From 82337beeddbb30a895f2d9fb16ca757077d2966d Mon Sep 17 00:00:00 2001
From: Michael Meyer <me@entrez.cc>
Date: Wed, 21 Sep 2022 22:19:42 -0400
Subject: [PATCH] Prevent impossible fall dmg if falling up

The way hole destinations work now theoretically allows for a
cross-branch hole or trap door to move you across branches in a way that
decreases your overall depth.  If this happened, it would cause an
impossible when the negative result of (depth(new) - depth(old)) was
used to calculate fall damage.  Limit fall damage to 1d6 if dist <= 0.
---
 src/do.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/do.c b/src/do.c
index 3f1ee04c3..9e2fd69a3 100644
--- a/src/do.c
+++ b/src/do.c
@@ -1822,7 +1822,7 @@ goto_level(
 
     /* fall damage? */
     if (do_fall_dmg) {
-        int dmg = d(dist, 6);
+        int dmg = d(max(dist, 1), 6);
 
         dmg = Maybe_Half_Phys(dmg);
         losehp(dmg, "falling down a mine shaft", KILLED_BY);