Implement Inheritance - Githubissues

Implement inheritance!

This is done by -

Adding base class awareness to ICG
Completely remaking CompositeDataType.
- CompositeDataType is now an abstract class, and it must be overridden by SpecifiedCompositeType.
- SpecifiedCompositeType must be defined by template specialization. These are generated by ICG. The generic version can be used for a class with no members.
- An instantiation of a SpecifiedCompositeClass template looks like:


template <>
class SpecifiedCompositeType<B> : public CompositeDataType {

    public:
    SpecifiedCompositeType() : CompositeDataType("B", sizeof(B), &construct_composite<B>, &destruct_composite<B>) {}

    // this is how we determine offsets without having to deal with lookups at ICG time
    template<typename Derived>
    static MemberMap applyMembersToDerived () {
        using type_to_add = B;

        MemberMap derived_member_map = {
            {"c", StructMember("c", "double", offsetof(Derived, type_to_add::c))},
        };

        auto derived_members = SpecifiedCompositeType<A>::applyMembersToDerived<Derived>();
        derived_member_map.insert(derived_members.begin(), derived_members.end());

        return derived_member_map;
    }    

    MemberMap& getMemberMap () {
        using type_to_add = B;

        // the MemberMap exists as a static variable local to this function. Initialize it on first use by pulling in the derived members.        
        static bool initialized = false;
        static MemberMap member_map = {
            {"c", StructMember("c", "double", offsetof(type_to_add, c))},
        };

        if (!initialized) {
            auto derived_members = SpecifiedCompositeType<A>::applyMembersToDerived<B>();
            member_map.insert(derived_members.begin(), derived_members.end());

            initialized = true;
        }

        return member_map;
    }

    // this is just a const override of above
    const MemberMap& getMemberMap () const override {
        return (const_cast<SpecifiedCompositeType<B>*> (this))->getMemberMap();
    }
};

jdeans289 / icg2

Implement Inheritance #44