5.10. GCC-4.6.1 - Pass 2

5.10.1. Installation of GCC

Versions of GCC later than 4.3 will treat this build as if it were a relocated compiler and disallow searching for startfiles in the location specified by --prefix. Since this will not be a relocated compiler, and the startfiles in /tools are crucial to building a working compiler linked to the libs in /tools, apply the following patch which partially reverts GCC to its old behavior:

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

Under normal circumstances the GCC fixincludes script is run in order to fix potentially broken header files. As GCC-4.6.1 and Glibc-2.14 have already been installed at this point, and their respective header files are known to not require fixing, the fixincludes script is not required. In fact, running this script may actually pollute the build environment by installing fixed headers from the host system into GCC's private include directory. The running of the fixincludes script can be suppressed by issuing the following commands:

cp -v gcc/Makefile.in{,.orig}
sed 's@\./fixinc\.sh@-c true@' gcc/Makefile.in.orig > gcc/Makefile.in

For x86 machines, a bootstrap build of GCC uses the -fomit-frame-pointer compiler flag. Non-bootstrap builds omit this flag by default, and the goal should be to produce a compiler that is exactly the same as if it were bootstrapped. Apply the following sed command to force the build to use the flag:

cp -v gcc/Makefile.in{,.tmp}
sed 's/^T_CFLAGS =$/& -fomit-frame-pointer/' gcc/Makefile.in.tmp \
  > gcc/Makefile.in

The following command will change the location of GCC's default dynamic linker to use the one installed in /tools. It also removes /usr/include from GCC's include search path. Doing this now rather than adjusting the specs file after installation ensures that the new dynamic linker is used during the actual build of GCC. That is, all of the binaries created during the build will link against the new Glibc. Issue:

for file in \
 $(find gcc/config -name linux64.h -o -name linux.h -o -name sysv4.h)
do
  cp -uv $file{,.orig}
  sed -e 's@/lib\(64\)\?\(32\)\?/ld@/tools&@g' \
  -e 's@/usr@/tools@g' $file.orig > $file
  echo '
#undef STANDARD_INCLUDE_DIR
#define STANDARD_INCLUDE_DIR 0
#define STANDARD_STARTFILE_PREFIX_1 ""
#define STANDARD_STARTFILE_PREFIX_2 ""' >> $file
  touch $file.orig
done

In case the above seems hard to follow, let's break it down a bit. First we find all the files under the gcc/config directory that are named either linux.h, linux64.h or sysv4.h. For each file found, we copy it to a file of the same name but with an added suffix of “.orig”. Then the first sed expression prepends “/tools” to every instance of “/lib/ld”, “/lib64/ld” or “/lib32/ld”, while the second one replaces hard-coded instances of “/usr”. Then we add our define statements which alter the include search path and the default startfile prefix to the end of the file. Finally, we use touch to update the timestamp on the copied files. When used in conjunction with cp -u, this prevents unexpected changes to the original files in case the commands are inadvertently run twice.

On x86_64, unsetting the multilib spec for GCC ensures that it won't attempt to link against libraries on the host:

case $(uname -m) in
  x86_64)
    for file in $(find gcc/config -name t-linux64) ; do \
      cp -v $file{,.orig}
      sed '/MULTILIB_OSDIRNAMES/d' $file.orig > $file
    done
  ;;
esac

As in the first build of GCC it requires the GMP, MPFR and MPC packages. Unpack the tarballs and move them into the required directory names:

tar -jxf ../mpfr-3.0.1.tar.bz2
mv -v mpfr-3.0.1 mpfr
tar -jxf ../gmp-5.0.2.tar.bz2
mv -v gmp-5.0.2 gmp
tar -zxf ../mpc-0.9.tar.gz
mv -v mpc-0.9 mpc

Create a separate build directory again:

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

Before starting to build GCC, remember to unset any environment variables that override the default optimization flags.

Now prepare GCC for compilation:

CC="$LFS_TGT-gcc -B/tools/lib/" \
    AR=$LFS_TGT-ar RANLIB=$LFS_TGT-ranlib \
    ../gcc-4.6.1/configure --prefix=/tools \
    --with-local-prefix=/tools --enable-clocale=gnu \
    --enable-shared --enable-threads=posix \
    --enable-__cxa_atexit --enable-languages=c,c++ \
    --disable-libstdcxx-pch --disable-multilib \
    --disable-bootstrap --disable-libgomp \
    --without-ppl --without-cloog

Compile the package:

make

Install the package:

make install

As a finishing touch, create a symlink. Many programs and scripts run cc instead of gcc, which is used to keep programs generic and therefore usable on all kinds of UNIX systems where the GNU C compiler is not always installed. Running cc leaves the system administrator free to decide which C compiler to install:

ln -vs gcc /tools/bin/cc