From caa8aa7f60ebb8eb7d5f1e5fa1ddfdef9f821a0c Mon Sep 17 00:00:00 2001
From: nhmall <nhmall@nethack.org>
Date: Sat, 16 Dec 2023 12:55:09 -0500
Subject: [PATCH] reinstate obj guard on _see_with_infrared macro

Checking the callers:
newsym() the use of see_with_infrared() is guarded by
    } else if ((mon = m_at(x, y)) != 0 [...]

do_mgivenname() the use of see_with_infrared is guarded by !mtmp:
        && (!mtmp
            || (!sensemon(mtmp)
                && (!(cansee(cx, cy) || see_with_infrared(mtmp))

howmonseen(mon) dereferences mon in other places, so it would
    segfault if mon were NULL; howmonseen has NONNULLARG1.
---
 include/display.h | 2 +-
 src/vision.c      | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/display.h b/include/display.h
index ee4958905..b97b1d8e4 100644
--- a/include/display.h
+++ b/include/display.h
@@ -104,7 +104,7 @@
  * canseemon() or canspotmon() which already check that.
  */
 #define _see_with_infrared(mon) \
-    (!Blind && Infravision && mon && infravisible(mon->data) \
+    (!Blind && Infravision && infravisible(mon->data) \
      && couldsee(mon->mx, mon->my))
 
 /*
diff --git a/src/vision.c b/src/vision.c
index 341ef9c57..d670c3a38 100644
--- a/src/vision.c
+++ b/src/vision.c
@@ -2131,6 +2131,7 @@ howmonseen(struct monst *mon)
     int xraydist = (u.xray_range < 0) ? -1 : (u.xray_range * u.xray_range);
     unsigned how_seen = 0; /* result */
 
+    /* assert(mon != NULL) */
     /* normal vision;
        cansee is true for both normal and astral vision,
        but couldsee it not true for astral vision */