building.sgml

一套linux glib源代码

        <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>
      </formalpara>

      <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>
	  </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-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>

   </refsect1>

</refentry>