Possibly incorrect answer to Exercise 2.23

[lisenkoevg]

The answer to ex.2.23 says:

Exercise 2.23: Given a pointer p, can you determine whether p points to a valid
object. If so, how? If not, why not?

By Faisal saadatmand

Yes. Any of the following methods would work:

if (p != nullptr)  // preferred new C++ standard
if (p != 0)
if (p != NULL)     // requires cstdlib header
if (!p)
if (p)

I suggest, fact that pointer p is not equals to nullptr (or 0 or NULL) doesn't say anything about validity of object it points to. I suppose, it is not possible to determine whether p points to a valid object (and even whether it point to any object at all).