Re: [boost] [boost.move] move_ptr

From: Bronek Kozicki (brok_at_[hidden])
Date: 2004-08-27 10:49:00

Howard Hinnant wrote:
>> So that sizeof(move_ptr<T>) can be the same as sizeof(T*).
> 
> 
> Yes, yes!  Absolutely zero-overhead over a raw pointer is (imho) a 
> critical design criteria of this type of smart pointer.  And the reason 
> for the ::type dance instead of something more direct like:
> 
> template<class T, class D = detail::default_delete<T> >

OK, I guess that detail::default_delete<T> is going to be stored as 
static field of move_ptr class. However  ...

> 2.  And the deleter itself should be able to be a reference type.
> 
> I can't stress this second point enough.  It is a real feature when you 
> want to allow for the possibility of a deleter that is both state-full 
> and heavy.  In templated code that already owns a deleter (that you 
> don't know anything about, except its name), and you're using the 
> move_ptr just to enforce ownership temporarily (say for exception safety 
> purposes), then passing a reference-typed deleter to the move_ptr is an 
> extremely elegant solution:
> 
> Code templated on P (p : pointer type) and D (d_ : deleter type):
> 
>     move_ptr<P, D&> hold(p, d_);   // grab hold of p, using a D&, as 
> opposed to a D

... how are you going to store reference to deleter object here, without 
any memory overhead in your pointer object?

B.