🚀 go-pugleaf

jhg@mpd.tandem.com (Jim Garrison) writes:

>The ARM states that it is illegal to declare a function in a 
>derived class that differs from a virtual in a parent class by 
>only its return type.  I.e.

>class A
>{
>        virtual int foo();
>}

>class B1 : public A
>{
>        char * foo(); // Illegal
>}


>Has the standard changed with respect to this?  IBM VisualAge C++ 
>now allows this (it's an EXTREMELY useful thing to be able to do),
>but the SGI compiler on which I'm working doesn't.

The draft standard allows "covariant return types".

If the base-class version of a virtual function returns a
pointer (or reference) to a class, the derived-class version may
return a pointer (or reference) to a class derived from the
original.

Your example above is not allowed, because char* is not derived
from int. If the IBM compiler allows it, that would be a
non-standard extension.
--
Steve Clamage, stephen.clamage@eng.sun.com


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