linux-kernel - [PATCH 16/17] drbd: Avoid Clang warning about pointless switch statment

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Date:   Thu, 20 Dec 2018 17:23:43 +0100
From:   Lars Ellenberg <lars.ellenberg@...bit.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org
Cc:     drbd-dev@...ts.linbit.com
Subject: [PATCH 16/17] drbd: Avoid Clang warning about pointless switch statment

From: Nathan Chancellor <natechancellor@...il.com>

There are several warnings from Clang about no case statement matching
the constant 0:

In file included from drivers/block/drbd/drbd_receiver.c:48:
In file included from drivers/block/drbd/drbd_int.h:48:
In file included from ./include/linux/drbd_genl_api.h:54:
In file included from ./include/linux/genl_magic_struct.h:236:
./include/linux/drbd_genl.h:321:1: warning: no case matching constant
switch condition '0'
GENL_struct(DRBD_NLA_HELPER, 24, drbd_helper_info,
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/genl_magic_struct.h:220:10: note: expanded from macro
'GENL_struct'
        switch (0) {
                ^

Silence this warning by adding a 'case 0:' statement. Additionally,
adjust the alignment of the statements in the ct_assert_unique macro to
avoid a checkpatch warning.

This solution was originally sent by Arnd Bergmann with a default case
statement: https://lore.kernel.org/patchwork/patch/756723/

Link: https://github.com/ClangBuiltLinux/linux/issues/43
Suggested-by: Lars Ellenberg <lars.ellenberg@...bit.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 include/linux/genl_magic_struct.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/genl_magic_struct.h b/include/linux/genl_magic_struct.h
index 5972e4969197..eeae59d3ceb7 100644
--- a/include/linux/genl_magic_struct.h
+++ b/include/linux/genl_magic_struct.h
@@ -191,6 +191,7 @@ static inline void ct_assert_unique_operations(void)
 {
 	switch (0) {
 #include GENL_MAGIC_INCLUDE_FILE
+	case 0:
 		;
 	}
 }
@@ -209,6 +210,7 @@ static inline void ct_assert_unique_top_level_attributes(void)
 {
 	switch (0) {
 #include GENL_MAGIC_INCLUDE_FILE
+	case 0:
 		;
 	}
 }
@@ -218,7 +220,8 @@ static inline void ct_assert_unique_top_level_attributes(void)
 static inline void ct_assert_unique_ ## s_name ## _attributes(void)	\
 {									\
 	switch (0) {							\
-		s_fields						\
+	s_fields							\
+	case 0:								\
 			;						\
 	}								\
 }
-- 
2.17.1