long double __far powl(long double x, long double y); (C99)
If x < 0 and y is a non-integer or if x = 0 and y <= 0, powl returns a Not-a-Number (NaN) and sets the macro EDOM for the global variable errno.
If an overflow occurs, powl returns ±∞ and sets the macro ERANGE for errno.
If an underflow occurs, powl returns a denormal number and sets the macro ERANGE for errno.