anchor.diff:      (enableFeature gprofSupport "gprof")
       (enableFeature gcovSupport "gcov")
       # Required to build shared libraries
  -    (enableFeature (!isCygwin) "pic")
  +    (enableFeature true "pic")
       (enableFeature (isi686 || isx86_64) "use-x86inc")
       (enableFeature optimizationsSupport "optimizations")
       (enableFeature runtimeCpuDetectSupport "runtime-cpu-detect")
  
positive.code: assert postprocVisualizerSupport -> postprocSupport;
  assert unitTestsSupport -> curl != null && coreutils != null;
  assert vp9HighbitdepthSupport -> (vp9DecoderSupport || vp9EncoderSupport);
  assert isCygwin -> unitTestsSupport && webmIOSupport && libyuvSupport;
  
  stdenv.mkDerivation rec {
    name = "libvpx-${version}";
  
negative.code: }:
  
  let
    inherit (stdenv) isi686 isx86_64 is64bit;
    inherit (stdenv.lib) enableFeature optional optionals;
  in
  
  assert isi686 || isx86_64; # Requires ARM with floating point support
  
  assert vp8DecoderSupport || vp8EncoderSupport || vp9DecoderSupport || vp9EncoderSupport;
  assert internalStatsSupport && (vp9DecoderSupport || vp9EncoderSupport) -> postprocSupport;
  