NAME

std::nothrow - std::nothrow

Synopsis

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

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 made explicit
could lead to ambiguity

See also

operator new allocation functions
operator new[] (function)