On Tue, 15 Oct 2024 at 14:30, Patrick Palka <ppa...@redhat.com> wrote:
>
> 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
Ah yes, good catch. I'll fix and push, thanks.
>
> > 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
> >
> >
>
