Why is the Default Constructor of the Grandmother Class Invoked When Instantiating a Daughter Object Using Virtual Inheritance?

Impact of Virtual Inheritance on Default Constructor Invocation

When dealing with virtual inheritance, understanding the intricacies of constructor invocation is crucial. In the code provided, an object of type daughter is instantiated, leading to the unexpected invocation of the default grandmother() constructor.

A fundamental aspect of virtual inheritance is that the most derived class's constructor directly calls the virtual base class's constructor. In this situation, the daughter constructor calls the grandmother constructor directly, without an explicit invocation through the initialization list.

Since an explicit constructor for grandmother was omitted in the daughter class's initialization list, the compiler implicitly calls the default constructor. To rectify this issue, explicitly specify the desired constructor in the initialization list, as demonstrated in the following code snippet:

daughter(int attr) : grandmother(attr), mother(attr) { ... }

This modification ensures that the appropriate grandmother constructor is invoked, resolving the initial behavior. Furthermore, the FAQ entry provided offers additional insights into this topic for further clarification.

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