linux-kernel - Re: slab.h debugging tags....

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Message-ID: <87pp0n96fi.fsf@rasmusvillemoes.dk>
Date:	Fri, 09 Oct 2015 21:40:33 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Valdis Kletnieks <Valdis.Kletnieks@...edu>
Cc:	Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: slab.h debugging tags....

On Fri, Oct 09 2015, Valdis Kletnieks <Valdis.Kletnieks@...edu> wrote:

> Author: Rasmus Villemoes <linux@...musvillemoes.dk>
> Date:   Wed Oct 7 15:09:20 2015 +1100
>
>     slab.h: sprinkle __assume_aligned attributes
>
> causes *tons* of whinges if you do 'make C=2' with sparse 0.5.0:
>
>   CHECK   drivers/media/usb/pwc/pwc-if.c
> include/linux/slab.h:307:43: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:308:58: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:337:73: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:375:74: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:378:80: error: attribute '__assume_aligned__': unknown attribute
>
> [/usr/src/linux-next] grep CHECK build.default | wc
>    1779    3558   59132
> [/usr/src/linux-next] grep slab.h build.default | wc
>    7225   43350  621350
>
> Canned it after about 1/3 of the build.
>
> Where's a sparse that can handle this?

I don't think there is any (sparse 0.5 seems to be the latest). Hm,
if I'm reading the sparse source correctly, it is pretending to be
whatever gcc version it itself is built with. That's... um... let's just
say odd.

Does this fix it for you?

Subject: [PATCH] slab.h: hide assume_aligned attribute from sparse

sparse apparently pretends to be gcc >= 4.9, yet isn't prepared to
handle all the function attributes supported by those gccs and
complains loudly. So hide the definition of __assume_aligned from it
(so that the generic one in compiler.h gets used).

Reported-by: Valdis Kletnieks <Valdis.Kletnieks@...edu>
Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 include/linux/compiler-gcc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 18606a460baf..dc13ceeef8c8 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -211,7 +211,7 @@
 #endif
 
 
-#if GCC_VERSION >= 40900
+#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
 /*
  * __assume_aligned(n, k): Tell the optimizer that the returned
  * pointer can be assumed to be k modulo n. The second argument is
--
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