Re: [PATCH] btrfs: fix uninitialized variable warning

[Qu Wenruo]

On 2023/3/24 11:05, genjian zhang wrote:
> On Fri, Mar 24, 2023 at 10:35 AM David Sterba <dsterba@xxxxxxx> wrote:
> > On Fri, Mar 24, 2023 at 10:24:55AM +0800, Qu Wenruo wrote:
> > > On 2023/3/24 10:08, Genjian wrote:
> > > > From: Genjian Zhang <zhanggenjian@xxxxxxxxxx>
> > > >
> > > > compiler warning:
> > >
> > > Compiler version please.
> > >
> > > > ../fs/btrfs/volumes.c: In function ‘btrfs_init_new_device’:
> > > > ../fs/btrfs/volumes.c:2703:3: error: ‘seed_devices’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > > >    2703 |   btrfs_setup_sprout(fs_info, seed_devices);
> > > >         |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >
> > > > ../fs/btrfs/send.c: In function ‘get_cur_inode_state’:
> > > > ../include/linux/compiler.h:70:32: error: ‘right_gen’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > > >      70 |   (__if_trace.miss_hit[1]++,1) :  \
> > > >         |                                ^
> > > > ../fs/btrfs/send.c:1878:6: note: ‘right_gen’ was declared here
> > > >    1878 |  u64 right_gen;
> > > >         |      ^~~~~~~~~
> > > >
> > > > Initialize the uninitialized variables.
> > > >
> > > > Reported-by: k2ci <kernel-bot@xxxxxxxxxx>
> > > > Signed-off-by: Genjian Zhang <zhanggenjian@xxxxxxxxxx>
> > > > ---
> > > >    fs/btrfs/send.c    | 2 +-
> > > >    fs/btrfs/volumes.c | 2 +-
> > > >    2 files changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> > > > index e5c963bb873d..af2e153543a5 100644
> > > > --- a/fs/btrfs/send.c
> > > > +++ b/fs/btrfs/send.c
> > > > @@ -1875,7 +1875,7 @@ static int get_cur_inode_state(struct send_ctx *sctx, u64 ino, u64 gen,
> > > >      int left_ret;
> > > >      int right_ret;
> > > >      u64 left_gen;
> > > > -   u64 right_gen;
> > > > +   u64 right_gen = 0;
> > >
> > > IIRC this is not my first time explaining why this is a false alert.
> > >
> > > Thus please report your compiler version first.
> >
> > This is probably because of the -Wmaybe-uninitialized we enabled, on
> > some combination of architecture and compiler. While I'm also interested
> > in the compiler and version we need to fix the warnings before 6.3 final.
> > We'd be gettting the warnings and reports/patches, which is wasting
> > peoples' time, it's not a big deal to initialize the variables. But
> > still I also want to know which version reports that.
>
> aarch64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110 and
> aarch64-linux-gnu-gcc (7.3.0-20190804.h30.ky10.aarch64 )

Latest GCC 10.x is already 10.3, and 7.x is already 7.5.

Either report to your distro and let them update the toolchain, or find 
a way to make your bot shut up on the false alert.

> Thanks,
>
> Genjian.