Rewrite get_sched_policy_name for safety.

This way you'll get a build time error if you make the usual mistake of
adding to the enum but not adding an entry to the array.

Also improve the unit tests, and fix get_sched_policy_name's incorrect
behavior on invalid inputs.

Bug: N/A
Test: ran tests
Change-Id: Iefcb1ec9ef66267837da7a576c8be3d0cfb16cd0

1 files changed, 7 insertions, 6 deletions

diff --git a/libcutils/sched_policy.cpp b/libcutils/sched_policy.cpp
index f72ec52d6..3fa548f78 100644
--- a/libcutils/sched_policy.cpp
+++ b/libcutils/sched_policy.cpp
@@ -25,6 +25,7 @@
 #include <string.h>
 #include <unistd.h>
 
+#include <android-base/macros.h>
 #include <log/log.h>
 
 /* Re-map SP_DEFAULT to the system default policy, and leave other values unchanged.
@@ -460,16 +461,16 @@ int get_sched_policy(int /*tid*/, SchedPolicy* policy) {
 
 #endif
 
-const char *get_sched_policy_name(SchedPolicy policy)
-{
+const char* get_sched_policy_name(SchedPolicy policy) {
     policy = _policy(policy);
-    static const char* const strings[SP_CNT] = {
+    static const char* const kSchedPolicyNames[] = {
             [SP_BACKGROUND] = "bg", [SP_FOREGROUND] = "fg", [SP_SYSTEM] = "  ",
             [SP_AUDIO_APP] = "aa",  [SP_AUDIO_SYS] = "as",  [SP_TOP_APP] = "ta",
             [SP_RT_APP] = "rt",     [SP_RESTRICTED] = "rs",
     };
-    if ((policy < SP_CNT) && (strings[policy] != NULL))
-        return strings[policy];
-    else
+    static_assert(arraysize(kSchedPolicyNames) == SP_CNT, "missing name");
+    if (policy < SP_BACKGROUND || policy >= SP_CNT) {
         return "error";
+    }
+    return kSchedPolicyNames[policy];
 }