linux-kernel - Re: [PATCH v1 0/2] drm/i915/fence: A couple of build fixes

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Message-ID: <87a5gvw4y9.fsf@intel.com>
Date: Thu, 29 Aug 2024 21:37:34 +0300
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Nathan Chancellor <nathan@...nel.org>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Joonas Lahtinen
 <joonas.lahtinen@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v1 0/2] drm/i915/fence: A couple of build fixes

On Thu, 29 Aug 2024, Nathan Chancellor <nathan@...nel.org> wrote:
> On Thu, Aug 29, 2024 at 09:10:41PM +0300, Andy Shevchenko wrote:
>> On Thu, Aug 29, 2024 at 07:53:25PM +0300, Andy Shevchenko wrote:
>> > On Thu, Aug 29, 2024 at 07:38:08PM +0300, Jani Nikula wrote:
>> > > On Thu, 29 Aug 2024, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
>> > > > With CONFIG_WERROR=y and `make W=1` build fails on my x86_64 machine.
>> > > > This is due to some unused functions. Hence these quick fixes.
>> > > 
>> > > Since when have we been getting the warnings for static inlines?
>
> Since commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
> inline functions for W=1 build"). clang warns about unused static inline
> functions in .c files, unlike GCC (they both do not warn for functions
> coming from .h files). This difference is worked around for the normal
> build by adding '__maybe_unused' to the definition of 'inline' but
> Masahiro wanted to disable it for W=1 to allow this difference to find
> unused/dead code. There have not been too many complaints as far as I am
> aware but I can see how it is surprising.

Heh, I was just going to reply citing the same commit.

I occasionally build with clang myself, and we do enable most W=1 by
default in the drm subsystem, so I was wondering why I hadn't hit
this. The crucial difference is that we lack -DKBUILD_EXTRA_WARN1 which
W=1 adds.

I see there's no subdir-cppflags-y, but I don't see any harm in us
adding -Wundef and -DKBUILD_EXTRA_WARN1 to subdir-ccflags-y. After we
fix the fallout, of course. Do you?

I don't much like the __maybe_unused stuff, but I guess it's fine as a
stopgap measure, and then we can grep for that when running out of
things to do. :p

The TL;DR is,

Reviewed-by: Jani Nikula <jani.nikula@...el.com>

on the series.

BR,
Jani.

-- 
Jani Nikula, Intel