Possibility of ARC overflow in Swift?

Question

Swift uses "Automatic Reference Counting" to deallocate objects which are no longer referenced and thus no longer needed. The Swift language guide [1] states the following:

Every time you create a new instance of a class, ARC allocates a chunk of memory to store information about that instance. This memory holds information about [...] values of any stored properties associated with that instance.

I assume that the reference count gets stored as an integer. Could the reference counter then suffer from an overflow ? If this is the case, what implications would this have on my program, would the objects still getting referenced by others simply get deallocated ?

As an example: if the counter were, say, an unsigned 2 byte integer, this would put the upper limit of references to an object (while still having a correct reference count) at around 130k. Once that upper limit is reached and the object gets referenced once more, this would increment the counter by one, setting it to 0 again.

[1] https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/AutomaticReferenceCounting.html

Answer 1

NSObject's retainCount is a 64-bit unsigned integer on 64-bit OS's. And it's a 32-bit unsigned integer on 32 bit OS's. This is also the size of the address space, so it is impossible to create that many references to a single object and overflow the count.