anchor.diff:  
     NIX_CFLAGS_COMPILE = [
       "-I${libxml2.dev}/include/libxml2"
  +    "-Wno-error=implicit-fallthrough"
     ] ++ optional stdenv.isDarwin "-Wno-error=deprecated-declarations";
   
     preConfigure = (concatMapStringsSep "\n" (mod: mod.preConfigure or "") modules);
  
positive.code: { stdenv, fetchurl, openssl, zlib, pcre, libxml2, libxslt
  , gd, geoip, gperftools, jemalloc
  , withDebug ? false
  , withMail ? false
  
negative.code:     license     = licenses.bsd2;
      platforms   = platforms.all;
      maintainers = with maintainers; [ izorkin ];
    };
  }
  