{ stdenv, fetchsvn, cmake, libunwind }:

let rev = "190100"; in

stdenv.mkDerivation rec {
  name = "libc++-pre${rev}";

  src = fetchsvn {
    url = "http://llvm.org/svn/llvm-project/libcxx/trunk";
    inherit rev;
    sha256 = "0hnfvzzrkj797kp9sk2yncvbmiyx0d72k8bys3z7l6i47d37xv03";
  };

  cxxabi = fetchsvn {
    url = "http://llvm.org/svn/llvm-project/libcxxabi/trunk";
    inherit rev;
    sha256 = "1kdyvngwd229cgmcqpawaf0qizas8bqc0g8s08fmbgwsrh1qrryp";
  };

  buildInputs = [ cmake ];

  preConfigure = ''
      sed -i 's/;cxa_demangle.h//' CMakeLists.txt
      cp -R ${cxxabi} cxxabi
      chmod u+w -R cxxabi # umm
      (export NIX_CFLAGS_COMPILE="-I${libunwind}/include -I$PWD/include";
       export NIX_CFLAGS_LINK="-L${libunwind}/lib -lunwind";
       cd cxxabi/lib
       sed -e s,-lstdc++,, -i buildit # do not link to libstdc++!
       ./buildit
       mkdir -p $out/lib && cp libc++abi.so.1.0 $out/lib
       cd $out/lib
       ln -s libc++abi.so.1.0 libc++abi.so
       ln -s libc++abi.so.1.0 libc++abi.so.1)
  '';

  cmakeFlags = [ "-DCMAKE_BUILD_TYPE=Release"
                 "-DLIBCXX_LIBCXXABI_INCLUDE_PATHS=${cxxabi}/include"
                 "-DLIBCXX_CXX_ABI=libcxxabi" ];
  buildPhase = ''NIX_CFLAGS_LINK="-L$out/lib -lc++abi" make'';

  enableParallelBuilding = true;

  meta = {
    homepage = http://libcxx.llvm.org/;
    description = "A new implementation of the C++ standard library, targeting C++11";
    license = "BSD";
    maintainers = stdenv.lib.maintainers.shlevy;
    platforms = stdenv.lib.platforms.all;
  };
}