[tip:perf/core] perf pmu: Fix check for unset alias->unit array

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  b30a7d1fc96d60fe2c02e375a56a046385701d17
Gitweb:     http://git.kernel.org/tip/b30a7d1fc96d60fe2c02e375a56a046385701d17
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Wed, 15 Feb 2017 10:06:20 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 15 Feb 2017 10:06:20 -0300

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>
---
 tools/perf/util/pmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 82a654de..49bfee0 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)