The Collection Manager is available to 64-bit applications, but unlike many other APIs, the itemSize parameters have not been widened to 64 bits; they remain SInt32. This can cause problems if your code is already casting an itemSize parameter to an SInt32* type before calling a Collection Manager function. For example, this code will compile without warnings in a 64-bit target but will fail at runtime because sizeof(ByteCount) is no longer equal to sizeof(SInt32).