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<!ENTITY % general-entities SYSTEM "../general.ent">
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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>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 \
--disable-fixinclude \
--with-system-zlib</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>--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 -Rv 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>Eleven tests in the i386 test suite for the gcc compiler are known to FAIL.
It's because the test files do not account for the
<parameter>--enable-default-pie</parameter> option.</para>
<!--
<para>Four tests related to PR100400 may be reported
as both XPASS and FAIL when testing the g++ compiler; the test file
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) 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/$(gcc -dumpmachine)/&gcc-version;/include{,-fixed}</userinput></screen>
<para>Create a symlink required by the <ulink
url="https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch03s09.html">FHS</ulink>
for "historical" reasons.</para>
<screen><userinput remap="install">ln -svr /usr/bin/cpp /usr/lib</userinput></screen>
<!-- already done earlier
<para>Many packages use the name <command>cc</command> to call the C
compiler. To satisfy those packages, create a symlink:</para>
<screen><userinput remap="install">ln -sv gcc /usr/bin/cc</userinput></screen>
-->
<para>Add a compatibility symlink to enable building programs with
Link Time Optimization (LTO):</para>
<screen><userinput remap="install">ln -sfv ../../libexec/gcc/$(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(){}' > dummy.c
cc dummy.c -v -Wl,--verbose &> 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 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/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 <...> 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 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-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 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}, 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 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>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 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="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 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="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>