linux-kernel - Re: [PATCH 1/1] checkpatch.pl: thou shalt not use () or (...) in function declarations

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Message-ID: <20120415181847.GB22990@pcarmody2.research.nokia.com>
Date:	Sun, 15 Apr 2012 21:18:47 +0300
From:	Phil Carmody <ext-phil.2.carmody@...ia.com>
To:	ext Jiri Slaby <jslaby@...e.cz>
Cc:	apw@...onical.com, hpa@...or.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] checkpatch.pl: thou shalt not use () or (...) in
 function declarations

On 22/03/12 17:22 +0100, ext Jiri Slaby wrote:
> On 03/22/2012 04:27 PM, Phil Carmody wrote:
> > After HPA's wonderful lkml post, referenced, it seems worth trying to
> > detect this robomatically.
> > 
> > Signed-off-by: Phil Carmody <ext-phil.2.carmody@...ia.com>
> > ---
> >  scripts/checkpatch.pl |    4 ++++
> >  1 files changed, 4 insertions(+), 0 deletions(-)
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index a3b9782..3993011 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -1881,6 +1881,10 @@ sub process {
> >  				substr($ctx, 0, $name_len + 1, '');
> >  				$ctx =~ s/\)[^\)]*$//;
> >  
> > +				if ($ctx =~ /^\s*(?:\.\.\.)?\s*$/) {
> > +					# HPA explains why: http://lwn.net/Articles/487493/
> > +					ERROR("(...) and () are not sufficiently informative function declarations\n$hereline");
> > +				}
> 
> That explanation is not fully correct. C99 explicitly says (6.7.5.3.14):
> An identifier list declares only the identifiers of the parameters of
> the function. An empty list in a function declarator that is part of a
> definition of that function specifies that the function has no
> parameters. The empty list in a function declarator that is not part of
> a definition of that function specifies that no information about the
> number or types of the parameters is supplied.
> 
> So what you are trying to force here holds only for (forward)
> declarations. Not for functions with definitions (bodies). Is checkpatch
> capable to differ between those?

I know I've already agreed to the above, as it makes perfect sense, but 
I've just come across this, and it appears we're both wrong.

http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_317.htm
""""
...
void f(){}
...
Question 1: Does such a function definition give the function a type including a prototype for the rest of the translation unit?
...
Committee Response
The grammar states that an empty parens stands for an empty identifier list not an empty parameter-type-list.
The answer to question #1 is NO
"""

So it appears () is never sufficiently informative.
Phil
-- 
Phil Carmody
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