Thread: invalid use of incomplete type 'struct a'

Hi to all, I m quite new to c++ and i try to compile this little program without success...

Code:

class b;
class a;

class b
{
public:
    a *aa;
    b()
    {
        aa = new a();
    }
    ~b();
};
class a
{
public:
    b *bb;
    a()
    {
        bb = new b();
    }
    ~a();
};


void main(int argc, char *argv[])
{
    a my_a;
    b my_b;
}

What is wrong with this code ?

Thank you for your coments and help.