C++ call virtual method in child class

Question

hi guys, i have the following classes:

class A {
protected:
     A *inner;
public:
    ....
    virtual void doSomething() = 0;
    ....
}

class B: public A {
   ...
   void doSomething() {
       if(inner != NULL)
           inner->doSomething();
   }
   ...
}

When I use inner->doSomething() I get a segmentation fault. What should I do in order to call inner->doSomething() in the B class?

thanks in advance.

Answer 1

Without an explicit initialization of the member inner, it's possible for it to be both not NULL and point to invalid memory. Can you show us the code that explicitly initalizes inner?

An appropriate constructor for A would be the following

protected:
A() : inner(NULL) {
  ...
}

Answer 2

though if you assign the A* to be the same as the B initialised this pointer you'll get a stack overflow ... Any reason you need the inner? Can't you just call A::DoSomething()?