idd
test(idd(nextafter(DBL_MAX, INFINITY)), INFINITY, ex_over);
test(idd(nextafter(INFINITY, 0.0)), DBL_MAX, 0);
test(idd(nexttoward(DBL_MAX, DBL_MAX * 2.0L)), INFINITY, ex_over);
test(idd(nexttoward(INFINITY, DBL_MAX * 2.0L)), DBL_MAX, 0);
static double idd(double);