On Mon, 14 Oct 2024, Jonathan Wakely wrote:
> Tested x86_64-linux.
>
> -- >8 --
>
> LWG 3798 modified the iterator_category of the iterator types for
> transform_view, join_with_view, zip_transform_view and
> adjacent_transform_view, to allow the iterator's reference type to be an
> rvalue reference.
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/106676
> * include/bits/iterator_concepts.h (__cpp17_fwd_iterator): Use
> is_reference instead of is_value_reference.
> rvalue references.
> * include/std/ranges (transform_view:__iter_cat::_S_iter_cat):
> Likewise.
> (zip_transform_view::__iter_cat::_S_iter_cat): Likewise.
> (adjacent_transform_view::__iter_cat::_S_iter_cat): Likewise.
> (join_with_view::__iter_cat::_S_iter_cat): Likewise.
> * testsuite/std/ranges/adaptors/transform.cc: Check
> iterator_category when the transformation function returns an
> rvalue reference type.
> ---
> libstdc++-v3/include/bits/iterator_concepts.h | 4 +++-
> libstdc++-v3/include/std/ranges | 16 ++++++++++++----
> .../testsuite/std/ranges/adaptors/transform.cc | 16 ++++++++++++++++
> 3 files changed, 31 insertions(+), 5 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/iterator_concepts.h
> b/libstdc++-v3/include/bits/iterator_concepts.h
> index 490a362cdf1..669d3ddfd1e 100644
> --- a/libstdc++-v3/include/bits/iterator_concepts.h
> +++ b/libstdc++-v3/include/bits/iterator_concepts.h
> @@ -333,10 +333,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> typename incrementable_traits<_Iter>::difference_type>;
> };
>
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 3798. Rvalue reference and iterator_category
> template<typename _Iter>
> concept __cpp17_fwd_iterator = __cpp17_input_iterator<_Iter>
> && constructible_from<_Iter>
> - && is_lvalue_reference_v<iter_reference_t<_Iter>>
> + && is_reference_v<iter_reference_t<_Iter>>
> && same_as<remove_cvref_t<iter_reference_t<_Iter>>,
> typename indirectly_readable_traits<_Iter>::value_type>
> && requires(_Iter __it)
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index f0d81cbea0c..941189d65c3 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -1892,7 +1892,9 @@ namespace views::__adaptor
> using _Fpc = __detail::__maybe_const_t<_Const, _Fp>;
> using _Base = transform_view::_Base<_Const>;
> using _Res = invoke_result_t<_Fpc&, range_reference_t<_Base>>;
> - if constexpr (is_lvalue_reference_v<_Res>)
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 3798. Rvalue reference and iterator_category
> + if constexpr (is_reference_v<_Res>)
> {
> using _Cat
> = typename
> iterator_traits<iterator_t<_Base>>::iterator_category;
> @@ -5047,7 +5049,9 @@ namespace views::__adaptor
> using __detail::__range_iter_cat;
> using _Res = invoke_result_t<__maybe_const_t<_Const, _Fp>&,
>
> range_reference_t<__maybe_const_t<_Const, _Vs>>...>;
> - if constexpr (!is_lvalue_reference_v<_Res>)
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 3798. Rvalue reference and iterator_category
> + if constexpr (!is_reference_v<_Res>)
> return input_iterator_tag{};
> else if constexpr ((derived_from<__range_iter_cat<_Vs, _Const>,
> random_access_iterator_tag> && ...))
> @@ -5820,7 +5824,9 @@ namespace views::__adaptor
> using _Res = invoke_result_t<__unarize<__maybe_const_t<_Const, _Fp>&,
> _Nm>,
> range_reference_t<_Base>>;
> using _Cat = typename
> iterator_traits<iterator_t<_Base>>::iterator_category;
> - if constexpr (!is_lvalue_reference_v<_Res>)
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 3798. Rvalue reference and iterator_category
> + if constexpr (!is_reference_v<_Res>)
> return input_iterator_tag{};
> else if constexpr (derived_from<_Cat, random_access_iterator_tag>)
> return random_access_iterator_tag{};
> @@ -7228,7 +7234,9 @@ namespace views::__adaptor
> using _OuterCat = typename
> iterator_traits<_OuterIter>::iterator_category;
> using _InnerCat = typename
> iterator_traits<_InnerIter>::iterator_category;
> using _PatternCat = typename
> iterator_traits<_PatternIter>::iterator_category;
> - if constexpr
> (!is_lvalue_reference_v<common_reference_t<iter_reference_t<_InnerIter>,
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 3798. Rvalue reference and iterator_category
> + if constexpr
> (!is_reference_v<common_reference_t<iter_reference_t<_InnerIter>,
>
> iter_reference_t<_PatternIter>>>)
This line is misaligned with the previous one now. LGTM besides that
> return input_iterator_tag{};
> else if constexpr (derived_from<_OuterCat, bidirectional_iterator_tag>
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> index ca695349650..e1b74353e63 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> @@ -214,6 +214,21 @@ test10()
> static_assert(std::same_as<cat, std::random_access_iterator_tag>);
> }
>
> +void
> +test11()
> +{
> + struct MoveIt {
> + int&& operator()(int& i) const { return std::move(i); }
> + };
> +
> + int x[] {2, 4};
> + auto xform = x | views::transform(MoveIt{});
> + using iterator = decltype(xform.begin());
> + // LWG 3798. Rvalue reference and iterator_category
> + using cat = std::iterator_traits<iterator>::iterator_category;
> + static_assert(std::same_as<cat, std::random_access_iterator_tag>);
> +}
> +
> int
> main()
> {
> @@ -227,4 +242,5 @@ main()
> test08();
> test09();
> test10();
> + test11();
> }
> --
> 2.46.2
>
>
