3.3 RPC Runtime Check Notes
The behavior of the client when methods are executed can be
affected by the RPC protocol runtime checks and MIDL compiler options used when
generating stubs. For example, this often concerns error codes when passing the
NULL value in parameters with the
attribute. In these cases, the IDL method does not return the expected error
code. Instead, an RPC exception is raised.
For more information about generating RPC stubs from IDL definitions, see the topic "Using the MIDL Compiler" in [MSDN-MIDL].