std::nothrow

Since C++11

Header: <new>

std::nothrow_t is an empty class type used to disambiguate the overloads of throwing and non-throwing allocation functions. std::nothrow is a constant of it.

# Declarations

struct nothrow_t {};

(until C++11)

struct nothrow_t { explicit nothrow_t() = default; };

(since C++11)

extern const std::nothrow_t nothrow;

# Example

#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;
        }
    }
}

# Defect reports

DRApplied toBehavior as publishedCorrect behavior
LWG 2510C++11the default constructor was non-explicit, which could lead to ambiguitymade explicit

# See also