<new> defines operator new and operator delete for memory allocation. You can overload them for custom allocation behavior or set a custom new_handler function to be called if allocation fails.

Most code never needs this; just use smart pointers from <memory>.

This example sets a custom new_handler to be called if memory allocation fails, though modern code uses smart pointers instead.

// compile: g++ -std=c++11 -o newexample newexample.cpp
// run: ./newexample
// description: custom new_handler
 
#include <new>
#include <iostream>
 
void handle_out_of_memory() {
    std::cout << "out of memory!\n";
    std::exit(1);
}
 
int main() {
    std::set_new_handler(handle_out_of_memory);
 
    try {
        int* p = new int;
        std::cout << "allocated successfully\n";
        delete p;
    } catch (const std::bad_alloc&) {
        std::cout << "caught bad_alloc\n";
    }
 
    return 0;
}