Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!kchen
From: kchen@Apple.COM (Kok Chen)
Newsgroups: comp.lang.c
Subject: Re: assigning an integer to ...
Message-ID: <22581@apple.Apple.COM>
Date: 20 Dec 88 17:25:04 GMT
References: <1911@pembina.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 25

In article <1911@pembina.UUCP> lake@alberta.UUCP (Robert Lake) writes:
>		int i;
>		short j = 1;
>		i = -(unsigned short)j;
>If I run this program on a VAX 11/780 using 4.3 BSD, I obtain -1 as the
>answer.  However, if I run this on a SUN using SUN OS 3.5, I obtain 65535
>as the answer.  Who is right?  ...

From K&R-I, arithmetic operators (including unary ones) are supposed to 
work on longs, no? I would have compiled the line of code into:

		load j
		sign extend to a long
		negate
		(cast to type of i)
		store i

This means BSD is the more correct one, based on K&R-I.

But, why would one have written such a contorted line of code in real life?
Or, is this yet another attempt at breaking compilers? :-)


Kok Chen			{decwrl,sun}!apple!kchen
Apple Computer, Inc.