Constructor Inheritance in C 11: How Does It Work?

Inheriting Constructors in C 11

In C 11, constructor inheritance allows a derived class to implicitly inherit constructors from its base class. This is achieved through the using keyword, which specifies that the derived class should use the constructors of the base class.

Syntax:

struct B {
  B(int); // Normal constructor 1
  B(string); // Normal constructor 2
};

struct D : B {
  using B::B; // Inherit constructors from B
};

Implications:

• The derived class D now has the inherited constructors:

  • D::D(int);
  • D::D(string);
• Member variables of D are default-initialized by these inherited constructors.

Applications:

Constructor inheritance is useful in the following scenarios:

• Saving typing effort: It eliminates the need to manually define constructors in the derived class.
• Ensuring base-class initialization: It guarantees that the base class is initialized properly.

In-Depth Explanation:

The Standard Library defines the inheriting constructors as follows:

D::D(int x) : B(x) {}
D::D(string s) : B(s) {}

This means that when an instance of the derived class D is constructed, it will call the appropriate constructor of the base class B to initialize its base members.

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