Details on this package are located in Section 8.30.2, “Contents of GCC.”
The GCC package contains the GNU compiler collection, which includes the C and C++ compilers.
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$(call if_multiarch,:i386-linux-gnu)/' \
-i.orig gcc/config/i386/t-linux64
Make -mstackrealign a default for
32bit objects:
sed '/STACK_REALIGN_DEFAULT/s/0/(!TARGET_64BIT \&\& TARGET_SSE)/' \
-i gcc/config/i386/i386.h
Override the building rule of libgcc and libstdc++ headers, to allow building these libraries with POSIX threads support:
sed '/thread_header =/s/@.*@/gthr-posix.h/' \
-i libgcc/Makefile.in libstdc++-v3/include/Makefile.in
Create a separate build directory again:
mkdir -v build cd build
Before starting to build GCC, remember to unset any environment variables that override the default optimization flags.
Now prepare GCC for compilation:
mlist=m64,m32,mx32
../configure \
--build=$(../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.”