Does a base class's constructor and destructor get called with the derived ones?

Question

I have a class called MyBase which has a constructor and destructor:

class MyBase
{
public:
    MyBase(void);
    ~MyBase(void);
};

and I have a class called Banana, that extends MyBase like so:

class Banana:public MyBase
{
public:
    Banana(void);
    ~Banana(void);
};

Does the implementation of the new constructor and destructor in Banana override the MyBase ones, or do they still exist, and get called say before or after the Banana constructor / destructor executes?

Thanks, and my apologies if my question seems silly.

Answer 1

A Base constructor will always be called before the derived constructor. The Base destructor will be called after Dervided destructor.

You can specify on derived constructor which Base constructor you want, if not the default one will be executed.

If you define other constructors but not default and don't specify on Derived constructor which one to execute it'll try default which doesn't exist and will crash compilation.

The above happens because once you declare one constructor no default constructors are generated.

Answer 2

Constructors cannot be overriden. You can't declare a base class constructor in a derived class. A class constructor has to call a constructor in base class (if one is not explicitly stated, the default constructor is called) prior to anything else.

To be able to clean up the derived class correctly, you should declare the base class destructor as virtual:

virtual ~MyBase() { ... }