How can I delete dynamic array pointer correctly

Question

Possible Duplicate:
C++ delete - It deletes my objects but I can still access the data?
Why doesn't delete destroy anything?

I've Created dynamic array, and I added values ​​to the values ​​of the array like that.

int *pArr;
pArr = new int[10];

for(int i=0;i<10;i++){
   pArr[i] = i+2;
}

delete[] pArr;  

// After deletion I can find the value of the array items.
cout << pArr[5] << endl;

As you see in the code above and in the last line, I can output the fifth element in the array without any problem . With that supposed to be the array has been removed.

Answer 1

Once you delete[] the array and still try to access the elements of the array it is Undefined Behavior and any behavior is possible.

Answer 2

To show that the memory can be used again, consider this expansion of your code:

int *pArr;
pArr = new int[10];

for(int i=0;i<10;i++){
       pArr[i] = i+2;
}

delete[] pArr;

int *pArr2;
pArr2 = new int[10];

for(int i=0;i<10;i++){
       pArr2[i] = (2*i)+2;
}

cout << pArr[5] << endl;

That prints out 12 for me. i.e. the value from pArr2[5] actually. Or at least I should say it does for my machine with my specific compiler & version, etc. As others have pointed out it is undefined behaviour. But hopefully my example shows you at least one kind of undefined behaviour.

Answer 3

Yes, this may work, but is not guaranteed to work. Delete [] only invalidates the memory but does not zero it. The memory you are referencing is invalidate at this point. So don't do it :)