linux-kernel - [PATCH] m32r: fix build warning

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Date:   Sat, 14 Jan 2017 22:24:24 +0000
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH] m32r: fix build warning

Some m32r builds were having a warning:

arch/m32r/include/asm/cmpxchg.h:191:3:
	warning: value computed is not used


arch/m32r/include/asm/cmpxchg.h:68:3:
	warning: value computed is not used

Taking the idea from e001bbae7147 ("ARM: cmpxchg: avoid warnings from
macro-ized cmpxchg() implementations") the m32r implementation is
changed to use a similar construct with a compound expression instead
of a typecast, which causes the compiler to not complain about an
unused result.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
---
 arch/m32r/include/asm/cmpxchg.h | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/m32r/include/asm/cmpxchg.h b/arch/m32r/include/asm/cmpxchg.h
index 14bf9b7..23c9d05 100644
--- a/arch/m32r/include/asm/cmpxchg.h
+++ b/arch/m32r/include/asm/cmpxchg.h
@@ -64,8 +64,10 @@
 	return (tmp);
 }
 
-#define xchg(ptr, x)							\
-	((__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
+#define xchg(ptr, x) ({							\
+	((__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr),		\
+				    sizeof(*(ptr))));			\
+})
 
 static __always_inline unsigned long
 __xchg_local(unsigned long x, volatile void *ptr, int size)
@@ -187,9 +189,12 @@
 	return old;
 }
 
-#define cmpxchg(ptr, o, n)						 \
-	((__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)(o),	 \
-			(unsigned long)(n), sizeof(*(ptr))))
+#define cmpxchg(ptr, o, n) ({				\
+	((__typeof__(*(ptr)))				\
+		 __cmpxchg((ptr), (unsigned long)(o),	\
+			   (unsigned long)(n),		\
+			   sizeof(*(ptr))));		\
+})
 
 #include <asm-generic/cmpxchg-local.h>
 
-- 
1.9.1