As stated in Section 5.3, SIDL longs are equivalent to those in C. Hence, they map to 64-bit integers in the middleware. However, since Python's unlimited precision integer data type is used in the bindings, the behaviour is not exactly like 64-bit integers (i.e. there is no overflow).
NOTE
For Python versions before 2.2, the code needs to guarantee that a Python
unlimited precision integer is used whenever a SIDL long is needed.
For example, calling isPrime -- whose SIDL
signature is bool isPrime(long num) -- as isPrime(1) will
fail. However, calling isPrime(1L) will succeed.