NULL may be passed as the value in, out, in-out; or as a return value.
The intention of a Stable interface is to enable arbitrary third parties to develop applications to these interfaces, release them, and have confidence that they will run on all minor releases of the product (after the one in which the interface was introduced, and within the same major release). Even at a major release, incompatible changes are expected to be rare, and to have strong justifications.
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.