This concerns Beyond Zork release 60, although other versions may well be affected. This version can be found at Zarf’s Obsessively Complete Inform Catalog.
This came via a Spatterlight bug report which includes steps to reproduce, including a save file to get right to the problematic section.
What’s happening is that @get_prop_addr is being called with object number 41920, which is not valid. I’ve tried tracking down why this is occurring, in hopes to dynamically patch the problematic code to not use invalid objects. What I’ve found follows.
Routine fd84, 5 locals fd85: 52 01 31 04 GET_PROP_ADDR L00,#31 -> L03
The call site:
2fbfa: f9 00 3f 61 a3 c0 ab b2 d3 24 CALL_VN fd84 ("circlet","film","zzzp")
The source code for this can be found at the Obsessively Complete list. From what I can tell, the following function is the offender (i.e. is the code at 0xfd85):
<ROUTINE REPLACE-SYN? (OBJ OLD NEW "AUX" TBL LEN) <SET TBL <GETPT .OBJ ,P?SYNONYM>> <COND (<ZERO? .TBL> <RFALSE>)> <SET LEN </ <PTSIZE .TBL> 2>> <REPEAT () <COND (<DLESS? LEN 0> <RFALSE>) (<EQUAL? <GET .TBL .LEN> .OLD> <PUT .TBL .LEN .NEW> <RTRUE>)>>>
<ROUTINE KILL-FILM () <UNMAKE ,CIRCLET ,SEEN> <REPLACE-SYN? ,W?CIRCLET ,W?FILM ,W?ZZZP> <REPLACE-ADJ? ,W?CIRCLET ,W?SWIRLING ,W?ZZZP> <RFALSE>>
At this point I’ve exhausted my ability to track this down. Does anybody more well-versed in ZIL see what could be causing this? ,W?CIRCLET seems to be the “wrong” value here, but I’m not sure at all how it could be so.