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From: rpw3@amdcad.UUCP
Newsgroups: comp.arch,comp.lang.c
Subject: Re: Optimization vs. the programmer
Message-ID: <16014@amdcad.AMD.COM>
Date: Tue, 7-Apr-87 22:12:43 EST
Article-I.D.: amdcad.16014
Posted: Tue Apr  7 22:12:43 1987
Date-Received: Sat, 11-Apr-87 03:34:45 EST
References: <479@danews.ATT.COM>
Reply-To: rpw3@amdcad.UUCP (Rob Warnock)
Distribution: world
Organization: [Consultant] San Mateo, CA
Lines: 26
Xref: utgpu comp.arch:810 comp.lang.c:1515
Summary: Use "volatile" when needed

In article <479@danews.ATT.COM> lvc@danews.ATT.COM (Larry Cipriani) writes:
+---------------
| There is a certain computer (that I still use) that requires the statement:
| 	n = n;
| in order to force the hardware to work right for certain values of n...
| If I had an optimizing compiler that was smart (?$!?) enough to excise this
| I couldn't make the machine work right.
+---------------

I can't agree. Instead, *tell* the compiler that you need to do this.
In ANSI C (or any useful optimizing C compiler), simply say:

	volatile int n;
	...
	n = n;

And the compiler will *always* fetch & store "n" when referenced.


Rob Warnock
Systems Architecture Consultant

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