Linux From Scratch - Version r12.2-776-multilib

Chapter 5. Compiling a Cross-Toolchain

5.6. Libstdc++ from GCC-14.2.0

Libstdc++ is the standard C++ library. It is needed to compile C++ code (part of GCC is written in C++), but we had to defer its installation when we built gcc-pass1 because Libstdc++ depends on Glibc, which was not yet available in the target directory.

Approximate build time: 0.2 SBU
Required disk space: 1.2 GB

5.6.1. Installation of Target Libstdc++

[Note]

Note

Libstdc++ is part of the GCC sources. You should first unpack the GCC tarball and change to the gcc-14.2.0 directory.

Create a separate build directory for Libstdc++ and enter it: 

mkdir -v build
cd       build

Prepare Libstdc++ for compilation: 

../libstdc++-v3/configure           \
    --host=$LFS_TGT                 \
    --build=$(../config.guess)      \
    --prefix=/usr                   \
    --enable-multilib               \
    --disable-nls                   \
    --disable-libstdcxx-pch         \
    --with-gxx-include-dir=/tools/$LFS_TGT/include/c++/14.2.0

The meaning of the configure options:

--host=...

Specifies that the cross-compiler we have just built should be used instead of the one in /usr/bin.

--enable-multilib

Enable building multilib objects.

--disable-libstdcxx-pch

This switch prevents the installation of precompiled include files, which are not needed at this stage.

--with-gxx-include-dir=/tools/$LFS_TGT/include/c++/14.2.0

This specifies the installation directory for include files. Because Libstdc++ is the standard C++ library for LFS, this directory should match the location where the C++ compiler ($LFS_TGT-g++) would search for the standard C++ include files. In a normal build, this information is automatically passed to the Libstdc++ configure options from the top level directory. In our case, this information must be explicitly given. The C++ compiler will prepend the sysroot path $LFS (specified when building GCC-pass1) to the include file search path, so it will actually search in $LFS/tools/$LFS_TGT/include/c++/14.2.0. The combination of the DESTDIR variable (in the make install command below) and this switch causes the headers to be installed there.

Compile Libstdc++ by running: 

make

Install the library: 

make DESTDIR=$LFS install

Remove the libtool archive files because they are harmful for cross-compilation: 

rm -v $LFS/usr/lib/lib{stdc++{,exp,fs},supc++}.la

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