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Does having several levels of base classes slow down a class? A derives B derives C derives D derives F derives G, ...
Does multiple inheritance slow down a class?
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Answer. Yes, a class can inherit from more than one base class. The term for this is “multiple inheritance”. When inheriting from a single class, the base class is included in parenthesis as part of the class definition following the class name.
A derived class can have only one direct base class.
A class can be derived from more than one base class. In a multiple-inheritance model (where classes are derived from more than one base class), the base classes are specified using the base-list grammar element.
To answer your question, struct is slightly faster.
Non-virtual function-calls have absolutely no performance hit at run-time, in accordance with the c++ mantra that you shouldn't pay for what you don't use. In a virtual function call, you generally pay for an extra pointer lookup, no matter how many levels of inheritance, or number of base classes you have. Of course this is all implementation defined.
Edit: As noted elsewhere, in some multiple inheritance scenarios, an adjustment to the 'this' pointer is required before making the call. Raymond Chen describes how this works for COM objects. Basically, calling a virtual function on an object that inherits from multiple bases can require an extra subtraction and a jmp instruction on top of the extra pointer lookup required for a virtual call.
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