Question

In Visual Studio 2008 (C++) I have a class destructor (Let’s call this class ‘A’) which deletes a pointer to a different class (Let’s call this class ‘B’).

it looks like this:

A::~A()
{
    delete B;
    B = NULL;
}

My B class has a pointer to the instance of A that created it. In B’s destructor, I delete everything in B, except for the pointer to the instance of A.

In my debug build, it works okay, but fails on my release build..

In the debug build, right after B is deleted but before B is reassigned to NULL, The value of the pointer to the instance of A is something weird like 0xdddddddd.. However in the Release build, it is still pointing to the instance of A.. In both cases the pointer to B is still valid and B is not destroyed. What is going on and how do I fix it?

Answer 1

If I understand what you are saying, everything is working perfectly fine. After the call to delete B, the pointer held by variable B will be unchanged. It will still contain the address of the memory. The memory may or may not change; that part is completely undefined and depends on other things happening in the system at the moment and what the heap manager does.

After the delete to B is completed (and B’s destructor has run), the memory in which B was stored may or may not be changed (again it depends on the heap manager). So the fact that B’s pointer to A is changed in one build type and not the other is fine. After the delete, you cannot use anything in B.