anchor.diff:  
     enableParallelBuilding = true;
     nativeBuildInputs = [ pkgconfig ];
  -  buildInputs = [ tcl readline libffi python3 bison flex ];
  +  buildInputs = [ tcl readline libffi python3 bison flex protobuf ];
  +
  +  makeFlags = [ "ENABLE_PROTOBUF=1" ];
   
     patchPhase = ''
       substituteInPlace ../yosys-abc/Makefile \
  
positive.code: { stdenv, fetchFromGitHub
  , pkgconfig, tcl, readline, libffi, python3, bison, flex
  }:
  
  with builtins;
  
  stdenv.mkDerivation rec {
    name = "yosys-${version}";
    version = "2018.05.03";
  
    srcs = [
      (fetchFromGitHub {
        owner  = "yosyshq";
        repo   = "yosys";
        rev    = "a572b495387743a58111e7264917a497faa17ebf";
        sha256 = "0q4xh4sy3n83c8il8lygzv0i6ca4qw36i2k6qz6giw0wd2pkibkb";
        name   = "yosys";
      })
  
  
negative.code:     (fetchFromGitHub {
        owner  = "berkeley-abc";
        repo   = "abc";
        rev    = "ae6716b064c842f45109a88e84dca71fe4cc311f";
        sha256 = "0g39k16dmrl6q73q39yr5yd9r4rcliz5zxzbnwzh29z9xwi6ipw8";
        name   = "yosys-abc";
      })
    ];
  