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Subject: [PATCH] kernel.h: Verify that arguments to swap() are the same type
From: Joe Perches <joe@perches.com>
To: LKML <linux-kernel@vger.kernel.org>
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Date: Wed, 15 Jul 2009 18:34:21 -0700
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Signed-off-by: Joe Perches <joe@perches.com>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d6320a3..72878a5 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -637,8 +637,13 @@ static inline void ftrace_dump(void) { }
 /*
  * swap - swap value of @a and @b
  */
-#define swap(a, b) \
-	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+#define swap(a, b)				\
+do {						\
+	typeof(a) __tmp = (a);			\
+	BUILD_BUG_ON(!__same_type(__tmp, (b)));	\
+	(a) = (b);				\
+	(b) = __tmp;				\
+} while (0)
 
 /**
  * container_of - cast a member of a structure out to the containing structure