* [PATCH] rbd: avoid clang -Wuninitialized warning
@ 2019-03-22 14:36 Arnd Bergmann
2019-03-22 16:34 ` Ilya Dryomov
0 siblings, 1 reply; 4+ messages in thread
From: Arnd Bergmann @ 2019-03-22 14:36 UTC (permalink / raw)
To: Ilya Dryomov, Sage Weil, Alex Elder, Jens Axboe
Cc: clang-built-linux, Nick Desaulniers, Nathan Chancellor,
Arnd Bergmann, Jason Dillaman, ceph-devel, linux-block,
linux-kernel
clang fails to see that rbd_assert(0) ends in an unreachable code
path and warns about a subsequent use of an uninitialized variable
when CONFIG_PROFILE_ANNOTATED_BRANCHES is set:
drivers/block/rbd.c:2402:4: error: variable 'ret' is used uninitialized whenever 'if' condition is false
[-Werror,-Wsometimes-uninitialized]
rbd_assert(0);
^~~~~~~~~~~~~
drivers/block/rbd.c:563:7: note: expanded from macro 'rbd_assert'
if (unlikely(!(expr))) { \
^~~~~~~~~~~~~~~~~
include/linux/compiler.h:48:23: note: expanded from macro 'unlikely'
# define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/block/rbd.c:2410:6: note: uninitialized use occurs here
if (ret) {
^~~
drivers/block/rbd.c:2402:4: note: remove the 'if' if its condition is always true
rbd_assert(0);
^
drivers/block/rbd.c:563:3: note: expanded from macro 'rbd_assert'
if (unlikely(!(expr))) { \
^
drivers/block/rbd.c:2376:9: note: initialize the variable 'ret' to silence this warning
int ret;
^
= 0
1 error generated.
This seems to be a bug in clang, but is easy to work around by using
an unconditional BUG().
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/block/rbd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 4ba967d65cf9..cbcc3baf3807 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2399,7 +2399,7 @@ static int rbd_obj_read_from_parent(struct rbd_obj_request *obj_req)
&obj_req->bvec_pos);
break;
default:
- rbd_assert(0);
+ BUG();
}
} else {
ret = rbd_img_fill_from_bvecs(child_img_req,
--
2.20.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] rbd: avoid clang -Wuninitialized warning
2019-03-22 14:36 [PATCH] rbd: avoid clang -Wuninitialized warning Arnd Bergmann
@ 2019-03-22 16:34 ` Ilya Dryomov
2019-03-22 16:55 ` Arnd Bergmann
0 siblings, 1 reply; 4+ messages in thread
From: Ilya Dryomov @ 2019-03-22 16:34 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Sage Weil, Alex Elder, Jens Axboe, clang-built-linux,
Nick Desaulniers, Nathan Chancellor, Jason Dillaman,
Ceph Development, linux-block, LKML
On Fri, Mar 22, 2019 at 3:36 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> clang fails to see that rbd_assert(0) ends in an unreachable code
> path and warns about a subsequent use of an uninitialized variable
> when CONFIG_PROFILE_ANNOTATED_BRANCHES is set:
>
> drivers/block/rbd.c:2402:4: error: variable 'ret' is used uninitialized whenever 'if' condition is false
> [-Werror,-Wsometimes-uninitialized]
> rbd_assert(0);
> ^~~~~~~~~~~~~
> drivers/block/rbd.c:563:7: note: expanded from macro 'rbd_assert'
> if (unlikely(!(expr))) { \
> ^~~~~~~~~~~~~~~~~
> include/linux/compiler.h:48:23: note: expanded from macro 'unlikely'
> # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/block/rbd.c:2410:6: note: uninitialized use occurs here
> if (ret) {
> ^~~
> drivers/block/rbd.c:2402:4: note: remove the 'if' if its condition is always true
> rbd_assert(0);
> ^
> drivers/block/rbd.c:563:3: note: expanded from macro 'rbd_assert'
> if (unlikely(!(expr))) { \
> ^
> drivers/block/rbd.c:2376:9: note: initialize the variable 'ret' to silence this warning
> int ret;
> ^
> = 0
> 1 error generated.
>
> This seems to be a bug in clang, but is easy to work around by using
> an unconditional BUG().
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/block/rbd.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 4ba967d65cf9..cbcc3baf3807 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -2399,7 +2399,7 @@ static int rbd_obj_read_from_parent(struct rbd_obj_request *obj_req)
> &obj_req->bvec_pos);
> break;
> default:
> - rbd_assert(0);
> + BUG();
> }
> } else {
> ret = rbd_img_fill_from_bvecs(child_img_req,
Hi Arnd,
You did a couple of these last year in commit c6244b3b2377 ("rbd: avoid
Wreturn-type warnings"). Let's change all of those default cases to BUG
in one go. Do you want to do that or should I?
Thanks,
Ilya
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] rbd: avoid clang -Wuninitialized warning
2019-03-22 16:34 ` Ilya Dryomov
@ 2019-03-22 16:55 ` Arnd Bergmann
2019-03-25 11:11 ` Ilya Dryomov
0 siblings, 1 reply; 4+ messages in thread
From: Arnd Bergmann @ 2019-03-22 16:55 UTC (permalink / raw)
To: Ilya Dryomov
Cc: Sage Weil, Alex Elder, Jens Axboe, clang-built-linux,
Nick Desaulniers, Nathan Chancellor, Jason Dillaman,
Ceph Development, linux-block, LKML
On Fri, Mar 22, 2019 at 5:33 PM Ilya Dryomov <idryomov@gmail.com> wrote:
>
> On Fri, Mar 22, 2019 at 3:36 PM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> > index 4ba967d65cf9..cbcc3baf3807 100644
> > --- a/drivers/block/rbd.c
> > +++ b/drivers/block/rbd.c
> > @@ -2399,7 +2399,7 @@ static int rbd_obj_read_from_parent(struct rbd_obj_request *obj_req)
> > &obj_req->bvec_pos);
> > break;
> > default:
> > - rbd_assert(0);
> > + BUG();
> > }
> > } else {
> > ret = rbd_img_fill_from_bvecs(child_img_req,
>
> Hi Arnd,
>
> You did a couple of these last year in commit c6244b3b2377 ("rbd: avoid
> Wreturn-type warnings").
Ah, I had completely forgotten about that. Different bug and different
compiler, but same solution ;-)
> Let's change all of those default cases to BUG
> in one go. Do you want to do that or should I?
I've prepared another patch now and sent it out, please
apply it on top. I'd like this one-line patch to stay separate though
since it captures the warning message and may need to
be backported to stable kernels later.
Arnd
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] rbd: avoid clang -Wuninitialized warning
2019-03-22 16:55 ` Arnd Bergmann
@ 2019-03-25 11:11 ` Ilya Dryomov
0 siblings, 0 replies; 4+ messages in thread
From: Ilya Dryomov @ 2019-03-25 11:11 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Sage Weil, Alex Elder, Jens Axboe, clang-built-linux,
Nick Desaulniers, Nathan Chancellor, Jason Dillaman,
Ceph Development, linux-block, LKML
On Fri, Mar 22, 2019 at 5:55 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Fri, Mar 22, 2019 at 5:33 PM Ilya Dryomov <idryomov@gmail.com> wrote:
> >
> > On Fri, Mar 22, 2019 at 3:36 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > >
> > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> > > index 4ba967d65cf9..cbcc3baf3807 100644
> > > --- a/drivers/block/rbd.c
> > > +++ b/drivers/block/rbd.c
> > > @@ -2399,7 +2399,7 @@ static int rbd_obj_read_from_parent(struct rbd_obj_request *obj_req)
> > > &obj_req->bvec_pos);
> > > break;
> > > default:
> > > - rbd_assert(0);
> > > + BUG();
> > > }
> > > } else {
> > > ret = rbd_img_fill_from_bvecs(child_img_req,
> >
> > Hi Arnd,
> >
> > You did a couple of these last year in commit c6244b3b2377 ("rbd: avoid
> > Wreturn-type warnings").
>
> Ah, I had completely forgotten about that. Different bug and different
> compiler, but same solution ;-)
>
> > Let's change all of those default cases to BUG
> > in one go. Do you want to do that or should I?
>
> I've prepared another patch now and sent it out, please
> apply it on top. I'd like this one-line patch to stay separate though
> since it captures the warning message and may need to
> be backported to stable kernels later.
Applied.
Thanks,
Ilya
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-03-22 14:36 [PATCH] rbd: avoid clang -Wuninitialized warning Arnd Bergmann
2019-03-22 16:34 ` Ilya Dryomov
2019-03-22 16:55 ` Arnd Bergmann
2019-03-25 11:11 ` Ilya Dryomov
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