std::destroy_at

 

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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) voidify (C++20) 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::construct_at (C++20) ranges::destroy (C++20) ranges::destroy_n (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 (C++20) ranges::uninitialized_value_construct (C++20) ranges::uninitialized_default_construct_n (C++20)   ranges::uninitialized_value_construct_n (C++20) 分配器 allocator allocator_traits (C++11) allocation_result (C++23) 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) 垃圾收集支持 declare_reachable (C++11)(直到 C++23) undeclare_reachable (C++11)(直到 C++23) declare_no_pointers (C++11)(直到 C++23) undeclare_no_pointers (C++11)(直到 C++23) pointer_safety (C++11)(直到 C++23) get_pointer_safety (C++11)(直到 C++23) 未初始化存储 raw_storage_iterator (直到 C++20*) get_temporary_buffer (直到 C++20*) return_temporary_buffer (直到 C++20*) 显式生命周期管理 start_lifetime_asstart_lifetime_as_array (C++23)(C++23)

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定义在头文件 <memory> 中
template< class T > void destroy_at( T* p );		(自 C++17 起) (直到 C++20)
template< class T > constexpr void destroy_at( T* p );		(自 C++20 起)

如果 T 不是数组类型，则调用 p 指向的对象的析构函数，如同调用 p->~T() 一样。

如果 T 是数组类型，程序格式不正确(直到 C++20)递归地销毁 *p 中的元素，顺序如同调用 std::destroy(std::begin(*p), std::end(*p)) 一样(自 C++20 起).

参数

p

-

指向要销毁的对象的指针

返回值

(无)

可能的实现

template<class T> constexpr void destroy_at(T* p) { if constexpr (std::is_array_v<T>) for (auto &elem : *p) (destroy_at)(std::addressof(elem)); else p->~T(); } // C++17 version: // template<class T> void destroy_at(T* p) { p->~T(); }

备注

destroy_at 推断要销毁的对象的类型，因此避免在析构函数调用中显式写入它。

当在某些 常量表达式 e 的求值中调用 destroy_at 时，参数 p 必须指向一个对象，该对象的生存期始于 e 的求值之中。

(自 C++20 起)

示例

以下示例演示如何使用 destroy_at 销毁连续的元素序列。

运行此代码

#include <iostream>
#include <memory>
#include <new>
 
struct Tracer
{
    int value;
    ~Tracer() { std::cout << value << " destructed\n"; }
};
 
int main()
{
    alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8];
 
    for (int i = 0; i < 8; ++i)
        new(buffer + sizeof(Tracer) * i) Tracer{i}; //manually construct objects
 
    auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer));
 
    for (int i = 0; i < 8; ++i)
        std::destroy_at(ptr + i);
}

输出

0 destructed
1 destructed
2 destructed
3 destructed
4 destructed
5 destructed
6 destructed
7 destructed

另请参阅

destroy (C++17)	销毁一系列对象 (函数模板)
destroy_n (C++17)	销毁一系列对象中的多个对象 (函数模板)
construct_at (C++20)	在给定地址处创建对象 (函数模板)
ranges::destroy_at (C++20)	销毁给定地址处的对象 (niebloid)