Linux From Scratch - Version 7.5-systemd

Chapter 6. Installing Basic System Software

6.17. GCC-4.8.2

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

Approximate build time: 55.6 SBU
Required disk space: 2.2 GB

6.17.1. Installation of GCC

As in Section 5.10, “GCC-4.8.2 - Pass 2”, apply the following sed to force the build to use the -fomit-frame-pointer compiler flag in order to ensure consistent compiler builds: 

case `uname -m` in
  i?86) sed -i 's/^T_CFLAGS =$/& -fomit-frame-pointer/' gcc/Makefile.in ;;
esac

Also fix an error in one of the check Makefiles and disable one test in the g++ libmudflap test suite: 

sed -i -e /autogen/d -e /check.sh/d fixincludes/Makefile.in 
mv -v libmudflap/testsuite/libmudflap.c++/pass41-frag.cxx{,.disable}

The GCC documentation recommends building GCC outside of the source directory in a dedicated build directory: 

mkdir -v ../gcc-build
cd ../gcc-build

Prepare GCC for compilation: 

SED=sed                          \
../gcc-4.8.2/configure           \
     --prefix=/usr               \
     --enable-shared             \
     --enable-threads=posix      \
     --enable-__cxa_atexit       \
     --enable-clocale=gnu        \
     --enable-languages=c,c++    \
     --disable-multilib          \
     --disable-bootstrap         \
     --with-system-zlib

Note that for other languages, there are some prerequisites that are not available. See the BLFS Book for instructions on how to build all the GCC supported languages.

The meaning of the new configure option:

SED=sed

Setting this environment variable prevents a hard-coded path to /tools/bin/sed.

--with-system-zlib

This switch tells GCC to link to the system installed copy of the Zlib library, rather than its own internal copy.

Compile the package: 

make
[Important]

Important

In this section, the test suite for GCC is considered critical. Do not skip it under any circumstance.

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

ulimit -s 32768

Test the results, but do not stop at errors: 

make -k check

To receive a summary of the test suite results, run: 

../gcc-4.8.2/contrib/test_summary

For only the summaries, pipe the output through grep -A7 Summ.

Results can be compared with those located at http://www.linuxfromscratch.org/lfs/build-logs/7.5-systemd/ and http://gcc.gnu.org/ml/gcc-testresults/.

A few unexpected failures cannot always be avoided. The GCC developers are usually aware of these issues, but have not resolved them yet. In particular, the libmudflap tests are known to be particularly problematic as a result of a bug in GCC (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20003). Unless the test results are vastly different from those at the above URL, it is safe to continue.

Install the package: 

make install

Some packages expect the C preprocessor to be installed in the /lib directory. To support those packages, create this symlink: 

ln -sv ../usr/bin/cpp /lib

Many packages use the name cc to call the C compiler. To satisfy those packages, create a symlink: 

ln -sv gcc /usr/bin/cc

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 the same sanity checks as we did earlier in the chapter: 

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

If everything is working correctly, there should be no errors, and the output of the last command will be (allowing for platform-specific differences in dynamic linker name): 

[Requesting program interpreter: /lib/ld-linux.so.2]

Now make sure that we're setup to use the correct startfiles: 

grep -o '/usr/lib.*/crt[1in].*succeeded' dummy.log

If everything is working correctly, there should be no errors, and the output of the last command will be: 

/usr/lib/gcc/i686-pc-linux-gnu/4.8.2/../../../crt1.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.8.2/../../../crti.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.8.2/../../../crtn.o succeeded

Depending on your machine architecture, the above may differ slightly, the difference usually being the name of the directory after /usr/lib/gcc. If your machine is a 64-bit system, you may also see a directory named lib64 towards the end of the string. The important thing to look for here is that gcc has found all three crt*.o files under the /usr/lib directory.

Verify that the compiler is searching for the correct header files: 

grep -B4 '^ /usr/include' dummy.log

This command should return successfully with the following output: 

#include <...> search starts here:
 /usr/lib/gcc/i686-pc-linux-gnu/4.8.2/include
 /usr/local/include
 /usr/lib/gcc/i686-pc-linux-gnu/4.8.2/include-fixed
 /usr/include

Again, note that the directory named after your target triplet may be different than the above, depending on your architecture.

[Note]

Note

As of version 4.3.0, GCC now unconditionally installs the limits.h file into the private include-fixed directory, and that directory is required to be in place.

Next, verify that the new linker is being used with the correct search paths: 

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

If everything is working correctly, there should be no errors, and the output of the last command will be: 

SEARCH_DIR("/usr/i686-pc-linux-gnu/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");

A 64-bit system may see a few more directories. For example, here is the output from an x86_64 machine: 

SEARCH_DIR("/usr/x86_64-unknown-linux-gnu/lib64")
SEARCH_DIR("/usr/local/lib64")
SEARCH_DIR("/lib64")
SEARCH_DIR("/usr/lib64")
SEARCH_DIR("/usr/x86_64-unknown-linux-gnu/lib")
SEARCH_DIR("/usr/local/lib")
SEARCH_DIR("/lib")
SEARCH_DIR("/usr/lib");

Next make sure that we're using the correct libc: 

grep "/lib.*/libc.so.6 " dummy.log

If everything is working correctly, there should be no errors, and the output of the last command (allowing for a lib64 directory on 64-bit hosts) will be: 

attempt to open /lib/libc.so.6 succeeded

Lastly, make sure GCC is using the correct dynamic linker: 

grep found dummy.log

If everything is working correctly, there should be no errors, and the output of the last command will be (allowing for platform-specific differences in dynamic linker name and a lib64 directory on 64-bit hosts): 

found ld-linux.so.2 at /lib/ld-linux.so.2

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 on with the process.

Once everything is working correctly, clean up the test files: 

rm -v dummy.c a.out dummy.log

Finally, move a misplaced file: 

mkdir -pv /usr/share/gdb/auto-load/usr/lib
mv -v /usr/lib/*gdb.py /usr/share/gdb/auto-load/usr/lib

6.17.2. Contents of GCC

Installed programs: c++, cc (link to gcc), cpp, g++, gcc, gcc-ar, gcc-nm, gcc-ranlib, and gcov
Installed libraries: libasan.{a,so}, libatomic.{a,so}, libgcc.a, libgcc_eh.a, libgcc_s.so, libgcov.a, libgomp.{a,so}, libiberty.a, libitm.{a,so}, liblto_plugin.so, libmudflap.{a,so}, libmudflapth.{a,so}, libquadmath.{a,so}, libssp.{a,so}, libssp_nonshared.a, libstdc++.{a,so}, libsupc++.a and libtsan.{a,so}
Installed directories: /usr/include/c++, /usr/lib/gcc, /usr/libexec/gcc, /usr/share/gcc-4.8.2

Short Descriptions

c++

The C++ compiler

cc

The C compiler

cpp

The C preprocessor; it is used by the compiler to expand the #include, #define, and similar statements in the source files

g++

The C++ compiler

gcc

The C compiler

gcc-ar

A wrapper around ar that adds a plugin to the command line. This program is only used to add "link time optization" and is not useful with the default build options.

gcc-nm

A wrapper around nm that adds a plugin to the command line. This program is only used to add "link time optization" and is not useful with the default build options.

gcc-ranlib

A wrapper around ranlib that adds a plugin to the command line. This program is only used to add "link time optization" and is not useful with the default build options.

gcov

A coverage testing tool; it is used to analyze programs to determine where optimizations will have the most effect

libasan

The Address Sanitizer runtime library

libgcc

Contains run-time support for gcc

libgcov

This library is linked in to a program when GCC is instructed to enable profiling

libgomp

GNU implementation of the OpenMP API for multi-platform shared-memory parallel programming in C/C++ and Fortran

libiberty

Contains routines used by various GNU programs, including getopt, obstack, strerror, strtol, and strtoul

liblto_plugin

GCC's Link Time Optimization (LTO) plugin allows GCC to perform optimizations across compilation units.

libmudflap

Contains routines that support GCC's bounds checking functionality

libquadmath

GCC Quad Precision Math Library API

libssp

Contains routines supporting GCC's stack-smashing protection functionality

libstdc++

The standard C++ library

libsupc++

Provides supporting routines for the C++ programming language

libtsan

The Thread Sanitizer runtime library