[boost] Re: move_ptr

From: Jonathan Turkanis (technews_at_[hidden])
Date: 2004-01-21 13:08:36

"Larry Evans" <cppljevans_at_[hidden]> wrote in message
news:bumcp2$gqu$1_at_sea.gmane.org...
> On 01/21/2004 04:01 AM, Bronek Kozicki wrote:
>  > On Tue, 20 Jan 2004 22:05:33 -0500, Howard Hinnant wrote:
> [snip]
>  >
>  > Ahhh, clause 5.3.5/3 : "In the second alternative  (delete array)
if the
>  > dynamic type of the object to be deleted differs from its static
type,
>  > the behavior is undefined". Hm. I missed it [1].
>  >
>  > However I still think that my example (from
>  > http://b.kozicki.pl/cpp/T192.cpp ) :
>  > auto_ptr<Base> source6 ()
>  > {
>  >   printf("returning pointer to table\n");
>  >   return auto_ptr<Derived>(new Derived[3], del_array());
>  > }
>  >
>  > is valid. This is not really useful application of custom
deleter, but
>  > does not intruduce undefined behaviour, nor unexpected behaviour,
thus
>  > (being quite useless) it's still valid. Please note that deleter
will
>  > always receive static-type == dynamic-type, when used properly
(ie.
>  > smart pointer intialized directly with raw pointer).
> [snip]
>
> I BRIEFLY looked at T192.cpp and T191.hpp.  T191.hpp shows the
> auto_ptr contains 3 pointers:
>
>    typedef void (* _free_t_) (const volatile void *);
>
>    X* ptr_;
>    const volatile void* ptv_;
>    _free_t_ del_; // pointer to deleter function
>
> I believe, at the same memory cost and a restriction of the
"initial"
> CTOR arguments, auto_new (as the initial CTOR argument) with a 2
> template argument auto_ptr, can achieve the same results.  The
> auto_new I'm referring to is in:
>
>    http://groups.yahoo.com/group/boost/files/shared_cyclic_ptr/
>    auto_smart_ptr.zip
>

Hi Larry,
    I'm working on this issue right now, so I'd like to look at your
code. Unfortunately, I can't seem to download it from yaho. Could you
send me a zip?
   I am working on several versions which will eliminate one of the
pointers in Bronek's implementation. What exactly is the storage
overhead in your implementation?

Regards,
Jonathan