Re: [PATCH 11/28] block: rdb: false-postive gcc-4.9 -Wmaybe-uninitialized

Ilya Dryomov
2016-10-18T09:57:37Z

On Tue, Oct 18, 2016 at 12:10 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> When building with gcc-4.9 -Wmaybe-uninitialized, we get a bogus
> warning in rbd_watch_cb, as the variable is not used at all
> in the one case in which it is not initialized first:
>
> drivers/block/rbd.c: In function ‘rbd_watch_cb’:
> drivers/block/rbd.c:3690:5: error: ‘struct_v’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> drivers/block/rbd.c:3759:5: note: ‘struct_v’ was declared here
>
> Later compiler versions fix this, but adding another initialization
> here is harmless and lets us build cleanly with 4.9 as well.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/block/rbd.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index abb7162..4ab990b 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -3776,6 +3776,7 @@ static void rbd_watch_cb(void *arg, u64 notify_id, u64 cookie,
> } else {
> /* legacy notification for header updates */
> notify_op = RBD_NOTIFY_OP_HEADER_UPDATE;
> + struct_v = 0;
> len = 0;
> }

It already got silenced by initializing at declaration in one of the
downstream trees, so I'd rather we do

@@ -3756,7 +3819,7 @@ static void rbd_watch_cb(void *arg, u64
notify_id, u64 cookie,
struct rbd_device *rbd_dev = arg;
void *p = data;
void *const end = p + data_len;
- u8 struct_v;
+ u8 struct_v = 0;
u32 len;
u32 notify_op;
int ret;

to reduce the churn.

The "block" prefix is redundant and "rdb" should be "rbd" in the subject.

Thanks,

Ilya