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This mapping is similar to CORBA/COM, except for the following:
• Some COM primitive data types (for example, UNICODE long, unsigned long long, and wide char) and constructed types (for example, wide string) are not currently supported by OMG IDL. (These data types may be added to OMG IDL in the future.)
• Though it is less common, COM objects may be built directly in C and C++ (without exposing an interface specification) by providing custom marshaling implementations. If the interface can be expressed precisely in some COM formalism (MIDL, ODL, or a Type Library), it must first be hand-translated to such a form before any formal mapping can be constructed. If not, the interworking mechanism (such as the View, request transformation, and so forth) must be custom-built.
• MIDL, ODL, and Type Libraries are somewhat different, and some are not supported on certain Windows platforms; for example, MIDL is not available on Win16 platforms.
• Some unions, pointer types and the SAFEARRAY type require special handling.
The COM/CORBA mapping is somewhat further complicated, by the following issues: