linux-kernel - Re: [PATCH] btrfs: Fix backref.c selftest compilation warning

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Message-ID: <4b1e57b3-ca0d-f3e0-f4c4-72cdfe943d7a@cmss.chinamobile.com>
Date:   Sun, 12 Apr 2020 11:21:31 +0800
From:   Tang Bin <tangbin@...s.chinamobile.com>
To:     Qu Wenruo <quwenruo.btrfs@....com>, clm@...com,
        josef@...icpanda.com, dsterba@...e.com
Cc:     linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: Fix backref.c selftest compilation warning

Hi Qu:

On 2020/4/12 8:52, Qu Wenruo wrote:
>
> On 2020/4/11 下午11:49, Tang Bin wrote:
>> Fix missing braces compilation warning in the ARM
>> compiler environment:
>>      fs/btrfs/backref.c: In function ‘is_shared_data_backref’:
>>      fs/btrfs/backref.c:394:9: warning: missing braces around initializer [-Wmissing-braces]
>>        struct prelim_ref target = {0};
>>      fs/btrfs/backref.c:394:9: warning: (near initialization for ‘target.rbnode’) [-Wmissing-braces]
> GCC version please.
>
> It looks like you're using an older GCC, as it's pretty common certain
> prebuild tool chain is still using outdated GCC.
>
> In my environment with GCC 9.2.0 natively (on aarch64) it's completely fine.
> Thus personally I recommend to build your own tool chain using
> buildroot, or run it natively, other than rely on prebuilt one.

My environment:

   PC : Ubuntu 16.04

   Hardware : I.MX6ULL

   Tool Chain : arm-linux-gnueabihf-gcc (Linaro GCC 4.9-2017.01) 4.9.4

>
> In fact your fix could cause problem, as the original code is
> initializing all members to 0, but now it's uninitialized.
>
> You need to locate the root cause other than blindly follow the warning.

In hardware experiment, this approach is feasible.

Thanks.

Tang Bin

>
>