From f0220c4203d5b3ec7a300624d967534bb193df43 Mon Sep 17 00:00:00 2001
From: Pasi Kallinen <paxed@alt.org>
Date: Sun, 11 Oct 2015 20:36:28 +0300
Subject: [PATCH] Add monster data sanity checking

---
 include/extern.h |  1 +
 src/cmd.c        |  1 +
 src/mon.c        | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/include/extern.h b/include/extern.h
index 059e4fcde..7cae62d8c 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1280,6 +1280,7 @@ E int FDECL(cmap_to_type, (int));
 
 /* ### mon.c ### */
 
+E void NDECL(mon_sanity_check);
 E int FDECL(undead_to_corpse, (int));
 E int FDECL(genus, (int, int));
 E int FDECL(pm_to_cham, (int));
diff --git a/src/cmd.c b/src/cmd.c
index 7e69ee7c5..63dc9b920 100644
--- a/src/cmd.c
+++ b/src/cmd.c
@@ -3067,6 +3067,7 @@ sanity_check()
 {
     obj_sanity_check();
     timer_sanity_check();
+    mon_sanity_check();
 }
 
 #ifdef DEBUG_MIGRATING_MONS
diff --git a/src/mon.c b/src/mon.c
index 44f4c48ae..4e5be3f96 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -39,6 +39,40 @@ const char *warnings[] = {
 };
 #endif /* 0 */
 
+
+void
+sanity_check_single_mon(mtmp, msg)
+struct monst *mtmp;
+const char *msg;
+{
+    if (DEADMONSTER(mtmp)) return;
+    if ((mtmp->data < &mons[LOW_PM]) || (mtmp->data >= &mons[NUMMONS]))
+        impossible("illegal mon data (%s)", msg);
+}
+
+void
+mon_sanity_check()
+{
+    int x,y;
+    struct monst *mtmp = fmon;
+
+    while (mtmp) {
+        sanity_check_single_mon(mtmp, "fmon");
+        mtmp = mtmp->nmon;
+    }
+    for (x = 0; x < COLNO; x++)
+        for (y = 0; y < ROWNO; y++)
+            if ((mtmp = m_at(x,y)) != 0)
+                sanity_check_single_mon(mtmp, "m_at");
+
+    mtmp = migrating_mons;
+    while (mtmp) {
+        sanity_check_single_mon(mtmp, "migr");
+        mtmp = mtmp->nmon;
+    }
+}
+
+
 /* convert the monster index of an undead to its living counterpart */
 int
 undead_to_corpse(mndx)