Class and pointer deletion

Question

I have a question about deleting an object and pointers to them. First test:

  a test;
  a* test_ptr;
  test_ptr = &test;
  test.aPrint();
  test_ptr->aPrint();
  delete(test_ptr);
  test.aPrint();

I've added printout in the constructor, destructor and function aPrint prints the text "aPrint" (ob).

constructor
aPrint
aPrint
destructor
aPrint
destructor

How can I get a call to the destructor twice? And how can I still use object test after deletion?

-----edit-----

So if I use new instead. Then I have to use delete or else I got leakage.

a* test_ptr;
test_ptr = new a;
test_ptr->aPrint();
delete(test_ptr);

Is this because this example uses the heap were the first example uses the stack?

doptimusprime · Accepted Answer · 2013-10-31 07:47:31Z

1

Since your object is on stack, its destructor will be called when this object will go out of the scope.

You are deleting one times and compiler is calling destructor implicitly another time.

That is why destructor is called twice.

However, behaviour of such program is not defined and be ready for any side-effect of double deletion.

answered Oct 31, 2013 at 7:47

doptimusprime

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Henrik · Accepted Answer · 2013-10-31 07:42:15Z

1

The object wasn't allocated using new, so it's undefined behavior to call delete. Just let it go out of scope, and the destructor will be called automatically (the second call in your example).

answered Oct 31, 2013 at 7:42

Henrik

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