Re: [PATCH v2 4/8] selftests/mm: Add -Wunused family of flags

[Kevin Brodsky <kevin.brodsky@arm.com>]

On 21/08/2025 08:28, Muhammad Usama Anjum wrote:
>> As to -Wunused-parameter I am frankly not convinced it's worth the
>> hassle. We're getting 90 lines changed in patch 6-8 just to mark
>> parameters as unused, in other words noise to keep the compiler happy.
>> It is not enabled by default in the kernel proper precisely because it
>> is so noisy when callbacks are involved.
>>
>> Patch 5 is clearly an improvement, but I'd rather take it without
>> actually enabling -Wunused-parameter. The rest of this patch isn't that
>> useful either IMHO.
> Patch 5 removes genuinely unused parameters flagged by the compiler. If we
> drop the -Wunused-parameter option, however, new unused parameters will
> continue to creep in with future patches. The goal of enabling this warning
> is to surface such issues early so developers can address them during
> development, rather than later during review or debugging.
>
> Long term, I’d like us to rely more on compiler and static analysis just like
> kernel to catch these kinds of problems proactively, instead of waiting until
> they’re reported or someone fixes them later. While it may feel like noise
> initially, this is largely a one-time cleanup—once done, developers will
> simply fix warnings as they arise, keeping the codebase cleaner going forward.

Agreed on the general principle, but I think the hassle is just too big
for what we're getting in return here (see also Andrew's reply). New
code may also introduce a bunch of unused parameters for legitimate
reasons and it's easy to imagine contributors ignoring such seemingly
harmless/irrelevant warnings instead of sprinkling __unused all over. My
feeling is that unused parameters are expected to be allowed in the
kernel and it isn't helpful to go against that expectation in just a
small subset of kselftests.

- Kevin