std::allocator_traits

STD：：分配器[医]性状

Defined in header
template< class Alloc > struct allocator_traits;		(since C++11)

大allocator_traits类模板提供了标准的方法来访问Allocator斯标准容器和其他标准库组件通过此模板访问分配器，这使得可以使用任何类类型作为分配器，只要用户提供的专门化allocator_traits实现所有必需的功能。

默认的，非专门化的，allocator_traits包含下列成员：

Type	Definition
allocator_type	Alloc
value_type	Alloc::value_type
pointer	Alloc::pointer if present, otherwise value_type*
const_pointer	Alloc::const_pointer if present, otherwise std::pointer_traits<pointer>::rebind<const value_type>
void_pointer	Alloc::void_pointer if present, otherwise std::pointer_traits<pointer>::rebind<void>
const_void_pointer	Alloc::const_void_pointer if present, otherwise std::pointer_traits<pointer>::rebind<const void>
difference_type	Alloc::difference_type if present, otherwise std::pointer_traits<pointer>::difference_type
size_type	Alloc::size_type if present, otherwise std::make_unsigned<difference_type>::type
propagate_on_container_copy_assignment	Alloc::propagate_on_container_copy_assignment if present, otherwise std::false_type
propagate_on_container_move_assignment	Alloc::propagate_on_container_move_assignment if present, otherwise std::false_type
propagate_on_container_swap	Alloc::propagate_on_container_swap if present, otherwise std::false_type
is_always_equal(since C++17)	Alloc::is_always_equal if present, otherwise std::is_empty<Alloc>::type

Type	Definition
rebind_alloc<T>	Alloc::rebind<T>::other if present, otherwise Alloc<T, Args> if this Alloc is Alloc<U, Args>
rebind_traits<T>	std::allocator_traits<rebind_alloc<T>>

allocate static	allocates uninitialized storage using the allocator (public static member function)
deallocate static	deallocates storage using the allocator (public static member function)
construct static	constructs an object in the allocated storage (function template)
destroy static	destructs an object stored in the allocated storage (function template)
max_size static	returns the maximum object size supported by the allocator (public static member function)
select_on_container_copy_construction static	obtains the allocator to use after copying a standard container (public static member function)

allocator	the default allocator (class template)
scoped_allocator_adaptor (C++11)	implements multi-level allocator for multi-level containers (class template)
pointer_traits (C++11)	provides information about pointer-like types (class template)

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