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From: mwarren@rws1.ma30.bull.com (Mark Warren)
Subject: Problem with access to shared memory
Organization: Bull HN Informations Systems Inc.
Date: 31 May 91 12:23:32 GMT
Message-ID: <mwarren.675692612@rws1>
Sender: @mips2.ma30.bull.com

In Mips RISC/os 4.52, I have a program which allocates shared memory regions,
and would like to have the regions attached RDONLY sometimes, and READ-WRITE
at other times.  Essentially, it does:

	id = shmget(key, size, (IPC_CREAT | 0600));
	addr = shmat(shmid, 0, 0);
	strcpy(addr, "some stuff");
	shmdt(addr);
	addr = shmat(shmid, 0, SHM_RDONLY);
	strcpy(addr, "some other stuff");

I expect the second strcpy to fail with a SIGSEGV or SIGBUS, but instead
it succeeds.  What am I doing wrong?
--

 == Mark Warren                      Bull HN Information Systems Inc. ==
 == (508) 294-3171 (FAX 294-3020)    300 Concord Road     MS836A      ==
 == M.Warren@bull.com                Billerica, MA 01821              ==