std::destroy_at

 

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在标头 <memory> 定义
template< class T > void destroy_at( T* p );		(C++17 起) (C++20 前)
template< class T > constexpr void destroy_at( T* p );		(C++20 起)

若 T 不是数组类型，则调用 p 所指向对象的析构函数，如同用 p->~T() 。

若 T 是数组类型，则程序非良构 (C++20 前)按顺序递归地销毁 *p 的元素，如同通过调用 std::destroy(std::begin(*p), std::end(*p)) (C++20 起)。

参数

p

-

指向要被销毁的对象的指针

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 版本： // template<class T> void destroy_at(T* p) { p->~T(); }

注解

destroy_at 推导要销毁的对象类型，从而避免在析构函数调用中显式写出它。

在某常量表达式 e 的求值中调用 destroy_at 时，参数 p 必须指向生存期始于 e 的求值内的对象。

(C++20 起)

示例

下列示例演示如何用 destroy_at 销毁元素的相接序列。

运行此代码

#include <memory>
#include <new>
#include <iostream>
 
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}; // 手工构造对象
 
    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

参阅

destroy (C++17)	销毁一个范围中的对象 (函数模板)
destroy_n (C++17)	销毁范围中一定数量的对象 (函数模板)
construct_at (C++20)	在给定地址创建对象 (函数模板)
ranges::destroy_at (C++20)	销毁位于给定地址的元素 (niebloid)