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

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Date:   Sun, 12 Apr 2020 13:04:29 +0800
From:   Qu Wenruo <quwenruo.btrfs@....com>
To:     Tang Bin <tangbin@...s.chinamobile.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



On 2020/4/12 上午11:21, Tang Bin wrote:
> 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 prebuild tool chain is still using outdated GCC.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

That's pretty old.

You'd better fetch the newer version, as newer kernel may require higher
version gcc.

Or even build your own using tools like buildroot.

Thanks,
Qu

> 
>>
>> 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
> 
>>
>>
> 
> 



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