Question

Im playing with my smart pointer class and I want to implement ++ and — operators with the following behavior: If pointer points to single variable or if it points to array and ++(–) moves pointer out of array bounds an exception should be thrown when trying to ++(–).

Something like that:

class A;

SmartPtr<A> s(new A[3]);
SmartPtr<A> s1(new A());
++s;//ok
--s;//ok
--s;//exception OutOfBounds thrown
++s1;//exception OutOfBounds thrown
--s1;//exception OutOfBounds thrown

I tried to use typeid. But it returns A type anyway.

A* arr=new A[3];
typeid(arr).name();//type is P1A
typeid(--arr).name();//type is P1A
typeid(arr+7).name();//type is P1A

So is there any way to determine does pointer point to “my” type of object after ++(–)?

Answer 1

new A[3] returns an A*, just like new A does. So you can’t distinguish them.

If you want your class to do bounds checking, then you will need to explicitly tell it how many items are in the array.