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SubjectRe: [PATCH 1/1] perf annotate: Initialize 'arch' variable not to trip some -Werror=maybe-uninitialized
On Wed, Apr 03, 2024 at 09:01:56AM -0700, Ian Rogers wrote:
> On Wed, Apr 3, 2024 at 8:16 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> >
> > In some older distros the build is failing due to
> > -Werror=maybe-uninitialized, in this case we know that this isn't the
> > case because 'arch' gets initialized by evsel__get_arch(), so just init
> > 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=maybe-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=maybe-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>

Trying with this on top, i.e. what you suggests:

From 70e6fd996ce7f9c9adbb30640ed666025bf6f1e4 Mon Sep 17 00:00:00 2001
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Date: Wed, 3 Apr 2024 16:49:54 -0300
Subject: [PATCH 1/1] WIP

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/annotate.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index f316e0b65897957a..35235147b111e788 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -838,8 +838,10 @@ static int evsel__get_arch(struct evsel *evsel, struct arch **parch)
struct arch *arch;
int err;

- if (!arch_name)
+ if (!arch_name) {
+ *parch = NULL;
return errno;
+ }

*parch = arch = arch__find(arch_name);
if (arch == NULL) {
@@ -2266,7 +2268,7 @@ struct annotated_data_type *hist_entry__get_data_type(struct hist_entry *he)
{
struct map_symbol *ms = &he->ms;
struct evsel *evsel = hists_to_evsel(he->hists);
- struct arch *arch = NULL;
+ struct arch *arch;
struct disasm_line *dl;
struct annotated_insn_loc loc;
struct annotated_op_loc *op_loc;
--
2.44.0

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