Can somebody please identify the POSIX method by which one can wait on a set of descriptors, that does not involve spinning in a polling loop and gobbling up a CPU thread? The last time I had a need for such a thing, select() was the preferred way to do that.
If you want both portability and performance (as in, O(1) instead of O(N) as poll() and select() ), there's no portable standard. In that case you're better of with a wrapper library like libuv or livev.
Aside from being a lot more recent (posix 2001), poll was also broken on macOS until 10.9. Though you can always use kqueue instead that remains a portability annoyance: Linux still doesn’t have kqueue.
And with io_uring around it never will unless someone does a pure userspace implementation. Not certain if possible but it might be.