Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!sdd.hp.com!samsung!munnari.oz.au!ditmela!diemen!tasis.eecs.utas.edu.au!charles
From: charles@tasis.eecs.utas.edu.au (Charles Lakos)
Newsgroups: comp.std.c
Subject: Order of allocation of fields in a struct?
Message-ID: <1563@diemen.cc.utas.oz>
Date: 13 Jun 90 14:00:00 GMT
Sender: news@diemen.cc.utas.oz
Lines: 29

I wonder if the C standard says anything about the order of allocation of 
memory to fields of a struct.  In particular, suppose that I have
  typedef struct {
    int a;  char c;  real b;
  } t1;
  typedef struct {
    int a;  char c;  real b;  something-else d;
  } t2;
  t2 v2, *p
  ...
  p = &v2;  /* set p to point to v2 of type t2 */
Can I then access the fields of v2 in the following way:
  (t1 *) p -> b

If this is not standardised, is it common practice?

(The question interests me from the point of view of implementing object-
oriented languages in C.  Classes could be implemented as struct's and
pointers to the object could be coerced to the relevant type without
problem.)




-----
Charles Lakos                                   charles@tasis.eecs.utas.edu.au
Electrical Engineering & Computer Science
University of Tasmania
Tasmania, Australia.