linux-kernel - Re: [PATCH] util: constant -1 with expression of type char and allocation failure handling

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Message-ID: <ZnpO8TKWSiterMwC@google.com>
Date: Mon, 24 Jun 2024 22:00:33 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Yunseong Kim <yskelg@...il.com>
Cc: Ian Rogers <irogers@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Yang Jihong <yangjihong1@...wei.com>, Ze Gao <zegao2021@...il.com>,
	Leo Yan <leo.yan@...ux.dev>, Ravi Bangoria <ravi.bangoria@....com>,
	Austin Kim <austindh.kim@...il.com>, shjy180909@...il.com,
	linux-perf-users <linux-perf-users@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] util: constant -1 with expression of type char and
 allocation failure handling

Hello,

On Thu, Jun 20, 2024 at 04:10:53AM +0900, Yunseong Kim wrote:
> Hi Ian,
> 
> On 6/20/24 4:03 오전, Ian Rogers wrote:
> > 
> > 
> > On Wed, Jun 19, 2024, 11:39 AM <yskelg@...il.com
> > <mailto:yskelg@...il.com>> wrote:
> > 
> >     From: Yunseong Kim <yskelg@...il.com <mailto:yskelg@...il.com>>
> > 
> >     This patch resolve this warning.
> > 
> >     tools/perf/util/evsel.c:1620:9: error: result of comparison of constant
> >     -1 with expression of type 'char' is always false
> >      -Werror,-Wtautological-constant-out-of-range-compare
> >      1620 |                 if (c == -1)
> >           |                     ~ ^  ~~
> > 
> >     Add handling on unread_unwind_spec_debug_frame().
> >     This make caller find_proc_info() works well when the allocation
> >     failure.
> > 
> >     Signed-off-by: Yunseong Kim <yskelg@...il.com <mailto:yskelg@...il.com>>
> > 
> > 
> > 
> > Both changes look good. Could you make them 2 commits? If so add my: 
> 
> No problem! I'll send it right away.
> 
> Thank you for the code review.
> 
> > Reviewed-by: Ian Rogers <irogers@...gle.com <mailto:irogers@...gle.com>>

You forgot to add Ian's Reviewed-by in the next patches.
I can add it to them this time, but please do so next time.

Thanks,
Namhyung

> > 
> > Thanks, 
> > Ian
> > 
> >     ---
> >      tools/perf/util/evsel.c                  | 2 +-
> >      tools/perf/util/unwind-libunwind-local.c | 5 +++++
> >      2 files changed, 6 insertions(+), 1 deletion(-)
> > 
> >     diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> >     index 25857894c047..bc603193c477 100644
> >     --- a/tools/perf/util/evsel.c
> >     +++ b/tools/perf/util/evsel.c
> >     @@ -1620,7 +1620,7 @@ static int evsel__read_group(struct evsel
> >     *leader, int cpu_map_idx, int thread)
> > 
> >      static bool read_until_char(struct io *io, char e)
> >      {
> >     -       char c;
> >     +       int c;
> > 
> >             do {
> >                     c = io__get_char(io);
> >     diff --git a/tools/perf/util/unwind-libunwind-local.c
> >     b/tools/perf/util/unwind-libunwind-local.c
> >     index cde267ea3e99..a424eae6d308 100644
> >     --- a/tools/perf/util/unwind-libunwind-local.c
> >     +++ b/tools/perf/util/unwind-libunwind-local.c
> >     @@ -390,6 +390,11 @@ static int read_unwind_spec_debug_frame(struct
> >     dso *dso,
> >                             char *debuglink = malloc(PATH_MAX);
> >                             int ret = 0;
> > 
> >     +                       if (debuglink == NULL) {
> >     +                               pr_err("unwind: Can't read unwind
> >     spec debug frame.\n");
> >     +                               return -ENOMEM;
> >     +                       }
> >     +
> >                             ret = dso__read_binary_type_filename(
> >                                     dso, DSO_BINARY_TYPE__DEBUGLINK,
> >                                     machine->root_dir, debuglink, PATH_MAX);
> >     -- 
> >     2.44.0
> > 
> 
> Warm Regards,
> Yunseong Kim