lfs/chapter05/gcc-pass1.xml

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

  <sect1info condition="script">
    <productname>gcc-pass1</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="../chapter08/gcc.xml"
    xpointer="xpointer(/sect1/sect2[1]/para[1])"/>

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

      <seglistitem>
        <seg>&gcc-tmpp1-sbu;</seg>
        <seg>&gcc-tmpp1-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

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

    <para>GCC 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-&gcc-version; 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 -xf ../mpfr-&mpfr-version;.tar.xz
mv -v mpfr-&mpfr-version; mpfr
tar -xf ../gmp-&gmp-version;.tar.xz
mv -v gmp-&gmp-version; gmp
tar -xf ../mpc-&mpc-version;.tar.gz
mv -v mpc-&mpc-version; mpc</userinput></screen>

    <para>On 64-bit MIPS hosts, set the default directory name for
    64-bit libraries to <quote>lib</quote>:</para>

<screen><userinput remap="pre">sed -e 's/lib64/lib/' \
    -i.orig gcc/config/mips/{mips.h,t-linux64}</userinput></screen>

    <para>The GCC documentation recommends building GCC
    in a dedicated build directory:</para>

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

    <para>Probe the NaN encoding of the CPU:</para>

<screen><userinput remap="pre">cat > nan2008.c &lt;&lt; \EOF
<literal>#include &lt;stdio.h&gt;
int main()
{
  int x;
  asm("cfc1\t%0,$31":"=r"(x));
  return !(x &amp; 1 &lt;&lt; 18);
}</literal>
EOF
gcc nan2008.c -o nan2008
if ! grep -q nan_legacy /proc/cpuinfo &amp;&amp;
   (grep -q nan_2008 /proc/cpuinfo || ./nan2008) then
  NAN_SWITCH=--with-nan=2008
fi</userinput></screen>

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

<screen><userinput remap="configure">../configure                  \
    --target=$LFS_TGT         \
    --prefix=$LFS/tools       \
    --with-arch=mips64r2      \
    --with-glibc-version=&glibc-version; \
    --with-sysroot=$LFS       \
    --with-newlib             \
    --without-headers         \
    --enable-default-pie      \
    --enable-default-ssp      \
    --disable-nls             \
    --disable-shared          \
    --disable-multilib        \
    --disable-threads         \
    --disable-libatomic       \
    --disable-libgomp         \
    --disable-libquadmath     \
    --disable-libssp          \
    --disable-libvtv          \
    --disable-libstdcxx       \
    --enable-languages=c,c++  \
    $NAN_SWITCH

unset NAN_SWITCH</userinput></screen>
    <variablelist>
      <title>The meaning of the configure options:</title>

      <varlistentry>
        <term><parameter>--with-arch=mips64r2</parameter></term>
        <listitem>
          <para>Set the default value of <option>-march=</option> to
          mips64r2.  Most distros use it as the baseline for the MIPS port,
          so we are doing the same.  You may change it if your CPU is not
          compatible with mips64r2 (for example, mips3 or mips64r6), or
          your CPU is stronger than mips64r2 and you don't care about the
          compatibility with mips64r2, but we've not tested any setting
          other than mips64r2.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-glibc-version=&glibc-version;</parameter></term>
        <listitem>
          <para>This option specifies the version of Glibc which will be
          used on the target. It is not relevant to the libc of the host
          distro because everything compiled by pass1 GCC will run in the
          chroot environment, which is isolated from libc of the host
          distro.</para>
        </listitem>
      </varlistentry>

      <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>--enable-default-pie and
      --enable-default-ssp</parameter></term>
        <listitem>
          <para>Those switches allow GCC to compile programs with
           some hardening security features (more information on those in
           the <xref linkend="pie-ssp-info"/> in chapter 8) by default. They
           are not strictly needed at this stage, since the compiler will
           only produce temporary executables. But it is cleaner to have the
           temporary packages be as close as possible to the final ones.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-shared</parameter></term>
        <listitem>
          <para>This switch forces GCC to link its internal libraries
          statically. We need this because the shared libraries require Glibc,
          which is not yet installed on the target system.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-multilib</parameter></term>
        <listitem>
          <para>On 64-bit MIPS, LFS does not support a multilib configuration.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-threads,
        --disable-libatomic, --disable-libgomp,
        --disable-libquadmath, --disable-libssp, --disable-libvtv,
        --disable-libstdcxx</parameter></term>
        <listitem>
          <para>These switches disable support for
          threading, libatomic, libgomp, libquadmath, libssp,
          libvtv, and the C++ standard library respectively. These features
          may 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>--enable-languages=c,c++</parameter></term>
        <listitem>
          <para>This option ensures that only the C and C++ compilers are built.
          These are the only languages needed now.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>$NAN_SWITCH</parameter></term>
        <listitem>
          <para>If the CPU encodes NaN (Not a Number) values following
          IEEE 754-2008 (indicated by the 16th bit of FCSR), this variable
          will be set to <option>--with-nan=2008</option> so GCC will be
          configured to use the IEEE 754-2008 encoding for NaN values as
          the default.  If this option is not properly set to match the CPU,
          depending on the host kernel configuration, the programs compiled
          by GCC may fail to start with
          <computeroutput>Exec format error</computeroutput> (causing
          <xref linkend='ch-tools-chroot'/> to fail), or produce bad results
          (causing test failures building some packages, for example Glibc
          and Python).</para>
        </listitem>
      </varlistentry>

    </variablelist>

    <para>Compile GCC by running:</para>

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

    <para>Install the package:</para>

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

    <para>This build of GCC has installed a couple of internal system
    headers.  Normally one of them, <filename>limits.h</filename>, would in turn
    include the corresponding system <filename>limits.h</filename> header, in
    this case, <filename>$LFS/usr/include/limits.h</filename>. However, at the
    time of this build of GCC <filename>$LFS/usr/include/limits.h</filename>
    does not exist, so the internal header that has just been installed is a
    partial, self-contained file and does not include the extended features of
    the system header. This is adequate for building Glibc, but the full
    internal header will be needed later.  Create a full version of the internal
    header using a command that is identical to what the GCC build system does
    in normal circumstances:</para>

    <note>
      <para>The command below shows an example of nested command substitution
      using two methods: backquotes and a <literal>$()</literal> construct. 
      It could be rewritten using the same method for both substitutions,
      but is shown this way to demonstrate how they can be mixed.  Generally
      the <literal>$()</literal> method is preferred.</para>
    </note>

<screen><userinput remap="install">cd ..
cat gcc/limitx.h gcc/glimits.h gcc/limity.h > \
  `dirname $($LFS_TGT-gcc -print-libgcc-file-name)`/include/limits.h</userinput></screen>
  </sect2>

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

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

  </sect2>

</sect1>