operator==,!=,<,<=,>,>=,<=>(std::unique_ptr)

 

C++

语言

标准库头文件

自立与有宿主实现

具名要求

语言支持库

概念库 (C++20)

诊断库

工具库

字符串库

容器库

迭代器库

范围库 (C++20)

算法库

数值库

本地化库

输入/输出库

文件系统库 (C++17)

正则表达式库 (C++11)

原子操作库 (C++11)

线程支持库 (C++11)

技术规范

 

工具库

语言支持 类型支持（基本类型、 RTTI 、类型特征）     库功能特性测试宏 (C++20) 动态内存管理 程序工具 错误处理 协程支持 (C++20) 变参数函数 launder (C++17) initializer_list (C++11) source_location (C++20) 三路比较 (C++20) three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20) is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

通用工具 日期和时间 函数对象 bitset 格式化库 (C++20) hash (C++11) integer_sequence (C++14) 关系运算符 (C++20 中弃用) rel_ops::operator!=rel_ops::operator> rel_ops::operator<=rel_ops::operator>= 整数比较函数 cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20) cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) swap 与类型运算 swap ranges::swap (C++20) exchange (C++14) declval (C++11) forward (C++11) move (C++11) move_if_noexcept (C++11) as_const (C++17) to_underlying (C++23) 常用词汇类型 pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) 初等字符串转换 to_chars (C++17) from_chars (C++17) chars_format (C++17) 栈踪 stacktrace_entry (C++23) basic_stacktrace (C++23)

 

动态内存管理

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) 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) 分配器 allocator allocator_traits (C++11) allocation_result (C++23) allocate_at_least (C++23) allocator_arg_t (C++11) 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) scoped_allocator_adaptor (C++11) pmr::polymorphic_allocator (C++17) 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::null_memory_resource (C++17) pmr::synchronized_pool_resource (C++17) pmr::unsynchronized_pool_resource (C++17) pmr::monotonic_buffer_resource (C++17) pmr::pool_options (C++17) 未初始化存储 raw_storage_iterator (C++20 前) get_temporary_buffer (C++20 前) return_temporary_buffer (C++20 前)

未初始化内存算法 uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) destroy (C++17) destroy_at (C++17) uninitialized_copy_n (C++11) uninitialized_fill_n uninitialized_move_n (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17) destroy_n (C++17) construct_at (C++20) 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_default_construct (C++20) ranges::uninitialized_value_construct (C++20) ranges::destroy (C++20) ranges::destroy_at (C++20) ranges::uninitialized_copy_n (C++20) ranges::uninitialized_fill_n (C++20) ranges::uninitialized_move_n (C++20) ranges::uninitialized_default_construct_n (C++20) ranges::uninitialized_value_construct_n (C++20) ranges::destroy_n (C++20) ranges::construct_at (C++20) 垃圾收集支持 declare_reachable (C++11)(C++23 前) undeclare_reachable (C++11)(C++23 前) declare_no_pointers (C++11)(C++23 前) undeclare_no_pointers (C++11)(C++23 前) pointer_safety (C++11)(C++23 前) get_pointer_safety (C++11)(C++23 前) 杂项 pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) C 库 malloc aligned_alloc (C++17) calloc realloc free 低层内存管理

 

std::unique_ptr

成员函数

unique_ptr::unique_ptr

unique_ptr::~unique_ptr

unique_ptr::operator=

修改器

unique_ptr::release

unique_ptr::reset

unique_ptr::swap

观察器

unique_ptr::get

unique_ptr::get_deleter

unique_ptr::operator bool

unique_ptr::operator*unique_ptr::operator->

unique_ptr::operator[]

非成员函数

make_uniquemake_unique_for_overwrite (C++14)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (C++20 前)(C++20)

operator<< (C++20)

std::swap

std::hash

 

定义于头文件 <memory>
template<class T1, class D1, class T2, class D2> bool operator==(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(1)	(C++11 起)
template<class T1, class D1, class T2, class D2> bool operator!=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(2)	(C++11 起) (C++20 前)
template<class T1, class D1, class T2, class D2> bool operator<(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(3)	(C++11 起)
template<class T1, class D1, class T2, class D2> bool operator<=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(4)	(C++11 起)
template<class T1, class D1, class T2, class D2> bool operator>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(5)	(C++11 起)
template<class T1, class D1, class T2, class D2> bool operator>=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(6)	(C++11 起)
template<class T1, class D1, class T2, class D2>     requires std::three_way_comparable_with<         typename unique_ptr<T1, D1>::pointer,         typename unique_ptr<T2, D2>::pointer> std::compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,                                 typename unique_ptr<T2, D2>::pointer>     operator<=>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);	(7)	(C++20 起)
template <class T, class D> bool operator==(const unique_ptr<T, D>& x, std::nullptr_t) noexcept;	(8)	(C++11 起)
template <class T, class D> bool operator==(std::nullptr_t, const unique_ptr<T, D>& x) noexcept;	(9)	(C++11 起) (C++20 前)
template <class T, class D> bool operator!=(const unique_ptr<T, D>& x, std::nullptr_t) noexcept;	(10)	(C++11 起) (C++20 前)
template <class T, class D> bool operator!=(std::nullptr_t, const unique_ptr<T, D>& x) noexcept;	(11)	(C++11 起) (C++20 前)
template <class T, class D> bool operator<(const unique_ptr<T, D>& x, std::nullptr_t);	(12)	(C++11 起)
template <class T, class D> bool operator<(std::nullptr_t, const unique_ptr<T, D>& y);	(13)	(C++11 起)
template <class T, class D> bool operator<=(const unique_ptr<T, D>& x, std::nullptr_t);	(14)	(C++11 起)
template <class T, class D> bool operator<=(std::nullptr_t, const unique_ptr<T, D>& y);	(15)	(C++11 起)
template <class T, class D> bool operator>(const unique_ptr<T, D>& x, std::nullptr_t);	(16)	(C++11 起)
template <class T, class D> bool operator>(std::nullptr_t, const unique_ptr<T, D>& y);	(17)	(C++11 起)
template <class T, class D> bool operator>=(const unique_ptr<T, D>& x, std::nullptr_t);	(18)	(C++11 起)
template <class T, class D> bool operator>=(std::nullptr_t, const unique_ptr<T, D>& y);	(19)	(C++11 起)
template<class T, class D>     requires std::three_way_comparable<typename unique_ptr<T, D>::pointer> std::compare_three_way_result_t<typename unique_ptr<T, D>::pointer>     operator<=>(const unique_ptr<T, D>& x, std::nullptr_t);	(20)	(C++20 起)

比较二个 unique_ptr 或 unique_ptr 与 nullptr 的指针值。

1-7) 比较二个 unique_ptr 。

8-20) 比较 unique_ptr 与 nullptr 。

!= 运算符从 operator== 合成。

(C++20 起)

参数

x, y

-

要比较的 unique_ptr

返回值

1) x.get() == y.get()

2) x.get() != y.get()

3) std::less<CT>()(x.get(), y.get()) ，其中 CT 是 std::common_type<unique_ptr<T1, D1>::pointer, unique_ptr<T2, D2>::pointer>::type

4) !(y < x)

5) y < x

6) !(x < y)

7) std::compare_three_way{}(x.get(), y.get())

8-9) !x

10-11) (bool)x

12) std::less<unique_ptr<T,D>::pointer>()(x.get(), nullptr)

13) std::less<unique_ptr<T,D>::pointer>()(nullptr, y.get())

14) !(nullptr < x)

15) !(y < nullptr)

16) nullptr < x

17) y < nullptr

18) !(x < nullptr)

19) !(nullptr < y)

20) std::compare_three_way{}(x.get(), static_cast<typename unique_ptr<T, D>::pointer>(nullptr))

示例

运行此代码

#include <iostream>
#include <memory>
 
int main() 
{
    std::unique_ptr<int> p1(new int(42));
    std::unique_ptr<int> p2(new int(42));
 
    std::cout << "p1 == p1: " << (p1 == p1) << '\n';
 
    // p1 与 p2 指向不同内存位置，故 p1 != p2
    std::cout << "p1 == p2: " << (p1 == p2) << '\n';
}

输出：

p1 == p1: 1
p1 == p2: 0

缺陷报告

下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。

DR	应用于	出版时的行为	正确行为
LWG 3426	C++20	operator<=>(unique_ptr, nullptr_t) 为谬构	修正约束与定义

参阅

get	返回指向被管理对象的指针 (公开成员函数)