Re: [committed] libstdc++: Specialize std::pointer_traits<__normal_iterator<I,C>>

["François Dumont" <frs.dumont@gmail.com>]

On 04/10/21 10:05 pm, François Dumont wrote:
> On 02/10/21 10:24 pm, Jonathan Wakely wrote:
>> On Sat, 2 Oct 2021 at 18:27, François Dumont wrote:
>>> I would like to propose this alternative approach.
>>>
>>> In this patch I make __normal_iterator and random iterator
>>> _Safe_iterator compatible for pointer_traits primary template.
>>>
>>> Regarding pointer_traits I wonder if it shouldn't check for the
>>> to_pointer method availability and use per default: return {
>>> std::addressof(__e) }; otherwise. This way we wouldn't have to 
>>> provide a
>>> pointer_to method on __normal_iterator.
>> But I would rather not have these members present in vector::iterator
>> and string::iterator, in case users accidentally start to rely on them
>> being present.
>
> Making pointer_traits friends would help but I do not like it neither.
>
>
>>
>> Another option would be to overload std::__to_address so it knows how
>> to get the address from __normal_iterator and _Safe_iterator.
>>
>> .
>
> I start thinking that rather than proposing not-useful and even 
> incorrect code in the case of the _Safe_iterator<> it might be a 
> better approach.
>
> Even the rebind for __normal_iterator is a little strange because when 
> doing rebind on std::vector<int>::iterator for long it produces 
> __normal_iterator<long*, std::vector<int>>, quite inconsistent even if 
> useless.
>
> But there's something that I'm missing, what is the relation between 
> __addressof and std::pointer_traits ? Is it that __builtin_addressof 
> is using it ?
>
Ignore this last question, I realized that we are talking about 
__to_address, not __addressof.