默认构造函数是否需要调用基类的默认构造函数？

Question

Was reading this answer and it surprised me, the suggestion you must always call a base class constructor in the derived class constructor. What if you are working only with default constructors, consider:

class Bar : public Foo {
private:
int y;

public:
Bar() : Foo(), y(0) {
}

...

Is the call to Foo() really necessary here?

Answer 1

You do not need to explicitly call a base class constructor in your constructor, in which case the compiler implicitly calls the default constructor, or you get a compile-time error, if none is callable.
Same applies to members who are non-POD.

An alternative is a member initialiser list only consisting of a delegation to another constructor of your class, thus creating a delegating constructor.

Answer 2

No, you don't. The reason why this is done is readability. It's clearer to read and might hint some IDEs helper logic like where the Baseclass::Baseclass() method is used.

Answer 3

您不需要调用它们，但就可读性而言，我认为这是一个好主意，并且还可以向审阅代码的人员证明您理解该类是派生的。