Re: "delete this" for object in Stack

From:
Goran <goran.pusic@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 15 Oct 2010 01:49:43 -0700 (PDT)
Message-ID:
<a18e063c-c33a-4a82-baff-1baf978a34f7@d25g2000yqc.googlegroups.com>
On Oct 15, 6:22 am, thomas <freshtho...@gmail.com> wrote:

Hi,

------------
class A {
public:
      ~A(){}
       void Release(){ delete this; }};

-----------
A *a = new A();
a->Release(); --> Method I
A a2;
a2.Release(); --> Method II
-----------

a is created in Heap while a2 is in Stack.
When I call "Release()", thus "delete this;" to these two different
kinds of object, what will happen?
If "delete this" just involves calling the destructor, I suppose they
are equivalent.


Not at all. operator delete invokes the destrucctor and then frees
allocated memory. Just like operator new allocates memory, then calls
the constructor. That's a rather fundamental aspect of what they do.

Any suggestions? Thanks.


Others already explained.

I'll add this: "delete this" is in general a bloody stupid idea with
rare situations where it's expedient. Your snippet is just a massive
bug.

C++ language, however, does allow you to design a type so that clients
have to use it on the heap, and that you have to call e.g. a Release
function (name is incidental). E.g.

class heap_only_please
{ // intentionally private:
  heap_only_please() {...}
  heap_only_please(const heap_only_please& ) {...};
  ~heap_only_please() {...}
  heap_only_please(params) {...}
public:
  static heap_only_please* create(params)
  {
    return new heap_only_please(params);
  }
  void Release() { delete this; }
  // Want refcounting? Put it in Release! ;-)
};

Goran.

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