Re: [boost] [shared_ptr] delete shared_ptr

Subject: Re: [boost] [shared_ptr] delete shared_ptr
From: Kenny Riddile (kfriddile_at_[hidden])
Date: 2011-03-16 16:09:29

On 3/16/2011 3:23 PM, pavel novikov wrote:
> i'm excited to present you a technique which i occasionally invented
> shared pointers are very good helpers
> they help us to manage dynamically allocated memory
> however it seems so natural i have never seen so far that one be
> allowed to delete shared pointer
> like this:
>
>    shared_ptr<int>
>      p = new int,
>      q = p;
>    delete p;
>    assert(!p);   //neither assertion fires
>    assert(q);
>
> in fact the technique is rather trivial
> provide a distinct class like this:
>
>    template<typename type>
>    struct deleter : shared_ptr_base<type>
>    {
>      void operator delete(void *p)
>      { reinterpret_cast<ptr_base*>(p)->detach(); }
>    };
>
> and let the 'operator unspecified_type_convertible_to_bool()' return
> statically casted address of the ptr instance itself (or NULL) like
> this:
>
>    template<typename type>  inline
>    shared_ptr<type>::operator const deleter<type>*() const
>    {
>      if (!data)
>        return 0;
>      const shared_ptr_base<type>  *base = this;
>      return static_cast<const safe_deleter<type>*>(base);  //oops! a little hack...
>    }
>
> minimum changes are needed to the existing library sources
> this way the example above works perfectly
>
> codepad.org is down so i just attached a toy programm with an
> implementation of this technique (works at least in msvc10)
>
>
>
>
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Maybe I'm missing something but how is "delete p;" different from 
"p.reset();" ?