Re: [PATCH] scripts: Add check-build-warnings.pl for tracking kernel build warnings

[Nathan Chancellor <nathan@kernel.org>]

Hi Pat,

On Fri, Oct 17, 2025 at 01:03:54PM -0400, Pat Somaru wrote:
> Add scripts/check-build-warnings.pl to automate the guidance in
> Documentation/process/maintainer-netdev.rst regarding new-warning-free
> code submissions. The netdev maintainers require that patches do not
> introduce new compiler warnings, and this script provides an
> automated/fool-proof way to do this with paste-into-commit-msg friendly
> output. This is not so much for netdev (which has it's own out-of-tree
> automation for this) but for folks who want to apply that bar to their
> contributions elsewhere and to have an easy way to communicate that with
> reviewers.
> 
> This script builds the kernel with specified targets and warning levels,
> saving warnings as baselines that can be checked against later builds to
> detect newly introduced warnings. This allows developers to easily
> verify their changes don't add new warnings before submitting patches.
> 
> Key features:
> - Automatic baseline creation and comparison per-target and
>   per-warning-level
> - Warning files stored alongside build artifacts (like .cmd files)
> - CONFIG_WERROR automatically disabled to capture warnings without build
>   failure
> - Support for W=1, W=2, W=3 extra warning levels
> - Clean by default to ensure all warnings are captured (not just changed
>   files)
> - Optional --no-clean for faster iterative development
> 
> Usage examples:
>   # Save initial baseline for a driver
>   scripts/check-build-warnings.pl --save-baseline drivers/net/ethernet/intel/
> 
>   # Check for new warnings after making changes
>   scripts/check-build-warnings.pl --check drivers/net/ethernet/intel/
> 
>   # Use stricter W=1 warnings (separate baseline)
>   scripts/check-build-warnings.pl --save-baseline --warn=1 drivers/net/

I don't know Perl so I cannot really review this but I do not see why
developers cannot just use 'make -s' and/or W=e (to set -Werror) to make
sure their code is warning free? I guess it could be helpful if there
are a lot of additional existing warnings in the code being modified but
those should be fixed, not just ignored.

Cheers,
Nathan