libstdc++: Enforce copyable/movable checks in std::atomic

C++20 adds some new preconditions to std::atomic, which weren't
previously checked by our implementation.

	* include/std/atomic (atomic): Add static assertions.
	* testsuite/29_atomics/atomic/requirements/types_neg.cc: New test.

2 files changed, 50 insertions, 0 deletions

diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index a455286..2161cbe 100644
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -198,6 +198,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       static_assert(sizeof(_Tp) > 0,
 		    "Incomplete or zero-sized types are not supported");
 
+#if __cplusplus > 201703L
+      static_assert(is_copy_constructible_v<_Tp>);
+      static_assert(is_move_constructible_v<_Tp>);
+      static_assert(is_copy_assignable_v<_Tp>);
+      static_assert(is_move_assignable_v<_Tp>);
+#endif
+
     public:
       atomic() = default;
       ~atomic() noexcept = default;
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/requirements/types_neg.cc b/libstdc++-v3/testsuite/29_atomics/atomic/requirements/types_neg.cc
new file mode 100644
index 0000000..4c58a9d
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/requirements/types_neg.cc
@@ -0,0 +1,43 @@
+// Copyright (C) 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 <atomic>
+
+std::atomic<const int> a; // { dg-error "here" }
+
+struct MoveOnly
+{
+  MoveOnly() = default;
+  MoveOnly(MoveOnly&&) = default;
+  MoveOnly& operator=(MoveOnly&&) = default;
+};
+std::atomic<MoveOnly> b; // { dg-error "here" }
+
+struct NoMove
+{
+  NoMove() = default;
+  NoMove(const NoMove&) = default;
+  NoMove& operator=(const NoMove&) = default;
+  NoMove(NoMove&&) = delete;
+  NoMove& operator=(NoMove&&) = delete;
+};
+std::atomic<NoMove> c; // { dg-error "here" }
+
+// { dg-error "static assertion failed" "" { target *-*-* } 0 }