linux-kernel - Re: [PATCH] libperf test: Silence printf flag warning

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Date:   Mon, 10 May 2021 09:33:33 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libperf test: Silence printf flag warning

On Tue, May 4, 2021 at 6:53 PM Rob Herring <robh@...nel.org> wrote:
>
> On Tue, May 4, 2021 at 2:43 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > __u64 maybe an unsigned long, it may also differ from the format
> > expected by PRIu64. Add a cast to silence the warning:
> >
> > tools/lib/perf/tests/test-evsel.c:176:33: error: format specifies type 'unsigned long long' but the argument has type 'unsigned long' [-Werror,-Wformat]
> >                 __T_VERBOSE("count = %llu\n", end - start);
> >                                      ~~~~     ^~~~~~~~~~~
> >                                      %lu
>
> Which arch/compiler did you hit this? LLVM? Would have been 64-bit
> presumably. I'm wondering how I didn't...
>
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/lib/perf/tests/test-evsel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/perf/tests/test-evsel.c b/tools/lib/perf/tests/test-evsel.c
> > index 288b5feaefe2..558097bbbfd0 100644
> > --- a/tools/lib/perf/tests/test-evsel.c
> > +++ b/tools/lib/perf/tests/test-evsel.c
> > @@ -173,7 +173,7 @@ static int test_stat_user_read(int event)
> >
> >                 __T("invalid counter data", (end - start) > last);
> >                 last = end - start;
> > -               __T_VERBOSE("count = %llu\n", end - start);
> > +               __T_VERBOSE("count = %llu\n", (unsigned long long)(end - start));
>
> I think I'd either change end/start to uint64_t which matches the
> count struct and use PRIu64, or change them to unsigned long long.

Thanks! I need to dig into this again, I suspect there was a problem
on PowerPC defining s64/u64 to be long int. Perhaps this is happening
by way of a typedef using int64_t but more likely defining
__SANE_USERSPACE_TYPES__ is my fix. The guidance in the kernel on
formatters is pretty clear:
https://www.kernel.org/doc/Documentation/printk-formats.txt
And so I think it is better to fix the type for overall sanity and to drop this.

Thanks,
Ian


> >         }
> >
> >         perf_evsel__munmap(evsel);
> > --
> > 2.31.1.607.g51e8a6a459-goog
> >