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

From: Larry Evans (jcampbell3_at_[hidden])
Date: 2002-09-03 14:08:54

Philippe A. Bouchard wrote:
[snip]

>What about implementing some exception when get_count() == 2.  Given:
>
There could be 2 placed_ptr's on stack pointing to the same referent.

>bool is_on_data(void * p); // Confirm p is address on data segment
>bool is_on_stack(void * p); // Confirm p is address on stack segment
>bool is_on_heap(void * p); // Confirm p is address on heap segment
>
The above would be os dependent. I don't think that's much of a problem 
since
all the conservative methods used os dependent methods to delimit the 
stack and
data segments. I'm guessing that a data segment is where static data is 
stored?

>
>struct placed_ptr_header
>{
>        int m_count;
>        void * m_owner;  // Could point to stacked candidate for destruction
>};
>
>placed_ptr<T>::placed_ptr(...)
>{
>        if (is_on_stack(this))
>
should ^ also have "|| is_on_data(this)"?

>        {
>                get_owner() = this;
>        }
>        ...
>}
>
>placed_ptr<T>::~placed_ptr()
>{
>        if (m_ptr)
>        {
>                -- get_count();
>
>                if (get_count() == 0)
>                {
>                        m_ptr->~T();
>                        free(m_ptr - ...);
>                }
>                else if (get_count() == 1 && get_owner() == this)
>
What if remainng placed_ptr is ALSO on stack?