Problems invoking a member function through pointers.

Problems invoking a member function through pointers.

[adriang]

In the following code I would expect the output to be:
Base::M1
Base::M1
Base::M2
Base::M2

To my surprise, the last line of the output says
Derived::M2

Does the standard mandate this behaviour?
I've tried with both Microsoft compiler and egcs.

thanx



#include <iostream>

class Interface
{
public:
    virtual void M1(void) = 0;
    virtual void M2(void) = 0;
};

class Base : public Interface
{
public:
    void M1(void){ std::cout << "Base::M1\n"; }
    void M2(void){ std::cout << "Base::M2\n"; }


    void Check(void);
};



class Derived1 : public Base
{
public:
    void M2(void){ std::cout << "Derived::M2\n"; }
};

void Base::Check(void)
{
    void (Base::*pfn1)(void) = &Base::M1;
    Base::M1();
    (this ->* pfn1)();

    void (Base::*pfn2)(void) = &Base::M2;
    Base::M2();
    (this ->* pfn2)();
}



void main(void)
{
    Derived1 d1;

    d1.Check();
}

Re: Problems invoking a member function through pointers.

[Alexandre Oliva]

On Dec 22, 1998, <adriang@adriang.ce.mediaone.net> wrote:

> To my surprise, the last line of the output says
> Derived::M2

> Does the standard mandate this behaviour?

Yep.  invoking member functions through pointers to member functions
always result in virtual dispatching.

-- 
Alexandre Oliva  http://www.dcc.unicamp.br/~oliva  aoliva@{acm.org}
oliva@{dcc.unicamp.br,gnu.org,egcs.cygnus.com,samba.org}
Universidade Estadual de Campinas, SP, Brasil

Re: Problems invoking a member function through pointers.

[Mike Stump]

> Date: Mon, 21 Dec 1998 23:08:06 -0600 (EST)
> From: <adriang@adriang.ce.mediaone.net>
> To: egcs@egcs.cygnus.com

> In the following code I would expect the output to be:
> Base::M1
> Base::M1
> Base::M2
> Base::M2

> To my surprise, the last line of the output says
> Derived::M2

This isn't the right group to learn C++ programming, comp.lang.c++ is
a better place.  Yes, this is what virtual means.  virtual means call
the most derived function in your class hierarchy.  If you don't want
that behavior, don't use virtual.

obj.Base::M2 () != obj .* (&Base::M2) ()