Question

I have an issue with a memory leak. I have a base-class pointer. From it, I use new to allocate different derived classes. Then, when I try to delete those classes with the reference (not typecasted), I get a memory leak. I researched the problem and found that I should add a virtual destructor to the base-class, but I tried this and I still have a memory leak; that is, according to my task-manager, the memory usage continues to rise with each allocation and deletion of the derived class using the base-class pointer. I tried making it an abstract destructor and added destructors to the derived classes, but I got an undefined reference error. I also tried typecasting the pointer as a derived-class pointer for the delete, but apparently this crashes the program.

Does anyone have any idea what I should do?

Example code:

class A {
public:
  A();
  ~A() {};
  virtual ~A();      /*or*/
  virtual ~A()=0;    /*or*/
                     /*or nothing?*/
}

class B: private A {
public:
  B();
  ~B() {};           /*this?*/
                     /*or nothing?*/
}

Answer 1

use virtual ~A();

I’d be surprised if virtual ~A()=0 is allowed.

With this code:

A* base = new B();
delete base;

the destructor for B then A will be called.

If you’re really still leaking memory, then you have another leak elsewhere.