6.18. GCC-14.2.0 - Pass 2

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

Approximate build time: 4.2 SBU
Required disk space: 5.5 GB

6.18.1. Installation of GCC

As in the first build of GCC, the GMP, MPFR, and MPC packages are required. Unpack the tarballs and move them into the required directories:

tar -xf ../mpfr-4.2.1.tar.xz
mv -v mpfr-4.2.1 mpfr
tar -xf ../gmp-6.3.0.tar.xz
mv -v gmp-6.3.0 gmp
tar -xf ../mpc-1.3.1.tar.gz
mv -v mpc-1.3.1 mpc

Change the default directory name for the libraries:

sed -e '/m64=/s/lib64/lib/' \
    -e '/m32=/s/m32=.*/m32=..\/lib32$(call if_multiarch,:i386-linux-gnu)/' \
    -i.orig gcc/config/i386/t-linux64

Override the building rule of libgcc and libstdc++ headers, to allow building these libraries with POSIX threads support:

sed '/thread_header =/s/@.*@/gthr-posix.h/' \
    -i libgcc/Makefile.in libstdc++-v3/include/Makefile.in

Create a separate build directory again:

mkdir -v build
cd       build

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

Now prepare GCC for compilation:

mlist=m64,m32,mx32
../configure                                       \
    --build=$(../config.guess)                     \
    --host=$LFS_TGT                                \
    --target=$LFS_TGT                              \
    LDFLAGS_FOR_TARGET=-L$PWD/$LFS_TGT/libgcc      \
    --prefix=/usr                                  \
    --with-build-sysroot=$LFS                      \
    --enable-default-pie                           \
    --enable-default-ssp                           \
    --disable-nls                                  \
    --enable-multilib --with-multilib-list=$mlist  \
    --disable-libatomic                            \
    --disable-libgomp                              \
    --disable-libquadmath                          \
    --disable-libsanitizer                         \
    --disable-libssp                               \
    --disable-libvtv                               \
    --enable-languages=c,c++

The meaning of the new configure options:

--with-build-sysroot=$LFS

Normally, using --host ensures that a cross-compiler is used for building GCC, and that compiler knows that it has to look for headers and libraries in $LFS. But the build system for GCC uses other tools, which are not aware of this location. This switch is needed so those tools will find the needed files in $LFS, and not on the host.

--target=$LFS_TGT

We are cross-compiling GCC, so it's impossible to build target libraries (libgcc and libstdc++) with the GCC binaries compiled in this pass—those binaries won't run on the host. The GCC build system will attempt to use the host's C and C++ compilers as a workaround by default. Building the GCC target libraries with a different version of GCC is not supported, so using the host's compilers may cause the build to fail. This parameter ensures the libraries are built by GCC pass 1.

LDFLAGS_FOR_TARGET=...

Allow libstdc++ to use the libgcc being built in this pass, instead of the previous version built in gcc-pass1. The previous version cannot properly support C++ exception handling because it was built without libc support.

--disable-libsanitizer

Disable GCC sanitizer runtime libraries. They are not needed for the temporary installation. In gcc-pass1 it was implied by --disable-libstdcxx, and now we can explicitly pass it.

Compile the package:

make

Install the package:

make DESTDIR=$LFS install

As a finishing touch, create a utility 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 -sv gcc $LFS/usr/bin/cc

Details on this package are located in Section 8.30.2, “Contents of GCC.”