placement new to defer to a different constructor

Question

Is this safe? I\'m not using any virtual functions in my actual implementation, but I\'m tempted to believe that even if I was, it would still be safe.

clas         


        

Answer 1

You wouldn't be safe if you extended another class and that class had a destructor, for example

class Foo
{
    int* a;
public:
    Foo():a(new int)
    {

    }
    ~Foo(){delete a;}
}

class Bar:public Foo
{
    Bar()
    {
        // initialize things
    }

    Bar( int )
    {
         new ( this ) Foo();
    }
}

First Bar(int) calls Foo(), then it calls Bar() which also calls Foo(). The second time Foo() is called, it overwrites the pointer set up by the first call to Foo(), and the allocated memory is leaked.