Details on this package are located in Section 8.29.2, “Contents of GCC.”
The GCC package contains the GNU compiler collection, which includes the C and C++ compilers.
Approximate build time:
3.2 SBU
Required disk space:
4.9 GB
5.3.1. Installation of Cross GCC
GCC requires the GMP, MPFR and MPC packages. As these packages may not be included in your host distribution, they will be built with GCC. Unpack each package into the GCC source directory and rename the resulting directories so the GCC build procedures will automatically use them:
![[Note]](../images/note.png)
Note
There are frequent misunderstandings about this chapter. The procedures are the same as every other chapter, as explained earlier (Package build instructions). First, extract the gcc-14.2.0 tarball from the sources directory, and then change to the directory created. Only then should you proceed with the instructions below.
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
On 64-bit MIPS hosts, set the default directory name for 64-bit libraries to “lib”:
sed -e 's/lib64/lib/' \
-i.orig gcc/config/mips/{mips.h,t-linux64}
The GCC documentation recommends building GCC in a dedicated build directory:
mkdir -v build cd build
Probe the NaN encoding of the CPU:
cat > nan2008.c << \EOF
#include <stdio.h>
int main()
{
int x;
asm("cfc1\t%0,$31":"=r"(x));
return !(x & 1 << 18);
}
EOF
gcc nan2008.c -o nan2008
if ./nan2008; then
NAN_SWITCH=--with-nan=2008
fi
Prepare GCC for compilation:
../configure \
--target=$LFS_TGT \
--prefix=$LFS/tools \
--with-arch=mips64r2 \
--with-glibc-version=2.40 \
--with-sysroot=$LFS \
--with-newlib \
--without-headers \
--enable-default-pie \
--enable-default-ssp \
--disable-nls \
--disable-shared \
--disable-multilib \
--disable-threads \
--disable-libatomic \
--disable-libgomp \
--disable-libquadmath \
--disable-libssp \
--disable-libvtv \
--disable-libstdcxx \
--enable-languages=c,c++ \
$NAN_SWITCH
The meaning of the configure options:
-
--with-arch=mips64r2 -
Set the default value of
-march=to mips64r2. Most distros use it as the baseline for the MIPS port, so we are doing the same. You may change it if your CPU is not compatible with mips64r2 (for example, mips3 or mips64r6), or your CPU is stronger than mips64r2 and you don't care about the compatibility with mips64r2, but we've not tested any setting other than mips64r2. -
--with-glibc-version=2.40 -
This option specifies the version of Glibc which will be used on the target. It is not relevant to the libc of the host distro because everything compiled by pass1 GCC will run in the chroot environment, which is isolated from libc of the host distro.
-
--with-newlib -
Since a working C library is not yet available, this ensures that the inhibit_libc constant is defined when building libgcc. This prevents the compiling of any code that requires libc support.
-
--without-headers -
When creating a complete cross-compiler, GCC requires standard headers compatible with the target system. For our purposes these headers will not be needed. This switch prevents GCC from looking for them.
-
--enable-default-pie and --enable-default-ssp -
Those switches allow GCC to compile programs with some hardening security features (more information on those in the note on PIE and SSP in chapter 8) by default. They are not strictly needed at this stage, since the compiler will only produce temporary executables. But it is cleaner to have the temporary packages be as close as possible to the final ones.
-
--disable-shared -
This switch forces GCC to link its internal libraries statically. We need this because the shared libraries require Glibc, which is not yet installed on the target system.
-
--disable-multilib -
On 64-bit MIPS, LFS does not support a multilib configuration.
-
--disable-threads, --disable-libatomic, --disable-libgomp, --disable-libquadmath, --disable-libssp, --disable-libvtv, --disable-libstdcxx -
These switches disable support for threading, libatomic, libgomp, libquadmath, libssp, libvtv, and the C++ standard library respectively. These features may fail to compile when building a cross-compiler and are not necessary for the task of cross-compiling the temporary libc.
-
--enable-languages=c,c++ -
This option ensures that only the C and C++ compilers are built. These are the only languages needed now.
-
$NAN_SWITCH -
If the CPU encodes NaN (Not a Number) values following IEEE 754-2008 (indicated by the 16th bit of FCSR), this variable will be set to
--with-nan=2008so GCC will be configured to use the IEEE 754-2008 encoding for NaN values as the default. If this option is not properly set to match the CPU, depending on the host kernel configuration, the programs compiled by GCC may fail to start withExec format error(causing Section 7.4, “Entering the Chroot Environment” to fail), or produce bad results (causing test failures building some packages, for example Glibc and Python).
Compile GCC by running:
make
Install the package:
make install
This build of GCC has installed a couple of internal system
headers. Normally one of them, limits.h, would in turn include the corresponding
system limits.h header, in this case,
$LFS/usr/include/limits.h. However,
at the time of this build of GCC $LFS/usr/include/limits.h does not exist, so the
internal header that has just been installed is a partial,
self-contained file and does not include the extended features of
the system header. This is adequate for building Glibc, but the
full internal header will be needed later. Create a full version of
the internal header using a command that is identical to what the
GCC build system does in normal circumstances:
Note
The command below shows an example of nested command substitution
using two methods: backquotes and a $() construct. It could be rewritten using the
same method for both substitutions, but is shown this way to
demonstrate how they can be mixed. Generally the $() method is preferred.
cd .. cat gcc/limitx.h gcc/glimits.h gcc/limity.h > \ `dirname $($LFS_TGT-gcc -print-libgcc-file-name)`/include/limits.h