anchor.diff:  
     src = fetchurl {
       url = "${meta.homepage}/poppler-${version}.tar.xz";
  -    sha256 = "0lfs1b1jfamxl13zbl5n448dqvl9n8frbv8180y7b7kfyaw7wx61";
  +    sha256 = "00yv7011y40jc5iw9b7zjyg8ij5wsfbjm32kli5qha1ij11majz4";
     };
   
     outputs = [ "out" "dev" ];
  
positive.code: }:
  
  let # beware: updates often break cups-filters build
    version = "0.72.0";
    mkFlag = optset: flag: "-DENABLE_${flag}=${if optset then "on" else "off"}";
  in
  stdenv.mkDerivation rec {
  
negative.code:   CXXFLAGS = stdenv.lib.optionalString stdenv.cc.isClang "-std=c++14";
  
    cmakeFlags = [
      (mkFlag true "UNSTABLE_API_ABI_HEADERS") # previously "XPDF_HEADERS"
      (mkFlag (!minimal) "GLIB")
      (mkFlag (!minimal) "CPP")
      (mkFlag (!minimal) "LIBCURL")
  