perf pmu: clang points out: address of array 'alias->unit' will always evaluate to 'true'

[Arnaldo Carvalho de Melo]

util/pmu.c:948:28: error: address of array 'alias->unit' will always evaluate 
to 'true' [-Werror,-Wpointer-bool-conversion]
        if ((info->unit && alias->unit) ||
                        ~~ ~~~~~~~^~~~
util/pmu.c:953:13: error: address of array 'alias->unit' will always evaluate 
to 'true' [-Werror,-Wpointer-bool-conversion]
        if (alias->unit)
        ~~  ~~~~~~~^~~~
2 errors generated.


So, is this test about having something on that alias->unit array? I.e.
should this suffice?

[acme@jouet linux]$ cat clang.patch 
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)
[acme@jouet linux]$