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

<sect1 id="ch05-gcc-pass1">
<title>Installing GCC-&gcc-version; - Pass 1</title>
<?dbhtml filename="gcc-pass1.html" dir="chapter05"?>

<screen>Estimated build time:           &gcc-time-tools-pass1;
Estimated required disk space:  &gcc-compsize-tools-pass1;</screen>

<para>For the package details see <xref linkend="contents-gcc"/>.</para>

<sect2><title>&nbsp;</title><para>&nbsp;</para></sect2>

<sect2>
<title>Installation of GCC</title>

<para>Unpack only the GCC-core tarball, as we won't be needing a C++ compiler
for the moment.</para>

<note><para>Even though GCC is an important toolchain package, we are not
going to run the test suite at this early stage. First, the test suite framework
is not yet in place and second, the programs from this first pass will soon be
overwritten by those installed in the second pass.</para></note>

<para>This package is known to behave badly when you have changed its
default optimization flags (including the -march and -mcpu options).
Therefore, if you have defined any environment variables that override
default optimizations, such as CFLAGS and CXXFLAGS, we recommend unsetting
or modifying 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 \
&nbsp;&nbsp;&nbsp;&nbsp;--with-local-prefix=/tools \
&nbsp;&nbsp;&nbsp;&nbsp;--disable-nls --enable-shared \
&nbsp;&nbsp;&nbsp;&nbsp;--enable-languages=c</userinput></screen>

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

<itemizedlist>
<listitem><para><userinput>--with-local-prefix=/tools</userinput>:  The
purpose of this switch is to remove <filename>/usr/local/include</filename>
from <userinput>gcc</userinput>'s include search path. This is not absolutely
essential; however, we want to try to minimize the influence of the host
system, thus making this a sensible thing to do.</para></listitem>

<listitem><para><userinput>--enable-shared</userinput>: This switch may
seem counter-intuitive at first. But using it allows the building of
<filename>libgcc_s.so.1</filename> and <filename>libgcc_eh.a</filename>, and
having <filename>libgcc_eh.a</filename> available ensures that the configure
script for Glibc (the next package we compile) produces the proper results.
Note that the <userinput>gcc</userinput> binaries will still be linked
statically, as this is controlled by the <userinput>-static</userinput>
value of BOOT_LDFLAGS further on.</para></listitem>

<listitem><para><userinput>--enable-languages=c</userinput>: This option
ensures that only the C compiler is built. The option is only needed when you
have downloaded and unpacked the full GCC tarball.</para></listitem>
</itemizedlist>

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

<screen><userinput>make BOOT_LDFLAGS="-static" bootstrap</userinput></screen>

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

<itemizedlist>
<listitem><para><userinput>BOOT_LDFLAGS="-static"</userinput>: This tells
GCC to link its programs statically.</para></listitem>

<listitem><para><userinput>bootstrap</userinput>: This target doesn't 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, which most probably means that it was
compiled correctly.</para></listitem>
</itemizedlist>

<para>And install the package:</para>

<screen><userinput>make install</userinput></screen>

<para>As a finishing touch we'll create the <filename
class="symlink">/tools/bin/cc</filename> symlink. Many programs and
scripts run <userinput>cc</userinput> instead of <userinput>gcc</userinput>,
a thing meant to keep programs generic and therefore usable on all kinds of
Unix systems. Not everybody has the GNU C compiler installed. Simply running
<userinput>cc</userinput> leaves the system administrator free to decide what
C compiler to install, as long as there's a symlink pointing to it:</para>

<screen><userinput>ln -sf gcc /tools/bin/cc</userinput></screen>

</sect2>

</sect1>