* elfcode.h (elf_bfd_final_link): If trying to generate a shared

[binutils.git] / gdb / README

		      README for gdb-4.12 release
		    Updated 3-Feb-94 by Fred Fish

This is GDB, the GNU source-level debugger, presently running under un*x.
A summary of new features is in the file `NEWS'.


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-4.12 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-4.12.tar.gz file, you'll find a directory
called `gdb-4.12', which contains:

  Makefile.in      config.sub*      glob/            opcodes/
  README           configure*       include/         readline/
  bfd/             configure.in     libiberty/       texinfo/
  config/          etc/             mmalloc/
  config.guess*    gdb/             move-if-change*

To build GDB, you can just do:

	cd gdb-4.12
	./configure
	make
	cp gdb/gdb /usr/local/bin/gdb	(or wherever you want)

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

   The GDB 4 release includes an already-formatted reference card,
ready for printing with PostScript or GhostScript, in the `gdb'
subdirectory of the main source directory.  (In `gdb-4.12/gdb/refcard.ps'.)
If you can use PostScript or GhostScript with your printer, you can
print the reference card immediately with `refcard.ps'.

   The release also includes the source for the reference card.  You
can format it, using TeX, by typing:

     make refcard.dvi

   The GDB 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 DVI output program.

   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' subdirectory.  The main Info file is
`gdb-VERSION-NUMBER/gdb/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-4.12', in the case of version 4.12), you can make
the Info file by typing:

     cd gdb
     make gdb.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.

   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-VERSION-NUMBER/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-4.12/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 4.12 distribution is in the `gdb-4.12'
directory.  That directory contains:

`gdb-4.12/configure (and supporting files)'
     script for configuring GDB and all its supporting libraries.

`gdb-4.12/gdb'
     the source specific to GDB itself

`gdb-4.12/bfd'
     source for the Binary File Descriptor library

`gdb-4.12/include'
     GNU include files

`gdb-4.12/libiberty'
     source for the `-liberty' free software library

`gdb-4.12/opcodes'
     source for the library of opcode tables and disassemblers

`gdb-4.12/readline'
     source for the GNU command-line interface

`gdb-4.12/glob'
     source for the GNU filename pattern-matching subroutine

`gdb-4.12/mmalloc'
     source for the GNU memory-mapped malloc package

'gdb-4.12/sim'
     source for some simulators (z8000, H8/300, H8/500, etc)

   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-4.12' directory.

   First switch to the `gdb-VERSION-NUMBER' source directory if you are
not already in it; then run `configure'.  Pass the identifier for the
platform on which GDB will run as an argument.

   For example:

     cd gdb-4.12
     ./configure HOST
     make

where HOST is an identifier such as `sun4' or `decstation', that
identifies the platform where GDB will run.

   Running `configure HOST' 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 HOST

   If you run `configure' from a directory that contains source
directories for multiple libraries or programs, such as the `gdb-4.12'
source directory for version 4.12, `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 4.12, type the following to configure only
the `bfd' subdirectory:

     cd gdb-4.12/bfd
     ../configure HOST

   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 4.12, you can build GDB in a separate
directory for a Sun 4 like this:

     cd gdb-4.12
     mkdir ../gdb-sun4
     cd ../gdb-sun4
     ../gdb-4.12/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-4.12' (or in a separate configured directory configured with
`--srcdir=PATH/gdb-4.12'), 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-sunos411
     % sh config.sub sun3
     m68k-sun-sunos411
     % sh config.sub decstation
     mips-dec-ultrix42
     % sh config.sub hp300bsd
     m68k-hp-bsd
     % sh config.sub i386v
     i386-unknown-sysv
     % sh config.sub i786v
     Invalid configuration `i786v': machine `i786v' not recognized

`config.sub' is also distributed in the GDB source directory
(`gdb-4.12', for version 4.12).


`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]
               [--target=TARGET] 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.

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

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

`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 (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 file rem-multi.shar contains a general stub that can probably
run on various different flavors of unix to allow debugging over a
serial line from one machine to another.

Some working remote interfaces for talking to existing ROM monitors
are:
	remote-adapt.c	 AMD 29000 "Adapt"
	remote-eb.c	 AMD 29000 "EBMON"
	remote-es1800.c	 Ericsson 1800 monitor
	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-sim.c	 Generalized simulator protocol
	remote-st2000.c	 Tandem ST-2000 monitor
	remote-udi.c	 AMD 29000 using the AMD "Universal Debug Interface"
	remote-vx.c	 VxWorks realtime kernel
	remote-z8k.c	 Zilog Z8000 simulator

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
"[email protected]".  Please email all bugs, and all requests for
help with GDB, to that address.  Please include the GDB version number
(e.g. gdb-4.12), and how you configured it (e.g. "sun4" or "mach386
host, i586-intel-synopsys target").  If you include the banner that GDB
prints when it starts up, that will give us enough information.

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.

  * On the SPARC GDB reports incorrect values of struct arguments to
    functions, for the seventh and subsequent arguments.  We have been looking
    at this but no fix is available yet.

  * 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.

    Under some circumstances OSF/1 shared libraries do get relocated to a
    different address, but gdb cannot handle these relocations yet. If you
    encounter problems while debugging executables which use shared libraries,
    try to relink your executable with the -non_shared option when using cc
    or with the -static option when using gcc.

  * Notes for BSD/386:
    To compile gdb-4.12 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
=====================

There is an "xxgdb", which seems to work for simple operations,
which was posted to comp.sources.x.

For those interested in auto display of source and the availability of
an editor while debugging I suggest trying gdb-mode in gnu-emacs
(Try typing M-x gdb RETURN).  Comments on this mode are 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.  In particular, see the nodes Getting Started,
Debugging GDB, New Architectures, Coding Style, Clean Design, and
Submitting Patches.

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 gdb's with local modifications.
The testsuite is distributed separately from the base gdb distribution
for the convenience of people that wish to get either gdb or the testsuite
separately.

The name of the testsuite is gdb-4.12-testsuite.tar.gz.  You unpack it in the
same directory in which you unpacked the base gdb distribution, and it
will create and populate the directory gdb-4.12/gdb/testsuite.

Running the testsuite requires the prior installation of dejagnu, which
should be available via ftp.  Once dejagnu is installed, you can run
the tests in one of two ways:

  (1)	cd gdb-4.12/gdb		(assuming you also unpacked gdb)
	make check

or

  (2)	cd gdb-4.12/gdb/testsuite
	make		(builds the test executables)
	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, in case you wish to remove some
test executables before running the tests, 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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