[cfe-users] Can't find correct libstdc++ headers with --with-gcc-toolchain nor --with-cxx-include-root

[Hans Wennborg]

On Tue, Apr 22, 2014 at 3:38 PM, Steven Vormwald <sdvormwa at mtu.edu> wrote:
> Hello,
>
> I'm trying to build clang 3.4 to use libstdc++ from an installation of GCC
> 4.8.1, but I haven't been able to get clang to correctly locate the headers.
> I've tried configuring both using the '--with-gcc-toolchain' option and the
> '--with-cxx-include-root' option, but in both cases the resulting clang
> toolchain doesn't find the C++ headers.  I suspect this is because GCC was
> configured with a non-standard layout
> (--with-gxx-include-dir=$PREFIX/include/g++ rather than
> $PREFIX/include/c++).

You're right, --with-gcc-toolchain won't work with the non-standard
layout you're using. As you show in the clang output, it finds the gcc
install, but doesn't find the include dirs.

--with-cxx-include-root doesn't exist anymore; it was was replaced by
--with-gcc-toolchain in r149651.

Patching lib/Driver/ToolChains.cpp like you suggest
(Linux::AddClangCXXStdlibIncludeArgs is probably the relevant
function) sounds like the way forward. I have no idea if your gcc
install layout is common, but if it is you could try contributing a
patch.

Thanks,
Hans