anchor.diff:    name    = "compcert-${version}";
     version = "3.5";
   
  -  src = fetchurl {
  -    url    = "http://compcert.inria.fr/release/${name}.tgz";
  -    sha256 = "127s8nwsmpl7ng7h4yy8cci8p6ncsw8i8jq3z0pyhx2siryddq0v";
  +  src = fetchFromGitHub {
  +    owner = "AbsInt";
  +    repo = "CompCert";
  +    rev = "v${version}";
  +    sha256 = "1g8067a5x3vd0l47d04gjvy5yx49nghh55am5d1fbrjirfsnsz8j";
     };
   
     nativeBuildInputs = [ makeWrapper ];
  
positive.code:   enableParallelBuilding = true;
  
    patchPhase = ''
      substituteInPlace ./VERSION --replace 3.4 3.5
      substituteInPlace ./configure \
        --replace '{toolprefix}gcc' '{toolprefix}cc'
    '';
  
negative.code: { stdenv, lib, fetchFromGitHub, fetchpatch, makeWrapper
  , coq, ocamlPackages, coq2html
  , tools ? stdenv.cc
  }:
  