Multiple Inheritance from two derived classes

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It looks like you want to do virtual inheritance. Whether that turns out to actually be a good idea is another question, but here’s how you do it:


class AbsBase {...};
class AbsInit: public virtual AbsBase {...};
class AbsWork: public virtual AbsBase {...};
class NotAbsTotal: public AbsInit, public AbsWork {...};

Basically, the default, non-virtual multiple inheritance will include a copy of each base class in the derived class, and includes all their methods. This is why you have two copies of AbsBase — and the reason your method use is ambiguous is both sets of methods are loaded, so C++ has no way to know which copy to access!

Virtual inheritance condenses all references to a virtual base class into one datastructure. This should make the methods from the base class unambiguous again. However, note: if there is additional data in the two intermediate classes, there may be some small additional runtime overhead, to enable the code to find the shared virtual base class.

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