Message-ID: <CAP-5=fVJkJ39_qx2T9ZHn-fdxjECP_2G+cyfRRAjLvZZt5vz2A@mail.gmail.com>
Date: Wed, 2 Apr 2025 09:53:57 -0700
From: Ian Rogers <irogers@...gle.com>
To: Leo Yan <leo.yan@....com>
Cc: Yury Norov <yury.norov@...il.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
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Subject: Re: [PATCH v1 09/48] perf tests: Silence -Wshorten-64-to-32 warnings

On Wed, Apr 2, 2025 at 9:38 AM Leo Yan <leo.yan@....com> wrote:
>
> Hi Ian,
>
> On Wed, Apr 02, 2025 at 08:42:58AM -0700, Ian Rogers wrote:
>
> [...]
>
> > On Wed, Apr 2, 2025 at 7:35 AM Leo Yan <leo.yan@....com> wrote:
> > >
> > > On Tue, Apr 01, 2025 at 11:23:07AM -0700, Ian Rogers wrote:
> > >
> > > [...]
> > >
> > > > @@ -478,13 +478,14 @@ static int __cmd_test(struct test_suite **suites, int argc, const char *argv[],
> > > >       int err = 0;
> > > >
> > > >       for (struct test_suite **t = suites; *t; t++) {
> > > > -             int i, len = strlen(test_description(*t, -1));
> > > > +             int i;
> > > > +             int len = (int)strlen(test_description(*t, -1));
> > >
> > > Thanks for huge polish.
> > >
> > > Just a concern from me.  Throughout this patch, the methodology is not
> > > consistent.  Some changes update variable types which is fine for me.
> > >
> > > But the case above it simply cast size_t to int.  Should we update the
> > > variable type as 'size_t' at here?
> >
> > Thanks Leo, I played around with it, but don't mind if someone wants
> > to do it a different way. I was trying to make the changes minimal.
> > The problem typically with size_t is we then use the value, for
> > example, as a printf size modifier and need to introduce lots of casts
> > back to being an int.
>
> This conclusion is not quite right, see:
> https://stackoverflow.com/questions/2524611/how-can-one-print-a-size-t-variable-portably-using-the-printf-family
>
> > When this isn't too great I've done it, but in
> > this case I think keeping the int, the lack of casts but a cast here
> > to capture that we expect test descriptions to fit in the size of an
> > int is the least worst option.
>
> I would say in another way.  After we enabled a compiler warning
> option, this will give us a chance to improve code by dismissing
> the warnings (and avoid potential bugs).
>
> If we use casts just to silence warnings, we also lose the opportunity
> to improve code quality.  The changes in this series that fix type
> mismatches are good, but I think the use of casts is not particularly
> helpful - we're simply switching from implicit compiler casts to
> explicit ones.

Right, but I think changing function parameters, return types would
turn into an epic refactor and the patch series is already unwieldy.
With the casts we can see the behavior is deliberate but that's not to
say it couldn't be better. With the warnings gone it allows
-Wshorten-64-to-32 to find the truly errant 64 to 32 bit implicit
casts. Anyway, I don't have time to do such a larger refactor so
somebody else is going to need to pick that up. I did refactor the
cases where I thought it mattered more, but as you say that does lead
to a feeling of inconsistency in the series.

Thanks,
Ian

> Thanks,
> Leo

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