anchor.diff:      itstool
     ];
   
  -  meta = with stdenv.lib; {
  +  passthru = {
  +    srcVerification = fetchurl {
  +      inherit (src)
  +        outputHash
  +        outputHashAlgo
  +        urls;
  +      sha256Url = "https://download.gnome.org/sources/gtk-doc/${version}/"
  +        + "${name}.sha256sum";
  +      failEarly = true;
  +    };
  +  };
  +
  +  meta = with lib; {
       description = "Tools for documentation embedded in GTK+/GNOME source code";
       homepage = http://www.gtk.org/gtk-doc;
       license = licenses.gpl2;
  
positive.code: { stdenv
  , fetchurl
  , which
  
  , perl
  
negative.code: , itstool
  }:
  
  let
    version = "1.26";
  in
  stdenv.mkDerivation rec {
    name = "gtk-doc-${version}";
  
    src = fetchurl {
      url = "mirror://gnome/sources/gtk-doc/${version}/${name}.tar.xz";
      sha256 = "bff3f44467b1d39775e94fad545f050faa7e8d68dc6a31aef5024ba3c2d7f2b7";
    };
  
    preConfigure =
  