Re: avoiding virtual call with pointer to member function

From:

xtrigger303@gmail.com

Newsgroups:

comp.lang.c++

Date:

4 Apr 2007 14:25:19 -0700

Message-ID:

<1175721919.517204.118690@w1g2000hsg.googlegroups.com>

Thanks for the reply, but doesn't work. I (guess) the vptr points
always to the same vtable.
Tried below

#include <iostream>

struct Base
{
    virtual ~Base() {}
    virtual void Do() const { std::cout << "Base\n"; }
};

struct Der : public Base
{
    virtual void Do() const { std::cout << "Der\n"; }
};

int main()
{
    Der obj;

    obj.Base::Do(); // avoid virtual call

    void ( Base::*ptrToMembFunc )() const = &Base::Do;

    ( obj.*ptrToMembFunc )(); // virtual call
    // is there a way to avoid virtual call with pointers to member
functions
    // as in the above direct call?

    ( static_cast< Base & >( obj ).*ptrToMembFunc )();
    // won't work, the vptr always points to the same vtable

}

On Apr 4, 11:14 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:

xtrigger...@gmail.com wrote:

Hi to all,
a newbie question. Is it possible to avoid the virtual mechanism with
pointers to members syntax the same way it's done with an explicit
call ( obj.Base::Func() )? It would be useful for something I'm
doing... check out the trivial program down here...
Thanks in advance,
Francesco

#include <iostream>

struct Base
{
virtual ~Base() {}
virtual void Do() const { std::cout << "Base\n"; }
};

struct Der : public Base
{
virtual void Do() const { std::cout << "Der\n"; }
};

int main()
{
Der obj;

obj.Base::Do(); // avoid virtual call

void ( Base::*ptrToMembFunc )() const = &Base::Do;

( obj.*ptrToMembFunc )(); // virtual call
// is there a way to avoid virtual call with pointers to member
functions
// as in the above direct call?
}

You could try forcing 'obj' into being a 'Base' by means of
'static_cast'...

V
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