linux-kernel - [PATCH 1/4] compiler.h: introduce unused

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Date:	Wed, 25 Apr 2012 15:26:23 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc:	linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 1/4] compiler.h: introduce unused_expression() macro

Sometimes we want to check some expressions correctness in compile-time without
generating extra code. "(void)(e)" does not work if expression has side-effects.
This patch introduces macro unused_expression() which helps in this situation.

Cast to "long" required because sizeof does not work for bit-fields.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
---
 include/linux/compiler.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 923d093..46fbda3 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -310,4 +310,6 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
  */
 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
 
+#define unused_expression(e) ((void)(sizeof((__force long)(e))))
+
 #endif /* __LINUX_COMPILER_H */

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