std::nothrow

 

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函数

operator newoperator new[]

operator deleteoperator delete[]

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bad_array_new_length (C++11)

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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 {};			(C++11 前)
struct nothrow_t { explicit nothrow_t() = default; };			(C++11 起)
extern const std::nothrow_t nothrow;		(2)

std::nothrow_t 是一个空的类类型，用于区分抛出异常和不抛出异常的分配函数的重载。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

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。

缺陷报告	应用于	发布时的行为	正确的行为
LWG 2510	C++11	默认构造函数不是 explicit 的，可能导致歧义	改为 explicit

参见

operator newoperator new[]

分配函数 (函数)