What causes std::bad_function_call?

Question

I\'ve seen a few questions that refer to the std::bad_function_call exception, but haven\'t been able to find out any by Googling about what causes this exception.

W

Answer 1

Sure- the easiest is where you try to call a std::function that's empty.

int main() {
    std::function intfunc;
    int x = intfunc(); // BAD
}