Re: [boost] shared_ptr feature request

From: Peter Dimov (pdimov_at_[hidden])
Date: 2006-10-26 18:24:17

Emil Dotchevski wrote:

> template <class T>
> shared_ptr
> {
>    ....
>    template <class Y>
>    shared_ptr( shared_ptr<Y> const & sp, T * p ): px(p), pn(sp.pn)
>    {
>    }
>    ....
> };

This has already been proposed in

http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1851.pdf

along with a few other features. On the one hand, when you need it, it's 
unquestionably useful and carries no additional overhead. I also like how 
the casts are now implementable via the public interface. On the other hand, 
it could be argued that this constructor makes it uncomfortably easy to 
construct a shared_ptr that can dangle (because the lifetime of p is not 
properly bounded by sp.)