🚀 go-pugleaf

One use for dereferencing null pointers leaps to mind.  Consider this
definition, used in Intrinsics-based widgets in the X Window System:


Copyright 1987, 1988 by Digital Equipment Corporation, Maynard,
Massachusetts, and the Massachusetts Institute of Technology,
Cambridge, Massachusetts. All Rights Reserved.

#define XtOffset(type,field) \
        ((unsigned int) (((char *) (&(((type)NULL)->field))) - \
                         ((char *) NULL)))



It's used to calculate offsets into the elements of a struct, as
in this snippet from a fictional wristWatch widget:

static XtResource Resources[] = 
{
  { XtNwatchFaceColor,
      XtCFaceColor,
      XtRString,
      sizeof(char *), 
      XtOffset(GIWristWatchWidget, watch.face_color),
      XtRImmediate,
      "White"
  },
....


Can anyone else think of a situation where null dereferencing is
useful, besides compile-time calculation of offsets?


Rod
--
---------------------------------------------------------------------
 __  __
|__)(__'  Don't worry about not seeing the top....
|  \___)               _    o   
                        -_ -\>
                          -_<\
                            -_
                              -_
              ...so much as seeing the bottom.

Roderick Sprattling                      DialCom:  8*833-7054

sprattlingrl@crd.ge.com	                 rls@onondaga.crd.ge.com
uunet!crd.ge.com!sprattlingrl

---------------------------------------------------------------------