libcxx/include/__memory/allocator.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___MEMORY_ALLOCATOR_H
  11 #define _LIBCPP___MEMORY_ALLOCATOR_H
  12
  13 #include <__config>
  14 #include <__memory/addressof.h>
  15 #include <__memory/allocate_at_least.h>
  16 #include <__memory/allocator_traits.h>
  17 #include <__type_traits/is_constant_evaluated.h>
  18 #include <__type_traits/is_same.h>
  19 #include <__type_traits/is_void.h>
  20 #include <__type_traits/is_volatile.h>
  21 #include <__utility/forward.h>
  22 #include <cstddef>
  23 #include <new>
  24
  25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  26 #  pragma GCC system_header
  27 #endif
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 template <class _Tp> class allocator;
  32
  33 #if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_VOID_SPECIALIZATION)
  34 // These specializations shouldn't be marked _LIBCPP_DEPRECATED_IN_CXX17.
  35 // Specializing allocator<void> is deprecated, but not using it.
  36 template <>
  37 class _LIBCPP_TEMPLATE_VIS allocator<void>
  38 {
  39 #if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
  40 public:
  41     _LIBCPP_DEPRECATED_IN_CXX17 typedef void*             pointer;
  42     _LIBCPP_DEPRECATED_IN_CXX17 typedef const void*       const_pointer;
  43     _LIBCPP_DEPRECATED_IN_CXX17 typedef void              value_type;
  44
  45     template <class _Up> struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {typedef allocator<_Up> other;};
  46 #endif
  47 };
  48
  49 template <>
  50 class _LIBCPP_TEMPLATE_VIS allocator<const void>
  51 {
  52 #if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
  53 public:
  54     _LIBCPP_DEPRECATED_IN_CXX17 typedef const void*       pointer;
  55     _LIBCPP_DEPRECATED_IN_CXX17 typedef const void*       const_pointer;
  56     _LIBCPP_DEPRECATED_IN_CXX17 typedef const void        value_type;
  57
  58     template <class _Up> struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {typedef allocator<_Up> other;};
  59 #endif
  60 };
  61 #endif
  62
  63 // This class provides a non-trivial default constructor to the class that derives from it
  64 // if the condition is satisfied.
  65 //
  66 // The second template parameter exists to allow giving a unique type to __non_trivial_if,
  67 // which makes it possible to avoid breaking the ABI when making this a base class of an
  68 // existing class. Without that, imagine we have classes D1 and D2, both of which used to
  69 // have no base classes, but which now derive from __non_trivial_if. The layout of a class
  70 // that inherits from both D1 and D2 will change because the two __non_trivial_if base
  71 // classes are not allowed to share the same address.
  72 //
  73 // By making those __non_trivial_if base classes unique, we work around this problem and
  74 // it is safe to start deriving from __non_trivial_if in existing classes.
  75 template <bool _Cond, class _Unique>
  76 struct __non_trivial_if { };
  77
  78 template <class _Unique>
  79 struct __non_trivial_if<true, _Unique> {
  80     _LIBCPP_INLINE_VISIBILITY
  81     _LIBCPP_CONSTEXPR __non_trivial_if() _NOEXCEPT { }
  82 };
  83
  84 // allocator
  85 //
  86 // Note: For ABI compatibility between C++20 and previous standards, we make
  87 //       allocator<void> trivial in C++20.
  88
  89 template <class _Tp>
  90 class _LIBCPP_TEMPLATE_VIS allocator
  91     : private __non_trivial_if<!is_void<_Tp>::value, allocator<_Tp> >
  92 {
  93     static_assert(!is_volatile<_Tp>::value, "std::allocator does not support volatile types");
  94 public:
  95     typedef size_t      size_type;
  96     typedef ptrdiff_t   difference_type;
  97     typedef _Tp         value_type;
  98     typedef true_type   propagate_on_container_move_assignment;
  99     typedef true_type   is_always_equal;
 100
 101     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 allocator() _NOEXCEPT = default;
 102
 103     template <class _Up>
 104     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 105     allocator(const allocator<_Up>&) _NOEXCEPT { }
 106
 107     _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 108     _Tp* allocate(size_t __n) {
 109         if (__n > allocator_traits<allocator>::max_size(*this))
 110             __throw_bad_array_new_length();
 111         if (__libcpp_is_constant_evaluated()) {
 112             return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
 113         } else {
 114             return static_cast<_Tp*>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
 115         }
 116     }
 117
 118 #if _LIBCPP_STD_VER >= 23
 119     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr
 120     allocation_result<_Tp*> allocate_at_least(size_t __n) {
 121         return {allocate(__n), __n};
 122     }
 123 #endif
 124
 125     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 126     void deallocate(_Tp* __p, size_t __n) _NOEXCEPT {
 127         if (__libcpp_is_constant_evaluated()) {
 128             ::operator delete(__p);
 129         } else {
 130             _VSTD::__libcpp_deallocate((void*)__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
 131         }
 132     }
 133
 134     // C++20 Removed members
 135 #if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
 136     _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp*       pointer;
 137     _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* const_pointer;
 138     _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp&       reference;
 139     _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& const_reference;
 140
 141     template <class _Up>
 142     struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
 143         typedef allocator<_Up> other;
 144     };
 145
 146     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 147     pointer address(reference __x) const _NOEXCEPT {
 148         return _VSTD::addressof(__x);
 149     }
 150     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 151     const_pointer address(const_reference __x) const _NOEXCEPT {
 152         return _VSTD::addressof(__x);
 153     }
 154
 155     _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_IN_CXX17
 156     _Tp* allocate(size_t __n, const void*) {
 157         return allocate(__n);
 158     }
 159
 160     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT {
 161         return size_type(~0) / sizeof(_Tp);
 162     }
 163
 164     template <class _Up, class... _Args>
 165     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 166     void construct(_Up* __p, _Args&&... __args) {
 167         ::new ((void*)__p) _Up(_VSTD::forward<_Args>(__args)...);
 168     }
 169
 170     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 171     void destroy(pointer __p) {
 172         __p->~_Tp();
 173     }
 174 #endif
 175 };
 176
 177 template <class _Tp>
 178 class _LIBCPP_TEMPLATE_VIS allocator<const _Tp>
 179     : private __non_trivial_if<!is_void<_Tp>::value, allocator<const _Tp> >
 180 {
 181     static_assert(!is_volatile<_Tp>::value, "std::allocator does not support volatile types");
 182 public:
 183     typedef size_t      size_type;
 184     typedef ptrdiff_t   difference_type;
 185     typedef const _Tp   value_type;
 186     typedef true_type   propagate_on_container_move_assignment;
 187     typedef true_type   is_always_equal;
 188
 189     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 allocator() _NOEXCEPT = default;
 190
 191     template <class _Up>
 192     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 193     allocator(const allocator<_Up>&) _NOEXCEPT { }
 194
 195     _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 196     const _Tp* allocate(size_t __n) {
 197         if (__n > allocator_traits<allocator>::max_size(*this))
 198             __throw_bad_array_new_length();
 199         if (__libcpp_is_constant_evaluated()) {
 200             return static_cast<const _Tp*>(::operator new(__n * sizeof(_Tp)));
 201         } else {
 202             return static_cast<const _Tp*>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
 203         }
 204     }
 205
 206 #if _LIBCPP_STD_VER >= 23
 207     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr
 208     allocation_result<const _Tp*> allocate_at_least(size_t __n) {
 209         return {allocate(__n), __n};
 210     }
 211 #endif
 212
 213     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 214     void deallocate(const _Tp* __p, size_t __n) {
 215         if (__libcpp_is_constant_evaluated()) {
 216             ::operator delete(const_cast<_Tp*>(__p));
 217         } else {
 218             _VSTD::__libcpp_deallocate((void*) const_cast<_Tp *>(__p), __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
 219         }
 220     }
 221
 222     // C++20 Removed members
 223 #if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
 224     _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* pointer;
 225     _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* const_pointer;
 226     _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& reference;
 227     _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& const_reference;
 228
 229     template <class _Up>
 230     struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
 231         typedef allocator<_Up> other;
 232     };
 233
 234     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 235     const_pointer address(const_reference __x) const _NOEXCEPT {
 236         return _VSTD::addressof(__x);
 237     }
 238
 239     _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_IN_CXX17
 240     const _Tp* allocate(size_t __n, const void*) {
 241         return allocate(__n);
 242     }
 243
 244     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT {
 245         return size_type(~0) / sizeof(_Tp);
 246     }
 247
 248     template <class _Up, class... _Args>
 249     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 250     void construct(_Up* __p, _Args&&... __args) {
 251         ::new ((void*)__p) _Up(_VSTD::forward<_Args>(__args)...);
 252     }
 253
 254     _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
 255     void destroy(pointer __p) {
 256         __p->~_Tp();
 257     }
 258 #endif
 259 };
 260
 261 template <class _Tp, class _Up>
 262 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
 263 bool operator==(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {return true;}
 264
 265 #if _LIBCPP_STD_VER <= 17
 266
 267 template <class _Tp, class _Up>
 268 inline _LIBCPP_INLINE_VISIBILITY
 269 bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {return false;}
 270
 271 #endif
 272
 273 _LIBCPP_END_NAMESPACE_STD
 274
 275 #endif // _LIBCPP___MEMORY_ALLOCATOR_H