linux-kernel - Re: [PATCH] mac80211: check endianness/types in sparse runs

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Date:	Thu, 21 Feb 2008 12:01:31 -0800
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	John Linville <linville@...driver.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Stefano Brivio <stefano.brivio@...imi.it>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mac80211: check endianness/types in sparse runs

On Thu, 2008-02-21 at 13:42 +0100, Johannes Berg wrote:
> >> [patch doing CHECKFLAGS += -D__CHECK_ENDIAN__ in the
> >> net/mac80211/Makefile]
> 
> > I would prefer it to be kernel wide enabled.
> > Tried a defconfig build.
> 
> Hm. I tend to think there was a reason for this, since this is actually
> explicitly disabled by include/linux/types.h:
> 
> #ifdef __CHECKER__
> #define __bitwise__ __attribute__((bitwise))
> #else 
> #define __bitwise__
> #endif
> 
> #ifdef __CHECK_ENDIAN__
> #define __bitwise __bitwise__
> #else
> #define __bitwise
> #endif
> 

This seems somewhat suspect.

> I recently ran sparse on my config and was surprised by the number of
> warnings. Then again, something in mmzone.h or so generated billions of
> them...

Potentially expensive pointer subtraction 640:....

Patch in -mm.

> 
> In any case, I would love to have __CHECK_ENDIAN__ enabled by default at
> least on the wireless code (just caught another bug with it...)
> 

I'd love to have it too, but there are so many trivial warnings that
clutter up valid warnings that it is prohibitive.  I'm working on
reducing the noise level a bit for 2.6.26, we'll see about turning
it on then.

Harvey

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