On 02/10/21 12:29 am, Jonathan Wakely wrote:
> On Thu, 30 Sept 2021 at 21:27, François Dumont via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
>> Here is the _Safe_iterator one.
>>
>> Doing so I noticed that pointer_traits rebind for __normal_iterator was
>> wrong and added tests on it.
> Oops, thanks!
>
>> For _Safe_iterator maybe I should specialize only when instantiated with
>> __normal_iterator ? Or maybe limit to random_access_iterator_tag ?
> Yes, I think that's a good idea, maybe only for __normal_iterator<T*,
> C>. I think that should cover all the cases we actually need to
> support.
>
> And could you change the existing pointer_traits<__normal_iterator<I,
> C>> partial specialization to only be valid for
> __normal_iterator<T*,C> as well? i.e. only for __normal_iterator that
> wraps a pointer (which is true for string::iterator, vector::iterator
> etc.)

Is the attached patch what you had in mind ?

At least it is passing tests.


>
>> Whatever the pointer_to implementation is problematic, we can only
>> produce singular iterator as I did ifor now.
> Hmm, yes. I think that's OK, because I don't think anybody is actually
> going to use that function. What matters is that it works with
> std::__to_address for C++17 mode, and that doesn't depend on
> pointer_to, so it's OK if it doesn't work usefully.
>
This is why I think that my patch of the unordered containers to support 
custom pointers is not so bad because it avoids usage of 
pointer_traits::to_pointer :-)