CPP13 — Concrete ValueType _init class problem

The second-to-last paragraph of section 1.17.10.3 says

"For valuetypes that have no operations or initializers, a concrete type-specific factory class is generated whose implementation of the create_for_unmarshal function simply constructs an instance of the OBV_ class for the valuetype using new and the default constructor."

As specified, that requires the generation of invalid C++. The OBV_ class is abstract since it does not have implementations of the ValueBase reference counting functions.

Perhaps the intention is that the OBV_ classes in such cases should derive from DefaultValueRefCountBase. However, the wording and explanation in section 1.17.6 explicitly forbids this:

"Note that it is the application-supplied concrete valuetype classes that must derive from these mix-in classes, not the valuetype classes generated by the IDL compiler."

One solution that avoids the problem, and avoids restricting the application's use of the OBV_ classes is to generate yet another class that derives from both the OBV_ class and DefaultValueRefCountBase, for instantiation by the _init class's create_for_unmarshal function.