A small post that documents something that almost no one appears to know. And if you do anything with floating point, you do need to know: always use feenableexcept()
This seems to suffer from the same problem that fast-math suffers from: you enable it for everyone, including all the libraries you use. Those might rely on the exact opposite state (as that's the default).
@robryk hasn't hurt me yet. And easy enough to discover.