linux-kernel - [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 19:36:23 +0200
From: Mirsad Todorovac <mtodorovac69@...il.com>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: 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: [PROBLEM] make randconfig: fs/btrfs/ref-verify.c:500:16: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

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

---
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;
+
        ptr = (unsigned long)iref;
        end = (unsigned long)ei + item_size;
        while (ptr < end) {
---

Hope this helps.

Best regards,
Mirsad Todorovac