Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

#include <iostream>
#include <new>       // std::nothrow, placement new
#include <cstdlib>   // std::malloc, std::free

struct Widget {
    Widget(int id) : id_(id) {
        std::cout << "Widget(" << id_ << ") constructed
";
    }
    ~Widget() {
        std::cout << "Widget(" << id_ << ") destroyed
";
    }
    int id_;
};

int main() {
    // Scalar new/delete
    Widget* w = new Widget(1);
    delete w;

// Array new/delete
    Widget* arr = new Widget[3]{2, 3, 4};
    delete[] arr;   // must use delete[], not delete

// nothrow: returns nullptr instead of throwing
    Widget* big = new (std::nothrow) Widget(5);
    if (!big) {
        std::cout << "Allocation failed
";
    } else {
        delete big;
    }

// Placement new: construct into pre-allocated buffer
    alignas(Widget) unsigned char buf[sizeof(Widget)];
    Widget* pw = new (buf) Widget(99);   // no heap allocation
    std::cout << "Placed widget id: " << pw->id_ << "
";
    pw->~Widget();   // explicit destructor — do NOT delete pw

// Alignment query
    std::cout << "alignof(Widget) = " << alignof(Widget) << "
";
    std::cout << "sizeof(Widget)  = " << sizeof(Widget)  << "
";

return 0;
}