anchor.diff: -{ lib, stdenv
  +{ lib
  +, stdenv
   , fetchurl
   , pkg-config
   , vala
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "gegl";
    version = "0.4.28";
  
    outputs = [ "out" "dev" "devdoc" ];
    outputBin = "dev";
  
    src = fetchurl {
      url = "https://download.gimp.org/pub/gegl/${lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
      sha256 = "sha256-HRENhXfVTMo7NCOTFb03xXzLJ91DVWVQdKLSs/2JeQA=";
    };
  
    nativeBuildInputs = [
  
negative.code:   NIX_CFLAGS_COMPILE = "-lm";
  
    postPatch = ''
      chmod +x tests/opencl/opencl_test.sh
      patchShebangs tests/ff-load-save/tests_ff_load_save.sh tests/opencl/opencl_test.sh tools/xml_insert.sh
    '';
  
    # tests fail to connect to the com.apple.fonts daemon in sandboxed mode
  