From b6d511be2dd6646891a47643f399e98040b0ee84 Mon Sep 17 00:00:00 2001
From: Lukas Krickl <lukas@krickl.dev>
Date: Tue, 31 Dec 2024 16:35:49 +0100
Subject: [PATCH] map: Added basic panic handler that is called when the map
 ptr is NULL

---
 src/map.s     |  7 ++++++-
 src/strings.s |  4 ++++
 src/sys.s     | 15 ++++++++++++++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/map.s b/src/map.s
index 102469a..2558ad2 100644
--- a/src/map.s
+++ b/src/map.s
@@ -186,7 +186,12 @@ room_goto:
   ld e, a
   ld a, [hl]
   ld d, a
- 
+
+  ; check if de is NULL 
+  add a, e
+  cp a, 0
+  call z, panic 
+
   call room_load_from
 
   ; its player's turn again
diff --git a/src/strings.s b/src/strings.s
index 4080d9d..6e01970 100644
--- a/src/strings.s
+++ b/src/strings.s
@@ -21,6 +21,10 @@ STR_MP:
 
 STR_GAME_OVER:
 .str "GAME OVER"
+.db 0
+
+STR_PANIC:
+.str "PANIC"
 .db 0
 
   ; print a string 0-terminated to the screen 
diff --git a/src/sys.s b/src/sys.s
index 18314b0..c30a158 100644
--- a/src/sys.s
+++ b/src/sys.s
@@ -1,8 +1,21 @@
 nohandler:
   ret
 
+  ; crashes the program 
+  ; and displays debug information on screen
 panic:
-  ret
+  ; no more interrupts
+  call disableinterrutpts
+
+  call next_vblank_wait
+
+  ; print panic message 
+  ld hl, STR_PANIC
+  ld de, SCRN0
+  call puts
+
+@loop:
+  jp @loop
 
 enableinterrupts:
   ; enable interrupts 
-- 
2.30.2