linux-kernel - Re: [PATCH 06/68] 0 -> NULL, for arch/frv

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Date:	Wed, 1 Aug 2007 15:28:15 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Richard Knutsson <ricknu-0@...dent.ltu.se>
Cc:	Mike Frysinger <vapier.adi@...il.com>,
	Robin Getz <rgetz@...ckfin.uclinux.org>,
	Yoann Padioleau <padator@...adoo.fr>,
	David Howells <dhowells@...hat.com>,
	kernel-janitors@...r.kernel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/68] 0 -> NULL, for arch/frv

On Wed, Aug 01, 2007 at 12:38:39PM +0200, Richard Knutsson wrote:
> Mike Frysinger wrote:
> >On 7/31/07, Richard Knutsson <ricknu-0@...dent.ltu.se> wrote:
> >  
> >>Mike Frysinger wrote:
> >>    
> >>>On 7/27/07, Robin Getz <rgetz@...ckfin.uclinux.org> wrote:
> >>>      
> >>>>If there is a definite style or semantic preference that everyone 
> >>>>should live
> >>>>with - does it make sense to put checks in checkpatch.pl to enforce it?
> >>>>        
> >>>checkpatch.pl does not have enough semantic knowledge to know if the
> >>>thing being tested is a pointer ... dont know if the sparse utility
> >>>would be able to pick it out as i'm not familiar with what level that
> >>>thing runs at
> >>>      
> >>Didn't he mean "x == NULL" > "!x"?
> >>    
> >
> >i'm sure i understand your meaning of ">" ... are you saying that "x
> >== NULL" is greater (preferred) to "!x" or are you saying that "x ==
> >NULL" should be changed to "!x" ?
> >  
> If I understood Robin correctly, he suggested that checkpatch.pl would 
> tell to convert "x == NULL" to "!x", if that would be the preferred way.
> >i dont think the former case can be checked by checkpatch.pl, but the
> >latter certainly can ... but i'd be very skeptical you could get the
> >wider LKML audience to sign off one way or the other wrt to "x ==
> >NULL" vs "!x".  you can certainly get people to sign off on "x == 0"
> >being wrong when x is a pointer.
> >  
> I agree!
> BTW, too bad checkpatch.pl does not know the types, since it otherwise 
> could check for the "x [=!]= 0"-thing.

About the only place that if (x != 0) is preferred to if (x) is cases
where the 0 value doesn't semantically correspond to false/off/disabled.
And that's basically thing that return 0 for success and negative errors.

-- 
Mathematics is the supreme nostalgia of our time.
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