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  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
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<sect1 id="ch-system-libffi" role="wrap">
  <?dbhtml filename="libffi.html"?>

  <sect1info condition="script">
    <productname>libffi</productname>
    <productnumber>&libffi-version;</productnumber>
    <address>&libffi-url;</address>
  </sect1info>

  <title>Libffi-&libffi-version;</title>

  <indexterm zone="ch-system-libffi">
    <primary sortas="a-libffi">libffi</primary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The Libffi library provides a portable, high level programming
    interface to various calling conventions. This allows a programmer to call
    any function specified by a call interface description at run time.</para>
  
    <para>FFI stands for Foreign Function Interface. An FFI allows a program written
    in one language to call a program written in another language. Specifically,
    Libffi can provide a bridge between an interpreter like Perl, or Python, and
    shared library subroutines written in C, or C++.</para>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&libffi-fin-sbu;</seg>
        <seg>&libffi-fin-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

  <sect2 role="installation">
    <title>Installation of Libffi</title>

    <note>
      <para>Like GMP, Libffi builds with optimizations specific
      to the processor in use. If building for another system, change the
      value of the <parameter>--with-gcc-arch=</parameter> parameter in the
      following command to an architecture name fully implemented by
      <emphasis role='bold'>both</emphasis> the host CPU and the
      CPU on that system.
      If this is not done, all applications that link to
      <filename class='libraryfile'>libffi</filename> will trigger
      Illegal Operation Errors.  If you cannot figure out a value
      safe for both the CPUs, replace the parameter with
      <option>--without-gcc-arch</option> to produce a generic library.</para>
    </note>

    <para>Prepare Libffi for compilation:</para>

    <screen><userinput remap="configure">./configure --prefix=/usr          \
            --disable-static       \
            --with-gcc-arch=native</userinput></screen>

    <variablelist>
      <title>The meaning of the configure option:</title>

      <varlistentry>
        <term><parameter>--with-gcc-arch=native</parameter></term>
        <listitem>
          <para>Ensure GCC optimizes for the current system.  If this
          is not specified, the system is guessed and the code generated
          may not be correct.  If the generated code
          will be copied from the native system to a less capable
          system, use the less capable system as a parameter. For details
          about alternative system types, see <ulink
          url='https://gcc.gnu.org/onlinedocs/gcc-&gcc-version;/gcc/x86-Options.html'>
          the x86 options in the GCC manual</ulink>.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>Compile the package:</para>

<screen><userinput remap="make">make</userinput></screen>

    <para>To test the results, issue:</para>

<screen><userinput remap="test">make check</userinput></screen>

    <para>Install the package:</para>

<screen><userinput remap="install">make install</userinput></screen>

  </sect2>

  <sect2 id="contents-libffi" role="content">
    <title>Contents of Libffi</title>

    <segmentedlist>
      <segtitle>Installed library</segtitle>

      <seglistitem>
        <seg>libffi.so</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="libffi">
        <term><filename class="libraryfile">libffi</filename></term>
        <listitem>
          <para>Contains the foreign function interface API functions</para>
          <indexterm zone="ch-system-libffi">
            <primary sortas="c-libffi">libffi</primary>
          </indexterm>
        </listitem>
      </varlistentry>
    </variablelist>

  </sect2>

</sect1>