fox32rom: Add panic routine

fox32rom.def

@@ -7,6 +7,7 @@ get_mouse_position:                       jmp [0xF0040008]
 new_event:                                jmp [0xF004000C]
 wait_for_event:                           jmp [0xF0040010]
 get_next_event:                           jmp [0xF0040014]
+panic:                                    jmp [0xF0040018]
 
 ; generic drawing jump table
 draw_str_generic:                         jmp [0xF0041000]

main.asm

@@ -154,6 +154,7 @@ get_rom_version:
     #include "menu_bar.asm"
     #include "mouse.asm"
     #include "overlay.asm"
+    #include "panic.asm"
     #include "vsync.asm"
 
 
@@ -170,6 +171,7 @@ get_rom_version:
     data.32 new_event
     data.32 wait_for_event
     data.32 get_next_event
+    data.32 panic
 
     ; generic drawing jump table
     org.pad 0xF0041000

panic.asm

@@ -0,0 +1,18 @@
+; panic routines
+
+; panic and hang
+; inputs:
+; r0: pointer to null-terminated string, or zero for none
+; outputs:
+; none, does not return
+panic:
+    icl
+    brk
+    cmp r0, 0
+    ifnz mov r0, panic_string
+    call debug_print
+panic_loop:
+    jmp panic_loop
+    halt
+
+panic_string: data.str "Panic occurred!" data.8 10 data.8 0