1  /* GNU Objective C Runtime nil receiver function
       2     Copyright (C) 1993-2023 Free Software Foundation, Inc.
       3     Contributed by Kresten Krab Thorup
       4  
       5  This file is part of GCC.
       6  
       7  GCC is free software; you can redistribute it and/or modify it under the
       8  terms of the GNU General Public License as published by the Free Software
       9  Foundation; either version 3, or (at your option) any later version.
      10  
      11  GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      12  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
      13  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
      14  details.
      15  
      16  Under Section 7 of GPL version 3, you are granted additional
      17  permissions described in the GCC Runtime Library Exception, version
      18  3.1, as published by the Free Software Foundation.
      19  
      20  You should have received a copy of the GNU General Public License and
      21  a copy of the GCC Runtime Library Exception along with this program;
      22  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23  <http://www.gnu.org/licenses/>.  */
      24  
      25  
      26  /* This is the nil method, the function that is called when the receiver
      27     of a method is nil */
      28  
      29  #include "objc-private/common.h"
      30  #include "objc/objc.h"
      31  
      32  /* When the receiver of a method invocation is nil, the runtime
      33     returns nil_method() as the method implementation.  This function
      34     will be casted to whatever function was supposed to be executed to
      35     execute that method (that function will take an id, followed by a
      36     SEL, followed by who knows what arguments, depends on the method),
      37     and executed.
      38     
      39     For this reason, nil_method() should be a function which can be
      40     called in place of any function taking an 'id' argument followed by
      41     a 'SEL' argument, followed by zero, or one, or any number of
      42     arguments (both a fixed number, or a variable number !).
      43     
      44     There is no "proper" implementation of such a nil_method function
      45     in C, however in all existing implementations it does not matter
      46     when extra arguments are present, so we can simply create a function
      47     taking a receiver and a selector, and all other arguments will be
      48     ignored. :-)
      49  */
      50  
      51  id
      52  nil_method (id receiver, SEL op __attribute__ ((__unused__)))
      53  {
      54    return receiver;
      55  }