path: root/gdb/README

		     README for gdb-4.18 release
		   Updated 4 Apr 1999 by Jim Blandy

This is GDB, the GNU source-level debugger.
A summary of new features is in the file `NEWS'.

See the GDB home page at http://sourceware.cygnus.com/gdb/ for up to
date release information, mailing list links and archives, etc.


Unpacking and Installation -- quick overview
==========================

In this release, the GDB debugger sources, the generic GNU include
files, the BFD ("binary file description") library, the readline
library, and other libraries all have directories of their own
underneath the gdb-4.18 directory.  The idea is that a variety of GNU
tools can share a common copy of these things.  Be aware of variation
over time--for example don't try to build gdb with a copy of bfd from
a release other than the gdb release (such as a binutils or gas
release), especially if the releases are more than a few weeks apart.
Configuration scripts and makefiles exist to cruise up and down this
directory tree and automatically build all the pieces in the right
order.

When you unpack the gdb-4.18.tar.gz file, you'll find a directory
called `gdb-4.18', which contains:

  COPYING          config.sub*      libiberty/       opcodes/
  COPYING.LIB      configure*       mmalloc/         readline/
  Makefile.in      configure.in     move-if-change*  sim/
  README           etc/             mpw-README       texinfo/
  bfd/             gdb/             mpw-build.in     utils/
  config/          include/         mpw-config.in
  config.guess*    install.sh*      mpw-configure

To build GDB, you can just do:

	cd gdb-4.18
	./configure
	make
	cp gdb/gdb /usr/local/bin/gdb	(or wherever you want)

(Building GDB with DJGPP tools for MS-DOS/MS-Windows is slightly
different; see the file gdb/config/djgpp/README for details.)

This will configure and build all the libraries as well as GDB.
If `configure' can't determine your system type, specify one as its
argument, e.g., sun4 or decstation.

If you get compiler warnings during this stage, see the `Reporting Bugs'
section below; there are a few known problems.

GDB requires an ANSI C compiler.  If you do not have an ANSI C
compiler for your system, you may be able to download and install the
GNU CC compiler.  It is available via anonymous FTP from ftp.gnu.org,
in /pub/gnu/gcc (as a URL, that's ftp://ftp.gnu.org/pub/gnu/gcc).

GDB can be used as a cross-debugger, running on a machine of one type
while debugging a program running on a machine of another type.  See below.


More Documentation
******************

   All the documentation for GDB comes as part of the machine-readable
distribution.  The documentation is written in Texinfo format, which is
a documentation system that uses a single source file to produce both
on-line information and a printed manual.  You can use one of the Info
formatting commands to create the on-line version of the documentation
and TeX (or `texi2roff') to typeset the printed version.

   GDB includes an already formatted copy of the on-line Info version of
this manual in the `gdb/doc' subdirectory.  The main Info file is
`gdb-4.18/gdb/doc/gdb.info', and it refers to subordinate files matching
`gdb.info*' in the same directory.  If necessary, you can print out
these files, or read them with any editor; but they are easier to read
using the `info' subsystem in GNU Emacs or the standalone `info' program,
available as part of the GNU Texinfo distribution.

   If you want to format these Info files yourself, you need one of the
Info formatting programs, such as `texinfo-format-buffer' or
`makeinfo'.

   If you have `makeinfo' installed, and are in the top level GDB
source directory (`gdb-4.18', in the case of version 4.18), you can make
the Info file by typing:

     cd gdb/doc
     make info

   If you want to typeset and print copies of this manual, you need
TeX, a program to print its DVI output files, and `texinfo.tex', the
Texinfo definitions file.  This file is included in the GDB
distribution, in the directory `gdb-4.18/texinfo'.

   TeX is a typesetting program; it does not print files directly, but
produces output files called DVI files.  To print a typeset document,
you need a program to print DVI files.  If your system has TeX
installed, chances are it has such a program.  The precise command to
use depends on your system; `lpr -d' is common; another (for PostScript
devices) is `dvips'.  The DVI print command may require a file name
without any extension or a `.dvi' extension.

   TeX also requires a macro definitions file called `texinfo.tex'. 
This file tells TeX how to typeset a document written in Texinfo
format.  On its own, TeX cannot read, much less typeset a Texinfo file.
 `texinfo.tex' is distributed with GDB and is located in the
`gdb-4.18/texinfo' directory.

   If you have TeX and a DVI printer program installed, you can typeset
and print this manual.  First switch to the the `gdb' subdirectory of
the main source directory (for example, to `gdb-4.18/gdb') and then type:

     make gdb.dvi


Installing GDB
**************

   GDB comes with a `configure' script that automates the process of
preparing GDB for installation; you can then use `make' to build the
`gdb' program.

   The GDB distribution includes all the source code you need for GDB in
a single directory, whose name is usually composed by appending the
version number to `gdb'.

   For example, the GDB version 4.18 distribution is in the `gdb-4.18'
directory.  That directory contains:

`gdb-4.18/{COPYING,COPYING.LIB}'
     Standard GNU license files.  Please read them.

`gdb-4.18/bfd'
     source for the Binary File Descriptor library

`gdb-4.18/config*'
     script for configuring GDB, along with other support files

`gdb-4.18/gdb'
     the source specific to GDB itself

`gdb-4.18/include'
     GNU include files

`gdb-4.18/libiberty'
     source for the `-liberty' free software library

`gdb-4.18/mmalloc'
     source for the GNU memory-mapped malloc package

`gdb-4.18/opcodes'
     source for the library of opcode tables and disassemblers

`gdb-4.18/readline'
     source for the GNU command-line interface
     NOTE:  The readline library is compiled for use by GDB, but will
     not be installed on your system when "make install" is issued.

`gdb-4.18/sim'
     source for some simulators (ARM, D10V, SPARC, M32R, MIPS, PPC, V850, etc)

`gdb-4.18/intl'
     source for the GNU gettext library, for internationalization.
     This is slightly modified from the standalone gettext
     distribution you can get from GNU.

`gdb-4.18/texinfo'
     The `texinfo.tex' file, which you need in order to make a printed
     manual using TeX.

`gdb-4.18/etc'
     Coding standards, useful files for editing GDB, and other
     miscellanea.

`gdb-4.18/utils'
     A grab bag of random utilities.

   Note: the following instructions are for building GDB on Unix or
Unix-like systems.  Instructions for building with DJGPP for
MS-DOS/MS-Windows are in the file gdb/config/djgpp/README.

   The simplest way to configure and build GDB is to run `configure'
from the `gdb-VERSION-NUMBER' source directory, which in this example
is the `gdb-4.18' directory.

   First switch to the `gdb-VERSION-NUMBER' source directory if you are
not already in it; then run `configure'.

   For example:

     cd gdb-4.18
     ./configure
     make

   Running `configure' followed by `make' builds the `bfd',
`readline', `mmalloc', and `libiberty' libraries, then `gdb' itself.
The configured source files, and the binaries, are left in the
corresponding source directories.

   `configure' is a Bourne-shell (`/bin/sh') script; if your system
does not recognize this automatically when you run a different shell,
you may need to run `sh' on it explicitly:

     sh configure

   If you run `configure' from a directory that contains source
directories for multiple libraries or programs, such as the `gdb-4.18'
source directory for version 4.18, `configure' creates configuration
files for every directory level underneath (unless you tell it not to,
with the `--norecursion' option).

   You can run the `configure' script from any of the subordinate
directories in the GDB distribution, if you only want to configure that
subdirectory; but be sure to specify a path to it.

   For example, with version 4.18, type the following to configure only
the `bfd' subdirectory:

     cd gdb-4.18/bfd
     ../configure

   You can install `gdb' anywhere; it has no hardwired paths. However,
you should make sure that the shell on your path (named by the `SHELL'
environment variable) is publicly readable.  Remember that GDB uses the
shell to start your program--some systems refuse to let GDB debug child
processes whose programs are not readable.


Compiling GDB in another directory
==================================

   If you want to run GDB versions for several host or target machines,
you need a different `gdb' compiled for each combination of host and
target.  `configure' is designed to make this easy by allowing you to
generate each configuration in a separate subdirectory, rather than in
the source directory.  If your `make' program handles the `VPATH'
feature correctly (GNU `make' and SunOS 'make' are two that should),
running `make' in each of these directories builds the `gdb' program
specified there.

   To build `gdb' in a separate directory, run `configure' with the
`--srcdir' option to specify where to find the source. (You also need
to specify a path to find `configure' itself from your working
directory.  If the path to `configure' would be the same as the
argument to `--srcdir', you can leave out the `--srcdir' option; it
will be assumed.)

   For example, with version 4.18, you can build GDB in a separate
directory for a Sun 4 like this:

     cd gdb-4.18
     mkdir ../gdb-sun4
     cd ../gdb-sun4
     ../gdb-4.18/configure sun4
     make

   When `configure' builds a configuration using a remote source
directory, it creates a tree for the binaries with the same structure
(and using the same names) as the tree under the source directory.  In
the example, you'd find the Sun 4 library `libiberty.a' in the
directory `gdb-sun4/libiberty', and GDB itself in `gdb-sun4/gdb'.

   One popular reason to build several GDB configurations in separate
directories is to configure GDB for cross-compiling (where GDB runs on
one machine--the host--while debugging programs that run on another
machine--the target).  You specify a cross-debugging target by giving
the `--target=TARGET' option to `configure'.

   When you run `make' to build a program or library, you must run it
in a configured directory--whatever directory you were in when you
called `configure' (or one of its subdirectories).

   The `Makefile' that `configure' generates in each source directory
also runs recursively.  If you type `make' in a source directory such
as `gdb-4.18' (or in a separate configured directory configured with
`--srcdir=PATH/gdb-4.18'), you will build all the required libraries,
and then build GDB.

   When you have multiple hosts or targets configured in separate
directories, you can run `make' on them in parallel (for example, if
they are NFS-mounted on each of the hosts); they will not interfere
with each other.


Specifying names for hosts and targets
======================================

   The specifications used for hosts and targets in the `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:

     ARCHITECTURE-VENDOR-OS

   For example, you can use the alias `sun4' as a HOST argument or in a
`--target=TARGET' option.  The equivalent full name is
`sparc-sun-sunos4'.

   The `configure' script accompanying GDB does not provide any query
facility to list all supported host and target names or aliases. 
`configure' calls the Bourne shell script `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:

     % sh config.sub sun4
     sparc-sun-sunos4.1.1
     % sh config.sub sun3
     m68k-sun-sunos4.1.1
     % sh config.sub decstation
     mips-dec-ultrix4.2
     % sh config.sub hp300bsd
     m68k-hp-bsd
     % sh config.sub i386v
     i386-pc-sysv
     % sh config.sub i786v
     Invalid configuration `i786v': machine `i786v' not recognized

`config.sub' is also distributed in the GDB source directory
(`gdb-4.18', for version 4.18).


`configure' options
===================

   Here is a summary of the `configure' options and arguments that are
most often useful for building GDB.  `configure' also has several other
options not listed here.  *note : (configure.info)What Configure Does,
for a full explanation of `configure'.

     configure [--help]
               [--prefix=DIR]
               [--srcdir=PATH]
               [--norecursion] [--rm]
	       [--enable-build-warnings]
               [--target=TARGET]
	       [--host=HOST]
	       [HOST]

You may introduce options with a single `-' rather than `--' if you
prefer; but you may abbreviate option names if you use `--'.

`--help'
     Display a quick summary of how to invoke `configure'.

`-prefix=DIR'
     Configure the source to install programs and files under directory
     `DIR'.

`--srcdir=PATH'
     *Warning: using this option requires GNU `make', or another `make'
     that compatibly implements the `VPATH' feature.*
     Use this option to make configurations in directories separate
     from the GDB source directories.  Among other things, you can use
     this to build (or maintain) several configurations simultaneously,
     in separate directories.  `configure' writes configuration
     specific files in the current directory, but arranges for them to
     use the source in the directory PATH.  `configure' will create
     directories under the working directory in parallel to the source
     directories below PATH.

`--norecursion'
     Configure only the directory level where `configure' is executed;
     do not propagate configuration to subdirectories.

`--rm'
     Remove the configuration that the other arguments specify.

`--enable-build-warnings'
     When building the GDB sources, ask the compiler to warn about any
     code which looks even vaguely suspicious.  You should only using
     this feature if you're compiling with GNU CC.  It passes the
     following flags:
	-Wall
	-Wpointer-arith
	-Wstrict-prototypes
	-Wmissing-prototypes
	-Wmissing-declarations

`--target=TARGET'
     Configure GDB for cross-debugging programs running on the specified
     TARGET.  Without this option, GDB is configured to debug programs
     that run on the same machine (HOST) as GDB itself.

     There is no convenient way to generate a list of all available
     targets.

`--host=HOST'
     Configure GDB to run on the specified HOST.

     There is no convenient way to generate a list of all available
     hosts.

`HOST ...'
     Same as `--host=HOST'.  If you omit this, GDB will guess; it's
     quite accurate.

`configure' accepts other options, for compatibility with configuring
other GNU tools recursively; but these are the only options that affect
GDB or its supporting libraries.


Languages other than C
=======================

See the GDB manual (gdb/doc/gdb.texinfo) for information on this.


Kernel debugging
=================

I have't done this myself so I can't really offer any advice.
Remote debugging over serial lines works fine, but the kernel debugging
code in here has not been tested in years.  Van Jacobson has
better kernel debugging, but the UC lawyers won't let FSF have it.


Remote debugging
=================

The files m68k-stub.c, i386-stub.c, and sparc-stub.c are examples of
remote stubs to be used with remote.c.  They are designed to run
standalone on an m68k, i386, or SPARC cpu and communicate properly with
the remote.c stub over a serial line.

The directory gdb/gdbserver/ contains `gdbserver', a program that
allows remote debugging for Unix applications.  gdbserver is only
supported for some native configurations, including Sun 3, Sun 4,
and Linux.

There are a number of remote interfaces for talking to existing ROM
monitors and other hardware:

	remote-adapt.c	 AMD 29000 "Adapt"
	remote-array.c   Array Tech RAID controller
	remote-bug.c	 Motorola BUG monitor
        remote-d10v.c    GDB protocol, talking to a d10v chip
	remote-e7000.c	 Hitachi E7000 ICE
	remote-eb.c	 AMD 29000 "EBMON"
	remote-es.c	 Ericsson 1800 monitor
	remote-est.c	 EST emulator
	remote-hms.c	 Hitachi Micro Systems H8/300 monitor
	remote-mips.c	 MIPS remote debugging protocol
	remote-mm.c	 AMD 29000 "minimon"
	remote-nindy.c   Intel 960 "Nindy"
	remote-nrom.c	 NetROM ROM emulator
	remote-os9k.c	 PC running OS/9000
	remote-rdi.c	 ARM with Angel monitor
	remote-rdp.c	 ARM with Demon monitor
	remote-sds.c	 PowerPC SDS monitor
	remote-sim.c	 Generalized simulator protocol
	remote-st.c	 Tandem ST-2000 monitor
	remote-udi.c	 AMD 29000 using the AMD "Universal Debug Interface"
	remote-vx.c	 VxWorks realtime kernel

Remote-vx.c and the vx-share subdirectory contain a remote interface for the
VxWorks realtime kernel, which communicates over TCP using the Sun
RPC library.  This would be a useful starting point for other remote-
via-ethernet back ends.

Remote-udi.c and the 29k-share subdirectory contain a remote interface
for AMD 29000 programs, which uses the AMD "Universal Debug Interface".
This allows GDB to talk to software simulators, emulators, and/or bare
hardware boards, via network or serial interfaces.  Note that GDB only
provides an interface that speaks UDI, not a complete solution.  You
will need something on the other end that also speaks UDI.


Reporting Bugs
===============

The correct address for reporting bugs found in gdb is
"bug-gdb@gnu.org".  Please email all bugs, and all requests for
help with GDB, to that address.  Please include the GDB version number
(e.g., gdb-4.18), and how you configured it (e.g., "sun4" or "mach386
host, i586-intel-synopsys target").  Since GDB now supports so many
different configurations, it is important that you be precise about this.
If at all possible, you should include the actual banner that GDB prints
when it starts up, or failing that, the actual configure command that
you used when configuring GDB.

For more information on how/whether to report bugs, see the GDB Bugs
section of the GDB manual (gdb/doc/gdb.texinfo).

Known bugs:

  * Under Ultrix 4.2 (DECstation-3100) or Alphas under OSF/1, we have
    seen problems with backtraces after interrupting the inferior out
    of a read().  The problem is caused by ptrace() returning an
    incorrect value for the frame pointer register (register 15 or
    30).  As far as we can tell, this is a kernel problem.  Any help
    with this would be greatly appreciated.

  * Under Ultrix 4.4 (DECstation-3100), setting the TERMCAP environment
    variable to a string without a trailing ':' can cause GDB to dump
    core upon startup.  Although the core file makes it look as though
    GDB code failed, the crash actually occurs within a call to the
    termcap library function tgetent().  The problem can be solved by
    using the GNU Termcap library.

    Alphas running OSF/1 (versions 1.0 through 2.1) have the same buggy
    termcap code, but GDB behaves strangely rather than crashing.

  * On DECstations there are warnings about shift counts out of range in
    various BFD modules.  None of them is a cause for alarm, they are actually
    a result of bugs in the DECstation compiler.

  * Notes for the DEC Alpha using OSF/1:
    The debugging output of native cc has two known problems; we view these
    as compiler bugs.
    The linker miscompacts symbol tables, which causes gdb to confuse the
    type of variables or results in `struct <illegal>' type outputs.
    dbx has the same problems with those executables.  A workaround is to
    specify -Wl,-b when linking, but that will increase the executable size
    considerably.
    If a structure has incomplete type in one file (e.g., "struct foo *"
    without a definition for "struct foo"), gdb will be unable to find the
    structure definition from another file.
    It has been reported that the Ultrix 4.3A compiler on decstations has the
    same problems.

  * Notes for Solaris 2.x, using the SPARCworks cc compiler:
    You have to compile your program with the -xs option of the SPARCworks
    compiler to be able to debug your program with gdb.
    Under Solaris 2.3 you also need patch 101409-03 (Jumbo linker patch).
    Under Solaris 2.2, if you have patch 101052 installed, make sure
    that it is at least at revision 101052-06.

  * Under Irix 5 for SGIs, you must have installed the `compiler_dev.hdr'
    subsystem that is on the IDO CD, otherwise you will get complaints
    that certain files such as `/usr/include/syms.h' cannot be found.

  * Notes for BSD/386:
    To compile gdb-4.18 on BSD/386, you must run the configure script and
    its subscripts with bash.  Here is an easy way to do this:

	bash -c 'CONFIG_SHELL=/bin/bash ./configure'

    (configure will report i386-unknown-bsd).  Then, compile with the
    standard "make" command.

GDB can produce warnings about symbols that it does not understand.  By
default, these warnings are disabled.  You can enable them by executing
`set complaint 10' (which you can put in your ~/.gdbinit if you like).
I recommend doing this if you are working on a compiler, assembler,
linker, or GDB, since it will point out problems that you may be able
to fix.  Warnings produced during symbol reading indicate some mismatch
between the object file and GDB's symbol reading code.  In many cases,
it's a mismatch between the specs for the object file format, and what
the compiler actually outputs or the debugger actually understands.


X Windows versus GDB
=====================

You should check out DDD, the Data Display Debugger.  Here's the blurb
from the DDD web site, http://www.cs.tu-bs.de/softech/ddd:

    The Data Display Debugger (DDD) is a popular graphical user
    interface for command-line debuggers such as GDB, DBX, JDB, WDB,
    XDB, the Perl debugger, and the Python debugger.  Besides ``usual''
    front-end features such as viewing source texts, DDD has become
    famous through its interactive graphical data display, where data
    structures are displayed as graphs. A simple mouse click
    dereferences pointers or views structure contents, updated each
    time the program stops. Using DDD, you can reason about your
    application by watching its data, not just by viewing it execute
    lines of source code.

Emacs users will very likely enjoy the Grand Unified Debugger mode;
try typing `M-x gdb RET'.

Those interested in experimenting with a new kind of gdb-mode
should load gdb/gdba.el into GNU Emacs 19.25 or later.  Comments
on this mode are also welcome.


Writing Code for GDB
=====================

There is a lot of information about writing code for GDB in the
internals manual, distributed with GDB in gdb/doc/gdbint.texinfo.  You
can read it by hand, print it by using TeX and texinfo, or process it
into an `info' file for use with Emacs' info mode or the standalone
`info' program.

If you are pondering writing anything but a short patch, especially
take note of the information about copyrights in the node Submitting
Patches.  It can take quite a while to get all the paperwork done, so
we encourage you to start that process as soon as you decide you are
planning to work on something, or at least well ahead of when you
think you will be ready to submit the patches.


GDB Testsuite
=============

There is a DejaGNU based testsuite available for testing your newly
built GDB, or for regression testing GDBs with local modifications.

Running the testsuite requires the prior installation of DejaGNU,
which is generally available via ftp; you'll need a pretty recent
release.  Once DejaGNU is installed, you can run the tests in one of
two ways:

  (1)	cd gdb-4.18/gdb		(assuming you also unpacked gdb)
	make check

or

  (2)	cd gdb-4.18/gdb/testsuite
	make site.exp	(builds the site specific file)
	runtest -tool gdb GDB=../gdb    (or GDB=<somepath> as appropriate)

The second method gives you slightly more control in case of problems with
building one or more test executables or if you are using the testsuite
'standalone', without it being part of the GDB source tree.

See the DejaGNU documentation for further details.


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