Generics and defining elements of containers and arrays.

NULL may be passed as the value in, out, in-out; or as a return value.

NULL may be passed instead of a pointer to a location.

Parameter for returning results. Default is transfer full.

Exposed in C code, not necessarily available in other languages.

Alias for transfer none, used for objects with floating refs.

The caller owns the data, and is responsible for free it.

The data is owned by the callee, which is responsible of freeing it.