NULL is OK, both for passing and for returning.
Parameter points to an array of items.
This parameter is a 'user_data', for callbacks; many bindings can pass NULL here.
Generics and defining elements of containers and arrays.
The callback is valid until first called.
Exposed in C code, not necessarily available in other languages.
Free data container after the code is done.
Free data after the code is done.
Don't free data after the code is done.
Override the parsed C type with given type.