building.sgml

This GLib version 2.16.1. GLib is the low-level core library that forms the basis for projects such

        </listitem>
        <listitem>
	  <para>
	  </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>
        <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>GList</structname>, <structname>GSList</structname>,
         <structname>GNode</structname>, <structname>GHash</structname> 
         allocations. The functions g_list_push_allocator(), 
         g_list_pop_allocator(), g_slist_push_allocator(), 
         g_slist_pop_allocator(), g_node_push_allocator() and 
         g_node_pop_allocator() are not available
        </para>
        </listitem>
        <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>--disable-threads</systemitem> and
          <systemitem>--enable-threads</systemitem></title>

        <para>
           Do not compile GLib to be multi thread safe. GLib
           will be slightly faster then. This is however not
           recommended, as many programs rely on GLib being
           multi thread safe.
        </para>
      </formalpara>

      <formalpara>
        <title><systemitem>--with-threads</systemitem></title>

        <para>
          Specify a thread implementation to use.
          <itemizedlist>
              <listitem><para>
                'posix' and 'dce' can be used interchangeable
                to mean the different versions of Posix
                threads. configure tries to find out, which
                one is installed.
              </para></listitem>

              <listitem><para>
                'none' means that GLib will be thread safe,
                but does not have a default thread
                implementation. This has to be supplied to
                <function>g_thread_init()</function> by the programmer.
              </para></listitem>
        </itemizedlist>

        </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 <function>printf()</function> functions. In detail, 
	  <command>configure</command> checks that the semantics of
          <function>snprintf()</function> 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 <function>printf()</function> 
          family.
          These options can be used to explicitly control whether
          an implementation fo the <function>printf()</function> family
          should be included or not.
        </para>
      </formalpara>

      <formalpara>
         <title><systemitem>--disable-visibility</systemitem> and
           <systemitem>--enable-visibility</systemitem></title>

        <para>
          By default, GLib uses ELF visibility attributes to optimize
          PLT table entries if the compiler supports ELF visibility
          attributes. A side-effect of the way in which this is currently
          implemented is that any  header change forces a full 
          recompilation, and missing includes may go unnoticed. 
          Therefore, it makes sense to turn this feature off while
          doing GLib development, even if the compiler supports ELF
          visibility attributes. The <option>--disable-visibility</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 SELinxu support should
	  be included.
        </para>
     </formalpara>
   </refsect1>

</refentry>