Can the result of std::fetestexcept return multiple bits set, or does it only ever return a single bit?
It can return an int with up to as many bits set as you provided in the argument to std::fetestexcept. If you for example provided FE_ALL_EXCEPT as an argument, it may return an int with a combination of ...
FE_DIVBYZERO
FE_INEXACT
FE_INVALID
FE_OVERFLOW
FE_UNDERFLOW
... bitwise ORed together. To check for a certain bit, just do a bitwise AND with the constant you'd like to check:
if (std::fetestexcept(FE_ALL_EXCEPT) & FE_OVERFLOW) {
std::cout << "the overflow bit was set\n";
}
Of course, if you only provide a constant with a single bit set, like FE_OVERFLOW, it will only return an int with zero or one bit set and then you don't need the bitwise AND after the call:
if (std::fetestexcept(FE_OVERFLOW) {
std::cout << "the overflow bit was set\n";
}