Re: Making a smart pointer which works with incomplete types

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Sun, 07 Sep 2008 17:59:55 +0200

Message-ID:

<5bydnaJ9H-DhZ17VnZ2dnUVZ_uidnZ2d@posted.comnet>

* Juha Nieminen:

Alf P. Steinbach wrote:

Consider the following:

  template< typename T >
  void destroy( T* );

  template< typename T >
  class SmartPointer
  {
  ...
  public:
      ~SmartPointer() { if( ... ) { destroy( myReferent ); } }
  };

It achieves the same as the original code without any static pointer.

  From the point of view of incomplete types, exactly how is that
destructor different from this one:

      ~SmartPointer() { if( ... ) { delete myReferent; } }

  The whole idea with the deleter function pointer is that the
destructor of the smart pointer can delete the object even if the
object's type is incomplete in that context. How exactly does [the normal]
version achieve this?

As shown (quoted above).

Since this is utterly trivial -- I can't think of anything simpler -- I
suspect you're thinking of some way to implement it that will Not Work.

If so, post your code.

For more flexibility (in the direction that a static pointer could add
flexibility) make the deleter a template parameter.

The whole idea is to be able to delete the object with only an
incomplete type. Could you explain how the template parameter helps in
this task?

Sorry, that question is not meaningful to me.

Cheers, & hth.,

- Alf

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