tomalakgeretkal

What _are_ allowed? I can't find it documented anywhere.

I think some of the innards aren't necessarily set up yet when `_setCFClientFlags` first gets invoked on certain systems (I'm seeing this on macOS 10.14, but not 10.15). The `copiedCallback`...

Actually I'll leave the PR to someone else, but if you're only integrating with NSUrlSessions then you can skip all the callback invocations (in both read and setCFClientFlags). Otherwise you'll...

Amalgamated.

Looks amalgamated here :( check-amalgamate works for me!