Re: [PATCH v2] drbd: Avoid Clang warning about pointless switch statment

Jens Axboe
2018-12-17T17:29:48Z

On 12/17/18 10:24 AM, Nathan Chancellor wrote:
> On Thu, Oct 04, 2018 at 01:09:13PM -0700, Nathan Chancellor wrote:
>> 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@linbit.com>
>> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
>> ---
>>
>> Since this is not the same as Arnd's patch, I took authorship for it
>> while leaving a link to the original patch in the commit message. If
>> this is not how it should have been done, please let me know.
>>
>> 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: \
>> ; \
>> } \
>> }
>> --
>> 2.19.0
>>
>
> Hi Lars and Philipp,
>
> Could you please make sure that this patch and the other one I sent make
> it into 4.21/5.0? I am not sure when you were planning on sending the
> pull request to Jens that you mentioned in the other thread but I've
> noticed most maintainers typically send their requests for the impending
> merge window around -rc7 or so and I wanted to make sure it was on your
> radar.

It needs to get here now, but drbd hasn't really sent anything in for
about a year, so I'm starting to doubt how maintained it is at this
point.

--
Jens Axboe