comp.lang.c++

Hi,

I have been totally confused about the covariant return type feature
in C++. Below is an example code I wrote that doesn't compile with g++
4.1.2 (on Fedora 8)

class virt_base
{
public:
virt_base()
{
}

virtual ~virt_base()
{

}

virtual virt_base* cut()
{
return new virt_base();
}

void say_hi()
{
cout <<"hi!!! " < }
};

class virt_derived
: public virt_base
{
public:
virt_derived()
{
}

~virt_derived()
{

}

virtual virt_derived* cut()
{
return new virt_derived();
}

void say_hi()
{
cout <<"HI!!!! " < }
};

int main()
{
virt_base* my_virt_derived = new virt_derived();
virt_derived* new_virt_derived = my_virt_derived->cut(); // g++
complains here: invalid
//
conversion from 'virt_base*' to
//
'virt_derived*'
new_virt_derived->say_hi();
}

------------
It is very weird. Can somebody enlighten me what went wrong here?
Thanks in advance.