Shared Pointers

The implementation details of shared pointers may be of interest to those using them. Specifically, the rules surrounding how and when shared and weak pointers are serialized and pooled may affect how you choose to use them.


Shared pointers (Rc and Arc) are serialized whenever they're encountered for the first time, and the data address is reused when subsequent shared pointers point to the same data. This means that you can expect shared pointers to always point to the same value when archived, even if they are unsized to different types.

Weak pointers (rc::Weak and sync::Weak) have serialization attempted as soon as they're encountered. The serialization process upgrades them, and if it succeeds it serializes them like shared pointers. Otherwise, it serializes them like None.


Similarly, shared pointers are deserialized on the first encounter and reused afterward. Weak pointers do a similar upgrade attempt when they're encountered for the first time.

Serializers and Deserializers

The serializers for shared pointers hold the location of the serialized data. This means it's safe to serialize shared pointers to an archive across multiple serialize calls as long as you use the same serializer for each one. Using a new serializer will still do the right thing, but may end up duplicating the shared data.

The deserializers for shared pointers hold a shared pointer to any deserialized values, and will hold them in memory until the deserializer is dropped. This means that if you serialize only weak pointers to some shared data, they will point to the correct value when deserialized but will point to nothing as soon as the deserializer is dropped.