Fixes projectiles being able to hit humans in organs they do not have.

Will also prevent body shields blocking bullets with non-existant limbs. Expands on the special return values for bullet_act(), adds defines for them.

code/game/machinery/alarm.dm

@@ -919,7 +919,7 @@ FIRE ALARM
 /obj/machinery/firealarm/attack_ai(mob/user as mob)
 	return src.attack_hand(user)
 
-/obj/machinery/firealarm/bullet_act(BLAH)
+/obj/machinery/firealarm/bullet_act()
 	return src.alarm()
 
 /obj/machinery/firealarm/emp_act(severity)

code/game/objects/items/shooting_range.dm

@@ -146,7 +146,7 @@
 
 		return
 
-	return -1 // the bullet/projectile goes through the target! Ie, you missed
+	return PROJECTILE_CONTINUE // the bullet/projectile goes through the target!
 
 
 // Small memory holder entity for transparent bullet holes

code/game/objects/structures/girders.dm

@@ -25,7 +25,7 @@
 /obj/structure/girder/bullet_act(var/obj/item/projectile/Proj)
 	//Girders only provide partial cover. There's a chance that the projectiles will just pass through. (unless you are trying to shoot the girder)
 	if(Proj.original != src && !prob(cover))
-		return -1 //pass through
+		return PROJECTILE_CONTINUE //pass through
 
 	//Tasers and the like should not damage girders.
 	if(!(Proj.damage_type == BRUTE || Proj.damage_type == BURN))

code/game/objects/structures/grille.dm

@@ -94,7 +94,7 @@
 				passthrough = 1
 
 	if(passthrough)
-		. = -1
+		. = PROJECTILE_CONTINUE
 		damage = between(0, (damage - Proj.damage)*(Proj.damage_type == BRUTE? 0.4 : 1), 10) //if the bullet passes through then the grille avoids most of the damage
 
 	src.health -= damage*0.2

code/modules/mob/living/carbon/human/human_defense.dm

@@ -10,9 +10,11 @@ emp_act
 
 /mob/living/carbon/human/bullet_act(var/obj/item/projectile/P, var/def_zone)
 
-	var/obj/item/organ/external/organ = get_organ(check_zone(def_zone))
-	if(!organ)
-		return
+	def_zone = check_zone(def_zone)
+	if(!has_organ(def_zone))
+		return PROJECTILE_FORCE_MISS //if they don't have the organ in question then the projectile just passes by.
+
+	var/obj/item/organ/external/organ = get_organ()
 
 	//Shields
 	if(check_shields(P.damage, "the [P.name]"))
@@ -37,7 +39,7 @@ emp_act
 					// redirect the projectile
 					P.redirect(new_x, new_y, curloc, src)
 
-				return -1 // complete projectile permutation
+				return PROJECTILE_CONTINUE // complete projectile permutation
 
 	//Shrapnel
 	if(P.can_embed())

code/modules/projectiles/projectile.dm

@@ -166,13 +166,16 @@
 	//roll to-hit
 	miss_modifier = max(15*(distance-2) - round(15*accuracy) + miss_modifier, 0)
 	var/hit_zone = get_zone_with_miss_chance(def_zone, target_mob, miss_modifier, ranged_attack=(distance > 1 || original != target_mob)) //if the projectile hits a target we weren't originally aiming at then retain the chance to miss
-	if(!hit_zone)
+	
+	var/result = PROJECTILE_FORCE_MISS
+	if(hit_zone)
+		def_zone = hit_zone //set def_zone, so if the projectile ends up hitting someone else later (to be implemented), it is more likely to hit the same part
+		result = target_mob.bullet_act(src, def_zone)
+	
+	if(result == PROJECTILE_FORCE_MISS)
 		visible_message("<span class='notice'>\The [src] misses [target_mob] narrowly!</span>")
 		return 0
 
-	//set def_zone, so if the projectile ends up hitting someone else later (to be implemented), it is more likely to hit the same part
-	def_zone = hit_zone
-
 	//hit messages
 	if(silenced)
 		target_mob << "<span class='danger'>You've been hit in the [parse_zone(def_zone)] by \the [src]!</span>"
@@ -193,7 +196,7 @@
 			msg_admin_attack("UNKNOWN shot [target_mob] ([target_mob.ckey]) with \a [src] (<A HREF='?_src_=holder;adminplayerobservecoodjump=1;X=[target_mob.x];Y=[target_mob.y];Z=[target_mob.z]'>JMP</a>)")
 
 	//sometimes bullet_act() will want the projectile to continue flying
-	if (target_mob.bullet_act(src, def_zone) == -1)
+	if (result == PROJECTILE_CONTINUE)
 		return 0
 
 	return 1
@@ -227,7 +230,7 @@
 		else
 			passthrough = 1 //so ghosts don't stop bullets
 	else
-		passthrough = (A.bullet_act(src, def_zone) == -1) //backwards compatibility
+		passthrough = (A.bullet_act(src, def_zone) == PROJECTILE_CONTINUE) //backwards compatibility
 		if(isturf(A))
 			for(var/obj/O in A)
 				O.bullet_act(src)

code/setup.dm

@@ -720,6 +720,10 @@ var/list/be_special_flags = list(
 #define FILE_DRM            16 // Some files want to not be copied/moved. This is them complaining that you tried.
 #define NETWORK_FAILURE     32
 
+// Special return values from bullet_act(). Positive return values are already used to indicate the blocked level of the projectile.
+#define PROJECTILE_CONTINUE   -1 //if the projectile should continue flying after calling bullet_act()
+#define PROJECTILE_FORCE_MISS -2 //if the projectile should treat the attack as a miss (suppresses attack and admin logs) - only applies to mobs.
+
 // Some on_mob_life() procs check for alien races.
 #define IS_DIONA  1
 #define IS_VOX    2