From cc46da90e00e54b99f45b8cd1d9d69e7efe0f52c Mon Sep 17 00:00:00 2001
From: Michael Meyer <me@entrez.cc>
Date: Fri, 1 Jul 2022 12:29:47 -0400
Subject: [PATCH] Fix #812: recovered stair dlevel

Stair dlevels weren't being restored with the correct values when
recovered after the game crashed, apparently because they weren't being
reset back to their 'absolute' level from a 'relative' level.  I'm not
totally sure of why this affected only recovered games (maybe that's the
only time when the 'relative' stair values are used?) but this fix seems
to work.

Fixes #812
---
 include/hack.h | 5 +++++
 src/restore.c  | 7 +++++--
 src/save.c     | 6 ++++--
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/hack.h b/include/hack.h
index 6b14d5e86..a57a53059 100644
--- a/include/hack.h
+++ b/include/hack.h
@@ -254,6 +254,11 @@ enum saveformats {
     ascii = 3           /* each field, ascii text (just proof of concept) */
 };
 
+enum restore_stages {
+    REST_GSTATE = 1,    /* restoring current level and game state */
+    REST_LEVELS = 2,    /* restoring remainder of dungeon */
+};
+
 /* sortloot() return type; needed before extern.h */
 struct sortloot_item {
     struct obj *obj;
diff --git a/src/restore.c b/src/restore.c
index e328f9084..0ffe4e2f3 100644
--- a/src/restore.c
+++ b/src/restore.c
@@ -749,7 +749,7 @@ dorecover(NHFILE* nhfp)
     int rtmp;
 
     /* suppress map display if some part of the code tries to update that */
-    g.program_state.restoring = 1;
+    g.program_state.restoring = REST_GSTATE;
 
     get_plname_from_file(nhfp, g.plname);
     getlev(nhfp, 0, (xint8) 0);
@@ -776,6 +776,8 @@ dorecover(NHFILE* nhfp)
     if (rtmp < 2)
         return rtmp; /* dorecover called recursively */
 
+    g.program_state.restoring = REST_LEVELS;
+
     /* these pointers won't be valid while we're processing the
      * other levels, but they'll be reset again by restlevelstate()
      * afterwards, and in the meantime at least u.usteed may mislead
@@ -909,7 +911,8 @@ rest_stairs(NHFILE* nhfp)
         if (nhfp->structlevel) {
             mread(nhfp->fd, (genericptr_t) &stway, sizeof (stairway));
         }
-        if (stway.tolev.dnum == u.uz.dnum) {
+        if (g.program_state.restoring != REST_GSTATE
+            && stway.tolev.dnum == u.uz.dnum) {
             /* stairway dlevel is relative, make it absolute */
             stway.tolev.dlevel += u.uz.dlevel;
         }
diff --git a/src/save.c b/src/save.c
index ddf39c207..b8f5939e8 100644
--- a/src/save.c
+++ b/src/save.c
@@ -717,7 +717,9 @@ save_stairs(NHFILE* nhfp)
 
     while (stway) {
         if (perform_bwrite(nhfp)) {
-            if (stway->tolev.dnum == u.uz.dnum) {
+            boolean use_relative = (g.program_state.restoring != REST_GSTATE
+                                    && stway->tolev.dnum == u.uz.dnum);
+            if (use_relative) {
                 /* make dlevel relative to current level */
                 stway->tolev.dlevel -= u.uz.dlevel;
             }
@@ -725,7 +727,7 @@ save_stairs(NHFILE* nhfp)
                 bwrite(nhfp->fd, (genericptr_t) &buflen, sizeof buflen);
                 bwrite(nhfp->fd, (genericptr_t) stway, sizeof *stway);
             }
-            if (stway->tolev.dnum == u.uz.dnum) {
+            if (use_relative) {
                 /* reset staiway dlevel back to absolute */
                 stway->tolev.dlevel += u.uz.dlevel;
             }