Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!hp-pcd!hpfcso!mjs
From: mjs@hpfcso.FC.HP.COM (Marc Sabatella)
Newsgroups: comp.sys.hp
Subject: Re: HP-UX 8.0: memory mapped files?
Message-ID: <7370391@hpfcso.FC.HP.COM>
Date: 8 May 91 19:26:37 GMT
References: <1991Apr25.092827@ead.dsa.com>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 25

/ hpfcso:comp.sys.hp / vandys@sequent.com (Andrew Valencia) / 10:57 pm  May  3, 1991 /

>But how are OS
>maintainers going to get their grey hair if you guys don't go out and
>monkey with the unsupported interfaces? :-)

Gee, thanks, Andy!  OK, he and other observant posters are right, there is
an entry point for mmap, which we can't prevent you from calling :-)

>If somebody goes for it, please post and tell us if they found whether
>read/write is coherent with the mmap'ed region or not.  I'd just love
>to know how far they got.

You can't write to an mmap'ed file at all - PROT_WRITE only works with
MAP_PRIVATE (ie, copy on write), so coherency isn't a problem.  Well, I suppose
someone could write to the file through normal means, although they'd have to
do it over NFS or they'd get ETXTBUSY.  As I said, mmap() is in place for
shared libraries only, and using mmap() to write the file was not required, so
it isn't implemented.

--------------
Marc Sabatella (marc@hpmonk.fc.hp.com)
Disclaimers:
	2 + 2 = 3, for suitably small values of 2
	Bill and Dave may not always agree with me