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.
Parameter for input. Default is transfer none.
Parameter for input and for returning results. Default is transfer full.
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.
Out parameter, where caller must allocate storage.
The callback is valid only during the call to the method.
Exposed in C code, not necessarily available in other languages.
The caller owns the data, and is responsible for free it.
The data is owned by the callee, which is responsible of freeing it.