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diff --git a/gdb/doc/interim-gdb.texinfo b/gdb/doc/interim-gdb.texinfo index 53a01e4..e69de29 100755 --- a/gdb/doc/interim-gdb.texinfo +++ b/gdb/doc/interim-gdb.texinfo @@ -1,7901 +0,0 @@ -_dnl__ -*-Texinfo-*- -_dnl__ Copyright (c) 1988 1989 1990 1991 Free Software Foundation, Inc. -\input texinfo -@setfilename _GDBP__.info -@c $Id$ -@c THIS MANUAL REQUIRES TEXINFO-2 macros and info-makers to format properly. -@c -@c NOTE: this manual is marked up for preprocessing with a collection -@c of m4 macros called "pretex.m4". If you see <_if__> and <_fi__> -@c scattered around the source, you have the full source before -@c preprocessing; if you don't, you have the source configured for -@c _HOST__ architectures (and you can of course get the full source, -@c with all configurations, from wherever you got this). -_if__(0) - -THIS IS THE SOURCE PRIOR TO PREPROCESSING. The full source needs to -be run through m4 before either tex- or info- formatting: for example, -_0__ - m4 pretex.m4 none.m4 all.m4 gdb.texinfo >gdb-all.texinfo -_1__ -will produce (assuming your path finds either GNU m4 >= 0.84, or SysV -m4; Berkeley won't do) a file suitable for formatting. See the text in -"pretex.m4" for a fuller explanation (and the macro definitions). - -_fi__(0) -_include__(gdbVN.m4) -@tex -\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ -\xdef\manvers{\$Revision$} % For use in headers, footers too -@end tex -@c -@syncodeindex ky cp -@c FOR UPDATES LEADING TO THIS DRAFT, GDB CHANGELOG CONSULTED BETWEEN: -@c Fri Sep 20 16:10:52 1991 John Gilmore (gnu at cygnus.com) -@c Sat Dec 22 02:51:40 1990 John Gilmore (gnu at cygint) -@ifinfo -This file documents the GNU debugger _GDBN__. - -Copyright (C) 1988, 1989, 1990, 1991 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -@ignore -Permission is granted to process this file through TeX and print the -results, provided the printed document carries copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). - -@end ignore -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled ``GNU General Public License'' is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this -one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled ``GNU General Public License'' may be -included in a translation approved by the Free Software Foundation -instead of in the original English. -@end ifinfo -@c @smallbook -@setchapternewpage odd -_if__(_GENERIC__) -@settitle Using _GDBN__ (<v>_GDB_VN__) -_fi__(_GENERIC__) -_if__(!_GENERIC__) -@settitle Using _GDBN__ <v>_GDB_VN__ (_HOST__) -_fi__(!_GENERIC__) -@iftex -@finalout -@end iftex -@titlepage -@title{Using _GDBN__} -@subtitle{A Guide to the GNU Source-Level Debugger} -_if__(!_GENERIC__) -@subtitle{On _HOST__ Systems} -_fi__(!_GENERIC__) -@sp 1 -@c Maybe crank this up to "Fourth Edition" when released at FSF -@c @subtitle Third Edition---_GDBN__ version _GDB_VN__ -@subtitle _GDBN__ version _GDB_VN__ -@subtitle July 1991 -@author{Richard M. Stallman@qquad @hfill Free Software Foundation} -@author{Roland H. Pesch@qquad @hfill Cygnus Support} -@page -@tex -{\parskip=0pt -\hfill rms\@ai.mit.edu, pesch\@cygnus.com\par -\hfill {\it Using _GDBN__}, \manvers\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex - -@vskip 0pt plus 1filll -Copyright @copyright{} 1988, 1989, 1990, 1991 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled ``GNU General Public License'' is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this -one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled ``GNU General Public License'' may be -included in a translation approved by the Free Software Foundation -instead of in the original English. -@end titlepage -@page - -@node Top, Summary, (dir), (dir) -@ifinfo -This file describes version _GDB_VN__ of GDB, the GNU symbolic debugger. -@end ifinfo - -@menu -* Summary:: Summary of _GDBN__ -* New Features:: New Features in _GDBN__ version _GDB_VN__ -* Sample Session:: A Sample _GDBN__ Session -* Invocation:: Getting In and Out of _GDBN__ -* Commands:: _GDBN__ Commands -* Running:: Running Programs Under _GDBN__ -* Stopping:: Stopping and Continuing -* Stack:: Examining the Stack -* Source:: Examining Source Files -* Data:: Examining Data -* Languages:: Using _GDBN__ with Different Languages -* Symbols:: Examining the Symbol Table -* Altering:: Altering Execution -* _GDBN__ Files:: _GDBN__'s Files -* Targets:: Specifying a Debugging Target -* Controlling _GDBN__:: Controlling _GDBN__ -* Sequences:: Canned Sequences of Commands -* Emacs:: Using _GDBN__ under GNU Emacs -* _GDBN__ Bugs:: Reporting Bugs in _GDBN__ -* Renamed Commands:: -* Installing _GDBN__:: Installing _GDBN__ -* Copying:: GNU GENERAL PUBLIC LICENSE -* Index:: Index - - --- The Detailed Node Listing --- - -Summary of _GDBN__ - -* Free Software:: Free Software -* Contributors:: Contributors to _GDBN__ - -Getting In and Out of _GDBN__ - -* Starting _GDBN__:: Starting _GDBN__ -* Leaving _GDBN__:: Leaving _GDBN__ -* Shell Commands:: Shell Commands - -Starting _GDBN__ - -* File Options:: Choosing Files -* Mode Options:: Choosing Modes - -_GDBN__ Commands - -* Command Syntax:: Command Syntax -* Help:: Getting Help - -Running Programs Under _GDBN__ - -* 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 - -Stopping and Continuing - -* Breakpoints:: Breakpoints, Watchpoints, and Exceptions -* Continuing and Stepping:: Resuming Execution -* Signals:: Signals - -Breakpoints, Watchpoints, and Exceptions - -* Set Breaks:: Setting Breakpoints -* Set Watchpoints:: Setting Watchpoints -* Exception Handling:: Breakpoints and Exceptions -* 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'' - -Examining the Stack - -* Frames:: Stack Frames -* Backtrace:: Backtraces -* Selection:: Selecting a Frame -* Frame Info:: Information on a Frame - -Examining Source Files - -* List:: Printing Source Lines -* Search:: Searching Source Files -* Source Path:: Specifying Source Directories -* Machine Code:: Source and Machine Code - -Examining Data - -* 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 - -Using GDB with Different Languages - -* Setting:: Switching between source languages -* Show:: Displaying the language -* Checks:: Type and Range checks -* Support:: Supported languages - -Switching between source languages - -* Manually:: Setting the working language manually -* Automatically:: Having GDB infer the source language - -Type and range Checking - -* Type Checking:: An overview of type checking -* Range Checking:: An overview of range checking - -Supported Languages - -* C:: C and C++ -* Modula-2:: Modula-2 - -C and C++ - -* C Operators:: C and C++ Operators -* C Constants:: C and C++ Constants -* Cplusplus expressions:: C++ Expressions -* C Defaults:: Default settings for C and C++ -* C Checks:: C and C++ Type and Range Checks -* Debugging C:: _GDBN__ and C -* Debugging C plus plus:: Special features for C++ - -Modula-2 - -* M2 Operators:: Built-in operators -* Builtin 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:: GDB and Modula-2 - -Altering Execution - -* Assignment:: Assignment to Variables -* Jumping:: Continuing at a Different Address -* Signaling:: Giving the Program a Signal -* Returning:: Returning from a Function -* Calling:: Calling your Program's Functions -* Patching:: Patching your Program - -_GDBN__'s Files - -* Files:: Commands to Specify Files -* Symbol Errors:: Errors Reading Symbol Files - -Specifying a Debugging Target - -* Active Targets:: Active Targets -* Target Commands:: Commands for Managing Targets -* Remote:: Remote Debugging - -Remote Debugging - -* i960-Nindy Remote:: _GDBN__ with a Remote i960 (Nindy) -* EB29K Remote:: _GDBN__ with a Remote EB29K -* VxWorks Remote:: _GDBN__ and VxWorks - -_GDBN__ with a Remote i960 (Nindy) - -* Nindy Startup:: Startup with Nindy -* Nindy Options:: Options for Nindy -* Nindy reset:: Nindy Reset Command - -_GDBN__ with a Remote EB29K - -* Comms (EB29K):: Communications Setup -* gdb-EB29K:: EB29K cross-debugging -* Remote Log:: Remote Log - -_GDBN__ and VxWorks - -* VxWorks connection:: Connecting to VxWorks -* VxWorks download:: VxWorks Download -* VxWorks attach:: Running Tasks - -Controlling _GDBN__ - -* Prompt:: Prompt -* Editing:: Command Editing -* History:: Command History -* Screen Size:: Screen Size -* Numbers:: Numbers -* Messages/Warnings:: Optional Warnings and Messages - -Canned Sequences of Commands - -* Define:: User-Defined Commands -* Command Files:: Command Files -* Output:: Commands for Controlled Output - -Reporting Bugs in _GDBN__ - -* Bug Criteria:: Have You Found a Bug? -* Bug Reporting:: How to Report Bugs - -Installing GDB - -* Subdirectories:: Configuration subdirectories -* Config Names:: Specifying names for hosts and targets -* configure Options:: Summary of options for configure -* Formatting Documentation:: How to format and print GDB documentation -@end menu - -@node Summary, New Features, Top, Top -@unnumbered Summary of _GDBN__ - -The purpose of a debugger such as _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. - -_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 _GDBN__ to debug programs written in C, C++, and Modula-2. -Fortran support will be added when a GNU Fortran compiler is ready. - -@menu -* Free Software:: Free Software -* Contributors:: Contributors to GDB -@end menu - -@node Free Software, Contributors, Summary, Summary -@unnumberedsec Free Software -_GDBN__ is @dfn{free software}, protected by the 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 can't take these freedoms away -from anyone else. - -@c FIXME: (passim) go through all xrefs, expanding to use text headings -For full details, @pxref{Copying}. -@node Contributors, , Free Software, Summary -@unnumberedsec Contributors to GDB - -Richard Stallman was the original author of GDB, and of many other 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 GDB 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; let's 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 long labor as thankless, we -particularly thank those who shepherded GDB through major releases: John -Gilmore (releases _GDB_VN__, 4.0); Jim Kingdon (releases 3.9, 3.5, 3.4, 3.3); -and Randy Smith (releases 3.2, 3.1, 3.0). As major maintainer of GDB -for some period, each contributed significantly to the structure, -stability, and capabilities of the entire debugger. - -Richard Stallman, assisted at various times by Pete TerMaat, Chris -Hanson, and Richard Mlynarik, handled releases through 2.8. - -Michael Tiemann is the author of most of the GNU C++ support in GDB, -with significant additional contributions from Per Bothner. James -Clark wrote the GNU C++ demangler. Early work on C++ was by Peter -TerMaat (who also did much general update work leading to release 3.0). - -GDB _GDB_VN__ uses the BFD subroutine library to examine multiple -object-file formats; BFD was a joint project of V. Gumby -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. - -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. -Keith Packard contributed NS32K support. Doug Rabson contributed -Acorn Risc Machine 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. - -Rich Schaefer and Peter Schauer helped with support of SunOS shared -libraries. - -Jay Fenlason and Roland McGrath ensured that GDB and GAS agree about -several machine instruction sets. - -Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped -develop remote debugging. Intel Corporation and Wind River Systems -contributed remote debugging modules for their products. - -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 and -the Modula-2 support, and contributed the Languages chapter of this -manual. - -@node New Features, Sample Session, Summary, Top -@unnumbered New Features since _GDBN__ version 3.5 - -@table @emph -@item Targets -Using the new command @code{target}, you can select at runtime whether -you are debugging local files, local processes, standalone systems over -a serial port, realtime systems over a TCP/IP connection, etc. The -command @code{load} can download programs into a remote system. Serial -stubs are available for Motorola 680x0 and Intel 80386 remote systems; -_GDBN__ also supports debugging realtime processes running under -VxWorks, using SunRPC Remote Procedure Calls over TCP/IP to talk to a -debugger stub on the target system. Internally, _GDBN__ now uses a -function vector to mediate access to different targets; if you need to -add your own support for a remote protocol, this makes it much easier. - -@item Watchpoints -_GDBN__ now sports watchpoints as well as breakpoints. You can use a -watchpoint to stop execution whenever the value of an expression -changes, without having to predict a particular place in your program -where this may happen. - -@item Wide Output -Commands that issue wide output now insert newlines at places designed -to make the output more readable. - -@item Object Code Formats -_GDBN__ uses a new library called the Binary File Descriptor (BFD) -Library to permit it to switch dynamically, without reconfiguration or -recompilation, between different object-file formats. Formats currently -supported are COFF, a.out, and the Intel 960 b.out; files may be read as -.o's, archive libraries, or core dumps. BFD is available as a -subroutine library so that other programs may take advantage of it, and -the other GNU binary utilities are being converted to use it. - -@item Configuration and Ports -Compile-time configuration (to select a particular architecture and -operating system) is much easier. The script @code{configure} now -allows you to configure _GDBN__ as either a native debugger or a -cross-debugger. @xref{Installing _GDBN__} for details on how to -configure and on what architectures are now available. - -@item Interaction -The user interface to _GDBN__'s control variables has been simplified -and consolidated in two commands, @code{set} and @code{show}. Output -lines are now broken at readable places, rather than overflowing onto -the next line. You can suppress output of machine-level addresses, -displaying only source language information. - - -@item C++ -_GDBN__ now supports C++ multiple inheritance (if used with a GCC -version 2 compiler), and also has limited support for C++ exception -handling, with the commands @code{catch} and @code{info catch}: _GDBN__ -can break when an exception is raised, before the stack is peeled back -to the exception handler's context. - -@item Modula-2 -_GDBN__ now has preliminary support for the GNU Modula-2 compiler, -currently under development at the State University of New York at -Buffalo. Coordinated development of both _GDBN__ and the GNU Modula-2 -compiler will continue through the fall of 1991 and into 1992. Other -Modula-2 compilers are currently not supported, and attempting to debug -programs compiled with them will likely result in an error as the symbol -table of the executable is read in. - -@item Command Rationalization -Many _GDBN__ commands have been renamed to make them easier to remember -and use. In particular, the subcommands of @code{info} and -@code{show}/@code{set} are grouped to make the former refer to the state -of your program, and the latter refer to the state of _GDBN__ itself. -@xref{Renamed Commands}, for details on what commands were renamed. - -@item Shared Libraries -_GDBN__ _GDB_VN__ can debug programs and core files that use SunOS shared -libraries. - -@item Reference Card -_GDBN__ _GDB_VN__ has a reference card; @xref{Formatting Documentation} for -instructions on printing it. - -@item Work in Progress -Kernel debugging for BSD and Mach systems; Tahoe and HPPA architecture -support. - -@end table - -@node Sample Session, Invocation, New Features, Top -@chapter A Sample _GDBN__ Session - -You can use this manual at your leisure to read all about _GDBN__. -However, a handful of commands are enough to get started using the -debugger. This chapter illustrates these commands. - -@iftex -In this sample session, we emphasize user input like this: @i{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. -_0__ -One of the preliminary versions of 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's -definition in 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} builtin @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 -$ @i{cd gnu/m4} -$ @i{./m4} -@i{define(foo,0000)} - -@i{foo} -0000 -@i{define(bar,defn(`foo'))} - -@i{bar} -0000 -@i{changequote(<QUOTE>,<UNQUOTE>)} - -@i{define(baz,defn(<QUOTE>foo<UNQUOTE>))} -@i{baz} -@i{C-d} -m4: End of input: 0: fatal error: EOF in string -@end smallexample - -@noindent -Let's use _GDBN__ to try to see what's going on. - -@smallexample -$ @i{_GDBP__ m4} -GDB is free software and you are welcome to distribute copies of it - under certain conditions; type "info copying" to see the conditions. -There is absolutely no warranty for GDB; type "info warranty" for details. -GDB _GDB_VN__, Copyright 1991 Free Software Foundation, Inc... -(_GDBP__) -@end smallexample - -@noindent -_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 -then tell _GDBN__ to use a narrower display width than usual, so -that examples will fit in this manual. - -@smallexample -(_GDBP__) @i{set width 70} -@end smallexample - -@noindent -Let's see how the @code{m4} builtin @code{changequote} works. -Having looked at the source, we know the relevant subroutine is -@code{m4_changequote}, so we set a breakpoint there with _GDBN__'s -@code{break} command. - -@smallexample -(_GDBP__) @i{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 _GDBN__ -control; as long as control does not reach the @code{m4_changequote} -subroutine, the program runs as usual: - -@smallexample -(_GDBP__) @i{run} -Starting program: /work/Editorial/gdb/gnu/m4/m4 -@i{define(foo,0000)} - -@i{foo} -0000 -@end smallexample - -@noindent -To trigger the breakpoint, we call @code{changequote}. _GDBN__ -suspends execution of @code{m4}, displaying information about the -context where it stops. - -@smallexample -@i{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 -(_GDBP__) @i{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 -(_GDBP__) @i{s} -set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -530 if (lquote != def_lquote) -@end smallexample - -@noindent -The summary display showing the subroutine where @code{m4} is now -suspended (and its arguments) is called a stack frame display. We can -use the @code{backtrace} command (which can also be spelled @code{bt}), -to see where we are in the stack: it displays a stack frame for each -active subroutine. - -@smallexample -(_GDBP__) @i{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 -Let's 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 -(_GDBP__) @i{s} -0x3b5c 532 if (rquote != def_rquote) -(_GDBP__) @i{s} -0x3b80 535 lquote = (lq == nil || *lq == '\0') ? def_lquote :\ - xstrdup(lq); -(_GDBP__) @i{n} -536 rquote = (rq == nil || *rq == '\0') ? def_rquote : xstrdup\ -(rq); -(_GDBP__) @i{n} -538 len_lquote = strlen(rquote); -@end smallexample - -@noindent -The last line displayed looks a little odd; let's examine the variables -@code{lquote} and @code{rquote} to see if they are in fact the new left -and right quotes we specified. We can use the command @code{p} -(@code{print}) to see their values. - -@smallexample -(_GDBP__) @i{p lquote} -$1 = 0x35d40 "<QUOTE>" -(_GDBP__) @i{p rquote} -$2 = 0x35d50 "<UNQUOTE>" -@end smallexample - -@noindent -@code{lquote} and @code{rquote} are indeed the new left and right quotes. -Let's look at some context; we can display ten lines of source -surrounding the current line, with the @code{l} (@code{list}) command. - -@smallexample -(_GDBP__) @i{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's step past the two lines that set @code{len_lquote} and -@code{len_rquote}, and then examine the values of those variables. - -@smallexample -(_GDBP__) @i{n} -539 len_rquote = strlen(lquote); -(_GDBP__) @i{n} -540 @} -(_GDBP__) @i{p len_lquote} -$3 = 9 -(_GDBP__) @i{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. Let's try setting them to better values. -We can use the @code{p} command for this, since it'll print the value of -any expression---and that expression can include subroutine calls and -assignments. - -@smallexample -(_GDBP__) p len_lquote=strlen(lquote) -$5 = 7 -(_GDBP__) p len_rquote=strlen(rquote) -$6 = 9 -@end smallexample - -@noindent -Let's see if that fixes 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 -(_GDBP__) @i{c} -Continuing. - -@i{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'll let @code{m4} exit by giving it an EOF as input. - -@smallexample -@i{C-d} -Program exited normally. -@end smallexample - -@noindent -The message @samp{Program exited normally.} is from _GDBN__; it -indicates @code{m4} has finished executing. We can end our _GDBN__ -session with the _GDBN__ @code{quit} command. - -@smallexample -(_GDBP__) @i{quit} -_1__@end smallexample - -@node Invocation, Commands, Sample Session, Top -@chapter Getting In and Out of _GDBN__ - -@menu -* Starting _GDBN__:: Starting _GDBN__ -* Leaving _GDBN__:: Leaving _GDBN__ -* Shell Commands:: Shell Commands -@end menu - -@node Starting _GDBN__, Leaving _GDBN__, Invocation, Invocation -@section Starting _GDBN__ - -_GDBN__ is invoked with the shell command @code{_GDBP__}. Once started, -it reads commands from the terminal until you tell it to exit. - -You can run @code{_GDBP__} with no arguments or options; but the most -usual way to start _GDBN__ is with one argument or two, specifying an -executable program as the argument: -@example -_GDBP__ program -@end example -@noindent -You can also start with both an executable program and a core file specified: -@example -_GDBP__ program core -@end example - -You can, instead, specify a process ID as a second argument, if you want -to debug a running process: -@example -_GDBP__ program 1234 -@end example -@noindent -would attach _GDBN__ to process @code{1234} (unless you also have a file -named @file{1234}; _GDBN__ does check for a core file first). - -@noindent -You can further control how _GDBN__ starts up by using command-line -options. _GDBN__ itself can remind you of the options available: -@example -_GDBP__ -help -@end example -@noindent -will display all available options and briefly describe their use -(@samp{_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 -_if__(!_GENERIC__) -_include__(gdbinv-m.m4)_dnl__ -_fi__(!_GENERIC__) -@end menu - -@node File Options, Mode Options, Starting _GDBN__, Starting _GDBN__ -@subsection Choosing Files - -As shown above, any arguments other than options specify an executable -file and core file; that is, the first argument encountered with no -associated option flag is equivalent to a @samp{-se} option, and the -second, if any, is equivalent to a @samp{-c} option. Many options have -both long and short forms; both are shown here. The long forms are also -recognized 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.) - -@table @code -@item -symbols=@var{file} -@itemx -s @var{file} -Read symbol table from file @var{file}. - -@item -exec=@var{file} -@itemx -e @var{file} -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} -Read symbol table from file @var{file} and use it as the executable -file. - -@item -core=@var{file} -@itemx -c @var{file} -Use file @var{file} as a core dump to examine. - -@item -command=@var{file} -@itemx -x @var{file} -Execute _GDBN__ commands from file @var{file}. @xref{Command Files}. - -@item -directory=@var{directory} -@itemx -d @var{directory} -Add @var{directory} to the path to search for source files. -@end table - -_if__(!_GENERIC__) -@node Mode Options, Mode Options, File Options, Starting _GDBN__ -_fi__(!_GENERIC__) -_if__(_GENERIC__) -@node Mode Options, , File Options, Starting _GDBN__ -_fi__(_GENERIC__) -@subsection Choosing Modes - -@table @code -@item -nx -@itemx -n -Do not execute commands from any @file{_GDBINIT__} initialization files. -Normally, the commands in these files are executed after all the -command options and arguments have been processed. -@xref{Command Files}. - -@item -quiet -@itemx -q -``Quiet''. Do not print the introductory and copyright messages. These -messages are also suppressed in batch mode. - -@item -batch -Run in batch mode. Exit with status @code{0} after processing all the command -files specified with @samp{-x} (and @file{_GDBINIT__}, if not inhibited). -Exit with nonzero status if an error occurs in executing the _GDBN__ -commands in the command files. - -Batch mode may be useful for running _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 _GDBN__ control -terminates) is not issued when running in batch mode. - -@item -cd=@var{directory} -Run _GDBN__ using @var{directory} as its working directory, -instead of the current directory. - -@item -fullname -@itemx -f -Emacs sets this option when it runs _GDBN__ as a subprocess. It tells _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 the 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-_GDBN__ interface program uses the two @samp{\032} characters as -a signal to display the source code for the frame. - -@item -b @var{bps} -Set the line speed (baud rate or bits per second) of any serial -interface used by _GDBN__ for remote debugging. - -@item -tty=@var{device} -Run using @var{device} for your program's standard input and output. -@c FIXME: kingdon thinks there's more to -tty. Investigate. -@end table - -_if__(!_GENERIC__) -_include__(gdbinv-s.m4) -_fi__(!_GENERIC__) - -@node Leaving _GDBN__, Shell Commands, Starting _GDBN__, Invocation -@section Leaving _GDBN__ -@cindex exiting _GDBN__ -@table @code -@item quit -@kindex quit -@kindex q -To exit _GDBN__, use the @code{quit} command (abbreviated @code{q}), or type -an end-of-file character (usually @kbd{C-d}). -@end table - -@cindex interrupt -An interrupt (often @kbd{C-c}) will not exit from _GDBN__, but rather -will terminate the action of any _GDBN__ command that is in progress and -return to _GDBN__ command level. It is safe to type the interrupt -character at any time because _GDBN__ does not allow it to take effect -until a time when it is safe. - -If you've been using _GDBN__ to control an attached process or device, -you can release it with the @code{detach} command; @pxref{Attach}. - -@node Shell Commands, , Leaving _GDBN__, Invocation -@section Shell Commands -If you need to execute occasional shell commands during your -debugging session, there's no need to leave or suspend _GDBN__; you can -just use the @code{shell} command. - -@table @code -@item shell @var{command string} -@kindex shell -@cindex shell escape -Directs _GDBN__ to invoke an inferior shell to execute @var{command -string}. If it exists, the environment variable @code{SHELL} is used -for the name of the shell to run. Otherwise _GDBN__ uses -@code{/bin/sh}. -@end table - -The utility @code{make} is often needed in development environments. -You don't have to use the @code{shell} command for this purpose in _GDBN__: - -@table @code -@item make @var{make-args} -@kindex make -@cindex calling make -Causes _GDBN__ to execute an inferior @code{make} program with the specified -arguments. This is equivalent to @samp{shell make @var{make-args}}. -@end table - -@node Commands, Running, Invocation, Top -@chapter _GDBN__ Commands - -@menu -* Command Syntax:: Command Syntax -* Help:: Getting Help -@end menu - -@node Command Syntax, Help, Commands, Commands -@section Command Syntax -A _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 command names do not allow any arguments. - -@cindex abbreviation -_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 -A blank line as input to _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 for which 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. - -_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}). Since it's easy to press one @key{RET} too many -in this situation, _GDBN__ disables command repetition after any command -that generates this sort of display. - -@kindex # -@cindex comment -A line of input starting with @kbd{#} is a comment; it does nothing. -This is useful mainly in command files (@xref{Command Files}). - -@node Help, , Command Syntax, Commands -@section Getting Help -@cindex online documentation -@kindex help -You can always ask _GDBN__ itself for information on its commands, using the -command @code{help}. - -@table @code -@item help -@itemx h -@kindex h -You can use @code{help} (abbreviated @code{h}) with no arguments to -display a short list of named classes of commands: -@smallexample -(_GDBP__) help -List of classes of commands: - -running -- Running the program -stack -- Examining the stack -data -- Examining data -breakpoints -- Making program stop at certain points -files -- Specifying and examining files -status -- Status inquiries -support -- Support facilities -user-defined -- User-defined commands -aliases -- Aliases of other commands -obscure -- Obscure features - -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. -(_GDBP__) -@end smallexample - -@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 -(_GDBP__) help status -Status inquiries. - -List of commands: - -show -- Generic command for showing things set with "set" -info -- Generic command for printing status - -Type "help" followed by command name for full documentation. -Command name abbreviations are allowed if unambiguous. -(_GDBP__) -@end smallexample - -@item help @var{command} -With a command name as @code{help} argument, _GDBN__ will display a -short paragraph on how to use that command. -@end table - -In addition to @code{help}, you can use the _GDBN__ commands @code{info} -and @code{show} to inquire about the state of your program, or the state -of _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. -@c FIXME: @pxref{Index} used to be here, but even though it shows up in -@c FIXME...the 'aux' file with a pageno the xref can't find it. - -@c @group -@table @code -@item info -@kindex info -@kindex i -This command (abbreviated @code{i}) is for describing the state of your -program; for example, it can list the arguments given to your program -(@code{info args}), the registers currently in use (@code{info -registers}), or the breakpoints you've set (@code{info breakpoints}). -You can get a complete list of the @code{info} sub-commands with -@w{@code{help info}}. - -@kindex show -@item show -In contrast, @code{show} is for describing the state of _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 _GDBN__ is running. You should include this -information in _GDBN__ bug-reports. If multiple versions of _GDBN__ are -in use at your site, you may occasionally want to make sure what version -of _GDBN__ you're running; as _GDBN__ evolves, new commands are -introduced, and old ones may wither away. The version number is also -announced when you start _GDBN__ with no arguments. - -@kindex show copying -@item show copying -Display information about permission for copying _GDBN__. - -@kindex show warranty -@item show warranty -Display the GNU ``NO WARRANTY'' statement. -@end table - -@node Running, Stopping, Commands, Top -@chapter Running Programs Under _GDBN__ - -@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 -@end menu - -@node Compilation, Starting, Running, Running -@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. - -The 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 the program is -correct, but there's no sense in pushing your luck. - -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 as a bug (including a test case!). - -Older versions of the GNU C compiler permitted a variant option -@samp{-gg} for debugging information. _GDBN__ no longer supports this -format; if your GNU C compiler has this option, do not use it. - -@ignore -@comment As far as I know, there are no cases in which _GDBN__ will -@comment produce strange output in this case. (but no promises). -If your program includes archives made with the @code{ar} program, and -if the object files used as input to @code{ar} were compiled without the -@samp{-g} option and have names longer than 15 characters, _GDBN__ will get -confused reading the program's symbol table. No error message will be -given, but _GDBN__ may behave strangely. The reason for this problem is a -deficiency in the Unix archive file format, which cannot represent file -names longer than 15 characters. - -To avoid this problem, compile the archive members with the @samp{-g} -option or use shorter file names. Alternatively, use a version of GNU -@code{ar} dated more recently than August 1989. -@end ignore - - -@node Starting, Arguments, Compilation, Running -@section Starting your Program -@cindex starting -@cindex running -@table @code -@item run -@itemx r -@kindex run -Use the @code{run} command to start your program under _GDBN__. You -must first specify the program name -_if__(_VXWORKS__) -(except on VxWorks) -_fi__(_VXWORKS__) -with an argument to _GDBN__ -(@pxref{Invocation}), or using the @code{file} or @code{exec-file} -command (@pxref{Files}). -@refill -@end table - -On targets that support processes, @code{run} creates an inferior -process and makes that process run your program. On other targets, -@code{run} jumps to the start of the program. - -The execution of a program is affected by certain information it -receives from its superior. _GDBN__ provides ways to specify this -information, which you must do @i{before} starting the program. (You -can change it after starting the program, but such changes will only affect -the program the next time you start it.) This information may be -divided into four categories: - -@table @asis -@item The @i{arguments.} -You 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}.@refill - -@item The @i{environment.} -Your program normally inherits its environment from _GDBN__, but you can -use the _GDBN__ commands @code{set environment} and @code{unset -environment} to change parts of the environment that will be given to -the program. @xref{Environment}.@refill - -@item The @i{working directory.} -Your program inherits its working directory from _GDBN__. You can set -_GDBN__'s working directory with the @code{cd} command in _GDBN__. -@xref{Working Directory}. - -@item The @i{standard input and output.} -Your program normally uses the same device for standard input and -standard output as _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}. - -@cindex pipes -@emph{Warning:} While input and output redirection work, you can't use -pipes to pass the output of the program you're debugging to another -program; if you attempt this, _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}, for discussion of how to arrange for your -program to stop. Once your program has been started by the @code{run} -command (and then stopped), you may evaluate expressions that involve -calls to functions in the inferior, using the @code{print} or -@code{call} commands. @xref{Data}. - -If the modification time of your symbol file has changed since the last -time _GDBN__ read its symbols, _GDBN__ will discard its symbol table and re-read -it. In this process, it tries to retain your current breakpoints. - -@node Arguments, Environment, Starting, Running -@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 the program. -_GDBN__ uses the shell indicated by your environment variable -@code{SHELL} if it exists; otherwise, _GDBN__ uses @code{/bin/sh}. - -@code{run} with no arguments uses the same arguments used by the previous -@code{run}, or those set by the @code{set args} command. - -@kindex set args -@table @code -@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} will execute 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. - -@item show args -@kindex show args -Show the arguments to give your program when it is started. -@end table - -@node Environment, Working Directory, Arguments, Running -@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 the program with a modified -environment without having to start _GDBN__ over again. - -@table @code -@item path @var{directory} -@kindex path -Add @var{directory} to the front of the @code{PATH} environment variable -(the search path for executables), for both _GDBN__ and your program. -You may specify several directory names, separated by @samp{:} or -whitespace. If @var{directory} is already in the path, it is moved to -the front, so it will be searched sooner. - -You can use the string @samp{$cwd} to refer to whatever is the current -working directory at the time _GDBN__ searches the path. If you use -@samp{.} instead, it refers to the directory where you executed the -@code{path} command. _GDBN__ fills in the current path where needed in -the @var{directory} argument, before adding it to the search path. -@c 'path' is explicitly nonrepeatable, but RMS points out it's silly to -@c document that, since repeating it would be a no-op. - -@item show paths -@kindex show paths -Display the list of search paths for executables (the @code{PATH} -environment variable). - -@item show environment @r{[}@var{varname}@r{]} -@kindex show environment -Print the value of environment variable @var{varname} to be given to -your program when it starts. If you don't 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}. - -@item set environment @var{varname} @r{[}=@r{]} @var{value} -@kindex set environment -Sets environment variable @var{varname} to @var{value}. The value -changes for your program only, not for _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 doesn't include leading, trailing -@c blanks. Gnu asks: does anyone care? - -For example, this command: - -@example -set env USER = foo -@end example - -@noindent -tells a Unix 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.) - -@item unset environment @var{varname} -@kindex unset environment -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 - -@node Working Directory, Input/Output, Environment, Running -@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 _GDBN__. _GDBN__'s -working directory is initially whatever it inherited from its parent -process (typically the shell), but you can specify a new working -directory in _GDBN__ with the @code{cd} command. - -The _GDBN__ working directory also serves as a default for the commands -that specify files for _GDBN__ to operate on. @xref{Files}. - -@table @code -@item cd @var{directory} -@kindex cd -Set _GDBN__'s working directory to @var{directory}. - -@item pwd -@kindex pwd -Print _GDBN__'s working directory. -@end table - -@node Input/Output, Attach, Working Directory, Running -@section Your Program's Input and Output - -@cindex redirection -@cindex i/o -@cindex terminal -By default, the program you run under _GDBN__ does input and output to -the same terminal that _GDBN__ uses. _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 -@item info terminal -@kindex info terminal -Displays _GDBN__'s recorded information about the terminal modes your -program is using. -@end table - -You can redirect the program's input and/or output using shell -redirection with the @code{run} command. For example, - -_0__@example -run > outfile -_1__@end example - -@noindent -starts the program, diverting its output to the file @file{outfile}. - -@kindex tty -@cindex controlling terminal -Another way to specify where the 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 _GDBN__ still comes from your terminal. - -@node Attach, Kill Process, Input/Output, Running -@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 _GDBN__. -(@code{info files} will show 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} will not repeat if you press @key{RET} a second time after -executing the command. -@end table - -To use @code{attach}, you must be debugging in an environment which -supports processes. You must also have permission to send the process a -signal, and it must have the same effective user ID as the _GDBN__ -process. - -When using @code{attach}, you should first use the @code{file} command -to specify the program running in the process and load its symbol table. -@xref{Files}. - -The first thing _GDBN__ does after arranging to debug the specified -process is to stop it. You can examine and modify an attached process -with all the _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 _GDBN__ to the process. - -@table @code -@item detach -@kindex detach -When you have finished debugging the attached process, you can use the -@code{detach} command to release it from _GDBN__'s control. Detaching -the process continues its execution. After the @code{detach} command, -that process and _GDBN__ become completely independent once more, and you -are ready to @code{attach} another process or start one with @code{run}. -@code{detach} will not repeat if you press @key{RET} again after -executing the command. -@end table - -If you exit _GDBN__ or use the @code{run} command while you have an attached -process, you kill that process. By default, you will be asked 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}). - -@node Kill Process, , Attach, Running -@c @group -@section Killing the Child Process - -@table @code -@item kill -@kindex kill -Kill the child process in which your program is running under _GDBN__. -@end table - -This command is useful if you wish to debug a core dump instead of a -running process. _GDBN__ ignores any core dump file while your program -is running. -@c @end group - -On some operating systems, a program can't be executed outside _GDBN__ -while you have breakpoints set on it inside _GDBN__. You can use the -@code{kill} command in this situation to permit running the program -outside the debugger. - -The @code{kill} command is also useful if you wish to recompile and -relink the 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}, _GDBN__ will notice that the file has changed, and -will re-read the symbol table (while trying to preserve your current -breakpoint settings). - -@node Stopping, Stack, Running, Top -@chapter Stopping and Continuing - -The principal purpose of using a debugger is so that you can stop your -program before it terminates; or so that, if the program runs into -trouble, you can investigate and find out why. - -Inside _GDBN__, your program may stop for any of several reasons, such -as a signal, a breakpoint, or reaching a new line after a _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 _GDBN__ provide ample -explanation of the status of your program---but you can also explicitly -request this information at any time. - -@table @code -@item info program -@kindex 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 Exceptions -* Continuing and Stepping:: Resuming Execution -* Signals:: Signals -@end menu - -@node Breakpoints, Continuing and Stepping, Stopping, Stopping -@section Breakpoints, Watchpoints, and Exceptions - -@cindex breakpoints -A @dfn{breakpoint} makes your program stop whenever a certain point in -the program is reached. For each breakpoint, you can add various -conditions to control in finer detail whether the program will stop. -You can set breakpoints with the @code{break} command and its variants -(@pxref{Set Breaks}), to specify the place where the program should stop -by line number, function name or exact address in the program. In -languages with exception handling (such as GNU C++), you can also set -breakpoints where an exception is raised (@pxref{Exception Handling}). - -@cindex watchpoints -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}), 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. - -Each breakpoint or watchpoint is assigned a number when it is created; -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 the program until you enable it again. - -@menu -* Set Breaks:: Setting Breakpoints -* Set Watchpoints:: Setting Watchpoints -* Exception Handling:: Breakpoints and Exceptions -* Delete Breaks:: Deleting Breakpoints -* Disabling:: Disabling Breakpoints -* Conditions:: Break Conditions -* Break Commands:: Breakpoint Command Lists -* Breakpoint Menus:: Breakpoint Menus -* Error in Breakpoints:: -@end menu - -@node Set Breaks, Set Watchpoints, Breakpoints, Breakpoints -@subsection Setting Breakpoints - -@kindex break -@kindex b -Breakpoints are set with the @code{break} command (abbreviated @code{b}). - -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++, -@var{function} may refer to more than one possible place to break. -@xref{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 frame. - -@item break @var{linenum} -Set a breakpoint at line @var{linenum} in the current source file. -That file is the last file whose source text was printed. This -breakpoint will stop the 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 the 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}). In any selected frame but the innermost, this will -cause the program to 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} doesn't leave an -active breakpoint. If you use @code{break} without an argument in the -innermost frame, _GDBN__ will stop the next time it reaches the current -location; this may be useful inside loops. - -_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 the 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}, for more -information on breakpoint conditions. - -@item tbreak @var{args} -@kindex tbreak -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 disabled the first time it -is hit. @xref{Disabling}. - -@item rbreak @var{regex} -@kindex rbreak -@cindex regular expression -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. They can -be deleted, disabled, made conditional, etc., in the standard ways. - -When debugging C++ programs, @code{rbreak} is useful for setting -breakpoints on overloaded functions that are not members of any special -classes. - -@kindex info breakpoints -@cindex @code{$_} and @code{info breakpoints} -@item info breakpoints @r{[}@var{n}@r{]} -@item info break @r{[}@var{n}@r{]} -Print a list of all breakpoints (but not watchpoints) set and not -deleted, showing their numbers, where in the program they are, and any -special features in use for them. Disabled breakpoints are included in -the list, but marked as disabled. @code{info break} with a breakpoint -number @var{n} as argument lists only that breakpoint. The convenience -variable @code{$_} and the default examining-address for the @code{x} -command are set to the address of the last breakpoint listed -(@pxref{Memory}). The equivalent command for watchpoints is @code{info -watch}. @end table - -_GDBN__ allows you to set any number of breakpoints at the same place in the -program. There is nothing silly or meaningless about this. When the -breakpoints are conditional, this is even useful (@pxref{Conditions}). - -@node Set Watchpoints, Exception Handling, Set Breaks, Breakpoints -@subsection Setting Watchpoints -@cindex setting 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. - -Watchpoints currently execute two orders of magnitude more slowly than -other breakpoints, but this can well be worth it to catch errors where -you have no clue what part of your program is the culprit. Some -processors provide special hardware to support watchpoint evaluation; future -releases of _GDBN__ will use such hardware if it is available. - -@table @code -@kindex watch -@item watch @var{expr} -Set a watchpoint for an expression. - -@kindex info watchpoints -@item info watchpoints -This command prints a list of watchpoints; it is otherwise similar to -@code{info break}. -@end table - -@node Exception Handling, Delete Breaks, Set Watchpoints, Breakpoints -@subsection Breakpoints and Exceptions -@cindex exception handlers - -Some languages, such as GNU C++, implement exception handling. You can -use _GDBN__ to examine what caused the program to raise an exception, -and to list the exceptions the program is prepared to handle at a -given point in time. - -@table @code -@item catch @var{exceptions} -@kindex catch -You can set breakpoints at active exception handlers by using the -@code{catch} command. @var{exceptions} is a list of names of exceptions -to catch. -@end table - -You can use @code{info catch} to list active exception handlers; -@pxref{Frame Info}. - -There are currently some limitations to exception handling in _GDBN__. -These will be corrected in a future release. - -@itemize @bullet -@item -If you call a function interactively, _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 the user and cause the program to simply continue -running until it hits a breakpoint, catches a signal that _GDBN__ is -listening for, or exits. -@item -You cannot raise an exception interactively. -@item -You cannot interactively install an exception handler. -@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's 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 GNU C++, 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. - ID is the exception identifier. */ - void __raise_exception (void **@var{addr}, void *@var{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}). - -With a conditional breakpoint (@xref{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 the -program when any of a number of exceptions are raised. - -@node Delete Breaks, Disabling, Exception Handling, Breakpoints -@subsection Deleting Breakpoints - -@cindex clearing breakpoints, watchpoints -@cindex deleting breakpoints, watchpoints -It is often necessary to eliminate a breakpoint or watchpoint once it -has done its job and you no longer want the 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 the program. With the @code{delete} command you can -delete individual breakpoints or watchpoints by specifying their -breakpoint numbers. - -It is not necessary to delete a breakpoint to proceed past it. _GDBN__ -automatically ignores breakpoints on the first instruction to be executed -when you continue execution without changing the execution address. - -@table @code -@item clear -@kindex clear -Delete any breakpoints at the next instruction to be executed in the -selected stack frame (@pxref{Selection}). When the innermost frame -is selected, this is a good way to delete a breakpoint that the program -just stopped at. - -@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. - -@item delete @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} -@cindex delete breakpoints -@kindex delete -@kindex d -Delete the breakpoints or watchpoints of the numbers specified as -arguments. If no argument is specified, delete all breakpoints (_GDBN__ -asks confirmation, unless you've @code{set confirm off}). You -can abbreviate this command as @code{d}. -@end table - -@node Disabling, Conditions, Delete Breaks, Breakpoints -@subsection Disabling Breakpoints - -@cindex disabled breakpoints -@cindex enabled breakpoints -Rather than deleting a breakpoint or watchpoint, 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 and watchpoints 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 or watchpoints if you -don't know which numbers to use. - -A breakpoint or watchpoint can have any of four different states of -enablement: - -@itemize @bullet -@item -Enabled. The breakpoint will stop the program. A breakpoint set -with the @code{break} command starts out in this state. -@item -Disabled. The breakpoint has no effect on the program. -@item -Enabled once. The breakpoint will stop the program, but -when it does so it will become disabled. A breakpoint set -with the @code{tbreak} command starts out in this state. -@item -Enabled for deletion. The breakpoint will stop the program, but -immediately after it does so it will be deleted permanently. -@end itemize - -You can use the following commands to enable or disable breakpoints and -watchpoints: - -@table @code -@item disable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} -@kindex disable breakpoints -@kindex disable -@kindex dis -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}. - -@item enable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]} -@kindex enable breakpoints -@kindex enable -Enable the specified breakpoints (or all defined breakpoints). They -become effective once again in stopping the program. - -@item enable @r{[}breakpoints@r{]} once @var{bnums}@dots{} -Enable the specified breakpoints temporarily. Each will be disabled -again the next time it stops the program. - -@item enable @r{[}breakpoints@r{]} delete @var{bnums}@dots{} -Enable the specified breakpoints to work once and then die. Each of -the breakpoints will be deleted the next time it stops the program. -@end table - -Save for a breakpoint set with @code{tbreak} (@pxref{Set Breaks}), -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 -will not change the state of your other breakpoints; -@pxref{Continuing and Stepping}.) - -@node Conditions, Break Commands, Disabling, Breakpoints -@subsection Break Conditions -@cindex conditional breakpoints -@cindex breakpoint conditions - -The simplest sort of breakpoint breaks every time the 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. (@xref{Expressions}). A breakpoint with a condition -evaluates the expression each time the program reaches it, and the -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 ca 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, _GDBN__ might see the other breakpoint first and stop the program -without checking the condition of this one.) Note that breakpoint -commands are usually more convenient and flexible for the purpose of -performing side effects when a breakpoint is reached -(@pxref{Break Commands}). - -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}. -They can also be changed at any time with the @code{condition} command. -The @code{watch} command doesn't recognize the @code{if} keyword; -@code{condition} is the only way to impose a further condition on a -watchpoint. - -@table @code -@item condition @var{bnum} @var{expression} -@kindex condition -Specify @var{expression} as the break condition for breakpoint or -watchpoint number @var{bnum}. From now on, this breakpoint will stop -the program only if the value of @var{expression} is true (nonzero, in -C). When you use @code{condition}, _GDBN__ checks @var{expression} -immediately for syntactic correctness, and to determine whether symbols -in it have referents in the context of your breakpoint. _GDBN__ does -not actually evaluate @var{expression} at the time the @code{condition} -command is given, however. @xref{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 the 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 will not stop the next @var{n} times it -is reached. - -@table @code -@item ignore @var{bnum} @var{count} -@kindex ignore -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 will not stop; other than to decrement the ignore count, _GDBN__ -takes no action. - -To make the breakpoint stop the next time it is reached, specify -a count of zero. - -@item continue @var{count} -@itemx c @var{count} -@itemx fg @var{count} -@kindex continue @var{count} -Continue execution of the program, setting the ignore count of the -breakpoint that the program stopped at to @var{count} minus one. -Thus, the program will not stop at this breakpoint until the -@var{count}'th time it is reached. - -An argument to this command is meaningful only when the program stopped -due to a breakpoint. At other times, the argument to @code{continue} is -ignored. - -The synonym @code{fg} is provided purely for convenience, and has -exactly the same behavior as other forms of the command. -@end table - -If a breakpoint has a positive ignore count and a condition, the condition -is not checked. Once the ignore count reaches zero, the condition will -be checked. - -You could achieve the effect of the ignore count with a -condition such as _0__@w{@samp{$foo-- <= 0}}_1__ using a debugger convenience -variable that is decremented each time. @xref{Convenience Vars}. - -@node Break Commands, Breakpoint Menus, Conditions, Breakpoints -@subsection Breakpoint Command Lists - -@cindex breakpoint commands -You can give any breakpoint (or watchpoint) a series of commands to -execute when the program stops due to that breakpoint. For example, you -might want to print the values of certain expressions, or enable other -breakpoints. - -@table @code -@item commands @r{[}@var{bnum}@r{]} -@itemx @dots{} @var{command-list} @dots{} -@itemx end -@kindex commands -@kindex 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} followed -immediately by @code{end}; that is, give no commands. - -With no @var{bnum} argument, @code{commands} refers to the last -breakpoint or watchpoint set (not to the breakpoint most recently -encountered). -@end table - -Pressing @key{RET} as a means of repeating the last _GDBN__ command is -disabled within a @var{command-list}. - -You can use breakpoint commands to start the program up again. Simply -use the @code{continue} command, or @code{step}, or any other command -that resumes execution. Subsequent commands in the command list are -ignored. - -@kindex silent -If the first command specified 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 the remaining commands too print nothing, you will see no sign that -the breakpoint was reached at all. @code{silent} is meaningful only -at the beginning of a breakpoint command list. - -The commands @code{echo} and @code{output} that allow you to print precisely -controlled output are often useful in silent breakpoints. @xref{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. - -_0__@example -break foo if x>0 -commands -silent -echo x is\040 -output x -echo \n -cont -end -_1__@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 the 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 - -@cindex lost output -One deficiency in the operation of automatically continuing breakpoints -under Unix appears when your program uses raw mode for the terminal. -_GDBN__ switches back to its own terminal modes (not raw) before executing -commands, and then must switch back to raw mode when your program is -continued. This causes any pending terminal input to be lost. -@c FIXME: revisit below when GNU sys avail. -@c In the GNU system, this will be fixed by changing the behavior of -@c terminal modes. - -Under Unix, you can get around this problem by writing actions into -the breakpoint condition rather than in commands. For example - -@example -condition 5 (x = y + 4), 0 -@end example - -@noindent -specifies a condition expression (@xref{Expressions}) that will change -@code{x} as needed, then always have the value zero so the program will -not stop. No input is lost here, because _GDBN__ evaluates break -conditions without changing the terminal modes. When you want to have -nontrivial conditions for performing the side effects, the operators -@samp{&&}, @samp{||} and @samp{?@dots{}:} may be useful. - -@node Breakpoint Menus, Error in Breakpoints, Break Commands, Breakpoints -@subsection Breakpoint Menus -@cindex overloading -@cindex symbol overloading - -Some programming languages (notably C++) 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 _GDBN__ where you -want a breakpoint. _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: - -@example -(_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. -(_GDBP__) -@end example - - -@node Error in Breakpoints, , Breakpoint Menus, Breakpoints -@subsection ``Cannot Insert Breakpoints'' - -@c FIXME: "cannot insert breakpoints" error, v unclear. -@c Q in pending mail to Gilmore. ---pesch@cygnus.com, 26mar91 -@c some light may be shed by looking at instances of -@c ONE_PROCESS_WRITETEXT. But error seems possible otherwise -@c too. pesch, 20sep91 -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 _GDBN__ -to stop the other process. - -When this happens, you have three ways to proceed: - -@enumerate -@item -Remove or disable the breakpoints, then continue. - -@item -Suspend _GDBN__, and copy the file containing the program to a new name. -Resume _GDBN__ and use the @code{exec-file} command to specify that _GDBN__ -should run the program under that name. Then start the program again. - -@c FIXME: RMS commented here "Show example". Maybe when someone -@c explains the first FIXME: in this section... - -@item -Relink the 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 - -@node Continuing and Stepping, Signals, Breakpoints, Stopping -@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 resuming program -execution for a very limited time: one line of source code, or one -machine instruction. Either when continuing or when stepping, the -program may stop even sooner, due to a breakpoint or to a signal. (If -due to a signal, you may want to use @code{handle}, or use @samp{signal -0} to resume execution; @pxref{Signals}.) - -@table @code -@item continue @r{[}@var{ignore-count}@r{]} -@kindex continue -Resume program execution, at the address where the 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}). - -To resume execution at a different place, you can use @code{return} -(@pxref{Returning}) to go back to the calling function; or @code{jump} -(@pxref{Jumping}) to go to an arbitrary location in your program. - -@end table - -A typical technique for using stepping is to set a breakpoint -(@pxref{Breakpoints}) at the beginning of the function or the section of -the program in which a problem is believed to lie, run the 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 -@item step -@kindex step -@kindex s -Continue running the program until control reaches a different source -line, then stop it and return control to _GDBN__. This command is -abbreviated @code{s}. - -@quotation -@emph{Warning:} If you use the @code{step} command while control is -within a function that was compiled without debugging information, -execution will proceed until control reaches another function. -@end quotation - -@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. - -@item next @r{[}@var{count}@r{]} -@kindex next -@kindex n -Continue to the next source line in the current (innermost) stack frame. -Similar to @code{step}, but any function calls appearing within the line -of code are executed without stopping. Execution stops when control -reaches a different line of code at the stack level which was executing -when the @code{next} command was given. This command is abbreviated -@code{n}. - -An argument @var{count} is a repeat count, as for @code{step}. - -@code{next} within a function that lacks debugging information acts like -@code{step}, but any function calls appearing within the code of the -function are executed without stopping. - -@item finish -@kindex 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}). - -@item until -@kindex until -@item u -@kindex 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} will cause the program to continue execution -until the loop is exited. In contrast, a @code{next} command at the end -of a loop will simply step back to the beginning of the loop, which -would force you to step through the next iteration. - -@code{until} always stops the 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 -(_GDBP__) f -#0 main (argc=4, argv=0xf7fffae8) at m4.c:206 -206 expand_input(); -(_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} -@item u @var{location} -Continue running the 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}). This form of the command uses breakpoints, and -hence is quicker than @code{until} without an argument. - -@item stepi -@itemx si -@kindex stepi -@kindex 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 will cause the next instruction to be executed to -be displayed automatically at each stop. @xref{Auto Display}. - -An argument is a repeat count, as in @code{step}. - -@item nexti -@itemx ni -@kindex nexti -@kindex 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, , Continuing and Stepping, Stopping -@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 (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 the program has -requested an alarm). - -@cindex fatal signals -Some signals, including @code{SIGALRM}, are a normal part of the -functioning of the program. Others, such as @code{SIGSEGV}, indicate -errors; these signals are @dfn{fatal} (kill the 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 the program, but it is normally -fatal so it can carry out the purpose of the interrupt: to kill the program. - -_GDBN__ has the ability to detect any occurrence of a signal in the program -running under _GDBN__'s control. You can tell _GDBN__ in advance what to do for -each kind of signal. - -@cindex handling signals -Normally, _GDBN__ is set up to ignore non-erroneous signals like @code{SIGALRM} -(so as not to interfere with their role in the functioning of the program) -but to stop the program immediately whenever an error signal happens. -You can change these settings with the @code{handle} command. - -@table @code -@item info signals -@kindex info signals -Print a table of all the kinds of signals and how _GDBN__ has been told to -handle each one. You can use this to see the signal numbers of all -the defined types of signals. - -@item handle @var{signal} @var{keywords}@dots{} -@kindex handle -Change the way _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). 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 -_GDBN__ should not stop the program when this signal happens. It may -still print a message telling you that the signal has come in. - -@item stop -_GDBN__ should stop the program when this signal happens. This implies -the @code{print} keyword as well. - -@item print -_GDBN__ should print a message when this signal happens. - -@item noprint -_GDBN__ should not mention the occurrence of the signal at all. This -implies the @code{nostop} keyword as well. - -@item pass -_GDBN__ should allow the program to see this signal; the program will be -able to handle the signal, or may be terminated if the signal is fatal -and not handled. - -@item nopass -_GDBN__ should not allow the program to see this signal. -@end table -@c @end group - -When a signal has been set to stop the program, the program cannot see the -signal until you continue. It will see the signal then, if @code{pass} is -in effect for the signal in question @i{at that time}. In other words, -after _GDBN__ reports a signal, you can use the @code{handle} command with -@code{pass} or @code{nopass} to control whether that signal will be seen by -the program when you later continue it. - -You can also use the @code{signal} command to prevent the 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 the 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 the program would probably terminate immediately as -a result of the fatal signal once it sees the signal. To prevent this, -you can continue with @samp{signal 0}. @xref{Signaling}. - -@node Stack, Source, Stopping, Top -@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, the information about -where in the program the call was made from is saved in a block of data -called a @dfn{stack frame}. The frame also contains the arguments of the -call and the local variables of the function that was called. All the -stack frames are allocated in a region of memory called the @dfn{call -stack}. - -When your program stops, the _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 _GDBN__ and many _GDBN__ commands -refer implicitly to the selected frame. In particular, whenever you ask -_GDBN__ for the value of a variable in the program, the value is found in the -selected frame. There are special _GDBN__ commands to select whichever frame -you are interested in. - -When the program stops, _GDBN__ automatically selects the currently executing -frame and describes it briefly as the @code{frame} command does -(@pxref{Frame Info}). - -@menu -* Frames:: Stack Frames -* Backtrace:: Backtraces -* Selection:: Selecting a Frame -* Frame Info:: Information on a Frame -@end menu - -@node Frames, Backtrace, Stack, Stack -@section Stack Frames - -@cindex frame -@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 of those bytes 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 -_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 _GDBN__ to give you a way of designating stack -frames in _GDBN__ commands. - -@cindex frameless execution -Some compilers allow functions to be compiled so that they operate -without stack frames. (For example, the @code{_GCC__} option -@samp{-fomit-frame-pointer} will generate functions without a frame.) -This is occasionally done with heavily used library functions to save -the frame setup time. _GDBN__ has limited facilities for dealing with -these function invocations. If the innermost function invocation has no -stack frame, _GDBN__ will nevertheless regard it as though it had a -separate frame, which is numbered zero as usual, allowing correct -tracing of the function call chain. However, _GDBN__ has no provision -for frameless functions elsewhere in the stack. - -@node Backtrace, Selection, Frames, Stack -@section Backtraces - -A backtrace is a summary of how the 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 -@item backtrace -@itemx bt -@kindex backtrace -@kindex 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 -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 doesn't begin with a program counter -value, indicating that the program has stopped at the beginning of the -code for line @code{993} of @code{builtin.c}. - -@node Selection, Frame Info, Backtrace, Stack -@section Selecting a Frame - -Most commands for examining the stack and other data in the 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 -@item frame @var{n} -@itemx f @var{n} -@kindex frame -@kindex f -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 @code{main}'s -frame. - -@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 _GDBN__ to assign numbers properly to all frames. In -addition, this can be useful when the program has multiple stacks and -switches between them. - -_if__(_SPARC__) -On the SPARC architecture, @code{frame} needs two addresses to -select an arbitrary frame: a frame pointer and a stack pointer. -@c note to future updaters: this is conditioned on a flag -@c FRAME_SPECIFICATION_DYADIC in the tm-*.h files, currently only used -@c by SPARC, hence the specific attribution. Generalize or list all -@c possibilities if more supported machines start doing this. -_fi__(_SPARC__) - -@item up @var{n} -@kindex up -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. - -@item down @var{n} -@kindex down -@kindex do -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. For -example: - -@smallexample -(_GDBP__) up -#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) at env.c:10 -10 read_input_file (argv[i]); -@end smallexample - -After such a printout, the @code{list} command with no arguments will print -ten lines centered on the point of execution in the frame. @xref{List}. - -@table @code -@item up-silently @var{n} -@itemx down-silently @var{n} -@kindex down-silently -@kindex up-silently -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 _GDBN__ command scripts, where the output might be unnecessary and -distracting. - -@end table - -@node Frame Info, , Selection, Stack -@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 (@pxref{Selection}). - -@item info frame -@kindex info frame -@itemx info f -@kindex info f -This command prints a verbose description of the selected stack frame, -including the address of the frame, the addresses of the next frame down -(called by this frame) and the next frame up (caller of this frame), the -language that the source code corresponding to this frame was written in, -the address of the frame's arguments, the program counter saved in it -(the address of execution in the caller frame), and which registers -were saved in the frame. 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. - -@item info args -@kindex 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 static or automatic within all -program blocks that execution in this frame is currently inside of. - -@item info catch -@kindex info catch -@cindex catch exceptions -@cindex exception handlers -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{Exception Handling}. -@end table - -@node Source, Data, Stack, Top -@chapter Examining Source Files - -_GDBN__ can print parts of your program's source, since the debugging -information recorded in your program tells _GDBN__ what source files -were used to built it. When your program stops, _GDBN__ spontaneously -prints the line where it stopped. Likewise, when you select a stack -frame (@pxref{Selection}), _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 _GDBN__ through its GNU Emacs interface, you may prefer to -use Emacs facilities to view source; @pxref{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, Search, Source, Source -@section Printing Source Lines - -@kindex list -@kindex l -To print lines from a source file, use the @code{list} command -(abbreviated @code{l}). 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}), this prints -lines centered around that line. - -@item list - -Print lines just before the lines last printed. -@end table - -By default, _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 -@item set listsize @var{count} -@kindex set listsize -Make the @code{list} command display @var{count} source lines (unless -the @code{list} argument explicitly specifies some other number). - -@item show listsize -@kindex show listsize -Display the number of lines that @code{list} will currently display by -default. -@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} -@c FIXME: "of the open-brace" is C-centric. When we add other langs... -Specifies the line of the open-brace that begins the body of the -function @var{function}. - -@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, Source Path, List, Source -@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 -@item forward-search @var{regexp} -@itemx search @var{regexp} -@kindex search -@kindex forward-search -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 abbreviate the command name -as @code{fo}. The synonym @samp{search @var{regexp}} is also supported. - -@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, Machine Code, Search, Source -@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. _GDBN__ has a list of directories to search for source files; -this is called the @dfn{source path}. Each time _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 _GDBN__ can't find a source file in the source path, and the object -program records a directory, _GDBN__ tries that directory too. If the -source path is empty, and there is no record of the compilation -directory, _GDBN__ will, as a last resort, look in the current -directory. - -Whenever you reset or rearrange the source path, _GDBN__ will clear out -any information it has cached about where source files are found, where -each line is in the file, etc. - -@kindex directory -When you start _GDBN__, its source path is empty. -To add other directories, use the @code{directory} command. - -@table @code -@item directory @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{:} or -whitespace. You may specify a directory that is already in the source -path; this moves it forward, so it will be searched sooner. - -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 _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 don't 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, _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, , Source Path, Source -@section Source and Machine Code -You can use the command @code{info line} to map source lines to program -addresses (and viceversa), and the command @code{disassemble} to display -a range of addresses as machine instructions. - -@table @code -@item info line @var{linespec} -@kindex info line -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}). -@end table - -For example, we can use @code{info line} to inquire on where the object -code for the first line of function @code{m4_changequote} lies: -@smallexample -(_GDBP__) info line m4_changecom -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 -(_GDBP__) info line *0x63ff -Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. -@end smallexample - -@cindex @code{$_} and @code{info line} -After @code{info line}, the default address for the @code{x} -command is changed to the starting address of the line, so that -@samp{x/i} is sufficient to begin examining the machine code -(@pxref{Memory}). Also, this address is saved as the value of the -convenience variable @code{$_} (@pxref{Convenience Vars}). - -@table @code -@kindex disassemble -@item disassemble -This specialized command is provided to dump 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; the function -surrounding this value will be dumped. Two arguments (separated by one -or more spaces) specify a range of addresses (first inclusive, second -exclusive) to be dumped. -@end table - -We can use @code{disassemble} to inspect the object code -range shown in the last @code{info line} example: - -@smallexample -(_GDBP__) disas 0x63e4 0x6404 -Dump of assembler code from 0x63e4 to 0x6404: -0x63e4 <builtin_init+5340>: ble 0x63f8 <builtin_init+5360> -0x63e8 <builtin_init+5344>: sethi %hi(0x4c00), %o0 -0x63ec <builtin_init+5348>: ld [%i1+4], %o0 -0x63f0 <builtin_init+5352>: b 0x63fc <builtin_init+5364> -0x63f4 <builtin_init+5356>: ld [%o0+4], %o0 -0x63f8 <builtin_init+5360>: or %o0, 0x1a4, %o0 -0x63fc <builtin_init+5364>: call 0x9288 <path_search> -0x6400 <builtin_init+5368>: nop -End of assembler dump. -(_GDBP__) - -@end smallexample - -@node Data, Languages, Source, Top -@chapter Examining Data - -@cindex printing data -@cindex examining data -@kindex print -@kindex inspect -@c "inspect" isn't quite a synonym if you're using Epoch, which we don't -@c document because it's 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}). You type - -@example -print @var{exp} -@end example - -@noindent -where @var{exp} is an expression (in the source language), and -the value of @var{exp} is printed in a format appropriate to its data -type. - -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}. - -If you're interested in information about types, or about how the fields -of a struct or class are declared, use the @code{ptype @var{exp}} -command rather than @code{print}. @xref{Symbols}. - -@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 -@end menu - -@node Expressions, Variables, Data, Data -@section Expressions - -@cindex expressions -@code{print} and many other _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 legal in an expression in -_GDBN__. This includes conditional expressions, function calls, casts -and string constants. It unfortunately does not include symbols defined -by preprocessor @code{#define} commands. - -Because C is so widespread, most of the expressions shown in examples in -this manual are in C. @xref{Languages,, Using _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 _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 so as to examine a structure -at that address in memory. -@c FIXME: casts supported---Mod2 true? - -_GDBN__ supports these operators in addition to those of programming -languages: - -@table @code -@item @@ -@samp{@@} is a binary operator for treating parts of memory as arrays. -@xref{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}. - -@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}.@refill -@end table - -@node Variables, Arrays, Expressions, Data -@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}); they must either be global (or static) or be visible -according to the scope rules of the programming language from the point of -execution in that frame. This means that in the function - -@example -foo (a) - int a; -@{ - bar (a); - @{ - int b = test (); - bar (b); - @} -@} -@end example - -@noindent -the variable @code{a} is usable whenever the program is executing -within the function @code{foo}, but the variable @code{b} is visible -only while the program is executing inside the block in which @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 variable in a particular file, using the colon-colon notation: - -@cindex colon-colon -@kindex :: -@example -@var{file}::@var{variable} -@end example - -@noindent -Here @var{file} is the name of the source file whose variable you want. - -@cindex C++ scope resolution -This use of @samp{::} is very rarely in conflict with the very similar -use of the same notation in C++. _GDBN__ also supports use of the C++ -scope resolution operator in _GDBN__ expressions. - -@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 the -function, and just before exit. You may see this problem when you're -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're stepping by machine instructions, -variables may appear to have the wrong values until the stack frame is -completely built. On function 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. -@end quotation - -@node Arrays, Output formats, Variables, Data -@section Artificial Arrays - -@cindex artificial array -@kindex @@ -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. - -This can be done by constructing an @dfn{artificial array} with the -binary operator @samp{@@}. The left operand of @samp{@@} should be -the first element of the desired array, as 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}), after printing one out.) - -Sometimes the artificial array mechanism isn't quite enough; in -moderately complex data structures, the elements of interest may not -actually be adjacent---for example, if you're 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}) 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're interested in the -values of a field @code{fv} in each structure. Here's 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, Memory, Arrays, Data -@section Output formats - -@cindex formatted output -@cindex output formats -By default, _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''. - -@item a -Print as an address, both absolute in hex and as an offset from the -nearest preceding symbol. This format can be used to discover where (in -what function) an unknown address is located: -@example -(_GDBP__) p/a 0x54320 -_0__$3 = 0x54320 <_initialize_vx+396>_1__ -@end example - - -@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 _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, Auto Display, Output formats, Data -@section Examining Memory - -@cindex examining memory -@table @code -@kindex x -@item x/@var{nfu} @var{expr} -The command @code{x} (for `examine') can be used to examine memory -without being constrained by your program's data types. You can specify -the unit size @var{u} of memory to inspect, and a repeat count @var{n} of how -many of those units to display. @code{x} understands the formats -@var{f} used by @code{print}; two additional formats, @samp{s} (string) -and @samp{i} (machine instruction) can be used without specifying a unit -size. -@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}) in hexadecimal (@samp{x}). - -Since the letters indicating unit sizes are all distinct from the -letters specifying output formats, you don't have to remember whether -unit size or format comes first; either order will work. The output -specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. - -After the format specification, you supply an expression for the address -where _GDBN__ is to begin reading from 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} for more -information on expressions. - -These are the memory units @var{u} you can specify with the @code{x} -command: - -@table @code -@item b -Examine individual bytes. - -@item h -Examine halfwords (two bytes each). - -@item w -Examine words (four bytes each). - -@cindex word -Many assemblers and cpu designers still use `word' for a 16-bit quantity, -as a holdover from specific predecessor machines of the 1970's that really -did use two-byte words. But more generally the term `word' has always -referred to the size of quantity that a machine normally operates on and -stores in its registers. This is 32 bits for all the machines that _GDBN__ -runs on. - -@item g -Examine giant words (8 bytes). -@end table - -You can combine these unit specifications with any of the formats -described for @code{print}. @xref{Output formats}. - -@code{x} has two additional output specifications which derive the unit -size from the data inspected: - -@table @code -@item s -Print a null-terminated string of characters. Any explicitly specified -unit size is ignored; instead, the unit is however many bytes it takes -to reach a null character (including the null character). - -@item i -Print a machine instruction in assembler syntax (or nearly). Any -specified unit size is ignored; the number of bytes in an instruction -varies depending on the type of machine, the opcode and the addressing -modes used. The command @code{disassemble} gives an alternative way of -inspecting machine instructions. @xref{Machine Code}. -@end table - -If you omit either the format @var{f} or the unit size @var{u}, @code{x} -will use the same one that was used last. If you don't use any letters -or digits after the slash, you can omit the slash as well. - -You can also omit the address to examine. Then the address used is just -after the last unit examined. This is why string and instruction -formats actually compute a unit-size based on the data: so that the next -string or instruction examined will start in the right place. - -When the @code{print} command shows a value that resides in memory, -@code{print} also sets the default address for the @code{x} command. -@code{info line} also sets the default for @code{x}, to the address of -the start of the machine code for the specified line -(@pxref{Machine Code}), -and @code{info breakpoints} sets it to the address of the last -breakpoint listed (@pxref{Set Breaks}).@refill - -When you use @key{RET} to repeat an @code{x} command, the address -specified previously (if any) is ignored, so that the repeated command -examines the successive locations in memory rather than the same ones. - -You can examine several consecutive units of memory with one command by -writing a repeat-count after the slash (before the format letters, if -any). Omitting the repeat count @var{n} displays one unit of the -appropriate size. The repeat count must be a decimal integer. It has -the same effect as repeating the @code{x} command @var{n} times except -that the output may be more compact, with several units per line. For -example, - -@example -x/10i $pc -@end example - -@noindent -prints ten instructions starting with the one to be executed next in the -selected frame. After doing this, you could print a further seven -instructions with - -@example -x/7 -@end example - -@noindent ----where the format and address are allowed to default. - -@cindex @code{$_}, @code{$__}, and value history -The addresses and contents printed by the @code{x} command are not put -in the value history because there is often too much of them and they -would get in the way. Instead, _GDBN__ makes these values available for -subsequent use in expressions as values of the convenience variables -@code{$_} 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, Print Settings, Memory, Data -@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 _GDBN__ will print its value each time the 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 -showing 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 -@item display @var{exp} -@kindex display -Add the expression @var{exp} to the list of expressions to display -each time the program stops. @xref{Expressions}. - -@code{display} will not repeat if you press @key{RET} again after using it. - -@item display/@var{fmt} @var{exp} -For @var{fmt} specifying only a display format and not a size or -count, add the expression @var{exp} to the auto-display list but -arranges to display it each time in the specified format @var{fmt}. -@xref{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 the program stops. Examining means in effect -doing @samp{x/@var{fmt} @var{addr}}. @xref{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}). - -@table @code -@item undisplay @var{dnums}@dots{} -@itemx delete display @var{dnums}@dots{} -@kindex delete display -@kindex undisplay -Remove item numbers @var{dnums} from the list of expressions to display. - -@code{undisplay} will not repeat if you press @key{RET} after using it. -(Otherwise you would just get the error @samp{No display number @dots{}}.) - -@item disable display @var{dnums}@dots{} -@kindex disable display -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. - -@item enable display @var{dnums}@dots{} -@kindex enable display -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 the program stops. - -@item info display -@kindex 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}, then this argument will be displayed while the program -continues to stop inside that function. When it stops elsewhere---where -there is no variable @code{last_char}---display is disabled. The next time -your program stops where @code{last_char} is meaningful, you can enable the -display expression once again. - -@node Print Settings, Value History, Auto Display, Data -@section Print Settings - -@cindex format options -@cindex print settings -_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 -@item set print address -@item set print address on -@kindex set print address -_GDBN__ will print 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 on. For example, this is what a stack frame display looks like, with -@code{set print address on}: -@smallexample -(_GDBP__) f -#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") - at input.c:530 -530 if (lquote != def_lquote) -@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}: -@example -(_GDBP__) set print addr off -(_GDBP__) f -#0 set_quotes (lq="<<", rq=">>") at input.c:530 -530 if (lquote != def_lquote) -@end example - -@item show print address -@kindex show print address -Show whether or not addresses are to be printed. - -@item set print array -@itemx set print array on -@kindex set print array -_GDBN__ will 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. - -@item show print array -@kindex show print array -Show whether compressed or pretty format is selected for displaying -arrays. - -@item set print elements @var{number-of-elements} -@kindex set print elements -If _GDBN__ is printing a large array, it will stop 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. - -@item show print elements -@kindex show print elements -Display the number of elements of a large array that _GDBN__ will print -before losing patience. - -@item set print pretty on -@kindex set print pretty -Cause _GDBN__ to print structures in an indented format with one member per -line, like this: - -@example -$1 = @{ - next = 0x0, - flags = @{ - sweet = 1, - sour = 1 - @}, - meat = 0x54 "Pork" -@} -@end example - -@item set print pretty off -Cause _GDBN__ to print structures in a compact format, like this: - -@smallexample -$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, meat \ -= 0x54 "Pork"@} -@end smallexample - -@noindent -This is the default format. - -@item show print pretty -@kindex show print pretty -Show which format _GDBN__ will use to print structures. - -@item set print sevenbit-strings on -@kindex set print sevenbit-strings -Print using only seven-bit characters; if this option is set, -_GDBN__ will display any eight-bit characters (in strings or character -values) using the notation @code{\}@var{nnn}. For example, @kbd{M-a} is -displayed as @code{\341}. - -@item set print sevenbit-strings off -Print using either seven-bit or eight-bit characters, as required. This -is the default. - -@item show print sevenbit-strings -@kindex show print sevenbit-strings -Show whether or not _GDBN__ will print only seven-bit characters. - -@item set print union on -@kindex set print union -Tell _GDBN__ to print unions which are contained in structures. This is the -default setting. - -@item set print union off -Tell _GDBN__ not to print unions which are contained in structures. - -@item show print union -@kindex show print union -Ask _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 - -@noindent -These settings are of interest when debugging C++ programs: - -@table @code -@item set print demangle -@itemx set print demangle on -@kindex set print demangle -Print C++ names in their source form rather than in the mangled form -in which they are passed to the assembler and linker for type-safe linkage. -The default is on. - -@item show print demangle -@kindex show print demangle -Show whether C++ names will be printed in mangled or demangled form. - -@item set print asm-demangle -@itemx set print asm-demangle on -@kindex set print asm-demangle -Print C++ names in their source form rather than their mangled form, even -in assembler code printouts such as instruction disassemblies. -The default is off. - -@item show print asm-demangle -@kindex show print asm-demangle -Show whether C++ names in assembly listings will be printed in mangled -or demangled form. - -@item set print object -@itemx set print object on -@kindex set print object -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. - -@item show print object -@kindex show print object -Show whether actual, or declared, object types will be displayed. - -@item set print vtbl -@itemx set print vtbl on -@kindex set print vtbl -Pretty print C++ virtual function tables. The default is off. - -@item set print vtbl off -Do not pretty print C++ virtual function tables. - -@item show print vtbl -@kindex show print vtbl -Show whether C++ virtual function tables are pretty printed, or not. - -@end table - -@node Value History, Convenience Vars, Print Settings, Data -@section Value History - -@cindex value history -Values printed by the @code{print} command are saved in _GDBN__'s @dfn{value -history} so that you can 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{$$} -@cindex history number -The values printed are given @dfn{history numbers} for you to refer to them -by. These are successive integers starting with one. @code{print} shows you -the history number assigned to a value by printing @samp{$@var{num} = } -before the value; here @var{num} is the history number. - -To refer to any previous value, use @samp{$} followed by the value's -history number. The way @code{print} labels its output is designed to -remind you of this. Just @code{$} refers to the most recent value in -the history, and @code{$$} 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, 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, Registers, Value History, Data -@section Convenience Variables - -@cindex convenience variables -_GDBN__ provides @dfn{convenience variables} that you can use within -_GDBN__ to hold on to a value and refer to it later. These variables -exist entirely within _GDBN__; they are not part of your program, and -setting a convenience variable has no direct effect on further execution -of your program. That's 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}). -(Value history references, in contrast, are @emph{numbers} preceded -by @samp{$}. @xref{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. 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 -@item show convenience -@kindex show convenience -Print a list of convenience variables used so far, and their values. -Abbreviated @code{show con}. -@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: - -_0__@example -set $i = 0 -print bar[$i++]->contents -@i{@dots{} repeat that command by typing @key{RET}.} -_1__@end example - -Some convenience variables are created automatically by _GDBN__ and given -values likely to be useful. - -@table @code -@item $_ -@kindex $_ -The variable @code{$_} is automatically set by the @code{x} command to -the last address examined (@pxref{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{$__}. - -@item $__ -@kindex $__ -The variable @code{$__} 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. -@end table - -@node Registers, Floating Point Hardware, Convenience Vars, Data -@section Registers - -@cindex registers -You can refer to machine register contents, in expressions, as variables -with names starting with @samp{$}. The names of registers are different -for each machine; use @code{info registers} to see the names used on -your machine. - -@table @code -@item info registers -@kindex info registers -Print the names and values of all registers except floating-point -registers (in the selected stack frame). - -@item info all-registers -@kindex info all-registers -@cindex floating point registers -Print the names and values of all registers, including floating-point -registers. - -@item info registers @var{regname} -Print the relativized value of register @var{regname}. @var{regname} -may be any register name valid on the machine you are using, with -or without the initial @samp{$}. -@end table - -The register names @code{$pc} and @code{$sp} are used on most machines -for the program counter register and the stack pointer. 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 with -@example -set $sp += 4 -@end example - -@noindent -The last is a way of removing one word from the stack, on machines where -stacks grow downward in memory (most machines, nowadays). This assumes -that the innermost stack frame is selected; setting @code{$sp} is -not allowed when other stack frames are selected. (To pop entire frames -off the stack, regardless of machine architecture, use @code{return}; -@pxref{Returning}.) - -Often @code{$fp} is used for a register that contains a pointer to the -current stack frame, and @code{$ps} is sometimes used for a register -that contains the processor status. These standard register names may -be available on your machine even though the @code{info registers} -command shows other 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}. - -_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, _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}). 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, _GDBN__ must deduce where registers are saved, from the machine -code generated by your compiler. If some registers are not saved, or if -_GDBN__ is unable to locate the saved registers, the selected stack -frame will make no difference. - -@node Floating Point Hardware, , Registers, Data -@section Floating Point Hardware -@cindex floating point -Depending on the host machine architecture, _GDBN__ may be able to give -you more information about the status of the floating point hardware. - -@table @code -@item info float -@kindex info float -If available, provides hardware-dependent information about the floating -point unit. The exact contents and layout vary depending on the -floating point chip. -@end table -@c FIXME: this is a cop-out. Try to get examples, explanations. Only -@c FIXME...supported currently on arm's and 386's. Mark properly with -@c FIXME... m4 macros to isolate general statements from hardware-dep, -@c FIXME... at that point. - -@node Languages, Symbols, Data, Top -@chapter Using _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 are written -like @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}. - -@cindex working language -Language-specific information is built into _GDBN__ for some languages, -allowing you to express operations like the above in the program's -native language, and allowing _GDBN__ to output values in a manner -consistent with the syntax of the program's native language. The -language you use to build expressions, called the @dfn{working -language}, can be selected manually, or _GDBN__ can set it -automatically. - -@menu -* Setting:: Switching between source languages -* Show:: Displaying the language -* Checks:: Type and Range checks -* Support:: Supported languages -@end menu - -@node Setting, Show, Languages, Languages -@section Switching between source languages - -There are two ways to control the working language---either have _GDBN__ -set it automatically, or select it manually yourself. You can use the -@code{set language} command for either purpose. On startup, _GDBN__ -defaults to setting the language automatically. - -@menu -* Manually:: Setting the working language manually -* Automatically:: Having _GDBN__ infer the source language -@end menu - -@node Manually, Automatically, Setting, Setting -@subsection Setting the working language - -@kindex set language -To set the language, issue the command @samp{set language @var{lang}}, -where @var{lang} is the name of a language: @code{c} or @code{modula-2}. -For a list of the supported languages, type @samp{set language}. - -Setting the language manually prevents _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 _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. - -If you allow _GDBN__ to set the language automatically, then -you can count on expressions evaluating the same way in your debugging -session and in your program. - -@node Automatically, , Manually, Setting -@subsection Having _GDBN__ infer the source language - -To have _GDBN__ set the working language automatically, use @samp{set -language local} or @samp{set language auto}. _GDBN__ then infers the -language that a program was written in by looking at the name of its -source files, and examining their extensions: - -@table @file -@item *.mod -Modula-2 source file - -@item *.c -@itemx *.cc -C or C++ source file. -@end table - -This information is recorded for each function or procedure in a source -file. When your program stops in a frame (usually by encountering a -breakpoint), _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 _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, Checks, Setting, Languages -@section Displaying the language - -The following commands will 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 -@kindex info source -@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 the program. - -@item info frame -Among the other information listed here (@pxref{Frame Info,,Information -about a Frame}) is the source language for this frame. This is the -language that will become the working language if you ever use an -identifier that is in this frame. - -@item info source -Among the other information listed here (@pxref{Symbols,,Examining the -Symbol Table}) is the source language of this source file. - -@end table - -@node Checks, Support, Show, Languages -@section Type and range Checking - -@quotation -@emph{Warning:} In this release, the _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 the program is running. - -_GDBN__ can check for conditions like the above if you wish. -Although _GDBN__ will not check the statements in your program, it -can check expressions entered directly into _GDBN__ for evaluation via -the @code{print} command, for example. As with the working language, -_GDBN__ can also decide whether or not to check automatically based on -the source language of the program being debugged. -@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, Range Checking, Checks, Checks -@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, - -@example -1 + 2 @result{} 3 -@error{} 1 + 2.3 -@end example - -The second example fails because the @code{CARDINAL} 1 is not -type-compatible with the @code{REAL} 2.3. - -For expressions you use in _GDBN__ commands, you can tell the _GDBN__ -type checker to skip checking; to treat any mismatches as errors and -abandon the expression; or only issue warnings when type mismatches -occur, but evaluate the expression anyway. When you choose the last of -these, _GDBN__ evaluates expressions like the second example above, but -also issues a warning. - -Even though you may turn type checking off, other type-based reasons may -prevent _GDBN__ from evaluating an expression. For instance, _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 futher -details on specific languages. - -_GDBN__ provides some additional commands for controlling the type checker: - -@kindex set check -@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's default. If any type mismatches occur in -evaluating an expression while typechecking is on, _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, _GDBN__ cannot add -numbers and structures. - -@item show type -Show the current setting of the type checker, and whether or not _GDBN__ is -setting it automatically. -@end table - -@cindex range checking -@cindex checks, range -@node Range Checking, , Type Checking, Checks -@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 _GDBN__ commands, you can tell _GDBN__ to -ignore range errors; to always treat them as errors and abandon the -expression; or to issue warnings when a range error occurs but evaluate -the expression anyway. - -A range error can result from numerical overflow, from exceeding an -array index bound, or when you type in 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. - -_GDBN__ provides some additional commands for controlling the range checker: - -@kindex set check -@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's default. If a range error occurs, then a message -is printed and evaluation of the expression is aborted. - -@item set check range warn -Output messages when the _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 _GDBN__. -@end table - -@node Support, , Checks, Languages -@section Supported Languages - -_GDBN__ _GDB_VN__ supports C, C++, and Modula-2. The syntax for C and C++ is -so closely related that _GDBN__ does not distinguish the two. Some -_GDBN__ features may be used in expressions regardless of the language -you use: the _GDBN__ @code{@@} and @code{::} operators, and the -@samp{@{type@}addr} construct (@pxref{Expressions}) can be used with the constructs of -any of the supported languages. - -The following sections detail to what degree each of these -source languages is supported by _GDBN__. These sections are -not meant to be language tutorials or references, but serve only as a -reference guide to what the _GDBN__ expression parser will accept, 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++ -* Modula-2:: Modula-2 -@end menu - -@node C, Modula-2, Support, Support -@subsection C and C++ -@cindex C and C++ - -@cindex expressions in C or C++ -Since C and C++ are so closely related, _GDBN__ does not distinguish -between them when interpreting the expressions recognized in _GDBN__ -commands. - -@cindex C++ -@kindex g++ -@cindex GNU C++ -The C++ debugging facilities are jointly implemented by the GNU C++ -compiler and _GDBN__. Therefore, to debug your C++ code effectively, -you must compile your C++ programs with the GNU C++ compiler, -@code{g++}. - - -@menu -* C Operators:: C and C++ Operators -* C Constants:: C and C++ Constants -* Cplusplus expressions:: C++ Expressions -* C Defaults:: Default settings for C and C++ -* C Checks:: C and C++ Type and Range Checks -* Debugging C:: _GDBN__ and C -* Debugging C plus plus:: Special features for C++ -@end menu - -@cindex C and C++ operators -@node C Operators, C Constants, C, C -@subsubsection C and C++ 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++, the -following definitions hold: - -@itemize @bullet -@item -@emph{Integral types} include @code{int} with any of its storage-class -specifiers, @code{char}, and @code{enum}s. - -@item -@emph{Floating-point types} include @code{float} and @code{double}. - -@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 -_0__ -@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 @var{a} @var{op}@code{=} @var{b}, and -translated to @var{a} @code{=} @var{a op b}. @var{op}@code{=} and -@code{=} have the same precendence. @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 OR. Defined on integral types. - -@item && -Logical AND. Defined on integral types. - -@item | -Bitwise OR. Defined on integral types. - -@item ^ -Bitwise exclusive-OR. Defined on integral types. - -@item & -Bitwise 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 _GDBN__ ``artificial array'' operator (@pxref{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{++}. - -@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, -_GDBN__ regards the two as equivalent, choosing whether to dereference a -pointer based on the stored type information. -Defined on @code{struct}s and @code{union}s. - -@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++ scope resolution operator. Defined on -@code{struct}, @code{union}, and @code{class} types. - -@item :: -The _GDBN__ scope operator (@pxref{Expressions}). Same precedence as -@code{::}, above. _1__ -@end table - -@cindex C and C++ constants -@node C Constants, Cplusplus expressions, C Operators, C -@subsubsection C and C++ Constants - -_GDBN__ allows you to express the constants of C and C++ in the -following ways: - -@itemize @bullet - -@item -Integer constants are a sequence of digits. Octal constants are -specified by a leading @samp{0} (ie. zero), and hexadecimal constants by -a leading @samp{0x} or @samp{0X}. Constants may also end with an -@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. - -@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{"}). - -@item -Pointer constants are an integral value. - -@end itemize - - -@node Cplusplus expressions, C Defaults, C Constants, C -@subsubsection C++ Expressions - -@cindex expressions in C++ -_GDBN__'s expression handling has the following extensions to -interpret a significant subset of C++ expressions: - -@enumerate - -@cindex member functions -@item -Member function calls are allowed; you can use expressions like -@example -count = aml->GetOriginal(x, y) -@end example - -@kindex this -@cindex namespace in C++ -@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, _GDBN__ allows implicit references to the class instance -pointer @code{this} following the same rules as C++. - -@cindex call overloaded functions -@cindex type conversions in C++ -@item -You can call overloaded functions; _GDBN__ will resolve the function -call to the right definition, with one restriction---you must use -arguments of the type required by the function that you want to call. -_GDBN__ will not perform conversions requiring constructors or -user-defined type operators. - -@cindex reference declarations -@item -_GDBN__ understands variables declared as C++ references; you can use them in -expressions just as you do in C++ source---they are automatically -dereferenced. - -In the parameter list shown when _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've specified @samp{set print address off}. - - -@item -_GDBN__ supports the C++ 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}}. _GDBN__ also allows -resolving name scope by reference to source files, in both C and C++ -debugging; @pxref{Variables}. - -@end enumerate - - -@node C Defaults, C Checks, Cplusplus expressions, C -@subsubsection C and C++ Defaults -@cindex C and C++ defaults - -If you allow _GDBN__ to set type and range checking automatically, they -both default to @code{off} whenever the working language changes to -C/C++. This happens regardless of whether you, or _GDBN__, -selected the working language. - -If you allow _GDBN__ to set the language automatically, it sets the -working language to C/C++ on entering code compiled from a source file -whose name ends with @file{.c} or @file{.cc}. -@xref{Automatically,,Having _GDBN__ infer the source language}, for -further details. - -@node C Checks, Debugging C, C Defaults, C -@subsubsection C and C++ Type and Range Checks -@cindex C and C++ checks - -@quotation -@emph{Warning:} in this release, _GDBN__ does not yet perform type or -range checking. -@end quotation -@c FIXME remove warning when type/range checks added - -By default, when _GDBN__ parses C or C++ expressions, type checking -is not used. However, if you turn type checking on, _GDBN__ will -consider two variables type equivalent if: - -@itemize @bullet -@item -The two variables are structured and have the same structure, union, or -enumerated tag. - -@item -Two 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, Debugging C plus plus, C Checks, C -@subsubsection _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} will also be printed. -Otherwise, it will appear as @samp{@{...@}}. - -The @code{@@} operator aids in the debugging of dynamic arrays, formed -with pointers and a memory allocation function. (@pxref{Expressions}) - -@node Debugging C plus plus, , Debugging C, C -@subsubsection _GDBN__ Commands for C++ - -@cindex commands for C++ -Some _GDBN__ commands are particularly useful with C++, and some are -designed specifically for use with C++. 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, -_GDBN__'s breakpoint menus help you specify which function definition -you want. @xref{Breakpoint Menus}. - -@cindex overloading in C++ -@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}. - -@cindex C++ exception handling -@item catch @var{exceptions} -@itemx info catch -Debug C++ exception handling using these commands. @xref{Exception Handling}. - -@cindex inheritance -@item ptype @var{typename} -Print inheritance relationships as well as other information for type -@var{typename}. -@xref{Symbols}. - -@cindex C++ symbol display -@item set print demangle -@itemx show print demangle -@itemx set print asm-demangle -@itemx show print asm-demangle -Control whether C++ symbols display in their source form, both when -displaying code as C++ source and when displaying disassemblies. -@xref{Print Settings}. - -@item set print object -@itemx show print object -Choose whether to print derived (actual) or declared types of objects. -@xref{Print Settings}. - -@item set print vtbl -@itemx show print vtbl -Control the format for printing virtual function tables. -@xref{Print Settings}. - -@end table - - -@node Modula-2, , C, Support -@subsection Modula-2 -@cindex Modula-2 - -The extensions made to _GDBN__ to support Modula-2 support output -from the 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 will most likely result in an error -as _GDBN__ reads in the executable's symbol table. - -@cindex expressions in Modula-2 -@menu -* M2 Operators:: Built-in operators -* Builtin 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:: _GDBN__ and Modula-2 -@end menu - -@node M2 Operators, Builtin Func/Proc, Modula-2, Modula-2 -@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}s and @code{BITSET}s. - -@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 -_0__ -@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, greater than, 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 _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 conjuction. Defined on boolean types. - -@item @@ -The _GDBN__ ``artificial array'' operator (@pxref{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}s and @code{REAL}s. - -@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}s. Same -precedence as @code{^}. - -@item [] -Array indexing. Defined on @code{ARRAY}s. Same precedence as @code{^}. - -@item () -Procedure argument list. Defined on @code{PROCEDURE}s. Same precedence -as @code{^}. - -@item ::@r{, }. -_GDBN__ and Modula-2 scope operators. - -@end table - -@quotation -@emph{Warning:} Sets and their operations are not yet supported, so _GDBN__ -will treat 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 -_1__ - -@cindex Modula-2 builtins -@node Builtin Func/Proc, M2 Constants, M2 Operators, Modula-2 -@subsubsection Built-in Functions and Procedures - -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}. 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}. 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 ASCII value (on machines supporting the -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 -_GDBN__ will treat the use of procedures @code{INCL} and @code{EXCL} as -an error. -@end quotation - -@cindex Modula-2 constants -@node M2 Constants, M2 Defaults, Builtin Func/Proc, Modula-2 -@subsubsection Constants - -_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 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}, 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, Deviations, M2 Constants, Modula-2 -@subsubsection Modula-2 Defaults -@cindex Modula-2 defaults - -If type and range checking are set automatically by _GDBN__, they -both default to @code{on} whenever the working language changes to -Modula-2. This happens regardless of whether you, or _GDBN__, -selected the working language. - -If you allow _GDBN__ to set the language automatically, then entering -code compiled from a file whose name ends with @file{.mod} will set the -working language to Modula-2. @xref{Automatically,,Having _GDBN__ set -the language automatically}, for further details. - -@node Deviations, M2 Checks, M2 Defaults, Modula-2 -@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. _GDBN__ will print 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 builtin procedures both modify @emph{and} return their argument. - -@end itemize - -@node M2 Checks, M2 Scope, Deviations, Modula-2 -@subsubsection Modula-2 Type and Range Checks -@cindex Modula-2 checks - -@quotation -@emph{Warning:} in this release, _GDBN__ does not yet perform type or -range checking. -@end quotation -@c FIXME remove warning when type/range checks added - -_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 -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 builtin functions and procedures. - -@node M2 Scope, GDB/M2, M2 Checks, Modula-2 -@subsubsection The scope operators @code{::} and @code{.} -@cindex scope -@kindex . -@kindex :: - -There are a few subtle differences between the Modula-2 scope operator -(@code{.}) and the _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 delcared -identifier within the program, except another module. - -Using the @code{::} operator makes _GDBN__ search the scope -specified by @var{scope} for the identifier @var{id}. If it is not -found in the specified scope, then _GDBN__ will search all scopes -enclosing the one specified by @var{scope}. - -Using the @code{.} operator makes _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, , M2 Scope, Modula-2 -@subsubsection _GDBN__ and Modula-2 - -Some _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++: @samp{vtbl}, @samp{demangle}, -@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four -apply to C++, and the last to C's @code{union} type, which has no direct -analogue in Modula-2. - -The @code{@@} operator (@pxref{Expressions}), while available -while using 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++. However, because an -address can be specified by an integral constant, the construct -@samp{@{@var{type}@}@var{adrexp}} is still useful. (@pxref{Expressions}) - -_0__ -@cindex @code{#} in Modula-2 -In _GDBN__ scripts, the Modula-2 inequality operator @code{#} is -interpreted as the beginning of a comment. Use @code{<>} instead. -_1__ - - -@node Symbols, Altering, Languages, Top -@chapter Examining the Symbol Table - -The commands described in this section 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 the program executes. _GDBN__ finds it in your -program's symbol table, in the file indicated when you started _GDBN__ -(@pxref{File Options}), or by one of the file-management commands -(@pxref{Files}). - -@table @code -@item info address @var{symbol} -@kindex info address -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 variables, and for a stack local variable prints -the exact address of the current instantiation of the variable. - -@item whatis @var{exp} -@kindex whatis -Print the data type of expression @var{exp}. @var{exp} is not -actually evaluated, and any side-effecting operations (such as -assignments or function calls) inside it do not take place. -@xref{Expressions}. - -@item whatis -Print the data type of @code{$}, the last value in the value history. - -@item ptype @var{typename} -@kindex ptype -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{struct @var{struct-tag}}, @samp{union @var{union-tag}} or -@samp{enum @var{enum-tag}}.@refill - -@item ptype @var{exp} -Print a description of the type of expression @var{exp}. @code{ptype} -differs from @code{whatis} by printing a detailed description, instead of just -the name of the type. For example, if your program declares a variable -as -@example -struct complex @{double real; double imag;@} v; -@end example -@noindent -compare the output of the two commands: -@example -(_GDBP__) whatis v -type = struct complex -(_GDBP__) ptype v -type = struct complex @{ - double real; - double imag; -@} -@end example - -@item info types @var{regexp} -@itemx info types -@kindex info types -Print a brief description of all types whose name matches @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 -name includes 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. - -@item info source -@kindex 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. - -@item info sources -@kindex info sources -Print the names of all source files in the 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. - -@item info functions -@kindex 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}. - -@item info variables -@kindex 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. -@item info methods -@itemx info methods @var{regexp} -@kindex info methods -The @code{info methods} command permits the user to examine all defined -methods within C++ program, or (with the @var{regexp} argument) a -specific set of methods found in the various C++ classes. Many -C++ 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 - -@item printsyms @var{filename} -@kindex printsyms -Write a dump of debugging symbol data into the file -@var{filename}. Only symbols with debugging data are included. _GDBN__ -includes all the symbols it already knows about: that is, @var{filename} -reflects symbols for only those files whose symbols _GDBN__ has read. -You can find out which files these are using the command @code{info -files}. The description of @code{symbol-file} describes how _GDBN__ -reads symbols; both commands are described under @ref{Files}. -@end table - -@node Altering, _GDBN__ Files, Symbols, Top -@chapter Altering Execution - -Once you think you have found an error in the 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 _GDBN__ features for altering execution of the -program. - -For example, you can store new values into variables or memory -locations, give the program a signal, restart it at a different address, -or even return prematurely from a function to its caller. - -@menu -* Assignment:: Assignment to Variables -* Jumping:: Continuing at a Different Address -* Signaling:: Giving the Program a Signal -* Returning:: Returning from a Function -* Calling:: Calling your Program's Functions -* Patching:: Patching your Program -@end menu - -@node Assignment, Jumping, Altering, Altering -@section Assignment to Variables - -@cindex assignment -@cindex setting variables -To alter the value of a variable, evaluate an assignment expression. -@xref{Expressions}. For example, - -@example -print x=4 -@end example - -@noindent -would store the value 4 into the variable @code{x}, and then print the -value of the assignment expression (which is 4). @xref{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}). 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, a -program might well have a variable @code{width}---which leads to -an error if we try to set a new value with just @samp{set width=13}, as -we might if @code{set width} didn't happen to be a _GDBN__ command: -@example -(_GDBP__) whatis width -type = double -(_GDBP__) p width -$4 = 13 -(_GDBP__) set width=47 -Invalid syntax in expression. -@end example -@noindent -The invalid expression, of course, is @samp{=47}. What we can do in -order to actually set our program's variable @code{width} is -@example -(_GDBP__) set var width=47 -@end example - -_GDBN__ allows more implicit conversions in assignments than C does; you can -freely store an integer value into a pointer variable or vice versa, and -any structure can be converted to any other structure that is the same -length or shorter. -@comment FIXME: how do structs align/pad in these conversions? -@comment /pesch@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}). 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, Signaling, Assignment, Altering -@section Continuing at a Different Address - -Ordinarily, when you continue the 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 -@item jump @var{linespec} -@kindex jump -Resume execution at line @var{linespec}. Execution will stop -immediately if there is a breakpoint there. @xref{List} for a -description of the different forms of @var{linespec}. - -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 the program. - -@item jump *@var{address} -Resume execution at the instruction at address @var{address}. -@end table - -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 the program running; it only changes the address where it -@emph{will} run when it is continued. For example, - -@example -set $pc = 0x485 -@end example - -@noindent -causes the next @code{continue} command or stepping command to execute at -address 0x485, rather than at the address where the program stopped. -@xref{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. - -@node Signaling, Returning, Jumping, Altering -@c @group -@section Giving the Program a Signal - -@table @code -@item signal @var{signalnum} -@kindex signal -Resume execution where the program stopped, but give it immediately the -signal number @var{signalnum}. - -Alternatively, if @var{signalnum} is zero, continue execution without -giving a signal. This is useful when the 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 - -@node Returning, Calling, Signaling, Altering -@section Returning from a Function - -@table @code -@item return -@itemx return @var{expression} -@cindex returning from a function -@kindex return -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}, _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}), 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}) -resumes execution until the selected stack frame returns naturally.@refill - -@node Calling, Patching, Returning, Altering -@section Calling your Program's 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. The result is printed and saved in -the value history, if it is not void. - -@node Patching, , Calling, Altering -@section Patching your Program -@cindex patching binaries -@cindex writing into executables -@cindex writing into corefiles -By default, _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 -@item set write on -@itemx set write off -@kindex set write -If you specify @samp{set write on}, _GDBN__ will open executable and -core files for both reading and writing; if you specify @samp{set write -off} (the default), _GDBN__ will open them read-only. - -If you've 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 will be opened for -writing as well as reading. - -@end table - -@node _GDBN__ Files, Targets, Altering, Top -@chapter _GDBN__'s Files - -@menu -* Files:: Commands to Specify Files -* Symbol Errors:: Errors Reading Symbol Files -@end menu - -@node Files, Symbol Errors, _GDBN__ Files, _GDBN__ Files -@section Commands to Specify Files -@cindex core dump file -@cindex symbol table -_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 the program. To -debug a core dump of a previous run, _GDBN__ must be told the file name of -the core dump. - -The usual way to specify the executable and core dump file names is with -the command arguments given when you start _GDBN__, as discussed in -@pxref{Invocation}. - -Occasionally it is necessary to change to a different file during a -_GDBN__ session. Or you may run _GDBN__ and forget to specify the files you -want to use. In these situations the _GDBN__ commands to specify new files -are useful. - -@table @code -@item file @var{filename} -@cindex executable file -@kindex file -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 _GDBN__'s working directory, - -_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 _GDBN__ and -your program, using the @code{path} command. - -@code{file} with no argument makes _GDBN__ discard any information it -has on both executable file and the symbol table. - -@item exec-file @var{filename} -@kindex exec-file -Specify that the program to be run (but not the symbol table) is found -in @var{filename}. _GDBN__ will search the environment variable @code{PATH} -if necessary to locate the program. - -@item symbol-file @var{filename} -@kindex symbol-file -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 _GDBN__'s information on your -program's symbol table. - -The @code{symbol-file} command causes _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 _GDBN__. - -@code{symbol-file} will not repeat if you press @key{RET} again after -executing it once. - -On some kinds of object files, the @code{symbol-file} command does not -actually 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, -when they are needed. - -The purpose of this two-stage reading strategy is to make _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}). - -When the symbol table is stored in COFF format, @code{symbol-file} does -read the symbol table data in full right away. We haven't implemented -the two-stage strategy for COFF yet. - -When _GDBN__ is configured for a particular environment, it will -understand debugging information in whatever format is the standard -generated for that environment; you may use either a GNU compiler, or -other compilers that adhere to the local conventions. Best results are -usually obtained from GNU compilers; for example, using @code{_GCC__} -you can generate debugging information for optimized code. - -@item core-file @var{filename} -@itemx core @var{filename} -@kindex core -@kindex core-file -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; _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 _GDBN__. So, if you have been running the 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}). - -@item load @var{filename} -@kindex load -_if__(_GENERIC__) -Depending on what remote debugging facilities are configured into -_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 @var{filename}'s symbol table in _GDBN__, like -the @code{add-symbol-file} command. - -If @code{load} is not available on your _GDBN__, attempting to execute -it gets the error message ``@code{You can't do that when your target is -@dots{}}'' -_fi__(_GENERIC__) - -_if__(_VXWORKS__) -On VxWorks, @code{load} will dynamically link @var{filename} on the -current target system as well as adding its symbols in _GDBN__. -_fi__(_VXWORKS__) - -_if__(_I960__) -@cindex download to Nindy-960 -With the Nindy interface to an Intel 960 board, @code{load} will -download @var{filename} to the 960 as well as adding its symbols in -_GDBN__. -_fi__(_I960__) - -@code{load} will not repeat if you press @key{RET} again after using it. - -@item add-symbol-file @var{filename} @var{address} -@kindex add-symbol-file -@cindex dynamic linking -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; _GDBN__ cannot figure this out for itself. - -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. - -@code{add-symbol-file} will not repeat if you press @key{RET} after using it. - -@item info files -@itemx info target -@kindex info files -@kindex info target -@code{info files} and @code{info target} are synonymous; both print the -current targets (@pxref{Targets}), including the names of the executable -and core dump files currently in use by _GDBN__, and the files from -which symbols were loaded. The command @code{help targets} lists all -possible targets rather than current ones. - -@end table - -All file-specifying commands allow both absolute and relative file names -as arguments. _GDBN__ always converts the file name to an absolute path -name and remembers it that way. - -@cindex shared libraries - -_GDBN__ supports the SunOS shared library format. _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, _GDBN__ won't understand references to a -function in a shared library, however---unless you're debugging a core -file). -@c FIXME: next _GDBN__ release should permit some refs to undef -@c FIXME...symbols---eg in a break cmd---assuming they're from a shared lib - -@table @code -@item info share -@itemx info sharedlibrary -@kindex info sharedlibrary -@kindex info share -Print the names of the shared libraries which are currently loaded. - -@item sharedlibrary @var{regex} -@itemx share @var{regex} -@kindex sharedlibrary -@kindex share -This is an obsolescent command; you can use it to explicitly -load shared object library symbols for files matching a UNIX regular -expression, but as with files loaded automatically, it will only load -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 - -@node Symbol Errors, , Files, _GDBN__ Files -@section Errors Reading Symbol Files -While reading a symbol file, _GDBN__ will occasionally encounter -problems, such as symbol types it does not recognize, or known bugs in -compiler output. By default, _GDBN__ does not notify you of such -problems, since they're 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 _GDBN__ to print -only one message about each such type of problem, no matter how many -times the problem occurs; or you can ask _GDBN__ to print more messages, -to see how many times the problems occur, with the @code{set complaints} -command (@xref{Messages/Warnings}). - -The messages currently printed, and their meanings, are: - -@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. - -_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. - -_GDBN__ does not circumvent this problem, and will have trouble locating -symbols in the source file whose symbols being read. (You can often -determine what source file is affected by specifying @code{set verbose -on}. @xref{Messages/Warnings}.) - -@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. - -_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. - -_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 _GDBN__ does not yet -know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood -information, in hexadecimal. - -_GDBN__ circumvents the error by ignoring this symbol information. This -will usually allow the program to be debugged, though certain symbols -will not be accessible. If you encounter such a problem and feel like -debugging it, you can debug @code{_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 -_GDBN__ could not find the full definition for a struct or class. - -@ignore -@c this is #if 0'd in dbxread.c as of (at least!) 17 may 1991 -@item const/volatile indicator missing, got '@var{X}' - -The symbol information for a C++ member function is missing some -information that the compiler should have output for it. -@end ignore - -@item C++ type mismatch between compiler and debugger - -_GDBN__ could not parse a type specification output by the compiler -for some C++ object. - -@end table - -@node Targets, Controlling _GDBN__, _GDBN__ Files, Top -@chapter Specifying a Debugging Target -@cindex debugging target -@kindex target -A @dfn{target} is an interface between the debugger and a particular -kind of file or process. - -Often, you will be able to run _GDBN__ in the same host environment as the -program you are debugging; in that case, the debugging target can just be -specified as a side effect of the @code{file} or @code{core} commands. -When you need more flexibility---for example, running _GDBN__ on a -physically separate host, controlling standalone systems over a -serial port, or realtime systems over a TCP/IP connection---you can use -the @code{target} command. - -@menu -* Active Targets:: Active Targets -* Target Commands:: Commands for Managing Targets -* Remote:: Remote Debugging -@end menu - -@node Active Targets, Target Commands, Targets, Targets -@section Active Targets -@cindex stacking targets -@cindex active targets -@cindex multiple targets - -Targets are managed in three @dfn{strata} that correspond to different -classes of target: processes, core files, and executable files. This -allows you to (for example) start a process and inspect its activity -without abandoning your work on a core file. - -More than one target can potentially respond to a request. In -particular, when you access memory _GDBN__ will examine the three strata of -targets until it finds a target that can handle that particular address. -Strata are always examined in a fixed order: first a process if there is -one, then a core file if there is one, and finally an executable file if -there is one of those. - -When you specify a new target in a given stratum, it replaces any target -previously in that stratum. - -To get rid of a target without replacing it, use the @code{detach} -command. The related command @code{attach} provides you with a way of -choosing a particular running process as a new target. @xref{Attach}. - -@node Target Commands, Remote, Active Targets, Targets -@section Commands for Managing Targets - -@table @code -@item target @var{type} @var{parameters} -Connects the _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 will not repeat if you press @key{RET} again -after executing the command. - -@item help target -@kindex 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}). - -@item help target @var{name} -Describe a particular target, including any parameters necessary to -select it. -@end table - -Here are some common targets (available, or not, depending on the _GDBN__ -configuration): - -@table @code -@item target exec @var{prog} -@kindex target exec -An executable file. @samp{target exec @var{prog}} is the same as -@samp{exec-file @var{prog}}. - -@item target core @var{filename} -@kindex target core -A core dump file. @samp{target core @var{filename}} is the same as -@samp{core-file @var{filename}}. - -@item target remote @var{dev} -@kindex target remote -Remote serial target in _GDBN__-specific protocol. The argument @var{dev} -specifies what serial device to use for the connection (e.g. -@file{/dev/ttya}). @xref{Remote}. - -_if__(_AMD29K__) -@item target amd-eb @var{dev} @var{speed} @var{PROG} -@kindex target amd-eb -@cindex AMD EB29K -Remote PC-resident AMD EB29K board, attached over serial lines. -@var{dev} is the serial device, as for @code{target remote}; -@var{speed} allows you to specify the linespeed; and @var{PROG} is the -name of the program to be debugged, as it appears to DOS on the PC. -@xref{EB29K Remote}. - -_fi__(_AMD29K__) -_if__(_I960__) -@item target nindy @var{devicename} -@kindex target nindy -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}. @xref{i960-Nindy Remote}. - -_fi__(_I960__) -_if__(_VXWORKS__) -@item target vxworks @var{machinename} -@kindex target vxworks -A VxWorks system, attached via TCP/IP. The argument @var{machinename} -is the target system's machine name or IP address. -@xref{VxWorks Remote}. -_fi__(_VXWORKS__) -@end table - -_if__(_GENERIC__) -Different targets are available on different configurations of _GDBN__; your -configuration may have more or fewer targets. -_fi__(_GENERIC__) - -@node Remote, , Target Commands, Targets -@section Remote Debugging -@cindex remote debugging - -_if__(_GENERIC__) -@menu -_include__(gdbinv-m.m4)<>_dnl__ -@end menu -_fi__(_GENERIC__) - -If you are trying to debug a program running on a machine that can't run -_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 _GDBN__ have special serial or TCP/IP interfaces -to make this work with particular debugging targets. In addition, -_GDBN__ comes with a generic serial protocol (specific to _GDBN__, but -not specific to any particular target system) which you can use if you -write the remote stubs---the code that will run on the remote system to -communicate with _GDBN__. - -To use the _GDBN__ remote serial protocol, the program to be debugged on -the remote machine needs to contain a debugging stub which talks to -_GDBN__ over the serial line. Several working remote stubs are -distributed with _GDBN__; see the @file{README} file in the _GDBN__ -distribution for more information. - -For details of this communication protocol, see the comments in the -_GDBN__ source file @file{remote.c}. - -To start remote debugging, first run _GDBN__ and specify as an executable file -the program that is running in the remote machine. This tells _GDBN__ how -to find the program's symbols and the contents of its pure text. Then -establish communication using the @code{target remote} command with a device -name as an argument. For example: - -@example -target remote /dev/ttyb -@end example - -@noindent -if the serial line is connected to the device named @file{/dev/ttyb}. This -will stop the remote machine if it is not already stopped. - -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. - -Other remote targets may be available in your -configuration of _GDBN__; use @code{help targets} to list them. - -_if__(_GENERIC__) -@c Text on starting up GDB in various specific cases; it goes up front -@c in manuals configured for any of those particular situations, here -@c otherwise. -_include__(gdbinv-s.m4) -_fi__(_GENERIC__) - -@node Controlling _GDBN__, Sequences, Targets, Top -@chapter Controlling _GDBN__ - -You can alter many aspects of _GDBN__'s interaction with you by using -the @code{set} command. For commands controlling how _GDBN__ displays -data, @pxref{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 -@end menu - -@node Prompt, Editing, Controlling _GDBN__, Controlling _GDBN__ -@section Prompt -@cindex prompt -_GDBN__ indicates its readiness to read a command by printing a string -called the @dfn{prompt}. This string is normally @samp{(_GDBP__)}. You -can change the prompt string with the @code{set prompt} command. For -instance, when debugging _GDBN__ with _GDBN__, it is useful to change -the prompt in one of the _GDBN__<>s so that you can always tell which -one you are talking to. - -@table @code -@item set prompt @var{newprompt} -@kindex set prompt -Directs _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, History, Prompt, Controlling _GDBN__ -@section Command Editing -@cindex readline -@cindex command line editing -_GDBN__ reads its input commands via the @dfn{readline} interface. This -GNU library provides consistent behavior for programs which provide a -command line interface to the user. Advantages are @code{emacs}-style -or @code{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 _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, Screen Size, Editing, Controlling _GDBN__ -@section Command History -@table @code -@cindex history substitution -@cindex history file -@kindex set history filename -@item set history filename @var{fname} -Set the name of the _GDBN__ command history file to @var{fname}. This is -the file from which _GDBN__ will read an initial command history -list or to which it will write this list when it exits. This list is -accessed 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} 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 _GDBN__ will keep 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{!}. -@iftex -(@xref{Event Designators}.) -@end iftex -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 will 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 @code{emacs} -or @code{vi} may wish to read it. -@iftex -@xref{Command Line Editing}. -@end iftex - -@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 _GDBN__ history parameters. -@code{show history} by itself displays all four states. -@c @end group - -@end table - -@table @code -@kindex show commands -@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, Numbers, History, Controlling _GDBN__ -@section Screen Size -@cindex size of screen -@cindex pauses in output -Certain commands to _GDBN__ may produce large amounts of information -output to the screen. To help you read all of it, _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. _GDBN__ also uses the screen -width setting to determine when to wrap lines of output. Depending on -what is being printed, it tries to break the line at a readable place, -rather than simply letting it overflow onto the following line. - -Normally _GDBN__ knows the size of the screen from 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 -@item set height @var{lpp} -@itemx show height -@itemx set width @var{cpl} -@itemx show width -@kindex set height -@kindex set width -@kindex show width -@kindex show height -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, _GDBN__ will 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. -@end table - -@node Numbers, Messages/Warnings, Screen Size, Controlling _GDBN__ -@section Numbers -@cindex number representation -@cindex entering numbers -You can always enter numbers in octal, decimal, or hexadecimal in _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 radix -@item set radix @var{base} -Set the default base for numeric input and display. Supported choices -for @var{base} are decimal 2, 8, 10, 16. @var{base} must itself be -specified either unambiguously or using the current default radix; for -example, any of - -@example -set radix 1010 -set radix 012 -set radix 10. -set radix 0xa -@end example - -@noindent -will set the base to decimal. On the other hand, @samp{set radix 10} -will leave the radix unchanged no matter what it was. - -@kindex show radix -@item show radix -Display the current default base for numeric input and display. - -@end table - -@node Messages/Warnings, , Numbers, Controlling _GDBN__ -@section Optional Warnings and Messages -By default, _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. -It will make _GDBN__ tell you when it does a lengthy internal operation, so -you won't 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 -(@pxref{Files}, in the description of the command -@code{symbol-file}). -@c The following is the right way to do it, but emacs 18.55 doesn't support -@c @ref, and neither the emacs lisp manual version of texinfmt or makeinfo -@c is released. -@ignore -see @code{symbol-file} in @ref{Files}). -@end ignore - -@table @code -@kindex set verbose -@item set verbose on -Enables _GDBN__'s output of certain informational messages. - -@item set verbose off -Disables _GDBN__'s 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 _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}). - -@table @code -@kindex set complaints -@item set complaints @var{limit} -Permits _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 _GDBN__ is permitted to produce. -@end table - -By default, _GDBN__ is cautious, and asks what sometimes seem 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 -(_GDBP__) run -The program being debugged has been started already. -Start it from the beginning? (y or n) -@end example - -If you're 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). - -@item show confirm -@kindex show confirm -Displays state of confirmation requests. -@end table - -@c FIXME this doesn't really belong here. But where *does* it belong? -@cindex reloading symbols -Some systems allow individual object files that make up your program to -be replaced without stopping and restarting your program. -_if__(_VXWORKS__) -For example, in VxWorks you can simply recompile a defective object file -and keep on running. -_fi__(_VXWORKS__) -If you're running on one of these systems, you can allow _GDBN__ to -reload the symbols for automatically relinked modules:@refill -@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 -Don't replace symbol definitions when re-encountering object files of -the same name. This is the default state; if you're not running on a -system that permits automatically relinking modules, you should leave -@code{symbol-reloading} off, since otherwise _GDBN__ may discard symbols -when linking large programs, that may contain several modules (from -different directories or libraries) with the same name. - -@item show symbol-reloading -Show the current @code{on} or @code{off} setting. -@end table - -@node Sequences, Emacs, Controlling _GDBN__, Top -@chapter Canned Sequences of Commands - -Aside from breakpoint commands (@pxref{Break Commands}), _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 -* Command Files:: Command Files -* Output:: Commands for Controlled Output -@end menu - -@node Define, Command Files, Sequences, Sequences -@section User-Defined Commands - -@cindex user-defined command -A @dfn{user-defined command} is a sequence of _GDBN__ commands to which you -assign a new name as a command. This is done with the @code{define} -command. - -@table @code -@item define @var{commandname} -@kindex define -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 _GDBN__ command lines, -which are given following the @code{define} command. The end of these -commands is marked by a line containing @code{end}. - -@item document @var{commandname} -@kindex document -Give documentation to the user-defined command @var{commandname}. 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} will print -the documentation you have specified. - -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. - -@item help user-defined -@kindex help user-defined -List all user-defined commands, with the first line of the documentation -(if any) for each. - -@item info user -@itemx info user @var{commandname} -@kindex info user -Display the _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 - -User-defined commands do not take arguments. When they are executed, the -commands of the definition are not printed. An error in any command -stops execution of the user-defined command. - -Commands that would ask for confirmation if used interactively proceed -without asking when used inside a user-defined command. Many _GDBN__ commands -that normally print messages to say what they are doing omit the messages -when used in a user-defined command. - -@node Command Files, Output, Define, Sequences -@section Command Files - -@cindex command files -A command file for _GDBN__ is a file of lines that are _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__} -When you start _GDBN__, it automatically executes commands from its -@dfn{init files}. These are files named @file{_GDBINIT__}. _GDBN__ -reads the init file (if any) in your home directory and then the init -file (if any) in the current working directory. (The init files are not -executed if you use the @samp{-nx} option; @pxref{Mode Options}.) You -can also request the execution of a command file with the @code{source} -command: - -@table @code -@item source @var{filename} -@kindex source -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 _GDBN__ commands that -normally print messages to say what they are doing omit the messages -when called from command files. - -@node Output, , Command Files, Sequences -@section Commands for Controlled Output - -During the execution of a command file or a user-defined command, normal -_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 -@item echo @var{text} -@kindex echo -@c I don't consider backslash-space a standard C escape sequence -@c because it's 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. @b{No -newline will be 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 outputting a string with spaces at the -beginning or the end, since leading and trailing spaces are otherwise -trimmed from all arguments. Thus, to print @samp{@ and foo =@ }, use the -command @samp{echo \@ and foo = \@ }. -@c FIXME: verify hard copy actually issues enspaces for '@ '! Will this -@c confuse texinfo? - -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 - -@item output @var{expression} -@kindex output -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} 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}; @pxref{Output formats}, for more -information. - -@item printf @var{string}, @var{expressions}@dots{} -@kindex printf -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 the program were to execute - -@example -printf (@var{string}, @var{expressions}@dots{}); -@end example - -For example, you can print two values in hex like this: - -@example -printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo -@end example - -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 Emacs, _GDBN__ Bugs, Sequences, Top -@chapter Using _GDBN__ under GNU Emacs - -@cindex emacs -A special interface allows you to use GNU Emacs to view (and -edit) the source files for the program you are debugging with -_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 -_GDBN__ as a subprocess of Emacs, with input and output through a newly -created Emacs buffer. - -Using _GDBN__ under Emacs is just like using _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 _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 -_GDBN__ displays source code through Emacs. -@end itemize - -Each time _GDBN__ displays a stack frame, Emacs automatically finds the -source file for that frame and puts an arrow (_0__@samp{=>}_1__) at the -left margin of the current line. Emacs uses a separate buffer for -source display, and splits the window to show both your _GDBN__ session -and the source. - -Explicit _GDBN__ @code{list} or search commands still produce output as -usual, but you probably will have no reason to use them. - -@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 will not -appear to show your source. _GDBN__ can find programs by searching your -environment's @code{PATH} variable, so the _GDBN__ input and output -session will proceed normally; but Emacs doesn't get enough information -back from _GDBN__ to locate the source files in this situation. To -avoid this problem, either start _GDBN__ mode from the directory where -your program resides, or specify a full path name when prompted for the -@kbd{M-x gdb} argument. - -A similar confusion can result if you use the _GDBN__ @code{file} command to -switch to debugging a program in some other location, from an existing -_GDBN__ buffer in Emacs. -@end quotation - -By default, @kbd{M-x gdb} calls the program called @file{gdb}. If -you need to call _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{ESC ESC}, or typed in the @code{*scratch*} buffer, or -in your @file{.emacs} file) will make Emacs call the program named -``@code{mygdb}'' instead. - -In the _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' _GDBN__ Mode. - -@item M-s -Execute to another source line, like the _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 _GDBN__ @code{next} command. Then update the display window -to show the current file and location. - -@item M-i -Execute one instruction, like the _GDBN__ @code{stepi} command; update -display window accordingly. - -@item M-x gdb-nexti -Execute to next instruction, using the _GDBN__ @code{nexti} command; update -display window accordingly. - -@item C-c C-f -Execute until exit from the selected stack frame, like the _GDBN__ -@code{finish} command. - -@item M-c -Continue execution of the program, like the _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 GNU Emacs Manual}), -like the _GDBN__ @code{up} command. @emph{Warning:} In Emacs v19, this -command is @kbd{C-c C-u}.@refill - -@item M-d -Go down the number of frames indicated by the numeric argument, like the -_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 _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 on the fly 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 &} will both indicate that you -wish special formatting, and act 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 _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 _GDBN__ buffer, to -request a frame display; when you run under Emacs, this will recreate -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 _GDBN__ -communicates with Emacs in terms of line numbers. If you add or -delete lines from the text, the line numbers that _GDBN__ knows will cease -to correspond properly to the code. - -@c The following dropped because Epoch is nonstandard. Reactivate -@c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990 -@ignore -@kindex emacs epoch environment -@kindex epoch -@kindex inspect - -Version 18 of 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 - -@node _GDBN__ Bugs, Renamed Commands, Emacs, Top -@chapter Reporting Bugs in _GDBN__ -@cindex Bugs in _GDBN__ -@cindex Reporting Bugs in _GDBN__ - -Your bug reports play an essential role in making _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 _GDBN__ work better. Bug -reports are your contribution to the maintenance of _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, Bug Reporting, _GDBN__ Bugs, _GDBN__ Bugs -@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 -@item -@cindex Fatal Signal -@cindex Core Dump -If the debugger gets a fatal signal, for any input whatever, that is a -_GDBN__ bug. Reliable debuggers never crash. - -@item -@cindex error on Valid Input -If _GDBN__ produces an error message for valid input, that is a bug. - -@item -@cindex Invalid Input -If _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 _GDBN__ are welcome in any case. -@end itemize - -@node Bug Reporting, , Bug Criteria, _GDBN__ Bugs -@section How to Report Bugs -@cindex Bug Reports -@cindex _GDBN__ Bugs, Reporting - -A number of companies and individuals offer support for GNU products. -If you obtained _GDBN__ from a support organization, we recommend you -contact that organization first. - -Contact information for many support companies and individuals is -available in the file @file{etc/SERVICE} in the GNU Emacs distribution. - -In any event, we also recommend that you send bug reports for _GDBN__ to one -of these addresses: - -@example -bug-gdb@@prep.ai.mit.edu -@{ucbvax|mit-eddie|uunet@}!prep.ai.mit.edu!bug-gdb -@end example - -@strong{Do not send bug reports to @samp{info-gdb}, or to -@samp{help-gdb}, or to any newsgroups.} Most users of _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 -GNU Debugger Bugs -Free Software Foundation -545 Tech Square -Cambridge, MA 02139 -@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 don't matter. Thus, you might -assume that the name of the variable you use in an example does not matter. -Well, probably it doesn't, 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 if it is new to us. It isn't as important what happens if -the bug is already known. Therefore, always write your bug reports on -the assumption that the bug has not been reported previously. - -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 _GDBN__. _GDBN__ announces it if you start with no -arguments; you can also print it at any time using @code{show version}. - -Without this, we won't know whether there is any point in looking for -the bug in the current version of _GDBN__. - -@item -A complete input script, and all necessary source files, that will -reproduce the bug. - -@item -What compiler (and its version) was used to compile _GDBN__---e.g. -``_GCC__-1.37.1''. - -@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 won't omit something important, list them all. - -If we were to try to guess the arguments, we would probably guess wrong -and then we might not encounter the bug. - -@item -The type of machine you are using, and the operating system name and -version number. - -@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 _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. We are human, after all. 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 _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 _GDBN__ source, send us context -diffs. If you even discuss something in the _GDBN__ source, refer to -it by context, not by line number. - -The line numbers in our development sources won't 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, etc. - -However, simplification is not vital; if you don't 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 don't 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 _GDBN__ it is very hard to -construct an example that will make the program follow a certain path -through the code. If you don't send us the example, we won't be able -to construct one, so we won't be able to verify that the bug is fixed. - -And if we can't understand what bug you are trying to fix, or why your -patch should be an improvement, we won't 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 can't guess right about such -things without first using the debugger to find the facts. -@end itemize - -@iftex -@include rdl-apps.texi -@end iftex - -@node Renamed Commands, Installing _GDBN__, _GDBN__ Bugs, Top -@appendix Renamed Commands - -The following commands were renamed in _GDBN__ 4.0, in order to make the -command set as a whole more consistent and easier to use and remember: - -@kindex add-syms -@kindex delete environment -@kindex info copying -@kindex info convenience -@kindex info directories -@kindex info editing -@kindex info history -@kindex info targets -@kindex info values -@kindex info version -@kindex info warranty -@kindex set addressprint -@kindex set arrayprint -@kindex set prettyprint -@kindex set screen-height -@kindex set screen-width -@kindex set unionprint -@kindex set vtblprint -@kindex set demangle -@kindex set asm-demangle -@kindex set sevenbit-strings -@kindex set array-max -@kindex set caution -@kindex set history write -@kindex show addressprint -@kindex show arrayprint -@kindex show prettyprint -@kindex show screen-height -@kindex show screen-width -@kindex show unionprint -@kindex show vtblprint -@kindex show demangle -@kindex show asm-demangle -@kindex show sevenbit-strings -@kindex show array-max -@kindex show caution -@kindex show history write -@kindex unset - -@ifinfo -@example -OLD COMMAND NEW COMMAND ---------------- ------------------------------- -add-syms add-symbol-file -delete environment unset environment -info convenience show convenience -info copying show copying -info directories show directories -info editing show commands -info history show values -info targets help target -info values show values -info version show version -info warranty show warranty -set/show addressprint set/show print address -set/show array-max set/show print elements -set/show arrayprint set/show print array -set/show asm-demangle set/show print asm-demangle -set/show caution set/show confirm -set/show demangle set/show print demangle -set/show history write set/show history save -set/show prettyprint set/show print pretty -set/show screen-height set/show height -set/show screen-width set/show width -set/show sevenbit-strings set/show print sevenbit-strings -set/show unionprint set/show print union -set/show vtblprint set/show print vtbl - -unset [No longer an alias for delete] -@end example -@end ifinfo - -@tex -\vskip \parskip\vskip \baselineskip -\halign{\tt #\hfil &\qquad#&\tt #\hfil\cr -{\bf Old Command} &&{\bf New Command}\cr -add-syms &&add-symbol-file\cr -delete environment &&unset environment\cr -info convenience &&show convenience\cr -info copying &&show copying\cr -info directories &&show directories \cr -info editing &&show commands\cr -info history &&show values\cr -info targets &&help target\cr -info values &&show values\cr -info version &&show version\cr -info warranty &&show warranty\cr -set{\rm / }show addressprint &&set{\rm / }show print address\cr -set{\rm / }show array-max &&set{\rm / }show print elements\cr -set{\rm / }show arrayprint &&set{\rm / }show print array\cr -set{\rm / }show asm-demangle &&set{\rm / }show print asm-demangle\cr -set{\rm / }show caution &&set{\rm / }show confirm\cr -set{\rm / }show demangle &&set{\rm / }show print demangle\cr -set{\rm / }show history write &&set{\rm / }show history save\cr -set{\rm / }show prettyprint &&set{\rm / }show print pretty\cr -set{\rm / }show screen-height &&set{\rm / }show height\cr -set{\rm / }show screen-width &&set{\rm / }show width\cr -set{\rm / }show sevenbit-strings &&set{\rm / }show print sevenbit-strings\cr -set{\rm / }show unionprint &&set{\rm / }show print union\cr -set{\rm / }show vtblprint &&set{\rm / }show print vtbl\cr -\cr -unset &&\rm(No longer an alias for delete)\cr -} -@end tex - -@node Installing _GDBN__, Copying, Renamed Commands, Top -@appendix Installing _GDBN__ -@cindex configuring _GDBN__ -@cindex installation - -_GDBN__ comes with a @code{configure} script that automates the process -of preparing _GDBN__ for installation; you can then use @code{make} to -build the @code{_GDBP__} program. - -The _GDBP__ distribution includes all the source code you need for -_GDBP__ in a single directory @file{gdb-_GDB_VN__}. That directory in turn -contains: - -@table @code -@item gdb-_GDB_VN__/configure -Overall script for configuring _GDBN__ and all its supporting libraries. - -@item gdb-_GDB_VN__/gdb -the source specific to _GDBN__ itself - -@item gdb-_GDB_VN__/bfd -source for the Binary File Descriptor Library - -@item gdb-_GDB_VN__/include -GNU include files - -@item gdb-_GDB_VN__/libiberty -source for the @samp{-liberty} free software library - -@item gdb-_GDB_VN__/readline -source for the GNU command-line interface -@end table -@noindent -Each of these directories has its own @code{configure} script, which are -used by the overall @code{configure} script in @file{gdb-_GDB_VN__}. - -It is most convenient to run @code{configure} from the @file{gdb-_GDB_VN__} -directory. The simplest way to configure and build _GDBN__ is the -following: -@example -cd gdb-_GDB_VN__ -./configure @var{host} -make -@end example -@noindent -where @var{host} is something like @samp{sun4} or @samp{decstation}, that -identifies the platform where _GDBN__ will run. This builds the three -libraries @file{bfd}, @file{readline}, and @file{libiberty}, then -@code{gdb} itself. The configured source files, and the binaries, are -left in the corresponding source directories. - -You can install @code{_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; some systems -refuse to let _GDBN__ debug child processes whose programs are not -readable, and _GDBN__ uses the shell to start your program. - -@menu -* Subdirectories:: Configuration subdirectories -* Config Names:: Specifying names for hosts and targets -* configure Options:: Summary of options for configure -* Formatting Documentation:: How to format and print _GDBN__ documentation -@end menu - - -@node Subdirectories, Config Names, Installing _GDBN__, Installing _GDBN__ -@section Configuration Subdirectories -If you want to run _GDBN__ versions for several host or target machines, -you'll need a different _GDBP__ 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. If your -@code{make} program handles the @samp{VPATH} feature (GNU @code{make} -does), running @code{make} in each of these directories then builds the -_GDBP__ program specified there. - -@code{configure} creates these subdirectories for you when you -simultaneously specify several configurations; but it's a good habit -even for a single configuration. You can specify the use of -subdirectories using the @samp{+subdirs} option (abbreviated -@samp{+sub}). For example, you can build _GDBN__ on a Sun 4 as follows: - -@example -@group -cd gdb-_GDB_VN__ -./configure +sub sun4 -cd Host-sparc-sun-sunos4/Target-sparc-sun-sunos4 -make -@end group -@end example - -When @code{configure} uses subdirectories to build programs or -libraries, it creates nested directories -@file{Host-@var{host}/Target-@var{target}}. (As you see in the example, -the names used for @var{host} and @var{target} may be expanded from your -@code{configure} argument; @pxref{Config Names}). @code{configure} uses -these two directory levels because _GDBN__ can be configured for -cross-compiling: _GDBN__ can run on one machine (the host) while -debugging programs that run on another machine (the target). You -specify cross-debugging targets by giving the -@samp{+target=@var{target}} option to @code{configure}. Specifying only -hosts still gives you two levels of subdirectory for each host, with the -same configuration suffix on both; that is, if you give any number of -hosts but no targets, _GDBN__ will be configured for native debugging on -each host. On the other hand, whenever you specify both hosts and -targets on the same command line, @code{configure} creates all -combinations of the hosts and targets you list.@refill - -When you run @code{make} to build a program or library, you must run it -in a configured directory. If you made a single configuration, -without subdirectories, run @code{make} in the source directory. -If you have @file{Host-@var{host}/Target-@var{target}} subdirectories, -run @code{make} in those subdirectories. - -Each @code{configure} and @code{Makefile} under each source directory -runs recursively, so that typing @code{make} in @file{gdb-_GDB_VN__} (or in a -@file{gdb-_GDB_VN__/Host-@var{host}/Target-@var{target}} subdirectory) -builds all the required libraries, then _GDBN__.@refill - -If you run @code{configure} from a directory (such as @file{gdb-_GDB_VN__}) that -contains source directories for multiple libraries or programs, -@code{configure} creates the @file{Host-@var{host}/Target-@var{target}} -subdirectories in each library or program's source directory. For -example, typing: -@example -cd gdb-_GDB_VN__ -configure sun4 +target=vxworks960 -@end example -@noindent -creates the following directories: -@smallexample -gdb-_GDB_VN__/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -gdb-_GDB_VN__/bfd/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -gdb-_GDB_VN__/gdb/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -gdb-_GDB_VN__/libiberty/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -gdb-_GDB_VN__/readline/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -@end smallexample -@noindent -The @code{Makefile} in -@smallexample -gdb-_GDB_VN__/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -@end smallexample -@noindent -will @code{cd} to the appropriate lower-level directories, for example: -@smallexample -gdb-_GDB_VN__/bfd/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks -@end smallexample -@noindent -building each in turn. - -When you have multiple hosts or targets configured, 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. - - -@iftex -@c FIXME isn't there something kinder, gentler than @page? -@page -@end iftex -@node Config Names, configure Options, Subdirectories, Installing _GDBN__ -@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 in a @code{+target=@var{target}} option, but the full name of that -configuration specifies that the architecture is @samp{sparc}, the -vendor is @samp{sun}, and the operating system is @samp{sunos4}. - -@iftex -@c I know this is ugly, but @group is useless except in examples now... -@c (using texinfo 2.52 or so) -@page -@end iftex - -The following table shows all the architectures, hosts, and OS prefixes -that @code{configure} recognizes in _GDBN__ _GDB_VN__. Entries in the ``OS -prefix'' column ending in a @samp{*} may be followed by a release number. - -@ifinfo -@example - -ARCHITECTURE VENDOR OS prefix -------------+-------------+------------- - | | - 580 | altos | aix* - a29k | amdahl | amigados - alliant | aout | aout - arm | apollo | bout - c1 | att | bsd* - c2 | bull | coff - cray2 | bcs | ctix* - h8300 | bout | dynix* - i386 | cbm | esix* - i860 | coff | hpux* - i960 | convergent | irix* - m68000 | convex | isc* - m68k | cray | kern - m88k | dec | mach* - mips | encore | newsos* - ns32k | gould | nindy* - pyramid | hp | none - romp | ibm | osf* - rs6000 | intel | sco* - rtpc | isi | sunos* - sparc | little | svr4 - tahoe | mips | sym* - tron | motorola | sysv* - vax | ncr | ultrix* - xmp | next | unicos - ymp | none | unos* - | nyu | uts - | sco | v88r* - | sequent | vms* - | sgi | vxworks* - | sony | - | sun | - | unicom | - | utek | - | wrs | - -@end example -@quotation -@emph{Warning:} Many combinations of architecture, vendor, and OS are -untested. -@end quotation -@end ifinfo -@c FIXME: this table is probably screwed in @smallbook. Try setting -@c FIXME...smallbook fonts? -@tex -%\vskip\parskip -\vskip \baselineskip -\halign{\hskip\parindent\tt #\hfil &\qquad#&\tt #\hfil &\qquad#&\tt -#\hfil &\qquad\qquad\it #\hfil\cr -{\bf Architecture} &&{\bf Vendor} &&{\bf OS prefix}\cr -\multispan5\hrulefill\cr - 580 && altos && aix* \cr - a29k && amdahl && amigados\cr - alliant && aout && aout \cr - arm && apollo && bout \cr - c1 && att && bsd* \cr - c2 && bull && coff \cr - cray2 && bcs && ctix* \cr - h8300 && bout && dynix* \cr - i386 && cbm && esix* \cr - i860 && coff && hpux* &Warning: \cr - i960 && convergent && irix* &Many combinations \cr - m68000 && convex && isc* &of architecture, vendor \cr - m68k && cray && kern &and OS are untested. \cr - m88k && dec && mach* \cr - mips && encore && newsos* \cr - ns32k && gould && nindy* \cr - pyramid && hp && none \cr - romp && ibm && osf* \cr - rs6000 && intel && sco* \cr - rtpc && isi && sunos* \cr - sparc && little && svr4 \cr - tahoe && mips && sym* \cr - tron && motorola && sysv* \cr - vax && ncr && ultrix* \cr - xmp && next && unicos \cr - ymp && none && unos* \cr - && nyu && uts \cr - && sco && v88r* \cr - && sequent && vms* \cr - && sgi && vxworks*\cr - && sony &&\cr - && sun &&\cr - && unicom &&\cr - && utek &&\cr - && wrs &&\cr -} -@end tex - -The @code{configure} script accompanying _GDBN__ _GDB_VN__ 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: -@example -% sh config.sub sun4 -sparc-sun-sunos4 -% sh config.sub sun3 -m68k-sun-sunos4 -% sh config.sub decstation -mips-dec-ultrix -% sh config.sub hp300bsd -m68k-hp-bsd -% sh config.sub i386v -i386-none-sysv -% sh config.sub i486v -*** No vendor: configuration `i486v' not recognized -@end example - -@node configure Options, Formatting Documentation, Config Names, Installing _GDBN__ -@section @code{configure} Options - -Here is a summary of all the @code{configure} options and arguments that -you might use for building _GDBN__: - -@example -configure @r{[}+destdir=@var{dir}@r{]} @r{[}+subdirs@r{]} @r{[}+norecur@r{]} @r{[}+rm@r{]} - @r{[}+target=@var{target}@dots{}@r{]} @var{host}@dots{} -@end example -@noindent -You may introduce options with the character @samp{-} rather than -@samp{+} if you prefer; but you may abbreviate option names if you use -@samp{+}. - -@table @code -@item +destdir=@var{dir} -@var{dir} is an installation directory @emph{path prefix}. After you -configure with this option, @code{make install} will install _GDBN__ as -@file{@var{dir}/bin/_GDBP__}, and the libraries in @file{@var{dir}/lib}. -If you specify @samp{+destdir=/usr/local}, for example, @code{make -install} creates @file{/usr/local/bin/gdb}.@refill - -@item +subdirs -Write configuration specific files in subdirectories of the form -@example -Host-@var{host}/Target-@var{target} -@end example -@noindent -(and configure the @code{Makefile} to write binaries there too). -Without this option, if you specify only one configuration for _GDBN__, -@code{configure} will use the same directory for source, configured -files, and binaries. This option is used automatically if you specify -more than one @var{host} or more than one @samp{+target=@var{target}} -option on the @code{configure} command line. - -@item +norecur -Configure only the directory where @code{configure} is executed; do not -propagate configuration to subdirectories. - -@item +rm -Remove the configuration that the other arguments specify. - -@c This doesn't work (yet if ever). FIXME. -@c @item +parse=@var{lang} @dots{} -@c Configure the _GDBN__ expression parser to parse the listed languages. -@c @samp{all} configures _GDBN__ for all supported languages. To get a -@c list of all supported languages, omit the argument. Without this -@c option, _GDBN__ is configured to parse all supported languages. - -@item +target=@var{target} @dots{} -Configure _GDBN__ for cross-debugging programs running on each specified -@var{target}. You may specify as many @samp{+target} options as you -wish. Without this option, _GDBN__ is configured to debug programs that -run on the same machine (@var{host}) as _GDBN__ itself. - -There is no convenient way to generate a list of all available targets. - -@item @var{host} @dots{} -Configure _GDBN__ to run on each specified @var{host}. You may specify as -many host names as you wish. - -There is no convenient way to generate a list of all available hosts. -@end table - -@noindent -@code{configure} accepts other options, for compatibility with -configuring other GNU tools recursively; but these are the only -options that affect _GDBN__ or its supporting libraries. - -@node Formatting Documentation, , configure Options, Installing _GDBN__ -@section Formatting the Documentation - -@cindex _GDBN__ reference card -@cindex reference card -The _GDBN__ _GDB_VN__ release includes an already-formatted reference card, -ready for printing on a PostScript printer, as @file{gdb-_GDB_VN__/gdb/refcard.ps}. -It uses the most common PostScript fonts: the Times family, Courier, and -Symbol. If you have a PostScript printer, you can print the reference -card by just sending @file{refcard.ps} to the printer. - -The release also includes the online Info version of this manual already -formatted: the main Info file is @file{gdb-_GDB_VN__/gdb/gdb.info}, and it -refers to subordinate files matching @samp{gdb.info*} in the same -directory. - -If you want to make these Info files yourself from the _GDBN__ manual's -source, you need the GNU @code{makeinfo} program. Once you have it, you -can type -@example -cd gdb-_GDB_VN__/gdb -make gdb.info -@end example -@noindent -to make the Info file. - -If you want to format and print copies of the manual, you need several -things: -@itemize @bullet -@item -@TeX{}, the public domain typesetting program written by Donald Knuth, -must be installed on your system and available through your execution -path. -@item -@file{gdb-_GDB_VN__/texinfo}: @TeX{} macros defining the GNU -Documentation Format. -@item -@emph{A @sc{dvi} output program.} @TeX{} doesn't actually make marks on -paper; it produces output files called @sc{dvi} files. If your system -has @TeX{} installed, chances are it has a program for printing out -these files; one popular example is @code{dvips}, which can print -@sc{dvi} files on PostScript printers. -@end itemize -@noindent -Once you have these things, you can type -@example -cd gdb-_GDB_VN__/gdb -make gdb.dvi -@end example -@noindent -to format the text of this manual, and print it with the usual output -method for @TeX{} @sc{dvi} files at your site. - -If you want to print the reference card, but don't have a PostScript -printer, or you want to use Computer Modern fonts instead, -you can still print it if you have @TeX{}. Format the reference card by typing -@example -cd gdb-_GDB_VN__/gdb -make refcard.dvi -@end example -@noindent - -The _GDBN__ reference card is designed to print in 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. - - -@node Copying, Index, Installing _GDBN__, Top -@unnumbered GNU GENERAL PUBLIC LICENSE -@center Version 2, June 1991 - -@display -Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. -675 Mass Ave, Cambridge, MA 02139, USA - -Everyone is permitted to copy and distribute verbatim copies -of this license document, but changing it is not allowed. -@end display - -@unnumberedsec Preamble - - The licenses for most software are designed to take away your -freedom to share and change it. By contrast, the GNU General Public -License is intended to guarantee your freedom to share and change free -software---to make sure the software is free for all its users. This -General Public License applies to most of the Free Software -Foundation's software and to any other program whose authors commit to -using it. (Some other Free Software Foundation software is covered by -the GNU Library General Public License instead.) You can apply it to -your programs, too. - - When we speak of free software, we are referring to freedom, not -price. Our General Public Licenses are designed to make sure that you -have the freedom to distribute copies of free software (and charge for -this service if you wish), that you receive source code or can get it -if you want it, that you can change the software or use pieces of it -in new free programs; and that you know you can do these things. - - To protect your rights, we need to make restrictions that forbid -anyone to deny you these rights or to ask you to surrender the rights. -These restrictions translate to certain responsibilities for you if you -distribute copies of the software, or if you modify it. - - For example, if you distribute copies of such a program, whether -gratis or for a fee, you must give the recipients all the rights that -you have. You must make sure that they, too, receive or can get the -source code. And you must show them these terms so they know their -rights. - - We protect your rights with two steps: (1) copyright the software, and -(2) offer you this license which gives you legal permission to copy, -distribute and/or modify the software. - - Also, for each author's protection and ours, we want to make certain -that everyone understands that there is no warranty for this free -software. If the software is modified by someone else and passed on, we -want its recipients to know that what they have is not the original, so -that any problems introduced by others will not reflect on the original -authors' reputations. - - Finally, any free program is threatened constantly by software -patents. We wish to avoid the danger that redistributors of a free -program will individually obtain patent licenses, in effect making the -program proprietary. To prevent this, we have made it clear that any -patent must be licensed for everyone's free use or not licensed at all. - - The precise terms and conditions for copying, distribution and -modification follow. - -@iftex -@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION -@end iftex -@ifinfo -@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION -@end ifinfo - -@enumerate -@item -This License applies to any program or other work which contains -a notice placed by the copyright holder saying it may be distributed -under the terms of this General Public License. The ``Program'', below, -refers to any such program or work, and a ``work based on the Program'' -means either the Program or any derivative work under copyright law: -that is to say, a work containing the Program or a portion of it, -either verbatim or with modifications and/or translated into another -language. (Hereinafter, translation is included without limitation in -the term ``modification''.) Each licensee is addressed as ``you''. - -Activities other than copying, distribution and modification are not -covered by this License; they are outside its scope. The act of -running the Program is not restricted, and the output from the Program -is covered only if its contents constitute a work based on the -Program (independent of having been made by running the Program). -Whether that is true depends on what the Program does. - -@item -You may copy and distribute verbatim copies of the Program's -source code as you receive it, in any medium, provided that you -conspicuously and appropriately publish on each copy an appropriate -copyright notice and disclaimer of warranty; keep intact all the -notices that refer to this License and to the absence of any warranty; -and give any other recipients of the Program a copy of this License -along with the Program. - -You may charge a fee for the physical act of transferring a copy, and -you may at your option offer warranty protection in exchange for a fee. - -@item -You may modify your copy or copies of the Program or any portion -of it, thus forming a work based on the Program, and copy and -distribute such modifications or work under the terms of Section 1 -above, provided that you also meet all of these conditions: - -@alphaenumerate -@item -You must cause the modified files to carry prominent notices -stating that you changed the files and the date of any change. - -@item -You must cause any work that you distribute or publish, that in -whole or in part contains or is derived from the Program or any -part thereof, to be licensed as a whole at no charge to all third -parties under the terms of this License. - -@item -If the modified program normally reads commands interactively -when run, you must cause it, when started running for such -interactive use in the most ordinary way, to print or display an -announcement including an appropriate copyright notice and a -notice that there is no warranty (or else, saying that you provide -a warranty) and that users may redistribute the program under -these conditions, and telling the user how to view a copy of this -License. (Exception: if the Program itself is interactive but -does not normally print such an announcement, your work based on -the Program is not required to print an announcement.) -@end alphaenumerate - -These requirements apply to the modified work as a whole. If -identifiable sections of that work are not derived from the Program, -and can be reasonably considered independent and separate works in -themselves, then this License, and its terms, do not apply to those -sections when you distribute them as separate works. But when you -distribute the same sections as part of a whole which is a work based -on the Program, the distribution of the whole must be on the terms of -this License, whose permissions for other licensees extend to the -entire whole, and thus to each and every part regardless of who wrote it. - -Thus, it is not the intent of this section to claim rights or contest -your rights to work written entirely by you; rather, the intent is to -exercise the right to control the distribution of derivative or -collective works based on the Program. - -In addition, mere aggregation of another work not based on the Program -with the Program (or with a work based on the Program) on a volume of -a storage or distribution medium does not bring the other work under -the scope of this License. - -@item -You may copy and distribute the Program (or a work based on it, -under Section 2) in object code or executable form under the terms of -Sections 1 and 2 above provided that you also do one of the following: - -@alphaenumerate -@item -Accompany it with the complete corresponding machine-readable -source code, which must be distributed under the terms of Sections -1 and 2 above on a medium customarily used for software interchange; or, - -@item -Accompany it with a written offer, valid for at least three -years, to give any third party, for a charge no more than your -cost of physically performing source distribution, a complete -machine-readable copy of the corresponding source code, to be -distributed under the terms of Sections 1 and 2 above on a medium -customarily used for software interchange; or, - -@item -Accompany it with the information you received as to the offer -to distribute corresponding source code. (This alternative is -allowed only for noncommercial distribution and only if you -received the program in object code or executable form with such -an offer, in accord with Subsection b above.) -@end alphaenumerate - -The source code for a work means the preferred form of the work for -making modifications to it. For an executable work, complete source -code means all the source code for all modules it contains, plus any -associated interface definition files, plus the scripts used to -control compilation and installation of the executable. However, as a -special exception, the source code distributed need not include -anything that is normally distributed (in either source or binary -form) with the major components (compiler, kernel, and so on) of the -operating system on which the executable runs, unless that component -itself accompanies the executable. - -If distribution of executable or object code is made by offering -access to copy from a designated place, then offering equivalent -access to copy the source code from the same place counts as -distribution of the source code, even though third parties are not -compelled to copy the source along with the object code. - -@item -You may not copy, modify, sublicense, or distribute the Program -except as expressly provided under this License. Any attempt -otherwise to copy, modify, sublicense or distribute the Program is -void, and will automatically terminate your rights under this License. -However, parties who have received copies, or rights, from you under -this License will not have their licenses terminated so long as such -parties remain in full compliance. - -@item -You are not required to accept this License, since you have not -signed it. However, nothing else grants you permission to modify or -distribute the Program or its derivative works. These actions are -prohibited by law if you do not accept this License. Therefore, by -modifying or distributing the Program (or any work based on the -Program), you indicate your acceptance of this License to do so, and -all its terms and conditions for copying, distributing or modifying -the Program or works based on it. - -@item -Each time you redistribute the Program (or any work based on the -Program), the recipient automatically receives a license from the -original licensor to copy, distribute or modify the Program subject to -these terms and conditions. You may not impose any further -restrictions on the recipients' exercise of the rights granted herein. -You are not responsible for enforcing compliance by third parties to -this License. - -@item -If, as a consequence of a court judgment or allegation of patent -infringement or for any other reason (not limited to patent issues), -conditions are imposed on you (whether by court order, agreement or -otherwise) that contradict the conditions of this License, they do not -excuse you from the conditions of this License. If you cannot -distribute so as to satisfy simultaneously your obligations under this -License and any other pertinent obligations, then as a consequence you -may not distribute the Program at all. For example, if a patent -license would not permit royalty-free redistribution of the Program by -all those who receive copies directly or indirectly through you, then -the only way you could satisfy both it and this License would be to -refrain entirely from distribution of the Program. - -If any portion of this section is held invalid or unenforceable under -any particular circumstance, the balance of the section is intended to -apply and the section as a whole is intended to apply in other -circumstances. - -It is not the purpose of this section to induce you to infringe any -patents or other property right claims or to contest validity of any -such claims; this section has the sole purpose of protecting the -integrity of the free software distribution system, which is -implemented by public license practices. Many people have made -generous contributions to the wide range of software distributed -through that system in reliance on consistent application of that -system; it is up to the author/donor to decide if he or she is willing -to distribute software through any other system and a licensee cannot -impose that choice. - -This section is intended to make thoroughly clear what is believed to -be a consequence of the rest of this License. - -@item -If the distribution and/or use of the Program is restricted in -certain countries either by patents or by copyrighted interfaces, the -original copyright holder who places the Program under this License -may add an explicit geographical distribution limitation excluding -those countries, so that distribution is permitted only in or among -countries not thus excluded. In such case, this License incorporates -the limitation as if written in the body of this License. - -@item -The Free Software Foundation may publish revised and/or new versions -of the General Public License from time to time. Such new versions will -be similar in spirit to the present version, but may differ in detail to -address new problems or concerns. - -Each version is given a distinguishing version number. If the Program -specifies a version number of this License which applies to it and ``any -later version'', you have the option of following the terms and conditions -either of that version or of any later version published by the Free -Software Foundation. If the Program does not specify a version number of -this License, you may choose any version ever published by the Free Software -Foundation. - -@item -If you wish to incorporate parts of the Program into other free -programs whose distribution conditions are different, write to the author -to ask for permission. For software which is copyrighted by the Free -Software Foundation, write to the Free Software Foundation; we sometimes -make exceptions for this. Our decision will be guided by the two goals -of preserving the free status of all derivatives of our free software and -of promoting the sharing and reuse of software generally. - -@iftex -@heading NO WARRANTY -@end iftex -@ifinfo -@center NO WARRANTY -@end ifinfo - -@item -BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY -FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN -OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES -PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED -OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF -MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS -TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE -PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, -REPAIR OR CORRECTION. - -@item -IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING -WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR -REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, -INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING -OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED -TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY -YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER -PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE -POSSIBILITY OF SUCH DAMAGES. -@end enumerate - -@iftex -@heading END OF TERMS AND CONDITIONS -@end iftex -@ifinfo -@center END OF TERMS AND CONDITIONS -@end ifinfo - -@page -@unnumberedsec Applying These Terms to Your New Programs - - If you develop a new program, and you want it to be of the greatest -possible use to the public, the best way to achieve this is to make it -free software which everyone can redistribute and change under these terms. - - To do so, attach the following notices to the program. It is safest -to attach them to the start of each source file to most effectively -convey the exclusion of warranty; and each file should have at least -the ``copyright'' line and a pointer to where the full notice is found. - -@smallexample -@var{one line to give the program's name and a brief idea of what it does.} -Copyright (C) 19@var{yy} @var{name of author} - -This program is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 2 of the License, or -(at your option) any later version. - -This program is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with this program; if not, write to the Free Software -Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. -@end smallexample - -Also add information on how to contact you by electronic and paper mail. - -If the program is interactive, make it output a short notice like this -when it starts in an interactive mode: - -@smallexample -Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author} -Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. -This is free software, and you are welcome to redistribute it -under certain conditions; type `show c' for details. -@end smallexample - -The hypothetical commands @samp{show w} and @samp{show c} should show -the appropriate parts of the General Public License. Of course, the -commands you use may be called something other than @samp{show w} and -@samp{show c}; they could even be mouse-clicks or menu items---whatever -suits your program. - -You should also get your employer (if you work as a programmer) or your -school, if any, to sign a ``copyright disclaimer'' for the program, if -necessary. Here is a sample; alter the names: - -@example -Yoyodyne, Inc., hereby disclaims all copyright interest in the program -`Gnomovision' (which makes passes at compilers) written by James Hacker. - -@var{signature of Ty Coon}, 1 April 1989 -Ty Coon, President of Vice -@end example - -This General Public License does not permit incorporating your program into -proprietary programs. If your program is a subroutine library, you may -consider it more useful to permit linking proprietary applications with the -library. If this is what you want to do, use the GNU Library General -Public License instead of this License. - - -@node Index, , Copying, Top -@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\/} and} -\centerline{{\sl\fontname\tensl\/}} -\centerline{are used for emphasis.}\vfill} -\page\colophon -% Blame: pesch@cygnus.com, 28mar91. -@end tex - -@contents -@bye |