> > 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.

Indeed, this may be even better.

> 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.

You are right, we need a manual reset *or* we must ensure that every
user of _PyOS_SigintEvent only does so from the main thread.