Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!hplabs!hp-sdd!ucsdhub!jack!sdeggo!dave
From: dave@sdeggo.UUCP (David L. Smith)
Newsgroups: comp.unix.microport
Subject: Re: shared memory??
Message-ID: <183@sdeggo.UUCP>
Date: 18 Mar 88 19:32:24 GMT
References: <259@bby-bc.UUCP>
Organization: Lazy Programmer's Society of San Diego
Lines: 30

In article <259@bby-bc.UUCP>, john@bby-bc.UUCP (john) writes:
> I'm trying to use shared memory to access a frame buffer and it
> doesn't seem to work. I am running 2.2L.  I put the appropriate
> shmcreate lines in /etc/rc.d/shm.rc but when my program runs
> nothing seems to happen (I check for error returns and from
> shmat and shmget but no error indication is given).  to check it out
> I tried the tiny programbelow to try and write some high intensity
> "A"'s to the herc. mono adapter.  The program runs in a couple of seconds
> but nothing changes on the screens.  The only thing I have noticed is
> that in  system5.nm  shmat() is listed as an int rather than a char *

Well, your program is correct, I compiled and ran it on 'eggo without any
problems (well, it gives a core dump at the end, but that's not your problem
just yet).

There's two things to check for:  On older version of 2.2, the shmcreate
program did not attach the segments properly.  You can check to see if
the segments exist with the ipcs program.  I think the problem showed up
with the segments being "r--r--r--" protected.  Maybe you can talk Microport
into giving you a version that works.  You may also want to make sure
that you are running the "large" kernel, since the one that is installed
by the installation procedure does not have any of the shared memory
routines.


-- 
David L. Smith
{sdcsvax!jack,ihnp4!jack, hp-sdd!crash, pyramid, uport}!sdeggo!dave
sdeggo!dave@amos.ling.edu 
Sinners can repent, but stupid is forever.