A
NULL is OK, both for passing and for returning.
Parameter points to an array of items.
E
Generics and defining elements of containers and arrays.
N
NULL may be passed as the value in, out, in-out; or as a return value.
S
Exposed in C code, not necessarily available in other languages.
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.
T
Free data after the code is done.
Don't free data after the code is done.