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From: Ian Rogers <irogers@google.com>
Date: Wed, 3 Apr 2024 15:01:43 -0700
Message-ID: <CAP-5=fWKUb=ftSOo-U5NVYsP1WZewnrcYJ9EJPHfO8j_4evm1A@mail.gmail.com>
Subject: Re: [PATCH 1/1] perf annotate: Initialize 'arch' variable not to trip
 some -Werror=maybe-uninitialized
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>, Adrian Hunter <adrian.hunter@intel.com>, 
	Jiri Olsa <jolsa@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Apr 3, 2024 at 2:03=E2=80=AFPM Arnaldo Carvalho de Melo <acme@kerne=
l.org> wrote:
>
> On Wed, Apr 03, 2024 at 09:01:56AM -0700, Ian Rogers wrote:
> > On Wed, Apr 3, 2024 at 8:16=E2=80=AFAM Arnaldo Carvalho de Melo <acme@k=
ernel.org> wrote:
> > >
> > > In some older distros the build is failing due to
> > > -Werror=3Dmaybe-uninitialized, in this case we know that this isn't t=
he
> > > case because 'arch' gets initialized by evsel__get_arch(), so just in=
it
> > > it to NULL to silence those cases.
> > >
> > > E.g.:
> > >
> > >     32    17.12 opensuse:15.5                 : FAIL gcc version 7.5.=
0 (SUSE Linux)
> > >         util/annotate.c: In function 'hist_entry__get_data_type':
> > >     util/annotate.c:2269:15: error: 'arch' may be used uninitialized =
in this function [-Werror=3Dmaybe-uninitialized]
> > >       struct arch *arch;
> > >                    ^~~~
> > >     cc1: all warnings being treated as errors
> > >
> > >       43     7.30 ubuntu:18.04-x-powerpc64el    : FAIL gcc version 7.=
5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
> > >     util/annotate.c: In function 'hist_entry__get_data_type':
> > >     util/annotate.c:2351:36: error: 'arch' may be used uninitialized =
in this function [-Werror=3Dmaybe-uninitialized]
> > >        if (map__dso(ms->map)->kernel && arch__is(arch, "x86") &&
> > >                                         ^~~~~~~~~~~~~~~~~~~~~
> > >     cc1: all warnings being treated as errors
> > >
> > > Cc: Adrian Hunter <adrian.hunter@intel.com>
> > > Cc: Ian Rogers <irogers@google.com>
> > > Cc: Jiri Olsa <jolsa@kernel.org>
> > > Cc: Namhyung Kim <namhyung@kernel.org>
> > > Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> >
> > This looks fine but I couldn't line up the errors with code in the
> > tree. I was curious why the "maybe-uninitialized" was failing. Perhaps
> > evsel__get_arch should set the out argument to NULL when an error
> > occurs. This fix is also good but may potentially need repeating for
> > other evsel__get_arch cases, so a fix in evsel__get_arch may be
> > preferable.
> >
> > Reviewed-by: Ian Rogers <irogers@google.com>
>
> Yeah, your suggestion is better and I just tested, satisfies the
> compilers that were emitting this warning.
>
> I stamped a:
>
> Suggested-by: Ian Rogers <irogers@google.com>
>
> and kept your Reviewed-by, ok?

Sure :-)

Thanks,
Ian

> - Arnaldo