anchor.diff: -{ stdenv, lib, fetchurl
  +{ stdenv, lib, fetchurl, fetchpatch
   , coq, ocamlPackages
   , tools ? stdenv.cc
   }:
  
positive.code: 
  stdenv.mkDerivation rec {
    name    = "compcert-${version}";
    version = "3.2";
  
    src = fetchurl {
      url    = "http://compcert.inria.fr/release/${name}.tgz";
      sha256 = "11q4121s0rxva63njjwya7syfx9w0p4hzr6avh8s57vfbrcakc93";
    };
  
    buildInputs = [ coq ]
  
negative.code: 
    enableParallelBuilding = true;
  
    patches = [ (fetchpatch {
      url = "https://github.com/AbsInt/CompCert/commit/679ecfeaa24c0615fa1999e9582bf2af6a9f35e7.patch";
     sha256 = "04yrn6dp57aw6lmlr4yssjlx9cxix0mlmaw7gfhwyz5bzqc2za1a";
    })];
  
    configurePhase = ''
      substituteInPlace ./configure --replace '{toolprefix}gcc' '{toolprefix}cc'
  