linux-kernel - [PATCH] saner typechecking in generic unaligned.h

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Message-Id: <E1IAhoN-0001ij-Ry@ZenIV.linux.org.uk>
Date:	Tue, 17 Jul 2007 08:49:35 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: [PATCH] saner typechecking in generic unaligned.h


Verify that types would match for assignment (under sizeof, so we are safe from
side effects or any code actually getting generated), then explicitly cast
everywhere to the fixed-sized types.  Kills a bunch of bogus warnings about
constants being truncated (gcc, sparse), finds a pile of endianness problems
hidden by old noise (sparse).

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 include/asm-generic/unaligned.h |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/asm-generic/unaligned.h b/include/asm-generic/unaligned.h
index 09ec447..16a466e 100644
--- a/include/asm-generic/unaligned.h
+++ b/include/asm-generic/unaligned.h
@@ -18,7 +18,8 @@
 #define get_unaligned(ptr) \
 	__get_unaligned((ptr), sizeof(*(ptr)))
 #define put_unaligned(x,ptr) \
-	__put_unaligned((__u64)(x), (ptr), sizeof(*(ptr)))
+	((void)sizeof(*(ptr)=(x)),\
+	__put_unaligned((__force __u64)(x), (ptr), sizeof(*(ptr))))
 
 /*
  * This function doesn't actually exist.  The idea is that when
@@ -95,21 +96,21 @@ static inline void __ustw(__u16 val, __u16 *addr)
 	default:				\
 		bad_unaligned_access_length();	\
 	};					\
-	(__typeof__(*(ptr)))val;		\
+	(__force __typeof__(*(ptr)))val;	\
 })
 
 #define __put_unaligned(val, ptr, size)		\
-do {						\
+({						\
 	void *__gu_p = ptr;			\
 	switch (size) {				\
 	case 1:					\
-		*(__u8 *)__gu_p = val;		\
+		*(__u8 *)__gu_p = (__force __u8)val;		\
 	        break;				\
 	case 2:					\
-		__ustw(val, __gu_p);		\
+		__ustw((__force __u16)val, __gu_p);		\
 		break;				\
 	case 4:					\
-		__ustl(val, __gu_p);		\
+		__ustl((__force __u32)val, __gu_p);		\
 		break;				\
 	case 8:					\
 		__ustq(val, __gu_p);		\
@@ -117,6 +118,7 @@ do {						\
 	default:				\
 	    	bad_unaligned_access_length();	\
 	};					\
-} while(0)
+	(void)0;				\
+})
 
 #endif /* _ASM_GENERIC_UNALIGNED_H */
-- 
1.5.3.GIT


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