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

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Date:	Thu, 21 Feb 2008 13:42:56 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	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

>> [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

The commit that introduced __CHECK_ENDIAN__ was
af4ca457eaf2d6682059c18463eb106e2ce58198 ("gfp_t: infrastructure") but
it doesn't say anything about the rationale for it.

> When I enabled __CHECK_ENDIAN I got:
> 8 files with > 100 warnings
> 14 files with 10 to 99 warnings.
> 
> So nothing that should scare a kernel hacker...
> 
> warnings without: 1686
> warnings with: 2788
> 
> OK - thats a lot, but then fixing 8 files will significantly
> reduce this.

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...

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...)

johannes

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