> ALSO, while we're at it, the only global or thread-local variables you can read from or write to from a signal handler must be of type volatile sig_atomic_t (

> ALSO, while we're at it, the only global or thread-local variables you can read from or write to from a signal handler must be of type volatile sig_atomic_t (or else volatile of any other integral or pointer type that you can use with atomic operations). This is very important. I'd rather recommend C11 atomics without volatile. They use memory barriers to guarantee visibility, and getting the idea that "volatile" should be used in the context of atomics is a bad idea, as it allows reordering (unlike memory barriers).