Date: Fri, 17 Sep 1999 18:33:48 +1000 From: Patryk Zadarnowski <patrykz@mycenae.ilion.eu.org> To: Gregory Bond <gnb@itga.com.au> Cc: hackers@FreeBSD.ORG Subject: Re: "style" question Message-ID: <199909170833.SAA55426@mycenae.ilion.eu.org> In-Reply-To: Your message of "Fri, 17 Sep 1999 18:21:35 %2B1000." <199909170821.SAA15276@lightning.itga.com.au>
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> I'm looking at cleaning up a few compile nits and I'm wondering what the
> officially approved way of silencing "may not be used" warnings:
>
> int
> foo(int flag)
> {
> int j;
>
> if (flag)
> j = 1;
>
> /*
> * This noop statement is enough to confuse the optimiser so it
> * forgets that j is initialised iff flag != 0
> */
> flag = !!flag;
I don't know about the "official" way to silence the compiler (a well
placed else statement or a "default" switch case usually does the
trick for me) That is to say, I'm willing to argue that fixing the
flow of control is the only clean way of getting rid of these
warnings, unless you know something special about the allowed values
of the offending variable (eg. you know that your switch case is
exhaustive), in which case a dummy "default" or initializer cannot
hurt you much.
Also !!x IS NOT a noop. For example, !!5 == 1. I think you meant to
say `flag = ~~flag', which indeed is a NOP.
Pat.
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