From c2d22bfbe6ece13e0d7fa8293030573fd8ce2abf Mon Sep 17 00:00:00 2001
From: PatR <rankin@nethack.org>
Date: Sun, 15 Sep 2024 16:49:59 -0700
Subject: [PATCH] glob vs hider fix

Caught by 'sanity_check':  hides-under monster hiding under nothing
after the glob it was under coalesced with an adjacent one.  Tricky
to test because dropped, thrown, or kicked globs will always merge
with the one being hidden under.  Needed to kill the type of monster
that drops the type of glob since it gets created on the floor so
is eligible to draw in the existing one.
---
 src/mkobj.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/mkobj.c b/src/mkobj.c
index ea14e4c5d..f980f2ee3 100644
--- a/src/mkobj.c
+++ b/src/mkobj.c
@@ -952,8 +952,7 @@ mksobj_init(struct obj *otmp, boolean artif)
                need to perform any fix up and returns glob->owt as-is */
             otmp->owt = objects[otmp->otyp].oc_weight;
             otmp->known = otmp->dknown = 1;
-            otmp->corpsenm = PM_GRAY_OOZE
-                           + (otmp->otyp - GLOB_OF_GRAY_OOZE);
+            otmp->corpsenm = PM_GRAY_OOZE + (otmp->otyp - GLOB_OF_GRAY_OOZE);
             start_glob_timeout(otmp, 0L);
         } else {
             if (otmp->otyp != CORPSE && otmp->otyp != MEAT_RING
@@ -3656,16 +3655,19 @@ obj_absorb(struct obj **obj1, struct obj **obj2)
 /*
  * Causes the heavier object to absorb the lighter object in
  * most cases, but if one object is OBJ_FREE and the other is
- * on the floor, the floor object goes first.
+ * on the floor, the floor object goes first.  Note that when
+ * a globby monster dies, its corpse (new glob) will be created
+ * on the floor; when a glob is dropped, thrown, or kicked it
+ * in will be free at the time obj_meld() gets called.
  *
- * wrapper for obj_absorb so that floor_effects works more
- * cleanly (since we don't know which we want to stay around)
+ * Wrapper for obj_absorb() so that floor_effects works more
+ * cleanly (since we don't know which we want to stay around).
  */
 struct obj *
 obj_meld(struct obj **obj1, struct obj **obj2)
 {
     struct obj *otmp1, *otmp2, *result = 0;
-    int ox, oy;
+    int ox, oy; /* coordinates for the glob that goes away */
 
     if (obj1 && obj2) {
         otmp1 = *obj1;
@@ -3695,8 +3697,14 @@ obj_meld(struct obj **obj1, struct obj **obj2)
             }
             /* callers really ought to take care of this; glob melding is
                a bookkeeping issue rather than a display one */
-            if (ox && cansee(ox, oy))
-                newsym(ox, oy);
+            if (ox) {
+                if (cansee(ox, oy))
+                    newsym(ox, oy);
+                /* and this; a hides-under monster might be hiding under
+                   the glob that went away; if there's nothing else there
+                   to hide under, force it out of hiding */
+                maybe_unhide_at(ox, oy);
+            }
         }
     } else {
         impossible("obj_meld: not called with two actual objects");