perf pmu: Fix check for unset alias->unit array

The alias->unit field is an array, so to check that it is not set we
should see if it is an empty string, i.e. alias->unit[0], instead of
checking alias->unit != NULL, as this will _always_ evaluate to 'true'.

Pointed out by clang.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/20170214182435.GD4458@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 82a654dec666..49bfee0e3d9e 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -945,12 +945,12 @@ static int check_info_data(struct perf_pmu_alias *alias,
          * define unit, scale and snapshot, fail
          * if there's more than one.
          */
-        if ((info->unit && alias->unit) ||
+        if ((info->unit && alias->unit[0]) ||
             (info->scale && alias->scale) ||
             (info->snapshot && alias->snapshot))
                 return -EINVAL;
 
-        if (alias->unit)
+        if (alias->unit[0])
                 info->unit = alias->unit;
 
         if (alias->scale)