Re: [PATCH 6/6] config.mak.dev: enable -Wunused-parameter by default

[Eric Sunshine <sunshine@sunshineco.com>]

On Wed, Aug 28, 2024 at 12:01 AM Jeff King <peff@peff.net> wrote:
> Having now removed or annotated all of the unused function parameters in
> our code base, I found that each instance falls into one of three
> categories:
>
>   1. ignoring the parameter is a bug (e.g., a function takes a ptr/len
>      pair, but ignores the length). Detecting these helps us find the
>      bugs.
>
>   2. the parameter is unnecessary (and usually left over from a
>      refactoring or earlier iteration of a patches series). Removing
>      these cleans up the code.
>
>   3. the function has to conform to a specific interface (because it's
>      used via a function pointer, or matches something on the other side
>      of an #ifdef). These ones are annoying, but annotating them with
>      UNUSED is not too bad (especially if the compiler tells you about
>      the problem promptly).
> [...]
> And since the code base is now at a spot where we compile cleanly with
> -Wunused-parameter, turning it on will make it the responsibility of
> individual patch writers going forward.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> diff --git a/config.mak.dev b/config.mak.dev
> @@ -54,7 +54,6 @@ ifeq ($(filter extra-all,$(DEVOPTS)),)
>  DEVELOPER_CFLAGS += -Wno-sign-compare
> -DEVELOPER_CFLAGS += -Wno-unused-parameter

What is the expectation regarding newcomers to the project or even
people who have not been following this topic and its cousins?
Documentation/CodingGuidelines recommends enabling DEVELOPER mode,
which is good, but this change means that such people may now be hit
with a compiler complaint which they don't necessarily know how to
deal with in the legitimate case #3 (described above). Should
CodingGuidelines be updated to mention "UNUSED" and the circumstances
under which it should be used?