cc-wrapper: expose the c++ std library being used

    inherit bintools;

    inherit cc libc libcxx nativeTools nativeLibc nativePrefix isGNU isClang;

    # Expose the C++ standard library we're using. See the comments on "General

    # libc++ support". This is also relevant when using older gcc than the

    # stdenv's, as may be required e.g. by CUDAToolkit's nvcc.

    cxxStdlib =

      let

        givenLibcxx = libcxx.isLLVM or false;

        givenGccForLibs = useGccForLibs && gccForLibs.langCC or false;

      in

      if (!givenLibcxx) && givenGccForLibs then

        { kind = "libstdc++"; lib = gccForLibs; }

      else if givenLibcxx then

        { kind = "libc++"; lib = libcxx; }

      else

      # We're probably using the `libstdc++` that came with our `gcc`.

      # TODO: this is maybe not always correct?

      # TODO: what happens when `nativeTools = true`?

        { kind = "libstdc++"; lib = cc_solib; }

    ;

    emacsBufferSetup = pkgs: ''

      ; We should handle propagation here too

      (mapc

      echo "-L${gccForLibs}/lib/gcc/${targetPlatform.config}/${gccForLibs.version}" >> $out/nix-support/cc-ldflags

      echo "-L${gccForLibs_solib}/lib" >> $out/nix-support/cc-ldflags

    ''

    # The above "fix" may be incorrect; gcc.cc.lib doesn't contain a

    # `target-triple` dir but the correct fix may be to just remove the above?

    #

    # For clang it's not necessary (see `--gcc-toolchain` below) and for other

    # situations adding in the above will bring in lots of other gcc libraries

    # (i.e. sanitizer libraries, `libatomic`, `libquadmath`) besides just

    # `libstdc++`; this may actually break clang.

    # TODO We would like to connect this to `useGccForLibs`, but we cannot yet

    # because `libcxxStdenv` on linux still needs this. Maybe someday we'll