[libcxx-commits] [libcxx] [libc++] Speed up classic locale (PR #72112)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___UTILITY_NO_DESTROY_H
+#define _LIBCPP___UTILITY_NO_DESTROY_H
+
+#include <__config>
+#include <__utility/forward.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct __uninitialized_tag {};
+struct __zero_initialized_tag {};
+
+// This class stores an object of type T but never destroys it.
+//
+// This is akin to using __attribute__((no_destroy)), except that it is possible
+// to control the lifetime of the object with more flexibility by deciding e.g.
+// whether to initialize the object at construction or to defer to a later
+// initialization using __emplace.
+template <class _Tp>
+struct __no_destroy {
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ldionne wrote:

`launder` is also unnecessary now that we don't do type punning at all.

https://github.com/llvm/llvm-project/pull/72112