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<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 <application>Meson</application> build
      system. The normal sequence for compiling and installing the GLib library
      is thus:

      <literallayout>
        <userinput>meson _build</userinput>
        <userinput>ninja -C _build</userinput>
        <userinput>ninja -C _build install</userinput>
      </literallayout>
    </para>

    <para>
      The standard options provided by <application>Meson</application> may be
      passed to the <command>meson</command> command.  Please see the
      <application>Meson</application> documentation or run
      <command>meson configure --help</command> for information about
      the standard options.
    </para>
    <para>
      GLib is compiled with
      <ulink url="https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-fstrict-aliasing">strict aliasing</ulink>
      disabled. It is strongly recommended that this is not re-enabled by
      overriding the compiler flags, as GLib has not been tested with strict
      aliasing and cannot be guaranteed to work.
    </para>
    <para>
      The GTK+ documentation contains
      <ulink url="https://developer.gnome.org/gtk3/stable/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.
      If you are building from a release archive, you will need
      <ulink url="https://wiki.gnome.org/Projects/GLib/CompilerRequirements">a compliant C toolchain</ulink>,
      <application>Meson</application>, and <application>pkg-config</application>;
      the requirements are the same when building from a Git repository clone
      of GLib.
    </para>
    <itemizedlist>
      <listitem>
        <para>
          <ulink url="https://www.freedesktop.org/wiki/Software/pkg-config/">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).
        </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
          <option>-Diconv=gnu</option> option to <command>meson</command>. 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 system
          version of PCRE, to reduce the chances of security fixes going out
          of sync. GLib additionally provides an internal copy of PCRE in case
          the system version is too old, or does not support UTF-8; the internal
          copy is patched to use GLib for memory management and to share the
          same Unicode tables.
        </para>
      </listitem>
      <listitem>
        <para>
          The optional extended attribute support in GIO requires the
          <function>getxattr()</function> family of functions that may be
          provided by the C library or by the standalone libattr library. To
          build GLib without extended attribute support, use the
          <option>-Dxattr=false</option> option.
        </para>
      </listitem>
      <listitem>
        <para>
          The optional SELinux support in GIO requires libselinux.
          To build GLib without SELinux support, use the
          <option>-Dselinux=false</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>-Ddtrace=false</option> option.
        </para>
      </listitem>
      <listitem>
        <para>
          The optional support for
          <ulink url="http://sourceware.org/systemtap/">SystemTap</ulink>
          can be disabled with the <option>-Dsystemtap=false</option>
          option. Additionally, you can control the location
          where GLib installs the SystemTap probes, using the
          <option>-Dtapset_install_dir=DIR</option> option.
        </para>
      </listitem>
    </itemizedlist>

  </refsect1>
  <refsect1 id="extra-configuration-options">
    <title>Extra Configuration Options</title>

    <para>
      In addition to the normal options, these additional ones are supported
      when configuring the GLib library:
    </para>

    <formalpara>
      <title><option>--buildtype</option></title>

      <para>
        This is a standard <application>Meson</application> option which
        specifies how much debugging and optimization to enable. If the build
        type starts with <literal>debug</literal>,
        <literal>G_ENABLE_DEBUG</literal> will be defined and GLib will be built
        with additional debug code enabled.
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Dforce_posix_threads=true</option></title>

      <para>
        Normally, <application>Meson</application> should be able to work out
        the correct thread implementation to use. This option forces POSIX
        threads to be used even if the platform provides another threading API
        (for example, on Windows).
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Dinternal_pcre=true</option></title>

      <para>
        Normally, GLib will be configured to use the system-supplied PCRE
        library if it is suitable, falling back to an internal version
        otherwise. If this option is specified, the internal version will always
        be used.
      </para>
      <para>
        Using the internal PCRE is the preferred solution if:
        <itemizedlist>
          <listitem>
            <para>
              your system has strict resource constraints; the system-supplied
              PCRE has a separated copy of the tables used for Unicode
              handling, whereas the internal copy shares the Unicode tables
              used by GLib.
            </para>
          </listitem>
          <listitem>
            <para>
              your system has PCRE built without some needed features,
              such as UTF-8 and Unicode support.
            </para>
          </listitem>
          <listitem>
            <para>
              you are planning to use both GRegex and PCRE API at the same
              time, either directly or indirectly through a dependency; PCRE
              uses some global variables for memory management and
              other features, and if both GLib and PCRE try to access them
              at the same time, this could lead to undefined behavior.
            </para>
          </listitem>
        </itemizedlist>
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Dbsymbolic_functions=false</option> and
        <option>-Dbsymbolic_functions=true</option></title>

      <para>
        By default, GLib uses the <option>-Bsymbolic-functions</option>
        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>-Dbsymbolic_functions=false</option> option allows
        to do that.
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Dgtk_doc=false</option> and
        <option>-Dgtk_doc=true</option></title>

      <para>
        By default, GLib will 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><option>-Dman=false</option> and
        <option>-Dman=true</option></title>

      <para>
        By default, GLib will 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><option>-Dxattr=false</option> and
        <option>-Dxattr=true</option></title>

      <para>
        By default, GLib will detect whether the
        <function>getxattr()</function>
        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. <function>getxattr()</function>
        and friends can be provided by glibc or by the standalone
        libattr library.
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Dselinux=false</option> and
        <option>-Dselinux=true</option></title>

      <para>
        By default, GLib will 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><option>-Ddtrace=false</option> and
        <option>-Ddtrace=true</option></title>

      <para>
        By default, GLib will detect if DTrace support is available, and use it.
        These options can be used to explicitly control whether DTrace support
        is compiled into GLib.
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Dsystemtap=false</option> and
        <option>-Dsystemtap=true</option></title>

      <para>
        This option requires DTrace support. If it is available, then
        GLib will also check for the presence of SystemTap.
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Db_coverage=true</option> and
        <option>-Db_coverage=false</option></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
        <command>ninja coverage-html</command>. The report is placed in the
        <filename>meson-logs</filename> directory.
      </para>
    </formalpara>

    <formalpara>
      <title><option>-Druntime_libdir=RELPATH</option></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 <varname>LIBDIR</varname> is <filename>/usr/lib</filename> and
        <filename>../../lib</filename> is passed to
        <option>-Druntime_libdir</option> then the
        runtime libraries are installed into <filename>/lib</filename> rather
        than <filename>/usr/lib</filename>.
      </para>
    </formalpara>
  </refsect1>

</refentry>
