linux-kernel - Re: [for-linus][PATCH 01/10] tracing: Suppress sparse warnings triggered by is_signed

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Message-ID: <CAHk-=wgV1F7_ErXkXT2wd+07LJd_3Vp-yVUKLROPiEgijeoTrQ@mail.gmail.com>
Date:   Tue, 23 Aug 2022 18:49:25 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [for-linus][PATCH 01/10] tracing: Suppress sparse warnings
 triggered by is_signed_type()

On Tue, Aug 23, 2022 at 5:09 PM Bart Van Assche <bvanassche@....org> 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.

                     Linus