- fixed: CreateDamageFunction needs to return NULL for a damage value of 0 to preserve the collision detection handling of non-damaging actors.

SVN r3920 (scripting)

src/p_mobj.cpp

@@ -3410,7 +3410,8 @@ void AActor::Tick ()
 		// won't hurt anything. Don't do this if damage is 0! That way, you can
 		// still have missiles that go straight up and down through actors without
 		// damaging anything.
-		if ((flags & MF_MISSILE) && (velx|vely) == 0 && Damage != 0)
+		// (for backwards compatibility this must check for lack of damage function, not for zero damage!)
+		if ((flags & MF_MISSILE) && (velx|vely) == 0 && Damage != NULL)
 		{
 			velx = 1;
 		}

src/thingdef/thingdef.cpp

@@ -445,6 +445,13 @@ void LoadActors ()
 //==========================================================================
 
 VMScriptFunction *CreateDamageFunction(int dmg)
+{
+	if (dmg == 0)
+	{
+		// For zero damage, do not create a function so that the special collision detection case still works as before.
+		return NULL;
+	}
+	else
 	{
 		VMFunctionBuilder build;
 		build.Registers[REGT_POINTER].Get(1);		// The self pointer
@@ -454,3 +461,4 @@ VMScriptFunction *CreateDamageFunction(int dmg)
 		sfunc->NumArgs = 1;
 		return sfunc;
 	}
+}