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9310805aff
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@6028 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
210 lines
8.5 KiB
XML
210 lines
8.5 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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<!ENTITY % patches-entities SYSTEM "../patches.ent">
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%general-entities;
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%patches-entities;
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]>
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<sect1 id="ch-tools-gcc-pass2" role="wrap">
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<title>GCC-&gcc-version; - Pass 2</title>
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<?dbhtml filename="gcc-pass2.html"?>
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<indexterm zone="ch-tools-gcc-pass2">
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<primary sortas="a-GCC">GCC</primary>
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<secondary>tools, pass 2</secondary></indexterm>
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<sect2 role="package"><title/>
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<segmentedlist>
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<segtitle>&buildtime;</segtitle>
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<segtitle>&diskspace;</segtitle>
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<seglistitem><seg>11.0 SBU</seg><seg>292 MB</seg></seglistitem>
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</segmentedlist>
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<xi:include xmlns:xi="http://www.w3.org/2003/XInclude" href="../chapter06/gcc.xml" xpointer="xpointer(/sect1/sect2[1]/segmentedlist[2])"/>
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</sect2>
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<sect2 role="installation">
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<title>Re-installation of GCC</title>
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<para>This package is known to have issues when its default
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optimization flags (including the <parameter>-march</parameter> and
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<parameter>-mcpu</parameter> options) are changed. If any environment
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variables that override default optimizations have been defined, such
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as <envar>CFLAGS</envar> and <envar>CXXFLAGS</envar>,
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unset them when building GCC.</para>
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<para>The tools required to test GCC and Binutils—Tcl, Expect
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and DejaGNU—are installed now. GCC and Binutils can now be
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rebuilt, linking them against the new Glibc and testing them properly
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(if running the test suites in this chapter). Please note that these
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test suites are highly dependent on properly functioning PTYs which
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are provided by the host. PTYs are most commonly implemented via the
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<systemitem class="filesystem">devpts</systemitem> file system. Check
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to see if the host system is set up correctly in this regard by
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performing a quick test:</para>
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<screen><userinput>expect -c "spawn ls"</userinput></screen>
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<para>The response might be:</para>
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<screen><computeroutput>The system has no more ptys.
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Ask your system administrator to create more.</computeroutput></screen>
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<para>If the above message is received, the host does not have its
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PTYs set up properly. In this case, there is no point in running the
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test suites for GCC and Binutils until this issue is resolved. Please
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consult the LFS Wiki at <ulink url="&wiki-root;"/> for more
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information on how to get PTYs working.</para>
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<para>First correct a known problem and make an essential adjustment:</para>
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<screen><userinput>patch -Np1 -i ../&gcc-no_fixincludes-patch;
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patch -Np1 -i ../&gcc-specs-patch;</userinput></screen>
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<para>The first patch disables the GCC <command>fixincludes</command>
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script. This was briefly mentioned earlier, but a more in-depth
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explanation of the fixincludes process is warranted here. Under normal
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circumstances, the GCC <command>fixincludes</command> script scans the
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system for header files that need to be fixed. It might find that some
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Glibc header files on the host system need to be fixed, and will fix
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them and put them in the GCC private include directory. In <xref
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linkend="chapter-building-system"/>, after the newer Glibc has been
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installed, this private include directory will be searched before the
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system include directory. This may result in GCC finding the fixed
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headers from the host system, which most likely will not match the
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Glibc version used for the LFS system.</para>
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<para>The second patch changes GCC's default location of the dynamic
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linker (typically <filename class="libraryfile">ld-linux.so.2</filename>). It also removes
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<filename class="directory">/usr/include</filename> from GCC's include
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search path. Patching now rather than adjusting the specs file after
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installation ensures that the new dynamic linker is used during the
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actual build of GCC. That is, all of the final (and temporary)
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binaries created during the build will link against the new
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Glibc.</para>
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<important><para>The above patches are critical in ensuring a
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successful overall build. Do not forget to apply
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them.</para></important>
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<para>Create a separate build directory again:</para>
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<screen><userinput>mkdir ../gcc-build
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cd ../gcc-build</userinput></screen>
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<para>Before starting to build GCC, remember to unset any environment
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variables that override the default optimization flags.</para>
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<para>Now prepare GCC for compilation:</para>
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<screen><userinput>../gcc-&gcc-version;/configure --prefix=/tools \
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--libexecdir=/tools/lib --with-local-prefix=/tools \
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--enable-clocale=gnu --enable-shared \
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--enable-threads=posix --enable-__cxa_atexit \
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--enable-languages=c,c++ --disable-libstdcxx-pch</userinput></screen>
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<para>The meaning of the new configure options:</para>
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<variablelist>
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<varlistentry>
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<term><parameter>--enable-clocale=gnu</parameter></term>
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<listitem><para>This option ensures the correct locale model is
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selected for the C++ libraries under all circumstances. If the
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configure script finds the <emphasis>de_DE</emphasis> locale installed, it will select the
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correct gnu locale model. However, if the <emphasis>de_DE</emphasis> locale is not
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installed, there is the risk of building Application Binary Interface
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(ABI)-incompatible C++ libraries because the incorrect generic locale
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model may be selected.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>--enable-threads=posix</parameter></term>
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<listitem><para>This enables C++ exception handling for multi-threaded
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code.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>--enable-__cxa_atexit</parameter></term>
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<listitem><para>This option allows use of
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<emphasis>__cxa_atexit</emphasis>, rather than
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<emphasis>atexit</emphasis>, to register C++ destructors for local
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statics and global objects. This option is essential for fully
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standards-compliant handling of destructors. It also affects the C++
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ABI, and therefore results in C++ shared libraries and C++ programs
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that are interoperable with other Linux
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distributions.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>--enable-languages=c,c++</parameter></term>
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<listitem><para>This option
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ensures that both the C and C++ compilers are built.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>--disable-libstdcxx-pch</parameter></term>
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<listitem><para>Do not build the pre-compiled header (PCH) for
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<filename class="libraryfile">libstdc++</filename>. It takes up a lot of space,
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and we have no use for it.</para></listitem>
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</varlistentry>
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</variablelist>
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<para>Compile the package:</para>
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<screen><userinput>make</userinput></screen>
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<para>There is no need to use the <parameter>bootstrap</parameter>
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target now because the compiler being used to compile this GCC was
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built from the exact same version of the GCC sources used
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earlier.</para>
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<para>Compilation is now complete. As previously mentioned, running
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the test suites for the temporary tools compiled in this chapter is
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not mandatory. To run the GCC test suite anyway, use the following
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command:</para>
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<screen><userinput>make -k check</userinput></screen>
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<para>The <parameter>-k</parameter> flag is used to make the test suite run
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through to completion and not stop at the first failure. The GCC test
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suite is very comprehensive and is almost guaranteed to generate a few
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failures. To receive a summary of the test suite results, run:</para>
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<screen><userinput>../gcc-&gcc-version;/contrib/test_summary</userinput></screen>
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<para>For only the summaries, pipe the output through
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<userinput>grep -A7 Summ</userinput>.</para>
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<para>Results can be compared to those posted to the gcc-testresults
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mailing list to see similar configurations to the one being built. For
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an example of how current GCC-&gcc-version; should look on
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i686-pc-linux-gnu, see <ulink
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url="http://gcc.gnu.org/ml/gcc-testresults/2004-07/msg00179.html"/>.</para>
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<para>A few unexpected failures cannot always be avoided. The
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GCC developers are usually aware of these issues, but have not
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resolved them yet. Unless the test results are vastly different from
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those at the above URL, it is safe to continue.</para>
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<para>Install the package:</para>
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<screen><userinput>make install</userinput></screen>
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<note><para>At this point it is strongly recommended to repeat the
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sanity check we performed earlier in this chapter. Refer back to <xref
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linkend="ch-tools-adjusting" role=","/> and repeat the test compilation. If
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the result is wrong, the most likely reason is that the GCC Specs
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patch was not properly applied.</para></note>
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</sect2>
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<sect2 role="content"><title/>
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<para>Details on this package are located in <xref
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linkend="contents-gcc" role="."/></para>
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</sect2>
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</sect1>
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