std::ranges::destroy

 

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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) 受限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) 垃圾回收支持 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
调用签名
template< no-throw-input-iterator I, no-throw-sentinel-for<I> S >     requires std::destructible<std::iter_value_t<I>> constexpr I destroy( I first, S last ) noexcept;	(1)	(自 C++20 起)
template< no-throw-input-range R >     requires std::destructible<ranges::range_value_t<R>> constexpr ranges::borrowed_iterator_t<R> destroy( R&& r ) noexcept;	(2)	(自 C++20 起)

1) 销毁范围 [first, last) 中的对象，如同通过

for (; first != last; ++first)
    std::ranges::destroy_at(std::addressof(*first));
return first;

2) 与 (1) 相同，但使用 r 作为源范围，如同使用 ranges::begin(r) 作为 first 以及 ranges::end(r) 作为 last。

此页面上描述的函数式实体为 niebloids，即

• 调用它们时，不能指定显式模板参数列表。
• 它们都不对 与参数相关的查找 可见。
• 当它们中的任何一个被 普通无限定查找 作为函数调用运算符左侧的名称找到时，与参数相关的查找 将被禁止。

实际上，它们可能被实现为函数对象，或使用特殊的编译器扩展。

参数

first, last	-	迭代器-哨兵对，表示要销毁的元素范围
r	-	要销毁的范围

返回值

一个与 last 相等的迭代器。

复杂度

从 first 到 last 的距离的线性时间。

可能的实现

struct destroy_fn { template<no-throw-input-iterator I, no-throw-sentinel-for<I> S> requires std::destructible<std::iter_value_t<I>> constexpr I operator()(I first, S last) const noexcept { for (; first != last; ++first) std::ranges::destroy_at(std::addressof(*first)); return first; }   template<no-throw-input-range R> requires std::destructible<std::ranges::range_value_t<R>> constexpr std::ranges::borrowed_iterator_t<R> operator()(R&& r) const noexcept { return operator()(std::ranges::begin(r), std::ranges::end(r)); } };   inline constexpr destroy_fn destroy{};

示例

以下示例演示了如何使用ranges::destroy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));
 
    std::ranges::destroy(ptr, ptr + 8);
}

输出

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

参见

ranges::destroy_n (C++20)	销毁范围内的多个对象 (niebloid)
ranges::destroy_at (C++20)	销毁指定地址处的对象 (niebloid)
destroy (C++17)	销毁对象范围 (函数模板)