linux-kernel - Re: [PATCH 6/7] cpufreq: intel

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Date:	Wed, 11 Jun 2014 02:23:27 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Joe Perches <joe@...ches.com>
Cc:	Stratos Karafotis <stratosk@...aphore.gr>,
	Dirk Brandewie <dirk.brandewie@...il.com>,
	dirk.j.brandewie@...el.com, Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] cpufreq: intel_pstate: Trivial code cleanup

On Tuesday, June 10, 2014 02:26:45 PM Joe Perches wrote:
> On Tue, 2014-06-10 at 23:38 +0200, Rafael J. Wysocki wrote:
> 
> > > > is.  And the result of (a * 100) / b may generally be different from
> > > > a * 100 / b for integers (if the division is carried out first).
> > > 
> > > I thought that (a * 100) / b is always equivalent to a * 100 / b.
> > 
> > I'm not actually sure if that's guaranteed by C standards.
> 
> It is.  left to right, same precedence.
> 
> > It surely
> > wasn't some time ago (when there was no formal C standard).
> 
> c89 is 25 years ago now.

Apparently, I'm old.

> > Either way, in my opinion it's better to put the parens into the expression
> > in this particular case to clearly state the intention.
> 
> I don't think so.

Of course, you're free to disagree, but I guess you'll admit that
a * b / c is generally different from b / c * a and if you see something
like this it is hard to say at first sight whether or not this is intentional
or an expression ordering bug.

Rafael

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