Namespaces
Variants
Views
Actions

std::nothrow

From cppreference.com
< cpp‎ | memory‎ | new
 
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
Dynamic memory management
Uninitialized memory algorithms
(C++17)
(C++17)
(C++20)
(C++17)
Constrained uninitialized
memory algorithms
C Library

Allocators
Memory resources
Garbage collection support
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
Uninitialized storage
(until C++20*)
(until C++20*)
Explicit lifetime management
 
 
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.

[edit] 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;
        }
    }
}

Output:

std::bad_alloc
Allocation returned nullptr

[edit] 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

[edit] See also

allocation functions
(function) [edit]