Merge pull request #3867 from Citadel-Station-13/upstream-merge-32504

[MIRROR] Weakrefs

code/__DEFINES/is_helpers.dm

@@ -10,6 +10,8 @@
 
 #define isatom(A) (isloc(A))
 
+#define isweakref(D) (istype(D, /datum/weakref))
+
 //Turfs
 //#define isturf(A) (istype(A, /turf)) This is actually a byond built-in. Added here for completeness sake.
 

code/__HELPERS/unsorted.dm

@@ -1440,7 +1440,6 @@ GLOBAL_DATUM_INIT(dview_mob, /mob/dview, new)
 	var/time_low = num2hex(world.time, 3)
 
 	var/time_clock = num2hex(TICK_DELTA_TO_MS(world.tick_usage), 3)
-
 	return "{[time_high]-[time_mid]-[GUID_VERSION][time_low]-[GUID_VARIANT][time_clock]-[node_id]}"
 
 // \ref behaviour got changed in 512 so this is necesary to replicate old behaviour.

code/datums/datum.dm

@@ -4,6 +4,7 @@
     var/list/datum_components //for /datum/components
     var/ui_screen = "home"  //for tgui
     var/use_tag = FALSE
+    var/datum/weakref/weak_reference
 
 #ifdef TESTING
     var/running_find_references
@@ -15,6 +16,7 @@
 // Return the appropriate QDEL_HINT; in most cases this is QDEL_HINT_QUEUE.
 /datum/proc/Destroy(force=FALSE, ...)
 	tag = null
+	weak_reference = null	//ensure prompt GCing of weakref.
 	var/list/timers = active_timers
 	active_timers = null
 	for(var/thing in timers)

code/datums/weakrefs.dm

@@ -0,0 +1,19 @@
+
+/proc/WEAKREF(datum/input)
+	if(istype(input) && !QDELETED(input))
+		if(!input.weak_reference)
+			input.weak_reference = new /datum/weakref(input)
+		return input.weak_reference
+
+/datum/weakref
+	var/reference
+
+/datum/weakref/New(datum/thing)
+	reference = REF(thing)
+
+/datum/weakref/Destroy()
+	return QDEL_HINT_LETMELIVE	//Let BYOND autoGC thiswhen nothing is using it anymore.
+
+/datum/weakref/proc/resolve()
+	var/datum/D = locate(reference)
+	return D.weak_reference == src? D : null

code/game/area/ai_monitored.dm

@@ -2,7 +2,7 @@
 	name = "AI Monitored Area"
 	clockwork_warp_allowed = FALSE
 	var/list/obj/machinery/camera/motioncameras = list()
-	var/list/motionTargets = list()
+	var/list/datum/weakref/motionTargets = list()
 
 /area/ai_monitored/Initialize(mapload)
 	. = ..()
@@ -27,5 +27,5 @@
 	if (ismob(O) && motioncameras.len)
 		for(var/X in motioncameras)
 			var/obj/machinery/camera/cam = X
-			cam.lostTarget(O)
+			cam.lostTargetRef(WEAKREF(O))
 			return

code/game/machinery/camera/motion.dm

@@ -1,6 +1,6 @@
 /obj/machinery/camera
 
-	var/list/localMotionTargets = list()
+	var/list/datum/weakref/localMotionTargets = list()
 	var/detectTime = 0
 	var/area/ai_monitored/area_motion = null
 	var/alarm_delay = 30 // Don't forget, there's another 3 seconds in queueAlarm()
@@ -15,11 +15,11 @@
 		if (elapsed > alarm_delay)
 			triggerAlarm()
 	else if (detectTime == -1)
-		for (var/targetref in getTargetList())
-			var/mob/target = locate(targetref) in GLOB.mob_list
-			if (QDELETED(target) || target.stat == DEAD || (!area_motion && !in_range(src, target)))
+		for (var/datum/weakref/targetref in getTargetList())
+			var/mob/target = targetref.resolve()
+			if(QDELETED(target) || target.stat == DEAD || (!area_motion && !in_range(src, target)))
 				//If not part of a monitored area and the camera is not in range or the target is dead
-				lostTarget(target)
+				lostTargetRef(targetref)
 
 /obj/machinery/camera/proc/getTargetList()
 	if(area_motion)
@@ -28,22 +28,23 @@
 
 /obj/machinery/camera/proc/newTarget(mob/target)
 	if(isAI(target))
-		return 0
+		return FALSE
 	if (detectTime == 0)
 		detectTime = world.time // start the clock
 	var/list/targets = getTargetList()
-	targets |= "[REF(target)]"
-	return 1
+	targets |= WEAKREF(target)
+	return TRUE
 
 /obj/machinery/camera/Destroy()
 	var/area/ai_monitored/A = get_area(src)
+	localMotionTargets = null
 	if(istype(A))
 		A.motioncameras -= src
 	return ..()
 
-/obj/machinery/camera/proc/lostTarget(mob/target)
+/obj/machinery/camera/proc/lostTargetRef(datum/weakref/R)
 	var/list/targets = getTargetList()
-	targets -= "[REF(target)]"
+	targets -= R
 	if (targets.len == 0)
 		cancelAlarm()
 
@@ -53,19 +54,20 @@
 			if (status)
 				aiPlayer.cancelAlarm("Motion", get_area(src), src)
 	detectTime = 0
-	return 1
+	return TRUE
 
 /obj/machinery/camera/proc/triggerAlarm()
 	if (!detectTime)
-		return 0
+		return FALSE
 	for (var/mob/living/silicon/aiPlayer in GLOB.player_list)
 		if (status)
 			aiPlayer.triggerAlarm("Motion", get_area(src), list(src), src)
 	detectTime = -1
-	return 1
+	return TRUE
 
 /obj/machinery/camera/HasProximity(atom/movable/AM as mob|obj)
 	// Motion cameras outside of an "ai monitored" area will use this to detect stuff.
 	if (!area_motion)
 		if(isliving(AM))
 			newTarget(AM)
+