Merge pull request '[5.6] safely handle entities involving set_hp' (#2526) from iliekprogrammar/MineClone2:safe_entity_handling into master

Reviewed-on: MineClone2/MineClone2#2526
Reviewed-by: cora <cora@noreply.git.minetest.land>

mods/CORE/mcl_explosions/init.lua

@@ -337,7 +337,6 @@ local function trace_explode(pos, strength, raydirs, radius, info, direct, sourc
 						if not obj:is_player() then
 							return
 						end
-
 						mcl_util.deal_damage(obj, damage, {type = "explosion", direct = direct, source = source})
 
 						obj:add_velocity(vector.multiply(punch_dir, impact * 20))

mods/ENTITIES/mcl_boats/init.lua

@@ -202,6 +202,8 @@ end
 
 function boat.on_step(self, dtime, moveresult)
 	mcl_burning.tick(self.object, dtime, self)
+	-- mcl_burning.tick may remove object immediately
+	if not self.object:get_pos() then return end
 
 	self._v = get_v(self.object:get_velocity()) * get_sign(self._v)
 	local v_factor = 1

mods/ENTITIES/mcl_mobs/api.lua

@@ -3618,6 +3618,8 @@ local mob_step = function(self, dtime)
 	check_aggro(self,dtime)
 	if not self.fire_resistant then
 		mcl_burning.tick(self.object, dtime, self)
+		-- mcl_burning.tick may remove object immediately
+		if not self.object:get_pos() then return end
 	end
 
 	local pos = self.object:get_pos()

mods/ENVIRONMENT/lightning/init.lua

@@ -120,9 +120,10 @@ function lightning.strike(pos)
 	if not pos then
 		return false
 	end
-	local objects = get_objects_inside_radius(pos2, 3.5)
 	if lightning.on_strike_functions then
 		for _, func in pairs(lightning.on_strike_functions) do
+			-- allow on_strike callbacks to destroy entities by re-obtaining objects for each callback
+			local objects = get_objects_inside_radius(pos2, 3.5)
 			func(pos, pos2, objects)
 		end
 	end
@@ -174,6 +175,7 @@ lightning.register_on_strike(function(pos, pos2, objects)
 		elseif lua and lua.name == "mobs_mc:creeper" then
 			mcl_util.replace_mob(obj, "mobs_mc:creeper_charged")
 		else
+			-- WARNING: unsafe entity handling. object may be removed immediately
 			mcl_util.deal_damage(obj, 5, { type = "lightning_bolt" })
 		end
 	end

mods/ITEMS/mcl_armor/damage.lua

@@ -90,6 +90,8 @@ mcl_damage.register_modifier(function(obj, damage, reason)
 
 	if thorns_damage > 0 and reason.type ~= "thorns" and reason.source ~= obj then
 		mcl_util.deal_damage(reason.source, thorns_damage, {type = "thorns", direct = obj})
+		-- mcl_util.deal_damage may remove object immediately
+		if not reason.source:get_pos() then return end
 
 		local thorns_item = thorns_pieces[math.random(#thorns_pieces)]
 

mods/ITEMS/mcl_bows/arrow.lua

@@ -115,6 +115,8 @@ end
 
 function ARROW_ENTITY.on_step(self, dtime)
 	mcl_burning.tick(self.object, dtime, self)
+	-- mcl_burning.tick may remove object immediately
+	if not self.object:get_pos() then return end
 
 	self._time_in_air = self._time_in_air + .001
 

mods/ITEMS/mcl_bows/rocket.lua

@@ -313,6 +313,8 @@ end
 
 function ARROW_ENTITY.on_step(self, dtime)
 	mcl_burning.tick(self.object, dtime, self)
+	-- mcl_burning.tick may remove object immediately
+	if not self.object:get_pos() then return end
 
 	self._time_in_air = self._time_in_air + .001