Remove magic number 5 in severity eventsCount

flow/Trace.cpp

@@ -1039,12 +1039,11 @@ TraceEvent& TraceEvent::GetLastError() {
 #endif
 }
 
-// We're cheating in counting, as in practice, we only use {10,20,30,40}.
-static_assert(SevMaxUsed / 10 + 1 == 5, "Please bump eventCounts[5] to SevMaxUsed/10+1");
-unsigned long TraceEvent::eventCounts[5] = {0,0,0,0,0};
+unsigned long TraceEvent::eventCounts[NUM_MAJOR_LEVELS_OF_EVENTS] = {0, 0, 0, 0, 0};
 
 unsigned long TraceEvent::CountEventsLoggedAt(Severity sev) {
-  return TraceEvent::eventCounts[sev/10];
+	ASSERT(sev <= SevMaxUsed);
+	return TraceEvent::eventCounts[sev/10];
 }
 
 TraceEvent& TraceEvent::backtrace(const std::string& prefix) {

flow/Trace.h

@@ -47,6 +47,9 @@ inline static bool TRACE_SAMPLE() { return false; }
 
 extern thread_local int g_allocation_tracing_disabled;
 
+// Each major level of severity has 10 levels of minor levels, which are not all
+// used. when the numbers of severity events in each level are counted, they are
+// grouped by the major level.
 enum Severity {
 	SevVerbose = 0,
 	SevSample = 1,
@@ -59,6 +62,8 @@ enum Severity {
 	SevMax = 1000000
 };
 
+const int NUM_MAJOR_LEVELS_OF_EVENTS = SevMaxUsed / 10 + 1;
+
 class TraceEventFields {
 public:
 	constexpr static FileIdentifier file_identifier = 11262274;
@@ -510,7 +515,7 @@ private:
 
 	void setSizeLimits();
 
-	static unsigned long eventCounts[5];
+	static unsigned long eventCounts[NUM_MAJOR_LEVELS_OF_EVENTS];
 	static thread_local bool networkThread;
 
 	bool init();