libobjc/nil_method.c

/* GNU Objective C Runtime nil receiver function
   Copyright (C) 1993, 1995, 1996, 2002, 2009, 2010
   Free Software Foundation, Inc.
   Contributed by Kresten Krab Thorup

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */


/* This is the nil method, the function that is called when the receiver
   of a method is nil */

#include "objc-private/common.h"
#include "objc/objc.h"

/* When the receiver of a method invocation is nil, the runtime
   returns nil_method() as the method implementation.  This function
   will be casted to whatever function was supposed to be executed to
   execute that method (that function will take an id, followed by a
   SEL, followed by who knows what arguments, depends on the method),
   and executed.
   
   For this reason, nil_method() should be a function which can be
   called in place of any function taking an 'id' argument followed by
   a 'SEL' argument, followed by zero, or one, or any number of
   arguments (both a fixed number, or a variable number !).
   
   There is no "proper" implementation of such a nil_method function
   in C, however in all existing implementations it does not matter
   when extra arguments are present, so we can simply create a function
   taking a receiver and a selector, and all other arguments will be
   ignored. :-)
*/

id
nil_method (id receiver, SEL op __attribute__ ((__unused__)))
{
  return receiver;
}