Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: volatile
Message-ID: <11531@mimsy.UUCP>
Date: 17 May 88 10:52:26 GMT
References: <20345@pyramid.pyramid.com> <502@wsccs.UUCP> <51431@sun.uucp> <526@wsccs.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 21

In article <526@wsccs.UUCP> terry@wsccs.UUCP (Every system needs one) writes:
>Why can't the compiler figure out what is volitile and
>THEN optimize without being hit over the head?

In many cases it can.  This is one of several reasonably good arguments
against volatile.  One pro-volatile (or #pragma) counterargument is that
it helps the reader to realise that there is something unusual going on
here too---not that this cannot be done with a comment.

>>Compiler technology is getting really good, and we need a way to tell
>>the optimisers that strange things can happen.

>If it's sooooo advanced, it could determine volatility (or aliasing)
>without me having to tell it.

Could and should: I agree.  But (as dmr put it) the nice thing about
`volatile' is that the average programmer can ignore it; this was
not true of `noalias'.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris