Xref: utzoo comp.lang.c:25921 comp.lang.c++:6472
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From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c,comp.lang.c++
Subject: Re: Using distributive property to optimize.
Message-ID: <15944@haddock.ima.isc.com>
Date: 14 Feb 90 22:02:26 GMT
References: <229@altos86.Altos.COM> <1020.nlhp3@oracle.nl> <94348@linus.UUCP> <15904@haddock.ima.isc.com> <CHUCKP.90Feb13065634@halley.ncr-fc.FtCollins.NCR.com>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Followup-To: comp.lang.c
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 17

In article <CHUCKP.90Feb13065634@halley.ncr-fc.FtCollins.NCR.com> chuckp@ncr-fc.FtCollins.NCR.com (Chuck Phillips) writes:
>Agreed.  In the spirit of C, the compiler _should_, by default, have the
>freedom to rearrange an expression (take advantage of distributivity, etc.).
>However, there are times when you _really need_ to explicitly control the
>order and means of evaluation.

Please describe such a circumstance.  I believe that all such are covered by
the new ANSI C rules%, and hence there is no need for extensions like your
proposed "cast-to-volatile".

Karl W. Z. Heuer (karl@ima.ima.isc.com or harvard!ima!karl), The Walking Lint
Followups to comp.lang.c only; this isn't really C++ related.
________
% Briefly, the rule is that the implementation is permitted to rearrange only
  through the grace of the as-if rule: i.e., only if the result obtained is
  indistinguishable from that of the abstract machine.  Lvalues with the
  "volatile" attribute must be loaded and stored as per the abstract machine.