linux-kernel - Re: [PATCH] staging: lustre: shut up clang warnings on CLASSERT()

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Date:   Thu, 2 Feb 2017 10:54:53 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Dilger, Andreas" <andreas.dilger@...el.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "Drokin, Oleg" <oleg.drokin@...el.com>,
        James Simmons <jsimmons@...radead.org>,
        "Eremin, Dmitry" <dmitry.eremin@...el.com>,
        Lustre Development List <lustre-devel@...ts.lustre.org>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] staging: lustre: shut up clang warnings on CLASSERT()

On Thu, Feb 02, 2017 at 07:50:24AM +0000, Dilger, Andreas wrote:
> On Feb 1, 2017, at 09:52, Arnd Bergmann <arnd@...db.de> wrote:
> > 
> > lustre uses a fake switch() statement as a compile-time assert, but unfortunately
> > each use of that causes a warning when building with clang:
> > 
> > drivers/staging/lustre/lnet/klnds/socklnd/socklnd.c:2907:2: warning: no case matching constant switch condition '42'
> > drivers/staging/lustre/lnet/klnds/socklnd/../../../include/linux/libcfs/libcfs_private.h:294:36: note: expanded from macro 'CLASSERT'
> > #define CLASSERT(cond) do {switch (42) {case (cond): case 0: break; } } while (0)
> > 
> > Adding a 'default:' label in there shuts up the warning.
> > 
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> Reviewed-by: Andreas Dilger <andreas.dilger@...el.com>
> 
> > ---
> > drivers/staging/lustre/include/linux/libcfs/libcfs_private.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h b/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> > index aab15d8112a4..2d5435029185 100644
> > --- a/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> > +++ b/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> > @@ -291,7 +291,7 @@ do {							    \
> >  *       value  after  conversion...
> >  *
> >  */
> > -#define CLASSERT(cond) do {switch (42) {case (cond): case 0: break; } } while (0)
> > +#define CLASSERT(cond) do {switch (42) {case (cond): case 0: default: break; } } while (0)

Ugh, why not just use the in-kernel ASSERT macro instead?

thanks,

greg k-h