Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!husc6!necntc!cullvax!drw
From: drw@cullvax.UUCP (Dale Worley)
Newsgroups: comp.unix.wizards,comp.lang.c
Subject: Incorrect subtraction in C program
Message-ID: <1242@cullvax.UUCP>
Date: Wed, 3-Jun-87 18:07:42 EDT
Article-I.D.: cullvax.1242
Posted: Wed Jun  3 18:07:42 1987
Date-Received: Sun, 7-Jun-87 04:02:12 EDT
Organization: Cullinet Software, Westwood, MA, USA
Lines: 20
Xref: mnetor comp.unix.wizards:2591 comp.lang.c:2334

jwp@uwmacc.UUCP (Jeffrey W Percival) writes:
> I have a problem I have distilled down into a short C program.
> The problem is that when I subtract a tiny number from 1,
> I get 1 (the right answer) on a VAX 780 running 4.3BSD, but
> I get 0 (the wrong answer) on a MicroVAX running 4.3BSD.  Here's
> the program:

This may have to do with the fact that the code in BSD that simulates
the VAX instructions that the uVAX hardware doesn't have has problems
with it.  If you have VMS on a uVAX also, use the debuggers to see if
the floating subtract instructions produce different results on the
two OS's from the same arguments.  (There's someone out in netland who
knows more about this.)

Dale
-- 
Dale Worley		Cullinet Software
UUCP: ...!seismo!harvard!mit-eddie!cullvax!drw
ARPA: cullvax!drw@eddie.mit.edu
Un*x (a generic name for a class of OS's) != Unix (AT&T's brand of such)