linux-kernel - Re: [PATCH] btrfs: fix uninitialized variable warning

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Message-ID: <fd8bf37e-3481-3607-834b-28805f0b7dc6@suse.com>
Date:   Fri, 24 Mar 2023 12:24:39 +0800
From:   Qu Wenruo <wqu@...e.com>
To:     genjian zhang <zhanggenjian123@...il.com>, dsterba@...e.cz
Cc:     Qu Wenruo <quwenruo.btrfs@....com>, clm@...com,
        josef@...icpanda.com, dsterba@...e.com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Genjian Zhang <zhanggenjian@...inos.cn>,
        k2ci <kernel-bot@...inos.cn>
Subject: Re: [PATCH] btrfs: fix uninitialized variable warning



On 2023/3/24 11:05, genjian zhang wrote:
> On Fri, Mar 24, 2023 at 10:35 AM David Sterba <dsterba@...e.cz> 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@...inos.cn>
>>>>
>>>> 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@...inos.cn>
>>>> Signed-off-by: Genjian Zhang <zhanggenjian@...inos.cn>
>>>> ---
>>>>    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.