1 // Allocator that wraps operator new -*- C++ -*-
2
3 // Copyright (C) 2001-2020 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file ext/new_allocator.h
26 * This file is a GNU extension to the Standard C++ Library.
27 */
28
29 #ifndef _NEW_ALLOCATOR_H
30 #define _NEW_ALLOCATOR_H 1
31
32 #include <bits/c++config.h>
33 #include <new>
34 #include <bits/functexcept.h>
35 #include <bits/move.h>
36 #if __cplusplus >= 201103L
37 #include <type_traits>
38 #endif
39
_GLIBCXX_VISIBILITY(default)40 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43
44 /**
45 * @brief An allocator that uses global new, as per C++03 [20.4.1].
46 * @ingroup allocators
47 *
48 * This is precisely the allocator defined in the C++ Standard.
49 * - all allocation calls operator new
50 * - all deallocation calls operator delete
51 *
52 * @tparam _Tp Type of allocated object.
53 */
54 template<typename _Tp>
55 class new_allocator
56 {
57 public:
58 typedef _Tp value_type;
59 typedef std::size_t size_type;
60 typedef std::ptrdiff_t difference_type;
61 #if __cplusplus <= 201703L
62 typedef _Tp* pointer;
63 typedef const _Tp* const_pointer;
64 typedef _Tp& reference;
65 typedef const _Tp& const_reference;
66
67 template<typename _Tp1>
68 struct rebind
69 { typedef new_allocator<_Tp1> other; };
70 #endif
71
72 #if __cplusplus >= 201103L
73 // _GLIBCXX_RESOLVE_LIB_DEFECTS
74 // 2103. propagate_on_container_move_assignment
75 typedef std::true_type propagate_on_container_move_assignment;
76 #endif
77
78 _GLIBCXX20_CONSTEXPR
79 new_allocator() _GLIBCXX_USE_NOEXCEPT { }
80
81 _GLIBCXX20_CONSTEXPR
82 new_allocator(const new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
83
84 template<typename _Tp1>
85 _GLIBCXX20_CONSTEXPR
86 new_allocator(const new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
87
88 #if __cplusplus <= 201703L
89 ~new_allocator() _GLIBCXX_USE_NOEXCEPT { }
90
91 pointer
92 address(reference __x) const _GLIBCXX_NOEXCEPT
93 { return std::__addressof(__x); }
94
95 const_pointer
96 address(const_reference __x) const _GLIBCXX_NOEXCEPT
97 { return std::__addressof(__x); }
98 #endif
99
100 // NB: __n is permitted to be 0. The C++ standard says nothing
101 // about what the return value is when __n == 0.
102 _GLIBCXX_NODISCARD _Tp*
103 allocate(size_type __n, const void* = static_cast<const void*>(0))
104 {
105 #if __cplusplus >= 201103L
106 // _GLIBCXX_RESOLVE_LIB_DEFECTS
107 // 3308. std::allocator<void>().allocate(n)
108 static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
109 #endif
110
111 if (__n > this->_M_max_size())
112 std::__throw_bad_alloc();
113
114 #if __cpp_aligned_new
115 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
116 {
117 std::align_val_t __al = std::align_val_t(alignof(_Tp));
118 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al));
119 }
120 #endif
121 return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
122 }
123
124 // __p is not permitted to be a null pointer.
125 void
126 deallocate(_Tp* __p, size_type __t)
127 {
128 #if __cpp_aligned_new
129 if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
130 {
131 ::operator delete(__p,
132 # if __cpp_sized_deallocation
133 __t * sizeof(_Tp),
134 # endif
135 std::align_val_t(alignof(_Tp)));
136 return;
137 }
138 #endif
139 ::operator delete(__p
140 #if __cpp_sized_deallocation
141 , __t * sizeof(_Tp)
142 #endif
143 );
144 }
145
146 #if __cplusplus <= 201703L
147 size_type
148 max_size() const _GLIBCXX_USE_NOEXCEPT
149 { return _M_max_size(); }
150
151 #if __cplusplus >= 201103L
152 template<typename _Up, typename... _Args>
153 void
154 construct(_Up* __p, _Args&&... __args)
155 noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
156 { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
157
158 template<typename _Up>
159 void
160 destroy(_Up* __p)
161 noexcept(std::is_nothrow_destructible<_Up>::value)
162 { __p->~_Up(); }
163 #else
164 // _GLIBCXX_RESOLVE_LIB_DEFECTS
165 // 402. wrong new expression in [some_] allocator::construct
166 void
167 construct(pointer __p, const _Tp& __val)
168 { ::new((void *)__p) _Tp(__val); }
169
170 void
171 destroy(pointer __p) { __p->~_Tp(); }
172 #endif
173 #endif // ! C++20
174
175 template<typename _Up>
176 friend _GLIBCXX20_CONSTEXPR bool
177 operator==(const new_allocator&, const new_allocator<_Up>&)
178 _GLIBCXX_NOTHROW
179 { return true; }
180
181 #if __cpp_impl_three_way_comparison < 201907L
182 template<typename _Up>
183 friend _GLIBCXX20_CONSTEXPR bool
184 operator!=(const new_allocator&, const new_allocator<_Up>&)
185 _GLIBCXX_NOTHROW
186 { return false; }
187 #endif
188
189 private:
190 _GLIBCXX_CONSTEXPR size_type
191 _M_max_size() const _GLIBCXX_USE_NOEXCEPT
192 {
193 #if __PTRDIFF_MAX__ < __SIZE_MAX__
194 return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
195 #else
196 return std::size_t(-1) / sizeof(_Tp);
197 #endif
198 }
199 };
200
201 _GLIBCXX_END_NAMESPACE_VERSION
202 } // namespace
203
204 #endif
205