🚀 go-pugleaf

>>>>> Albert Golembiowski <albert@inrs-telecom.uquebec.ca> writes:

> Dear Expert,
> Just 'd like to hear a confirmation that the g++-2.7.0 
> implementation of covariance is standard-compliant, stable, and it means:

>  [1] a virtual publicly inherited method
>        which returns a reference to a base object `b' of type `B' 

>         `virtual B& _Method() { /* do something */ return *this; }'
     
>       returns a reference to the derived object `d' of type `D' if called
>       from it, or through a base pointer, i.e. saying the following is
>       redundant
 
>          `virtual D& _Method() { B::_Method(); return *this; }' // 2

>       and only clutters the interface (and sweats the prerocessor) if
>       that all that `D& D::_Method()' is meant to do?

No.  The second method must be written if you want covariance.

>  [2] Is the statement //2// ever needed?

It is necessary for covariance.

>  [3] If I need a reference to B object returned from `d._Method()'
>      instead, do I always need to downcast?

You need to upcast, or you can rely on the implicit conversion if that will
work.

Your example does not test your hypothesis because Size is a virtual
function, so the D method is called even when the object parameter has a
static type of B.

Jason