linux-kernel - next-20250725 i386 x86_64 virtio_ring.c error variable 'id' is uninitialized when used here [-Werror,-Wuninitialized]

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Message-ID: <CA+G9fYuBnDVaiZ6Mqhr=4Y2quAsqeZoGfJ158xJ1-Q5HHw=cBw@mail.gmail.com>
Date: Fri, 25 Jul 2025 13:12:53 +0530
From: Naresh Kamboju <naresh.kamboju@...aro.org>
To: open list <linux-kernel@...r.kernel.org>, virtualization@...ts.linux.dev, 
	clang-built-linux <llvm@...ts.linux.dev>, lkft-triage@...ts.linaro.org, 
	Linux Regressions <regressions@...ts.linux.dev>
Cc: Jason Wang <jasowang@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Nathan Chancellor <nathan@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, Dan Carpenter <dan.carpenter@...aro.org>, 
	Anders Roxell <anders.roxell@...aro.org>, Ben Copeland <benjamin.copeland@...aro.org>
Subject: next-20250725 i386 x86_64 virtio_ring.c error variable 'id' is
 uninitialized when used here [-Werror,-Wuninitialized]

Regressions noticed while building x86_64 and i386 builds with clang-nightly
and clang-20 toolchains on the Linux next-20250725 tag.

First seen on the Linux next-20250725
Good: next-20250724
Bad:  next-20250725

Regression Analysis:
- New regression? Yes
- Reproducibility? Yes

## Build regressions
* i386, build
  - clang-20-defconfig
  - clang-nightly-defconfig

* x86_64, build
  - clang-20-allyesconfig
  - clang-20-lkftconfig
  - clang-20-lkftconfig-compat
  - clang-20-lkftconfig-kcsan
  - clang-20-lkftconfig-no-kselftest-frag
  - clang-20-x86_64_defconfig
  - clang-nightly-lkftconfig
  - clang-nightly-lkftconfig-hardening
  - clang-nightly-lkftconfig-kselftest
  - clang-nightly-lkftconfig-lto-full
  - clang-nightly-lkftconfig-lto-thing
  - clang-nightly-x86_64_defconfig
  - gcc-13-allyesconfig
  - korg-clang-20-lkftconfig-hardening
  - korg-clang-20-lkftconfig-lto-full
  - korg-clang-20-lkftconfig-lto-thing
  - rustclang-nightly-lkftconfig-kselftest

Build regression: next-20250725 i386 x86_64 virtio_ring.c error
variable 'id' is uninitialized when used here
[-Werror,-Wuninitialized]

Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>

## Build log
drivers/virtio/virtio_ring.c:2113:40: error: variable 'id' is
uninitialized when used here [-Werror,-Wuninitialized]
 2113 |                 BAD_RING(vq, "id %u out of range\n", id);
      |                                                      ^~
drivers/virtio/virtio_ring.c:2077:19: note: initialize the variable
'id' to silence this warning
 2077 |         u16 last_used, id, last_used_idx;
      |                          ^
      |                           = 0
1 error generated.

## Source
* Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
* Project: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20250725/
* Git sha: d7af19298454ed155f5cf67201a70f5cf836c842
* Git describe: 6.16.0-rc7-next-20250725
* kernel version: next-20250725
* Architectures: i386, x86_64
* Toolchains: clang-nightly clang-20
* Kconfigs: defconfig hardening lto-thing lto-full

## Test
* Test log: https://qa-reports.linaro.org/api/testruns/29243926/log_file/
* Test details:
https://regressions.linaro.org/lkft/linux-next-master/next-20250725/build/clang-nightly-defconfig/
* Test run: https://regressions.linaro.org/lkft/linux-next-master/next-20250725/testruns/1727064/
* Test history:
https://regressions.linaro.org/lkft/linux-next-master/next-20250725/log-parser-build-clang/clang-compiler-drivers_virtio_virtio_ring_c-error-variable-id-is-uninitialized-when-used-here/
* Test plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/builds/30LiHiVcyjXbMOk2IAEwlO93ZaH
* Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/30LiHiVcyjXbMOk2IAEwlO93ZaH/
* Kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/30LiHiVcyjXbMOk2IAEwlO93ZaH/config

## steps to reproduce
 * tuxmake --runtime podman --target-arch i386 --toolchain
clang-nightly --kconfig defconfig LLVM=1 LLVM_IAS=1

--
Linaro LKFT
https://lkft.linaro.org