linux-kernel - Re: [PATCH v1 02/48] tools headers: Silence -Wshorten-64-to-32 warnings

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Message-ID: <CAP-5=fU6E1_8Vzki1dVyb8hDEYOXaSNSrJJkR6AOU8xqvknT8w@mail.gmail.com>
Date: Thu, 3 Apr 2025 07:52:45 -0700
From: Ian Rogers <irogers@...gle.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>, Peter Zijlstra <peterz@...radead.org>, 
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Subject: Re: [PATCH v1 02/48] tools headers: Silence -Wshorten-64-to-32 warnings

On Thu, Apr 3, 2025 at 7:26 AM Yury Norov <yury.norov@...il.com> wrote:
>
> On Thu, Apr 03, 2025 at 10:08:39AM -0400, Yury Norov wrote:
> > On Tue, Apr 01, 2025 at 11:23:00AM -0700, Ian Rogers wrote:
> > > The clang warning -Wshorten-64-to-32 can be useful to catch
> > > inadvertent truncation. In some instances this truncation can lead to
> > > changing the sign of a result, for example, truncation to return an
> > > int to fit a sort routine. Silence the warning by making the implicit
> > > truncation explicit.
> > >
> > > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> I'm the first person in the To list, but only a couple patches in the
> series are related to my area. If you want to move it with me, can you
> send bitmaps, bitfields etc. separately?

Hi Yury,

If you think it is worthwhile. I did the series to see how prevalent a
bug was in perf's code - inspired by Leo Yan fixing an instance of it.
I would prefer not to be on the hook for all the kernel warnings :-)
Perhaps casts to avoid changing bitmap_weight's type. Unfortunately to
get to where the perf issues were I needed to clean up header files.
In the bitmap cases the change is just to make implicit casts explicit
and I don't know how much value you see in that.

Thanks,
Ian

> Thanks,
> Yury