1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___MEMORY_TEMP_VALUE_H
10 #define _LIBCPP___MEMORY_TEMP_VALUE_H
11 
12 #include <__config>
13 #include <__memory/addressof.h>
14 #include <__memory/allocator_traits.h>
15 #include <__type_traits/aligned_storage.h>
16 #include <__utility/forward.h>
17 
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 #  pragma GCC system_header
20 #endif
21 
22 _LIBCPP_BEGIN_NAMESPACE_STD
23 
24 template <class _Tp, class _Alloc>
25 struct __temp_value {
26     typedef allocator_traits<_Alloc> _Traits;
27 
28 #ifdef _LIBCPP_CXX03_LANG
29     typename aligned_storage<sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)>::type __v;
30 #else
31     union { _Tp __v; };
32 #endif
33     _Alloc &__a;
34 
35     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp *__addr() {
36 #ifdef _LIBCPP_CXX03_LANG
37         return reinterpret_cast<_Tp*>(std::addressof(__v));
38 #else
39         return std::addressof(__v);
40 #endif
41     }
42 
43     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp & get() { return *__addr(); }
44 
45     template<class... _Args>
46     _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI
47     _LIBCPP_CONSTEXPR_SINCE_CXX20 __temp_value(_Alloc &__alloc, _Args&& ... __args) : __a(__alloc) {
48       _Traits::construct(__a, __addr(), std::forward<_Args>(__args)...);
49     }
50 
51     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__temp_value() { _Traits::destroy(__a, __addr()); }
52 };
53 
54 _LIBCPP_END_NAMESPACE_STD
55 
56 #endif // _LIBCPP___MEMORY_TEMP_VALUE_H
57