vbase11_x.c

gcc-you can use this code to learn something about gcc, and inquire further into linux,

#include "vbase11.h"

extern void vbase11_y (derived&);

int base::foo() { return 1; }
int derived::foo() { return 2; }
int derived::bar() { return 3; }

void vbase11_x ()
{
  derived d;

  vbase11_y (d);
}