START_PROCESSING* now checks processing instances

The START_PROCESSING* macros check which subsystem an already processed
 instance is being processed by.
If it is not the same as the given subsystem an error is raised.

code/__defines/MC.dm

@@ -19,7 +19,17 @@
 
 #define NEW_SS_GLOBAL(varname) if(varname != src){if(istype(varname)){Recover();qdel(varname);}varname = src;}
 
-#define START_PROCESSING(Processor, Datum) if (!Datum.is_processing) {Datum.is_processing = #Processor;Processor.processing += Datum}
+#define START_PROCESSING(Processor, Datum) \
+if (Datum.is_processing) {\
+	if(Datum.is_processing != #Processor)\
+	{\
+		crash_with("Failed to start processing. [log_info_line(Datum)] is already being processed by [Datum.is_processing] but queue attempt occured on [#Processor]."); \
+	}\
+} else {\
+	Datum.is_processing = #Processor;\
+	Processor.processing += Datum;\
+}
+
 #define STOP_PROCESSING(Processor, Datum) \
 if(Datum.is_processing) {\
 	if(Processor.processing.Remove(Datum)) {\

code/controllers/subsystems/machines.dm

@@ -3,7 +3,17 @@
 #define SSMACHINES_POWERNETS     3
 #define SSMACHINES_POWER_OBJECTS 4
 
-#define START_PROCESSING_IN_LIST(Datum, List) if (!Datum.is_processing) {Datum.is_processing = "SSmachines.[#List]"; SSmachines.List += Datum}
+#define START_PROCESSING_IN_LIST(Datum, List) \
+if (Datum.is_processing) {\
+	if(Datum.is_processing != #Processor)\
+	{\
+		crash_with("Failed to start processing. [log_info_line(Datum)] is already being processed by [Datum.is_processing] but queue attempt occured on [#Processor]."); \
+	}\
+} else {\
+	Datum.is_processing = "SSmachines.[#List]";\
+	SSmachines.List += Datum;\
+}
+
 #define STOP_PROCESSING_IN_LIST(Datum, List) \
 if(Datum.is_processing) {\
 	if(SSmachines.List.Remove(Datum)) {\