Path: utzoo!mnetor!uunet!husc6!cmcl2!nrl-cmf!ames!sri-spam!sri-unix!garth!walter
From: walter@garth.UUCP (Walter Bays)
Newsgroups: comp.lang.c
Subject: Re: Volatile is Necessary
Message-ID: <580@garth.UUCP>
Date: 28 Mar 88 22:10:24 GMT
References: <12578@brl-adm.ARPA> <1988Mar25.172355.348@utzoo.uucp> <8107@sol.ARPA>
Reply-To: walter@garth.UUCP (Walter Bays)
Organization: INTERGRAPH (APD) -- Palo Alto, CA
Lines: 20

In article <8107@sol.ARPA> crowl@cs.rochester.edu (Lawrence Crowl) writes:
>The `volatile' type qualifier of ANSI C has recently been criticized as a
>frill.  While this assertion is arguable for uniprocessors, it is not true for
>shared-memory multiprocessors.  [...] If there is no mechanism to
>indicate when a variable referenced by one process may be modified by
>another process, the compiler must assume that all variables may be
>modified at any time.  [...] This limits the optimizing effectiveness
>of compilers substantially. [...]

The 'volatile' keyword would also work for uniprocessor device
drivers.  How about setjmp()?  Or side effects of functions with
"dangerous" pointers?
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