> Hmm, it seems to me that it should be done in _poll() instead. 
> Otherwise, recv() will not be interruptible, will it?

Or maybe WaitForMultipleObjects() should be changed to also wait on sigint_event if called by the main thread.

> Also, after looking at this again, it seems sigint_event would be 
> better provided (at the C level) by the Python core, e.g. as 
> _PyOS_SigintEvent. The time module already uses a similar mechanism.

> By setting the event in the sigint handler itself, rather than in an 
> auxiliary HandlerRoutine callback function, it should also ensure 
> that, when the event is set, the "tripped" bit in signalmodule.c 
> has been set, meaning we wouldn't need to Sleep() anymore.

> (I also wonder why the event isn't auto-reset. Otherwise, there's a 
> race condition - which is probably harmless in most cases, but still.)

If it is an auto-reset event then we must worry about a non-main thread stealing the event.  Maybe _PyOS_SigintEvent() should return NULL if called by a non-main thread, and be documented with a loud usage warning.