anchor.diff:          ++ optional langAda      "ada"
           ++ optional langVhdl     "vhdl"
           ++ optional langGo       "go"
  +        ++ optional langObjC     "objc"
  +        ++ optional langObjCpp   "obj-c++"
           ++ optionals crossDarwin [ "objc" "obj-c++" ]
           )
         )
  
positive.code:     else null;
  
    passthru =
      { inherit langC langCC langAda langFortran langVhdl langGo enableMultilib version; };
  
    inherit enableParallelBuilding;
  
  
negative.code: { stdenv, fetchurl, noSysDirs
  , langC ? true, langCC ? true, langFortran ? false
  , langObjC ? stdenv.isDarwin
  , langObjCpp ? stdenv.isDarwin
  , langJava ? false
  , langAda ? false
  , langVhdl ? false
  