🚀 go-pugleaf

grosjean@masi.ibp.fr (Christophe GROSJEAN) wants to know why
his code doesn't exhibit virtual function call
behavior even though he has declared his functions
virtual.

:#include <stdio.h>
:#define DATA int
:
:class function
:{
:public:
:	virtual void funcall(DATA i);
:};
:
:virtual void function::funcall(DATA i)
:{
:	printf(" first definition  = %d ", i);
:}
:	
:class function2: public function
:{
:public:
:	virtual void funcall(DATA i) { printf(" redefined = %d ", i); }
:};
:
:class Bug
:{
:	public:
:	void forall(class function f);
:};
:
:void Bug::forall(class function f)
:{
:	f.funcall(1);
:	f.funcall(2);
:}

You have to declare Bug::forall as follows:
	void Bug::forall(function& f);
That is, you have to pass parameter f as a reference to
class function. 

If you pass f by value like you have done here, when
you call Bug::funcall with an object whose class is
derived from function, only class function part of the
object is passed to Bug::funcall and hence, function::funcall()
is called rather than function2::funcall().

That is, the derived class funcall will override the
base class funcall for a virtual function funcall iff
the call is through a pointer or reference to base
class (see ARM pp. 208).

:main()
:{
:	Bug b;
:	function2 f;
:	b.forall(f);
:}