Re: [PATCH] libstdc++: Fix up implementation of LWG 3533 [PR101589]

[Jonathan Wakely <jwakely@redhat.com>]

On Fri, 23 Jul 2021 at 17:35, Patrick Palka via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> In r12-569 I accidentally applied the LWG 3533 change that
> was intended for elements_view::iterator::base to
> elements_view::base instead.
>
> This patch corrects this, and also applies the corresponding LWG 3533
> change to lazy_split_view::inner-iter::base now that we implement P2210.
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk and release
> branches?

OK, thanks.


>
>         PR libstdc++/101589
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/ranges (lazy_split_view::_InnerIter::base): Make
>         the const& overload unconstrained and return a const reference
>         as per LWG 3533.  Make unconditionally noexcept.
>         (elements_view::base): Revert accidental r12-569 change.
>         (elements_view::_Iterator::base): Make the const& overload
>         unconstrained and return a const reference as per LWG 3533.
>         Make unconditionally noexcept.
> ---
>  libstdc++-v3/include/std/ranges | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index d791e15d096..50b414e8c8c 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -3103,8 +3103,8 @@ namespace views::__adaptor
>             : _M_i(std::move(__i))
>           { }
>
> -         constexpr iterator_t<_Base>
> -         base() const& requires copyable<iterator_t<_Base>>
> +         constexpr const iterator_t<_Base>&
> +         base() const& noexcept
>           { return _M_i_current(); }
>
>           constexpr iterator_t<_Base>
> @@ -3786,8 +3786,8 @@ namespace views::__adaptor
>         : _M_base(std::move(base))
>        { }
>
> -      constexpr const _Vp&
> -      base() const & noexcept
> +      constexpr _Vp
> +      base() const& requires copy_constructible<_Vp>
>        { return _M_base; }
>
>        constexpr _Vp
> @@ -3913,9 +3913,8 @@ namespace views::__adaptor
>             : _M_current(std::move(i._M_current))
>           { }
>
> -         constexpr iterator_t<_Base>
> -         base() const&
> -           requires copyable<iterator_t<_Base>>
> +         constexpr const iterator_t<_Base>&
> +         base() const& noexcept
>           { return _M_current; }
>
>           constexpr iterator_t<_Base>
> --
> 2.32.0.349.gdaab8a564f
>