Re: [PATCH] rds: send: mark expected switch fall-through in rds_rm_size

[Gustavo A. R. Silva]

Hi Santosh,

On 02/20/2018 11:54 AM, Santosh Shilimkar wrote:
> Hi,
>
> 2/19/2018 10:10 AM, Gustavo A. R. Silva wrote:
> > In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> > where we are expecting to fall through.
> >
> > Addresses-Coverity-ID: 1465362 ("Missing break in switch")
> > Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> > ---
> > Â net/rds/send.c | 2 ++
> > Â 1 file changed, 2 insertions(+)
> >
> > diff --git a/net/rds/send.c b/net/rds/send.c
> > index 028ab59..79d158b 100644
> > --- a/net/rds/send.c
> > +++ b/net/rds/send.c
> > @@ -902,6 +902,8 @@ static int rds_rm_size(struct msghdr *msg, int 
> > num_sgs)
> > ÂÂÂÂÂÂÂÂÂ case RDS_CMSG_ZCOPY_COOKIE:
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ zcopy_cookie = true;
> > +ÂÂÂÂÂÂÂÂÂÂÂ /* fall through */
> > +
> > ÂÂÂÂÂÂÂÂÂ case RDS_CMSG_RDMA_DEST:
> > ÂÂÂÂÂÂÂÂÂ case RDS_CMSG_RDMA_MAP:
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ cmsg_groups |= 2;
> So coverity greps for commet as "fall through" for
> -Wimplicit-fallthrough build ?

No. Basically, Coverity only reports cases in which a break, return or 
continue statement is missing.

Now, if the statements I mention above are missing and if you add the 
following line to your Makefile:

KBUILD_CFLAGS  += $(call cc-option,-Wimplicit-fallthrough)

You will get a warning if a fall-through comment is missing.

> Adding that comments itself if fine but was curious
> about it if some one makes a spell error in this
> comment what happens ;-)

In this case, Coverity would still report the same "Missing break in 
switch" error, but you'll get a GCC warning.

> For patch itself,
> Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>

--
Gustavo