path: root/chapter08/gcc.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<!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;
]>

<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>If building on x86_64, change the default directory name for 64-bit
    libraries to <quote>lib</quote>:</para>

<screen><userinput remap="pre">case $(uname -m) in
  x86_64)
    sed -e '/m64=/s/lib64/lib/' \
        -i.orig gcc/config/i386/t-linux64
  ;;
esac</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      \
             --with-system-zlib</userinput></screen>

    <para>Note that for other programming languages there are some prerequisites that
    are not yet available. 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 installed
          by the binutils built earlier in this chapter, rather than
          the cross-built version which would otherwise be used.</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 executable) is a technique to produce
        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 the executable
        itself.  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,
        which would allow transferring control to some dangerous code
        (existing in the program or shared libraries, or injected by the
        attacker somehow) instead of the original one.
      </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 not skip it.  The time to run the tests can be
      reduced significantly by adding -jx to the make command below
      where x is the number of 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 -Rv tester .
su tester -c "PATH=$PATH make -k check"</userinput></screen>

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

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

    <para>For 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>In gcc, eleven tests, in the i386 test suite are known to FAIL.
    It's because the test files do not account for the
    <parameter>--enable-default-pie</parameter> option.</para>

    <para>In g++, four tests related to PR100400 are known to be reported
    as both XPASS and FAIL.  It's because the test file for this known issue
    is not well written.</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>

    <!--note><para>
      On some combinations of kernel configuration and AMD processors
      there may be more than 1100 failures in the gcc.target/i386/mpx
      tests (which are designed to test the MPX option on recent
      Intel processors). These can safely be ignored on AMD
      processors. These tests will also fail on Intel processors if MPX support
      is not enabled in the kernel even though it is present on the CPU.
    </para></note-->

    <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) will be incorrect.  Change the ownership to
    <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>
  <!-- already done earlier
    <para>Many packages use the name <command>cc</command> to call the C
    compiler. To satisfy those packages, create a symlink:</para>

<screen><userinput remap="install">ln -sv gcc /usr/bin/cc</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-linux-x86-64.so.2]</computeroutput></screen>

  <para>Now make sure that we're setup 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/x86_64-pc-linux-gnu/&gcc-version;/../../../../lib/Scrt1.o succeeded
/usr/lib/gcc/x86_64-pc-linux-gnu/&gcc-version;/../../../../lib/crti.o succeeded
/usr/lib/gcc/x86_64-pc-linux-gnu/&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/x86_64-pc-linux-gnu/&gcc-version;/include
 /usr/local/include
 /usr/lib/gcc/x86_64-pc-linux-gnu/&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/x86_64-pc-linux-gnu/lib64")
SEARCH_DIR("/usr/local/lib64")
SEARCH_DIR("/lib64")
SEARCH_DIR("/usr/lib64")
SEARCH_DIR("/usr/x86_64-pc-linux-gnu/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");</computeroutput></screen>

   <para>A 32-bit system may see a few different 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-linux-x86-64.so.2 at /usr/lib/ld-linux-x86-64.so.2</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 will need to 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}, libitm.{a,so},
        liblsan.{a,so}, liblto_plugin.so,
        libquadmath.{a,so}, libssp.{a,so}, libssp_nonshared.a,
        libstdc++.{a,so}, libstdc++fs.a, libsupc++.a, libtsan.{a,so},
        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 statements 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 most 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>The C preprocessing library</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 in to 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="libitm">
        <term><filename class="libraryfile">libitm</filename></term>
        <listitem>
          <para>The GNU transactional memory library</para>
          <indexterm zone="ch-system-gcc libitm">
            <primary sortas="c-libitm">libitm</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="liblsan">
        <term><filename class="libraryfile">liblsan</filename></term>
        <listitem>
          <para>The Leak Sanitizer runtime library</para>
          <indexterm zone="ch-system-gcc liblsan">
            <primary sortas="c-liblsan">liblsan</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's unused 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="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="libtsan">
        <term><filename class="libraryfile">libtsan</filename></term>
        <listitem>
          <para>The Thread Sanitizer runtime library</para>
          <indexterm zone="ch-system-gcc libtsan">
            <primary sortas="c-libtsan">libtsan</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>