Re: [groeck-staging:hwmon-next 13/13] drivers/hwmon/gpio-fan.c:250:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is false

[Nathan Chancellor <nathan@kernel.org>]

On Wed, Apr 09, 2025 at 08:50:14AM +0200, Alexander Stein wrote:
> Am Mittwoch, 9. April 2025, 04:51:35 CEST schrieb Guenter Roeck:
> > On 4/8/25 19:11, kernel test robot wrote:
> > > All warnings (new ones prefixed by >>):
> > > 
> > >>> drivers/hwmon/gpio-fan.c:250:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> > >       250 |         if (val == 0)
> > >           |             ^~~~~~~~
> > >     drivers/hwmon/gpio-fan.c:255:9: note: uninitialized use occurs here
> > >       255 |         return ret ? ret : count;
> > >           |                ^~~
> > >     drivers/hwmon/gpio-fan.c:250:2: note: remove the 'if' if its condition is always true
> > >       250 |         if (val == 0)
> > >           |         ^~~~~~~~~~~~~
> > >       251 |                 ret = set_fan_speed(fan_data, fan_data->num_speed - 1);
> > >     drivers/hwmon/gpio-fan.c:237:9: note: initialize the variable 'ret' to silence this warning
> > >       237 |         int ret;
> > >           |                ^
> > >           |                 = 0
> > >     1 warning generated.
> > > 
> > 
> > I dropped the patch from linux-next. Please fix and make sure there are no
> > such problems before resubmitting.
> 
> Oh, surprising. A W=1 build on my machine doesn't raise this warning. I'm not
> sure if this is specific to riscv or clang. Nevertheless this is correct and
> I'll send a fixed one.

Unfortunately, the kernel disabled GCC's version, -Wmaybe-uninitialized,
several years ago in commit 78a5255ffb6a ("Stop the ad-hoc games with
-Wno-maybe-initialized"), so you either need to add it yourself via
KCFLAGS or just do a quick pass with Clang's slightly weaker but more
reliable -Wsometimes-uninitialized. I have fast versions of clang
available on kernel.org to make doing this testing a little easier:
https://mirrors.edge.kernel.org/pub/tools/llvm/

Cheers,
Nathan