std::nothrow

 

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函式

operator newoperator new[]

operator deleteoperator delete[]

get_new_handler (C++11)

set_new_handler

類

bad_alloc

bad_array_new_length (C++11)

align_val_t (C++17)

型別

new_handler

物件

nothrow

destroying_delete (C++20)

物件訪問

launder (C++17)

 

定義於標頭檔案 <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 是一個空的類型別，用於區分丟擲異常和不丟擲異常的分配函式的過載。std::nothrow 是它的一個常量。

示例

執行此程式碼

#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;
        }
    }
}

輸出

std::bad_alloc
Allocation returned nullptr

缺陷報告

下列更改行為的缺陷報告追溯地應用於以前出版的 C++ 標準。

缺陷報告	應用於	釋出時的行為	正確的行為
LWG 2510	C++11	預設建構函式不是 explicit 的，可能導致歧義	改為 explicit

參見

operator newoperator new[]

分配函式 (函式)