How can I determine if a C++ object has been deallocated?

Question

I have a previous question that was answered in which I describe difficulties catching an exception when I try to access an object that has been deallocated by a third-party function. The function sometimes does and sometimes doesn't deallocate the object.

In order to avoid having to use a try/catch block to catch the SEH Exception as described in the previous question, I need to be able to tell whether the object has been deallocated or not.

How can I determine if a C++ object has been deallocated or is still a valid pointer?

Answer 1

You can't easily tell just by looking at the memory location if the object is still allocated or not. There might be some black magic tricks to do that, but a much cleaner way would be to build a call-back mechanism into the object's destructor.

Answer 2

I think you're asking the wrong question. The question really ought to be:

Why do I feel like I need to look at some address in order to find out whether the pointer pointing there refers to an object or to the garbage left after an ex-object was deleted?

Honestly, you shouldn't be in that situation. If an object is deleted, why are you left with a pointer to its ex-address? Ideally, the pointer should be out of scope. If that isn't possible in your code, it should have been set to NULL.