linux-kernel - Re: [PATCH] byteswap: don't use __builtin

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Message-ID: <2133648.lb1RCaYlXp@wuerfel>
Date:	Thu, 11 Aug 2016 13:55:48 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-sparse@...r.kernel.org,
	Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH] byteswap: don't use __builtin_bswap*() with sparse

On Thursday, August 11, 2016 1:15:02 PM CEST Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
> 
> Although sparse declares __builtin_bswap*(), it can't actually
> do constant folding inside them (yet). As such, things like
> 
>   switch (protocol) {
>   case htons(ETH_P_IP):
>           break;
>   }
> 
> which we do all over the place cause sparse to warn that it
> expects a constant instead of a function call.
> 
> Disable __HAVE_BUILTIN_BSWAP*__ if __CHECKER__ is defined to
> avoid this.
> 
> Cc: Arnd Bergmann <arnd@...db.de>
> Fixes: 7322dd755e7d ("byteswap: try to avoid __builtin_constant_p gcc bug")
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>

Looks good, thanks for addressing this!

Acked-by: Arnd Bergmann <arnd@...db.de>