Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!hao!boulder!sunybcs!bingvaxu!leah!itsgw!batcomputer!cornell!uw-beaver!tikal!sigma!uw-nsr!john
From: john@uw-nsr.UUCP (John Sambrook)
Newsgroups: comp.unix.questions
Subject: Re: Stack Direction -- Any War Stories?
Message-ID: <1187@uw-nsr.UUCP>
Date: 28 Dec 87 02:02:28 GMT
References: <205@ksr.UUCP>
Reply-To: john@uw-nsr.UUCP (John Sambrook 548-4386)
Organization: UW-Bioengineering, Seattle, WA
Lines: 31

In article <205@ksr.UUCP> benson@ksr.UUCP () writes:
>What machines have Unix stacks that grow up rather than down?

The stacks on the Data General MV series computers grow towards high memory.

>Has anyone any war stories of porting an application across a stack
>direction boundary and having it break due to pointer magnitude comparisons
>or other difficulties?

When I ported XLISP I had to modify one statement due to the direction of
stack growth, but finding and repairing the problem didn't take too long, 
maybe half an hour.  The use of the varargs facility would have prevented
this problem, if memory serves.

I've found a couple of `dangling reference' bugs in code ported to the DG
system.  Some of these bugs have been difficult to find in that you don't
expect them because the code works on many systems.  Pathalias 1.6 had such
a bug that apparently only manifested itself on the DG MV and the ATT 3B
series of computers.

Note that these types of problems are darn near impossible to find unless
you have access to a fairly wide range of different machines to port your
code to. 

>Benson I. Margulies                         Kendall Square Research Corp.
>harvard!ksr!benson			    ksr!benson@harvard.harvard.edu



-- 
John Sambrook                        Internet: john@nsr.bioeng.washington.edu
University of Washington RC-05           UUCP: uw-nsr!john
Seattle, Washington  98195               Dial: (206) 548-4386