Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!umd5!cvl!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: volatile
Message-ID: <10914@mimsy.UUCP>
Date: 4 Apr 88 05:20:51 GMT
References: <12578@brl-adm.ARPA> <1988Mar25.172355.348@utzoo.uucp> <18686@think.UUCP> <4217@ihlpf.ATT.COM>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26

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-In article <9176@tut.cis.ohio-state.edu> lvc@tut.cis.ohio-state.edu
-(Lawrence V. Cipriani) writes:
->	volatile int customer_changeable_var = 0;
->	if (customer_chageable_var != 0)
->[without something like volatile] the compiler would be free to
->optimize out the "impossible" code.

In article <18686@think.UUCP> barmar@think.COM (Barry Margolin) writes:
-I don't think volatile is necessary for the above example.

and in article <4217@ihlpf.ATT.COM> nevin1@ihlpf.ATT.COM (00704a-Liber)
writes:
-The compiler would *not* be free to optimize out this code!!  Because
-customer_changeable_var is EXTERNAL to main(), this optimization cannot
-occur.

lvc is right; barmar and nevin1 are wrong.  Remember, compilation
need not take place until after everything is linked together.
Admittedly there are few (possibly no) compilers which would make
this `optimisation' today.  I expect this to change in the near
future.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris