I noticed that the following changes from this paper were not yet
implemented.
OK to commit after testing on x86_64-pc-linux-gnu finishes successfully?
libstdc++-v3/ChangeLog:
* include/bits/stl_iterator.h (reverse_iterator::iter_move):
Define for C++20 as per P0896.
(reverse_iterator::iter_swap): Likewise.
(move_iterator::operator*): Apply P0896 changes for C++20.
(move_iterator::operator[]): Likewise.
* testsuite/24_iterators/reverse_iterator/cust.cc: New test.
---
libstdc++-v3/include/bits/stl_iterator.h | 33 ++++++++++++
.../24_iterators/reverse_iterator/cust.cc | 51 +++++++++++++++++++
2 files changed, 84 insertions(+)
create mode 100644 libstdc++-v3/testsuite/24_iterators/reverse_iterator/cust.cc
diff --git a/libstdc++-v3/include/bits/stl_iterator.h
b/libstdc++-v3/include/bits/stl_iterator.h
index f29bae92706..ca3c4cda329 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -362,6 +362,31 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
operator[](difference_type __n) const
{ return *(*this + __n); }
+#if __cplusplus > 201703L && __cpp_lib_concepts
+ friend constexpr iter_rvalue_reference_t<_Iterator>
+ iter_move(const reverse_iterator& __i)
+ noexcept(is_nothrow_copy_constructible_v<_Iterator>
+ && noexcept(ranges::iter_move(--declval<_Iterator&>())))
+ {
+ auto __tmp = __i.base();
+ return ranges::iter_move(--__tmp);
+ }
+
+ template<indirectly_swappable<_Iterator> _Iter2>
+ friend constexpr void
+ iter_swap(const reverse_iterator& __x,
+ const reverse_iterator<_Iter2>& __y)
+ noexcept(is_nothrow_copy_constructible_v<_Iterator>
+ && is_nothrow_copy_constructible_v<_Iter2>
+ && noexcept(ranges::iter_swap(--declval<_Iterator&>(),
+ --declval<_Iter2&>())))
+ {
+ auto __xtmp = __x.base();
+ auto __ytmp = __y.base();
+ ranges::iter_swap(--__xtmp, --__ytmp);
+ }
+#endif
+
private:
template<typename _Tp>
static _GLIBCXX17_CONSTEXPR _Tp*
@@ -1379,7 +1404,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX17_CONSTEXPR reference
operator*() const
+#if __cplusplus > 201703L && __cpp_lib_concepts
+ { return ranges::iter_move(_M_current); }
+#else
{ return static_cast<reference>(*_M_current); }
+#endif
_GLIBCXX17_CONSTEXPR pointer
operator->() const
@@ -1445,7 +1474,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX17_CONSTEXPR reference
operator[](difference_type __n) const
+#if __cplusplus > 201703L && __cpp_lib_concepts
+ { return ranges::iter_move(_M_current + __n); }
+#else
{ return std::move(_M_current[__n]); }
+#endif
#if __cplusplus > 201703L && __cpp_lib_concepts
template<sentinel_for<_Iterator> _Sent>
diff --git a/libstdc++-v3/testsuite/24_iterators/reverse_iterator/cust.cc
b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/cust.cc
new file mode 100644
index 00000000000..3476780e34c
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/reverse_iterator/cust.cc
@@ -0,0 +1,51 @@
+// Copyright (C) 2019-2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <iterator>
+#include <testsuite_hooks.h>
+
+// This test is an adaption of 24_iterators/move_iterator/cust.cc.
+
+constexpr bool
+test01()
+{
+ struct X
+ {
+ constexpr X(int i) noexcept : i(i) { }
+ constexpr X(X&& x) noexcept : i(x.i) { x.i = -1; }
+ constexpr X& operator=(X&& x) noexcept { i = x.i; x.i = 0; return *this; }
+ int i;
+ };
+
+ X arr[] = { 1, 2 };
+ std::reverse_iterator<X*> i(arr + 1), j(arr + 2);
+ static_assert(noexcept(std::ranges::iter_swap(i, j)));
+ std::ranges::iter_swap(i, j);
+ VERIFY( arr[0].i == 2 );
+ VERIFY( arr[1].i == 1 );
+
+ static_assert(noexcept(std::ranges::iter_move(i)));
+ X x = std::ranges::iter_move(i);
+ VERIFY( arr[0].i == -1 );
+ VERIFY( x.i == 2 );
+ return true;
+}
+
+static_assert(test01());
--
2.28.0.651.g306ee63a70
