Better align drop_throw with hero ammo breakage

There is a comment above the function indicating that it should be
aligned with hero ammo breakage, but this wasn't the case.  One big
difference is that any monster-thrown or -shot object would be deleted
unconditionally if it hit another monster trapped in a pit.  I don't
know why that was in there, but it's not present in hero ammo breakage
chances, and it meant that a monster could sling the Mines luckstone at
the hero, hit a monster in the pit, and permanently lock the hero out of
getting the luckstone (as just happened to a player during the current
tournament).  This pulls the hero breakage rules out into their own
function and uses that for monster breakage as well, to make sure they
are aligned.  I also refactored drop_throw a bit to reduce the number of
separate variables tracking whether the object was deleted (was create,
objgone, and retvalu), and changed its (and ohitmon's) type to boolean.

include/extern.h

@@ -667,6 +667,7 @@ extern boolean harmless_missile(struct obj *);
 extern boolean throwing_weapon(struct obj *);
 extern void throwit(struct obj *, long, boolean, struct obj *);
 extern int omon_adj(struct monst *, struct obj *, boolean);
+extern boolean should_mulch_missile(struct obj *);
 extern int thitmonst(struct monst *, struct obj *);
 extern int hero_breaks(struct obj *, coordxy, coordxy, unsigned);
 extern int breaks(struct obj *, coordxy, coordxy);
@@ -1824,7 +1825,7 @@ extern void Delay(int);
 extern const char *rnd_hallublast(void);
 extern boolean m_has_launcher_and_ammo(struct monst *);
 extern int thitu(int, int, struct obj **, const char *);
-extern int ohitmon(struct monst *, struct obj *, int, boolean);
+extern boolean ohitmon(struct monst *, struct obj *, int, boolean);
 extern void thrwmu(struct monst *);
 extern int spitmu(struct monst *, struct attack *);
 extern int breamu(struct monst *, struct attack *);

src/dothrow.c

@@ -1926,6 +1926,35 @@ tmiss(struct obj *obj, struct monst *mon, boolean maybe_wakeup)
       || (obj->otyp == FAKE_AMULET_OF_YENDOR && !obj->known))   \
      && mon->m_id == gq.quest_status.leader_m_id)
 
+/* whether or not object should be destroyed when it hits its target */
+boolean
+should_mulch_missile(struct obj *obj)
+{
+    boolean broken;
+    int chance;
+
+    /* only ammo (excluding magic stones) or missiles will break */
+    if (!obj || !(is_ammo(obj) || is_missile(obj))
+        || objects[obj->otyp].oc_magic)
+        return FALSE;
+
+    /* we had been breaking 2/3 of everything unconditionally.  we still don't
+       want anything to survive unconditionally, but we need ammo to stay
+       around longer on average. */
+    chance = 3 + greatest_erosion(obj) - obj->spe;
+    broken = chance > 1 ? rn2(chance) : !rn2(4);
+    if (obj->blessed && (gc.context.mon_moving ? !rn2(3) : !rnl(4)))
+        broken = FALSE;
+
+    /* Flint and hard gems don't break easily */
+    if (((obj->oclass == GEM_CLASS && objects[obj->otyp].oc_tough)
+         || obj->otyp == FLINT)
+        && !rn2(2))
+        broken = FALSE;
+
+    return broken;
+}
+
 /*
  * Object thrown by player arrives at monster's location.
  * Return 1 if obj has disappeared or otherwise been taken care of,
@@ -2141,34 +2170,11 @@ thitmonst(
             /* projectiles other than magic stones sometimes disappear
                when thrown; projectiles aren't among the types of weapon
                that hmon() might have destroyed so obj is intact */
-            if (objects[otyp].oc_skill < P_NONE
+            if (should_mulch_missile(obj)) {
-                && objects[otyp].oc_skill > -P_BOOMERANG
+                if (*u.ushops || obj->unpaid)
-                && !objects[otyp].oc_magic) {
+                    check_shop_obj(obj, gb.bhitpos.x, gb.bhitpos.y, TRUE);
-                /* we were breaking 2/3 of everything unconditionally.
+                obfree(obj, (struct obj *) 0);
-                 * we still don't want anything to survive unconditionally,
+                return 1;
-                 * but we need ammo to stay around longer on average.
-                 */
-                int broken, chance;
-
-                chance = 3 + greatest_erosion(obj) - obj->spe;
-                if (chance > 1)
-                    broken = rn2(chance);
-                else
-                    broken = !rn2(4);
-                if (obj->blessed && !rnl(4))
-                    broken = 0;
-
-                /* Flint and hard gems don't break easily */
-                if (((obj->oclass == GEM_CLASS && objects[otyp].oc_tough)
-                     || obj->otyp == FLINT) && !rn2(2))
-                    broken = 0;
-
-                if (broken) {
-                    if (*u.ushops || obj->unpaid)
-                        check_shop_obj(obj, gb.bhitpos.x, gb.bhitpos.y, TRUE);
-                    obfree(obj, (struct obj *) 0);
-                    return 1;
-                }
             }
             passive_obj(mon, obj, (struct attack *) 0);
         } else {

src/mthrowu.c

@@ -9,7 +9,7 @@ static int monmulti(struct monst *, struct obj *, struct obj *);
 static void monshoot(struct monst *, struct obj *, struct obj *);
 static boolean ucatchgem(struct obj *, struct monst *);
 static const char* breathwep_name(int);
-static int drop_throw(struct obj *, boolean, coordxy, coordxy);
+static boolean drop_throw(struct obj *, boolean, coordxy, coordxy);
 static int m_lined_up(struct monst *, struct monst *);
 
 #define URETREATING(x, y) \
@@ -152,51 +152,43 @@ thitu(
 
 /* Be sure this corresponds with what happens to player-thrown objects in
  * dothrow.c (for consistency). --KAA
- * Returns 0 if object still exists (not destroyed).
+ * Returns FALSE if object still exists (not destroyed).
  */
-static int
+static boolean
 drop_throw(
     register struct obj *obj,
     boolean ohit,
     coordxy x,
     coordxy y)
 {
-    int retvalu = 1;
+    boolean broken;
-    int create;
-    struct monst *mtmp;
-    struct trap *t;
 
     if (obj->otyp == CREAM_PIE || obj->oclass == VENOM_CLASS
-        || (ohit && obj->otyp == EGG))
+        || (ohit && obj->otyp == EGG)) {
-        create = 0;
+        broken = TRUE;
-    else if (ohit && (is_multigen(obj) || obj->otyp == ROCK))
+    } else {
-        create = !rn2(3);
+        broken = (ohit && should_mulch_missile(obj));
-    else
+    }
-        create = 1;
-
-    if (create && !((mtmp = m_at(x, y)) != 0 && mtmp->mtrapped
-                    && (t = t_at(x, y)) != 0
-                    && is_pit(t->ttyp))) {
-        int objgone = 0;
 
+    if (broken) {
+        delobj(obj);
+    } else {
         if (down_gate(x, y) != -1)
-            objgone = ship_object(obj, x, y, FALSE);
+            broken = ship_object(obj, x, y, FALSE);
-        if (!objgone) {
+        if (!broken) {
-            if (!flooreffects(obj, x, y, "fall")) {
+            struct monst *mtmp = m_at(x, y);
+            if (!(broken = flooreffects(obj, x, y, "fall"))) {
                 place_object(obj, x, y);
                 if (!mtmp && u_at(x, y))
                     mtmp = &gy.youmonst;
                 if (mtmp && ohit)
                     passive_obj(mtmp, obj, (struct attack *) 0);
                 stackobj(obj);
-                retvalu = 0;
             }
         }
-    } else {
-        delobj(obj);
     }
     gt.thrownobj = 0;
-    return retvalu;
+    return broken;
 }
 
 /* calculate multishot volley count for mtmp throwing otmp (if not ammo) or
@@ -318,7 +310,7 @@ monshoot(struct monst* mtmp, struct obj* otmp, struct obj* mwep)
    return 1 if the object has stopped moving (hit or its range used up)
    can anger the monster, if this happened due to hero (eg. exploding
    bag of holding throwing the items) */
-int
+boolean
 ohitmon(
     struct monst *mtmp, /* accidental target, located at <gb.bhitpos.x,.y> */
     struct obj *otmp,   /* missile; might be destroyed by drop_throw */
@@ -328,8 +320,7 @@ ohitmon(
     boolean verbose)/* give message(s) even when you can't see what happened */
 {
     int damage, tmp;
-    boolean vis, ismimic;
+    boolean vis, ismimic, objgone;
-    int objgone = 1;
     struct obj *mon_launcher = gm.marcher ? MON_WEP(gm.marcher) : NULL;
 
     gn.notonhead = (gb.bhitpos.x != mtmp->mx || gb.bhitpos.y != mtmp->my);
@@ -495,11 +486,11 @@ ohitmon(
         objgone = drop_throw(otmp, 1, gb.bhitpos.x, gb.bhitpos.y);
         if (!objgone && range == -1) { /* special case */
             obj_extract_self(otmp);    /* free it for motion again */
-            return 0;
+            return FALSE;
         }
-        return 1;
+        return TRUE;
     }
-    return 0;
+    return FALSE;
 }
 
 /* hero catches gem thrown by mon iff poly'd into unicorn; might drop it */