linux-kernel - Re: [PROBLEM] make randconfig: fs/btrfs/ref-verify.c:500:16: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

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Date: Thu, 27 Jun 2024 22:02:51 +0200
From: Mirsad Todorovac <mtodorovac69@...il.com>
To: Filipe Manana <fdmanana@...nel.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 Linux Kernel Build System <linux-kbuild@...r.kernel.org>,
 Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
 David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org
Subject: Re: [PROBLEM] make randconfig: fs/btrfs/ref-verify.c:500:16: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

On 6/27/24 20:11, Filipe Manana wrote:
> On Thu, Jun 27, 2024 at 7:07 PM Mirsad Todorovac <mtodorovac69@...il.com> wrote:
>>
>> Hi all,
>>
>> After following Boris' advice in https://lore.kernel.org/lkml/20240404134142.GCZg6uFh_ZSzUFLChd@fat_crate.local/
>> on using the randconfig test, this is the second catch:
>>
>> KCONFIG_SEED=0xEE80059C
>>
>> marvin@...iant:~/linux/kernel/linux_torvalds$ time nice make -j 36 bindeb-pkg |& tee ../err-6.10-rc5-05a.log; date
>>   GEN     debian
>> dpkg-buildpackage --build=binary --no-pre-clean --unsigned-changes -R'make -f debian/rules' -j1 -a$(cat debian/arch)
>> dpkg-buildpackage: info: source package linux-upstream
>> dpkg-buildpackage: info: source version 6.10.0-rc5-gafcd48134c58-27
>> dpkg-buildpackage: info: source distribution jammy
>> dpkg-buildpackage: info: source changed by marvin <marvin@...iant>
>> dpkg-architecture: warning: specified GNU system type i686-linux-gnu does not match CC system type x86_64-linux-gnu, try setting a correct CC environment variable
>>  dpkg-source --before-build .
>> dpkg-buildpackage: info: host architecture i386
>>  make -f debian/rules binary
>> #
>> # No change to .config
>> #
>>   CALL    scripts/checksyscalls.sh
>>   UPD     init/utsversion-tmp.h
>>   CC      init/version.o
>>   AR      init/built-in.a
>>   CHK     kernel/kheaders_data.tar.xz
>>   CC [M]  fs/btrfs/ref-verify.o
>>   AR      fs/built-in.a
>> fs/btrfs/ref-verify.c: In function ‘process_extent_item.isra’:
>> fs/btrfs/ref-verify.c:500:16: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>>   500 |         return ret;
>>       |                ^~~
>> cc1: all warnings being treated as errors
>> make[7]: *** [scripts/Makefile.build:244: fs/btrfs/ref-verify.o] Error 1
>> make[6]: *** [scripts/Makefile.build:485: fs/btrfs] Error 2
>> make[5]: *** [scripts/Makefile.build:485: fs] Error 2
>> make[4]: *** [Makefile:1934: .] Error 2
>> make[3]: *** [debian/rules:74: build-arch] Error 2
>> dpkg-buildpackage: error: make -f debian/rules binary subprocess returned exit status 2
>> make[2]: *** [scripts/Makefile.package:121: bindeb-pkg] Error 2
>> make[1]: *** [/home/marvin/linux/kernel/linux_torvalds/Makefile:1555: bindeb-pkg] Error 2
>> make: *** [Makefile:240: __sub-make] Error 2
>>
>> real    0m2.583s
>> user    0m9.943s
>> sys     0m5.607s
>> Thu Jun 27 19:14:55 CEST 2024
>> marvin@...iant:~/linux/kernel/linux_torvalds$
>>
>> This fix does nothing to the algorithm, but it silences compiler -Werror=maybe-uninitialised
> 
> You've reported this before, and there's a fix [1] for it in the
> btrfs' github repo, for-next branch. It's not yet in Linus' tree.
> 
> [1] https://lore.kernel.org/linux-btrfs/612bf950d478214e8b76bdd7c22dd6a991337b15.1719143259.git.fdmanana@suse.com/

Yes, this is correct. It is somewhat hard to follow all the possible trees ...

>> ---
>> diff --git a/fs/btrfs/ref-verify.c b/fs/btrfs/ref-verify.c
>> index cf531255ab76..0b5ff30e2d81 100644
>> --- a/fs/btrfs/ref-verify.c
>> +++ b/fs/btrfs/ref-verify.c
>> @@ -459,6 +459,8 @@ static int process_extent_item(struct btrfs_fs_info *fs_info,
>>                 iref = (struct btrfs_extent_inline_ref *)(ei + 1);
>>         }
>>
>> +       ret = -EINVAL;
>> +
> 
> This is not correct.
> This would result in failure if we have an extent item without any
> inline references (only keyed references following the extent item).

I see.

> Thanks.

No big deal. Many people do not like warnings in compilation and use -Werror ...

Glad I could be of use.

Best regards,
Mirsad Todorovac

>>         ptr = (unsigned long)iref;
>>         end = (unsigned long)ei + item_size;
>>         while (ptr < end) {
>> ---
>>
>> Hope this helps.
>>
>> Best regards,
>> Mirsad Todorovac
>>