Hmm.  I would think it would be a good idea to have os.kill do posix emulation where that makes sense, it makes cross-platform usage easier.  That's what 'kill' with no signal does, right (kills the process, just like the posix default)?

The posix spec says "If sig is 0 (the null signal), error checking is performed but no signal is actually sent. The null signal can be used to check the validity of pid." So *signal* zero doesn't have any special meaning on posix, either, but it does have a special meaning to the kill command.

It seems like it would be nice to add support for that to the windows version, but I'm a little confused.  First you say that signal 0 has no special meaning, and then you say that it does (signal.CTRL_C_EVENT).  Which is it?