lfs-book/chapter05/gcc-pass1.xml

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<sect1 id="ch-tools-gcc-pass1" role="wrap">
  <?dbhtml filename="gcc-pass1.html"?>

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

  <title>GCC-&gcc-version; - Pass 1</title>

  <indexterm zone="ch-tools-gcc-pass1">
    <primary sortas="a-GCC">GCC</primary>
    <secondary>tools, pass 1</secondary>
  </indexterm>

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

    <xi:include xmlns:xi="http://www.w3.org/2003/XInclude"
    href="../chapter06/gcc.xml"
    xpointer="xpointer(/sect1/sect2[1]/para[1])"/>

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

      <seglistitem>
        <seg>&gcc-ch5p1-sbu;</seg>
        <seg>&gcc-ch5p1-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

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

    <para>GCC now requires the GMP and MPFR packages. As these packages may
    not be included in your host distribution, they will be built with
    GCC.</para>

<screen><userinput remap="pre">tar -jxf ../mpfr-&mpfr-version;.tar.bz2
mv mpfr-&mpfr-version; mpfr
tar -jxf ../gmp-&gmp-version;.tar.bz2
mv gmp-&gmp-version; gmp</userinput></screen>

    <para>The GCC documentation recommends building GCC outside of the
    source directory in a dedicated build directory:</para>

<screen><userinput remap="pre">mkdir -v ../gcc-build
cd ../gcc-build</userinput></screen>

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

<screen><userinput remap="configure">CC="gcc -B/usr/bin/" ../gcc-&gcc-version;/configure --prefix=/tools \
    --with-local-prefix=/tools --disable-nls --disable-shared --disable-libssp \
    --enable-languages=c</userinput></screen>

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

      <varlistentry>
        <term><envar>CC="gcc -B/usr/bin/"</envar></term>
        <listitem>
          <para>This forces <command>gcc</command> to prefer the linker from
          the host in <filename class="directory">/usr/bin</filename>. This
          is necessary on some hosts where the new <command>ld</command>
          built in the previous section is not compatible with the host's
          <command>gcc</command>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-local-prefix=/tools</parameter></term>
        <listitem>
          <para>The purpose of this switch is to remove <filename
          class="directory">/usr/local/include</filename> from
          <command>gcc</command>'s include search path. This is not
          absolutely essential, however, it helps to minimize the
          influence of the host system.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-shared</parameter></term>
        <listitem>
          <para>This switch forces GCC to link its internal libraries
          statically. We do this to avoid possible issues with the host
          system.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-libssp</parameter></term>
        <listitem>
          <para>This switch prevents a conflict with older versions of 
          glibc which can cause the build to fail.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--enable-languages=c</parameter></term>
        <listitem>
          <para>This option ensures that only the C compiler is built.
          This is the only language needed now.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-multilib</parameter></term>
        <listitem>
          <para>We currently only want to build support for 64-bit libraries.</para>
        </listitem>
      </varlistentry>

    </variablelist>

    <para>The following command will compile GCC not once, but several times. It
    uses the programs compiled in a first round to compile itself a second time,
    and then again a third time. It then compares these second and third compiles
    to make sure it can reproduce itself flawlessly. This is called
    <quote>bootstrapping</quote>. Building GCC in this way ensures that it was
    compiled correctly and is now the default configuration for the released
    package. Continue with compiling by running:</para>

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

    <para>Compilation is now complete. At this point, the test suite would
    normally be run, but, as mentioned before, the test suite framework is
    not in place yet. The benefits of running the tests at this point
    are minimal since the programs from this first pass will soon be
    replaced.</para>

    <para>Install the package:</para>

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

    <para>Using <parameter>--disable-shared</parameter> means that the
    <filename>libgcc_eh.a</filename> file isn't created and installed. The
    Glibc package depends on this library as it uses
    <parameter>-lgcc_eh</parameter> within its build system. We can satisfy
    that dependency by creating a symlink to <filename>libgcc.a</filename>,
    since that file will end up containing the objects normally contained in
    <filename>libgcc_eh.a</filename>.</para>

<screen><userinput remap="install">ln -vs libgcc.a `gcc -print-libgcc-file-name | \
    sed 's/libgcc/&amp;_eh/'`</userinput></screen>

    <para>As a finishing touch, create a symlink. Many programs and scripts
    run <command>cc</command> instead of <command>gcc</command>, which is
    used to keep programs generic and therefore usable on all kinds of UNIX
    systems where the GNU C compiler is not always installed. Running
    <command>cc</command> leaves the system administrator free to decide
    which C compiler to install:</para>

<screen><userinput remap="install">ln -vs gcc /tools/bin/cc</userinput></screen>

  </sect2>

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

    <para>Details on this package are located in
    <xref linkend="contents-gcc" role="."/></para>

  </sect2>

</sect1>