1// Allocator that wraps "C" malloc -*- C++ -*-
2
3// Copyright (C) 2001-2022 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
41namespace __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>
54    class malloc_allocator
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
74      typedef std::true_type 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
85        malloc_allocator(const malloc_allocator<_Tp1>&)
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      _GLIBCXX_NODISCARD _Tp*
103      allocate(size_type __n, 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	_Tp* __ret = 0;
121#if __cpp_aligned_new
122#if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
123	if (alignof(_Tp) > alignof(std::max_align_t))
124	  {
125	    __ret = static_cast<_Tp*>(::aligned_alloc(alignof(_Tp),
126						      __n * sizeof(_Tp)));
127	  }
128#else
129# define _GLIBCXX_CHECK_MALLOC_RESULT
130#endif
131#endif
132	if (!__ret)
133	  __ret = static_cast<_Tp*>(std::malloc(__n * sizeof(_Tp)));
134	if (!__ret)
135	  std::__throw_bad_alloc();
136#ifdef _GLIBCXX_CHECK_MALLOC_RESULT
137#undef _GLIBCXX_CHECK_MALLOC_RESULT
138	  if (reinterpret_cast<std::size_t>(__ret) % alignof(_Tp))
139	    {
140	      // Memory returned by malloc is not suitably aligned for _Tp.
141	      deallocate(__ret, __n);
142	      std::__throw_bad_alloc();
143	    }
144#endif
145	return __ret;
146      }
147
148      // __p is not permitted to be a null pointer.
149      void
150      deallocate(_Tp* __p, size_type)
151      { std::free(static_cast<void*>(__p)); }
152
153#if __cplusplus <= 201703L
154      size_type
155      max_size() const _GLIBCXX_USE_NOEXCEPT
156      { return _M_max_size(); }
157
158#if __cplusplus >= 201103L
159      template<typename _Up, typename... _Args>
160        void
161        construct(_Up* __p, _Args&&... __args)
162	noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
163	{ ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
164
165      template<typename _Up>
166        void
167        destroy(_Up* __p)
168	noexcept(std::is_nothrow_destructible<_Up>::value)
169	{ __p->~_Up(); }
170#else
171      // _GLIBCXX_RESOLVE_LIB_DEFECTS
172      // 402. wrong new expression in [some_] allocator::construct
173      void
174      construct(pointer __p, const _Tp& __val)
175      { ::new((void *)__p) value_type(__val); }
176
177      void
178      destroy(pointer __p) { __p->~_Tp(); }
179#endif
180#endif // ! C++20
181
182      template<typename _Up>
183	friend _GLIBCXX20_CONSTEXPR bool
184	operator==(const malloc_allocator&, const malloc_allocator<_Up>&)
185	_GLIBCXX_NOTHROW
186	{ return true; }
187
188#if __cpp_impl_three_way_comparison < 201907L
189      template<typename _Up>
190	friend _GLIBCXX20_CONSTEXPR bool
191	operator!=(const malloc_allocator&, const malloc_allocator<_Up>&)
192	_GLIBCXX_NOTHROW
193	{ return false; }
194#endif
195
196    private:
197      _GLIBCXX_CONSTEXPR size_type
198      _M_max_size() const _GLIBCXX_USE_NOEXCEPT
199      {
200#if __PTRDIFF_MAX__ < __SIZE_MAX__
201	return std::size_t(__PTRDIFF_MAX__) / sizeof(_Tp);
202#else
203	return std::size_t(-1) / sizeof(_Tp);
204#endif
205      }
206    };
207
208_GLIBCXX_END_NAMESPACE_VERSION
209} // namespace
210
211#endif
212