linux-kernel - Re: [PATCH 2/2] serial: cascade needless conditionals

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Message-ID: <20091025183939.GB10898@khazad-dum.debian.net>
Date:	Sun, 25 Oct 2009 16:39:39 -0200
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	André Goddard Rosa <andre.goddard@...il.com>
Cc:	gregkh@...e.de, alan@...ux.intel.com,
	Andrew Morton <akpm@...ux-foundation.org>, adobriyan@...il.com,
	linux list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] serial: cascade needless conditionals

On Sun, 25 Oct 2009, André Goddard Rosa wrote:
> On 10/25/09, Henrique de Moraes Holschuh <hmh@....eng.br> wrote:
> > On Sun, 25 Oct 2009, André Goddard Rosa wrote:
> >>  	if (flags == UPF_SPD_HI)
> >>  		altbaud = 57600;
> >> -	if (flags == UPF_SPD_VHI)
> >> +	else if (flags == UPF_SPD_VHI)
> >>  		altbaud = 115200;
> >> -	if (flags == UPF_SPD_SHI)
> >> +	else if (flags == UPF_SPD_SHI)
> >>  		altbaud = 230400;
> >> -	if (flags == UPF_SPD_WARP)
> >> +	else if (flags == UPF_SPD_WARP)
> >>  		altbaud = 460800;
> >
> > This changes code behaviour if more than one bit is set (which might never
> > happen for all I know...).  You should invert the order of the tests if you
> > want to make sure it is side-effect-free.
> 
> Do you mind explaining why? Notice that it's not (var & flag), it's =='.
> Can flags be equal more than one flag at the same time?

No, I obviously am going through coffee withdrawal :(  Sorry about this.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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