anchor.diff:    NIX_CFLAGS_COMPILE = "-lm";
   
     postPatch = ''
  -    chmod +x tests/opencl/opencl_test.sh tests/buffer/buffer-tests-run.sh
  -    patchShebangs tests/ff-load-save/tests_ff_load_save.sh tests/opencl/opencl_test.sh tests/buffer/buffer-tests-run.sh tools/xml_insert.sh
  +    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
  
positive.code: { lib, stdenv
  , fetchurl
  , pkg-config
  , vala
  
negative.code: 
  stdenv.mkDerivation rec {
    pname = "gegl";
    version = "0.4.30";
  
    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-wRJ4LPQJaWniMhfM36vkIoTjXVQ1/wxD1A5McPrsqN0=";
    };
  
    nativeBuildInputs = [
  