how to make sure a dynamic variable is removed in C++?

Question

I had created some dynamic variable in a C++ code. When I had decided to check that the variable is deleted or not, I saw that I still can use it ! For example, in this code :

#include <iostream>
using namespace std;

int main ()
{
int *p=new int;
*p=3;
delete p;
cout<<*p;
return 0;
}

The output still is 3 ! What's the problem ?

Answer 1

The output is not necessarily 3. For me it outputs a number which i suppose is the memory of the pointer.
If you want to deallocate the memory that the pointer points to, you must nullify the pointer after deleting it.

Answer 2

(Black Winter)I tested it many times with different compilers but most of the time the pointer wasn't deleted

Answer 3

you cannot actually delete a pointer. what you are deleting is the allocated space created by new.
have you tested the code in Sololearn? I am using the app version and it is not displaying 3 after the delete.
what it points to after delete is undefined behavior so it's compiler dependent. It may still point to 3 or some other value.
That is why you must set your pointer to nullptr to prevent future use.

delete p;
p = nullptr;

an error will be raised if you try to use it again.

Answer 4

*3 no 3 yes