linux-kernel - Re: [PATCH] selftests: proc: mark vsyscall strings maybe-unused

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Message-Id: <20250820143954.33d95635e504e94df01930d0@linux-foundation.org>
Date: Wed, 20 Aug 2025 14:39:54 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Bala-Vignesh-Reddy <reddybalavignesh9979@...il.com>
Cc: shuah@...nel.org, surenb@...gle.com, skhan@...uxfoundation.org,
 linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH] selftests: proc: mark vsyscall strings maybe-unused

On Wed, 20 Aug 2025 23:26:10 +0530 Bala-Vignesh-Reddy <reddybalavignesh9979@...il.com> wrote:

> The str_vsyscall_* constants in proc-pid-vm.c triggers
> -Wunused-const-variable warnings with gcc-13.32 and clang 18.1.

OT but lol.  My head is spinning at the term "const-variable".  I
understand what they mean, but it's oxymoronic.

> Define and apply __maybe_unused locally to suppress the warnings.
> No functional change
> 
> Fixes compiler warning:
> warning: ‘str_vsyscall_*’ defined but not used[-Wunused-const-variable]
>
> ...
>
> --- a/tools/testing/selftests/proc/proc-pid-vm.c
> +++ b/tools/testing/selftests/proc/proc-pid-vm.c
> @@ -47,6 +47,10 @@
>  #include <sys/resource.h>
>  #include <linux/fs.h>
>  
> +#ifndef __maybe_unused
> +#define __maybe_unused __attribute__((__unused__))
> +#endif

This would be approximately the seventh definition of __maybe_unused
under tools/testing/selftests.  And there's another in
tools/testing/memblock, which, as if admitting that its directory is in
the wrong place, had to go and include ../selftests/kselftest.h.

So it would be pleasing if some kind soul were to define __maybe_unused
in a common place, which looks to be
tools/testing/selftests/kselftest.h.  Then go zap all those private
definitions.

This could be done either before or after your patch.

>  #include "../kselftest.h"

And we have 350 occurrences of "../kselftest.h".  Shouldn't the build
system be providing -Itools/testing/selftests?

Anyway, patch looks OK - I'll add it to mm.git, thanks.