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  // 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 (__builtin_expect(__n > this->_M_max_size(), false))
112  {
113  // _GLIBCXX_RESOLVE_LIB_DEFECTS
114  // 3190. allocator::allocate sometimes returns too little storage
115  if (__n > (std::size_t(-1) / sizeof(_Tp)))
116  std::__throw_bad_array_new_length();
117  std::__throw_bad_alloc();
118  }
119 
120 #if __cpp_aligned_new
121  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
122  {
123  std::align_val_t __al = std::align_val_t(alignof(_Tp));
124  return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), __al));
125  }
126 #endif
127  return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
128  }
129 
130  // __p is not permitted to be a null pointer.
131  void
132  deallocate(_Tp* __p, size_type __t __attribute__ ((__unused__)))
133  {
134 #if __cpp_aligned_new
135  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
136  {
137  ::operator delete(__p,
138 # if __cpp_sized_deallocation
139  __t * sizeof(_Tp),
140 # endif
141  std::align_val_t(alignof(_Tp)));
142  return;
143  }
144 #endif
145  ::operator delete(__p
146 #if __cpp_sized_deallocation
147  , __t * sizeof(_Tp)
148 #endif
149  );
150  }
151 
152 #if __cplusplus <= 201703L
153  size_type
154  max_size() const _GLIBCXX_USE_NOEXCEPT
155  { return _M_max_size(); }
156 
157 #if __cplusplus >= 201103L
158  template<typename _Up, typename... _Args>
159  void
160  construct(_Up* __p, _Args&&... __args)
162  { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
163 
164  template<typename _Up>
165  void
166  destroy(_Up* __p)
168  { __p->~_Up(); }
169 #else
170  // _GLIBCXX_RESOLVE_LIB_DEFECTS
171  // 402. wrong new expression in [some_] allocator::construct
172  void
173  construct(pointer __p, const _Tp& __val)
174  { ::new((void *)__p) _Tp(__val); }
175 
176  void
177  destroy(pointer __p) { __p->~_Tp(); }
178 #endif
179 #endif // ! C++20
180 
181  template<typename _Up>
182  friend _GLIBCXX20_CONSTEXPR bool
183  operator==(const new_allocator&, const new_allocator<_Up>&)
184  _GLIBCXX_NOTHROW
185  { return true; }
186 
187 #if __cpp_impl_three_way_comparison < 201907L
188  template<typename _Up>
189  friend _GLIBCXX20_CONSTEXPR bool
190  operator!=(const new_allocator&, const new_allocator<_Up>&)
191  _GLIBCXX_NOTHROW
192  { return false; }
193 #endif
194 
195  private:
196  _GLIBCXX_CONSTEXPR size_type
197  _M_max_size() const _GLIBCXX_USE_NOEXCEPT
198  {
199 #if __PTRDIFF_MAX__ < __SIZE_MAX__
200  return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
201 #else
202  return std::size_t(-1) / sizeof(_Tp);
203 #endif
204  }
205  };
206 
207 _GLIBCXX_END_NAMESPACE_VERSION
208 } // namespace
209 
210 #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:66
is_nothrow_destructible
Definition: type_traits:938
is_nothrow_constructible
Definition: type_traits:1024
An allocator that uses global new, as per C++03 [20.4.1].
Definition: new_allocator.h:56