Question

I am trying to understand Destructor. I got following issue. Here in the below snippet why the object b2 is out of scope for Destructor ?

class D
{
   B *b1;
   public:
   D()
   {
       b1 = new B;
       B *b2=new B;
       cout<<"D's Constructor Invoked"<<endl;
       //delete b2;
   }
   ~D()
   {
       delete b1;
       delete b2;  // error : undeclared identifier
       cout<<"D's Destructor Invoked"<<endl;
   }
};

B is just a simple class.

Thanks

Answer 1

b2 is a variable local to the constructor. What you’re trying to do is essentially equivalent to:

   void f()
   {
       B *b2=new B;
   }

   void g()
   {
       delete b2;  // error : undeclared identifier
   }

which I guess you understand why it doesn’t work. (g has its own scope and its own set of local variables, disjoint from those of f.)

Instead, make b2 a member variable:

class D
{
   B *b1;
   B *b2;
   public:
   D()
   {
       b1 = new B;
       b2 = new B;
       cout<<"D's Constructor Invoked"<<endl;
   }
   ~D()
   {
       delete b1;
       delete b2;  // works!
       cout<<"D's Destructor Invoked"<<endl;
   }
};