std::nothrow

 

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函数

operator newoperator new[]

operator deleteoperator delete[]

get_new_handler (C++11)

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类

bad_alloc

bad_array_new_length (C++11)

align_val_t (C++17)

类型

new_handler

对象

nothrow

destroying_delete (C++20)

对象访问

launder (C++17)

 

定义于头文件 <new>
	(1)
struct nothrow_t {};			(直到 C++11)
struct nothrow_t { explicit nothrow_t() = default; };			(自 C++11 起)
extern const std::nothrow_t nothrow;		(2)

std::nothrow_t 是一个空类类型，用于消除抛出和非抛出 分配函数 的重载歧义。std::nothrow 是它的一个常量。

示例

运行此代码

#include <iostream>
#include <new>
 
int main()
{
    try
    {
        while (true)
        {
            new int[100000000ul];   // throwing overload
        }
    }
    catch (const std::bad_alloc& e)
    {
        std::cout << e.what() << '\n';
    }
 
    while (true)
    {
        int* p = new(std::nothrow) int[100000000ul]; // non-throwing overload
        if (p == nullptr)
        {
            std::cout << "Allocation returned nullptr\n";
            break;
        }
    }
}

输出

std::bad_alloc
Allocation returned nullptr

缺陷报告

以下行为变更缺陷报告被追溯应用于之前发布的 C++ 标准。

DR	应用于	已发布行为	正确行为
LWG 2510	C++11	默认构造函数是非显式的，这可能导致歧义	设为显式

参见

operator newoperator new[]

分配函数 (函数)