Details on this package are located in Section 10.18.2, “Contents of GCC.”
The GCC package contains the GNU compiler collection, which includes the C and C++ compilers.
Here we will compile GCC, as a cross-compiler that will create
executables for our target architecture, statically so that it will
not need to look for Glibc's startfiles, which do not yet exist in
/tools. We will use this
cross-compiler, plus the cross-linker we have just installed with
Binutils, to compile Glibc. After Glibc is installed into
/tools, we can rebuild GCC so that it
will then be able to build executables that link against the
libraries in /tools.
Make a couple of essential adjustments to GCC's specs to ensure GCC uses our build environment:
patch -Np1 -i ../gcc-7.1.0-specs-1.patch
Change the StartFile Spec so that GCC looks in /tools:
echo -en '\n#undef STANDARD_STARTFILE_PREFIX_1\n#define STANDARD_STARTFILE_PREFIX_1 "/tools/lib/"\n' >> gcc/config/linux.h echo -en '\n#undef STANDARD_STARTFILE_PREFIX_2\n#define STANDARD_STARTFILE_PREFIX_2 ""\n' >> gcc/config/linux.h
We will create a dummy limits.h so
the build will not use the one provided by the host distro:
touch /tools/include/limits.h
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:
AR=ar \
LDFLAGS="-Wl,-rpath,/cross-tools/lib" \
../gcc-7.1.0/configure \
--prefix=/cross-tools \
--build=${CLFS_HOST} \
--host=${CLFS_HOST} \
--target=${CLFS_TARGET} \
--with-sysroot=${CLFS} \
--with-local-prefix=/tools \
--with-native-system-header-dir=/tools/include \
--disable-shared \
--with-mpfr=/cross-tools \
--with-gmp=/cross-tools \
--with-isl=/cross-tools \
--with-mpc=/cross-tools \
--without-headers \
--with-newlib \
--disable-decimal-float \
--disable-libgomp \
--disable-libssp \
--disable-libatomic \
--disable-libitm \
--disable-libsanitizer \
--disable-libquadmath \
--disable-libvtv \
--disable-libcilkrts \
--disable-libstdc++-v3 \
--disable-threads \
--disable-multilib \
--enable-languages=c \
--with-glibc-version=2.25
The meaning of the new configure options:
--build=${CLFS_HOST}
This specifies the system on which the cross-compiler is being built.
--with-local-prefix=/tools
The purpose of this switch is to remove /usr/local/include from gcc's include search path.
This is not absolutely essential, however, it helps to
minimize the influence of the host system.
--with-native-system-headers-dir=/tools/include
This switch ensures that GCC will search for the system
headers in /tools/include and
that host system headers will not be searched.
--disable-shared
This tells GCC not to create a shared library.
--without-headers
Disables GCC from using the target's Libc when cross compiling.
--with-newlib
This causes GCC to enable the inhibit_libc flag, which prevents libgcc from building code that uses libc
support.
--disable-decimal-float
Disables support for the C decimal floating point extension.
--disable-lib*
These options prevent GCC from building a number of libraries that are not needed at this time.
--disable-threads
This will prevent GCC from looking for the multi-thread include files, since they haven't been created for this architecture yet. GCC will be able to find the multi-thread information after the Glibc headers are created.
--with-system-zlib
This tells GCC to link to the system-installed zlib instead of the one in its source tree.
--enable-languages=c
This option ensures that only the C compiler is built.
--with-glibc-version=2.25
Needed when bootstrapping a cross toolchain without the header files available for building the initial bootstrap compiler.
Continue with compiling the package:
make all-gcc all-target-libgcc
The meaning of the new make options:
all-gcc
all-target-libgcc
Compiles only the parts of GCC that are needed at this time, rather than the full package.
Install the package:
make install-gcc install-target-libgcc
Details on this package are located in Section 10.18.2, “Contents of GCC.”