Re: [PATCH] modpost: Declare extra_warn with unused attribute

[Nathan Chancellor <nathan@kernel.org>]

On Tue, Mar 31, 2026 at 09:38:24PM +0200, Nicolas Schier wrote:
> On Wed, Mar 25, 2026 at 06:20:30PM -0700, Nathan Chancellor wrote:
> > A recent strengthening of -Wunused-but-set-variable (enabled with -Wall)
> > in clang under a new subwarning, -Wunused-but-set-global, points out an
> > unused static global variable in scripts/mod/modpost.c:
> > 
> >   scripts/mod/modpost.c:59:13: error: variable 'extra_warn' set but not used [-Werror,-Wunused-but-set-global]
> >      59 | static bool extra_warn;
> >         |             ^
> > 
> > This variable has been unused since commit 6c6c1fc09de3 ("modpost:
> > require a MODULE_DESCRIPTION()") but that is expected, as there are
> > currently no extra warnings at W=1 right now. Declare the variable with
> > the unused attribute to make it clear to the compiler that this variable
> > may be unused.
> > 
> > Cc: stable@vger.kernel.org
> > Fixes: 6c6c1fc09de3 ("modpost: require a MODULE_DESCRIPTION()")
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > ---
> > I will apply this to kbuild-fixes for 7.0.
> > ---
> >  scripts/mod/modpost.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> 
> modpost is just used in-tree, right?  Can't we just remove the '-W' flag
> and the extra_warn variable completely?

We could but I figured it was worth keeping it around in case we grow
any other checks that we would want under W=1. Not sure what those would
be but the dead code here is minimal so it did not seem worth it to
clean it up just for this warning.

> Nevertheless,
> 
> Reviewed-by: Nicolas Schier <nsc@kernel.org>

Thanks!

Nathan