anchor.diff:      "-DCLANG_PATH_TO_LLVM_BUILD=${llvm}"
       "-DCMAKE_BUILD_TYPE=Release"
       "-DLLVM_TARGETS_TO_BUILD=all"
  +    "-DGCC_INSTALL_PREFIX=${gccReal}"
     ] ++ stdenv.lib.optionals (stdenv.gcc.libc != null) [
       "-DC_INCLUDE_DIRS=${stdenv.gcc.libc}/include/"
     ];
  
positive.code:     homepage = http://clang.llvm.org/;
      description = "A C language family frontend for LLVM";
      license = "BSD";
      maintainers = with stdenv.lib.maintainers; [viric shlevy];
      platforms = with stdenv.lib.platforms; all;
    };
  }
  
negative.code: { stdenv, fetchurl, perl, groff, llvm, cmake }:
  
  let
    version = "3.1";
    gccReal = if (stdenv.gcc.gcc or null) == null then stdenv.gcc else stdenv.gcc.gcc;
  in
  
  stdenv.mkDerivation {
    name = "clang-${version}";
  