What is virtual inheritance?

Virtual inheritance is a unique concept in multiple inheritance,

Class D inherits from class B1,b2, and class B1,b2 inherits from Class A,

When Class A is a non-virtual base class, that is, when a class b1,b2 a non-virtual inheriting class A, the inheritance relationship is as follows:

A A

↓↓

B1 B2

D

The code is as follows:

1 class a{}; 2 class  Public a{}; 3 class  Public a{}; 4 class  Public  Public b2{};

Therefore, in order to save memory space, Class A can be defined as a virtual base class, that is, the class B1,B2 virtual inheritance Class A, the inheritance relationship is as follows:

A

B1 B2

D

The code is as follows:

1 class a{}; 2 class Virtual  a{}; 3 class Virtual  a{}; 4 class  Public  b2{};

What is virtual inheritance?