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Date: Tue, 19 Aug 2025 15:52:24 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>, David Hildenbrand
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 linux-mm@kvack.org, linux-riscv@lists.infradead.org, Shuah Khan
 <shuah@kernel.org>, kernel@collabora.com
Subject: Re: [PATCH v2 4/8] selftests/mm: Add -Wunused family of flags
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On Mon, 18 Aug 2025 10:16:35 +0200 Kevin Brodsky <kevin.brodsky@arm.com> wrote:

> >  # Avoid accidental wrong builds, due to built-in rules working just a little
> >  # bit too well--but not quite as well as required for our situation here.
> >  #
> > @@ -35,6 +34,7 @@ MAKEFLAGS += --no-builtin-rules
> >  
> >  CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
> >  CFLAGS += -Wunreachable-code
> > +CFLAGS += -Wunused  -Wunused-parameter -Wunused-function -Wunused-label -Wunused-variable -Wunused-value
> 
> -Wall implies all of these except -Wunused-parameter (at least according
> to gcc(1)).
> 
> 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.

Yeah, we rely upon unused parameters in a million places:

#else
static inline void some_stub_function(type1 arg2, type2 arg2)
{
}
#endif