linux-kernel - Re: [PATCH] [v2] ceph: fix clang warning for CEPH_DEFINE_OID

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Date:   Wed, 27 Mar 2019 17:33:07 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "Yan, Zheng" <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Alex Elder <elder@...aro.org>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [v2] ceph: fix clang warning for CEPH_DEFINE_OID_ONSTACK

On Mon, Mar 25, 2019 at 1:51 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> clang complains about assigning a variable to itself during the
> declaration:
>
> fs/ceph/ioctl.c:187:26: error: variable 'oid' is uninitialized when used within its own initialization [-Werror,-Wuninitialized]
>         CEPH_DEFINE_OID_ONSTACK(oid);
>                                 ^~~
> include/linux/ceph/osdmap.h:122:52: note: expanded from macro 'CEPH_DEFINE_OID_ONSTACK'
>         struct ceph_object_id oid = CEPH_OID_INIT_ONSTACK(oid)
>                               ~~~                         ^~~
> include/linux/ceph/osdmap.h:120:29: note: expanded from macro 'CEPH_OID_INIT_ONSTACK'
>     ({ ceph_oid_init(&oid); oid; })
>                             ^~~
>
> We use this trick in other places, but it is completely unnecessary
> here, as we can just use a regular struct initializer.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> v2: rearrange to only have one instance of the initializer
> ---
>  include/linux/ceph/osdmap.h | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/ceph/osdmap.h b/include/linux/ceph/osdmap.h
> index 5675b1f09bc5..8794cf0f0b39 100644
> --- a/include/linux/ceph/osdmap.h
> +++ b/include/linux/ceph/osdmap.h
> @@ -110,17 +110,16 @@ struct ceph_object_id {
>         int name_len;
>  };
>
> +#define CEPH_OID_INITIALIZER(oid) { .name = (oid).inline_name }
> +
> +#define CEPH_DEFINE_OID_ONSTACK(oid)                           \
> +       struct ceph_object_id oid = CEPH_OID_INITIALIZER(oid)
> +
>  static inline void ceph_oid_init(struct ceph_object_id *oid)
>  {
> -       oid->name = oid->inline_name;
> -       oid->name_len = 0;
> +       *oid = (struct ceph_object_id)CEPH_OID_INITIALIZER(*oid);
>  }
>
> -#define CEPH_OID_INIT_ONSTACK(oid)                                     \
> -    ({ ceph_oid_init(&oid); oid; })
> -#define CEPH_DEFINE_OID_ONSTACK(oid)                                   \
> -       struct ceph_object_id oid = CEPH_OID_INIT_ONSTACK(oid)
> -
>  static inline bool ceph_oid_empty(const struct ceph_object_id *oid)
>  {
>         return oid->name == oid->inline_name && !oid->name_len;

Applied.

Thanks,

                Ilya