The while(1) part of the event loop would be outside, provided by the stdlib. Each runtime would provide a set of FDs that they want to monitor, and a function

The while(1) part of the event loop would be outside, provided by the stdlib. Each runtime would provide a set of FDs that they want to monitor, and a function to execute a single iteration of their event loop. The while(1) loop would then be calling each runtime in a round-robin fashion, then go sleep while waiting on the union of all the runtimes’ FD sets. It would be sort of an “event loop of event loops”.