Re: auto_ptr who is right?

From:

Barry <dhb2000@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 06 Sep 2007 09:38:06 +0800

Message-ID:

<fbnllv$jek$1@aioe.org>

Tobias wrote:

8<
template<class _Ty>
    struct auto_ptr_ref
        { // proxy reference for auto_ptr copying
    auto_ptr_ref(void *_Right)
        : _Ref(_Right)
        { // construct from generic pointer to auto_ptr ptr
        }

    void *_Ref; // generic pointer to auto_ptr ptr
    };

Outch! After some test of object-compatibility the object pointer is
reduced to a void* pointer for later usage. This only works if the
vtable is quite simple. If I'm not mistaken the start of the vtable of
the base class must be equal to the start of the vtable of the derived
class. That is not always the case as we have seen in the example.

well, it's a mayor bug also inside auto_ptr implementation in MSVC8
the void* is already changed into Ty* in the VC9 beta. It's seems all
the cases here works fine with it.

anyway, it still uses auto_ptr_ref conversion in your case other than
template<class Y> auto_ptr& operator=(auto_ptr<Y>&) throw();

it's painful using auto_ptr at least with MSVC, while I felt that I'm
defending it.
It's deprecated in the working draft, said that it will be replaced by
unique_ptr, which borrows the new `Move' syntex. Still a long time to wait.

--
Thanks
Barry