Date: Sun, 12 May 2002 00:37:05 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: Dag-Erling Smorgrav <des@ofug.org> Cc: hiten@uk.FreeBSD.org, current@FreeBSD.org Subject: Re: alpha tinderbox failure Message-ID: <20020511213704.GF16174@hades.hell.gr> In-Reply-To: <xzpy9eqzlqz.fsf@flood.ping.uio.no> References: <20020511161441.GA1568@hpdi.ath.cx> <xzpy9eqzlqz.fsf@flood.ping.uio.no>
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On 2002-05-11 18:34, Dag-Erling Smorgrav wrote:
> Hiten Pandya <hiten@uk.FreeBSD.org> writes:
> > /*
> > * A comment is probably needed here for those not
> > * well versed in the "C" language. Yes, this is
> > * supposed to be a "switch" with the body of the
> > * "switch" being a "while" statement. The whole
> > * purpose of the switch is to allow us to jump into
> > * the middle of the while() loop, and then not have
> > * to do any more switch()s.
> > *
> > * Some compilers will spit out a warning message
> > * about the loop not being entered at the top.
> > */
> > switch (n&03)
> > while (n > 0) {
> > case 0:
> > ck ^= (int)*d++ << 24;
> > --n;
> > case 3:
> > ck ^= (int)*d++ << 16;
> > --n;
> > case 2:
> > ck ^= (int)*d++ << 8;
> > --n;
> > case 1:
> > ck ^= (int)*d++;
> > --n;
> > }
> > return(ck);
>
> Hmm, does this mean Duff's Device is not valid C?
It is ugly. I'm not sure if it's non-standard too. My impression
until now was that jumping from an outter block 'inside' a contained
block is not a Good Thing(TM). Note that the switch cases also lack a
'break' and are falling through. All of them!
This makes me wonder that happens the second time the loop runs. Does
the code start the second iteration at the beginning of the while
body? Or does it start at where the loop was entered the first time
(the proper 'case' of the switch statement)?
- Giorgos
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