6.17. GCC-4.6.1

6.17.1. Installation of GCC

Apply a sed substitution that will suppress the installation of libiberty.a. The version of libiberty.a provided by Binutils will be used instead:

sed -i 's/install_to_$(INSTALL_DEST) //' libiberty/Makefile.in

As in Section 5.10, “GCC-4.6.1 - 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

The fixincludes script is known to occasionally erroneously attempt to "fix" the system headers installed so far. As the headers up to this point are known to not require fixing, issue the following command to prevent the fixincludes script from running:

sed -i 's@\./fixinc\.sh@-c true@' gcc/Makefile.in

Finally, apply a patch that corrects the test code for locale changes that were made in glibc-2.14 and later.

patch -Np1 -i ../gcc-4.6.1-locale-1.patch

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:

../gcc-4.6.1/configure --prefix=/usr \
    --libexecdir=/usr/lib --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.

Compile the package:

make

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 16384

Test the results, but do not stop at errors:

make -k check

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

../gcc-4.6.1/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/7.0/ 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 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/4.6.1/../../../crt1.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.6.1/../../../crti.o succeeded
/usr/lib/gcc/i686-pc-linux-gnu/4.6.1/../../../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/local/include
 /usr/lib/gcc/i686-pc-linux-gnu/4.6.1/include
 /usr/lib/gcc/i686-pc-linux-gnu/4.6.1/include-fixed
 /usr/include

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

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 (allowing for platform-specific target triplets) 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