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

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Date:	Wed, 2 May 2007 21:55:16 +0200 (CEST)
From:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
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, 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.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- Sony Network and Software Technology Center Europe (NSCE)
Geert.Uytterhoeven@...ycom.com ------- The Corporate Village, Da Vincilaan 7-D1
Voice +32-2-7008453 Fax +32-2-7008622 ---------------- B-1935 Zaventem, Belgium
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