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From: mitt@hpclisp.HP.COM (Roy Mittendorff)
Newsgroups: comp.lang.c
Subject: Re: Useful macro...or dangerous??
Message-ID: <660006@hpclisp.HP.COM>
Date: 29 Apr 88 23:24:20 GMT
References: <221@raunvis.UUCP>
Organization: HP NSG/ISD Computer Language Lab
Lines: 25

/ pablo@polygen.uucp (Pablo Halpern) /  6:04 pm  Apr 28, 1988 /

> This would work ONLY IF THERE ARE NO HOLES IN THE STRUCTURES BEING COMPARED.
> For example, the following would not work on many architectures.
>
> 	struct {
> 		char	c;
> 		int	i;
> 	} x, y;
> 	...
> 	if (EQ(&x, &y))
> 		...;
> 
> On many machines, x.i and y.i will be aligned on word boundaries (i.e.,
> they must have addresses that are multiples of the word size, typically
> 2, 4, or 8).  That means that there could be a gap or "hole" of several
> bytes between the end of x.c and the beginning of x.i. ...

   Is there any guarantee that members of structs be stored in any
   particular order?  For example, could c and i may be reversed in 
   some implementations?

> Pablo Halpern

   Roy Mittendorff.