[boost] Re: shifted_ptr review

From: cppljevans_at_[hidden]
Date: 2003-10-01 11:19:12

On 10/01/2003 10:52 AM, David Abrahams wrote:
> Gregory Colvin <gregory.colvin_at_[hidden]> writes:
> 
[snip]
>>>
>>>  template<typename T> shifted_ptr<T> make_shifted_ptr(cont T& t) {
>>>      return shifted_ptr(new(so) T(t));
>>>  }
>>>
>>>  ... make_shifted_ptr(Stuff()) ...
>>>
>>>are compilers allowed to optimize away the copy and construct the
>>>Stuff in place?
> 
[snip]
> Oh, wait.  You meant the copy of Stuff()?  It's not meant to be a T
> neccessarily.  It's just any old argument to T's constructor.  You
> need a bunch of overloads for make_shifted_ptr to make the example
> complete.
> 
Why couldn't the shifted_ptr(T*) be replaced with
shifted_ptr(make_shifted_ptr<T>&), where make_shifted_ptr<T> is
simply derived from auto_ptr but has no make_shifted_ptr(T*) CTOR?
No copy is needed and it simply turns over the T* to shifted_ptr<T>.
Just as David points out, there would need to be a bunch of
overloads for every T CTOR or at least those which
the user wants to put into shifted_ptr.