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From: boyd@necisa.ho.necisa.oz (Boyd Roberts)
Newsgroups: comp.unix.wizards
Subject: Re: shared memory
Keywords: portability
Message-ID: <1210@necisa.ho.necisa.oz>
Date: 13 Dec 89 00:02:52 GMT
References: <11383@csli.Stanford.EDU>
Organization: NEC Information Systems Australia Pty. Ltd.
Lines: 24

In article <11383@csli.Stanford.EDU> poser@csli.Stanford.EDU (Bill Poser) writes:
>
>Am I correct in concluding that one simply cannot use shared memory
>portably for large objects or if one may need to allocate large amounts
>of ordinary memory dynamically?

Yes.  I think it's widely acknowledged that the Sys V inter-process
communication hooks are real crocks, particularly shared memory.

Any given shared memory implementation has major problems when it
comes to portability due to the reliance on the underlying architecture
of the machine.  The best you can hope for is a statement that clearly
defines what shared memory services are _guaranteed_.  That way you
can be fairly certain that your code will port well.  But, System V
gives no such assurances.

Anyway, using shared memory is a grody hack.  As someone one said:

    ``Don't diddle the code.  Choose a better algorithm.''


Boyd Roberts			boyd@necisa.ho.necisa.oz.au

``I've got reality backed up on this magtape -- in tar format''