Re: [PATCH] kbuild: Disable two Clang specific enumeration warnings

["Arnd Bergmann" <arnd@arndb.de>]

On Tue, Mar 5, 2024, at 20:30, Nathan Chancellor wrote:
> On Tue, Mar 05, 2024 at 10:52:16AM -0800, Nick Desaulniers wrote:
>> On Tue, Mar 5, 2024 at 10:50 AM Arnd Bergmann <arnd@arndb.de> wrote:
>> >
>> > On Tue, Mar 5, 2024, at 18:42, Nathan Chancellor wrote:
>> > >
>> > > As the warnings do not appear to have a high signal to noise ratio and
>> > > the source level silencing options are not sustainable, disable the
>> > > warnings unconditionally, as they will be enabled with -Wenum-conversion
>> > > and are supported in all versions of clang that can build the kernel.
>> >
>> > I took a look at a sample of warnings in an allmodconfig build
>> > and found a number that need attention. I would much prefer to
>> > leave these turned on at the W=1 level and only disable them
>> > at the default warning level.
>> 
>> Sounds like these new diagnostics are very noisy. 0day bot sends
>> people reports at W=1. Perhaps W=2?

It feels like this is not a great reason for moving it to W=2
instead of W=1, but W=2 is still better than always disabling
it I think.

Specifically, the 0day bot warns for newly added W=1 warnings
but not for preexisting ones, and I think there are other warnings
at the W=1 level that are similarly noisy to this one.

> A number of subsystems test with W=1 as well and while opting into W=1
> means that you are potentially asking for new warnings across newer
> compiler releases, a warning with this number of instances is going to
> cause a lot of issues (I think of netdev for example).

I only see a handful of warnings in net (devlink, bpf) and
drivers/net (ethernet/{3com,amd8111e,funeth,hns,idpf,jme,mlx4} and
wireless/{iwlwifi,mt76,rtw88,rtw89}). 

These are also some of the ones that I think need a closer look.

> Fundamentally, I do not really care which avenue we take (either this
> change or off by default, on at W=1), I am happy to do whatever.
> Unfortunately, CONFIG_WERROR makes these decisions much more urgent
> because it is either disable it and have other warnings creep in amongst
> the sprawl of these warnings or leave it on and miss other errors for
> the same reason.

Agreed.

       Arnd