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/2001/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 Cross GCC</title>

    <para>GCC now requires the GMP, MPFR and MPC packages. As these packages may
    not be included in your host distribution, they will be built with
    GCC.  Unpack each package into the GCC source directory and rename the
    resulting directories so the GCC build procedures will automatically
    use them:</para>

    <note><para>There are frequent misunderstandings about this chapter.  The
    procedures are the same as every other chapter as explained earlier (<xref
    linkend='buildinstr'/>).  First extract the gcc tarball from the sources
    directory and then change to the directory created.  Only then should you
    proceed with the instructions below.</para></note>

<screen><userinput remap="pre">tar -Jxf ../mpfr-&mpfr-version;.tar.xz
mv -v mpfr-&mpfr-version; mpfr
tar -Jxf ../gmp-&gmp-version;.tar.xz
mv -v gmp-&gmp-version; gmp
tar -zxf ../mpc-&mpc-version;.tar.gz
mv -v mpc-&mpc-version; mpc</userinput></screen>

    <para>The following command will change the location of GCC's default
    dynamic linker to use the one installed in <filename
    class="directory">/tools</filename>. It also removes <filename
    class="directory">/usr/include</filename> from GCC's include search path.
    Issue:</para>

<screen><userinput remap="pre">for file in \
 $(find gcc/config -name linux64.h -o -name linux.h -o -name sysv4.h)
do
  cp -uv $file{,.orig}
  sed -e 's@/lib\(64\)\?\(32\)\?/ld@/tools&amp;@g' \
      -e 's@/usr@/tools@g' $file.orig &gt; $file
  echo '
#undef STANDARD_STARTFILE_PREFIX_1
#undef STANDARD_STARTFILE_PREFIX_2
#define STANDARD_STARTFILE_PREFIX_1 "/tools/lib/"
#define STANDARD_STARTFILE_PREFIX_2 ""' &gt;&gt; $file
  touch $file.orig
done</userinput></screen>

    <para>In case the above seems hard to follow, let's break it down a bit.
    First we find all the files under the <filename
    class="directory">gcc/config</filename> directory that are named either
    <filename>linux.h</filename>, <filename>linux64.h</filename> or
    <filename>sysv4.h</filename>.  For each file found, we copy it to a file of
    the same name but with an added suffix of <quote>.orig</quote>. Then the
    first sed expression prepends <quote>/tools</quote> to every instance of
    <quote>/lib/ld</quote>, <quote>/lib64/ld</quote> or
    <quote>/lib32/ld</quote>, while the second one replaces hard-coded
    instances of <quote>/usr</quote>. Next, we add our define statements which
    alter the default startfile prefix to the end of the file. Note that the
    trailing <quote>/</quote> in <quote>/tools/lib/</quote> is required.
    Finally, we use <command>touch</command> to update the timestamp on the
    copied files.  When used in conjunction with <command>cp -u</command>, this
    prevents unexpected changes to the original files in case the commands are
    inadvertently run twice.  </para>

    <para>GCC doesn't detect stack protection correctly, which causes problems
    for the build of Glibc-&glibc-version;, so fix that by issuing the following
    command:</para>

<screen><userinput remap="pre">sed -i '/k prot/agcc_cv_libc_provides_ssp=yes' gcc/configure</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">../gcc-&gcc-version;/configure         \
    --target=$LFS_TGT          \
    --prefix=/tools            \
    --with-sysroot=$LFS        \
    --with-newlib              \
    --without-headers          \
    --with-local-prefix=/tools \
    --with-native-system-header-dir=/tools/include \
    --disable-nls              \
    --disable-shared           \
    --disable-multilib         \
    --disable-decimal-float    \
    --disable-threads          \
    --disable-libmudflap       \
    --disable-libssp           \
    --disable-libgomp          \
    --disable-libquadmath      \
    --enable-languages=c       \
    --with-mpfr-include=$(pwd)/../gcc-&gcc-version;/mpfr/src \
    --with-mpfr-lib=$(pwd)/mpfr/src/.libs</userinput></screen>

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

      <varlistentry>
        <term><parameter>--with-newlib</parameter></term>
        <listitem>
          <para>Since a working C library is not yet available, this ensures
          that the inhibit_libc constant is defined when building libgcc. This prevents
          the compiling of any code that requires libc support.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--without-headers</parameter></term>
        <listitem>
          <para>When creating a complete cross-compiler, GCC requires
          standard headers compatible with the target system. For our
          purposes these headers will not be needed. This switch prevents
          GCC from looking for them.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-local-prefix=/tools</parameter></term>
        <listitem>
          <para>The local prefix is the location in the system that GCC will search
          for locally installed include files. The default is <filename>/usr/local</filename>.
          Setting this to <filename>/tools</filename> helps keep the host location of
          <filename>/usr/local</filename> out of this GCC's search path.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-native-system-header-dir=/tools/include</parameter></term>
        <listitem>
          <para>By default GCC searches <filename>/usr/include</filename> for system
          headers. In conjunction with the sysroot switch, this would translate normally
          to <filename>$LFS/usr/include</filename>. However the headers that will be installed
          in the next two sections will go to <filename>$LFS/tools/include</filename>. This
          switch ensures that gcc will find them correctly. In the second pass of GCC, this
          same switch will ensure that no headers from the host system are found.</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-decimal-float, --disable-threads, --disable-libmudflap, --disable-libssp, --disable-libgomp, --disable-libquadmath</parameter></term>
        <listitem>
          <para>These switches disable support for the decimal floating point
          extension, threading, libmudflap, libssp and libgomp and libquadmath
          respectively. These features will fail to compile when building a
          cross-compiler and are not necessary for the task of cross-compiling
          the temporary libc.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-multilib</parameter></term>
        <listitem>
          <para>On x86_64, LFS does not yet support a multilib configuration.
          This switch is harmless for x86.</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>

    </variablelist>

    <para>Compile GCC 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. This dependency
    can be satisfied 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 -sv libgcc.a `$LFS_TGT-gcc -print-libgcc-file-name | sed 's/libgcc/&amp;_eh/'`</userinput></screen>

  </sect2>

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

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

  </sect2>

</sect1>