[RESEND] drbd: avoid clang warning about pointless switch statement

Message ID 20181002171447.10765-1-natechancellor@gmail.com
State New
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  • [RESEND] drbd: avoid clang warning about pointless switch statement
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Commit Message

Nathan Chancellor Oct. 2, 2018, 5:14 p.m.
From: Arnd Bergmann <arnd@arndb.de>


The drbd code causes warnings that we cannot easily disable when building with clang:

In file included from drivers/block/drbd/drbd_debugfs.c:10:
In file included from drivers/block/drbd/drbd_int.h:48:
In file included from include/linux/drbd_genl_api.h:53:
In file included from include/linux/genl_magic_struct.h:237:
include/linux/drbd_genl.h:300:1: warning: no case matching constant switch condition '0'

There is nothing wrong with the code, and adding 'default:' labels
in the right place is enough to let clang shut up about the warning.

Fixes: ec2c35ac1ea2 ("drbd: prepare the transition from connector to genetlink")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

---

This was recently resent by Philipp Klocke but the attribution on it
was incorrect (had Arnd's signoff but no From: line) and linux-block
wasn't cc'd, who presumably should take this patch since this file was
introduced by commit ec2c35ac1ea2 ("drbd: prepare the transition from
connector to genetlink"). If that is the case, perhaps these files
should be added to the drbd MAINTAINERS entry since they were introduced
by drbd and have been the only consumers since; I'd be happy to send a
patch if others agree.

It was acked by Lars on https://lore.kernel.org/patchwork/patch/756723/
so I don't know if this patch should carry

Acked-by: Lars Ellenberg <lars.ellenberg@linbit.com>


or not. I'll leave that up to the maintainer to decide.

Thanks!
Nathan

 include/linux/genl_magic_struct.h | 3 +++
 1 file changed, 3 insertions(+)

-- 
2.19.0

Comments

Lars Ellenberg Oct. 4, 2018, 7:18 p.m. | #1
On Tue, Oct 02, 2018 at 10:14:48AM -0700, Nathan Chancellor wrote:
> From: Arnd Bergmann <arnd@arndb.de>

> 

> The drbd code causes warnings that we cannot easily disable when building with clang:

> 

> In file included from drivers/block/drbd/drbd_debugfs.c:10:

> In file included from drivers/block/drbd/drbd_int.h:48:

> In file included from include/linux/drbd_genl_api.h:53:

> In file included from include/linux/genl_magic_struct.h:237:

> include/linux/drbd_genl.h:300:1: warning: no case matching constant switch condition '0'

> 

> There is nothing wrong with the code, and adding 'default:' labels

> in the right place is enough to let clang shut up about the warning.


Actually, I think I'd prefer a "case 0:" instead of the "default:",
because that would assert that we don't use a 0 for op or field numbers.

As at least some people seem to care, I suggest we bundle up
this and the other clang warning you just resent the patch for
with whatever else we may come up with for the next merge window
and send a pull request to Jens then.
In case we forget, please send a friendly reminder.

Thanks,

    Lars
Nathan Chancellor Oct. 4, 2018, 7:22 p.m. | #2
On Thu, Oct 04, 2018 at 09:18:54PM +0200, Lars Ellenberg wrote:
> On Tue, Oct 02, 2018 at 10:14:48AM -0700, Nathan Chancellor wrote:

> > From: Arnd Bergmann <arnd@arndb.de>

> > 

> > The drbd code causes warnings that we cannot easily disable when building with clang:

> > 

> > In file included from drivers/block/drbd/drbd_debugfs.c:10:

> > In file included from drivers/block/drbd/drbd_int.h:48:

> > In file included from include/linux/drbd_genl_api.h:53:

> > In file included from include/linux/genl_magic_struct.h:237:

> > include/linux/drbd_genl.h:300:1: warning: no case matching constant switch condition '0'

> > 

> > There is nothing wrong with the code, and adding 'default:' labels

> > in the right place is enough to let clang shut up about the warning.

> 

> Actually, I think I'd prefer a "case 0:" instead of the "default:",

> because that would assert that we don't use a 0 for op or field numbers.

> 

> As at least some people seem to care, I suggest we bundle up

> this and the other clang warning you just resent the patch for

> with whatever else we may come up with for the next merge window

> and send a pull request to Jens then.

> In case we forget, please send a friendly reminder.

> 

> Thanks,

> 

>     Lars

> 


Hi Lars,

I will go ahead and test that change shortly and send it over for
review.

Thanks for the quick reply!
Nathan

Patch

diff --git a/include/linux/genl_magic_struct.h b/include/linux/genl_magic_struct.h
index 5972e4969197..c11f42179c63 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
+	default:
 		;
 	}
 }
@@ -209,6 +210,7 @@  static inline void ct_assert_unique_top_level_attributes(void)
 {
 	switch (0) {
 #include GENL_MAGIC_INCLUDE_FILE
+	default:
 		;
 	}
 }
@@ -219,6 +221,7 @@  static inline void ct_assert_unique_ ## s_name ## _attributes(void)	\
 {									\
 	switch (0) {							\
 		s_fields						\
+		default:						\
 			;						\
 	}								\
 }