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std::set_new_handler - cppreference.com

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Defined in header <new>

std::new_handler set_new_handler( std::new_handler new_p ) throw();

 (until C++11)

std::new_handler set_new_handler( std::new_handler new_p ) noexcept;

 (since C++11)

Makes new_p the new global new-handler function and returns the previously installed new-handler.

The new-handler function is the function called by allocation functions whenever a memory allocation attempt fails. Its intended purpose is one of three things:

1) make more memory available,

2) terminate the program (e.g. by calling std::terminate),

3) throw exception of type std::bad_alloc or derived from std::bad_alloc.

The default implementation throws std::bad_alloc. The user can install their own new-handler, which may offer behavior different than the default one.

If new-handler returns, the allocation function repeats the previously-failed allocation attempt and calls the new-handler again if the allocation fails again. To end the loop, new-handler may call std::set_new_handler(nullptr): if, after a failed allocation attempt, allocation function finds that std::get_new_handler returns a null pointer value, it will throw std::bad_alloc.

At program startup, new-handler is a null pointer.

This function is thread-safe. Every call to std::set_new_handler synchronizes-with (see std::memory_order) the subsequent std::set_new_handler and std::get_new_handler calls.

(since C++11)

Parameters

new_p - pointer to function of type std::new_handler, or null pointer

Return value

The previously-installed new handler, or a null pointer value if none was installed.

Example

#include <iostream>
#include <new>

void handler()
{
    std::cout << "Memory allocation failed, terminating\n";
    std::set_new_handler(nullptr);
}

int main()
{
    std::set_new_handler(handler);
    try
    {
        while (true)
        {
            new int[1000'000'000ul]();
        }
    }
    catch (const std::bad_alloc& e)
    {
        std::cout << e.what() << '\n';
    }
}

Possible output: 

Memory allocation failed, terminating
std::bad_alloc

See also