lfs-book-zh_CN/chapter05/gcc-pass1.xml

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<sect1 id="ch-tools-gcc-pass1" role="wrap">
<title>GCC-&gcc-version; - Pass 1</title>
<?dbhtml filename="gcc-pass1.html"?>

<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>4.4 SBU</seg><seg>300 MB</seg></seglistitem>
</segmentedlist>

<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="../chapter06/gcc.xml" xpointer="xpointer(/sect1/sect2[1]/segmentedlist[2])"/>

</sect2>

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

<para>Unpack only the gcc-core tarball because neither the C++
compiler nor the test suite will be needed here.</para>

<para>This package is known to have issues when its default
optimization flags (including the <parameter>-march</parameter> and
<parameter>-mcpu</parameter> options) are changed. If any environment
variables that override default optimizations have been defined, such
as <envar>CFLAGS</envar> and <envar>CXXFLAGS</envar>,
unset them when building GCC.</para>

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

<screen><userinput>mkdir ../gcc-build
cd ../gcc-build</userinput></screen>

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

<screen><userinput>../gcc-&gcc-version;/configure --prefix=/tools \
    --libexecdir=/tools/lib --with-local-prefix=/tools \
    --disable-nls --enable-shared --enable-languages=c</userinput></screen>

<para>The meaning of the configure options:</para>

<variablelist>
<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>--enable-shared</parameter></term>
<listitem><para>This switch allows the building of
<filename class="libraryfile">libgcc_s.so.1</filename> and
<filename class="libraryfile">libgcc_eh.a</filename>.  Having
<filename class="libraryfile">libgcc_eh.a</filename> available ensures that the
configure script for Glibc (the next package we compile) produces the proper
results.</para></listitem>
</varlistentry>

<varlistentry>
<term><parameter>--enable-languages=c</parameter></term>
<listitem><para>This option ensures that only the C compiler is built.
This option is only needed when you have downloaded and unpacked the
full GCC tarball, as opposed to just the gcc-core
tarball.</para></listitem>
</varlistentry>
</variablelist>

<para>Continue with compiling the package:</para>

<screen><userinput>make bootstrap</userinput></screen>

<para>The meaning of the make parameters:</para>

<variablelist>
<varlistentry>
<term><parameter>bootstrap</parameter></term>
<listitem><para>This target does not just compile GCC, but compiles it
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 also implies that it was compiled
correctly.</para></listitem>
</varlistentry>
</variablelist>

<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>make install</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>ln -s 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>