INSTALL

Installation Instructions
*************************

Copyright (C) 1994, 1995, 1996, 1999, 2000, 2001, 2002, 2004, 2005,
2006, 2007 Free Software Foundation, Inc.

This file is free documentation; the Free Software Foundation gives
unlimited permission to copy, distribute and modify it.

Glog-Specific Install Notes
================================

*** NOTE FOR 64-BIT LINUX SYSTEMS

The glibc built-in stack-unwinder on 64-bit systems has some problems
with the glog libraries.  (In particular, if you are using
InstallFailureSignalHandler(), the signal may be raised in the middle
of malloc, holding some malloc-related locks when they invoke the
stack unwinder.  The built-in stack unwinder may call malloc
recursively, which may require the thread to acquire a lock it already
holds: deadlock.)

For that reason, if you use a 64-bit system and you need
InstallFailureSignalHandler(), we strongly recommend you install
libunwind before trying to configure or install google glog.
libunwind can be found at

   http://download.savannah.nongnu.org/releases/libunwind/libunwind-snap-070410.tar.gz

Even if you already have libunwind installed, you will probably still
need to install from the snapshot to get the latest version.

CAUTION: if you install libunwind from the URL above, be aware that
you may have trouble if you try to statically link your binary with
glog: that is, if you link with 'gcc -static -lgcc_eh ...'.  This
is because both libunwind and libgcc implement the same C++ exception
handling APIs, but they implement them differently on some platforms.
This is not likely to be a problem on ia64, but may be on x86-64.

Also, if you link binaries statically, make sure that you add
-Wl,--eh-frame-hdr to your linker options. This is required so that
libunwind can find the information generated by the compiler required
for stack unwinding.

Using -static is rare, though, so unless you know this will affect you
it probably won't.

If you cannot or do not wish to install libunwind, you can still try
to use two kinds of stack-unwinder: 1. glibc built-in stack-unwinder
and 2. frame pointer based stack-unwinder.

1. As we already mentioned, glibc's unwinder has a deadlock issue.
However, if you don't use InstallFailureSignalHandler() or you don't
worry about the rare possibilities of deadlocks, you can use this
stack-unwinder.  If you specify no options and libunwind isn't
detected on your system, the configure script chooses this unwinder by
default.

2. The frame pointer based stack unwinder requires that your
application, the glog library, and system libraries like libc, all be
compiled with a frame pointer.  This is *not* the default for x86-64.

If you are on x86-64 system, know that you have a set of system
libraries with frame-pointers enabled, and compile all your
applications with -fno-omit-frame-pointer, then you can enable the
frame pointer based stack unwinder by passing the
--enable-frame-pointers flag to configure.


Basic Installation
==================

Briefly, the shell commands `./configure; make; make install' should
configure, build, and install this package.  The following
more-detailed instructions are generic; see the `README.md' file for
instructions specific to this package.

   The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation.  It uses
those values to create a `Makefile' in each directory of the package.
It may also create one or more `.h' files containing system-dependent
definitions.  Finally, it creates a shell script `config.status' that
you can run in the future to recreate the current configuration, and a
file `config.log' containing compiler output (useful mainly for
debugging `configure').

   It can also use an optional file (typically called `config.cache'
and enabled with `--cache-file=config.cache' or simply `-C') that saves
the results of its tests to speed up reconfiguring.  Caching is
disabled by default to prevent problems with accidental use of stale
cache files.

   If you need to do unusual things to compile the package, please try
to figure out how `configure' could check whether to do them, and mail
diffs or instructions to the address given in the `README.md' so they can
be considered for the next release.  If you are using the cache, and at
some point `config.cache' contains results you don't want to keep, you
may remove or edit it.

   The file `configure.ac' (or `configure.in') is used to create
`configure' by a program called `autoconf'.  You need `configure.ac' if
you want to change it or regenerate `configure' using a newer version
of `autoconf'.

The simplest way to compile this package is:

  1. `cd' to the directory containing the package's source code and type
     `./configure' to configure the package for your system.

     Running `configure' might take a while.  While running, it prints
     some messages telling which features it is checking for.

  2. Type `make' to compile the package.

  3. Optionally, type `make check' to run any self-tests that come with
     the package.

  4. Type `make install' to install the programs and any data files and
     documentation.

  5. You can remove the program binaries and object files from the
     source code directory by typing `make clean'.  To also remove the
     files that `configure' created (so you can compile the package for
     a different kind of computer), type `make distclean'.  There is
     also a `make maintainer-clean' target, but that is intended mainly
     for the package's developers.  If you use it, you may have to get
     all sorts of other programs in order to regenerate files that came
     with the distribution.

  6. Often, you can also type `make uninstall' to remove the installed
     files again.

Compilers and Options
=====================

Some systems require unusual options for compilation or linking that the
`configure' script does not know about.  Run `./configure --help' for
details on some of the pertinent environment variables.

   You can give `configure' initial values for configuration parameters
by setting variables in the command line or in the environment.  Here
is an example:

     ./configure CC=c99 CFLAGS=-g LIBS=-lposix

   *Note Defining Variables::, for more details.

Compiling For Multiple Architectures
====================================

You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  To do this, you can use GNU `make'.  `cd' to the
directory where you want the object files and executables to go and run
the `configure' script.  `configure' automatically checks for the
source code in the directory that `configure' is in and in `..'.

   With a non-GNU `make', it is safer to compile the package for one
architecture at a time in the source code directory.  After you have
installed the package for one architecture, use `make distclean' before
reconfiguring for another architecture.

Installation Names
==================

By default, `make install' installs the package's commands under
`/usr/local/bin', include files under `/usr/local/include', etc.  You
can specify an installation prefix other than `/usr/local' by giving
`configure' the option `--prefix=PREFIX'.

   You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.  If you
pass the option `--exec-prefix=PREFIX' to `configure', the package uses
PREFIX as the prefix for installing programs and libraries.
Documentation and other data files still use the regular prefix.

   In addition, if you use an unusual directory layout you can give
options like `--bindir=DIR' to specify different values for particular
kinds of files.  Run `configure --help' for a list of the directories
you can set and what kinds of files go in them.

   If the package supports it, you can cause programs to be installed
with an extra prefix or suffix on their names by giving `configure' the
option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.

Optional Features
=================

Some packages pay attention to `--enable-FEATURE' options to
`configure', where FEATURE indicates an optional part of the package.
They may also pay attention to `--with-PACKAGE' options, where PACKAGE
is something like `gnu-as' or `x' (for the X Window System).  The
`README.md' should mention any `--enable-' and `--with-' options that the
package recognizes.

   For packages that use the X Window System, `configure' can usually
find the X include and library files automatically, but if it doesn't,
you can use the `configure' options `--x-includes=DIR' and
`--x-libraries=DIR' to specify their locations.

Specifying the System Type
==========================

There may be some features `configure' cannot figure out automatically,
but needs to determine by the type of machine the package will run on.
Usually, assuming the package is built to be run on the _same_
architectures, `configure' can figure that out, but if it prints a
message saying it cannot guess the machine type, give it the
`--build=TYPE' option.  TYPE can either be a short name for the system
type, such as `sun4', or a canonical name which has the form:

     CPU-COMPANY-SYSTEM

where SYSTEM can have one of these forms:

     OS KERNEL-OS

   See the file `config.sub' for the possible values of each field.  If
`config.sub' isn't included in this package, then this package doesn't
need to know the machine type.

   If you are _building_ compiler tools for cross-compiling, you should
use the option `--target=TYPE' to select the type of system they will
produce code for.

   If you want to _use_ a cross compiler, that generates code for a
platform different from the build platform, you should specify the
"host" platform (i.e., that on which the generated programs will
eventually be run) with `--host=TYPE'.

Sharing Defaults
================

If you want to set default values for `configure' scripts to share, you
can create a site shell script called `config.site' that gives default
values for variables like `CC', `cache_file', and `prefix'.
`configure' looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists.  Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: not all `configure' scripts look for a site script.

Defining Variables
==================

Variables not defined in a site shell script can be set in the
environment passed to `configure'.  However, some packages may run
configure again during the build, and the customized values of these
variables may be lost.  In order to avoid this problem, you should set
them in the `configure' command line, using `VAR=value'.  For example:

     ./configure CC=/usr/local2/bin/gcc

causes the specified `gcc' to be used as the C compiler (unless it is
overridden in the site shell script).

Unfortunately, this technique does not work for `CONFIG_SHELL' due to
an Autoconf bug.  Until the bug is fixed you can use this workaround:

     CONFIG_SHELL=/bin/bash /bin/bash ./configure CONFIG_SHELL=/bin/bash

`configure' Invocation
======================

`configure' recognizes the following options to control how it operates.

`--help'
`-h'
     Print a summary of the options to `configure', and exit.

`--version'
`-V'
     Print the version of Autoconf used to generate the `configure'
     script, and exit.

`--cache-file=FILE'
     Enable the cache: use and save the results of the tests in FILE,
     traditionally `config.cache'.  FILE defaults to `/dev/null' to
     disable caching.

`--config-cache'
`-C'
     Alias for `--cache-file=config.cache'.

`--quiet'
`--silent'
`-q'
     Do not print messages saying which checks are being made.  To
     suppress all normal output, redirect it to `/dev/null' (any error
     messages will still be shown).

`--srcdir=DIR'
     Look for the package's source code in directory DIR.  Usually
     `configure' can determine that directory automatically.

`configure' also accepts some other, not widely useful, options.  Run
`configure --help' for more details.