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.

Free data after the code is done.

Don't free data after the code is done.