[drm-xe:drm-xe-next 989/1016] drivers/gpu/drm/xe/xe_wait_user_fence.c:46:2: warning: variable 'passed' is used uninitialized whenever switch default is taken

[Nathan Chancellor]

On Sun, Dec 17, 2023 at 03:28:47AM +0800, kernel test robot wrote:
> tree:   https://gitlab.freedesktop.org/drm/xe/kernel.git drm-xe-next
> head:   c54005fdd0347a17088e7ff78070a55bf9103bc4
> commit: ad7d86415578e1a5deedb0ceed5c281f7367d66d [989/1016] drm/xe: Enable W=1 warnings by default
> config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20231217/202312170357.KPSinwPs-lkp@intel.com/config)
> compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231217/202312170357.KPSinwPs-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp at intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202312170357.KPSinwPs-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    warning: unknown warning option '-Wrestrict' [-Wunknown-warning-option]
>    warning: unknown warning option '-Wpacked-not-aligned'; did you mean '-Wpacked-non-pod'? [-Wunknown-warning-option]
>    warning: unknown warning option '-Wformat-overflow'; did you mean '-Wshift-overflow'? [-Wunknown-warning-option]
>    warning: unknown warning option '-Wformat-truncation' [-Wunknown-warning-option]
>    warning: unknown warning option '-Wstringop-overflow'; did you mean '-Wshift-overflow'? [-Wunknown-warning-option]
>    warning: unknown warning option '-Wstringop-truncation'; did you mean '-Wstring-concatenation'? [-Wunknown-warning-option]

I am not sure why these warnings are even showing up in the first place,
they are wrapped with cc-option, which should be catching that they are
not supported... Is 0day doing something funky with KCFLAGS?
Regardless...

> >> drivers/gpu/drm/xe/xe_wait_user_fence.c:46:2: warning: variable 'passed' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
>            default:
>            ^~~~~~~
>    drivers/gpu/drm/xe/xe_wait_user_fence.c:50:9: note: uninitialized use occurs here
>            return passed ? 0 : 1;
>                   ^~~~~~
>    drivers/gpu/drm/xe/xe_wait_user_fence.c:21:13: note: initialize the variable 'passed' to silence this warning
>            bool passed;
>                       ^
>                        = 0
>    7 warnings generated.

I was surprised that this was not caught sooner as
-Wsometimes-uninitialized is a part of -Wall but it looks like
drivers/gpu/drm/xe/Makefile was forked from the i915 Makefile before
commit 43192617f781 ("drm/i915: Enable -Wsometimes-uninitialized") was
added. It is good to see that the warnings are aligned now so that
trivial uninitialized warnings can be caught by clang because they are
disabled for GCC since commit 78a5255ffb6a ("Stop the ad-hoc games with
-Wno-maybe-initialized") in 5.7. Will this be fixed as a separate patch?

Cheers,
Nathan