Fixing a hang that would occur when there is incorrectly set time zone data in the windows registry. (case 1256569)

Author: UnityAlex

mcs/class/corlib/System/TimeZoneInfo.WinRT.cs

@@ -61,6 +61,7 @@ internal struct DYNAMIC_TIME_ZONE_INFORMATION
 
 		internal const uint TIME_ZONE_ID_INVALID = 0xffffffff;
 		internal const uint ERROR_NO_MORE_ITEMS = 259;
+		internal const uint ERROR_SUCCESS = 0;
 
 		[DllImport ("api-ms-win-core-timezone-l1-1-0.dll")]
 		internal extern static uint EnumDynamicTimeZoneInformation (uint dwIndex, out DYNAMIC_TIME_ZONE_INFORMATION lpTimeZoneInformation);
@@ -349,7 +350,7 @@ internal static List<TimeZoneInfo> GetSystemTimeZonesWinRTFallback ()
 			try {
 				uint index = 0;
 				DYNAMIC_TIME_ZONE_INFORMATION dtzi;
-				while (EnumDynamicTimeZoneInformation (index++, out dtzi) != ERROR_NO_MORE_ITEMS) {
+				while (EnumDynamicTimeZoneInformation (index++, out dtzi) == ERROR_SUCCESS) {
 					var timeZoneInfo = TryCreateTimeZone (dtzi);
 					if (timeZoneInfo != null)
 						result.Add (timeZoneInfo);
@@ -358,8 +359,6 @@ internal static List<TimeZoneInfo> GetSystemTimeZonesWinRTFallback ()
 				// EnumDynamicTimeZoneInformation() might not be available.
 			}
 
-			if (result.Count == 0)
-				result.Add (Local);
 			return result;
 		}
 	}

mcs/class/corlib/System/TimeZoneInfo.cs

@@ -787,6 +787,10 @@ public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 			if (systemTimeZones == null) {
 				var tz = new List<TimeZoneInfo> ();
 				GetSystemTimeZonesCore (tz);
+				// Don't want to return an empty list if we can help it
+				// but we don't want to stack overflow via a CreateLocal loop
+				if (tz.Count == 0 && local != null)
+					tz.Add(Local);
 				Interlocked.CompareExchange (ref systemTimeZones, new ReadOnlyCollection<TimeZoneInfo> (tz), null);
 			}