libvips/doc/reference/extending.xml

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<?xml version="1.0"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
]>
<refentry id="glib-building">
<refmeta>
<refentrytitle>Compiling the GLib package</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GLib Library</refmiscinfo>
</refmeta>
<refnamediv>
<refname>Compiling the GLib Package</refname>
<refpurpose>How to compile GLib itself</refpurpose>
</refnamediv>
<refsect1 id="building">
<title>Building the Library on UNIX</title>
<para>
On UNIX, GLib uses the standard GNU build system,
using <application>autoconf</application> for package
configuration and resolving portability issues,
<application>automake</application> for building makefiles
that comply with the GNU Coding Standards, and
<application>libtool</application> for building shared
libraries on multiple platforms. The normal sequence for
compiling and installing the GLib library is thus:
<literallayout>
<userinput>./configure</userinput>
<userinput>make</userinput>
<userinput>make install</userinput>
</literallayout>
</para>
<para>
The standard options provided by <application>GNU
autoconf</application> may be passed to the
<command>configure</command> script. Please see the
<application>autoconf</application> documentation or run
<command>./configure --help</command> for information about
the standard options.
</para>
<para>
The GTK+ documentation contains
<ulink url="../gtk/gtk-building.html">further details</ulink>
about the build process and ways to influence it.
</para>
</refsect1>
<refsect1 id="dependencies">
<title>Dependencies</title>
<para>
Before you can compile the GLib library, you need to have
various other tools and libraries installed on your system.
Beyond a C compiler (which must implement C90, but does not need
to implement C99), the two tools needed during the build process
(as differentiated from the tools used in when creating GLib
mentioned above such as <application>autoconf</application>) are
<command>pkg-config</command> and GNU make.
</para>
<itemizedlist>
<listitem>
<para>
<ulink url="http://www.freedesktop.org/software/pkgconfig/">pkg-config</ulink>
is a tool for tracking the compilation flags needed for
libraries that are used by the GLib library. (For each
library, a small <literal>.pc</literal> text file is
installed in a standard location that contains the compilation
flags needed for that library along with version number
information.) The version of <command>pkg-config</command>
needed to build GLib is mirrored in the
<filename>dependencies</filename> directory
on the <ulink url="ftp://ftp.gtk.org/pub/gtk/v2.2/">GTK+ FTP
site.</ulink>
</para>
</listitem>
<listitem>
<para>
The GLib Makefiles make use of several features specific to
<ulink url="http://www.gnu.org/software/make">GNU
make</ulink>, and will not build correctly with other
versions of <command>make</command>. You will need to
install it if you don't already have it on your system. (It
may be called <command>gmake</command> rather than
<command>make</command>.)
</para>
</listitem>
</itemizedlist>
<para>
A UNIX build of GLib requires that the system implements at
least the original 1990 version of POSIX. Beyond this, it
depends on a number of other libraries.
</para>
<itemizedlist>
<listitem>
<para>
The <ulink url="http://www.gnu.org/software/libiconv/">GNU
libiconv library</ulink> is needed to build GLib if your
system doesn't have the <function>iconv()</function>
function for doing conversion between character
encodings. Most modern systems should have
<function>iconv()</function>, however many older systems lack
an <function>iconv()</function> implementation. On such systems,
you must install the libiconv library. This can be found at:
<ulink url="http://www.gnu.org/software/libiconv">http://www.gnu.org/software/libiconv</ulink>.
</para>
<para>
If your system has an <function>iconv()</function> implementation but
you want to use libiconv instead, you can pass the
--with-libiconv option to configure. This forces
libiconv to be used.
</para>
<para>
Note that if you have libiconv installed in your default include
search path (for instance, in <filename>/usr/local/</filename>), but
don't enable it, you will get an error while compiling GLib because
the <filename>iconv.h</filename> that libiconv installs hides the
system iconv.
</para>
<para>
If you are using the native iconv implementation on Solaris
instead of libiconv, you'll need to make sure that you have
the converters between locale encodings and UTF-8 installed.
At a minimum you'll need the SUNWuiu8 package. You probably
should also install the SUNWciu8, SUNWhiu8, SUNWjiu8, and
SUNWkiu8 packages.
</para>
<para>
The native iconv on Compaq Tru64 doesn't contain support for
UTF-8, so you'll need to use GNU libiconv instead. (When
using GNU libiconv for GLib, you'll need to use GNU libiconv
for GNU gettext as well.) This probably applies to related
operating systems as well.
</para>
</listitem>
<listitem>
<para>
The libintl library from the <ulink
url="http://www.gnu.org/software/gettext">GNU gettext
package</ulink> is needed if your system doesn't have the
<function>gettext()</function> functionality for handling
message translation databases.
</para>
</listitem>
<listitem>
<para>
A thread implementation is needed. The thread support in GLib
can be based upon POSIX threads or win32 threads.
</para>
</listitem>
<listitem>
<para>
GRegex uses the <ulink url="http://www.pcre.org/">PCRE library</ulink>
for regular expression matching. The default is to use the internal
version of PCRE that is patched to use GLib for memory management
and Unicode handling. If you prefer to use the system-supplied PCRE
library you can pass the <option>--with-pcre=system</option> option
to, but it is not recommended.
</para>
</listitem>
<listitem>
<para>
The optional extended attribute support in GIO requires the
getxattr() family of functions that may be provided by glibc or
by the standalone libattr library. To build GLib without extended
attribute support, use the <option>--disable-xattr</option>
option.
</para>
</listitem>
<listitem>
<para>
The optional SELinux support in GIO requires libselinux.
To build GLib without SELinux support, use the
<option>--disable-selinux</option> option.
</para>
</listitem>
<listitem>
<para>
The optional support for DTrace requires the
<filename>sys/sdt.h</filename> header, which is provided
by SystemTap on Linux. To build GLib without DTrace, use
the <option>--disable-dtrace</option> configure option.
</para>
</listitem>
<listitem>
<para>
The optional support for
<ulink url="http://sourceware.org/systemtap/">SystemTap</ulink>
can be disabled with the <option>--disable-systemtap</option>
configure option.
</para>
</listitem>
</itemizedlist>
</refsect1>
<refsect1 id="extra-configuration-options">
<title>Extra Configuration Options</title>
<para>
In addition to the normal options, the
<command>configure</command> script in the GLib
library supports these additional arguments:
</para>
<formalpara>
<title><systemitem>--enable-debug</systemitem></title>
<para>
Turns on various amounts of debugging support. Setting this to 'no'
disables g_assert(), g_return_if_fail(), g_return_val_if_fail() and
all cast checks between different object types. Setting it to 'minimum' disables only cast checks. Setting it to 'yes' enables
<link linkend="G-DEBUG:CAPS">runtime debugging</link>.
The default is 'minimum'.
Note that 'no' is fast, but dangerous as it tends to destabilize
even mostly bug-free software by changing the effect of many bugs
from simple warnings into fatal crashes. Thus
<option>--enable-debug=no</option> should <emphasis>not</emphasis>
be used for stable releases of GLib.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-gc-friendly</systemitem> and
<systemitem>--enable-gc-friendly</systemitem></title>
<para>
By default, and with <systemitem>--disable-gc-friendly</systemitem>
as well, Glib does not clear the memory for certain objects before
they are freed. For example, Glib may decide to recycle GList nodes
by putting them in a free list. However, memory profiling and debugging
tools like <ulink url="http://www.valgrind.org">Valgrind</ulink> work
better if an application does not keep dangling pointers to freed
memory (even though these pointers are no longer dereferenced), or
invalid pointers inside uninitialized memory.
The <systemitem>--enable-gc-friendly</systemitem> option makes Glib
clear memory in these situations:
</para>
<itemizedlist>
<listitem>
<para>
When shrinking a GArray, Glib will clear the memory no longer
available in the array: shrink an array from 10 bytes to 7, and
the last 3 bytes will be cleared. This includes removals of single
and multiple elements.
</para>
</listitem>
<listitem>
<para>
When growing a GArray, Glib will clear the new chunk of memory.
Grow an array from 7 bytes to 10 bytes, and the last 3 bytes will
be cleared.
</para>
</listitem>
<listitem>
<para>
The above applies to GPtrArray as well.
</para>
</listitem>
<listitem>
<para>
When freeing a node from a GHashTable, Glib will first clear
the node, which used to have pointers to the key and the value
stored at that node.
</para>
</listitem>
<listitem>
<para>
When destroying or removing a GTree node, Glib will clear the node,
which used to have pointers to the node's value, and the left and
right subnodes.
</para>
</listitem>
</itemizedlist>
<para>
Since clearing the memory has a cost,
<systemitem>--disable-gc-friendly</systemitem> is the default.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-mem-pools</systemitem> and
<systemitem>--enable-mem-pools</systemitem></title>
<para>
Many small chunks of memory are often allocated via collective pools
in GLib and are cached after release to speed up reallocations.
For sparse memory systems this behaviour is often inferior, so
memory pools can be disabled to avoid excessive caching and force
atomic maintenance of chunks through the <function>g_malloc()</function>
and <function>g_free()</function> functions. Code currently affected by
this:
<itemizedlist>
<listitem>
<para>
<structname>GMemChunk</structname>s become basically non-effective
</para>
</listitem>
<listitem>
<para>
<structname>GSignal</structname> disables all caching
(potentially very slow)
</para>
</listitem>
<listitem>
<para>
<structname>GType</structname> doesn't honour the
<structname>GTypeInfo</structname>
<structfield>n_preallocs</structfield> field anymore
</para>
</listitem>
<listitem>
<para>
the <structname>GBSearchArray</structname> flag
<literal>G_BSEARCH_ALIGN_POWER2</literal> becomes non-functional
</para>
</listitem>
</itemizedlist>
</para>
</formalpara>
<formalpara>
<title><systemitem>--with-threads</systemitem></title>
<para>
Specify a thread implementation to use. Available options are
'posix' or 'win32'. Normally, <command>configure</command>
should be able to work out the system threads API on its own.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-regex</systemitem> and
<systemitem>--enable-regex</systemitem></title>
<para>
Do not compile GLib with regular expression support.
GLib will be smaller because it will not need the
PCRE library. This is however not recommended, as
programs may need GRegex.
</para>
</formalpara>
<formalpara>
<title><systemitem>--with-pcre</systemitem></title>
<para>
Specify whether to use the internal or the system-supplied
PCRE library.
<itemizedlist>
<listitem>
<para>
'internal' means that GRegex will be compiled to use
the internal PCRE library.
</para>
</listitem>
<listitem>
<para>
'system' means that GRegex will be compiled to use
the system-supplied PCRE library.
</para>
</listitem>
</itemizedlist>
Using the internal PCRE is the preferred solution:
<itemizedlist>
<listitem>
<para>
System-supplied PCRE has a separated copy of the big tables
used for Unicode handling.
</para>
</listitem>
<listitem>
<para>
Some systems have PCRE libraries compiled without some needed
features, such as UTF-8 and Unicode support.
</para>
</listitem>
<listitem>
<para>
PCRE uses some global variables for memory management and
other features. In the rare case of a program using both
GRegex and PCRE (maybe indirectly through a library),
this variables could lead to problems when they are modified.
</para>
</listitem>
</itemizedlist>
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-included-printf</systemitem> and
<systemitem>--enable-included-printf</systemitem></title>
<para>
By default the <command>configure</command> script will try
to auto-detect whether the C library provides a suitable set
of printf() functions. In detail, <command>configure</command>
checks that the semantics of snprintf() are as specified by C99
and that positional parameters as specified in the Single Unix
Specification are supported. If this not the case, GLib will
include an implementation of the printf() family.
</para>
<para>
These options can be used to explicitly control whether
an implementation of the printf() family should be included or not.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-Bsymbolic</systemitem> and
<systemitem>--enable-Bsymbolic</systemitem></title>
<para>
By default, GLib uses the -Bsymbolic-functions linker
flag to avoid intra-library PLT jumps. A side-effect
of this is that it is no longer possible to override
internal uses of GLib functions with
<envar>LD_PRELOAD</envar>. Therefore, it may make
sense to turn this feature off in some situations.
The <option>--disable-Bsymbolic</option> option allows
to do that.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-gtk-doc</systemitem> and
<systemitem>--enable-gtk-doc</systemitem></title>
<para>
By default the <command>configure</command> script will try
to auto-detect whether the
<application>gtk-doc</application> package is installed.
If it is, then it will use it to extract and build the
documentation for the GLib library. These options
can be used to explicitly control whether
<application>gtk-doc</application> should be
used or not. If it is not used, the distributed,
pre-generated HTML files will be installed instead of
building them on your machine.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-man</systemitem> and
<systemitem>--enable-man</systemitem></title>
<para>
By default the <command>configure</command> script will try
to auto-detect whether <application>xsltproc</application>
and the necessary Docbook stylesheets are installed.
If they are, then it will use them to rebuild the included
man pages from the XML sources. These options can be used
to explicitly control whether man pages should be rebuilt
used or not. The distribution includes pre-generated man
pages.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-xattr</systemitem> and
<systemitem>--enable-xattr</systemitem></title>
<para>
By default the <command>configure</command> script will try
to auto-detect whether the getxattr() family of functions
is available. If it is, then extended attribute support
will be included in GIO. These options can be used to
explicitly control whether extended attribute support
should be included or not. getxattr() and friends can
be provided by glibc or by the standalone libattr library.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-selinux</systemitem> and
<systemitem>--enable-selinux</systemitem></title>
<para>
By default the <command>configure</command> script will
auto-detect if libselinux is available and include
SELinux support in GIO if it is. These options can be
used to explicitly control whether SELinux support should
be included.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-dtrace</systemitem> and
<systemitem>--enable-dtrace</systemitem></title>
<para>
By default the <command>configure</command> script will
detect if DTrace support is available, and use it.
</para>
</formalpara>
<formalpara>
<title><systemitem>--disable-systemtap</systemitem> and
<systemitem>--enable-systemtap</systemitem></title>
<para>
This option requires DTrace support. If it is available, then
the <command>configure</command> script will also check for
the presence of SystemTap.
</para>
</formalpara>
<formalpara>
<title><systemitem>--enable-gcov</systemitem> and
<systemitem>--disable-gcov</systemitem></title>
<para>
Enable the generation of coverage reports for the GLib tests.
This requires the lcov frontend to gcov from the
<ulink url="http://ltp.sourceforge.net">Linux Test Project</ulink>.
To generate a coverage report, use the lcov make target. The
report is placed in the <filename>glib-lcov</filename> directory.
</para>
</formalpara>
<formalpara>
<title><systemitem>--with-runtime-libdir=RELPATH</systemitem></title>
<para>
Allows specifying a relative path to where to install the runtime
libraries (meaning library files used for running, not developing,
GLib applications). This can be used in operating system setups where
programs using GLib needs to run before e.g. <filename>/usr</filename>
is mounted.
For example, if LIBDIR is <filename>/usr/lib</filename> and
<filename>../../lib</filename> is passed to
<systemitem>--with-runtime-libdir</systemitem> then the
runtime libraries are installed into <filename>/lib</filename> rather
than <filename>/usr/lib</filename>.
</para>
</formalpara>
<formalpara>
<title><systemitem>--with-python</systemitem></title>
<para>
Allows specifying the Python interpreter to use, either as an absolute path,
or as a program name. GLib can be built with Python 2 (at least version 2.5)
or Python 3.
</para>
</formalpara>
</refsect1>
</refentry>