From owner-freebsd-questions  Fri Sep 24 13:33:28 1999
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Date: Fri, 24 Sep 1999 16:18:15 -0400 (EDT)
From: Zhihui Zhang <zzhang@cs.binghamton.edu>
To: Alfred Perlstein <bright@wintelcom.net>
Cc: freebsd-questions@FreeBSD.ORG
Subject: Re: A program that causes "bus error"
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On Fri, 24 Sep 1999, Alfred Perlstein wrote:

> 
> On Fri, 24 Sep 1999, Zhihui Zhang wrote:
> 
> > 
> > The following program causes "bus error" on a Sun workstation whether I
> > compile it with cc or gcc:
> > 
> > #include <stdio.h>
> > main()
> > {
> > 	union { 
> > 		char a[10]; int i;
> > 	} u;
> > 	int * p = (int *) &(u.a[1]);
> > 	 * p = 17;
> > 	printf("%d\n", *p);
> > }
> 
> You are violating sparc's alignment restrictions by doing this,
> a x86 machine will deal with the alignment issues in hardware however
> a sparc will trap to the OS (SIGBUS) if non-aligned accesses are
> attempted.
> 

Thanks. This code is taken from the book "Expert C Programming - Deep C
Secrets".  It is a good book. The auther must be very familiar with SunOS. 

-Zhihui



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