source: chapter08/gcc.xml@ 3d891c7

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
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<sect1 id="ch-system-gcc" role="wrap">
  <?dbhtml filename="gcc.html"?>

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

  <title>GCC-&gcc-version;</title>

  <indexterm zone="ch-system-gcc">
    <primary sortas="a-GCC">GCC</primary>
  </indexterm>

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

    <para>The GCC package contains the GNU compiler collection, which includes
    the C and C++ compilers.</para>

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

      <seglistitem>
        <seg>&gcc-fin-sbu;</seg>
        <seg>&gcc-fin-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

  <sect2 role="installation">
    <title>Installation of GCC</title>
<!--
    <para>At first, fix an issue breaking
    <filename class="libraryfile">libasan.a</filename> building this package
    with Glibc-2.34 or later:</para>

<screen><userinput remap="pre">sed -e '/static.*SIGSTKSZ/d' \
    -e 's/return kAltStackSize/return SIGSTKSZ * 4/' \
    -i libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp</userinput></screen>
-->
<!--
    <para>First fix a problem with the latest version of glibc:</para>

    <screen><userinput remap="pre">patch -Np1 -i ../&gcc-upstream-fixes-patch;</userinput></screen>
-->
    <para>For building on 64-bit MIPS, change the default directory name for
    64-bit libraries to <quote>lib</quote>:</para>

<screen><userinput remap="pre">sed -e 's/lib64/lib/' \
    -i.orig gcc/config/mips/{mips.h,t-linux64}</userinput></screen>

    <para>The GCC documentation recommends building GCC in a dedicated build directory:</para>

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

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

<screen><userinput remap="configure">../configure --prefix=/usr            \
             LD=ld                    \
             --enable-languages=c,c++ \
             --enable-default-pie     \
             --enable-default-ssp     \
             --disable-multilib       \
             --disable-bootstrap      \
             --disable-fixincludes    \
             --with-arch=mips64r2     \
             --with-system-zlib       \
             $(cc -v 2>&amp;1 | grep -o .-with-nan=2008)</userinput></screen>

    <para>GCC supports seven different computer languages, but the
    prerequisites for most of them have not yet been installed. See the
    <ulink url="&blfs-book;general/gcc.html">BLFS Book GCC page</ulink>
    for instructions on how to build all of GCC's supported languages.</para>

    <variablelist>
      <title>The meaning of the new configure parameters:</title>

      <varlistentry>
        <term><parameter>LD=ld</parameter></term>
        <listitem>
          <para>This parameter makes the configure script use the ld program installed
          by the Binutils package built earlier in this chapter, rather than
          the cross-built version which would otherwise be used.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--disable-fixincludes</parameter></term>
        <listitem>
          <para>By default, during the installation of GCC some system
          headers would be <quote>fixed</quote> to be used with GCC.  This
          is not necessary for a modern Linux system, and potentially 
          harmful if a package is reinstalled after installing GCC.  This
          switch prevents GCC from <quote>fixing</quote> the headers.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>--with-system-zlib</parameter></term>
        <listitem>
          <para>This switch tells GCC to link to the system installed copy of
          the Zlib library, rather than its own internal copy.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <note>
      <anchor id="pie-ssp-info" xreflabel="note on PIE and SSP"/>
      <para>
        PIE (position-independent executables) are
        binary programs that can be loaded anywhere in memory.  Without PIE,
        the security feature named ASLR (Address Space Layout Randomization)
        can be applied for the shared libraries, but not for the executables
        themselves.  Enabling PIE allows ASLR for the executables in addition to
        the shared libraries, and mitigates some attacks based on fixed
        addresses of sensitive code or data in the executables.
      </para>
      <para>
        SSP (Stack Smashing Protection) is a technique to ensure
        that the parameter stack is not corrupted. Stack corruption can,
        for example, alter the return address of a subroutine,
        thus transferring control to some dangerous code
        (existing in the program or shared libraries, or injected by the
        attacker somehow).
      </para>
    </note>

    <para>Compile the package:</para>

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

    <important>
      <para>In this section, the test suite for GCC is considered
      important, but it takes a long time. First-time builders are
      encouraged to run the test suite.  The time to run the tests can be
      reduced significantly by adding -jx to the <command>make -k check</command> command below,
      where x is the number of CPU cores on your system.</para>
    </important>

   <para>One set of tests in the GCC test suite is known to exhaust the default
   stack, so increase the stack size prior to running the tests:</para>

<screen><userinput remap="test">ulimit -s 32768</userinput></screen>

    <para>Test the results as a non-privileged user, but do not stop at errors:</para>

<screen><userinput remap="test">chown -R tester .
su tester -c "PATH=$PATH make -k check"</userinput></screen>

    <para>To extract a summary of the test suite results, run:</para>

<screen><userinput remap="test">../contrib/test_summary</userinput></screen>

    <para>To filter out only the summaries, pipe the output through
    <userinput>grep -A7 Summ</userinput>.</para>

    <para>Results can be compared with those located at <ulink
    url="&test-results;"/> and
    <ulink url="https://gcc.gnu.org/ml/gcc-testresults/"/>.</para>

    <para>
    Eight gcc tests (out of over 185,000):
    <!-- https://gcc.gnu.org/PR106375 --><filename>pr56837.c</filename>
    and seven tests in the <filename class='directory'>analyzer</filename>
    directory are known to fail.

    <!-- https://gcc.gnu.org/PR109353 -->
    One libstdc++ test (out of over 15000), <filename>copy.cc</filename>, is
    known to fail.

    For g++, 21 tests (out of approximately 250,000): 14
    <quote>AddressSanitizer*</quote>
    tests and 7 <filename>interception-malloc-test-1.C</filename> tests, are
    known to fail.

    Additionally, several tests in the
    <filename class='directory'>vect</filename> directory are known to fail
    if the hardware does not support AVX.</para>

    <para>Hundreds of gcc and g++ tests can fail on MIPS systems, as MIPS
    is not a primary platform of GCC and many MIPS tests are not written
    with <option>--enable-default-pie</option> or
    <option>--enable-default-ssp</option> in mind.</para>

    <para>In libstdc++ tests, the tests named
    <filename>abi_check</filename> and
    <filename>compare_exchange_padding.cc</filename> are known to fail.</para>

    <para>A few unexpected failures cannot always be avoided. The GCC developers
    are usually aware of these issues, but have not resolved them yet.
    Unless the test results are vastly different from those at the above URL,
    it is safe to continue.</para>

    <para>Install the package:</para>

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

    <para>The GCC build directory is owned by <systemitem class="username">
    tester</systemitem> now, and the ownership of the installed header
    directory (and its content) is incorrect.  Change the ownership to the
    <systemitem class="username">root</systemitem> user and group:</para>

<screen><userinput remap="install">chown -v -R root:root \
    /usr/lib/gcc/$(gcc -dumpmachine)/&gcc-version;/include{,-fixed}</userinput></screen>

    <para>Create a symlink required by the <ulink
    url="https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch03s09.html">FHS</ulink>
    for "historical" reasons.</para>

<screen><userinput remap="install">ln -svr /usr/bin/cpp /usr/lib</userinput></screen>

    <para>Many packages use the name <command>cc</command> to call the C
    compiler.  We've already created <command>cc</command> as a symlink in
    <xref linkend='ch-tools-gcc-pass2'/>, create its man page as a symlink
    as well:</para>

<screen><userinput remap="install">ln -sv gcc.1 /usr/share/man/man1/cc.1</userinput></screen>

    <para>Add a compatibility symlink to enable building programs with
    Link Time Optimization (LTO):</para>

<screen><userinput remap="install">ln -sfv ../../libexec/gcc/$(gcc -dumpmachine)/&gcc-version;/liblto_plugin.so \
        /usr/lib/bfd-plugins/</userinput></screen>

    <para>Now that our final toolchain is in place, it is important to again ensure
    that compiling and linking will work as expected. We do this by performing
    some sanity checks:</para>

<screen><userinput>echo 'int main(){}' &gt; dummy.c
cc dummy.c -v -Wl,--verbose &amp;&gt; dummy.log
readelf -l a.out | grep ': /lib'</userinput></screen>

  <para>There should be no errors,
  and the output of the last command will be (allowing for
  platform-specific differences in the dynamic linker name):</para>

<screen><computeroutput>[Requesting program interpreter: /lib64/ld.so.1]</computeroutput></screen>

  <para>Now make sure that we're set up to use the correct start files:</para>

<screen><userinput>grep -E -o '/usr/lib.*/S?crt[1in].*succeeded' dummy.log</userinput></screen>

  <para>The output of the last command should be:</para>

<screen><computeroutput>/usr/lib/gcc/mips64el-unknown-linux-gnuabi64/&gcc-version;/../../../../lib/Scrt1.o succeeded
/usr/lib/gcc/mips64el-unknown-linux-gnuabi64/&gcc-version;/../../../../lib/crti.o succeeded
/usr/lib/gcc/mips64el-unknown-linux-gnuabi64/&gcc-version;/../../../../lib/crtn.o succeeded</computeroutput></screen>

  <para>Depending on your machine architecture, the above may differ slightly.
  The difference will be the name of the directory
  after <filename class="directory">/usr/lib/gcc</filename>. The important
  thing to look for here is that <command>gcc</command> has found all three
  <filename>crt*.o</filename> files under the
  <filename class="directory">/usr/lib</filename> directory.</para>

  <para>Verify that the compiler is searching for the correct header
  files:</para>

<screen><userinput>grep -B4 '^ /usr/include' dummy.log</userinput></screen>

  <para>This command should return the following output:</para>

<screen><computeroutput>#include &lt;...&gt; search starts here:
 /usr/lib/gcc/mips64el-unknown-linux-gnuabi64/&gcc-version;/include
 /usr/local/include
 /usr/lib/gcc/mips64el-unknown-linux-gnuabi64/&gcc-version;/include-fixed
 /usr/include</computeroutput></screen>

   <para>Again, the directory named after your target triplet may be
   different than the above, depending on your system architecture.</para>

  <para>Next, verify that the new linker is being used with the correct search paths:</para>

<screen><userinput>grep 'SEARCH.*/usr/lib' dummy.log |sed 's|; |\n|g'</userinput></screen>

  <para>References to paths that have components with '-linux-gnu' should
  be ignored, but otherwise the output of the last command should be:</para>

<screen><computeroutput>SEARCH_DIR("/usr/mips64el-unknown-linux-gnuabi64/lib64")
SEARCH_DIR("/usr/local/lib64")
SEARCH_DIR("/lib64")
SEARCH_DIR("/usr/lib64")
SEARCH_DIR("/usr/mips64el-unknown-linux-gnuabi64/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");</computeroutput></screen>
<!--
   <para>A 32-bit system may use a few other directories. For example, here
   is the output from an i686 machine:</para>

<screen><computeroutput>SEARCH_DIR("/usr/i686-pc-linux-gnu/lib32")
SEARCH_DIR("/usr/local/lib32")
SEARCH_DIR("/lib32")
SEARCH_DIR("/usr/lib32")
SEARCH_DIR("/usr/i686-pc-linux-gnu/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");</computeroutput></screen>
-->
  <para>Next make sure that we're using the correct libc:</para>

<screen><userinput>grep "/lib.*/libc.so.6 " dummy.log</userinput></screen>

  <para>The output of the last command should be:</para>

<screen><computeroutput>attempt to open /usr/lib/libc.so.6 succeeded</computeroutput></screen>

  <para>Make sure GCC is using the correct dynamic linker:</para>

<screen><userinput>grep found dummy.log</userinput></screen>

  <para>The output of the last command should be (allowing for
  platform-specific differences in dynamic linker name):</para>

<screen><computeroutput>found ld.so.1 at /usr/lib/ld.so.1</computeroutput></screen>

  <para>If the output does not appear as shown above or is not received
  at all, then something is seriously wrong. Investigate and retrace the
  steps to find out where the problem is and correct it. <!--The most likely
  reason is that something went wrong with the specs file adjustment.--> Any
  issues should be resolved before continuing with the process.</para>

  <para>Once everything is working correctly, clean up the test files:</para>

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

    <para>Finally, move a misplaced file:</para>

<screen><userinput remap="install">mkdir -pv /usr/share/gdb/auto-load/usr/lib
mv -v /usr/lib/*gdb.py /usr/share/gdb/auto-load/usr/lib</userinput></screen>

  </sect2>

  <sect2 id="contents-gcc" role="content">
    <title>Contents of GCC</title>

    <segmentedlist>
      <segtitle>Installed programs</segtitle>
      <segtitle>Installed libraries</segtitle>
      <segtitle>Installed directories</segtitle>

      <seglistitem>
        <seg>c++, cc (link to gcc), cpp, g++, gcc,
        gcc-ar, gcc-nm, gcc-ranlib, gcov, gcov-dump, gcov-tool,
        and lto-dump</seg>

        <seg>libasan.{a,so}, libatomic.{a,so}, libcc1.so, libgcc.a, libgcc_eh.a,
        libgcc_s.so, libgcov.a, libgomp.{a,so},
        liblto_plugin.so,
        libquadmath.{a,so}, libssp.{a,so}, libssp_nonshared.a,
        libstdc++.{a,so}, libstdc++exp.a, libstdc++fs.a, libsupc++.a,
        and libubsan.{a,so}</seg>

        <seg>/usr/include/c++, /usr/lib/gcc, /usr/libexec/gcc, and
        /usr/share/gcc-&gcc-version;</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="c">
        <term><command>c++</command></term>
        <listitem>
          <para>The C++ compiler</para>
          <indexterm zone="ch-system-gcc c">
            <primary sortas="b-c++">c++</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="cc">
        <term><command>cc</command></term>
        <listitem>
          <para>The C compiler</para>
          <indexterm zone="ch-system-gcc cc">
            <primary sortas="b-cc">cc</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="cpp">
        <term><command>cpp</command></term>
        <listitem>
          <para>The C preprocessor; it is used by the compiler to expand the
          #include, #define, and similar directives in the source files</para>
          <indexterm zone="ch-system-gcc cpp">
            <primary sortas="b-cpp">cpp</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="g">
        <term><command>g++</command></term>
        <listitem>
          <para>The C++ compiler</para>
          <indexterm zone="ch-system-gcc g">
            <primary sortas="b-g++">g++</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcc">
        <term><command>gcc</command></term>
        <listitem>
          <para>The C compiler</para>
          <indexterm zone="ch-system-gcc gcc">
            <primary sortas="b-gcc">gcc</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcc-ar">
        <term><command>gcc-ar</command></term>
        <listitem>
          <para>A wrapper around <command>ar</command> that adds a
          plugin to the command line. This program is only used
          to add "link time optimization" and is not useful with the
          default build options.</para>
          <indexterm zone="ch-system-gcc gcc-ar">
            <primary sortas="b-gcc-ar">gc-ar</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcc-nm">
        <term><command>gcc-nm</command></term>
        <listitem>
          <para>A wrapper around <command>nm</command> that adds a
          plugin to the command line. This program is only used
          to add "link time optimization" and is not useful with the
          default build options.</para>
          <indexterm zone="ch-system-gcc gcc-nm">
            <primary sortas="b-gcc-nm">gc-nm</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcc-ranlib">
        <term><command>gcc-ranlib</command></term>
        <listitem>
          <para>A wrapper around <command>ranlib</command> that adds a
          plugin to the command line. This program is only used
          to add "link time optimization" and is not useful with the
          default build options.</para>
          <indexterm zone="ch-system-gcc gcc-ranlib">
            <primary sortas="b-gcc-ranlib">gc-ranlib</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcov">
        <term><command>gcov</command></term>
        <listitem>
          <para>A coverage testing tool; it is used to analyze programs to
          determine where optimizations will have the greatest effect</para>
          <indexterm zone="ch-system-gcc gcov">
            <primary sortas="b-gcov">gcov</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcov-dump">
        <term><command>gcov-dump</command></term>
        <listitem>
          <para>Offline gcda and gcno profile dump tool</para>
          <indexterm zone="ch-system-gcc gcov-dump">
            <primary sortas="b-gcov-dump">gcov-dump</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="gcov-tool">
        <term><command>gcov-tool</command></term>
        <listitem>
          <para>Offline gcda profile processing tool</para>
          <indexterm zone="ch-system-gcc gcov-tool">
            <primary sortas="b-gcov-tool">gcov-tool</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="lto-dump">
        <term><command>lto-dump</command></term>
        <listitem>
          <para>Tool for dumping object files produced by GCC with LTO
          enabled</para>
          <indexterm zone="ch-system-gcc lto-dump">
            <primary sortas="b-lto-dump">lto-dump</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libasan">
        <term><filename class="libraryfile">libasan</filename></term>
        <listitem>
          <para>The Address Sanitizer runtime library</para>
          <indexterm zone="ch-system-gcc libasan">
            <primary sortas="b-libasan">libasan</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libatomic">
        <term><filename class="libraryfile">libatomic</filename></term>
        <listitem>
          <para>GCC atomic built-in runtime library</para>
          <indexterm zone="ch-system-gcc libatomic">
            <primary sortas="b-libatomic">libatomic</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libcc1">
        <term><filename class="libraryfile">libcc1</filename></term>
        <listitem>
          <para>A library that allows GDB to make use of GCC</para>
          <indexterm zone="ch-system-gcc libcc1">
            <primary sortas="b-libcc1">libcc1</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libgcc">
        <term><filename class="libraryfile">libgcc</filename></term>
        <listitem>
          <para>Contains run-time support for <command>gcc</command></para>
          <indexterm zone="ch-system-gcc libgcc">
            <primary sortas="c-libgcc">libgcc</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libgcov">
        <term><filename class="libraryfile">libgcov</filename></term>
        <listitem>
          <para>This library is linked into a program when GCC is instructed
          to enable profiling</para>
          <indexterm zone="ch-system-gcc libgcov">
            <primary sortas="c-libgcov">libgcov</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libgomp">
        <term><filename class="libraryfile">libgomp</filename></term>
        <listitem>
          <para>GNU implementation of the OpenMP API for multi-platform
          shared-memory parallel programming in C/C++ and Fortran</para>
          <indexterm zone="ch-system-gcc libgomp">
            <primary sortas="c-libgomp">libgomp</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="liblto_plugin">
        <term><filename class="libraryfile">liblto_plugin</filename></term>
        <listitem>
          <para>GCC's LTO plugin allows Binutils to process object files
          produced by GCC with LTO enabled</para>
          <indexterm zone="ch-system-gcc liblto_plugin">
            <primary sortas="c-liblto_plugin">liblto_plugin</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libquadmath">
        <term><filename class="libraryfile">libquadmath</filename></term>
        <listitem>
          <para>GCC Quad Precision Math Library API</para>
          <indexterm zone="ch-system-gcc libquadmath">
            <primary sortas="c-libquadmath">libquadmath</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libssp">
        <term><filename class="libraryfile">libssp</filename></term>
        <listitem>
          <para>Contains routines supporting GCC's stack-smashing protection
          functionality.  Normally it is not used, because Glibc also provides
          those routines.</para>
          <indexterm zone="ch-system-gcc libssp">
            <primary sortas="c-libssp">libssp</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libstdc">
        <term><filename class="libraryfile">libstdc++</filename></term>
        <listitem>
          <para>The standard C++ library</para>
          <indexterm zone="ch-system-gcc libstdc">
            <primary sortas="c-libstdc++">libstdc++</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libstdcexp">
        <term><filename class="libraryfile">libstdc++exp</filename></term>
        <listitem>
          <para>Experimental C++ Contracts library</para>
          <indexterm zone="ch-system-gcc libstdcexp">
            <primary sortas="c-libstdc++exp">libstdc++exp</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libstdcfs">
        <term><filename class="libraryfile">libstdc++fs</filename></term>
        <listitem>
          <para>ISO/IEC TS 18822:2015 Filesystem library</para>
          <indexterm zone="ch-system-gcc libstdcfs">
            <primary sortas="c-libstdc++fs">libstdc++fs</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libsupc">
        <term><filename class="libraryfile">libsupc++</filename></term>
        <listitem>
          <para>Provides supporting routines for the C++ programming
          language</para>
          <indexterm zone="ch-system-gcc libsupc">
            <primary sortas="c-libsupc++">libsupc++</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libubsan">
        <term><filename class="libraryfile">libubsan</filename></term>
        <listitem>
          <para>The Undefined Behavior Sanitizer runtime library</para>
          <indexterm zone="ch-system-gcc libubsan">
            <primary sortas="c-libubsan">libubsan</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>