i had a question while i was reading the book "MEC++ chapter 3"

in the book, he says this will not work.

class BST
{
public:
virtual ~BST() { cout << "BST" << endl; }
};

class BalancedBST : public BST
{
public:
~BalancedBST() { cout << "BalancedBST" << endl; }
};

void delete(BST array[])
{
delete [] array;
}

BalancedBST *balTreeArray = new BalancedBST[10];

deleteArray(balTreeArray);


but with the VIsual C++ 2005 it seems to be worked fine

the set of "BalancedBST" and "BST" is printed 10 times.

did i understand the book wrong way? or it's just because of compiler
dependency?

SeniorLee wrote:

> i had a question while i was reading the book "MEC++ chapter 3"
>
> in the book, he says this will not work.
>
> class BST
> {
> public:
> virtual ~BST() { cout << "BST" << endl; }
> };
>
> class BalancedBST : public BST
> {
> public:
> ~BalancedBST() { cout << "BalancedBST" << endl; }
> };
>
> void delete(BST array[])
> {
> delete [] array;
> }
>
> BalancedBST *balTreeArray = new BalancedBST[10];
>
> deleteArray(balTreeArray);
>
>
> but with the VIsual C++ 2005 it seems to be worked fine
>
> the set of "BalancedBST" and "BST" is printed 10 times.
>
> did i understand the book wrong way?

No.

> or it's just because of compiler dependency?

Yes. You have undefined behavior, which on your platform happens to look
fine. Hint: this can be caused by the size of the base and the derived
class being equal so that vtable pointers happen to reside at the right
position; however, even though the undefined behavior could have an
explanation, it is still undefined.


Best

Kai-Uwe Bux