linux-kernel - Re: [PATCH] Clarify error on directive in macro arguments (Re: [PATCH] jffs2: fix sparse errors: directive in argument list)

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Message-ID: <1384740932.5814.4.camel@joe-AO722>
Date:	Sun, 17 Nov 2013 18:15:32 -0800
From:	Joe Perches <joe@...ches.com>
To:	Greg Price <price@....EDU>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Christopher Li <sparse@...isli.org>,
	Erico Nunes <nunes.erico@...il.com>,
	linux-sparse@...r.kernel.org, dwmw2 <dwmw2@...radead.org>,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Clarify error on directive in macro arguments (Re:
 [PATCH] jffs2: fix sparse errors: directive in argument list)

On Sun, 2013-11-17 at 21:07 -0500, Greg Price wrote:
> [+linux-sparse and Chris]
> 
> On Mon, Nov 18, 2013 at 01:33:49AM +0000, Al Viro wrote:
> > On Sun, Nov 17, 2013 at 02:45:05PM -0800, Joe Perches wrote:
> > > Yes.  I think it's a defect in how sparse
> > > treats string concatenation.
> > > 
> > > That style [... with printk ...] is pretty common in the kernel sources.
> > 
> > ... and it's perfectly fine, until somebody starts playing in nasal
> > daemon country and do that in *macro* arguments.  And a nasal daemon
> > country it is - it's an undefined behaviour.  See 6.10.3p11 in C99.
> > And trying to define a semantics for that gets real ugly real fast.
> > sparse matches gcc behaviour (I hope), but it warns about such abuses.
> > It's a defect, all right - one being reported by sparse.
> 
> Perhaps the following tweak to the error message would make this
> subtlety clearer?

Maybe, but this case isn't a macro.  It's a function.
Dunno if differentiating when it's a macro or a
function is difficult though.


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