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INFO-DIR-SECTION Software development

START-INFO-DIR-ENTRY

* Gdb: (gdb).                     The GNU debugger.

END-INFO-DIR-ENTRY

   This file documents the GNU debugger GDB.

   This is the Ninth Edition, of `Debugging with GDB: the GNU

Source-Level Debugger' for GDB Version 6.8.

   Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,

1998,

1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006

Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.1 or

any later version published by the Free Software Foundation; with the

Invariant Sections being "Free Software" and "Free Software Needs Free

Documentation", with the Front-Cover Texts being "A GNU Manual," and

with the Back-Cover Texts as in (a) below.

   (a) The FSF's Back-Cover Text is: "You are free to copy and modify

this GNU Manual.  Buying copies from GNU Press supports the FSF in

developing GNU and promoting software freedom."

File: gdb.info,  Node: Top,  Next: Summary,  Prev: (dir),  Up: (dir)

Debugging with GDB

******************

This file describes GDB, the GNU symbolic debugger.

   This is the Ninth Edition, for GDB Version 6.8.

   Copyright (C) 1988-2006 Free Software Foundation, Inc.

   This edition of the GDB manual is dedicated to the memory of Fred

Fish.  Fred was a long-standing contributor to GDB and to Free software

in general.  We will miss him.

* Menu:

* Summary::                     Summary of GDB

* Sample Session::              A sample GDB session

* Invocation::                  Getting in and out of GDB

* Commands::                    GDB commands

* Running::                     Running programs under GDB

* Stopping::                    Stopping and continuing

* Stack::                       Examining the stack

* Source::                      Examining source files

* Data::                        Examining data

* Macros::                      Preprocessor Macros

* Tracepoints::                 Debugging remote targets non-intrusively

* Overlays::                    Debugging programs that use overlays

* Languages::                   Using GDB with different languages

* Symbols::                     Examining the symbol table

* Altering::                    Altering execution

* GDB Files::                   GDB files

* Targets::                     Specifying a debugging target

* Remote Debugging::            Debugging remote programs

* Configurations::              Configuration-specific information

* Controlling GDB::             Controlling GDB

* Sequences::                   Canned sequences of commands

* Interpreters::                Command Interpreters

* TUI::                         GDB Text User Interface

* Emacs::                       Using GDB under GNU Emacs

* GDB/MI::                      GDB's Machine Interface.

* Annotations::                 GDB's annotation interface.

* GDB Bugs::                    Reporting bugs in GDB

* Command Line Editing::        Command Line Editing

* Using History Interactively:: Using History Interactively

* Formatting Documentation::    How to format and print GDB documentation

* Installing GDB::              Installing GDB

* Maintenance Commands::        Maintenance Commands

* Remote Protocol::             GDB Remote Serial Protocol

* Agent Expressions::           The GDB Agent Expression Mechanism

* Target Descriptions::         How targets can describe themselves to

                                GDB

* Copying::                     GNU General Public License says

                                how you can copy and share GDB

* GNU Free Documentation License::  The license for this documentation

* Index::                       Index

File: gdb.info,  Node: Summary,  Next: Sample Session,  Prev: Top,  Up: Top

Summary of GDB

**************

The purpose of a debugger such as GDB 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.

   GDB can do four main kinds of things (plus other things in support of

these) to help you catch bugs in the act:

   * Start your program, specifying anything that might affect its

     behavior.

   * Make your program stop on specified conditions.

   * Examine what has happened, when your program has stopped.

   * Change things in your program, so you can experiment with

     correcting the effects of one bug and go on to learn about another.

   You can use GDB to debug programs written in C and C++.  For more

information, see *Note Supported Languages: Supported Languages.  For

more information, see *Note C and C++: C.

   Support for Modula-2 is partial.  For information on Modula-2, see

*Note Modula-2: Modula-2.

   Debugging Pascal programs which use sets, subranges, file variables,

or nested functions does not currently work.  GDB does not support

entering expressions, printing values, or similar features using Pascal

syntax.

   GDB can be used to debug programs written in Fortran, although it

may be necessary to refer to some variables with a trailing underscore.

   GDB can be used to debug programs written in Objective-C, using

either the Apple/NeXT or the GNU Objective-C runtime.

* Menu:

* Free Software::               Freely redistributable software

* Contributors::                Contributors to GDB

File: gdb.info,  Node: Free Software,  Next: Contributors,  Up: Summary

Free Software

=============

GDB is "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 cannot take these freedoms

away from anyone else.

Free Software Needs Free Documentation

======================================

The biggest deficiency in the free software community today is not in

the software--it is the lack of good free documentation that we can

include with the free software.  Many of our most important programs do

not come with free reference manuals and free introductory texts.

Documentation is an essential part of any software package; when an

important free software package does not come with a free manual and a

free tutorial, that is a major gap.  We have many such gaps today.

   Consider Perl, for instance.  The tutorial manuals that people

normally use are non-free.  How did this come about?  Because the

authors of those manuals published them with restrictive terms--no

copying, no modification, source files not available--which exclude

them from the free software world.

   That wasn't the first time this sort of thing happened, and it was

far from the last.  Many times we have heard a GNU user eagerly

describe a manual that he is writing, his intended contribution to the

community, only to learn that he had ruined everything by signing a

publication contract to make it non-free.

   Free documentation, like free software, is a matter of freedom, not

price.  The problem with the non-free manual is not that publishers

charge a price for printed copies--that in itself is fine.  (The Free

Software Foundation sells printed copies of manuals, too.)  The problem

is the restrictions on the use of the manual.  Free manuals are

available in source code form, and give you permission to copy and

modify.  Non-free manuals do not allow this.

   The criteria of freedom for a free manual are roughly the same as for

free software.  Redistribution (including the normal kinds of

commercial redistribution) must be permitted, so that the manual can

accompany every copy of the program, both on-line and on paper.

   Permission for modification of the technical content is crucial too.

When people modify the software, adding or changing features, if they

are conscientious they will change the manual too--so they can provide

accurate and clear documentation for the modified program.  A manual

that leaves you no choice but to write a new manual to document a

changed version of the program is not really available to our community.

   Some kinds of limits on the way modification is handled are

acceptable.  For example, requirements to preserve the original

author's copyright notice, the distribution terms, or the list of

authors, are ok.  It is also no problem to require modified versions to

include notice that they were modified.  Even entire sections that may

not be deleted or changed are acceptable, as long as they deal with

nontechnical topics (like this one).  These kinds of restrictions are

acceptable because they don't obstruct the community's normal use of

the manual.

   However, it must be possible to modify all the _technical_ content

of the manual, and then distribute the result in all the usual media,

through all the usual channels.  Otherwise, the restrictions obstruct

the use of the manual, it is not free, and we need another manual to

replace it.

   Please spread the word about this issue.  Our community continues to

lose manuals to proprietary publishing.  If we spread the word that

free software needs free reference manuals and free tutorials, perhaps

the next person who wants to contribute by writing documentation will

realize, before it is too late, that only free manuals contribute to

the free software community.

   If you are writing documentation, please insist on publishing it

under the GNU Free Documentation License or another free documentation

license.  Remember that this decision requires your approval--you don't

have to let the publisher decide.  Some commercial publishers will use

a free license if you insist, but they will not propose the option; it

is up to you to raise the issue and say firmly that this is what you

want.  If the publisher you are dealing with refuses, please try other

publishers.  If you're not sure whether a proposed license is free,

write to .

   You can encourage commercial publishers to sell more free, copylefted

manuals and tutorials by buying them, and particularly by buying copies

from the publishers that paid for their writing or for major

improvements.  Meanwhile, try to avoid buying non-free documentation at

all.  Check the distribution terms of a manual before you buy it, and

insist that whoever seeks your business must respect your freedom.

Check the history of the book, and try to reward the publishers that

have paid or pay the authors to work on it.

   The Free Software Foundation maintains a list of free documentation

published by other publishers, at

`http://www.fsf.org/doc/other-free-books.html'.

File: gdb.info,  Node: Contributors,  Prev: Free Software,  Up: Summary

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

`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.

     _Plea:_ Additions to this section are particularly welcome.  If you

     or your friends (or enemies, to be evenhanded) have been unfairly

     omitted from this list, we would like to add your names!

   So that they may not regard their many labors as thankless, we

particularly thank those who shepherded GDB through major releases:

Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0); Jim

Blandy (release 4.18); Jason Molenda (release 4.17); Stan Shebs

(release 4.14); Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10,

and 4.9); Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5,

and 4.4); John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); Jim

Kingdon (releases 3.5, 3.4, and 3.3); and Randy Smith (releases 3.2,

3.1, and 3.0).

   Richard Stallman, assisted at various times by Peter TerMaat, Chris

Hanson, and Richard Mlynarik, handled releases through 2.8.

   Michael Tiemann is the author of most of the GNU C++ support in GDB,

with significant additional contributions from Per Bothner and Daniel

Berlin.  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 uses the BFD subroutine library to examine multiple object-file

formats; BFD was a joint project of David V.  Henkel-Wallace, Rich

Pixley, Steve Chamberlain, and John Gilmore.

   David Johnson wrote the original COFF support; Pace Willison did the

original support for encapsulated COFF.

   Brent Benson of Harris Computer Systems contributed DWARF 2 support.

   Adam de Boor and Bradley Davis contributed the ISI Optimum V support.

Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS

support.  Jean-Daniel Fekete contributed Sun 386i support.  Chris

Hanson improved the HP9000 support.  Noboyuki Hikichi and Tomoyuki

Hasei contributed Sony/News OS 3 support.  David Johnson contributed

Encore Umax support.  Jyrki Kuoppala contributed Altos 3068 support.

Jeff Law contributed HP PA and SOM support.  Keith Packard contributed

NS32K support.  Doug Rabson contributed Acorn Risc Machine support.

Bob Rusk contributed Harris Nighthawk CX-UX support.  Chris Smith

contributed Convex support (and Fortran debugging).  Jonathan Stone

contributed Pyramid support.  Michael Tiemann contributed SPARC support.

Tim Tucker contributed support for the Gould NP1 and Gould Powernode.

Pace Willison contributed Intel 386 support.  Jay Vosburgh contributed

Symmetry support.  Marko Mlinar contributed OpenRISC 1000 support.

   Andreas Schwab contributed M68K GNU/Linux 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, Wind River Systems, AMD,

and ARM contributed remote debugging modules for the i960, VxWorks,

A29K UDI, and RDI targets, respectively.

   Brian Fox is the author of the readline libraries providing

command-line editing and command history.

   Andrew Beers of SUNY Buffalo wrote the language-switching code, the

Modula-2 support, and contributed the Languages chapter of this manual.

   Fred Fish wrote most of the support for Unix System Vr4.  He also

enhanced the command-completion support to cover C++ overloaded symbols.

   Hitachi America (now Renesas America), Ltd. sponsored the support for

H8/300, H8/500, and Super-H processors.

   NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx

processors.

   Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and

M32R/D processors.

   Toshiba sponsored the support for the TX39 Mips processor.

   Matsushita sponsored the support for the MN10200 and MN10300

processors.

   Fujitsu sponsored the support for SPARClite and FR30 processors.

   Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware

watchpoints.

   Michael Snyder added support for tracepoints.

   Stu Grossman wrote gdbserver.

   Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made nearly

innumerable bug fixes and cleanups throughout GDB.

   The following people at the Hewlett-Packard Company contributed

support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0

(narrow mode), HP's implementation of kernel threads, HP's aC++

compiler, and the Text User Interface (nee Terminal User Interface):

Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,

Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni.  Kim Haase

provided HP-specific information in this manual.

   DJ Delorie ported GDB to MS-DOS, for the DJGPP project.  Robert

Hoehne made significant contributions to the DJGPP port.

   Cygnus Solutions has sponsored GDB maintenance and much of its

development since 1991.  Cygnus engineers who have worked on GDB

fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin

Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim

Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,

Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek

Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni.  In

addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,

JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug

Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff

Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,

Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin

Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela

Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David

Zuhn have made contributions both large and small.

   Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for

Cygnus Solutions, implemented the original GDB/MI interface.

   Jim Blandy added support for preprocessor macros, while working for

Red Hat.

   Andrew Cagney designed GDB's architecture vector.  Many people

including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick Duffek,

Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei Sakamoto,

Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason Thorpe, Corinna

Vinschen, Ulrich Weigand, and Elena Zannoni, helped with the migration

of old architectures to this new framework.

   Andrew Cagney completely re-designed and re-implemented GDB's

unwinder framework, this consisting of a fresh new design featuring

frame IDs, independent frame sniffers, and the sentinel frame.  Mark

Kettenis implemented the DWARF 2 unwinder, Jeff Johnston the libunwind

unwinder, and Andrew Cagney the dummy, sentinel, tramp, and trad

unwinders.  The architecture-specific changes, each involving a

complete rewrite of the architecture's frame code, were carried out by

Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane

Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel

Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei

Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich

Weigand.

   Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from

Tensilica, Inc. contributed support for Xtensa processors.  Others who

have worked on the Xtensa port of GDB in the past include Steve Tjiang,

John Newlin, and Scott Foehner.

File: gdb.info,  Node: Sample Session,  Next: Invocation,  Prev: Summary,  Up: Top

1 A Sample GDB Session

**********************

You can use this manual at your leisure to read all about GDB.

However, a handful of commands are enough to get started using the

debugger.  This chapter illustrates those commands.

   One of the preliminary versions of GNU `m4' (a generic macro

processor) exhibits the following bug: sometimes, when we change its

quote strings from the default, the commands used to capture one macro

definition within another stop working.  In the following short `m4'

session, we define a macro `foo' which expands to `0000'; we then use

the `m4' built-in `defn' to define `bar' as the same thing.  However,

when we change the open quote string to `' and the close quote

string to `', the same procedure fails to define a new synonym

`baz':

     $ cd gnu/m4

     $ ./m4

     define(foo,0000)

     foo

     0000

     define(bar,defn(`foo'))

     bar

     0000

     changequote(,)

     define(baz,defn(foo))

     baz

     Ctrl-d

     m4: End of input: 0: fatal error: EOF in string

Let us use GDB to try to see what is going on.

     $ gdb m4

     GDB is free software and you are welcome to distribute copies

      of it under certain conditions; type "show copying" to see

      the conditions.

     There is absolutely no warranty for GDB; type "show warranty"

      for details.

     GDB 6.8, Copyright 1999 Free Software Foundation, Inc...

     (gdb)

GDB reads only enough symbol data to know where to find the rest when

needed; as a result, the first prompt comes up very quickly.  We now

tell GDB to use a narrower display width than usual, so that examples

fit in this manual.

     (gdb) set width 70

We need to see how the `m4' built-in `changequote' works.  Having

looked at the source, we know the relevant subroutine is

`m4_changequote', so we set a breakpoint there with the GDB `break'

command.

     (gdb) break m4_changequote

     Breakpoint 1 at 0x62f4: file builtin.c, line 879.

Using the `run' command, we start `m4' running under GDB control; as

long as control does not reach the `m4_changequote' subroutine, the

program runs as usual:

     (gdb) run

     Starting program: /work/Editorial/gdb/gnu/m4/m4

     define(foo,0000)

     foo

     0000

To trigger the breakpoint, we call `changequote'.  GDB suspends

execution of `m4', displaying information about the context where it

stops.

     changequote(,)

     Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)

         at builtin.c:879

     879         if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))

Now we use the command `n' (`next') to advance execution to the next

line of the current function.

     (gdb) n

     882         set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\

      : nil,

`set_quotes' looks like a promising subroutine.  We can go into it by

using the command `s' (`step') instead of `next'.  `step' goes to the

next line to be executed in _any_ subroutine, so it steps into

`set_quotes'.

     (gdb) s

     set_quotes (lq=0x34c78 "", rq=0x34c88 "")

         at input.c:530

     530         if (lquote != def_lquote)

The display that shows the subroutine where `m4' is now suspended (and

its arguments) is called a stack frame display.  It shows a summary of

the stack.  We can use the `backtrace' command (which can also be

spelled `bt'), to see where we are in the stack as a whole: the

`backtrace' command displays a stack frame for each active subroutine.

     (gdb) bt

     #0  set_quotes (lq=0x34c78 "", rq=0x34c88 "")

         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

We step through a few more lines to see what happens.  The first two

times, we can use `s'; the next two times we use `n' to avoid falling

into the `xstrdup' subroutine.

     (gdb) s

     0x3b5c  532         if (rquote != def_rquote)

     (gdb) s

     0x3b80  535         lquote = (lq == nil || *lq == '\0') ?  \

     def_lquote : xstrdup(lq);

     (gdb) n

     536         rquote = (rq == nil || *rq == '\0') ? def_rquote\

      : xstrdup(rq);

     (gdb) n

     538         len_lquote = strlen(rquote);

The last line displayed looks a little odd; we can examine the variables

`lquote' and `rquote' to see if they are in fact the new left and right

quotes we specified.  We use the command `p' (`print') to see their

values.

     (gdb) p lquote

     $1 = 0x35d40 ""

     (gdb) p rquote

     $2 = 0x35d50 ""

`lquote' and `rquote' are indeed the new left and right quotes.  To

look at some context, we can display ten lines of source surrounding

the current line with the `l' (`list') command.

     (gdb) 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

Let us step past the two lines that set `len_lquote' and `len_rquote',

and then examine the values of those variables.

     (gdb) n

     539         len_rquote = strlen(lquote);

     (gdb) n

     540     }

     (gdb) p len_lquote

     $3 = 9

     (gdb) p len_rquote

     $4 = 7

That certainly looks wrong, assuming `len_lquote' and `len_rquote' are

meant to be the lengths of `lquote' and `rquote' respectively.  We can

set them to better values using the `p' command, since it can print the

value of any expression--and that expression can include subroutine

calls and assignments.

     (gdb) p len_lquote=strlen(lquote)

     $5 = 7

     (gdb) p len_rquote=strlen(rquote)

     $6 = 9

Is that enough to fix the problem of using the new quotes with the `m4'

built-in `defn'?  We can allow `m4' to continue executing with the `c'

(`continue') command, and then try the example that caused trouble

initially:

     (gdb) c

     Continuing.

     define(baz,defn(foo))

     baz

     0000

Success!  The new quotes now work just as well as the default ones.  The

problem seems to have been just the two typos defining the wrong

lengths.  We allow `m4' exit by giving it an EOF as input:

     Ctrl-d

     Program exited normally.

The message `Program exited normally.' is from GDB; it indicates `m4'

has finished executing.  We can end our GDB session with the GDB `quit'

command.

     (gdb) quit

File: gdb.info,  Node: Invocation,  Next: Commands,  Prev: Sample Session,  Up: Top

2 Getting In and Out of GDB

***************************

This chapter discusses how to start GDB, and how to get out of it.  The

essentials are:

   * type `gdb' to start GDB.

   * type `quit' or `Ctrl-d' to exit.

* Menu:

* Invoking GDB::                How to start GDB

* Quitting GDB::                How to quit GDB

* Shell Commands::              How to use shell commands inside GDB

* Logging Output::              How to log GDB's output to a file

File: gdb.info,  Node: Invoking GDB,  Next: Quitting GDB,  Up: Invocation

2.1 Invoking GDB

================

Invoke GDB by running the program `gdb'.  Once started, GDB reads

commands from the terminal until you tell it to exit.

   You can also run `gdb' with a variety of arguments and options, to

specify more of your debugging environment at the outset.

   The command-line options described here are designed to cover a

variety of situations; in some environments, some of these options may

effectively be unavailable.

   The most usual way to start GDB is with one argument, specifying an

executable program:

     gdb PROGRAM

You can also start with both an executable program and a core file

specified:

     gdb PROGRAM CORE

   You can, instead, specify a process ID as a second argument, if you

want to debug a running process:

     gdb PROGRAM 1234

would attach GDB to process `1234' (unless you also have a file named

`1234'; GDB does check for a core file first).

   Taking advantage of the second command-line argument requires a

fairly complete operating system; when you use GDB as a remote debugger

attached to a bare board, there may not be any notion of "process", and

there is often no way to get a core dump.  GDB will warn you if it is

unable to attach or to read core dumps.

   You can optionally have `gdb' pass any arguments after the

executable file to the inferior using `--args'.  This option stops

option processing.

     gdb --args gcc -O2 -c foo.c

   This will cause `gdb' to debug `gcc', and to set `gcc''s

command-line arguments (*note Arguments::) to `-O2 -c foo.c'.

   You can run `gdb' without printing the front material, which

describes GDB's non-warranty, by specifying `-silent':

     gdb -silent

You can further control how GDB starts up by using command-line

options.  GDB itself can remind you of the options available.

Type

     gdb -help

to display all available options and briefly describe their use (`gdb

-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 `-x' option is

used.

* Menu:

* File Options::                Choosing files

* Mode Options::                Choosing modes

* Startup::                     What GDB does during startup

File: gdb.info,  Node: File Options,  Next: Mode Options,  Up: Invoking GDB

2.1.1 Choosing Files

--------------------

When GDB starts, it reads any arguments other than options as

specifying an executable file and core file (or process ID).  This is

the same as if the arguments were specified by the `-se' and `-c' (or

`-p') options respectively.  (GDB reads the first argument that does

not have an associated option flag as equivalent to the `-se' option

followed by that argument; and the second argument that does not have

an associated option flag, if any, as equivalent to the `-c'/`-p'

option followed by that argument.)  If the second argument begins with

a decimal digit, GDB will first attempt to attach to it as a process,

and if that fails, attempt to open it as a corefile.  If you have a

corefile whose name begins with a digit, you can prevent GDB from

treating it as a pid by prefixing it with `./', e.g. `./12345'.

   If GDB has not been configured to included core file support, such

as for most embedded targets, then it will complain about a second

argument and ignore it.

   Many options have both long and short forms; both are shown in the

following list.  GDB also recognizes the long forms if you truncate

them, so long as enough of the option is present to be unambiguous.

(If you prefer, you can flag option arguments with `--' rather than

`-', though we illustrate the more usual convention.)

`-symbols FILE'

`-s FILE'

     Read symbol table from file FILE.

`-exec FILE'

`-e FILE'

     Use file FILE as the executable file to execute when appropriate,

     and for examining pure data in conjunction with a core dump.

`-se FILE'

     Read symbol table from file FILE and use it as the executable file.

`-core FILE'

`-c FILE'

     Use file FILE as a core dump to examine.

`-pid NUMBER'

`-p NUMBER'

     Connect to process ID NUMBER, as with the `attach' command.

`-command FILE'

`-x FILE'

     Execute GDB commands from file FILE.  *Note Command files: Command

     Files.

`-eval-command COMMAND'

`-ex COMMAND'

     Execute a single GDB command.

     This option may be used multiple times to call multiple commands.

     It may also be interleaved with `-command' as required.

          gdb -ex 'target sim' -ex 'load' \

             -x setbreakpoints -ex 'run' a.out

`-directory DIRECTORY'

`-d DIRECTORY'

     Add DIRECTORY to the path to search for source and script files.

`-r'

`-readnow'

     Read each symbol file's entire symbol table immediately, rather

     than the default, which is to read it incrementally as it is

     needed.  This makes startup slower, but makes future operations

     faster.

File: gdb.info,  Node: Mode Options,  Next: Startup,  Prev: File Options,  Up: Invoking GDB

2.1.2 Choosing Modes

--------------------

You can run GDB in various alternative modes--for example, in batch

mode or quiet mode.

`-nx'

`-n'

     Do not execute commands found in any initialization files.

     Normally, GDB executes the commands in these files after all the

     command options and arguments have been processed.  *Note Command

     Files: Command Files.

`-quiet'

`-silent'

`-q'

     "Quiet".  Do not print the introductory and copyright messages.

     These messages are also suppressed in batch mode.

`-batch'

     Run in batch mode.  Exit with status `0' after processing all the

     command files specified with `-x' (and all commands from

     initialization files, if not inhibited with `-n').  Exit with

     nonzero status if an error occurs in executing the GDB commands in

     the command files.

     Batch mode may be useful for running GDB as a filter, for example

     to download and run a program on another computer; in order to

     make this more useful, the message

          Program exited normally.

     (which is ordinarily issued whenever a program running under GDB

     control terminates) is not issued when running in batch mode.

`-batch-silent'

     Run in batch mode exactly like `-batch', but totally silently.  All

     GDB output to `stdout' is prevented (`stderr' is unaffected).

     This is much quieter than `-silent' and would be useless for an

     interactive session.

     This is particularly useful when using targets that give `Loading

     section' messages, for example.

     Note that targets that give their output via GDB, as opposed to

     writing directly to `stdout', will also be made silent.

`-return-child-result'

     The return code from GDB will be the return code from the child

     process (the process being debugged), with the following

     exceptions:

        * GDB exits abnormally.  E.g., due to an incorrect argument or

          an internal error.  In this case the exit code is the same as

          it would have been without `-return-child-result'.

        * The user quits with an explicit value.  E.g., `quit 1'.

        * The child process never runs, or is not allowed to terminate,

          in which case the exit code will be -1.

     This option is useful in conjunction with `-batch' or

     `-batch-silent', when GDB is being used as a remote program loader

     or simulator interface.

`-nowindows'

`-nw'

     "No windows".  If GDB comes with a graphical user interface (GUI)

     built in, then this option tells GDB to only use the command-line

     interface.  If no GUI is available, this option has no effect.

`-windows'

`-w'

     If GDB includes a GUI, then this option requires it to be used if

     possible.

`-cd DIRECTORY'

     Run GDB using DIRECTORY as its working directory, instead of the

     current directory.

`-fullname'

`-f'

     GNU Emacs sets this option when it runs GDB as a subprocess.  It

     tells GDB to output the full file name and line number in a

     standard, recognizable fashion each time a stack frame is

     displayed (which includes each time your program stops).  This

     recognizable format looks like two `\032' characters, followed by

     the file name, line number and character position separated by

     colons, and a newline.  The Emacs-to-GDB interface program uses

     the two `\032' characters as a signal to display the source code

     for the frame.

`-epoch'

     The Epoch Emacs-GDB interface sets this option when it runs GDB as

     a subprocess.  It tells GDB to modify its print routines so as to

     allow Epoch to display values of expressions in a separate window.

`-annotate LEVEL'

     This option sets the "annotation level" inside GDB.  Its effect is

     identical to using `set annotate LEVEL' (*note Annotations::).

     The annotation LEVEL controls how much information GDB prints

     together with its prompt, values of expressions, source lines, and

     other types of output.  Level 0 is the normal, level 1 is for use

     when GDB is run as a subprocess of GNU Emacs, level 3 is the

     maximum annotation suitable for programs that control GDB, and

     level 2 has been deprecated.

     The annotation mechanism has largely been superseded by GDB/MI

     (*note GDB/MI::).

`--args'

     Change interpretation of command line so that arguments following

     the executable file are passed as command line arguments to the

     inferior.  This option stops option processing.

`-baud BPS'

`-b BPS'

     Set the line speed (baud rate or bits per second) of any serial

     interface used by GDB for remote debugging.

`-l TIMEOUT'

     Set the timeout (in seconds) of any communication used by GDB for

     remote debugging.

`-tty DEVICE'

`-t DEVICE'

     Run using DEVICE for your program's standard input and output.

`-tui'

     Activate the "Text User Interface" when starting.  The Text User

     Interface manages several text windows on the terminal, showing

     source, assembly, registers and GDB command outputs (*note GDB

     Text User Interface: TUI.).  Alternatively, the Text User

     Interface can be enabled by invoking the program `gdbtui'.  Do not

     use this option if you run GDB from Emacs (*note Using GDB under

     GNU Emacs: Emacs.).

`-interpreter INTERP'

     Use the interpreter INTERP for interface with the controlling

     program or device.  This option is meant to be set by programs

     which communicate with GDB using it as a back end.  *Note Command