MIDL2164
The documentation lists this name without a value.
Documented in Win32
field/parameter must not derive from a structure that is recursive through a ref pointer By definition, a reference pointer cannot be set to NULL . A recursive data structure defined with a reference pointer has no NULL elements and by convention is nonterminating. Use a [ unique ] pointer attribute to allow the data structure to specify a NULL element, or redefine the data structure as a nonrecursive data structure.