Re: [for-linus][PATCH 01/10] tracing: Suppress sparse warnings triggered by is_signed_type()

[Bart Van Assche]

On 8/23/22 18:49, Linus Torvalds wrote:
> On Tue, Aug 23, 2022 at 5:09 PM Bart Van Assche <bvanassche@xxxxxxx> wrote:
> > I'm probably doing something wrong but even with sparse commit 658ee8e0f631
> > ("unrestricted values are unrestricted even after a cast") I see warnings
> > being triggered by users of the is_signed_type() macro, warnings that
> > disappear if I change the definition of the is_signed_type() macro into 0:
>
> That's the
>
> > It does require that kernel change to make
> >
> >    #define is_signed_type(type)   (((type)(-1)) <= (type)0)
>
> part I was talking about.
>
> So your kernel side patch looks fine, except I don't think you need
> the '__force' - the sparse patches in my tree should make sparse happy
> about casting '-1'.
>
> But I didn't do very much testing.

Hi Linus,

Can you take a look at the following report from the kernel test robot:
https://lore.kernel.org/all/202208250433.EVz5pZkB-lkp@xxxxxxxxx/ ?

Do I see correctly that gcc reports a new warning for the above 
definition of is_signed_type() with W=1? I'm not sure how to get rid of 
that new gcc warning without reintroducing a sparse warning.

The tree that the kernel robot tested is available here: 
https://github.com/bvanassche/linux/tree/tracing

Thanks,

Bart.