[libcxx-commits] [libcxx] [libc++] atomic timed wait (PR #172214)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,100 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef _LIBCPP___ATOMIC_ATOMIC_WAITABLE_TRAITS_H
+#define _LIBCPP___ATOMIC_ATOMIC_WAITABLE_TRAITS_H
+
+#include <__atomic/contention_t.h>
+#include <__atomic/memory_order.h>
+#include <__config>
+#include <__type_traits/decay.h>
+#include <__type_traits/has_unique_object_representation.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/is_trivially_copyable.h>
+#include <__type_traits/void_t.h>
+#include <__utility/declval.h>
+#include <cstring>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// The customisation points to enable the following functions:
+// - __atomic_wait
+// - __atomic_wait_unless
+// - __atomic_notify_one
+// - __atomic_notify_all
+// Note that std::atomic<T>::wait was back-ported to C++03
+// The below implementations look ugly to support C++03
+template <class _Tp, class = void>
+struct __atomic_waitable_traits {
+  using __value_type _LIBCPP_NODEBUG = void;
+
+  template <class _AtomicWaitable>
+  static void __atomic_load(_AtomicWaitable&&, memory_order) = delete;
+
+  template <class _AtomicWaitable>
+  static void __atomic_contention_address(_AtomicWaitable&&) = delete;
+};
+
+template <class _Tp, class = void>
+struct __atomic_waitable : false_type {};
+
+template <class _Tp>
+struct __atomic_waitable< _Tp,
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ldionne wrote:

I like splitting these traits into their own header regardless of whether we move forward with the rest of this change. How about we do this as a refactoring PR prior to this patch?

https://github.com/llvm/llvm-project/pull/172214