Re: ACPICA compilation error on x86_64_defconfig (W=1 build)

["Shevchenko, Andriy" <andriy.shevchenko@intel.com>]

Note, I have posted two much better solutions in that bug report thread.
Please, choose one and fix, it prevents kernel from building...

On Wed, Apr 09, 2025 at 02:24:45PM +0300, Shevchenko, Andriy wrote:
> GCC should ignore all clang specific pragmas as far as I know.
> 
> But this seems to me the not the best solution either. What code needs is to
> have some refactoring to make sure the variable is used or not defined and used
> at all. Unfortunately, I am not familiar with ACPICA to propose anything right
> now, though.
> 
> On Tue, Apr 08, 2025 at 09:34:36PM +0300, Dumbre, Saket wrote:
> > I am not sure about the Linux environment specifics like Andy described in the
> > previous conversation, but if GCC or some other compiler throws an error in the
> > code with #pragma for clang, then may I suggest using this instead:
> > 
> > #pragma clang diagnostic push
> > #if defined(__clang__) && __clang__ >= n (replace n with the least version
> > number which introduces this new warning type)
> > #pragma clang diagnostic ignored "-Wunused-but-set-variable"
> > #endif
> > u32 num_carats;
> > #pragma clang diagnostic pop
> > 
> > ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > From: Dumbre, Saket <saket.dumbre@intel.com>
> > Sent: Tuesday, April 8, 2025 11:11 AM
> > To: Shevchenko, Andriy <andriy.shevchenko@intel.com>; Rafael J. Wysocki
> > <rafael@kernel.org>
> > Cc: Moore, Robert <robert.moore@intel.com>; Wysocki, Rafael J
> > <rafael.j.wysocki@intel.com>; linux-acpi@vger.kernel.org
> > <linux-acpi@vger.kernel.org>; acpica-devel@lists.linux.dev
> > <acpica-devel@lists.linux.dev>
> > Subject: Re: ACPICA compilation error on x86_64_defconfig (W=1 build)
> >  
> > Hi Andy and Rafael,
> > 
> > This issue is a duplication of an Apple ecosystem-based (ARM + M-series micro
> > architecture) ACPICA GitHub Issue, which I was waiting on a response from the
> > contributor/submitter to move ahead to resolve it:
> > https://github.com/acpica/acpica/issues/973
> > 
> > I don't see a platform specific file for Clang/LLVM in ACPICA (only for GCC and
> > MSVC), so I think the worst-case untidy solution would be to locally patch this
> > warning-turned-error by suppressing this warning type if the compiler is Clang/
> > LLVM. 
> > 
> > It would look somewhat better to move that line all the way down after all the
> > other definitions/declarations just before any execution line and wrap it with
> > a #pragma something along the lines:
> > 
> > #pragma clang diagnostic push
> > #pragma clang diagnostic ignored "-Wunused-but-set-variable"
> > u32 num_carats;
> > #pragma clang diagnostic pop
> > 
> > I am just not sure if this is the only place in the ACPICA code that generates
> > this warning type and depending on the answer, this fix could be implemented at
> > a wider/global scale, but please give this hacky fix a try and let me know if
> > it resolves that. Thanks a lot! 
> > 
> > 
> > Kind regards,
> > 
> > Saket Dumbre
> > 
> > 
> > ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > From: Shevchenko, Andriy
> > Sent: Monday, April 7, 2025 11:51 AM
> > To: Rafael J. Wysocki
> > Cc: Dumbre, Saket; Moore, Robert; Wysocki, Rafael J;
> > linux-acpi@vger.kernel.org; acpica-devel@lists.linux.dev
> > Subject: Re: ACPICA compilation error on x86_64_defconfig (W=1 build)
> > 
> > On Mon, Apr 07, 2025 at 08:49:41PM +0200, Rafael J. Wysocki wrote:
> > > On Mon, Apr 7, 2025 at 8:47 PM Andy Shevchenko
> > > <andriy.shevchenko@intel.com> wrote:
> > > >
> > > > v6.15-rc1 (but seems older should also be problematic) fails to compile by
> > > > Clang 19 with `make W=1`.
> > > >
> > > >   CC      drivers/acpi/acpica/nsaccess.o
> > > >   drivers/acpi/acpica/nsaccess.c:295:6: error: variable 'num_carats' set
> > but not used [-Werror,-Wunused-but-set-variable]
> > > >     295 |         u32 num_carats;
> > > >         |             ^
> > > >   1 error generated.
> > > >
> > > > I looked briefly in the code and I have no idea how to fix this, as
> > probably
> > > > __maybe_unused not an option for ACPICA. Hence this report.
> > > >
> > > > Note, the in-tree defconfig is in use:
> > > >
> > > >         git checkout v6.15-rc1
> > > >         make x86_64_defconfig
> > 
> > > >         make W=1
> > 
> > Since it's a clang, this should have also something like LLVM=1.
> > 
> > > > should trigger it.
> > 
> > --
> > With Best Regards,
> > Andy Shevchenko
> > 
> > 
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

-- 
With Best Regards,
Andy Shevchenko