Py_SET_ERRNO_ON_MATH_ERROR() documentation also says that it is not reliable:

/* Py_SET_ERRNO_ON_MATH_ERROR(x)
 * If a libm function did not set errno, but it looks like the result
 * overflowed or not-a-number, set errno to ERANGE or EDOM.  Set errno
 * to 0 before calling a libm function, and invoke this macro after,
 * passing the function result.
 * Caution:
 *    This isn't reliable.  See Py_OVERFLOWED comments.
 *    X is evaluated more than once.
 */