v1/__memory/allocator.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___MEMORY_ALLOCATOR_H
0011 #define _LIBCPP___MEMORY_ALLOCATOR_H
0012
0013 #include <__config>
0014 #include <__cstddef/ptrdiff_t.h>
0015 #include <__cstddef/size_t.h>
0016 #include <__memory/addressof.h>
0017 #include <__memory/allocate_at_least.h>
0018 #include <__memory/allocator_traits.h>
0019 #include <__new/allocate.h>
0020 #include <__new/exceptions.h>
0021 #include <__type_traits/is_const.h>
0022 #include <__type_traits/is_constant_evaluated.h>
0023 #include <__type_traits/is_same.h>
0024 #include <__type_traits/is_void.h>
0025 #include <__type_traits/is_volatile.h>
0026 #include <__utility/forward.h>
0027
0028 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0029 #  pragma GCC system_header
0030 #endif
0031
0032 _LIBCPP_BEGIN_NAMESPACE_STD
0033
0034 template <class _Tp>
0035 class allocator;
0036
0037 #if _LIBCPP_STD_VER <= 17
0038 // These specializations shouldn't be marked _LIBCPP_DEPRECATED_IN_CXX17.
0039 // Specializing allocator<void> is deprecated, but not using it.
0040 template <>
0041 class _LIBCPP_TEMPLATE_VIS allocator<void> {
0042 public:
0043   _LIBCPP_DEPRECATED_IN_CXX17 typedef void* pointer;
0044   _LIBCPP_DEPRECATED_IN_CXX17 typedef const void* const_pointer;
0045   _LIBCPP_DEPRECATED_IN_CXX17 typedef void value_type;
0046
0047   template <class _Up>
0048   struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
0049     typedef allocator<_Up> other;
0050   };
0051 };
0052 #endif // _LIBCPP_STD_VER <= 17
0053
0054 // This class provides a non-trivial default constructor to the class that derives from it
0055 // if the condition is satisfied.
0056 //
0057 // The second template parameter exists to allow giving a unique type to __non_trivial_if,
0058 // which makes it possible to avoid breaking the ABI when making this a base class of an
0059 // existing class. Without that, imagine we have classes D1 and D2, both of which used to
0060 // have no base classes, but which now derive from __non_trivial_if. The layout of a class
0061 // that inherits from both D1 and D2 will change because the two __non_trivial_if base
0062 // classes are not allowed to share the same address.
0063 //
0064 // By making those __non_trivial_if base classes unique, we work around this problem and
0065 // it is safe to start deriving from __non_trivial_if in existing classes.
0066 template <bool _Cond, class _Unique>
0067 struct __non_trivial_if {};
0068
0069 template <class _Unique>
0070 struct __non_trivial_if<true, _Unique> {
0071   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __non_trivial_if() _NOEXCEPT {}
0072 };
0073
0074 // allocator
0075 //
0076 // Note: For ABI compatibility between C++20 and previous standards, we make
0077 //       allocator<void> trivial in C++20.
0078
0079 template <class _Tp>
0080 class _LIBCPP_TEMPLATE_VIS allocator : private __non_trivial_if<!is_void<_Tp>::value, allocator<_Tp> > {
0081   static_assert(!is_const<_Tp>::value, "std::allocator does not support const types");
0082   static_assert(!is_volatile<_Tp>::value, "std::allocator does not support volatile types");
0083
0084 public:
0085   typedef size_t size_type;
0086   typedef ptrdiff_t difference_type;
0087   typedef _Tp value_type;
0088   typedef true_type propagate_on_container_move_assignment;
0089 #if _LIBCPP_STD_VER <= 23 || defined(_LIBCPP_ENABLE_CXX26_REMOVED_ALLOCATOR_MEMBERS)
0090   _LIBCPP_DEPRECATED_IN_CXX23 typedef true_type is_always_equal;
0091 #endif
0092
0093   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 allocator() _NOEXCEPT = default;
0094
0095   template <class _Up>
0096   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 allocator(const allocator<_Up>&) _NOEXCEPT {}
0097
0098   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp* allocate(size_t __n) {
0099     static_assert(sizeof(_Tp) >= 0, "cannot allocate memory for an incomplete type");
0100     if (__n > allocator_traits<allocator>::max_size(*this))
0101       __throw_bad_array_new_length();
0102     if (__libcpp_is_constant_evaluated()) {
0103       return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
0104     } else {
0105       return std::__libcpp_allocate<_Tp>(__element_count(__n));
0106     }
0107   }
0108
0109 #if _LIBCPP_STD_VER >= 23
0110   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr allocation_result<_Tp*> allocate_at_least(size_t __n) {
0111     static_assert(sizeof(_Tp) >= 0, "cannot allocate memory for an incomplete type");
0112     return {allocate(__n), __n};
0113   }
0114 #endif
0115
0116   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void deallocate(_Tp* __p, size_t __n) _NOEXCEPT {
0117     if (__libcpp_is_constant_evaluated()) {
0118       ::operator delete(__p);
0119     } else {
0120       std::__libcpp_deallocate<_Tp>(__p, __element_count(__n));
0121     }
0122   }
0123
0124   // C++20 Removed members
0125 #if _LIBCPP_STD_VER <= 17
0126   _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp* pointer;
0127   _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* const_pointer;
0128   _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp& reference;
0129   _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& const_reference;
0130
0131   template <class _Up>
0132   struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
0133     typedef allocator<_Up> other;
0134   };
0135
0136   _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI pointer address(reference __x) const _NOEXCEPT {
0137     return std::addressof(__x);
0138   }
0139   _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI const_pointer address(const_reference __x) const _NOEXCEPT {
0140     return std::addressof(__x);
0141   }
0142
0143   [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_DEPRECATED_IN_CXX17 _Tp* allocate(size_t __n, const void*) {
0144     return allocate(__n);
0145   }
0146
0147   _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
0148     return size_type(~0) / sizeof(_Tp);
0149   }
0150
0151   template <class _Up, class... _Args>
0152   _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI void construct(_Up* __p, _Args&&... __args) {
0153     ::new ((void*)__p) _Up(std::forward<_Args>(__args)...);
0154   }
0155
0156   _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI void destroy(pointer __p) { __p->~_Tp(); }
0157 #endif
0158 };
0159
0160 template <class _Tp, class _Up>
0161 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
0162 operator==(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {
0163   return true;
0164 }
0165
0166 #if _LIBCPP_STD_VER <= 17
0167
0168 template <class _Tp, class _Up>
0169 inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {
0170   return false;
0171 }
0172
0173 #endif
0174
0175 _LIBCPP_END_NAMESPACE_STD
0176
0177 #endif // _LIBCPP___MEMORY_ALLOCATOR_H