# std::nothrow

From cppreference.com
< cpp‎ | memory‎ | new

Defined in header `<new>` |  |
| (1) |
struct nothrow_t {}; |  | (until C++11)
struct nothrow_t { explicit nothrow_t() = default; }; |  | (since C++11)
extern const std::nothrow_t nothrow; | (2) |

`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.

### Example

Run this code

    #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;
            }
        }
    }

Output:

    std::bad_alloc
    Allocation returned nullptr

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 2510 | C++11 | the default constructor was non-explicit, which could lead to ambiguity | made explicit

### See also

operator newoperator new[] | allocation functions (function)

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