -to download the code, then by @value{GDBN} in order to read the symbol -table. This can lead to problems if the current working directories on -the two systems differ. If both systems have NFS mounted the same -filesystems, you can avoid these problems by using absolute paths. -Otherwise, it is simplest to set the working directory on both systems -to the directory in which the object file resides, and then to reference -the file by its name, without any path. For instance, a program -@file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks -and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this -program, type this on VxWorks: - -@example --> cd "@var{vxpath}/vw/demo/rdb" -@end example - -@noindent -Then, in @value{GDBN}, type: - -@example -(vxgdb) cd @var{hostpath}/vw/demo/rdb -(vxgdb) load prog.o -@end example - -@value{GDBN} displays a response similar to this: - -@smallexample -Reading symbol data from wherever/vw/demo/rdb/prog.o... done. -@end smallexample - -You can also use the @code{load} command to reload an object module -after editing and recompiling the corresponding source file. Note that -this makes @value{GDBN} delete all currently-defined breakpoints, -auto-displays, and convenience variables, and to clear the value -history. (This is necessary in order to preserve the integrity of -debugger's data structures that reference the target system's symbol -table.) - -@node VxWorks Attach -@subsubsection Running tasks - -@cindex running VxWorks tasks -You can also attach to an existing task using the @code{attach} command as -follows: - -@example -(vxgdb) attach @var{task} -@end example - -@noindent -where @var{task} is the VxWorks hexadecimal task ID. The task can be running -or suspended when you attach to it. Running tasks are suspended at -the time of attachment. - -@node Embedded Processors -@section Embedded Processors - -This section goes into details specific to particular embedded -configurations. - - -@c OBSOLETE * A29K Embedded:: AMD A29K Embedded -@menu -* ARM:: ARM -* H8/300:: Hitachi H8/300 -* H8/500:: Hitachi H8/500 -* i960:: Intel i960 -* M32R/D:: Mitsubishi M32R/D -* M68K:: Motorola M68K -* M88K:: Motorola M88K -* MIPS Embedded:: MIPS Embedded -* PA:: HP PA Embedded -* PowerPC: PowerPC -* SH:: Hitachi SH -* Sparclet:: Tsqware Sparclet -* Sparclite:: Fujitsu Sparclite -* ST2000:: Tandem ST2000 -* Z8000:: Zilog Z8000 -@end menu - -@c OBSOLETE @node A29K Embedded -@c OBSOLETE @subsection AMD A29K Embedded -@c OBSOLETE -@c OBSOLETE @menu -@c OBSOLETE * A29K UDI:: -@c OBSOLETE * A29K EB29K:: -@c OBSOLETE * Comms (EB29K):: Communications setup -@c OBSOLETE * gdb-EB29K:: EB29K cross-debugging -@c OBSOLETE * Remote Log:: Remote log -@c OBSOLETE @end menu -@c OBSOLETE -@c OBSOLETE @table @code -@c OBSOLETE -@c OBSOLETE @kindex target adapt -@c OBSOLETE @item target adapt @var{dev} -@c OBSOLETE Adapt monitor for A29K. -@c OBSOLETE -@c OBSOLETE @kindex target amd-eb -@c OBSOLETE @item target amd-eb @var{dev} @var{speed} @var{PROG} -@c OBSOLETE @cindex AMD EB29K -@c OBSOLETE Remote PC-resident AMD EB29K board, attached over serial lines. -@c OBSOLETE @var{dev} is the serial device, as for @code{target remote}; -@c OBSOLETE @var{speed} allows you to specify the linespeed; and @var{PROG} is the -@c OBSOLETE name of the program to be debugged, as it appears to DOS on the PC. -@c OBSOLETE @xref{A29K EB29K, ,EBMON protocol for AMD29K}. -@c OBSOLETE -@c OBSOLETE @end table -@c OBSOLETE -@c OBSOLETE @node A29K UDI -@c OBSOLETE @subsubsection A29K UDI -@c OBSOLETE -@c OBSOLETE @cindex UDI -@c OBSOLETE @cindex AMD29K via UDI -@c OBSOLETE -@c OBSOLETE @value{GDBN} supports AMD's UDI (``Universal Debugger Interface'') -@c OBSOLETE protocol for debugging the a29k processor family. To use this -@c OBSOLETE configuration with AMD targets running the MiniMON monitor, you need the -@c OBSOLETE program @code{MONTIP}, available from AMD at no charge. You can also -@c OBSOLETE use @value{GDBN} with the UDI-conformant a29k simulator program -@c OBSOLETE @code{ISSTIP}, also available from AMD. -@c OBSOLETE -@c OBSOLETE @table @code -@c OBSOLETE @item target udi @var{keyword} -@c OBSOLETE @kindex udi -@c OBSOLETE Select the UDI interface to a remote a29k board or simulator, where -@c OBSOLETE @var{keyword} is an entry in the AMD configuration file @file{udi_soc}. -@c OBSOLETE This file contains keyword entries which specify parameters used to -@c OBSOLETE connect to a29k targets. If the @file{udi_soc} file is not in your -@c OBSOLETE working directory, you must set the environment variable @samp{UDICONF} -@c OBSOLETE to its pathname. -@c OBSOLETE @end table -@c OBSOLETE -@c OBSOLETE @node A29K EB29K -@c OBSOLETE @subsubsection EBMON protocol for AMD29K -@c OBSOLETE -@c OBSOLETE @cindex EB29K board -@c OBSOLETE @cindex running 29K programs -@c OBSOLETE -@c OBSOLETE AMD distributes a 29K development board meant to fit in a PC, together -@c OBSOLETE with a DOS-hosted monitor program called @code{EBMON}. As a shorthand -@c OBSOLETE term, this development system is called the ``EB29K''. To use -@c OBSOLETE @value{GDBN} from a Unix system to run programs on the EB29K board, you -@c OBSOLETE must first connect a serial cable between the PC (which hosts the EB29K -@c OBSOLETE board) and a serial port on the Unix system. In the following, we -@c OBSOLETE assume you've hooked the cable between the PC's @file{COM1} port and -@c OBSOLETE @file{/dev/ttya} on the Unix system. -@c OBSOLETE -@c OBSOLETE @node Comms (EB29K) -@c OBSOLETE @subsubsection Communications setup -@c OBSOLETE -@c OBSOLETE The next step is to set up the PC's port, by doing something like this -@c OBSOLETE in DOS on the PC: -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE C:\> MODE com1:9600,n,8,1,none -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE @noindent -@c OBSOLETE This example---run on an MS DOS 4.0 system---sets the PC port to 9600 -@c OBSOLETE bps, no parity, eight data bits, one stop bit, and no ``retry'' action; -@c OBSOLETE you must match the communications parameters when establishing the Unix -@c OBSOLETE end of the connection as well. -@c OBSOLETE @c FIXME: Who knows what this "no retry action" crud from the DOS manual may -@c OBSOLETE @c mean? It's optional; leave it out? ---doc@cygnus.com, 25feb91 -@c OBSOLETE @c -@c OBSOLETE @c It's optional, but it's unwise to omit it: who knows what is the -@c OBSOLETE @c default value set when the DOS machines boots? "No retry" means that -@c OBSOLETE @c the DOS serial device driver won't retry the operation if it fails; -@c OBSOLETE @c I understand that this is needed because the GDB serial protocol -@c OBSOLETE @c handles any errors and retransmissions itself. ---Eli Zaretskii, 3sep99 -@c OBSOLETE -@c OBSOLETE To give control of the PC to the Unix side of the serial line, type -@c OBSOLETE the following at the DOS console: -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE C:\> CTTY com1 -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE @noindent -@c OBSOLETE (Later, if you wish to return control to the DOS console, you can use -@c OBSOLETE the command @code{CTTY con}---but you must send it over the device that -@c OBSOLETE had control, in our example over the @file{COM1} serial line.) -@c OBSOLETE -@c OBSOLETE From the Unix host, use a communications program such as @code{tip} or -@c OBSOLETE @code{cu} to communicate with the PC; for example, -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE cu -s 9600 -l /dev/ttya -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE @noindent -@c OBSOLETE The @code{cu} options shown specify, respectively, the linespeed and the -@c OBSOLETE serial port to use. If you use @code{tip} instead, your command line -@c OBSOLETE may look something like the following: -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE tip -9600 /dev/ttya -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE @noindent -@c OBSOLETE Your system may require a different name where we show -@c OBSOLETE @file{/dev/ttya} as the argument to @code{tip}. The communications -@c OBSOLETE parameters, including which port to use, are associated with the -@c OBSOLETE @code{tip} argument in the ``remote'' descriptions file---normally the -@c OBSOLETE system table @file{/etc/remote}. -@c OBSOLETE @c FIXME: What if anything needs doing to match the "n,8,1,none" part of -@c OBSOLETE @c the DOS side's comms setup? cu can support -o (odd -@c OBSOLETE @c parity), -e (even parity)---apparently no settings for no parity or -@c OBSOLETE @c for character size. Taken from stty maybe...? John points out tip -@c OBSOLETE @c can set these as internal variables, eg ~s parity=none; man stty -@c OBSOLETE @c suggests that it *might* work to stty these options with stdin or -@c OBSOLETE @c stdout redirected... ---doc@cygnus.com, 25feb91 -@c OBSOLETE @c -@c OBSOLETE @c There's nothing to be done for the "none" part of the DOS MODE -@c OBSOLETE @c command. The rest of the parameters should be matched by the -@c OBSOLETE @c baudrate, bits, and parity used by the Unix side. ---Eli Zaretskii, 3Sep99 -@c OBSOLETE -@c OBSOLETE @kindex EBMON -@c OBSOLETE Using the @code{tip} or @code{cu} connection, change the DOS working -@c OBSOLETE directory to the directory containing a copy of your 29K program, then -@c OBSOLETE start the PC program @code{EBMON} (an EB29K control program supplied -@c OBSOLETE with your board by AMD). You should see an initial display from -@c OBSOLETE @code{EBMON} similar to the one that follows, ending with the -@c OBSOLETE @code{EBMON} prompt @samp{#}--- -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE C:\> G: -@c OBSOLETE -@c OBSOLETE G:\> CD \usr\joe\work29k -@c OBSOLETE -@c OBSOLETE G:\USR\JOE\WORK29K> EBMON -@c OBSOLETE Am29000 PC Coprocessor Board Monitor, version 3.0-18 -@c OBSOLETE Copyright 1990 Advanced Micro Devices, Inc. -@c OBSOLETE Written by Gibbons and Associates, Inc. -@c OBSOLETE -@c OBSOLETE Enter '?' or 'H' for help -@c OBSOLETE -@c OBSOLETE PC Coprocessor Type = EB29K -@c OBSOLETE I/O Base = 0x208 -@c OBSOLETE Memory Base = 0xd0000 -@c OBSOLETE -@c OBSOLETE Data Memory Size = 2048KB -@c OBSOLETE Available I-RAM Range = 0x8000 to 0x1fffff -@c OBSOLETE Available D-RAM Range = 0x80002000 to 0x801fffff -@c OBSOLETE -@c OBSOLETE PageSize = 0x400 -@c OBSOLETE Register Stack Size = 0x800 -@c OBSOLETE Memory Stack Size = 0x1800 -@c OBSOLETE -@c OBSOLETE CPU PRL = 0x3 -@c OBSOLETE Am29027 Available = No -@c OBSOLETE Byte Write Available = Yes -@c OBSOLETE -@c OBSOLETE # ~. -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE Then exit the @code{cu} or @code{tip} program (done in the example by -@c OBSOLETE typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} keeps -@c OBSOLETE running, ready for @value{GDBN} to take over. -@c OBSOLETE -@c OBSOLETE For this example, we've assumed what is probably the most convenient -@c OBSOLETE way to make sure the same 29K program is on both the PC and the Unix -@c OBSOLETE system: a PC/NFS connection that establishes ``drive @file{G:}'' on the -@c OBSOLETE PC as a file system on the Unix host. If you do not have PC/NFS or -@c OBSOLETE something similar connecting the two systems, you must arrange some -@c OBSOLETE other way---perhaps floppy-disk transfer---of getting the 29K program -@c OBSOLETE from the Unix system to the PC; @value{GDBN} does @emph{not} download it over the -@c OBSOLETE serial line. -@c OBSOLETE -@c OBSOLETE @node gdb-EB29K -@c OBSOLETE @subsubsection EB29K cross-debugging -@c OBSOLETE -@c OBSOLETE Finally, @code{cd} to the directory containing an image of your 29K -@c OBSOLETE program on the Unix system, and start @value{GDBN}---specifying as argument the -@c OBSOLETE name of your 29K program: -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE cd /usr/joe/work29k -@c OBSOLETE @value{GDBP} myfoo -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE @need 500 -@c OBSOLETE Now you can use the @code{target} command: -@c OBSOLETE -@c OBSOLETE @example -@c OBSOLETE target amd-eb /dev/ttya 9600 MYFOO -@c OBSOLETE @c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to -@c OBSOLETE @c emphasize that this is the name as seen by DOS (since I think DOS is -@c OBSOLETE @c single-minded about case of letters). ---doc@cygnus.com, 25feb91 -@c OBSOLETE @end example -@c OBSOLETE -@c OBSOLETE @noindent -@c OBSOLETE In this example, we've assumed your program is in a file called -@c OBSOLETE @file{myfoo}. Note that the filename given as the last argument to -@c OBSOLETE @code{target amd-eb} should be the name of the program as it appears to DOS. -@c OBSOLETE In our example this is simply @code{MYFOO}, but in general it can include -@c OBSOLETE a DOS path, and depending on your transfer mechanism may not resemble -@c OBSOLETE the name on the Unix side. -@c OBSOLETE -@c OBSOLETE At this point, you can set any breakpoints you wish; when you are ready -@c OBSOLETE to see your program run on the 29K board, use the @value{GDBN} command -@c OBSOLETE @code{run}. -@c OBSOLETE -@c OBSOLETE To stop debugging the remote program, use the @value{GDBN} @code{detach} -@c OBSOLETE command. -@c OBSOLETE -@c OBSOLETE To return control of the PC to its console, use @code{tip} or @code{cu} -@c OBSOLETE once again, after your @value{GDBN} session has concluded, to attach to -@c OBSOLETE @code{EBMON}. You can then type the command @code{q} to shut down -@c OBSOLETE @code{EBMON}, returning control to the DOS command-line interpreter. -@c OBSOLETE Type @kbd{CTTY con} to return command input to the main DOS console, -@c OBSOLETE and type @kbd{~.} to leave @code{tip} or @code{cu}. -@c OBSOLETE -@c OBSOLETE @node Remote Log -@c OBSOLETE @subsubsection Remote log -@c OBSOLETE @cindex @file{eb.log}, a log file for EB29K -@c OBSOLETE @cindex log file for EB29K -@c OBSOLETE -@c OBSOLETE The @code{target amd-eb} command creates a file @file{eb.log} in the -@c OBSOLETE current working directory, to help debug problems with the connection. -@c OBSOLETE @file{eb.log} records all the output from @code{EBMON}, including echoes -@c OBSOLETE of the commands sent to it. Running @samp{tail -f} on this file in -@c OBSOLETE another window often helps to understand trouble with @code{EBMON}, or -@c OBSOLETE unexpected events on the PC side of the connection. - -@node ARM -@subsection ARM - -@table @code - -@kindex target rdi -@item target rdi @var{dev} -ARM Angel monitor, via RDI library interface to ADP protocol. You may -use this target to communicate with both boards running the Angel -monitor, or with the EmbeddedICE JTAG debug device. - -@kindex target rdp -@item target rdp @var{dev} -ARM Demon monitor. - -@end table - -@node H8/300 -@subsection Hitachi H8/300 - -@table @code - -@kindex target hms@r{, with H8/300} -@item target hms @var{dev} -A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host. -Use special commands @code{device} and @code{speed} to control the serial -line and the communications speed used. - -@kindex target e7000@r{, with H8/300} -@item target e7000 @var{dev} -E7000 emulator for Hitachi H8 and SH. - -@kindex target sh3@r{, with H8/300} -@kindex target sh3e@r{, with H8/300} -@item target sh3 @var{dev} -@itemx target sh3e @var{dev} -Hitachi SH-3 and SH-3E target systems. - -@end table - -@cindex download to H8/300 or H8/500 -@cindex H8/300 or H8/500 download -@cindex download to Hitachi SH -@cindex Hitachi SH download -When you select remote debugging to a Hitachi SH, H8/300, or H8/500 -board, the @code{load} command downloads your program to the Hitachi -board and also opens it as the current executable target for -@value{GDBN} on your host (like the @code{file} command). - -@value{GDBN} needs to know these things to talk to your -Hitachi SH, H8/300, or H8/500: - -@enumerate -@item -that you want to use @samp{target hms}, the remote debugging interface -for Hitachi microprocessors, or @samp{target e7000}, the in-circuit -emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is -the default when @value{GDBN} is configured specifically for the Hitachi SH, -H8/300, or H8/500.) - -@item -what serial device connects your host to your Hitachi board (the first -serial device available on your host is the default). - -@item -what speed to use over the serial device. -@end enumerate - -@menu -* Hitachi Boards:: Connecting to Hitachi boards. -* Hitachi ICE:: Using the E7000 In-Circuit Emulator. -* Hitachi Special:: Special @value{GDBN} commands for Hitachi micros. -@end menu - -@node Hitachi Boards -@subsubsection Connecting to Hitachi boards - -@c only for Unix hosts -@kindex device -@cindex serial device, Hitachi micros -Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you -need to explicitly set the serial device. The default @var{port} is the -first available port on your host. This is only necessary on Unix -hosts, where it is typically something like @file{/dev/ttya}. - -@kindex speed -@cindex serial line speed, Hitachi micros -@code{@value{GDBN}} has another special command to set the communications -speed: @samp{speed @var{bps}}. This command also is only used from Unix -hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with -the DOS @code{mode} command (for instance, -@w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection). - -The @samp{device} and @samp{speed} commands are available only when you -use a Unix host to debug your Hitachi microprocessor programs. If you -use a DOS host, -@value{GDBN} depends on an auxiliary terminate-and-stay-resident program -called @code{asynctsr} to communicate with the development board -through a PC serial port. You must also use the DOS @code{mode} command -to set up the serial port on the DOS side. - -The following sample session illustrates the steps needed to start a -program under @value{GDBN} control on an H8/300. The example uses a -sample H8/300 program called @file{t.x}. The procedure is the same for -the Hitachi SH and the H8/500. - -First hook up your development board. In this example, we use a -board attached to serial port @code{COM2}; if you use a different serial -port, substitute its name in the argument of the @code{mode} command. -When you call @code{asynctsr}, the auxiliary comms program used by the -debugger, you give it just the numeric part of the serial port's name; -for example, @samp{asyncstr 2} below runs @code{asyncstr} on -@code{COM2}. - -@example -C:\H8300\TEST> asynctsr 2 -C:\H8300\TEST> mode com2:9600,n,8,1,p - -Resident portion of MODE loaded - -COM2: 9600, n, 8, 1, p - -@end example - -@quotation -@emph{Warning:} We have noticed a bug in PC-NFS that conflicts with -@code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to -disable it, or even boot without it, to use @code{asynctsr} to control -your development board. -@end quotation - -@kindex target hms@r{, and serial protocol} -Now that serial communications are set up, and the development board is -connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with -the name of your program as the argument. @code{@value{GDBN}} prompts -you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special -commands to begin your debugging session: @samp{target hms} to specify -cross-debugging to the Hitachi board, and the @code{load} command to -download your program to the board. @code{load} displays the names of -the program's sections, and a @samp{*} for each 2K of data downloaded. -(If you want to refresh @value{GDBN} data on symbols or on the -executable file without downloading, use the @value{GDBN} commands -@code{file} or @code{symbol-file}. These commands, and @code{load} -itself, are described in @ref{Files,,Commands to specify files}.) - -@smallexample -(eg-C:\H8300\TEST) @value{GDBP} t.x -@value{GDBN} is free software and you are welcome to distribute copies - of it under certain conditions; type "show copying" to see - the conditions. -There is absolutely no warranty for @value{GDBN}; type "show warranty" -for details. -@value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc... -(@value{GDBP}) target hms -Connected to remote H8/300 HMS system. -(@value{GDBP}) load t.x -.text : 0x8000 .. 0xabde *********** -.data : 0xabde .. 0xad30 * -.stack : 0xf000 .. 0xf014 * -@end smallexample - -At this point, you're ready to run or debug your program. From here on, -you can use all the usual @value{GDBN} commands. The @code{break} command -sets breakpoints; the @code{run} command starts your program; -@code{print} or @code{x} display data; the @code{continue} command -resumes execution after stopping at a breakpoint. You can use the -@code{help} command at any time to find out more about @value{GDBN} commands. - -Remember, however, that @emph{operating system} facilities aren't -available on your development board; for example, if your program hangs, -you can't send an interrupt---but you can press the @sc{reset} switch! - -Use the @sc{reset} button on the development board -@itemize @bullet -@item -to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has -no way to pass an interrupt signal to the development board); and - -@item -to return to the @value{GDBN} command prompt after your program finishes -normally. The communications protocol provides no other way for @value{GDBN} -to detect program completion. -@end itemize - -In either case, @value{GDBN} sees the effect of a @sc{reset} on the -development board as a ``normal exit'' of your program. - -@node Hitachi ICE -@subsubsection Using the E7000 in-circuit emulator - -@kindex target e7000@r{, with Hitachi ICE} -You can use the E7000 in-circuit emulator to develop code for either the -Hitachi SH or the H8/300H. Use one of these forms of the @samp{target -e7000} command to connect @value{GDBN} to your E7000: - -@table @code -@item target e7000 @var{port} @var{speed} -Use this form if your E7000 is connected to a serial port. The -@var{port} argument identifies what serial port to use (for example, -@samp{com2}). The third argument is the line speed in bits per second -(for example, @samp{9600}). - -@item target e7000 @var{hostname} -If your E7000 is installed as a host on a TCP/IP network, you can just -specify its hostname; @value{GDBN} uses @code{telnet} to connect. -@end table - -@node Hitachi Special -@subsubsection Special @value{GDBN} commands for Hitachi micros - -Some @value{GDBN} commands are available only for the H8/300: - -@table @code - -@kindex set machine -@kindex show machine -@item set machine h8300 -@itemx set machine h8300h -Condition @value{GDBN} for one of the two variants of the H8/300 -architecture with @samp{set machine}. You can use @samp{show machine} -to check which variant is currently in effect. - -@end table - -@node H8/500 -@subsection H8/500 - -@table @code - -@kindex set memory @var{mod} -@cindex memory models, H8/500 -@item set memory @var{mod} -@itemx show memory -Specify which H8/500 memory model (@var{mod}) you are using with -@samp{set memory}; check which memory model is in effect with @samp{show -memory}. The accepted values for @var{mod} are @code{small}, -@code{big}, @code{medium}, and @code{compact}. - -@end table - -@node i960 -@subsection Intel i960 - -@table @code - -@kindex target mon960 -@item target mon960 @var{dev} -MON960 monitor for Intel i960. - -@kindex target nindy -@item target nindy @var{devicename} -An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is -the name of the serial device to use for the connection, e.g. -@file{/dev/ttya}. - -@end table - -@cindex Nindy -@cindex i960 -@dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When -@value{GDBN} is configured to control a remote Intel 960 using Nindy, you can -tell @value{GDBN} how to connect to the 960 in several ways: - -@itemize @bullet -@item -Through command line options specifying serial port, version of the -Nindy protocol, and communications speed; - -@item -By responding to a prompt on startup; - -@item -By using the @code{target} command at any point during your @value{GDBN} -session. @xref{Target Commands, ,Commands for managing targets}. - -@end itemize - -@cindex download to Nindy-960 -With the Nindy interface to an Intel 960 board, @code{load} -downloads @var{filename} to the 960 as well as adding its symbols in -@value{GDBN}. - -@menu -* Nindy Startup:: Startup with Nindy -* Nindy Options:: Options for Nindy -* Nindy Reset:: Nindy reset command -@end menu - -@node Nindy Startup -@subsubsection Startup with Nindy - -If you simply start @code{@value{GDBP}} without using any command-line -options, you are prompted for what serial port to use, @emph{before} you -reach the ordinary @value{GDBN} prompt: - -@example -Attach /dev/ttyNN -- specify NN, or "quit" to quit: -@end example - -@noindent -Respond to the prompt with whatever suffix (after @samp{/dev/tty}) -identifies the serial port you want to use. You can, if you choose, -simply start up with no Nindy connection by responding to the prompt -with an empty line. If you do this and later wish to attach to Nindy, -use @code{target} (@pxref{Target Commands, ,Commands for managing targets}). - -@node Nindy Options -@subsubsection Options for Nindy - -These are the startup options for beginning your @value{GDBN} session with a -Nindy-960 board attached: - -@table @code -@item -r @var{port} -Specify the serial port name of a serial interface to be used to connect -to the target system. This option is only available when @value{GDBN} is -configured for the Intel 960 target architecture. You may specify -@var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a -device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique -suffix for a specific @code{tty} (e.g. @samp{-r a}). - -@item -O -(An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use -the ``old'' Nindy monitor protocol to connect to the target system. -This option is only available when @value{GDBN} is configured for the Intel 960 -target architecture. - -@quotation -@emph{Warning:} if you specify @samp{-O}, but are actually trying to -connect to a target system that expects the newer protocol, the connection -fails, appearing to be a speed mismatch. @value{GDBN} repeatedly -attempts to reconnect at several different line speeds. You can abort -this process with an interrupt. -@end quotation - -@item -brk -Specify that @value{GDBN} should first send a @code{BREAK} signal to the target -system, in an attempt to reset it, before connecting to a Nindy target. - -@quotation -@emph{Warning:} Many target systems do not have the hardware that this -requires; it only works with a few boards. -@end quotation -@end table - -The standard @samp{-b} option controls the line speed used on the serial -port. - -@c @group -@node Nindy Reset -@subsubsection Nindy reset command - -@table @code -@item reset -@kindex reset -For a Nindy target, this command sends a ``break'' to the remote target -system; this is only useful if the target has been equipped with a -circuit to perform a hard reset (or some other interesting action) when -a break is detected. -@end table -@c @end group - -@node M32R/D -@subsection Mitsubishi M32R/D - -@table @code - -@kindex target m32r -@item target m32r @var{dev} -Mitsubishi M32R/D ROM monitor. - -@end table - -@node M68K -@subsection M68k - -The Motorola m68k configuration includes ColdFire support, and -target command for the following ROM monitors. - -@table @code - -@kindex target abug -@item target abug @var{dev} -ABug ROM monitor for M68K. - -@kindex target cpu32bug -@item target cpu32bug @var{dev} -CPU32BUG monitor, running on a CPU32 (M68K) board. - -@kindex target dbug -@item target dbug @var{dev} -dBUG ROM monitor for Motorola ColdFire. - -@kindex target est -@item target est @var{dev} -EST-300 ICE monitor, running on a CPU32 (M68K) board. - -@kindex target rom68k -@item target rom68k @var{dev} -ROM 68K monitor, running on an M68K IDP board. - -@end table - -If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will -instead have only a single special target command: - -@table @code - -@kindex target es1800 -@item target es1800 @var{dev} -ES-1800 emulator for M68K. - -@end table - -[context?] - -@table @code - -@kindex target rombug -@item target rombug @var{dev} -ROMBUG ROM monitor for OS/9000. - -@end table - -@node M88K -@subsection M88K - -@table @code - -@kindex target bug -@item target bug @var{dev} -BUG monitor, running on a MVME187 (m88k) board. - -@end table - -@node MIPS Embedded -@subsection MIPS Embedded - -@cindex MIPS boards -@value{GDBN} can use the MIPS remote debugging protocol to talk to a -MIPS board attached to a serial line. This is available when -you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}. - -@need 1000 -Use these @value{GDBN} commands to specify the connection to your target board: - -@table @code -@item target mips @var{port} -@kindex target mips @var{port} -To run a program on the board, start up @code{@value{GDBP}} with the -name of your program as the argument. To connect to the board, use the -command @samp{target mips @var{port}}, where @var{port} is the name of -the serial port connected to the board. If the program has not already -been downloaded to the board, you may use the @code{load} command to -download it. You can then use all the usual @value{GDBN} commands. - -For example, this sequence connects to the target board through a serial -port, and loads and runs a program called @var{prog} through the -debugger: - -@example -host$ @value{GDBP} @var{prog} -@value{GDBN} is free software and @dots{} -(@value{GDBP}) target mips /dev/ttyb -(@value{GDBP}) load @var{prog} -(@value{GDBP}) run -@end example - -@item target mips @var{hostname}:@var{portnumber} -On some @value{GDBN} host configurations, you can specify a TCP -connection (for instance, to a serial line managed by a terminal -concentrator) instead of a serial port, using the syntax -@samp{@var{hostname}:@var{portnumber}}. - -@item target pmon @var{port} -@kindex target pmon @var{port} -PMON ROM monitor. - -@item target ddb @var{port} -@kindex target ddb @var{port} -NEC's DDB variant of PMON for Vr4300. - -@item target lsi @var{port} -@kindex target lsi @var{port} -LSI variant of PMON. - -@kindex target r3900 -@item target r3900 @var{dev} -Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips. - -@kindex target array -@item target array @var{dev} -Array Tech LSI33K RAID controller board. - -@end table - - -@noindent -@value{GDBN} also supports these special commands for MIPS targets: - -@table @code -@item set processor @var{args} -@itemx show processor -@kindex set processor @var{args} -@kindex show processor -Use the @code{set processor} command to set the type of MIPS -processor when you want to access processor-type-specific registers. -For example, @code{set processor @var{r3041}} tells @value{GDBN} -to use the CPU registers appropriate for the 3041 chip. -Use the @code{show processor} command to see what MIPS processor @value{GDBN} -is using. Use the @code{info reg} command to see what registers -@value{GDBN} is using. - -@item set mipsfpu double -@itemx set mipsfpu single -@itemx set mipsfpu none -@itemx show mipsfpu -@kindex set mipsfpu -@kindex show mipsfpu -@cindex MIPS remote floating point -@cindex floating point, MIPS remote -If your target board does not support the MIPS floating point -coprocessor, you should use the command @samp{set mipsfpu none} (if you -need this, you may wish to put the command in your @value{GDBN} init -file). This tells @value{GDBN} how to find the return value of -functions which return floating point values. It also allows -@value{GDBN} to avoid saving the floating point registers when calling -functions on the board. If you are using a floating point coprocessor -with only single precision floating point support, as on the @sc{r4650} -processor, use the command @samp{set mipsfpu single}. The default -double precision floating point coprocessor may be selected using -@samp{set mipsfpu double}. - -In previous versions the only choices were double precision or no -floating point, so @samp{set mipsfpu on} will select double precision -and @samp{set mipsfpu off} will select no floating point. - -As usual, you can inquire about the @code{mipsfpu} variable with -@samp{show mipsfpu}. - -@item set remotedebug @var{n} -@itemx show remotedebug -@kindex set remotedebug@r{, MIPS protocol} -@kindex show remotedebug@r{, MIPS protocol} -@cindex @code{remotedebug}, MIPS protocol -@cindex MIPS @code{remotedebug} protocol -@c FIXME! For this to be useful, you must know something about the MIPS -@c FIXME...protocol. Where is it described? -You can see some debugging information about communications with the board -by setting the @code{remotedebug} variable. If you set it to @code{1} using -@samp{set remotedebug 1}, every packet is displayed. If you set it -to @code{2}, every character is displayed. You can check the current value -at any time with the command @samp{show remotedebug}. - -@item set timeout @var{seconds} -@itemx set retransmit-timeout @var{seconds} -@itemx show timeout -@itemx show retransmit-timeout -@cindex @code{timeout}, MIPS protocol -@cindex @code{retransmit-timeout}, MIPS protocol -@kindex set timeout -@kindex show timeout -@kindex set retransmit-timeout -@kindex show retransmit-timeout -You can control the timeout used while waiting for a packet, in the MIPS -remote protocol, with the @code{set timeout @var{seconds}} command. The -default is 5 seconds. Similarly, you can control the timeout used while -waiting for an acknowledgement of a packet with the @code{set -retransmit-timeout @var{seconds}} command. The default is 3 seconds. -You can inspect both values with @code{show timeout} and @code{show -retransmit-timeout}. (These commands are @emph{only} available when -@value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.) - -The timeout set by @code{set timeout} does not apply when @value{GDBN} -is waiting for your program to stop. In that case, @value{GDBN} waits -forever because it has no way of knowing how long the program is going -to run before stopping. -@end table - -@node PowerPC -@subsection PowerPC - -@table @code - -@kindex target dink32 -@item target dink32 @var{dev} -DINK32 ROM monitor. - -@kindex target ppcbug -@item target ppcbug @var{dev} -@kindex target ppcbug1 -@item target ppcbug1 @var{dev} -PPCBUG ROM monitor for PowerPC. - -@kindex target sds -@item target sds @var{dev} -SDS monitor, running on a PowerPC board (such as Motorola's ADS). - -@end table - -@node PA -@subsection HP PA Embedded - -@table @code - -@kindex target op50n -@item target op50n @var{dev} -OP50N monitor, running on an OKI HPPA board. - -@kindex target w89k -@item target w89k @var{dev} -W89K monitor, running on a Winbond HPPA board. - -@end table - -@node SH -@subsection Hitachi SH - -@table @code - -@kindex target hms@r{, with Hitachi SH} -@item target hms @var{dev} -A Hitachi SH board attached via serial line to your host. Use special -commands @code{device} and @code{speed} to control the serial line and -the communications speed used. - -@kindex target e7000@r{, with Hitachi SH} -@item target e7000 @var{dev} -E7000 emulator for Hitachi SH. - -@kindex target sh3@r{, with SH} -@kindex target sh3e@r{, with SH} -@item target sh3 @var{dev} -@item target sh3e @var{dev} -Hitachi SH-3 and SH-3E target systems. - -@end table - -@node Sparclet -@subsection Tsqware Sparclet - -@cindex Sparclet - -@value{GDBN} enables developers to debug tasks running on -Sparclet targets from a Unix host. -@value{GDBN} uses code that runs on -both the Unix host and on the Sparclet target. The program -@code{@value{GDBP}} is installed and executed on the Unix host. - -@table @code -@item remotetimeout @var{args} -@kindex remotetimeout -@value{GDBN} supports the option @code{remotetimeout}. -This option is set by the user, and @var{args} represents the number of -seconds @value{GDBN} waits for responses. -@end table - -@cindex compiling, on Sparclet -When compiling for debugging, include the options @samp{-g} to get debug -information and @samp{-Ttext} to relocate the program to where you wish to -load it on the target. You may also want to add the options @samp{-n} or -@samp{-N} in order to reduce the size of the sections. Example: - -@example -sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N -@end example - -You can use @code{objdump} to verify that the addresses are what you intended: - -@example -sparclet-aout-objdump --headers --syms prog -@end example - -@cindex running, on Sparclet -Once you have set -your Unix execution search path to find @value{GDBN}, you are ready to -run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} -(or @code{sparclet-aout-gdb}, depending on your installation). - -@value{GDBN} comes up showing the prompt: - -@example -(gdbslet) -@end example - -@menu -* Sparclet File:: Setting the file to debug -* Sparclet Connection:: Connecting to Sparclet -* Sparclet Download:: Sparclet download -* Sparclet Execution:: Running and debugging -@end menu - -@node Sparclet File -@subsubsection Setting file to debug - -The @value{GDBN} command @code{file} lets you choose with program to debug. - -@example -(gdbslet) file prog -@end example - -@need 1000 -@value{GDBN} then attempts to read the symbol table of @file{prog}. -@value{GDBN} locates -the file by searching the directories listed in the command search -path. -If the file was compiled with debug information (option "-g"), source -files will be searched as well. -@value{GDBN} locates -the source files by searching the directories listed in the directory search -path (@pxref{Environment, ,Your program's environment}). -If it fails -to find a file, it displays a message such as: - -@example -prog: No such file or directory. -@end example - -When this happens, add the appropriate directories to the search paths with -the @value{GDBN} commands @code{path} and @code{dir}, and execute the -@code{target} command again. - -@node Sparclet Connection -@subsubsection Connecting to Sparclet - -The @value{GDBN} command @code{target} lets you connect to a Sparclet target. -To connect to a target on serial port ``@code{ttya}'', type: - -@example -(gdbslet) target sparclet /dev/ttya -Remote target sparclet connected to /dev/ttya -main () at ../prog.c:3 -@end example - -@need 750 -@value{GDBN} displays messages like these: - -@example -Connected to ttya. -@end example - -@node Sparclet Download -@subsubsection Sparclet download - -@cindex download to Sparclet -Once connected to the Sparclet target, -you can use the @value{GDBN} -@code{load} command to download the file from the host to the target. -The file name and load offset should be given as arguments to the @code{load} -command. -Since the file format is aout, the program must be loaded to the starting -address. You can use @code{objdump} to find out what this value is. The load -offset is an offset which is added to the VMA (virtual memory address) -of each of the file's sections. -For instance, if the program -@file{prog} was linked to text address 0x1201000, with data at 0x12010160 -and bss at 0x12010170, in @value{GDBN}, type: - -@example -(gdbslet) load prog 0x12010000 -Loading section .text, size 0xdb0 vma 0x12010000 -@end example - -If the code is loaded at a different address then what the program was linked -to, you may need to use the @code{section} and @code{add-symbol-file} commands -to tell @value{GDBN} where to map the symbol table. - -@node Sparclet Execution -@subsubsection Running and debugging - -@cindex running and debugging Sparclet programs -You can now begin debugging the task using @value{GDBN}'s execution control -commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN} -manual for the list of commands. - -@example -(gdbslet) b main -Breakpoint 1 at 0x12010000: file prog.c, line 3. -(gdbslet) run -Starting program: prog -Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3 -3 char *symarg = 0; -(gdbslet) step -4 char *execarg = "hello!"; -(gdbslet) -@end example - -@node Sparclite -@subsection Fujitsu Sparclite - -@table @code - -@kindex target sparclite -@item target sparclite @var{dev} -Fujitsu sparclite boards, used only for the purpose of loading. -You must use an additional command to debug the program. -For example: target remote @var{dev} using @value{GDBN} standard -remote protocol. - -@end table - -@node ST2000 -@subsection Tandem ST2000 - -@value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's -STDBUG protocol. - -To connect your ST2000 to the host system, see the manufacturer's -manual. Once the ST2000 is physically attached, you can run: - -@example -target st2000 @var{dev} @var{speed} -@end example - -@noindent -to establish it as your debugging environment. @var{dev} is normally -the name of a serial device, such as @file{/dev/ttya}, connected to the -ST2000 via a serial line. You can instead specify @var{dev} as a TCP -connection (for example, to a serial line attached via a terminal -concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}. - -The @code{load} and @code{attach} commands are @emph{not} defined for -this target; you must load your program into the ST2000 as you normally -would for standalone operation. @value{GDBN} reads debugging information -(such as symbols) from a separate, debugging version of the program -available on your host computer. -@c FIXME!! This is terribly vague; what little content is here is -@c basically hearsay. - -@cindex ST2000 auxiliary commands -These auxiliary @value{GDBN} commands are available to help you with the ST2000 -environment: - -@table @code -@item st2000 @var{command} -@kindex st2000 @var{cmd} -@cindex STDBUG commands (ST2000) -@cindex commands to STDBUG (ST2000) -Send a @var{command} to the STDBUG monitor. See the manufacturer's -manual for available commands. - -@item connect -@cindex connect (to STDBUG) -Connect the controlling terminal to the STDBUG command monitor. When -you are done interacting with STDBUG, typing either of two character -sequences gets you back to the @value{GDBN} command prompt: -@kbd{@key{RET}~.} (Return, followed by tilde and period) or -@kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D). -@end table - -@node Z8000 -@subsection Zilog Z8000 - -@cindex Z8000 -@cindex simulator, Z8000 -@cindex Zilog Z8000 simulator - -When configured for debugging Zilog Z8000 targets, @value{GDBN} includes -a Z8000 simulator. - -For the Z8000 family, @samp{target sim} simulates either the Z8002 (the -unsegmented variant of the Z8000 architecture) or the Z8001 (the -segmented variant). The simulator recognizes which architecture is -appropriate by inspecting the object code. - -@table @code -@item target sim @var{args} -@kindex sim -@kindex target sim@r{, with Z8000} -Debug programs on a simulated CPU. If the simulator supports setup -options, specify them via @var{args}. -@end table - -@noindent -After specifying this target, you can debug programs for the simulated -CPU in the same style as programs for your host computer; use the -@code{file} command to load a new program image, the @code{run} command -to run your program, and so on. - -As well as making available all the usual machine registers -(@pxref{Registers, ,Registers}), the Z8000 simulator provides three -additional items of information as specially named registers: - -@table @code - -@item cycles -Counts clock-ticks in the simulator. - -@item insts -Counts instructions run in the simulator. - -@item time -Execution time in 60ths of a second. - -@end table - -You can refer to these values in @value{GDBN} expressions with the usual -conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a -conditional breakpoint that suspends only after at least 5000 -simulated clock ticks. - -@node Architectures -@section Architectures - -This section describes characteristics of architectures that affect -all uses of @value{GDBN} with the architecture, both native and cross. - -@menu -* A29K:: -* Alpha:: -* MIPS:: -@end menu - -@node A29K -@subsection A29K - -@table @code - -@kindex set rstack_high_address -@cindex AMD 29K register stack -@cindex register stack, AMD29K -@item set rstack_high_address @var{address} -On AMD 29000 family processors, registers are saved in a separate -@dfn{register stack}. There is no way for @value{GDBN} to determine the -extent of this stack. Normally, @value{GDBN} just assumes that the -stack is ``large enough''. This may result in @value{GDBN} referencing -memory locations that do not exist. If necessary, you can get around -this problem by specifying the ending address of the register stack with -the @code{set rstack_high_address} command. The argument should be an -address, which you probably want to precede with @samp{0x} to specify in -hexadecimal. - -@kindex show rstack_high_address -@item show rstack_high_address -Display the current limit of the register stack, on AMD 29000 family -processors. - -@end table - -@node Alpha -@subsection Alpha - -See the following section. - -@node MIPS -@subsection MIPS - -@cindex stack on Alpha -@cindex stack on MIPS -@cindex Alpha stack -@cindex MIPS stack -Alpha- and MIPS-based computers use an unusual stack frame, which -sometimes requires @value{GDBN} to search backward in the object code to -find the beginning of a function. - -@cindex response time, MIPS debugging -To improve response time (especially for embedded applications, where -@value{GDBN} may be restricted to a slow serial line for this search) -you may want to limit the size of this search, using one of these -commands: - -@table @code -@cindex @code{heuristic-fence-post} (Alpha, MIPS) -@item set heuristic-fence-post @var{limit} -Restrict @value{GDBN} to examining at most @var{limit} bytes in its -search for the beginning of a function. A value of @var{0} (the -default) means there is no limit. However, except for @var{0}, the -larger the limit the more bytes @code{heuristic-fence-post} must search -and therefore the longer it takes to run. - -@item show heuristic-fence-post -Display the current limit. -@end table - -@noindent -These commands are available @emph{only} when @value{GDBN} is configured -for debugging programs on Alpha or MIPS processors. - - -@node Controlling GDB -@chapter Controlling @value{GDBN} - -You can alter the way @value{GDBN} interacts with you by using the -@code{set} command. For commands controlling how @value{GDBN} displays -data, see @ref{Print Settings, ,Print settings}. Other settings are -described here. - -@menu -* Prompt:: Prompt -* Editing:: Command editing -* History:: Command history -* Screen Size:: Screen size -* Numbers:: Numbers -* Messages/Warnings:: Optional warnings and messages -* Debugging Output:: Optional messages about internal happenings -@end menu - -@node Prompt -@section Prompt - -@cindex prompt - -@value{GDBN} indicates its readiness to read a command by printing a string -called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You -can change the prompt string with the @code{set prompt} command. For -instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change -the prompt in one of the @value{GDBN} sessions so that you can always tell -which one you are talking to. - -@emph{Note:} @code{set prompt} does not add a space for you after the -prompt you set. This allows you to set a prompt which ends in a space -or a prompt that does not. - -@table @code -@kindex set prompt -@item set prompt @var{newprompt} -Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth. - -@kindex show prompt -@item show prompt -Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}} -@end table - -@node Editing -@section Command editing -@cindex readline -@cindex command line editing - -@value{GDBN} reads its input commands via the @dfn{readline} interface. This -@sc{gnu} library provides consistent behavior for programs which provide a -command line interface to the user. Advantages are @sc{gnu} Emacs-style -or @dfn{vi}-style inline editing of commands, @code{csh}-like history -substitution, and a storage and recall of command history across -debugging sessions. - -You may control the behavior of command line editing in @value{GDBN} with the -command @code{set}. - -@table @code -@kindex set editing -@cindex editing -@item set editing -@itemx set editing on -Enable command line editing (enabled by default). - -@item set editing off -Disable command line editing. - -@kindex show editing -@item show editing -Show whether command line editing is enabled. -@end table - -@node History -@section Command history - -@value{GDBN} can keep track of the commands you type during your -debugging sessions, so that you can be certain of precisely what -happened. Use these commands to manage the @value{GDBN} command -history facility. - -@table @code -@cindex history substitution -@cindex history file -@kindex set history filename -@kindex GDBHISTFILE -@item set history filename @var{fname} -Set the name of the @value{GDBN} command history file to @var{fname}. -This is the file where @value{GDBN} reads an initial command history -list, and where it writes the command history from this session when it -exits. You can access this list through history expansion or through -the history command editing characters listed below. This file defaults -to the value of the environment variable @code{GDBHISTFILE}, or to -@file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable -is not set. - -@cindex history save -@kindex set history save -@item set history save -@itemx set history save on -Record command history in a file, whose name may be specified with the -@code{set history filename} command. By default, this option is disabled. - -@item set history save off -Stop recording command history in a file. - -@cindex history size -@kindex set history size -@item set history size @var{size} -Set the number of commands which @value{GDBN} keeps in its history list. -This defaults to the value of the environment variable -@code{HISTSIZE}, or to 256 if this variable is not set. -@end table - -@cindex history expansion -History expansion assigns special meaning to the character @kbd{!}. -@ifset have-readline-appendices -@xref{Event Designators}. -@end ifset - -Since @kbd{!} is also the logical not operator in C, history expansion -is off by default. If you decide to enable history expansion with the -@code{set history expansion on} command, you may sometimes need to -follow @kbd{!} (when it is used as logical not, in an expression) with -a space or a tab to prevent it from being expanded. The readline -history facilities do not attempt substitution on the strings -@kbd{!=} and @kbd{!(}, even when history expansion is enabled. - -The commands to control history expansion are: - -@table @code -@kindex set history expansion -@item set history expansion on -@itemx set history expansion -Enable history expansion. History expansion is off by default. - -@item set history expansion off -Disable history expansion. - -The readline code comes with more complete documentation of -editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs -or @code{vi} may wish to read it. -@ifset have-readline-appendices -@xref{Command Line Editing}. -@end ifset - -@c @group -@kindex show history -@item show history -@itemx show history filename -@itemx show history save -@itemx show history size -@itemx show history expansion -These commands display the state of the @value{GDBN} history parameters. -@code{show history} by itself displays all four states. -@c @end group -@end table - -@table @code -@kindex shows -@item show commands -Display the last ten commands in the command history. - -@item show commands @var{n} -Print ten commands centered on command number @var{n}. - -@item show commands + -Print ten commands just after the commands last printed. -@end table - -@node Screen Size -@section Screen size -@cindex size of screen -@cindex pauses in output - -Certain commands to @value{GDBN} may produce large amounts of -information output to the screen. To help you read all of it, -@value{GDBN} pauses and asks you for input at the end of each page of -output. Type @key{RET} when you want to continue the output, or @kbd{q} -to discard the remaining output. Also, the screen width setting -determines when to wrap lines of output. Depending on what is being -printed, @value{GDBN} tries to break the line at a readable place, -rather than simply letting it overflow onto the following line. - -Normally @value{GDBN} knows the size of the screen from the terminal -driver software. For example, on Unix @value{GDBN} uses the termcap data base -together with the value of the @code{TERM} environment variable and the -@code{stty rows} and @code{stty cols} settings. If this is not correct, -you can override it with the @code{set height} and @code{set -width} commands: - -@table @code -@kindex set height -@kindex set width -@kindex show width -@kindex show height -@item set height @var{lpp} -@itemx show height -@itemx set width @var{cpl} -@itemx show width -These @code{set} commands specify a screen height of @var{lpp} lines and -a screen width of @var{cpl} characters. The associated @code{show} -commands display the current settings. - -If you specify a height of zero lines, @value{GDBN} does not pause during -output no matter how long the output is. This is useful if output is to a -file or to an editor buffer. - -Likewise, you can specify @samp{set width 0} to prevent @value{GDBN} -from wrapping its output. -@end table - -@node Numbers -@section Numbers -@cindex number representation -@cindex entering numbers - -You can always enter numbers in octal, decimal, or hexadecimal in -@value{GDBN} by the usual conventions: octal numbers begin with -@samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers -begin with @samp{0x}. Numbers that begin with none of these are, by -default, entered in base 10; likewise, the default display for -numbers---when no particular format is specified---is base 10. You can -change the default base for both input and output with the @code{set -radix} command. - -@table @code -@kindex set input-radix -@item set input-radix @var{base} -Set the default base for numeric input. Supported choices -for @var{base} are decimal 8, 10, or 16. @var{base} must itself be -specified either unambiguously or using the current default radix; for -example, any of - -@smallexample -set radix 012 -set radix 10. -set radix 0xa -@end smallexample - -@noindent -sets the base to decimal. On the other hand, @samp{set radix 10} -leaves the radix unchanged no matter what it was. - -@kindex set output-radix -@item set output-radix @var{base} -Set the default base for numeric display. Supported choices -for @var{base} are decimal 8, 10, or 16. @var{base} must itself be -specified either unambiguously or using the current default radix. - -@kindex show input-radix -@item show input-radix -Display the current default base for numeric input. - -@kindex show output-radix -@item show output-radix -Display the current default base for numeric display. -@end table - -@node Messages/Warnings -@section Optional warnings and messages - -By default, @value{GDBN} is silent about its inner workings. If you are -running on a slow machine, you may want to use the @code{set verbose} -command. This makes @value{GDBN} tell you when it does a lengthy -internal operation, so you will not think it has crashed. - -Currently, the messages controlled by @code{set verbose} are those -which announce that the symbol table for a source file is being read; -see @code{symbol-file} in @ref{Files, ,Commands to specify files}. - -@table @code -@kindex set verbose -@item set verbose on -Enables @value{GDBN} output of certain informational messages. - -@item set verbose off -Disables @value{GDBN} output of certain informational messages. - -@kindex show verbose -@item show verbose -Displays whether @code{set verbose} is on or off. -@end table - -By default, if @value{GDBN} encounters bugs in the symbol table of an -object file, it is silent; but if you are debugging a compiler, you may -find this information useful (@pxref{Symbol Errors, ,Errors reading -symbol files}). - -@table @code - -@kindex set complaints -@item set complaints @var{limit} -Permits @value{GDBN} to output @var{limit} complaints about each type of -unusual symbols before becoming silent about the problem. Set -@var{limit} to zero to suppress all complaints; set it to a large number -to prevent complaints from being suppressed. - -@kindex show complaints -@item show complaints -Displays how many symbol complaints @value{GDBN} is permitted to produce. - -@end table - -By default, @value{GDBN} is cautious, and asks what sometimes seems to be a -lot of stupid questions to confirm certain commands. For example, if -you try to run a program which is already running: - -@example -(@value{GDBP}) run -The program being debugged has been started already. -Start it from the beginning? (y or n) -@end example - -If you are willing to unflinchingly face the consequences of your own -commands, you can disable this ``feature'': - -@table @code - -@kindex set confirm -@cindex flinching -@cindex confirmation -@cindex stupid questions -@item set confirm off -Disables confirmation requests. - -@item set confirm on -Enables confirmation requests (the default). - -@kindex show confirm -@item show confirm -Displays state of confirmation requests. - -@end table - -@node Debugging Output -@section Optional messages about internal happenings -@table @code -@kindex set debug arch -@item set debug arch -Turns on or off display of gdbarch debugging info. The default is off -@kindex show debug arch -@item show debug arch -Displays the current state of displaying gdbarch debugging info. -@kindex set debug event -@item set debug event -Turns on or off display of @value{GDBN} event debugging info. The -default is off. -@kindex show debug event -@item show debug event -Displays the current state of displaying @value{GDBN} event debugging -info. -@kindex set debug expression -@item set debug expression -Turns on or off display of @value{GDBN} expression debugging info. The -default is off. -@kindex show debug expression -@item show debug expression -Displays the current state of displaying @value{GDBN} expression -debugging info. -@kindex set debug overload -@item set debug overload -Turns on or off display of @value{GDBN} C@t{++} overload debugging -info. This includes info such as ranking of functions, etc. The default -is off. -@kindex show debug overload -@item show debug overload -Displays the current state of displaying @value{GDBN} C@t{++} overload -debugging info. -@kindex set debug remote -@cindex packets, reporting on stdout -@cindex serial connections, debugging -@item set debug remote -Turns on or off display of reports on all packets sent back and forth across -the serial line to the remote machine. The info is printed on the -@value{GDBN} standard output stream. The default is off. -@kindex show debug remote -@item show debug remote -Displays the state of display of remote packets. -@kindex set debug serial -@item set debug serial -Turns on or off display of @value{GDBN} serial debugging info. The -default is off. -@kindex show debug serial -@item show debug serial -Displays the current state of displaying @value{GDBN} serial debugging -info. -@kindex set debug target -@item set debug target -Turns on or off display of @value{GDBN} target debugging info. This info -includes what is going on at the target level of GDB, as it happens. The -default is off. -@kindex show debug target -@item show debug target -Displays the current state of displaying @value{GDBN} target debugging -info. -@kindex set debug varobj -@item set debug varobj -Turns on or off display of @value{GDBN} variable object debugging -info. The default is off. -@kindex show debug varobj -@item show debug varobj -Displays the current state of displaying @value{GDBN} variable object -debugging info. -@end table - -@node Sequences -@chapter Canned Sequences of Commands - -Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint -command lists}), @value{GDBN} provides two ways to store sequences of -commands for execution as a unit: user-defined commands and command -files. - -@menu -* Define:: User-defined commands -* Hooks:: User-defined command hooks -* Command Files:: Command files -* Output:: Commands for controlled output -@end menu - -@node Define -@section User-defined commands - -@cindex user-defined command -A @dfn{user-defined command} is a sequence of @value{GDBN} commands to -which you assign a new name as a command. This is done with the -@code{define} command. User commands may accept up to 10 arguments -separated by whitespace. Arguments are accessed within the user command -via @var{$arg0@dots{}$arg9}. A trivial example: - -@smallexample -define adder - print $arg0 + $arg1 + $arg2 -@end smallexample - -@noindent -To execute the command use: - -@smallexample -adder 1 2 3 -@end smallexample - -@noindent -This defines the command @code{adder}, which prints the sum of -its three arguments. Note the arguments are text substitutions, so they may -reference variables, use complex expressions, or even perform inferior -functions calls. - -@table @code - -@kindex define -@item define @var{commandname} -Define a command named @var{commandname}. If there is already a command -by that name, you are asked to confirm that you want to redefine it. - -The definition of the command is made up of other @value{GDBN} command lines, -which are given following the @code{define} command. The end of these -commands is marked by a line containing @code{end}. - -@kindex if -@kindex else -@item if -Takes a single argument, which is an expression to evaluate. -It is followed by a series of commands that are executed -only if the expression is true (nonzero). -There can then optionally be a line @code{else}, followed -by a series of commands that are only executed if the expression -was false. The end of the list is marked by a line containing @code{end}. - -@kindex while -@item while -The syntax is similar to @code{if}: the command takes a single argument, -which is an expression to evaluate, and must be followed by the commands to -execute, one per line, terminated by an @code{end}. -The commands are executed repeatedly as long as the expression -evaluates to true. - -@kindex document -@item document @var{commandname} -Document the user-defined command @var{commandname}, so that it can be -accessed by @code{help}. The command @var{commandname} must already be -defined. This command reads lines of documentation just as @code{define} -reads the lines of the command definition, ending with @code{end}. -After the @code{document} command is finished, @code{help} on command -@var{commandname} displays the documentation you have written. - -You may use the @code{document} command again to change the -documentation of a command. Redefining the command with @code{define} -does not change the documentation. - -@kindex help user-defined -@item help user-defined -List all user-defined commands, with the first line of the documentation -(if any) for each. - -@kindex show user -@item show user -@itemx show user @var{commandname} -Display the @value{GDBN} commands used to define @var{commandname} (but -not its documentation). If no @var{commandname} is given, display the -definitions for all user-defined commands. - -@end table - -When user-defined commands are executed, the -commands of the definition are not printed. An error in any command -stops execution of the user-defined command. - -If used interactively, commands that would ask for confirmation proceed -without asking when used inside a user-defined command. Many @value{GDBN} -commands that normally print messages to say what they are doing omit the -messages when used in a user-defined command. - -@node Hooks -@section User-defined command hooks -@cindex command hooks -@cindex hooks, for commands -@cindex hooks, pre-command - -@kindex hook -@kindex hook- -You may define @dfn{hooks}, which are a special kind of user-defined -command. Whenever you run the command @samp{foo}, if the user-defined -command @samp{hook-foo} exists, it is executed (with no arguments) -before that command. - -@cindex hooks, post-command -@kindex hookpost -@kindex hookpost- -A hook may also be defined which is run after the command you executed. -Whenever you run the command @samp{foo}, if the user-defined command -@samp{hookpost-foo} exists, it is executed (with no arguments) after -that command. Post-execution hooks may exist simultaneously with -pre-execution hooks, for the same command. - -It is valid for a hook to call the command which it hooks. If this -occurs, the hook is not re-executed, thereby avoiding infinte recursion. - -@c It would be nice if hookpost could be passed a parameter indicating -@c if the command it hooks executed properly or not. FIXME! - -@kindex stop@r{, a pseudo-command} -In addition, a pseudo-command, @samp{stop} exists. Defining -(@samp{hook-stop}) makes the associated commands execute every time -execution stops in your program: before breakpoint commands are run, -displays are printed, or the stack frame is printed. - -For example, to ignore @code{SIGALRM} signals while -single-stepping, but treat them normally during normal execution, -you could define: - -@example -define hook-stop -handle SIGALRM nopass -end - -define hook-run -handle SIGALRM pass -end - -define hook-continue -handle SIGLARM pass -end -@end example - -As a further example, to hook at the begining and end of the @code{echo} -command, and to add extra text to the beginning and end of the message, -you could define: - -@example -define hook-echo -echo <<<--- -end - -define hookpost-echo -echo --->>>\n -end - -(@value{GDBP}) echo Hello World -<<<---Hello World--->>> -(@value{GDBP}) - -@end example - -You can define a hook for any single-word command in @value{GDBN}, but -not for command aliases; you should define a hook for the basic command -name, e.g. @code{backtrace} rather than @code{bt}. -@c FIXME! So how does Joe User discover whether a command is an alias -@c or not? -If an error occurs during the execution of your hook, execution of -@value{GDBN} commands stops and @value{GDBN} issues a prompt -(before the command that you actually typed had a chance to run). - -If you try to define a hook which does not match any known command, you -get a warning from the @code{define} command. - -@node Command Files -@section Command files - -@cindex command files -A command file for @value{GDBN} is a file of lines that are @value{GDBN} -commands. Comments (lines starting with @kbd{#}) may also be included. -An empty line in a command file does nothing; it does not mean to repeat -the last command, as it would from the terminal. - -@cindex init file -@cindex @file{.gdbinit} -@cindex @file{gdb.ini} -When you start @value{GDBN}, it automatically executes commands from its -@dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP -port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the -limitations of file names imposed by DOS filesystems.}. -During startup, @value{GDBN} does the following: - -@enumerate -@item -Reads the init file (if any) in your home directory@footnote{On -DOS/Windows systems, the home directory is the one pointed to by the -@code{HOME} environment variable.}. - -@item -Processes command line options and operands. - -@item -Reads the init file (if any) in the current working directory. - -@item -Reads command files specified by the @samp{-x} option. -@end enumerate - -The init file in your home directory can set options (such as @samp{set -complaints}) that affect subsequent processing of command line options -and operands. Init files are not executed if you use the @samp{-nx} -option (@pxref{Mode Options, ,Choosing modes}). - -@cindex init file name -On some configurations of @value{GDBN}, the init file is known by a -different name (these are typically environments where a specialized -form of @value{GDBN} may need to coexist with other forms, hence a -different name for the specialized version's init file). These are the -environments with special init file names: - -@cindex @file{.vxgdbinit} -@itemize @bullet -@item -VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit} - -@cindex @file{.os68gdbinit} -@item -OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit} - -@cindex @file{.esgdbinit} -@item -ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit} -@end itemize - -You can also request the execution of a command file with the -@code{source} command: - -@table @code -@kindex source -@item source @var{filename} -Execute the command file @var{filename}. -@end table - -The lines in a command file are executed sequentially. They are not -printed as they are executed. An error in any command terminates execution -of the command file. - -Commands that would ask for confirmation if used interactively proceed -without asking when used in a command file. Many @value{GDBN} commands that -normally print messages to say what they are doing omit the messages -when called from command files. - -@value{GDBN} also accepts command input from standard input. In this -mode, normal output goes to standard output and error output goes to -standard error. Errors in a command file supplied on standard input do -not terminate execution of the command file --- execution continues with -the next command. - -@example -gdb < cmds > log 2>&1 -@end example - -(The syntax above will vary depending on the shell used.) This example -will execute commands from the file @file{cmds}. All output and errors -would be directed to @file{log}. - -@node Output -@section Commands for controlled output - -During the execution of a command file or a user-defined command, normal -@value{GDBN} output is suppressed; the only output that appears is what is -explicitly printed by the commands in the definition. This section -describes three commands useful for generating exactly the output you -want. - -@table @code -@kindex echo -@item echo @var{text} -@c I do not consider backslash-space a standard C escape sequence -@c because it is not in ANSI. -Print @var{text}. Nonprinting characters can be included in -@var{text} using C escape sequences, such as @samp{\n} to print a -newline. @strong{No newline is printed unless you specify one.} -In addition to the standard C escape sequences, a backslash followed -by a space stands for a space. This is useful for displaying a -string with spaces at the beginning or the end, since leading and -trailing spaces are otherwise trimmed from all arguments. -To print @samp{@w{ }and foo =@w{ }}, use the command -@samp{echo \@w{ }and foo = \@w{ }}. - -A backslash at the end of @var{text} can be used, as in C, to continue -the command onto subsequent lines. For example, - -@example -echo This is some text\n\ -which is continued\n\ -onto several lines.\n -@end example - -produces the same output as - -@example -echo This is some text\n -echo which is continued\n -echo onto several lines.\n -@end example - -@kindex output -@item output @var{expression} -Print the value of @var{expression} and nothing but that value: no -newlines, no @samp{$@var{nn} = }. The value is not entered in the -value history either. @xref{Expressions, ,Expressions}, for more information -on expressions. - -@item output/@var{fmt} @var{expression} -Print the value of @var{expression} in format @var{fmt}. You can use -the same formats as for @code{print}. @xref{Output Formats,,Output -formats}, for more information. - -@kindex printf -@item printf @var{string}, @var{expressions}@dots{} -Print the values of the @var{expressions} under the control of -@var{string}. The @var{expressions} are separated by commas and may be -either numbers or pointers. Their values are printed as specified by -@var{string}, exactly as if your program were to execute the C -subroutine -@c FIXME: the above implies that at least all ANSI C formats are -@c supported, but it isn't true: %E and %G don't work (or so it seems). -@c Either this is a bug, or the manual should document what formats are -@c supported. - -@example -printf (@var{string}, @var{expressions}@dots{}); -@end example - -For example, you can print two values in hex like this: - -@smallexample -printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo -@end smallexample - -The only backslash-escape sequences that you can use in the format -string are the simple ones that consist of backslash followed by a -letter. -@end table - -@node TUI -@chapter @value{GDBN} Text User Interface -@cindex TUI - -@menu -* TUI Overview:: TUI overview -* TUI Keys:: TUI key bindings -* TUI Commands:: TUI specific commands -* TUI Configuration:: TUI configuration variables -@end menu - -The @value{GDBN} Text User Interface, TUI in short, -is a terminal interface which uses the @code{curses} library -to show the source file, the assembly output, the program registers -and @value{GDBN} commands in separate text windows. -The TUI is available only when @value{GDBN} is configured -with the @code{--enable-tui} configure option (@pxref{Configure Options}). - -@node TUI Overview -@section TUI overview - -The TUI has two display modes that can be switched while -@value{GDBN} runs: - -@itemize @bullet -@item -A curses (or TUI) mode in which it displays several text -windows on the terminal. - -@item -A standard mode which corresponds to the @value{GDBN} configured without -the TUI. -@end itemize - -In the TUI mode, @value{GDBN} can display several text window -on the terminal: - -@table @emph -@item command -This window is the @value{GDBN} command window with the @value{GDBN} -prompt and the @value{GDBN} outputs. The @value{GDBN} input is still -managed using readline but through the TUI. The @emph{command} -window is always visible. - -@item source -The source window shows the source file of the program. The current -line as well as active breakpoints are displayed in this window. -The current program position is shown with the @samp{>} marker and -active breakpoints are shown with @samp{*} markers. - -@item assembly -The assembly window shows the disassembly output of the program. - -@item register -This window shows the processor registers. It detects when -a register is changed and when this is the case, registers that have -changed are highlighted. - -@end table - -The source, assembly and register windows are attached to the thread -and the frame position. They are updated when the current thread -changes, when the frame changes or when the program counter changes. -These three windows are arranged by the TUI according to several -layouts. The layout defines which of these three windows are visible. -The following layouts are available: - -@itemize @bullet -@item -source - -@item -assembly - -@item -source and assembly - -@item -source and registers - -@item -assembly and registers - -@end itemize - -@node TUI Keys -@section TUI Key Bindings -@cindex TUI key bindings - -The TUI installs several key bindings in the readline keymaps -(@pxref{Command Line Editing}). -They allow to leave or enter in the TUI mode or they operate -directly on the TUI layout and windows. The following key bindings -are installed for both TUI mode and the @value{GDBN} standard mode. - -@table @kbd -@kindex C-x C-a -@item C-x C-a -@kindex C-x a -@itemx C-x a -@kindex C-x A -@itemx C-x A -Enter or leave the TUI mode. When the TUI mode is left, -the curses window management is left and @value{GDBN} operates using -its standard mode writing on the terminal directly. When the TUI -mode is entered, the control is given back to the curses windows. -The screen is then refreshed. - -@kindex C-x 1 -@item C-x 1 -Use a TUI layout with only one window. The layout will -either be @samp{source} or @samp{assembly}. When the TUI mode -is not active, it will switch to the TUI mode. - -Think of this key binding as the Emacs @kbd{C-x 1} binding. - -@kindex C-x 2 -@item C-x 2 -Use a TUI layout with at least two windows. When the current -layout shows already two windows, a next layout with two windows is used. -When a new layout is chosen, one window will always be common to the -previous layout and the new one. - -Think of it as the Emacs @kbd{C-x 2} binding. - -@end table - -The following key bindings are handled only by the TUI mode: - -@table @key -@kindex PgUp -@item PgUp -Scroll the active window one page up. - -@kindex PgDn -@item PgDn -Scroll the active window one page down. - -@kindex Up -@item Up -Scroll the active window one line up. - -@kindex Down -@item Down -Scroll the active window one line down. - -@kindex Left -@item Left -Scroll the active window one column left. - -@kindex Right -@item Right -Scroll the active window one column right. - -@kindex C-L -@item C-L -Refresh the screen. - -@end table - -In the TUI mode, the arrow keys are used by the active window -for scrolling. This means they are not available for readline. It is -necessary to use other readline key bindings such as @key{C-p}, @key{C-n}, -@key{C-b} and @key{C-f}. - -@node TUI Commands -@section TUI specific commands -@cindex TUI commands - -The TUI has specific commands to control the text windows. -These commands are always available, that is they do not depend on -the current terminal mode in which @value{GDBN} runs. When @value{GDBN} -is in the standard mode, using these commands will automatically switch -in the TUI mode. - -@table @code -@item layout next -@kindex layout next -Display the next layout. - -@item layout prev -@kindex layout prev -Display the previous layout. - -@item layout src -@kindex layout src -Display the source window only. - -@item layout asm -@kindex layout asm -Display the assembly window only. - -@item layout split -@kindex layout split -Display the source and assembly window. - -@item layout regs -@kindex layout regs -Display the register window together with the source or assembly window. - -@item focus next | prev | src | asm | regs | split -@kindex focus -Set the focus to the named window. -This command allows to change the active window so that scrolling keys -can be affected to another window. - -@item refresh -@kindex refresh -Refresh the screen. This is similar to using @key{C-L} key. - -@item update -@kindex update -Update the source window and the current execution point. - -@item winheight @var{name} +@var{count} -@itemx winheight @var{name} -@var{count} -@kindex winheight -Change the height of the window @var{name} by @var{count} -lines. Positive counts increase the height, while negative counts -decrease it. - -@end table - -@node TUI Configuration -@section TUI configuration variables -@cindex TUI configuration variables - -The TUI has several configuration variables that control the -appearance of windows on the terminal. - -@table @code -@item set tui border-kind @var{kind} -@kindex set tui border-kind -Select the border appearance for the source, assembly and register windows. -The possible values are the following: -@table @code -@item space -Use a space character to draw the border. - -@item ascii -Use ascii characters + - and | to draw the border. - -@item acs -Use the Alternate Character Set to draw the border. The border is -drawn using character line graphics if the terminal supports them. - -@end table - -@item set tui active-border-mode @var{mode} -@kindex set tui active-border-mode -Select the attributes to display the border of the active window. -The possible values are @code{normal}, @code{standout}, @code{reverse}, -@code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}. - -@item set tui border-mode @var{mode} -@kindex set tui border-mode -Select the attributes to display the border of other windows. -The @var{mode} can be one of the following: -@table @code -@item normal -Use normal attributes to display the border. - -@item standout -Use standout mode. - -@item reverse -Use reverse video mode. - -@item half -Use half bright mode. - -@item half-standout -Use half bright and standout mode. - -@item bold -Use extra bright or bold mode. - -@item bold-standout -Use extra bright or bold and standout mode. - -@end table - -@end table - -@node Emacs -@chapter Using @value{GDBN} under @sc{gnu} Emacs - -@cindex Emacs -@cindex @sc{gnu} Emacs -A special interface allows you to use @sc{gnu} Emacs to view (and -edit) the source files for the program you are debugging with -@value{GDBN}. - -To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the -executable file you want to debug as an argument. This command starts -@value{GDBN} as a subprocess of Emacs, with input and output through a newly -created Emacs buffer. -@c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.) - -Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two -things: - -@itemize @bullet -@item -All ``terminal'' input and output goes through the Emacs buffer. -@end itemize - -This applies both to @value{GDBN} commands and their output, and to the input -and output done by the program you are debugging. - -This is useful because it means that you can copy the text of previous -commands and input them again; you can even use parts of the output -in this way. - -All the facilities of Emacs' Shell mode are available for interacting -with your program. In particular, you can send signals the usual -way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a -stop. - -@itemize @bullet -@item -@value{GDBN} displays source code through Emacs. -@end itemize - -Each time @value{GDBN} displays a stack frame, Emacs automatically finds the -source file for that frame and puts an arrow (@samp{=>}) at the -left margin of the current line. Emacs uses a separate buffer for -source display, and splits the screen to show both your @value{GDBN} session -and the source. - -Explicit @value{GDBN} @code{list} or search commands still produce output as -usual, but you probably have no reason to use them from Emacs. - -@quotation -@emph{Warning:} If the directory where your program resides is not your -current directory, it can be easy to confuse Emacs about the location of -the source files, in which case the auxiliary display buffer does not -appear to show your source. @value{GDBN} can find programs by searching your -environment's @code{PATH} variable, so the @value{GDBN} input and output -session proceeds normally; but Emacs does not get enough information -back from @value{GDBN} to locate the source files in this situation. To -avoid this problem, either start @value{GDBN} mode from the directory where -your program resides, or specify an absolute file name when prompted for the -@kbd{M-x gdb} argument. - -A similar confusion can result if you use the @value{GDBN} @code{file} command to -switch to debugging a program in some other location, from an existing -@value{GDBN} buffer in Emacs. -@end quotation - -By default, @kbd{M-x gdb} calls the program called @file{gdb}. If -you need to call @value{GDBN} by a different name (for example, if you keep -several configurations around, with different names) you can set the -Emacs variable @code{gdb-command-name}; for example, - -@example -(setq gdb-command-name "mygdb") -@end example - -@noindent -(preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or -in your @file{.emacs} file) makes Emacs call the program named -``@code{mygdb}'' instead. - -In the @value{GDBN} I/O buffer, you can use these special Emacs commands in -addition to the standard Shell mode commands: - -@table @kbd -@item C-h m -Describe the features of Emacs' @value{GDBN} Mode. - -@item M-s -Execute to another source line, like the @value{GDBN} @code{step} command; also -update the display window to show the current file and location. - -@item M-n -Execute to next source line in this function, skipping all function -calls, like the @value{GDBN} @code{next} command. Then update the display window -to show the current file and location. - -@item M-i -Execute one instruction, like the @value{GDBN} @code{stepi} command; update -display window accordingly. - -@item M-x gdb-nexti -Execute to next instruction, using the @value{GDBN} @code{nexti} command; update -display window accordingly. - -@item C-c C-f -Execute until exit from the selected stack frame, like the @value{GDBN} -@code{finish} command. - -@item M-c -Continue execution of your program, like the @value{GDBN} @code{continue} -command. - -@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}. - -@item M-u -Go up the number of frames indicated by the numeric argument -(@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}), -like the @value{GDBN} @code{up} command. - -@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}. - -@item M-d -Go down the number of frames indicated by the numeric argument, like the -@value{GDBN} @code{down} command. - -@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}. - -@item C-x & -Read the number where the cursor is positioned, and insert it at the end -of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code -around an address that was displayed earlier, type @kbd{disassemble}; -then move the cursor to the address display, and pick up the -argument for @code{disassemble} by typing @kbd{C-x &}. - -You can customize this further by defining elements of the list -@code{gdb-print-command}; once it is defined, you can format or -otherwise process numbers picked up by @kbd{C-x &} before they are -inserted. A numeric argument to @kbd{C-x &} indicates that you -wish special formatting, and also acts as an index to pick an element of the -list. If the list element is a string, the number to be inserted is -formatted using the Emacs function @code{format}; otherwise the number -is passed as an argument to the corresponding list element. -@end table - -In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break}) -tells @value{GDBN} to set a breakpoint on the source line point is on. - -If you accidentally delete the source-display buffer, an easy way to get -it back is to type the command @code{f} in the @value{GDBN} buffer, to -request a frame display; when you run under Emacs, this recreates -the source buffer if necessary to show you the context of the current -frame. - -The source files displayed in Emacs are in ordinary Emacs buffers -which are visiting the source files in the usual way. You can edit -the files with these buffers if you wish; but keep in mind that @value{GDBN} -communicates with Emacs in terms of line numbers. If you add or -delete lines from the text, the line numbers that @value{GDBN} knows cease -to correspond properly with the code. - -@c The following dropped because Epoch is nonstandard. Reactivate -@c if/when v19 does something similar. ---doc@cygnus.com 19dec1990 -@ignore -@kindex Emacs Epoch environment -@kindex Epoch -@kindex inspect - -Version 18 of @sc{gnu} Emacs has a built-in window system -called the @code{epoch} -environment. Users of this environment can use a new command, -@code{inspect} which performs identically to @code{print} except that -each value is printed in its own window. -@end ignore - -@include annotate.texi -@include gdbmi.texinfo - -@node GDB Bugs -@chapter Reporting Bugs in @value{GDBN} -@cindex bugs in @value{GDBN} -@cindex reporting bugs in @value{GDBN} - -Your bug reports play an essential role in making @value{GDBN} reliable. - -Reporting a bug may help you by bringing a solution to your problem, or it -may not. But in any case the principal function of a bug report is to help -the entire community by making the next version of @value{GDBN} work better. Bug -reports are your contribution to the maintenance of @value{GDBN}. - -In order for a bug report to serve its purpose, you must include the -information that enables us to fix the bug. - -@menu -* Bug Criteria:: Have you found a bug? -* Bug Reporting:: How to report bugs -@end menu - -@node Bug Criteria -@section Have you found a bug? -@cindex bug criteria - -If you are not sure whether you have found a bug, here are some guidelines: - -@itemize @bullet -@cindex fatal signal -@cindex debugger crash -@cindex crash of debugger -@item -If the debugger gets a fatal signal, for any input whatever, that is a -@value{GDBN} bug. Reliable debuggers never crash. - -@cindex error on valid input -@item -If @value{GDBN} produces an error message for valid input, that is a -bug. (Note that if you're cross debugging, the problem may also be -somewhere in the connection to the target.) - -@cindex invalid input -@item -If @value{GDBN} does not produce an error message for invalid input, -that is a bug. However, you should note that your idea of -``invalid input'' might be our idea of ``an extension'' or ``support -for traditional practice''. - -@item -If you are an experienced user of debugging tools, your suggestions -for improvement of @value{GDBN} are welcome in any case. -@end itemize - -@node Bug Reporting -@section How to report bugs -@cindex bug reports -@cindex @value{GDBN} bugs, reporting - -A number of companies and individuals offer support for @sc{gnu} products. -If you obtained @value{GDBN} from a support organization, we recommend you -contact that organization first. - -You can find contact information for many support companies and -individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs -distribution. -@c should add a web page ref... - -In any event, we also recommend that you send bug reports for -@value{GDBN} to this addresses: - -@example -bug-gdb@@gnu.org -@end example - -@strong{Do not send bug reports to @samp{info-gdb}, or to -@samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do -not want to receive bug reports. Those that do have arranged to receive -@samp{bug-gdb}. - -The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which -serves as a repeater. The mailing list and the newsgroup carry exactly -the same messages. Often people think of posting bug reports to the -newsgroup instead of mailing them. This appears to work, but it has one -problem which can be crucial: a newsgroup posting often lacks a mail -path back to the sender. Thus, if we need to ask for more information, -we may be unable to reach you. For this reason, it is better to send -bug reports to the mailing list. - -As a last resort, send bug reports on paper to: - -@example -@sc{gnu} Debugger Bugs -Free Software Foundation Inc. -59 Temple Place - Suite 330 -Boston, MA 02111-1307 -USA -@end example - -The fundamental principle of reporting bugs usefully is this: -@strong{report all the facts}. If you are not sure whether to state a -fact or leave it out, state it! - -Often people omit facts because they think they know what causes the -problem and assume that some details do not matter. Thus, you might -assume that the name of the variable you use in an example does not matter. -Well, probably it does not, but one cannot be sure. Perhaps the bug is a -stray memory reference which happens to fetch from the location where that -name is stored in memory; perhaps, if the name were different, the contents -of that location would fool the debugger into doing the right thing despite -the bug. Play it safe and give a specific, complete example. That is the -easiest thing for you to do, and the most helpful. - -Keep in mind that the purpose of a bug report is to enable us to fix the -bug. It may be that the bug has been reported previously, but neither -you nor we can know that unless your bug report is complete and -self-contained. - -Sometimes people give a few sketchy facts and ask, ``Does this ring a -bell?'' Those bug reports are useless, and we urge everyone to -@emph{refuse to respond to them} except to chide the sender to report -bugs properly. - -To enable us to fix the bug, you should include all these things: - -@itemize @bullet -@item -The version of @value{GDBN}. @value{GDBN} announces it if you start -with no arguments; you can also print it at any time using @code{show -version}. - -Without this, we will not know whether there is any point in looking for -the bug in the current version of @value{GDBN}. - -@item -The type of machine you are using, and the operating system name and -version number. - -@item -What compiler (and its version) was used to compile @value{GDBN}---e.g. -``@value{GCC}--2.8.1''. - -@item -What compiler (and its version) was used to compile the program you are -debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP -C Compiler''. For GCC, you can say @code{gcc --version} to get this -information; for other compilers, see the documentation for those -compilers. - -@item -The command arguments you gave the compiler to compile your example and -observe the bug. For example, did you use @samp{-O}? To guarantee -you will not omit something important, list them all. A copy of the -Makefile (or the output from make) is sufficient. - -If we were to try to guess the arguments, we would probably guess wrong -and then we might not encounter the bug. - -@item -A complete input script, and all necessary source files, that will -reproduce the bug. - -@item -A description of what behavior you observe that you believe is -incorrect. For example, ``It gets a fatal signal.'' - -Of course, if the bug is that @value{GDBN} gets a fatal signal, then we -will certainly notice it. But if the bug is incorrect output, we might -not notice unless it is glaringly wrong. You might as well not give us -a chance to make a mistake. - -Even if the problem you experience is a fatal signal, you should still -say so explicitly. Suppose something strange is going on, such as, your -copy of @value{GDBN} is out of synch, or you have encountered a bug in -the C library on your system. (This has happened!) Your copy might -crash and ours would not. If you told us to expect a crash, then when -ours fails to crash, we would know that the bug was not happening for -us. If you had not told us to expect a crash, then we would not be able -to draw any conclusion from our observations. - -@item -If you wish to suggest changes to the @value{GDBN} source, send us context -diffs. If you even discuss something in the @value{GDBN} source, refer to -it by context, not by line number. - -The line numbers in our development sources will not match those in your -sources. Your line numbers would convey no useful information to us. - -@end itemize - -Here are some things that are not necessary: - -@itemize @bullet -@item -A description of the envelope of the bug. - -Often people who encounter a bug spend a lot of time investigating -which changes to the input file will make the bug go away and which -changes will not affect it. - -This is often time consuming and not very useful, because the way we -will find the bug is by running a single example under the debugger -with breakpoints, not by pure deduction from a series of examples. -We recommend that you save your time for something else. - -Of course, if you can find a simpler example to report @emph{instead} -of the original one, that is a convenience for us. Errors in the -output will be easier to spot, running under the debugger will take -less time, and so on. - -However, simplification is not vital; if you do not want to do this, -report the bug anyway and send us the entire test case you used. - -@item -A patch for the bug. - -A patch for the bug does help us if it is a good one. But do not omit -the necessary information, such as the test case, on the assumption that -a patch is all we need. We might see problems with your patch and decide -to fix the problem another way, or we might not understand it at all. - -Sometimes with a program as complicated as @value{GDBN} it is very hard to -construct an example that will make the program follow a certain path -through the code. If you do not send us the example, we will not be able -to construct one, so we will not be able to verify that the bug is fixed. - -And if we cannot understand what bug you are trying to fix, or why your -patch should be an improvement, we will not install it. A test case will -help us to understand. - -@item -A guess about what the bug is or what it depends on. - -Such guesses are usually wrong. Even we cannot guess right about such -things without first using the debugger to find the facts. -@end itemize - -@c The readline documentation is distributed with the readline code -@c and consists of the two following files: -@c rluser.texinfo -@c inc-hist.texinfo -@c Use -I with makeinfo to point to the appropriate directory, -@c environment var TEXINPUTS with TeX. -@include rluser.texinfo -@include inc-hist.texinfo - - -@node Formatting Documentation -@appendix Formatting Documentation - -@cindex @value{GDBN} reference card -@cindex reference card -The @value{GDBN} 4 release includes an already-formatted reference card, ready -for printing with PostScript or Ghostscript, in the @file{gdb} -subdirectory of the main source directory@footnote{In -@file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN} -release.}. If you can use PostScript or Ghostscript with your printer, -you can print the reference card immediately with @file{refcard.ps}. - -The release also includes the source for the reference card. You -can format it, using @TeX{}, by typing: - -@example -make refcard.dvi -@end example - -The @value{GDBN} reference card is designed to print in @dfn{landscape} -mode on US ``letter'' size paper; -that is, on a sheet 11 inches wide by 8.5 inches -high. You will need to specify this form of printing as an option to -your @sc{dvi} output program. - -@cindex documentation - -All the documentation for @value{GDBN} comes as part of the machine-readable -distribution. The documentation is written in Texinfo format, which is -a documentation system that uses a single source file to produce both -on-line information and a printed manual. You can use one of the Info -formatting commands to create the on-line version of the documentation -and @TeX{} (or @code{texi2roff}) to typeset the printed version. - -@value{GDBN} includes an already formatted copy of the on-line Info -version of this manual in the @file{gdb} subdirectory. The main Info -file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to -subordinate files matching @samp{gdb.info*} in the same directory. If -necessary, you can print out these files, or read them with any editor; -but they are easier to read using the @code{info} subsystem in @sc{gnu} -Emacs or the standalone @code{info} program, available as part of the -@sc{gnu} Texinfo distribution. - -If you want to format these Info files yourself, you need one of the -Info formatting programs, such as @code{texinfo-format-buffer} or -@code{makeinfo}. - -If you have @code{makeinfo} installed, and are in the top level -@value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of -version @value{GDBVN}), you can make the Info file by typing: - -@example -cd gdb -make gdb.info -@end example - -If you want to typeset and print copies of this manual, you need @TeX{}, -a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the -Texinfo definitions file. - -@TeX{} is a typesetting program; it does not print files directly, but -produces output files called @sc{dvi} files. To print a typeset -document, you need a program to print @sc{dvi} files. If your system -has @TeX{} installed, chances are it has such a program. The precise -command to use depends on your system; @kbd{lpr -d} is common; another -(for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may -require a file name without any extension or a @samp{.dvi} extension. - -@TeX{} also requires a macro definitions file called -@file{texinfo.tex}. This file tells @TeX{} how to typeset a document -written in Texinfo format. On its own, @TeX{} cannot either read or -typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB -and is located in the @file{gdb-@var{version-number}/texinfo} -directory. - -If you have @TeX{} and a @sc{dvi} printer program installed, you can -typeset and print this manual. First switch to the the @file{gdb} -subdirectory of the main source directory (for example, to -@file{gdb-@value{GDBVN}/gdb}) and type: - -@example -make gdb.dvi -@end example - -Then give @file{gdb.dvi} to your @sc{dvi} printing program. - -@node Installing GDB -@appendix Installing @value{GDBN} -@cindex configuring @value{GDBN} -@cindex installation - -@value{GDBN} comes with a @code{configure} script that automates the process -of preparing @value{GDBN} for installation; you can then use @code{make} to -build the @code{gdb} program. -@iftex -@c irrelevant in info file; it's as current as the code it lives with. -@footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN}, -look at the @file{README} file in the sources; we may have improved the -installation procedures since publishing this manual.} -@end iftex - -The @value{GDBN} distribution includes all the source code you need for -@value{GDBN} in a single directory, whose name is usually composed by -appending the version number to @samp{gdb}. - -For example, the @value{GDBN} version @value{GDBVN} distribution is in the -@file{gdb-@value{GDBVN}} directory. That directory contains: - -@table @code -@item gdb-@value{GDBVN}/configure @r{(and supporting files)} -script for configuring @value{GDBN} and all its supporting libraries - -@item gdb-@value{GDBVN}/gdb -the source specific to @value{GDBN} itself - -@item gdb-@value{GDBVN}/bfd -source for the Binary File Descriptor library - -@item gdb-@value{GDBVN}/include -@sc{gnu} include files - -@item gdb-@value{GDBVN}/libiberty -source for the @samp{-liberty} free software library - -@item gdb-@value{GDBVN}/opcodes -source for the library of opcode tables and disassemblers - -@item gdb-@value{GDBVN}/readline -source for the @sc{gnu} command-line interface - -@item gdb-@value{GDBVN}/glob -source for the @sc{gnu} filename pattern-matching subroutine - -@item gdb-@value{GDBVN}/mmalloc -source for the @sc{gnu} memory-mapped malloc package -@end table - -The simplest way to configure and build @value{GDBN} is to run @code{configure} -from the @file{gdb-@var{version-number}} source directory, which in -this example is the @file{gdb-@value{GDBVN}} directory. - -First switch to the @file{gdb-@var{version-number}} source directory -if you are not already in it; then run @code{configure}. Pass the -identifier for the platform on which @value{GDBN} will run as an -argument. - -For example: - -@example -cd gdb-@value{GDBVN} -./configure @var{host} -make -@end example - -@noindent -where @var{host} is an identifier such as @samp{sun4} or -@samp{decstation}, that identifies the platform where @value{GDBN} will run. -(You can often leave off @var{host}; @code{configure} tries to guess the -correct value by examining your system.) - -Running @samp{configure @var{host}} and then running @code{make} builds the -@file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty} -libraries, then @code{gdb} itself. The configured source files, and the -binaries, are left in the corresponding source directories. - -@need 750 -@code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your -system does not recognize this automatically when you run a different -shell, you may need to run @code{sh} on it explicitly: - -@example -sh configure @var{host} -@end example - -If you run @code{configure} from a directory that contains source -directories for multiple libraries or programs, such as the -@file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure} -creates configuration files for every directory level underneath (unless -you tell it not to, with the @samp{--norecursion} option). - -You can run the @code{configure} script from any of the -subordinate directories in the @value{GDBN} distribution if you only want to -configure that subdirectory, but be sure to specify a path to it. - -For example, with version @value{GDBVN}, type the following to configure only -the @code{bfd} subdirectory: - -@example -@group -cd gdb-@value{GDBVN}/bfd -../configure @var{host} -@end group -@end example - -You can install @code{@value{GDBP}} anywhere; it has no hardwired paths. -However, you should make sure that the shell on your path (named by -the @samp{SHELL} environment variable) is publicly readable. Remember -that @value{GDBN} uses the shell to start your program---some systems refuse to -let @value{GDBN} debug child processes whose programs are not readable. - -@menu -* Separate Objdir:: Compiling @value{GDBN} in another directory -* Config Names:: Specifying names for hosts and targets -* Configure Options:: Summary of options for configure -@end menu - -@node Separate Objdir -@section Compiling @value{GDBN} in another directory - -If you want to run @value{GDBN} versions for several host or target machines, -you need a different @code{gdb} compiled for each combination of -host and target. @code{configure} is designed to make this easy by -allowing you to generate each configuration in a separate subdirectory, -rather than in the source directory. If your @code{make} program -handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running -@code{make} in each of these directories builds the @code{gdb} -program specified there. - -To build @code{gdb} in a separate directory, run @code{configure} -with the @samp{--srcdir} option to specify where to find the source. -(You also need to specify a path to find @code{configure} -itself from your working directory. If the path to @code{configure} -would be the same as the argument to @samp{--srcdir}, you can leave out -the @samp{--srcdir} option; it is assumed.) - -For example, with version @value{GDBVN}, you can build @value{GDBN} in a -separate directory for a Sun 4 like this: - -@example -@group -cd gdb-@value{GDBVN} -mkdir ../gdb-sun4 -cd ../gdb-sun4 -../gdb-@value{GDBVN}/configure sun4 -make -@end group -@end example - -When @code{configure} builds a configuration using a remote source -directory, it creates a tree for the binaries with the same structure -(and using the same names) as the tree under the source directory. In -the example, you'd find the Sun 4 library @file{libiberty.a} in the -directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in -@file{gdb-sun4/gdb}. - -One popular reason to build several @value{GDBN} configurations in separate -directories is to configure @value{GDBN} for cross-compiling (where -@value{GDBN} runs on one machine---the @dfn{host}---while debugging -programs that run on another machine---the @dfn{target}). -You specify a cross-debugging target by -giving the @samp{--target=@var{target}} option to @code{configure}. - -When you run @code{make} to build a program or library, you must run -it in a configured directory---whatever directory you were in when you -called @code{configure} (or one of its subdirectories). - -The @code{Makefile} that @code{configure} generates in each source -directory also runs recursively. If you type @code{make} in a source -directory such as @file{gdb-@value{GDBVN}} (or in a separate configured -directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you -will build all the required libraries, and then build GDB. - -When you have multiple hosts or targets configured in separate -directories, you can run @code{make} on them in parallel (for example, -if they are NFS-mounted on each of the hosts); they will not interfere -with each other. - -@node Config Names -@section Specifying names for hosts and targets - -The specifications used for hosts and targets in the @code{configure} -script are based on a three-part naming scheme, but some short predefined -aliases are also supported. The full naming scheme encodes three pieces -of information in the following pattern: - -@example -@var{architecture}-@var{vendor}-@var{os} -@end example - -For example, you can use the alias @code{sun4} as a @var{host} argument, -or as the value for @var{target} in a @code{--target=@var{target}} -option. The equivalent full name is @samp{sparc-sun-sunos4}. - -The @code{configure} script accompanying @value{GDBN} does not provide -any query facility to list all supported host and target names or -aliases. @code{configure} calls the Bourne shell script -@code{config.sub} to map abbreviations to full names; you can read the -script, if you wish, or you can use it to test your guesses on -abbreviations---for example: - -@smallexample -% sh config.sub i386-linux -i386-pc-linux-gnu -% sh config.sub alpha-linux -alpha-unknown-linux-gnu -% sh config.sub hp9k700 -hppa1.1-hp-hpux -% sh config.sub sun4 -sparc-sun-sunos4.1.1 -% sh config.sub sun3 -m68k-sun-sunos4.1.1 -% sh config.sub i986v -Invalid configuration `i986v': machine `i986v' not recognized -@end smallexample - -@noindent -@code{config.sub} is also distributed in the @value{GDBN} source -directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}). - -@node Configure Options -@section @code{configure} options - -Here is a summary of the @code{configure} options and arguments that -are most often useful for building @value{GDBN}. @code{configure} also has -several other options not listed here. @inforef{What Configure -Does,,configure.info}, for a full explanation of @code{configure}. - -@example -configure @r{[}--help@r{]} - @r{[}--prefix=@var{dir}@r{]} - @r{[}--exec-prefix=@var{dir}@r{]} - @r{[}--srcdir=@var{dirname}@r{]} - @r{[}--norecursion@r{]} @r{[}--rm@r{]} - @r{[}--target=@var{target}@r{]} - @var{host} -@end example - -@noindent -You may introduce options with a single @samp{-} rather than -@samp{--} if you prefer; but you may abbreviate option names if you use -@samp{--}. - -@table @code -@item --help -Display a quick summary of how to invoke @code{configure}. - -@item --prefix=@var{dir} -Configure the source to install programs and files under directory -@file{@var{dir}}. - -@item --exec-prefix=@var{dir} -Configure the source to install programs under directory -@file{@var{dir}}. - -@c avoid splitting the warning from the explanation: -@need 2000 -@item --srcdir=@var{dirname} -@strong{Warning: using this option requires @sc{gnu} @code{make}, or another -@code{make} that implements the @code{VPATH} feature.}@* -Use this option to make configurations in directories separate from the -@value{GDBN} source directories. Among other things, you can use this to -build (or maintain) several configurations simultaneously, in separate -directories. @code{configure} writes configuration specific files in -the current directory, but arranges for them to use the source in the -directory @var{dirname}. @code{configure} creates directories under -the working directory in parallel to the source directories below -@var{dirname}. - -@item --norecursion -Configure only the directory level where @code{configure} is executed; do not -propagate configuration to subdirectories. - -@item --target=@var{target} -Configure @value{GDBN} for cross-debugging programs running on the specified -@var{target}. Without this option, @value{GDBN} is configured to debug -programs that run on the same machine (@var{host}) as @value{GDBN} itself. - -There is no convenient way to generate a list of all available targets. - -@item @var{host} @dots{} -Configure @value{GDBN} to run on the specified @var{host}. - -There is no convenient way to generate a list of all available hosts. -@end table - -There are many other options available as well, but they are generally -needed for special purposes only. - -@node Maintenance Commands -@appendix Maintenance Commands -@cindex maintenance commands -@cindex internal commands - -In addition to commands intended for @value{GDBN} users, @value{GDBN} -includes a number of commands intended for @value{GDBN} developers. -These commands are provided here for reference. - -@table @code -@kindex maint info breakpoints -@item @anchor{maint info breakpoints}maint info breakpoints -Using the same format as @samp{info breakpoints}, display both the -breakpoints you've set explicitly, and those @value{GDBN} is using for -internal purposes. Internal breakpoints are shown with negative -breakpoint numbers. The type column identifies what kind of breakpoint -is shown: - -@table @code -@item breakpoint -Normal, explicitly set breakpoint. - -@item watchpoint -Normal, explicitly set watchpoint. - -@item longjmp -Internal breakpoint, used to handle correctly stepping through -@code{longjmp} calls. - -@item longjmp resume -Internal breakpoint at the target of a @code{longjmp}. - -@item until -Temporary internal breakpoint used by the @value{GDBN} @code{until} command. - -@item finish -Temporary internal breakpoint used by the @value{GDBN} @code{finish} command. - -@item shlib events -Shared library events. - -@end table - -@end table - - -@node Remote Protocol -@appendix @value{GDBN} Remote Serial Protocol - -There may be occasions when you need to know something about the -protocol---for example, if there is only one serial port to your target -machine, you might want your program to do something special if it -recognizes a packet meant for @value{GDBN}. - -In the examples below, @samp{<-} and @samp{->} are used to indicate -transmitted and received data respectfully. - -@cindex protocol, @value{GDBN} remote serial -@cindex serial protocol, @value{GDBN} remote -@cindex remote serial protocol -All @value{GDBN} commands and responses (other than acknowledgments) are -sent as a @var{packet}. A @var{packet} is introduced with the character -@samp{$}, the actual @var{packet-data}, and the terminating character -@samp{#} followed by a two-digit @var{checksum}: - -@example -@code{$}@var{packet-data}@code{#}@var{checksum} -@end example -@noindent - -@cindex checksum, for @value{GDBN} remote -@noindent -The two-digit @var{checksum} is computed as the modulo 256 sum of all -characters between the leading @samp{$} and the trailing @samp{#} (an -eight bit unsigned checksum). - -Implementors should note that prior to @value{GDBN} 5.0 the protocol -specification also included an optional two-digit @var{sequence-id}: - -@example -@code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum} -@end example - -@cindex sequence-id, for @value{GDBN} remote -@noindent -That @var{sequence-id} was appended to the acknowledgment. @value{GDBN} -has never output @var{sequence-id}s. Stubs that handle packets added -since @value{GDBN} 5.0 must not accept @var{sequence-id}. - -@cindex acknowledgment, for @value{GDBN} remote -When either the host or the target machine receives a packet, the first -response expected is an acknowledgment: either @samp{+} (to indicate -the package was received correctly) or @samp{-} (to request -retransmission): - -@example -<- @code{$}@var{packet-data}@code{#}@var{checksum} --> @code{+} -@end example -@noindent - -The host (@value{GDBN}) sends @var{command}s, and the target (the -debugging stub incorporated in your program) sends a @var{response}. In -the case of step and continue @var{command}s, the response is only sent -when the operation has completed (the target has again stopped). - -@var{packet-data} consists of a sequence of characters with the -exception of @samp{#} and @samp{$} (see @samp{X} packet for additional -exceptions). - -Fields within the packet should be separated using @samp{,} @samp{;} or -@samp{:}. Except where otherwise noted all numbers are represented in -HEX with leading zeros suppressed. - -Implementors should note that prior to @value{GDBN} 5.0, the character -@samp{:} could not appear as the third character in a packet (as it -would potentially conflict with the @var{sequence-id}). - -Response @var{data} can be run-length encoded to save space. A @samp{*} -means that the next character is an @sc{ascii} encoding giving a repeat count -which stands for that many repetitions of the character preceding the -@samp{*}. The encoding is @code{n+29}, yielding a printable character -where @code{n >=3} (which is where rle starts to win). The printable -characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric -value greater than 126 should not be used. - -Some remote systems have used a different run-length encoding mechanism -loosely refered to as the cisco encoding. Following the @samp{*} -character are two hex digits that indicate the size of the packet. - -So: -@example -"@code{0* }" -@end example -@noindent -means the same as "0000". - -The error response returned for some packets includes a two character -error number. That number is not well defined. - -For any @var{command} not supported by the stub, an empty response -(@samp{$#00}) should be returned. That way it is possible to extend the -protocol. A newer @value{GDBN} can tell if a packet is supported based -on that response. - -A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M}, -@samp{c}, and @samp{s} @var{command}s. All other @var{command}s are -optional. - -Below is a complete list of all currently defined @var{command}s and -their corresponding response @var{data}: -@page -@multitable @columnfractions .30 .30 .40 -@item Packet -@tab Request -@tab Description - -@item extended mode -@tab @code{!} -@tab -Enable extended mode. In extended mode, the remote server is made -persistent. The @samp{R} packet is used to restart the program being -debugged. -@item -@tab reply @samp{OK} -@tab -The remote target both supports and has enabled extended mode. - -@item last signal -@tab @code{?} -@tab -Indicate the reason the target halted. The reply is the same as for step -and continue. -@item -@tab reply -@tab see below - - -@item reserved -@tab @code{a} -@tab Reserved for future use - -@item set program arguments @strong{(reserved)} -@tab @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,...} -@tab -@item -@tab -@tab -Initialized @samp{argv[]} array passed into program. @var{arglen} -specifies the number of bytes in the hex encoded byte stream @var{arg}. -See @file{gdbserver} for more details. -@item -@tab reply @code{OK} -@item -@tab reply @code{E}@var{NN} - -@item set baud @strong{(deprecated)} -@tab @code{b}@var{baud} -@tab -Change the serial line speed to @var{baud}. JTC: @emph{When does the -transport layer state change? When it's received, or after the ACK is -transmitted. In either case, there are problems if the command or the -acknowledgment packet is dropped.} Stan: @emph{If people really wanted -to add something like this, and get it working for the first time, they -ought to modify ser-unix.c to send some kind of out-of-band message to a -specially-setup stub and have the switch happen "in between" packets, so -that from remote protocol's point of view, nothing actually -happened.} - -@item set breakpoint @strong{(deprecated)} -@tab @code{B}@var{addr},@var{mode} -@tab -Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a -breakpoint at @var{addr}. @emph{This has been replaced by the @samp{Z} and -@samp{z} packets.} - -@item continue -@tab @code{c}@var{addr} -@tab -@var{addr} is address to resume. If @var{addr} is omitted, resume at -current address. -@item -@tab reply -@tab see below - -@item continue with signal -@tab @code{C}@var{sig}@code{;}@var{addr} -@tab -Continue with signal @var{sig} (hex signal number). If -@code{;}@var{addr} is omitted, resume at same address. -@item -@tab reply -@tab see below - -@item toggle debug @strong{(deprecated)} -@tab @code{d} -@tab -toggle debug flag. - -@item detach -@tab @code{D} -@tab -Detach @value{GDBN} from the remote system. Sent to the remote target before -@value{GDBN} disconnects. -@item -@tab reply @emph{no response} -@tab -@value{GDBN} does not check for any response after sending this packet. - -@item reserved -@tab @code{e} -@tab Reserved for future use - -@item reserved -@tab @code{E} -@tab Reserved for future use - -@item reserved -@tab @code{f} -@tab Reserved for future use - -@item reserved -@tab @code{F} -@tab Reserved for future use - -@item read registers -@tab @code{g} -@tab Read general registers. -@item -@tab reply @var{XX...} -@tab -Each byte of register data is described by two hex digits. The bytes -with the register are transmitted in target byte order. The size of -each register and their position within the @samp{g} @var{packet} are -determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE} and -@var{REGISTER_NAME} macros. The specification of several standard -@code{g} packets is specified below. -@item -@tab @code{E}@var{NN} -@tab for an error. - -@item write regs -@tab @code{G}@var{XX...} -@tab -See @samp{g} for a description of the @var{XX...} data. -@item -@tab reply @code{OK} -@tab for success -@item -@tab reply @code{E}@var{NN} -@tab for an error - -@item reserved -@tab @code{h} -@tab Reserved for future use - -@item set thread -@tab @code{H}@var{c}@var{t...} -@tab -Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g}, -@samp{G}, et.al.). @var{c} = @samp{c} for thread used in step and -continue; @var{t...} can be -1 for all threads. @var{c} = @samp{g} for -thread used in other operations. If zero, pick a thread, any thread. -@item -@tab reply @code{OK} -@tab for success -@item -@tab reply @code{E}@var{NN} -@tab for an error - -@c FIXME: JTC: -@c 'H': How restrictive (or permissive) is the thread model. If a -@c thread is selected and stopped, are other threads allowed -@c to continue to execute? As I mentioned above, I think the -@c semantics of each command when a thread is selected must be -@c described. For example: -@c -@c 'g': If the stub supports threads and a specific thread is -@c selected, returns the register block from that thread; -@c otherwise returns current registers. -@c -@c 'G' If the stub supports threads and a specific thread is -@c selected, sets the registers of the register block of -@c that thread; otherwise sets current registers. - -@item cycle step @strong{(draft)} -@tab @code{i}@var{addr}@code{,}@var{nnn} -@tab -Step the remote target by a single clock cycle. If @code{,}@var{nnn} is -present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle -step starting at that address. - -@item signal then cycle step @strong{(reserved)} -@tab @code{I} -@tab -See @samp{i} and @samp{S} for likely syntax and semantics. - -@item reserved -@tab @code{j} -@tab Reserved for future use - -@item reserved -@tab @code{J} -@tab Reserved for future use - -@item kill request -@tab @code{k} -@tab -FIXME: @emph{There is no description of how to operate when a specific -thread context has been selected (i.e.@: does 'k' kill only that thread?)}. - -@item reserved -@tab @code{l} -@tab Reserved for future use - -@item reserved -@tab @code{L} -@tab Reserved for future use - -@item read memory -@tab @code{m}@var{addr}@code{,}@var{length} -@tab -Read @var{length} bytes of memory starting at address @var{addr}. -Neither @value{GDBN} nor the stub assume that sized memory transfers are assumed -using word alligned accesses. FIXME: @emph{A word aligned memory -transfer mechanism is needed.} -@item -@tab reply @var{XX...} -@tab -@var{XX...} is mem contents. Can be fewer bytes than requested if able -to read only part of the data. Neither @value{GDBN} nor the stub assume that -sized memory transfers are assumed using word alligned accesses. FIXME: -@emph{A word aligned memory transfer mechanism is needed.} -@item -@tab reply @code{E}@var{NN} -@tab @var{NN} is errno - -@item write mem -@tab @code{M}@var{addr},@var{length}@code{:}@var{XX...} -@tab -Write @var{length} bytes of memory starting at address @var{addr}. -@var{XX...} is the data. -@item -@tab reply @code{OK} -@tab for success -@item -@tab reply @code{E}@var{NN} -@tab -for an error (this includes the case where only part of the data was -written). - -@item reserved -@tab @code{n} -@tab Reserved for future use - -@item reserved -@tab @code{N} -@tab Reserved for future use - -@item reserved -@tab @code{o} -@tab Reserved for future use - -@item reserved -@tab @code{O} -@tab Reserved for future use - -@item read reg @strong{(reserved)} -@tab @code{p}@var{n...} -@tab -See write register. -@item -@tab return @var{r....} -@tab The hex encoded value of the register in target byte order. - -@item write reg -@tab @code{P}@var{n...}@code{=}@var{r...} -@tab -Write register @var{n...} with value @var{r...}, which contains two hex -digits for each byte in the register (target byte order). -@item -@tab reply @code{OK} -@tab for success -@item -@tab reply @code{E}@var{NN} -@tab for an error - -@item general query -@tab @code{q}@var{query} -@tab -Request info about @var{query}. In general @value{GDBN} queries -have a leading upper case letter. Custom vendor queries should use a -company prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may -optionally be followed by a @samp{,} or @samp{;} separated list. Stubs -must ensure that they match the full @var{query} name. -@item -@tab reply @code{XX...} -@tab Hex encoded data from query. The reply can not be empty. -@item -@tab reply @code{E}@var{NN} -@tab error reply -@item -@tab reply @samp{} -@tab Indicating an unrecognized @var{query}. - -@item general set -@tab @code{Q}@var{var}@code{=}@var{val} -@tab -Set value of @var{var} to @var{val}. See @samp{q} for a discussing of -naming conventions. - -@item reset @strong{(deprecated)} -@tab @code{r} -@tab -Reset the entire system. - -@item remote restart -@tab @code{R}@var{XX} -@tab -Restart the program being debugged. @var{XX}, while needed, is ignored. -This packet is only available in extended mode. -@item -@tab -no reply -@tab -The @samp{R} packet has no reply. - -@item step -@tab @code{s}@var{addr} -@tab -@var{addr} is address to resume. If @var{addr} is omitted, resume at -same address. -@item -@tab reply -@tab see below - -@item step with signal -@tab @code{S}@var{sig}@code{;}@var{addr} -@tab -Like @samp{C} but step not continue. -@item -@tab reply -@tab see below - -@item search -@tab @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} -@tab -Search backwards starting at address @var{addr} for a match with pattern -@var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 -bytes. @var{addr} must be at least 3 digits. - -@item thread alive -@tab @code{T}@var{XX} -@tab Find out if the thread XX is alive. -@item -@tab reply @code{OK} -@tab thread is still alive -@item -@tab reply @code{E}@var{NN} -@tab thread is dead - -@item reserved -@tab @code{u} -@tab Reserved for future use - -@item reserved -@tab @code{U} -@tab Reserved for future use - -@item reserved -@tab @code{v} -@tab Reserved for future use - -@item reserved -@tab @code{V} -@tab Reserved for future use - -@item reserved -@tab @code{w} -@tab Reserved for future use - -@item reserved -@tab @code{W} -@tab Reserved for future use - -@item reserved -@tab @code{x} -@tab Reserved for future use - -@item write mem (binary) -@tab @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX...} -@tab -@var{addr} is address, @var{length} is number of bytes, @var{XX...} is -binary data. The characters @code{$}, @code{#}, and @code{0x7d} are -escaped using @code{0x7d}. -@item -@tab reply @code{OK} -@tab for success -@item -@tab reply @code{E}@var{NN} -@tab for an error - -@item reserved -@tab @code{y} -@tab Reserved for future use - -@item reserved -@tab @code{Y} -@tab Reserved for future use - -@item remove break or watchpoint @strong{(draft)} -@tab @code{z}@var{t}@code{,}@var{addr}@code{,}@var{length} -@tab -See @samp{Z}. - -@item insert break or watchpoint @strong{(draft)} -@tab @code{Z}@var{t}@code{,}@var{addr}@code{,}@var{length} -@tab -@var{t} is type: @samp{0} - software breakpoint, @samp{1} - hardware -breakpoint, @samp{2} - write watchpoint, @samp{3} - read watchpoint, -@samp{4} - access watchpoint; @var{addr} is address; @var{length} is in -bytes. For a software breakpoint, @var{length} specifies the size of -the instruction to be patched. For hardware breakpoints and watchpoints -@var{length} specifies the memory region to be monitored. To avoid -potential problems with duplicate packets, the operations should be -implemented in an idempotent way. -@item -@tab reply @code{E}@var{NN} -@tab for an error -@item -@tab reply @code{OK} -@tab for success -@item -@tab @samp{} -@tab If not supported. - -@item reserved -@tab <other> -@tab Reserved for future use - -@end multitable - -The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can -receive any of the below as a reply. In the case of the @samp{C}, -@samp{c}, @samp{S} and @samp{s} packets, that reply is only returned -when the target halts. In the below the exact meaning of @samp{signal -number} is poorly defined. In general one of the UNIX signal numbering -conventions is used. - -@multitable @columnfractions .4 .6 - -@item @code{S}@var{AA} -@tab @var{AA} is the signal number - -@item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;} -@tab -@var{AA} = two hex digit signal number; @var{n...} = register number -(hex), @var{r...} = target byte ordered register contents, size defined -by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} = -thread process ID, this is a hex integer; @var{n...} = other string not -starting with valid hex digit. @value{GDBN} should ignore this -@var{n...}, @var{r...} pair and go on to the next. This way we can -extend the protocol. - -@item @code{W}@var{AA} -@tab -The process exited, and @var{AA} is the exit status. This is only -applicable for certains sorts of targets. - -@item @code{X}@var{AA} -@tab -The process terminated with signal @var{AA}. - -@item @code{N}@var{AA}@code{;}@var{t...}@code{;}@var{d...}@code{;}@var{b...} @strong{(obsolete)} -@tab -@var{AA} = signal number; @var{t...} = address of symbol "_start"; -@var{d...} = base of data section; @var{b...} = base of bss section. -@emph{Note: only used by Cisco Systems targets. The difference between -this reply and the "qOffsets" query is that the 'N' packet may arrive -spontaneously whereas the 'qOffsets' is a query initiated by the host -debugger.} - -@item @code{O}@var{XX...} -@tab -@var{XX...} is hex encoding of @sc{ascii} data. This can happen at any time -while the program is running and the debugger should continue to wait -for 'W', 'T', etc. - -@end multitable - -The following set and query packets have already been defined. - -@multitable @columnfractions .2 .2 .6 - -@item current thread -@tab @code{q}@code{C} -@tab Return the current thread id. -@item -@tab reply @code{QC}@var{pid} -@tab -Where @var{pid} is a HEX encoded 16 bit process id. -@item -@tab reply * -@tab Any other reply implies the old pid. - -@item all thread ids -@tab @code{q}@code{fThreadInfo} -@item -@tab @code{q}@code{sThreadInfo} -@tab -Obtain a list of active thread ids from the target (OS). Since there -may be too many active threads to fit into one reply packet, this query -works iteratively: it may require more than one query/reply sequence to -obtain the entire list of threads. The first query of the sequence will -be the @code{qf}@code{ThreadInfo} query; subsequent queries in the -sequence will be the @code{qs}@code{ThreadInfo} query. -@item -@tab -@tab NOTE: replaces the @code{qL} query (see below). -@item -@tab reply @code{m}@var{<id>} -@tab A single thread id -@item -@tab reply @code{m}@var{<id>},@var{<id>...} -@tab a comma-separated list of thread ids -@item -@tab reply @code{l} -@tab (lower case 'el') denotes end of list. -@item -@tab -@tab -In response to each query, the target will reply with a list of one -or more thread ids, in big-endian hex, separated by commas. GDB will -respond to each reply with a request for more thread ids (using the -@code{qs} form of the query), until the target responds with @code{l} -(lower-case el, for @code{'last'}). - -@item extra thread info -@tab @code{q}@code{ThreadExtraInfo}@code{,}@var{id} -@tab -@item -@tab -@tab -Where @var{<id>} is a thread-id in big-endian hex. -Obtain a printable string description of a thread's attributes from -the target OS. This string may contain anything that the target OS -thinks is interesting for @value{GDBN} to tell the user about the thread. -The string is displayed in @value{GDBN}'s @samp{info threads} display. -Some examples of possible thread extra info strings are "Runnable", or -"Blocked on Mutex". -@item -@tab reply @var{XX...} -@tab -Where @var{XX...} is a hex encoding of @sc{ascii} data, comprising the -printable string containing the extra information about the thread's -attributes. - -@item query @var{LIST} or @var{threadLIST} @strong{(deprecated)} -@tab @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} -@tab -@item -@tab -@tab -Obtain thread information from RTOS. Where: @var{startflag} (one hex -digit) is one to indicate the first query and zero to indicate a -subsequent query; @var{threadcount} (two hex digits) is the maximum -number of threads the response packet can contain; and @var{nextthread} -(eight hex digits), for subsequent queries (@var{startflag} is zero), is -returned in the response as @var{argthread}. -@item -@tab -@tab NOTE: this query is replaced by the @code{q}@code{fThreadInfo} -query (see above). -@item -@tab reply @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread...} -@tab -@item -@tab -@tab -Where: @var{count} (two hex digits) is the number of threads being -returned; @var{done} (one hex digit) is zero to indicate more threads -and one indicates no further threads; @var{argthreadid} (eight hex -digits) is @var{nextthread} from the request packet; @var{thread...} is -a sequence of thread IDs from the target. @var{threadid} (eight hex -digits). See @code{remote.c:parse_threadlist_response()}. - -@item compute CRC of memory block -@tab @code{q}@code{CRC:}@var{addr}@code{,}@var{length} -@tab -@item -@tab reply @code{E}@var{NN} -@tab An error (such as memory fault) -@item -@tab reply @code{C}@var{CRC32} -@tab A 32 bit cyclic redundancy check of the specified memory region. - -@item query sect offs -@tab @code{q}@code{Offsets} -@tab -Get section offsets that the target used when re-locating the downloaded -image. @emph{Note: while a @code{Bss} offset is included in the -response, @value{GDBN} ignores this and instead applies the @code{Data} -offset to the @code{Bss} section.} -@item -@tab reply @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz} - -@item thread info request -@tab @code{q}@code{P}@var{mode}@var{threadid} -@tab -@item -@tab -@tab -Returns information on @var{threadid}. Where: @var{mode} is a hex -encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID. -@item -@tab reply * -@tab -See @code{remote.c:remote_unpack_thread_info_response()}. - -@item remote command -@tab @code{q}@code{Rcmd,}@var{COMMAND} -@tab -@item -@tab -@tab -@var{COMMAND} (hex encoded) is passed to the local interpreter for -execution. Invalid commands should be reported using the output string. -Before the final result packet, the target may also respond with a -number of intermediate @code{O}@var{OUTPUT} console output -packets. @emph{Implementors should note that providing access to a -stubs's interpreter may have security implications}. -@item -@tab reply @code{OK} -@tab -A command response with no output. -@item -@tab reply @var{OUTPUT} -@tab -A command response with the hex encoded output string @var{OUTPUT}. -@item -@tab reply @code{E}@var{NN} -@tab -Indicate a badly formed request. - -@item -@tab reply @samp{} -@tab -When @samp{q}@samp{Rcmd} is not recognized. - -@item symbol lookup -@tab @code{qSymbol::} -@tab -Notify the target that @value{GDBN} is prepared to serve symbol lookup -requests. Accept requests from the target for the values of symbols. -@item -@tab -@tab -@item -@tab reply @code{OK} -@tab -The target does not need to look up any (more) symbols. -@item -@tab reply @code{qSymbol:}@var{sym_name} -@tab -@sp 2 -@noindent -The target requests the value of symbol @var{sym_name} (hex encoded). -@value{GDBN} may provide the value by using the -@code{qSymbol:}@var{sym_value}:@var{sym_name} -message, described below. - -@item symbol value -@tab @code{qSymbol:}@var{sym_value}:@var{sym_name} -@tab -@sp 1 -@noindent -Set the value of SYM_NAME to SYM_VALUE. -@item -@tab -@tab -@var{sym_name} (hex encoded) is the name of a symbol whose value -the target has previously requested. -@item -@tab -@tab -@var{sym_value} (hex) is the value for symbol @var{sym_name}. -If @value{GDBN} cannot supply a value for @var{sym_name}, then this -field will be empty. -@item -@tab reply @code{OK} -@tab -The target does not need to look up any (more) symbols. -@item -@tab reply @code{qSymbol:}@var{sym_name} -@tab -@sp 2 -@noindent -The target requests the value of a new symbol @var{sym_name} (hex encoded). -@value{GDBN} will continue to supply the values of symbols (if available), -until the target ceases to request them. - -@end multitable - -The following @samp{g}/@samp{G} packets have previously been defined. -In the below, some thirty-two bit registers are transferred as sixty-four -bits. Those registers should be zero/sign extended (which?) to fill the -space allocated. Register bytes are transfered in target byte order. -The two nibbles within a register byte are transfered most-significant - -least-significant. - -@multitable @columnfractions .5 .5 - -@item MIPS32 -@tab -All registers are transfered as thirty-two bit quantities in the order: -32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point -registers; fsr; fir; fp. - -@item MIPS64 -@tab -All registers are transfered as sixty-four bit quantities (including -thirty-two bit registers such as @code{sr}). The ordering is the same -as @code{MIPS32}. - -@end multitable - -Example sequence of a target being re-started. Notice how the restart -does not get any direct output: - -@example -<- @code{R00} --> @code{+} -@emph{target restarts} -<- @code{?} --> @code{+} --> @code{T001:1234123412341234} -<- @code{+} -@end example - -Example sequence of a target being stepped by a single instruction: - -@example -<- @code{G1445...} --> @code{+} -<- @code{s} --> @code{+} -@emph{time passes} --> @code{T001:1234123412341234} -<- @code{+} -<- @code{g} --> @code{+} --> @code{1455...} -<- @code{+} -@end example - - -@include fdl.texi - -@node Index -@unnumbered Index - -@printindex cp - -@tex -% I think something like @colophon should be in texinfo. In the -% meantime: -\long\def\colophon{\hbox to0pt{}\vfill -\centerline{The body of this manual is set in} -\centerline{\fontname\tenrm,} -\centerline{with headings in {\bf\fontname\tenbf}} -\centerline{and examples in {\tt\fontname\tentt}.} -\centerline{{\it\fontname\tenit\/},} -\centerline{{\bf\fontname\tenbf}, and} -\centerline{{\sl\fontname\tensl\/}} -\centerline{are used for emphasis.}\vfill} -\page\colophon -% Blame: doc@cygnus.com, 1991. -@end tex - -@bye |