mirror of https://github.com/tLDP/LDP
175 lines
8.0 KiB
XML
175 lines
8.0 KiB
XML
<sect1 id="ch05-gcc-pass2">
|
|
<title>Installing GCC-&gcc-version; - Pass 2</title>
|
|
<?dbhtml filename="gcc-pass2.html" dir="chapter05"?>
|
|
|
|
<screen>Estimated build time: &gcc-time-tools-pass2;
|
|
Estimated required disk space: &gcc-compsize-tools-pass2;</screen>
|
|
|
|
|
|
<sect2><title> </title><para> </para></sect2>
|
|
|
|
<sect2>
|
|
<title>Re-installation of GCC</title>
|
|
|
|
<para>The tools required to test GCC and Binutils are installed now (Tcl, Expect
|
|
and DejaGnu). We can continue on rebuilding GCC and Binutils, link them against
|
|
the new Glibc, and test them properly. One thing to note, however, is that these
|
|
test suites are highly dependent on properly functioning pseudo terminals (PTYs)
|
|
which are provided by your host distribution. These days, PTYs are most commonly
|
|
implemented via the <emphasis>devpts</emphasis> file system. You can quickly
|
|
check if your host system is set up correctly in this regard by performing a
|
|
simple test:</para>
|
|
|
|
<screen><userinput>expect -c "spawn ls"</userinput></screen>
|
|
|
|
<para>If you receive the message:</para>
|
|
|
|
<blockquote><screen>The system has no more ptys. Ask your system administrator to create more.</screen></blockquote>
|
|
|
|
<para>Your host distribution is not set up for proper PTY operation. In this
|
|
case there is no point in running the test suites for GCC and Binutils until you
|
|
are able to resolve the issue. You can consult the LFS Wiki at
|
|
<ulink url="http://wiki.linuxfromscratch.org/"/> for more information on how to
|
|
get PTYs working.</para>
|
|
|
|
<para>Unpack all three GCC tarballs (-core, -g++, and -testsuite) in one and the
|
|
same working directory. They will all unfold into a single
|
|
<filename>gcc-&gcc-version;/</filename> subdirectory.</para>
|
|
|
|
<para>First correct one problem and make an essential adjustment:</para>
|
|
|
|
<screen><userinput>patch -Np1 -i ../&gcc-nofixincludes-patch;
|
|
patch -Np1 -i ../&gcc-specs-patch;</userinput></screen>
|
|
|
|
<para>The first patch disables the GCC "fixincludes" script. We mentioned this
|
|
briefly earlier, but a slightly more in-depth explanation of the fixincludes
|
|
process is warranted here. Under normal circumstances, the GCC fixincludes
|
|
script scans your system for header files that need to be fixed. It might find
|
|
that some Glibc header files on your host system need to be fixed, fix them and
|
|
put them in the GCC private include directory. Then, later on in
|
|
<xref linkend="chapter06"/>, after we've installed the newer Glibc, this
|
|
private include directory would be searched before the system include
|
|
directory, resulting in GCC finding the fixed headers from the host system,
|
|
which would most likely not match the Glibc version actually used for the LFS
|
|
system.</para>
|
|
|
|
<para>The last patch changes GCC's default location of the dynamic linker
|
|
(typically <filename>ld-linux.so.2</filename>). It also removes
|
|
<filename class="directory">/usr/include</filename> from GCC's include search
|
|
path. Patching now rather than adjusting the specs file after installation
|
|
ensures that our new dynamic linker gets used during the actual build of GCC.
|
|
That is, all the final (and temporary) binaries created during the build will
|
|
link against the new Glibc.</para>
|
|
|
|
<important><para>These patches are <emphasis>critical</emphasis> in ensuring a
|
|
successful overall build. Do not forget to apply them.</para></important>
|
|
|
|
<para>Create a separate build directory again:</para>
|
|
|
|
<screen><userinput>mkdir ../gcc-build
|
|
cd ../gcc-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>../gcc-&gcc-version;/configure --prefix=/tools \
|
|
--with-local-prefix=/tools \
|
|
--enable-clocale=gnu --enable-shared \
|
|
--enable-threads=posix --enable-__cxa_atexit \
|
|
--enable-languages=c,c++</userinput></screen>
|
|
|
|
<para>The meaning of the new configure options:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem><para><userinput>--enable-threads=posix</userinput>: This enables
|
|
C++ exception handling for multi-threaded code.</para></listitem>
|
|
|
|
<listitem><para><userinput>--enable-__cxa_atexit</userinput>: This option
|
|
allows use of __cxa_atexit, rather than atexit, to register C++ destructors for
|
|
local statics and global objects and is essential for fully standards-compliant
|
|
handling of destructors. It also affects the C++ ABI and therefore results in
|
|
C++ shared libraries and C++ programs that are interoperable with other Linux
|
|
distributions.</para></listitem>
|
|
|
|
<listitem><para><userinput>--enable-clocale=gnu</userinput>: This option ensures
|
|
the correct locale model is selected for the C++ libraries under all
|
|
circumstances. If the configure script finds the <emphasis>de_DE</emphasis>
|
|
locale installed, it will select the correct model of <emphasis>gnu</emphasis>.
|
|
However, people who don't install the <emphasis>de_DE</emphasis> locale, run the
|
|
risk of building ABI incompatible C++ libraries due to the wrong locale model of
|
|
<emphasis>generic</emphasis> being selected.</para></listitem>
|
|
|
|
<listitem><para><userinput>--enable-languages=c,c++</userinput>: This option is
|
|
needed to ensure that both C and C++ compilers are built.</para></listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Compile the package:</para>
|
|
|
|
<screen><userinput>make</userinput></screen>
|
|
|
|
<para>There is no need to use the <userinput>bootstrap</userinput> target now,
|
|
as the compiler we're using to compile this GCC was built from the exact same
|
|
version of the GCC sources we used earlier.</para>
|
|
|
|
<note><para>It's worth pointing out that running the GCC test suite here
|
|
is considered not as important as running it in
|
|
<xref linkend="chapter06"/>.</para></note>
|
|
|
|
<para>Test the results:</para>
|
|
|
|
<screen><userinput>make -k check</userinput></screen>
|
|
|
|
<para>The <userinput>-k</userinput> flag is used to make the test suite run
|
|
through to completion and not stop at the first failure. The GCC test suite is
|
|
very comprehensive and is almost guaranteed to generate a few failures. To get
|
|
a summary of the test suite results, run this:</para>
|
|
|
|
<screen><userinput>../gcc-&gcc-version;/contrib/test_summary | more</userinput></screen>
|
|
|
|
<para>You can compare your results to those posted to the gcc-testresults
|
|
mailing list for similar configurations to your own. For an example of how
|
|
current GCC-&gcc-version; should look on i686-pc-linux-gnu, see
|
|
<ulink url="http://gcc.gnu.org/ml/gcc-testresults/2003-08/msg01612.html"/>.</para>
|
|
|
|
<para>Note that the results contain:</para>
|
|
|
|
<screen>* 1 XPASS (unexpected pass) for g++
|
|
* 1 FAIL (unexpected failure) for g++
|
|
* 2 FAIL for gcc
|
|
* 26 XPASS's for libstdc++</screen>
|
|
|
|
<para>The unexpected pass for g++ is due to the use of
|
|
<userinput>--enable-__cxa_atexit</userinput>. Apparently not all platforms
|
|
supported by GCC have support for "__cxa_atexit" in their C libraries, so this
|
|
test is not always expected to pass.</para>
|
|
|
|
<para>The 26 unexpected passes for libstdc++ are due to the use of
|
|
<userinput>--enable-clocale=gnu</userinput>, which is the correct choice on
|
|
Glibc-based systems of versions 2.2.5 and above. The underlying locale support
|
|
in the GNU C library is superior to that of the otherwise selected "generic"
|
|
model (which may be applicable if for instance you were using Newlibc, Sun-libc
|
|
or whatever libc). The libstdc++ test suite is apparently expecting the
|
|
"generic" model, hence those tests are not always expected to pass.</para>
|
|
|
|
<para>Unexpected failures often cannot be avoided. The GCC developers are
|
|
usually aware of them but haven't yet gotten around to fixing them. In short,
|
|
unless your results are vastly different from those at the above URL, it is safe
|
|
to continue on.</para>
|
|
|
|
<para>And finally install the package:</para>
|
|
|
|
<screen><userinput>make install</userinput></screen>
|
|
|
|
<note><para>At this point it is strongly recommended to repeat the sanity check
|
|
we performed earlier in the chapter. Refer back to
|
|
<xref linkend="ch05-locking-glibc"/> and repeat the check. If the results are
|
|
wrong, then most likely you forgot to apply the above mentioned GCC Specs
|
|
patch.</para></note>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|