C++: Pointer to monomorphic version of virtual member function?

Question

In C++, it\'s possible to get a pointer to a (non-static) member function of a class, and then later invoke it on an object. If the function was virtual, the call is dispatc

Answer 1

To elaborate with a code example for a wrapper function (and despite the fact the OP wanted to avoid this method!) as in many cases this is the pragmatically preferable solution:

#include <iostream>
using std::cout; using std::endl;

struct Foo
{
    virtual void foo() { cout << 1 << endl; }
};

struct Foo2: public Foo
{
    virtual void foo() { cout << 2 << endl; }
};

void monomorphicFooFoo( Foo * f ) { f->Foo::foo(); }

int main()
{
    Foo *foo = new Foo2;

    void (*baseFoo)( Foo * ) = &monomorphicFooFoo;
    baseFoo( foo ); // Prints 1
}

Answer 2

In other words : you want to cheat.

No, it is not possible because that is how the polymorphism in combination with pointer to member method works.

Answer 3

It's possible in GCC, but the way it's documented in C++ language extensions section suggests there's no portable way to do it.

You can do two things:

1. If you control the class, create a non-virtual function and a virtual wrapper for it and when you know you don't need virtual dispatch, just take address of the non-virtual one.
2. If you don't, create a template functor that will hold the member pointer and do the explicit scope call.