Does C++ require you to initialize base class members from its derived class?

Question

class Base {
public:
    int a;
    Base():a(0) {}
    virtual ~Base();
}
class Derived : public Base {
public:
    int b;
    Derived():b(0) {
        Base* pBase = static_cast<Base*>(this);
        pBase->Base();
    }
    ~Derived();
}

Is the call to the base class constructor necessary or does c++ do this automatically? e.g. Does C++ require you to initialize base class members from any derived class?

Answer 1

The base class's constructor will automatically be called before the derived class's constructor is called.

You can explicitly specify which base constructor to call (if it has multiple) using initialization lists:

class Base {
  public:
    int a;
    Base():a(0) {}
    Base(int a):a(a) {}
};
class Derived {
  public:
    int b;
    Derived():Base(),b(0) {}
    Derived(int a):Base(a),b(0) {}
};

Answer 2

Base class constructors are called automatically (and before derived class contructors). So you need not, and must not, try to call base constructors manually.