[gcc r12-568] libstdc++: Implement LWG 3391 changes to move/counted_iterator::base()
Patrick Palka
ppalka@gcc.gnu.org
Thu May 6 13:12:35 GMT 2021
https://gcc.gnu.org/g:08f3287eefea1d7c244db795d018870e8148d1c8
commit r12-568-g08f3287eefea1d7c244db795d018870e8148d1c8
Author: Patrick Palka <ppalka@redhat.com>
Date: Thu May 6 09:11:42 2021 -0400
libstdc++: Implement LWG 3391 changes to move/counted_iterator::base()
libstdc++-v3/ChangeLog:
* include/bits/stl_iterator.h (move_iterator::base): Make the
const& overload unconstrained and return a const reference as
per LWG 3391. Make unconditionally noexcept.
(counted_iterator::base): Likewise.
* testsuite/24_iterators/move_iterator/lwg3391.cc: New test.
* testsuite/24_iterators/move_iterator/move_only.cc: Adjust
has_member_base concept to decay-copy the result of base().
Diff:
---
libstdc++-v3/include/bits/stl_iterator.h | 13 +++-----
.../24_iterators/move_iterator/lwg3391.cc | 37 ++++++++++++++++++++++
.../24_iterators/move_iterator/move_only.cc | 8 ++++-
3 files changed, 48 insertions(+), 10 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 049f83cff90..2409cd71f86 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -1409,11 +1409,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
base() const
{ return _M_current; }
#else
- constexpr iterator_type
- base() const &
-#if __cpp_lib_concepts
- requires copy_constructible<iterator_type>
-#endif
+ constexpr const iterator_type&
+ base() const & noexcept
{ return _M_current; }
constexpr iterator_type
@@ -2141,10 +2138,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return *this;
}
- constexpr _It
- base() const &
- noexcept(is_nothrow_copy_constructible_v<_It>)
- requires copy_constructible<_It>
+ constexpr const _It&
+ base() const & noexcept
{ return _M_current; }
constexpr _It
diff --git a/libstdc++-v3/testsuite/24_iterators/move_iterator/lwg3391.cc b/libstdc++-v3/testsuite/24_iterators/move_iterator/lwg3391.cc
new file mode 100644
index 00000000000..18e015777cd
--- /dev/null
+++ b/libstdc++-v3/testsuite/24_iterators/move_iterator/lwg3391.cc
@@ -0,0 +1,37 @@
+// Copyright (C) 2021 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 } }
+
+// Verify LWG 3391 changes.
+
+#include <iterator>
+#include <ranges>
+
+#include <testsuite_iterators.h>
+
+using __gnu_test::test_range;
+using __gnu_test::input_iterator_wrapper_nocopy;
+
+void
+test01()
+{
+ extern test_range<int, input_iterator_wrapper_nocopy> rx;
+ auto v = rx | std::views::take(5);
+ std::ranges::begin(v) != std::ranges::end(v);
+}
diff --git a/libstdc++-v3/testsuite/24_iterators/move_iterator/move_only.cc b/libstdc++-v3/testsuite/24_iterators/move_iterator/move_only.cc
index 639adfab0e2..5537dfbf3cd 100644
--- a/libstdc++-v3/testsuite/24_iterators/move_iterator/move_only.cc
+++ b/libstdc++-v3/testsuite/24_iterators/move_iterator/move_only.cc
@@ -43,7 +43,13 @@ template<> struct std::iterator_traits<move_only_iterator>
static_assert(std::input_iterator<move_only_iterator>);
template<typename T>
- concept has_member_base = requires (T t) { std::forward<T>(t).base(); };
+ concept has_member_base = requires (T t) {
+ // LWG 3391 made the const& overload of move_iterator::base()
+ // unconstrained and return a const reference. So rather than checking
+ // whether base() is valid (which is now trivially true in an unevaluated
+ // context), the below now checks whether decay-copying base() is valid.
+ [](auto){}(std::forward<T>(t).base());
+ };
using move_only_move_iterator = std::move_iterator<move_only_iterator>;
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