lfs-book-zh_CN/chapter05/glibc.xml

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<sect1 id="ch-tools-glibc" role="wrap">
  <?dbhtml filename="glibc.html"?>

  <sect1info condition="script">
    <productname>glibc</productname>
    <productnumber>&glibc-version;</productnumber>
    <address>&glibc-url;</address>
  </sect1info>

  <title>Glibc-&glibc-version;</title>

  <indexterm zone="ch-tools-glibc">
    <primary sortas="a-Glibc">Glibc</primary>
    <secondary>tools</secondary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
    href="../chapter06/glibc.xml"
    xpointer="xpointer(/sect1/sect2[1]/para[1])"/>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&glibc-ch5-sbu;</seg>
        <seg>&glibc-ch5-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

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

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

<screen><userinput remap="pre">mkdir -v ../glibc-build
cd ../glibc-build</userinput></screen>

    <para>Because Glibc no longer supports i386, its developers say to use the
    compiler flag <parameter>-march=i486</parameter> when building it for x86
    machines. There are several ways to accomplish that, but testing shows that
    the flag is best placed inside the build variable <quote>CFLAGS</quote>.
    Instead of overriding completely what Glibc's internal build system uses
    for CFLAGS, append the new flag to the existing contents of CFLAGS by
    making use of the special file <filename>configparms</filename>. The
    -mtune=native flag is also necessary to reset a reasonable value for -mtune
    that is changed when setting -march.</para>

<screen><userinput remap="configure">case `uname -m` in
  i?86) echo "CFLAGS += -march=i486 -mtune=native" &gt; configparms ;;
esac</userinput></screen>

    <para>Fix an issue when building Glibc-&glibc-version; with GCC-&gcc-version;:</para>

<screen><userinput remap="pre">sed -i 's/ -lgcc_s//' ../glibc-&glibc-version;/Makeconfig</userinput></screen>

    <para>Next, prepare Glibc for compilation:</para>

<screen><userinput remap="configure">../glibc-&glibc-version;/configure                             \
      --prefix=/tools                                 \
      --host=$LFS_TGT                                 \
      --build=$(../glibc-&glibc-version;/scripts/config.guess) \
      --disable-profile                               \
      --enable-add-ons                                \
      --enable-kernel=2.6.25                          \
      --with-headers=/tools/include                   \
      libc_cv_forced_unwind=yes                       \
      libc_cv_ctors_header=yes                        \
      libc_cv_c_cleanup=yes</userinput></screen>

    <variablelist>
      <title>The meaning of the configure options:</title>

      <varlistentry>
        <term><parameter>--host=$LFS_TGT, --build=$(../glibc-&glibc-version;/scripts/config.guess)</parameter></term>
        <listitem>
          <para>The combined effect of these switches is that Glibc's build system
          configures itself to cross-compile, using the cross-linker and
          cross-compiler in <filename class="directory">/tools</filename>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-profile</parameter></term>
        <listitem>
          <para>This builds the libraries without profiling information. Omit
          this option if profiling on the temporary tools is necessary.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--enable-add-ons</parameter></term>
        <listitem>
          <para>This tells Glibc to use the NPTL add-on as its threading
          library.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--enable-kernel=2.6.25</parameter></term>
        <listitem>
          <para>This tells Glibc to compile the library with support
          for 2.6.25 and later Linux kernels.  Workarounds for older
          kernels are not enabled.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-headers=/tools/include</parameter></term>
        <listitem>
          <para>This tells Glibc to compile itself against the headers recently
          installed to the tools directory, so that it knows exactly what
          features the kernel has and can optimize itself accordingly.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>libc_cv_forced_unwind=yes</parameter></term>
        <listitem>
          <para>The linker installed during
          <xref linkend="ch-tools-binutils-pass1"/> was cross-compiled and as
          such cannot be used until Glibc has been installed.  This means that
          the configure test for force-unwind support will fail, as it relies on
          a working linker.  The libc_cv_forced_unwind=yes variable is passed in
          order to inform <command>configure</command> that force-unwind
          support is available without it having to run the test.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><parameter>libc_cv_c_cleanup=yes</parameter></term>
        <listitem>
          <para>Simlarly, we pass libc_cv_c_cleanup=yes through to the
          <command>configure</command> script so that the test is skipped and C
          cleanup handling support is configured.</para>
        </listitem>
      </varlistentry>
      <varlistentry>
        <term><parameter>libc_cv_ctors_header=yes</parameter></term>
        <listitem>
          <para>Simlarly, we pass libc_cv_ctors_header=yes through to the
          <command>configure</command> script so that the test is skipped and
          gcc constructor support is configured.</para>
        </listitem>
      </varlistentry>

    </variablelist>

    <para>During this stage the following warning might appear:</para>

    <blockquote>
<screen><computeroutput>configure: WARNING:
*** These auxiliary programs are missing or
*** incompatible versions: msgfmt
*** some features will be disabled.
*** Check the INSTALL file for required versions.</computeroutput></screen>
    </blockquote>

    <para>The missing or incompatible <command>msgfmt</command> program is
    generally harmless. This <command>msgfmt</command> program is part of the
    Gettext package which the host distribution should provide.</para>

    <para>Compile the package:</para>

<screen><userinput remap="make">make</userinput></screen>

    <para>This package does come with a test suite, however, it cannot be
    run at this time because we do not have a C++ compiler yet.</para>

    <note>
      <para>The test suite also requires locale data to be installed in order to run
      successfully. Locale data provides information to the system regarding
      such things as the date, time, and currency formats accepted and output by
      system utilities. If the test suites are not being run in this chapter
      (as per the recommendation), there is no need to install the locales now.
      The appropriate locales will be installed in the next chapter. To install
      the Glibc locales anyway, use instructions from <xref
      linkend="ch-system-glibc" role="."/></para>
    </note>

    <para>Install the package:</para>

<screen><userinput remap="install">make install</userinput></screen>

  <caution>
    <para>At this point, it is imperative to stop and ensure that the basic
    functions (compiling and linking) of the new toolchain are working as
    expected. To perform a sanity check, run the following commands:</para>

<screen><userinput>echo 'main(){}' &gt; dummy.c
$LFS_TGT-gcc dummy.c
readelf -l a.out | grep ': /tools'</userinput></screen>

    <para>If everything is working correctly, there should be no errors,
    and the output of the last command will be of the form:</para>

<screen><computeroutput>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</computeroutput></screen>

    <para>Note that <filename class="directory">/tools/lib</filename>, or
    <filename class="directory">/tools/lib64</filename> for 64-bit machines
    appears as the prefix of the dynamic linker.</para>

    <para>If the output is not shown as above or there was no output at all,
    then something is wrong. Investigate and retrace the steps to find out
    where the problem is and correct it. This issue must be resolved before
    continuing on.</para>

    <para>Once all is well, clean up the test files:</para>

<screen><userinput>rm -v dummy.c a.out</userinput></screen>

  </caution>

  <note><para>Building Binutils in the next section will serve as an additional check that
  the toolchain has been built properly. If Binutils fails to build, it is an
  indication that something has gone wrong with the previous Binutils, GCC, or Glibc
  installations.</para></note>

  </sect2>

  <sect2 role="content">
    <title/>

    <para>Details on this package are located in
    <xref linkend="contents-glibc" role="."/></para>

  </sect2>

</sect1>