[pjc50]

I had no idea this feature existed! Does it behave usefully in a multithreaded context?

[clarry]

Yes it does. N1570 7.6:

> The floating-point environment has thread storage duration. The initial state for a thread's floating-point environment is the current state of the floating-point environment of the thread that creates it at the time of creation.

[dfranke]

I think it uses thread-local storage like errno does, but I'd have to verify.