linux-kernel - next-20250813: x86_64 iov_iter.h:171:7: error: variable 'remain' is used uninitialized whenever 'if'

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Message-ID: <CA+G9fYtJPqkugHFbgs8vNK5jNGivX1yO1ZiL2q97c_dazUiArA@mail.gmail.com>
Date: Wed, 13 Aug 2025 23:26:05 +0530
From: Naresh Kamboju <naresh.kamboju@...aro.org>
To: clang-built-linux <llvm@...ts.linux.dev>, lkft-triage@...ts.linaro.org, 
	open list <linux-kernel@...r.kernel.org>, 
	Linux Regressions <regressions@...ts.linux.dev>
Cc: Anders Roxell <anders.roxell@...aro.org>, Dan Carpenter <dan.carpenter@...aro.org>, 
	Arnd Bergmann <arnd@...db.de>, Ben Copeland <benjamin.copeland@...aro.org>, 
	Nathan Chancellor <nathan@...nel.org>
Subject: next-20250813: x86_64 iov_iter.h:171:7: error: variable 'remain' is
 used uninitialized whenever 'if'

Regressions noticed while building x86_64 and i386 builds with clang-nightly
and clang-20 toolchains on the Linux next-20250813 tag.

First seen on the Linux next-20250813
Good: next-20250812
Bad:  next-20250813

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

## Build regressions
* x86_64, build
  - clang-20-lkftconfig-compat

Build regression: next-20250813 x86_64 iov_iter.h:171:7: error:
variable 'remain' is used uninitialized whenever 'if'

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

## Build log
In file included from net/core/skbuff.c:66:
include/linux/iov_iter.h:171:7: error: variable 'remain' is used
uninitialized whenever 'if' condition is true
[-Werror,-Wsometimes-uninitialized]
  171 |                 if (skip >= fsize)
      |                     ^~~~~~~~~~~~~
include/linux/iov_iter.h:190:7: note: uninitialized use occurs here
  190 |                 if (remain)
      |                     ^~~~~~
include/linux/iov_iter.h:171:3: note: remove the 'if' if its condition
is always false
  171 |                 if (skip >= fsize)
      |                 ^~~~~~~~~~~~~~~~~~
  172 |                         goto next;
      |                         ~~~~~~~~~
include/linux/iov_iter.h:163:22: note: initialize the variable
'remain' to silence this warning
  163 |                 size_t part, remain, consumed;
      |                                    ^
      |                                     = 0
1 error generated.
make[5]: *** [scripts/Makefile.build:287: net/core/skbuff.o] Error 1
In file included from net/core/datagram.c:53:
include/linux/iov_iter.h:171:7: error: variable 'remain' is used
uninitialized whenever 'if' condition is true
[-Werror,-Wsometimes-uninitialized]
  171 |                 if (skip >= fsize)
      |                     ^~~~~~~~~~~~~
include/linux/iov_iter.h:190:7: note: uninitialized use occurs here
  190 |                 if (remain)
      |                     ^~~~~~
include/linux/iov_iter.h:171:3: note: remove the 'if' if its condition
is always false
  171 |                 if (skip >= fsize)
      |                 ^~~~~~~~~~~~~~~~~~
  172 |                         goto next;
      |                         ~~~~~~~~~
include/linux/iov_iter.h:163:22: note: initialize the variable
'remain' to silence this warning
  163 |                 size_t part, remain, consumed;
      |                                    ^
      |                                     = 0
1 error generated.
make[5]: *** [scripts/Makefile.build:287: net/core/datagram.o] Error 1
In file included from lib/iov_iter.c:14:
include/linux/iov_iter.h:171:7: error: variable 'remain' is used
uninitialized whenever 'if' condition is true
[-Werror,-Wsometimes-uninitialized]
  171 |                 if (skip >= fsize)
      |                     ^~~~~~~~~~~~~
include/linux/iov_iter.h:190:7: note: uninitialized use occurs here
  190 |                 if (remain)
      |                     ^~~~~~
include/linux/iov_iter.h:171:3: note: remove the 'if' if its condition
is always false
  171 |                 if (skip >= fsize)
      |                 ^~~~~~~~~~~~~~~~~~
  172 |                         goto next;
      |                         ~~~~~~~~~
include/linux/iov_iter.h:163:22: note: initialize the variable
'remain' to silence this warning
  163 |                 size_t part, remain, consumed;
      |                                    ^
      |                                     = 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-20250813/
* kernel version: next-20250813
* Architectures: x86_64, i386
* Toolchains: clang-20
* Kconfigs: defconfig

## Test
* Test log: https://qa-reports.linaro.org/api/testruns/29479215/log_file/
* Test details:
https://regressions.linaro.org/lkft/linux-next-master/next-20250813/log-parser-build-clang/clang-compiler-include_linux_iov_iter_h-error-variable-remain-is-used-uninitialized-whenever-if-condition-is-true/
* Test plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/builds/31DcGmmPgATtnxuFKXwu6DM9bZu/
* Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/31DcGmmPgATtnxuFKXwu6DM9bZu/
* Kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/31DcGmmPgATtnxuFKXwu6DM9bZu/config

## steps to reproduce
 * tuxmake --runtime podman --target-arch x86_64 --toolchain clang-20
--kconfig x86_64_defconfig LLVM=1 LLVM_IAS=1

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