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Path: utzoo!decvax!tektronix!hplabs!sdcrdcf!trwrb!scgvaxd!wlbr!jplgodo!smeagol!earle
From: earle@smeagol.UUCP (Greg Earle)
Newsgroups: net.bugs.4bsd,net.news.b
Subject: Re: Limits on 4.2BSD lseek(2)?
Message-ID: <718@smeagol.UUCP>
Date: Fri, 16-May-86 01:06:31 EDT
Article-I.D.: smeagol.718
Posted: Fri May 16 01:06:31 1986
Date-Received: Mon, 19-May-86 01:17:43 EDT
References: <717@smeagol.UUCP>
Distribution: na
Organization: JPL, Pasadena CA
Lines: 57
Keywords: lseek  "Netnews 2.10.3 4.3bsd-beta 6/6/85"
Summary: WHOOPS!  It wasn't lseek [der ralph!] ; bitten by word alignment

In article <717@smeagol.UUCP>, earle@smeagol.UUCP I wrote:
> In the Netnews 2.10.3 4.3bsd-beta 6/6/85 distibution, there is a program
> called article (written by Peter Honeyman, down!honey) that comes in
> the `misc' directory.  This program will take an article message ID
> (like 1052@ellie, 1424@lll-crg, etc.), look it up in the dbm version
> of the news history file, and if it finds it, will print out the
> first pathname it finds for the article (if it was cross-posted), by 
> fetching the line containing the article ID from the history file.

[ Example omitted ]

> The problem I have found, is that more often than not, the program will
> blow up on a Bus Error.  This happens on a Sun 2-120 workstation, running
> Sun OS 2.0 (4.2BSD based).  The cause of this Bus Error is an execution
> of lseek(2).

No it's not, idiot ...

> I am finding that it retrieves some articles with no problem, but most of
> them are gagging with the accompaning Bus Error.

Like the guy at the school crossing once said:
	Look both ways before posting.

I got bitten by the Famous 680x0 long-pointer-must-be-word-aligned
problem ...

The program blows up when the pointer value in the datum that is returned
by fetch() is odd; i.e. not word aligned.  When interpreted as a (long *)
and dereferenced, gag city ...

Thanks to voder!jeff for pointing this out just as I was realizing it myself.

That's what I get for not being a dbm expert, & forgetting Machine Dependencies
to boot :-(

Hopefully this will get out before I get too much "Geez, what a MAROON" mail.

BTW, the fix:

Add a 
	long fpos;
declaration to main, and before the lseek insert

        /* The bcopy is NECESSARY to insure alignment on some machines */
        bcopy(content.dptr, (char *)&fpos, sizeof (long));

This is from the file funcs2.c, function findhist(); in the 2.10.3 4.3bsd-beta
Netnews distribution.

Again, my apologies for the original posting.  Oh well, maybe some of you
got a good laugh out of it, so ...
-- 
	Greg Earle	UUCP: sdcrdcf!smeagol!earle; (new!!) attmail!earle
	JPL		ARPA: elroy!smeagol!earle@csvax.caltech.edu

Hello, GORRY-O!!  I'm a GENIUS from HARVARD!!