Question

I am reviewing a section of C++ code an I came accross this statement block:

static void Vector3DefaultConstructor(Vector3 *self)
{    
    new(self) Vector3();    
}

I have not come accross the new operator being used in this way before. Can someone explain why new is being called in this way?

Answer 1

This is called “placement new“. By default, it does not allocate memory but instead constructs the object at the given location (here, self). It can, however, be overloaded for a class.

See the FAQ for more info.

The correct way to destroy an object constructed using placement new is by calling the destructor directly:

obj->~Vector3();