libstdc++
malloc_allocator.h
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1 // Allocator that wraps "C" malloc -*- 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/malloc_allocator.h
26  * This file is a GNU extension to the Standard C++ Library.
27  */
28 
29 #ifndef _MALLOC_ALLOCATOR_H
30 #define _MALLOC_ALLOCATOR_H 1
31 
32 #include <cstdlib>
33 #include <cstddef>
34 #include <new>
35 #include <bits/functexcept.h>
36 #include <bits/move.h>
37 #if __cplusplus >= 201103L
38 #include <type_traits>
39 #endif
40 
41 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
42 {
43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
44 
45  /**
46  * @brief An allocator that uses malloc.
47  * @ingroup allocators
48  *
49  * This is precisely the allocator defined in the C++ Standard.
50  * - all allocation calls malloc
51  * - all deallocation calls free
52  */
53  template<typename _Tp>
55  {
56  public:
57  typedef _Tp value_type;
58  typedef std::size_t size_type;
59  typedef std::ptrdiff_t difference_type;
60 #if __cplusplus <= 201703L
61  typedef _Tp* pointer;
62  typedef const _Tp* const_pointer;
63  typedef _Tp& reference;
64  typedef const _Tp& const_reference;
65 
66  template<typename _Tp1>
67  struct rebind
68  { typedef malloc_allocator<_Tp1> other; };
69 #endif
70 
71 #if __cplusplus >= 201103L
72  // _GLIBCXX_RESOLVE_LIB_DEFECTS
73  // 2103. propagate_on_container_move_assignment
75 #endif
76 
77  _GLIBCXX20_CONSTEXPR
78  malloc_allocator() _GLIBCXX_USE_NOEXCEPT { }
79 
80  _GLIBCXX20_CONSTEXPR
81  malloc_allocator(const malloc_allocator&) _GLIBCXX_USE_NOEXCEPT { }
82 
83  template<typename _Tp1>
84  _GLIBCXX20_CONSTEXPR
86  _GLIBCXX_USE_NOEXCEPT { }
87 
88 #if __cplusplus <= 201703L
89  ~malloc_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  _Tp*
103  allocate(size_type __n, const void* = 0)
104  {
105  if (__n > this->_M_max_size())
106  std::__throw_bad_alloc();
107 
108  _Tp* __ret = 0;
109 #if __cpp_aligned_new
110 #if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
111  if (alignof(_Tp) > alignof(std::max_align_t))
112  {
113  __ret = static_cast<_Tp*>(::aligned_alloc(alignof(_Tp),
114  __n * sizeof(_Tp)));
115  }
116 #else
117 # define _GLIBCXX_CHECK_MALLOC_RESULT
118 #endif
119 #endif
120  if (!__ret)
121  __ret = static_cast<_Tp*>(std::malloc(__n * sizeof(_Tp)));
122  if (!__ret)
123  std::__throw_bad_alloc();
124 #ifdef _GLIBCXX_CHECK_MALLOC_RESULT
125 #undef _GLIBCXX_CHECK_MALLOC_RESULT
126  if (reinterpret_cast<std::size_t>(__ret) % alignof(_Tp))
127  {
128  // Memory returned by malloc is not suitably aligned for _Tp.
129  deallocate(__ret, __n);
130  std::__throw_bad_alloc();
131  }
132 #endif
133  return __ret;
134  }
135 
136  // __p is not permitted to be a null pointer.
137  void
138  deallocate(_Tp* __p, size_type)
139  { std::free(static_cast<void*>(__p)); }
140 
141 #if __cplusplus <= 201703L
142  size_type
143  max_size() const _GLIBCXX_USE_NOEXCEPT
144  { return _M_max_size(); }
145 
146 #if __cplusplus >= 201103L
147  template<typename _Up, typename... _Args>
148  void
149  construct(_Up* __p, _Args&&... __args)
151  { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
152 
153  template<typename _Up>
154  void
155  destroy(_Up* __p)
157  { __p->~_Up(); }
158 #else
159  // _GLIBCXX_RESOLVE_LIB_DEFECTS
160  // 402. wrong new expression in [some_] allocator::construct
161  void
162  construct(pointer __p, const _Tp& __val)
163  { ::new((void *)__p) value_type(__val); }
164 
165  void
166  destroy(pointer __p) { __p->~_Tp(); }
167 #endif
168 #endif // ! C++20
169 
170  template<typename _Up>
171  friend _GLIBCXX20_CONSTEXPR bool
172  operator==(const malloc_allocator&, const malloc_allocator<_Up>&)
173  _GLIBCXX_NOTHROW
174  { return true; }
175 
176 #if __cpp_impl_three_way_comparison < 201907L
177  template<typename _Up>
178  friend _GLIBCXX20_CONSTEXPR bool
179  operator!=(const malloc_allocator&, const malloc_allocator<_Up>&)
180  _GLIBCXX_NOTHROW
181  { return false; }
182 #endif
183 
184  private:
185  _GLIBCXX_CONSTEXPR size_type
186  _M_max_size() const _GLIBCXX_USE_NOEXCEPT
187  {
188 #if __PTRDIFF_MAX__ < __SIZE_MAX__
189  return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
190 #else
191  return std::size_t(-1) / sizeof(_Tp);
192 #endif
193  }
194  };
195 
196 _GLIBCXX_END_NAMESPACE_VERSION
197 } // namespace
198 
199 #endif
is_nothrow_destructible
Definition: type_traits:892
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
integral_constant
Definition: type_traits:57
is_nothrow_constructible
Definition: type_traits:1008
An allocator that uses malloc.This is precisely the allocator defined in the C++ Standard.