anchor.diff:  , zlibSupport ? false, zlib ? null
   , sslSupport ? false, openssl ? null
   , scpSupport ? false, libssh2 ? null
  +, gssSupport ? false, gss ? null
   , linkStatic ? false
   }:
   
  
positive.code:   # Zlib and OpenSSL must be propagated because `libcurl.la' contains
    # "-lz -lssl", which aren't necessary direct build inputs of
    # applications that use Curl.
    propagatedBuildInputs =
      stdenv.lib.optional zlibSupport zlib ++
      stdenv.lib.optional sslSupport openssl;
  
    configureFlags = ''
      ${if sslSupport then "--with-ssl=${openssl}" else "--without-ssl"}
      ${if scpSupport then "--with-libssh2=${libssh2}" else "--without-libssh2"}
      ${if linkStatic then "--enable-static --disable-shared" else ""}
    '';
  
    dontDisableStatic = linkStatic;
  
  
negative.code:   crossAttrs = {
      # We should refer to the cross built openssl
      # For the 'urandom', maybe it should be a cross-system option
      configureFlags = [
          ( if sslSupport then "--with-ssl=${openssl.crossDrv}" else "--without-ssl" )
          "--with-random /dev/urandom"
        ]
        ++ stdenv.lib.optionals linkStatic [ "--enable-static" "--disable-shared" ]
      ;
    };
  
    passthru = {
      inherit sslSupport openssl;
    };
  
    meta = {
      homepage = "http://curl.haxx.se/";
      description = "A command line tool for transferring files with URL syntax";
  