libcxx/include/__cxx03/__memory/temp_value.h

   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 <__cxx03/__config>
  13 #include <__cxx03/__memory/addressof.h>
  14 #include <__cxx03/__memory/allocator_traits.h>
  15 #include <__cxx03/__type_traits/aligned_storage.h>
  16 #include <__cxx03/__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 {
  32     _Tp __v;
  33   };
  34 #endif
  35   _Alloc& __a;
  36
  37   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp* __addr() {
  38 #ifdef _LIBCPP_CXX03_LANG
  39     return reinterpret_cast<_Tp*>(std::addressof(__v));
  40 #else
  41     return std::addressof(__v);
  42 #endif
  43   }
  44
  45   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& get() { return *__addr(); }
  46
  47   template <class... _Args>
  48   _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _LIBCPP_CONSTEXPR_SINCE_CXX20 __temp_value(_Alloc& __alloc, _Args&&... __args)
  49       : __a(__alloc) {
  50     _Traits::construct(__a, __addr(), std::forward<_Args>(__args)...);
  51   }
  52
  53   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 ~__temp_value() { _Traits::destroy(__a, __addr()); }
  54 };
  55
  56 _LIBCPP_END_NAMESPACE_STD
  57
  58 #endif // _LIBCPP___MEMORY_TEMP_VALUE_H