It should be possible for an application developer to declare any client-side non-primitive arguments as _vars, assign values or not as appropriate, and pass them by calling *.in(), *.inout() or *.out() on the _vars, depending on the 'direction' of the IDL operation parameter declaration. The OMG's motivation for this mechanism was to provide a consistent interface for argument passing regardless of the size type of the argument. For fixed size structs and arrays, it is possible to optimize by using an arg declared on the stack, but the canonical way should also work.

Param_Test uses the optimized approach for fixed size structs, unions and arrays. It should be changed to use _vars for these client-side args.