From:	Andrew Crabtree <andrewc AT typhoon DOT rose DOT hp DOT com>
Message-Id:	<199711131747.AA236333222@typhoon.rose.hp.com>
Subject:	Re: Port of bzip2
To:	eliz AT is DOT elta DOT co DOT il (Eli Zaretskii)
Date:	Thu, 13 Nov 1997 9:47:02 PST
Cc:	djgpp AT delorie DOT com
In-Reply-To:	<Pine.SUN.3.91.971113130719.23653C-100000@is>; from "Eli Zaretskii" at Nov 13, 97 1:13 pm
Reply-To:	andrewc AT rosemail DOT rose DOT hp DOT com

 
> AFAIK, there's no such thing as SIGBUS on machines which don't require 
> alignment.  x86 can handle misaligned objects, they just inflict runtime  
> penalty.  Machines that have SIGBUS cannot access misaligned objects at 
> all.
Not sure here.  I think the pentium (at least) and above have
this capability.  I doubt its enabled in most (any?) cases though.

From 'Pentium Processor User's Manual Volume 3'
Page 14-24 (edited for length by yours truly)

14.9.16. Interrupt 17 - Alignment Check

An alignment-check fault can be generated for access to unaligned operands.
For example, a word stored at an odd byte address, or a doubleword
stored at an address which is not an integer multiple of four ....
To enable alignment checking, the following conditions myst be true:

^ AM bit in the CR0 register is set
^ AC flag is set
^ CPL is 3 (user mode)


 
> A better way is to check SIGBUS itself:
 
> Here, also, a better way is to test for the (un)supported feature rather 
> than for a system name:

Of course.  Right on both counts.  I have a tendency to do the 
quick and dirty fix.  I will send off your changes to the 
maintainer.

Andy


--
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           /                       	                  Andrew Crabtree 
          /                          	      Workgroup Networks Division 
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        /     /    /    /   		                    Roseville, CA 
     __/   __/    _____/                                     916/785-1675
                 /                           andrewc AT rosemail DOT rose DOT hp DOT com
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