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From: notes@hcx1.UUCP
Newsgroups: comp.unix.questions
Subject: Sys V shared mem ??
Message-ID: <123@hcx1.UUCP>
Date: Thu, 13-Nov-86 18:09:43 EST
Article-I.D.: hcx1.123
Posted: Thu Nov 13 18:09:43 1986
Date-Received: Sat, 15-Nov-86 05:05:03 EST
Sender: notes@hcx1.UUCP
Organization: Harris CSD, Fort Lauderdale, Florida
Lines: 25
Nf-ID: #N:hcx1:48200001:000:786
Nf-From: hcx1!gwp    Nov 13 18:08:00 1986


I have a question concerning System V.2 and shared memory.  It appears
(and I may be wrong) possible to do a shared memory attach into your
data region (we have System V source in house and I can't find any
checks that prevent this) . That is something like:

   int shmid, shmflg;
   char buf[1024];
   .
   .
   (get shmid, set shmflg, etc.)
   .
   .
   shmat (shmid, buf, shflg);

   and access the shared memory segemnt as buf[n].  The reason for doing
something like this is to save one indirection over the normal method
of just letting shmat() return a pointer the shared memory segment.

   My question is: What happens to the original contents of buf and
all the data objects declared after it ?
--------
Gil Pilz                                 ...!allegra!novavax!hcx1!gwp