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<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
%general-entities;
]>
<sect1 id="ch-tools-gcc-pass2" role="wrap" xreflabel="gcc-pass2">
<?dbhtml filename="gcc-pass2.html"?>
<sect1info condition="script">
<productname>gcc-pass2</productname>
<productnumber>&gcc-version;</productnumber>
<address>&gcc-url;</address>
</sect1info>
<title>GCC-&gcc-version; - Pass 2</title>
<indexterm zone="ch-tools-gcc-pass2">
<primary sortas="a-GCC">GCC</primary>
<secondary>tools, pass 2</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-tmpp2-sbu;</seg>
<seg>&gcc-tmpp2-du;</seg>
</seglistitem>
</segmentedlist>
</sect2>
<sect2 role="installation">
<title>Installation of GCC</title>
<para>As in the first build of GCC, the GMP, MPFR, and MPC packages are
required. Unpack the tarballs and move them into the required directory
names:</para>
<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>If building on x86_64, change the default directory name for 64-bit
libraries to <quote>lib</quote>:</para>
<screen><userinput remap="pre">case $(uname -m) in
x86_64)
sed -e '/m64=/s/lib64/lib/' -i.orig gcc/config/i386/t-linux64
;;
esac</userinput></screen>
<para>Override the building rule of libgcc and libstdc++ headers, to
allow building these libraries with POSIX threads support:</para>
<screen><userinput remap="pre">sed '/thread_header =/s/@.*@/gthr-posix.h/' \
-i libgcc/Makefile.in libstdc++-v3/include/Makefile.in</userinput></screen>
<para>Create a separate build directory again:</para>
<screen><userinput remap="pre">mkdir -v build
cd build</userinput></screen>
<para>Before starting to build GCC, remember to unset any environment
variables that override the default optimization flags.</para>
<para>Now prepare GCC for compilation:</para>
<screen><userinput remap="configure">../configure \
--build=$(../config.guess) \
--host=$LFS_TGT \
--target=$LFS_TGT \
LDFLAGS_FOR_TARGET=-L$PWD/$LFS_TGT/libgcc \
--prefix=/usr \
--with-build-sysroot=$LFS \
--enable-initfini-array \
--disable-nls \
--disable-multilib \
--disable-decimal-float \
--disable-libatomic \
--disable-libgomp \
--disable-libquadmath \
--disable-libssp \
--disable-libvtv \
--enable-languages=c,c++</userinput></screen>
<variablelist>
<title>The meaning of the new configure options:</title><!-- WIP -->
<varlistentry>
<term><parameter>--with-build-sysroot=$LFS</parameter></term>
<listitem>
<para>Normally, using <parameter>--host</parameter> ensures that
a cross-compiler is used for building GCC, and that compiler knows
that it has to look for headers and libraries in <filename
class="directory">$LFS</filename>. But the build system of GCC uses
other tools, which are not aware of this location. This switch is
needed to have them find the needed files in <filename
class="directory">$LFS</filename>, and not on the host.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>--target=$LFS_TGT</parameter></term>
<listitem>
<para>As we are cross-compiling GCC, it's impossible to build
target libraries (<filename class="libraryfile">libgcc</filename>
and <filename class="libraryfile">libstdc++</filename>) with the
compiled GCC binaries because these binaries won't run on the
host distro. GCC building system will attempt to use the
C and C++ compilers on the host distro as a workaround by default.
It's not supported to build GCC target libraries with a different
version of GCC, so using host compilers may cause building
failure. This parameter ensures to build the libraries with GCC
pass 1 and prevent the issue.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>LDFLAGS_FOR_TARGET=...</parameter></term>
<listitem>
<para>Allow <filename class="libraryfile">libstdc++</filename> to
use shared <filename class="libraryfile">libgcc</filename> being
built in this pass, instead of the static version built in GCC
pass 1. This is needed for supporting C++ exception
handling.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>--enable-initfini-array</parameter></term>
<listitem>
<para>This option is automatically enabled when building a native
compiler with a native compiler on x86. But here, we build with
a cross compiler, so we need to explicitly set this option.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Compile the package:</para>
<screen><userinput remap="make">make</userinput></screen>
<para>Install the package:</para>
<screen><userinput remap="install">make DESTDIR=$LFS install</userinput></screen>
<para>As a finishing touch, create a utility 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 -sv gcc $LFS/usr/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>
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