ARC does static lifetime tracking (or maybe better: ownership tracking) to remove redundant reference counting operations (highly simplfied: it basically makes

ARC does static lifetime tracking (or maybe better: ownership tracking) to remove redundant reference counting operations (highly simplfied: it basically makes the decision for you when to use the equivalent of a shared_ptr or unique_ptr under the hood - which is at least nice for API design, since functions just take or return generic "object references" instead of raw, shared or unique pointers like in C++ (which then is usually not what the caller wants in a specific situation). ARC is not perfect because it has to be fairly conservative (it can be manually tuned though), but ObjC still seems to give the compiler more static information than shared_ptr and unique_ptr in C++ which are purely stdlib runtime constructs.