operator==,!=(std::allocator)

 

C++

编译器支持

自立实现与有宿主实现

语言

标准库

标准库标头

具名要求

功能特性测试宏 (C++20)

语言支持库

概念库 (C++20)

诊断库

内存管理库

元编程库 (C++11)

通用工具库

容器库

迭代器库

范围库 (C++20)

算法库

字符串库

文本处理库

数值库

日期和时间库

输入/输出库

文件系统库 (C++17)

并发支持库 (C++11)

执行控制库 (C++26)

技术规范

符号索引

外部库

 

内存管理库

voidify (仅用于阐述*) 分配器 allocator allocator_traits (C++11) allocation_result (C++23) scoped_allocator_adaptor (C++11) pmr::polymorphic_allocator (C++17) allocator_arg (C++11) uses_allocator (C++11) uses_allocator_construction_args (C++20) make_obj_using_allocator (C++20) uninitialized_construct_using_allocator (C++20) 未初始化内存算法 uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_copy_n (C++11) uninitialized_fill_n uninitialized_move_n (C++17) construct_at (C++20) uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) destroy (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17) destroy_n (C++17) destroy_at (C++17) 受约束的未初始化内存算法 ranges::uninitialized_copy (C++20) ranges::uninitialized_fill (C++20) ranges::uninitialized_move (C++20) ranges::uninitialized_copy_n (C++20)  ranges::uninitialized_fill_n (C++20) ranges::uninitialized_move_n (C++20) ranges::construct_at (C++20) ranges::uninitialized_default_construct (C++20) ranges::uninitialized_value_construct (C++20) ranges::destroy (C++20) ranges::uninitialized_default_construct_n (C++20)  ranges::uninitialized_value_construct_n (C++20) ranges::destroy_n (C++20) ranges::destroy_at (C++20) 内存资源 pmr::memory_resource (C++17) pmr::get_default_resource (C++17) pmr::set_default_resource (C++17) pmr::new_delete_resource (C++17) pmr::pool_options (C++17) pmr::null_memory_resource (C++17) pmr::synchronized_pool_resource (C++17) pmr::unsynchronized_pool_resource (C++17) pmr::monotonic_buffer_resource (C++17) 显式生存期管理 start_lifetime_as (C++23) start_lifetime_as_array (C++23) 用于复合类设计的类型 indirect (C++26) polymorphic (C++26) 未初始化存储 (C++20 前) raw_storage_iterator (C++17 弃用) get_temporary_buffer (C++17 弃用) return_temporary_buffer (C++17 弃用) 垃圾收集器支持 (C++23 前) declare_reachable (C++11)(C++23 前) declare_no_pointers (C++11)(C++23 前) pointer_safety (C++11)(C++23 前) undeclare_reachable (C++11)(C++23 前) undeclare_no_pointers (C++11)(C++23 前) get_pointer_safety (C++11)(C++23 前)

低层内存管理 operator newoperator new[] operator deleteoperator delete[] nothrow_t nothrow new_handler set_new_handler get_new_handler (C++11) bad_alloc bad_array_new_length (C++11) align_val_t (C++17) destroying_delete_t (C++20) launder (C++17) 智能指针 unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (C++17 前*) owner_less (C++11) owner_less<void> (C++17) owner_hash (C++26) owner_equal (C++26) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) out_ptr_t (C++23) inout_ptr_t (C++23) 杂项 pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) is_sufficiently_aligned (C++26) C 库 malloc calloc realloc free aligned_alloc (C++17)

 

std::allocator

成员函数

allocator::allocator

allocator::~allocator

allocator::address (C++20 前)

allocator::allocate

allocator::allocate_at_least (C++23)

allocator::deallocate

allocator::max_size (C++20 前)

allocator::construct (C++20 前)

allocator::destroy (C++20 前)

非成员函数

operator==operator!= (C++20 前)

 

	(1)
template< class T1, class T2 > bool operator==( const allocator<T1>& lhs, const allocator<T2>& rhs ) throw();			(C++11 前)
template< class T1, class T2 > bool operator==( const allocator<T1>& lhs, const allocator<T2>& rhs ) noexcept;			(C++11 起) (C++20 前)
template< class T1, class T2 > constexpr bool operator==( const allocator<T1>& lhs, const allocator<T2>& rhs ) noexcept;			(C++20 起)
	(2)
template< class T1, class T2 > bool operator!=( const allocator<T1>& lhs, const allocator<T2>& rhs ) throw();			(C++11 前)
template< class T1, class T2 > bool operator!=( const allocator<T1>& lhs, const allocator<T2>& rhs ) noexcept;			(C++11 起) (C++20 前)

比较两个默认分配器。因为默认分配器无状态，故两个默认分配器始终相等。

1) 返回 true。

2) 返回 false。

!= 运算符从 operator== 运算符合成。

(C++20 起)

参数

lhs, rhs

-

要比较的默认分配器

返回值

1) true

2) false