Check valid pointer...

[ryu]

Hi GURUs,

I have a problem that will tickle GURUs brain

Imagine I have the following class:

class clsA
{
public:
   clsB *pObjB;

public:
   clsA()
   {
       pObjB = NULL;
   };
   ~clsA()
   {
      if(pObjB) delete pObjB;
   };
};

void main()
{
   clsA *pObjA1 = new clsA();
   clsA *pObjA2 = new clsA();

   pObjA1->pObjB = new clsB();
   pObjA2->pObjB = pObjA1->pObjB;

   delete pObjA1;   //the destructor will delete pObjB
   delete pObjA2;   //this will cause problem in the destructor since pObjB is not a valid pointer anymore (already been deleted previously by pObjA1 destructor)
}

As you can see, GURU, pObjB is been created once. Since both pObjA1 and pObjA2 point to the same pObjB, it will cause the memory exception because pObjA2 will try to delete pObjB that has been deleted by pObjA1.

My question is, how can I check whether pObjB is a valid pointer before I delete it in the destructor?

Thanks for any help from GURU(s) in advance...

Cheers