Inheritance and Compiler-Generated functions

Question

When i have inheritance, does the compiler-generated functions that i usually get (constructor, destructor, assignment operator and copy constructor) are still generated for my classes?

Let's say i have this inheritance: A base class, B which inherits A (public) and C which public inherits B. My A class has no memory allocation or anything that requires a destructor to be implemented by me, and i'm not implementing a destructor there, when i compile my program will it still create an empty A::~A(){} ?

Same for B and C.. Thank you!

Answer 1

The rule of 5 still applies to each of the classes, independent of their inheritence.

In other words, if B is derived from A, just because A defined their copy constructor, that doesn't affect the generation of Bs copy constructor.

You should, however, be mindful to define a virtual destructor for the base class if needed.

Answer 2

Yes, of course. And the constructor/destructor chained calls are still present (i.e., C destructor will call B destructor which calls A destructor, same in the reverse order for constructors).

Answer 3

Yes, Compiler always generates (constructor, destructor, assignment operator and copy constructor) for the classes , where user have not defined these functions explicitly.

Answer 4

Compiler inserts constructor, destructor,copy constructor and overloaded assignment operator in a class if it is not defined by the user.

But the most important thing is if user defines a parameterized constructor in a class,then compiler will not generate the default constructor and and object creation without any parameter will throw a linker error.

Say for example you have a class A

class A
{
int a;
public:
//.....
//some line of code 
//.....
}

If you don't provide any constructor, the compiler will generate a default constructor which does not takes any parameter A(){}.

But if by any chance you declare a parametrized constructor like

A(int i)
{
a = i;
}

The compiler doesn't generate any default constructor and your object creation with no parameter will fail.

 A a;    ---> This will fail.
 A b(10) ---> This will pass.

So thumb of rule is, if your are providing a constructor of your own, always provide the default constructor along with it.