🚀 go-pugleaf

Version: MW IDE 1.3, 68k C++ 1.3 running under System 7.5.1 on Quadra 700.
Reproducability: ALWAYS
Type: gotcha :)

Take this code below. The subclassed virtual function omits the 'const'.
This appears to MW C++ as a new overloaded function (even though this is
the only difference) and hence the 'OverrideMe()' function doesn't behave
polymorphically as one may at first look expect.

Most compilers return a warning when a subclass overloads a parent
function that differs only in return type. Could I suggest that when the
return type differs only in 'const' that this could be flagged as a
warning as well?

FYI, gnu g++ 2.7.0 also gives similar results.


----
#include <iostream.h>

template< class X > class T
    {
    public:
        virtual void    CallMe( X a )
                            {
                            cout << "CallMe from T" << a << endl;
                            OverrideMe( a );
                            }
    protected:              
        virtual void    OverrideMe( X a ) const
                            {
                            cout << "OverrideMe from T" << a << endl;
                            }
    };



class Derived: public T<int>
    {
    public:
        virtual void    OverrideMe( int da )
                            {
                            cout << "OverrideMe from Derived" << da << endl;
                            }
    };



int main( void ) {
    T<int> *p = new Derived();
    Derived q;
    T<int> r( q );
    
    p->CallMe( 4 );
    q.CallMe( 5 );
    r.CallMe( 6 );
    
    return 0;
}

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Microsoft is not the answer.                    >  Julian Harris, Programmer   >
Microsoft is the question.                     >  Comp. Sci. Dept.     x8915  >
                                              >  The University of Auckland  >
NO is the answer.                            >  julian@cs.auckland.ac.nz    >