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From: Powell, Gary (powellg_at_[hidden])
Date: 2003-09-30 11:45:09

> Powell > I'm a little concerned that it appears you can create bad pointers for
> Powell > this class by inadvertently not using placement new. I'd feel better
> Powell > about it if there was some way to prevent this.
> Abrahams >Generic smart pointer factories are the right way:
> Abrahams > shifted_ptr<U> p = make_shifted_ptr<T>(arg1, arg2, arg3, ref(arg4));
> So you are saying remove the constructor,
> template<class U>
> shifted_ptr( U *);
> and replace it with one that takes a temporary that is created only by make_shifted_ptr?

Abrahams >No, I was suggesting making the constructor private, making
Abrahams >make_shifted_ptr a friend, and have make_shifted_ptr<T>(...) return a
Abrahams >shifted_ptr<T>.

Abrahams >Your approach seems very complicated. Is there a reason to do it
Abrahams >that way?

Well depends whether you prefer and can compile.

template<class T>
  class shifted_ptr {
  template<class U, class Arg1>
       friend shifted_ptr<T> make_shifted_ptr();
  template<class U, class Arg1>
       friend shifted_ptr<T> make_shifted_ptr(Arg1 &);

  template<class U, class Arg1, class Arg2>
       friend shifted_ptr<T> make_shifted_ptr(Arg1 &, Arg2 &);

 Or the other way. If I remember correctly not all compilers used to be able to handle template friends. On the other hand the previous approach could have been due to a lack of caffeen.

So after looking at this for all of 5 minutes, if the friend make_shifted_ptr works, it looks easier to maintain. But in all cases taking raw pointers is to be avoided.


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