From 7f65f94917866c6b18d9698eec6451c1bf21e0f9 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Sun, 13 Oct 2024 22:28:16 +0100
Subject: [PATCH] libstdc++: Implement LWG 3798 for range adaptors [PR106676]
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.
Reviewed-by: Patrick Palka <ppalka@redhat.com>
---
libstdc++-v3/include/bits/iterator_concepts.h | 4 +++-
libstdc++-v3/include/std/ranges | 18 +++++++++++++-----
.../testsuite/std/ranges/adaptors/transform.cc | 16 ++++++++++++++++
3 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/libstdc++-v3/include/bits/iterator_concepts.h b/libstdc++-v3/include/bits/iterator_concepts.h
index 490a362cdf1c..669d3ddfd1ec 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 98442dcfbd51..5b4558885363 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1892,7 +1892,9 @@ namespace views::__adaptor
using _Base = transform_view::_Base<_Const>;
using _Res = invoke_result_t<__maybe_const_t<_Const, _Fp>&,
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{};
@@ -7228,8 +7234,10 @@ 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>,
- iter_reference_t<_PatternIter>>>)
+ // _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>>>)
return input_iterator_tag{};
else if constexpr (derived_from<_OuterCat, bidirectional_iterator_tag>
&& derived_from<_InnerCat, bidirectional_iterator_tag>
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
index ca695349650a..e1b74353e632 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();
}
--
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