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Subject: Re: [PATCH] Clarify error on directive in macro arguments (Re:
 [PATCH] jffs2: fix sparse errors: directive in argument list)
From: Joe Perches <joe@perches.com>
To: Greg Price <price@MIT.EDU>
Date: Sun, 17 Nov 2013 18:15:32 -0800
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Cc: Christopher Li <sparse@chrisli.org>,
 linux-kernel <linux-kernel@vger.kernel.org>, linux-sparse@vger.kernel.org,
 linux-mtd <linux-mtd@lists.infradead.org>, Al Viro <viro@ZenIV.linux.org.uk>,
 dwmw2 <dwmw2@infradead.org>, Erico Nunes <nunes.erico@gmail.com>
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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.