x                  On successful completion, x*(2**n) is
                       returned.
    HUGE_VAL           On overflow, scalb returns HUGE_VAL (according
                       to the sign of x) and sets errno to ERANGE.
    0                  Underflow occurred; errno is set to ERANGE.
    x                  x is Infinity.
    NaN                x or n is NaN; errno is set to EDOM.