x                  The converted string.
    0                  Indicates the conversion could not be
                       performed. errno is set to one of the
                       following:

                       o  EINVAL - No conversion could be performed.

                       o  ERANGE - The value would cause an
                          underflow.

                       o  ENOMEM - Not enough memory available for
                          internal conversion buffer.

    HUGE_VAL           Overflow occurred; errno is set to ERANGE.