Re: [PATCH] drm/amdgpu: Wrap -Wunused-but-set-variable in cc-option

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 08 Jun 2023, Nathan Chancellor <nathan@kernel.org> wrote:
> -Wunused-but-set-variable was only supported in clang starting with
> 13.0.0, so earlier versions will emit a warning, which is turned into a
> hard error for the kernel to mirror GCC:
>
>   error: unknown warning option '-Wunused-but-set-variable'; did you mean '-Wunused-const-variable'? [-Werror,-Wunknown-warning-option]
>
> The minimum supported version of clang for building the kernel is
> 11.0.0, so match the rest of the kernel and wrap
> -Wunused-but-set-variable in a cc-option call, so that it is only used
> when supported by the compiler.

I wonder if there's a table somewhere listing all the warning options,
which GCC and Clang versions support them, and which versions have them
in -Wall and -Wextra. Would be really useful.

If there isn't one, it would be really helpful. *wink*.

BR,
Jani.


>
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1869
> Fixes: a0fd5a5f676c ("drm/amd/amdgpu: introduce DRM_AMDGPU_WERROR")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  drivers/gpu/drm/amd/amdgpu/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile b/drivers/gpu/drm/amd/amdgpu/Makefile
> index 7ee68b1bbfed..86b833085f19 100644
> --- a/drivers/gpu/drm/amd/amdgpu/Makefile
> +++ b/drivers/gpu/drm/amd/amdgpu/Makefile
> @@ -40,7 +40,7 @@ ccflags-y := -I$(FULL_AMD_PATH)/include/asic_reg \
>  	-I$(FULL_AMD_PATH)/amdkfd
>  
>  subdir-ccflags-y := -Wextra
> -subdir-ccflags-y += -Wunused-but-set-variable
> +subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
>  subdir-ccflags-y += -Wno-unused-parameter
>  subdir-ccflags-y += -Wno-type-limits
>  subdir-ccflags-y += -Wno-sign-compare
>
> ---
> base-commit: 6bd4b01e8938779b0d959bdf33949a9aa258a363
> change-id: 20230608-amdgpu-wrap-wunused-but-set-variable-in-cc-option-0be9528ac5c8
>
> Best regards,

-- 
Jani Nikula, Intel Open Source Graphics Center