libstdc++
new_allocator.h
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1 // Allocator that wraps operator new -*- C++ -*-
2 
3 // Copyright (C) 2001-2021 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 
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>
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
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 #if __has_builtin(__builtin_operator_new) >= 201802L
101 # define _GLIBCXX_OPERATOR_NEW __builtin_operator_new
102 # define _GLIBCXX_OPERATOR_DELETE __builtin_operator_delete
103 #else
104 # define _GLIBCXX_OPERATOR_NEW ::operator new
105 # define _GLIBCXX_OPERATOR_DELETE ::operator delete
106 #endif
107 
108  // NB: __n is permitted to be 0. The C++ standard says nothing
109  // about what the return value is when __n == 0.
110  _GLIBCXX_NODISCARD _Tp*
111  allocate(size_type __n, const void* = static_cast<const void*>(0))
112  {
113 #if __cplusplus >= 201103L
114  // _GLIBCXX_RESOLVE_LIB_DEFECTS
115  // 3308. std::allocator<void>().allocate(n)
116  static_assert(sizeof(_Tp) != 0, "cannot allocate incomplete types");
117 #endif
118 
119  if (__builtin_expect(__n > this->_M_max_size(), false))
120  {
121  // _GLIBCXX_RESOLVE_LIB_DEFECTS
122  // 3190. allocator::allocate sometimes returns too little storage
123  if (__n > (std::size_t(-1) / sizeof(_Tp)))
124  std::__throw_bad_array_new_length();
125  std::__throw_bad_alloc();
126  }
127 
128 #if __cpp_aligned_new
129  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
130  {
131  std::align_val_t __al = std::align_val_t(alignof(_Tp));
132  return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp),
133  __al));
134  }
135 #endif
136  return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n * sizeof(_Tp)));
137  }
138 
139  // __p is not permitted to be a null pointer.
140  void
141  deallocate(_Tp* __p, size_type __n __attribute__ ((__unused__)))
142  {
143 #if __cpp_sized_deallocation
144 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p), (n) * sizeof(_Tp)
145 #else
146 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
147 #endif
148 
149 #if __cpp_aligned_new
150  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
151  {
152  _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),
153  std::align_val_t(alignof(_Tp)));
154  return;
155  }
156 #endif
157  _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n));
158  }
159 
160 #undef _GLIBCXX_SIZED_DEALLOC
161 #undef _GLIBCXX_OPERATOR_DELETE
162 #undef _GLIBCXX_OPERATOR_NEW
163 
164 #if __cplusplus <= 201703L
165  size_type
166  max_size() const _GLIBCXX_USE_NOEXCEPT
167  { return _M_max_size(); }
168 
169 #if __cplusplus >= 201103L
170  template<typename _Up, typename... _Args>
171  void
172  construct(_Up* __p, _Args&&... __args)
174  { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
175 
176  template<typename _Up>
177  void
178  destroy(_Up* __p)
180  { __p->~_Up(); }
181 #else
182  // _GLIBCXX_RESOLVE_LIB_DEFECTS
183  // 402. wrong new expression in [some_] allocator::construct
184  void
185  construct(pointer __p, const _Tp& __val)
186  { ::new((void *)__p) _Tp(__val); }
187 
188  void
189  destroy(pointer __p) { __p->~_Tp(); }
190 #endif
191 #endif // ! C++20
192 
193  template<typename _Up>
194  friend _GLIBCXX20_CONSTEXPR bool
195  operator==(const new_allocator&, const new_allocator<_Up>&)
196  _GLIBCXX_NOTHROW
197  { return true; }
198 
199 #if __cpp_impl_three_way_comparison < 201907L
200  template<typename _Up>
201  friend _GLIBCXX20_CONSTEXPR bool
202  operator!=(const new_allocator&, const new_allocator<_Up>&)
203  _GLIBCXX_NOTHROW
204  { return false; }
205 #endif
206 
207  private:
208  _GLIBCXX_CONSTEXPR size_type
209  _M_max_size() const _GLIBCXX_USE_NOEXCEPT
210  {
211 #if __PTRDIFF_MAX__ < __SIZE_MAX__
212  return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
213 #else
214  return std::size_t(-1) / sizeof(_Tp);
215 #endif
216  }
217  };
218 
219 _GLIBCXX_END_NAMESPACE_VERSION
220 } // namespace
221 
222 #endif
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
GNU extensions for public use.
integral_constant
Definition: type_traits:63
is_nothrow_destructible
Definition: type_traits:963
is_nothrow_constructible
Definition: type_traits:1049
An allocator that uses global new, as per C++03 [20.4.1].
Definition: new_allocator.h:56