[boost] Re: Re: cyclic ptr (was: Re: Re: Re: Re: Re: Re: Re: Proposals: p2m offsets, prebuild<>, squad_ptr<> (of course))

From: Philippe A. Bouchard (philippeb_at_[hidden])
Date: 2002-09-05 10:21:50

Larry Evans wrote:

> Philippe A. Bouchard wrote:
> 
>>  
>>
>>I'll start by adding a "forced" destruction member.  It will decrement the
>>pointer, followed by a self-destruct placed_ptr call.  This way at least
>>the programmer will be able to free his own cyclic container.
>>
>>... or maybe operator delete could be displaced for placed_ptr<> or other
>>rc pointer types.  What do you think?
>>
> I don't understand.  Could you provide examples?

operator delete will not work (too bad for cleanliness) but we could add 
the following (dummy example):

void placed_ptr<T>::force_reset(element_type * a_p = 0)
{
        if (m_ptr)
        {
                get_count() = -1;       // -1 for cyclic pointer prevention
                get()->~T();            // This will eventually delete the cyclic pointer
                ::free(m_ptr - ...);
        }

        m_ptr = a_p;
}

void placed_ptr<T>::reset(element_type * a_p = 0)
{
        if (m_ptr && (get_count() != -1 && ! -- get_count()))
        {
                get()->~T();            // This will eventually delete the cyclic pointer
                ::free(m_ptr - ...);
        }

        m_ptr = a_p;
}

-- 
Philippe A. Bouchard