linux-kernel - Re: checkpatch, a patch checking script.

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Message-Id: <20070502132938.4349a4ed.akpm@linux-foundation.org>
Date:	Wed, 2 May 2007 13:29:38 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Dave Jones <davej@...hat.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: checkpatch, a patch checking script.

On Wed, 2 May 2007 21:55:16 +0200 (CEST)
Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com> wrote:

> On Wed, 2 May 2007, Andrew Morton wrote:
> > On Wed, 2 May 2007 17:32:49 +0200 (CEST)
> > Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com> wrote:
> > 
> > > On Wed, 2 May 2007, Christoph Hellwig wrote:
> > > > On Wed, May 02, 2007 at 04:28:27PM +0200, Geert Uytterhoeven wrote:
> > > > >   - Check for GNU extension __FUNCTION__
> > > > 
> > > > __FUNCTION__ is prefered  over __func__
> > > 
> > > Is there a reason for that?
> > >   - __FUNCTION__ is a GNU extension
> > >   - __func__ is C99
> > >   - __func__ is shorter to type ;-)
> > > 
> > 
> > In that case we should use __func__.
> > 
> > But we discussed this at some length 3-4 years ago and decided to use
> > __FUNCTION__.  I don't remember why.  Perhaps problems with gcc support for
> > __func__?
> 
> I tried gcc 2.95/3.2/3.3/3.4/4.0/4.1, they all recognize __func__ and
> __FUNCTION__, like in e.g. printf("%s", __func__);
> 
> > (It could have been that compile-time string concatenation was involved:
> > 
> > 
> >         printf("xxx" __FILE__);			/* works */
> >         printf("xxx" __FUNCTION__);		/* doesn't */
> > 
> > Or not.)
> 
> Yep, when trying concatenation, I got:
>   - 2.95: works fine
>   - 3.2:
>       syntax error before "__func__"
>       warning: concatenation of string literals with __FUNCTION__ is deprecated
>   - 3.3:
>       error: syntax error before "__func__"
>       warning: concatenation of string literals with __FUNCTION__ is deprecated
>   - 3.4/4.0:
>       error: syntax error before "__func__"
>       error: syntax error before "__FUNCTION__"
>   - 4.1:
>       error: expected ')' before '__func__'
>       error: expected ')' before '__FUNCTION__'
> 
> Hence gcc 3.2 and up treat __func__ like the a variable, as per C99, while
> __FUNCTION__ has been moving from a virtual preprocessor definition in 2.95 to
> a variable, like __func__.
> 
> So in the end it doesn't matter, as concatenation has been fixed in the Linux
> source tree anyway.
> 

Great, thanks for working all that out.

So __func__ it is.  In new code.  However "convert __FUNCTION__ to
__func__" patches will be cheerfully ignored - life is too short.


err, kernel.h has

/* Trap pasters of __FUNCTION__ at compile-time */
#define __FUNCTION__ (__func__)

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