Placement `new` example

Foo.cpp

#include <stdio.h>
#include <new>

class Foo {
        int i;
        int j;
        public:
        Foo() {
                printf("The Foo at %p is constructing\n", this);
                i = 1;
                j = 5;
        }
};


class Bar {
        Foo a;
        char buf[sizeof(Foo)];

        Foo * bufFoo() {
                return (Foo *) buf;
        }
        public:
        Bar();

};


Bar::Bar()
        {
                printf("The inline Foo is at %p\n", &a);
                printf("The buffer is at %p\n", buf);
                new (bufFoo()) Foo();
        }


int main() {
        Bar bar;
        return 0;
}

$ ./Foo
The Foo at 0064FEC0 is constructing
The inline Foo is at 0064FEC0
The buffer is at 0064FEC8
The Foo at 0064FEC8 is constructing