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Date:	Wed, 20 Jun 2001 12:23:13 -0400
From:	"Charles S. Wilson" <cwilson AT ece DOT gatech DOT edu>
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To:	Brian Michael Genisio <genisiob AT pilot DOT msu DOT edu>
CC:	cygwin AT sources DOT redhat DOT com
Subject:	Re: cygipc does not seem to work!!!
References:	<200106191932 DOT f5JJWm532232 AT pilot14 DOT cl DOT msu DOT edu>

Note that Brian has already contacted me (as the cygipc maintainer) -- 
but I'm at a loss.  So I referred him here.  It looks like an 
ownership/permissions problem, but I really don't understand the 
underlying windows IPC mechanisms on which cygipc was based, so I'm not 
sure about how permissions are handled.  (I didn't write cygipc; I just 
saved it from death on the net and put in on my web page).

Here's a thought: Brian, you're not using the '--tight-security' option 
with the background ipc-daemon process, are you?

--Chuck

Brian Michael Genisio wrote:

> Hello Cygwin people,
> 
> I am trying to get a very simple shared memory application to work.  It works
> find in linux and solaris, but in cygwin... no luck.
> 
> I create the memory and attach to it with :
> shmid = shmget(IPC_PRIVATE, 100, IPC_CREAT|0777);
> strp = (char *)shmat(shmid, 0, 0);
> 
> The other app gets the shmid through stdout, and through a command arg.  It
> opens it with :
> strp = (char *)shmat(shmid, 0, 0);
> 
> The problem is that the second application cannot open the shared memory until
> the first application has terminated!!!  Once it does, it can read the memory
> with no problem.  Unfortunately, it is difficult for them to communicate when
> the first program has already exited.
> 
> I have tested it by starting the creator program, and running ipcs.  ipcs does
> not recognize the memory either, until the program has exited.
> 
> Any ideas?  Has anyone else gotten it to work?  Shared memory isnt that
> difficult... and I am not sure why I am having this problem.
> 
> Thanks,
> Brian
> 
> 
> 
> 
> 
> --
> ---------------------------
>       \\|//   Brian Genisio
>       (o o)        genisiob AT pilot DOT msu DOT edu
> ~~oOOo~(_)~oOOo~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> 
> 
> 
> 
> --
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