Infidel goes wild

A critical memory‑corruption bug has been uncovered in Infocom’s 1985 interactive fiction title Infidel, specifically in the Macintosh update (release 22, serial 840522). The flaw lies in the routine that tracks objects dropped in the game’s “ENDLESS‑DESERT” area, where the program stores latitude‑longitude coordinates and object IDs in a fixed‑size array called DESERT‑TABLE. Because of a wild‑pointer error, the routine writes data to the wrong memory locations, overwriting unrelated memory and potentially destabilising the Z‑machine interpreter; the same defect also exists in the original release (serial 830916) with slightly different address offsets.

The bug is especially pernicious because it is virtually invisible during normal play. The desert mechanic, inherited from Enchanter, treats every unmapped location as a single room, shifting dropped items into DESERT‑TABLE and retrieving them when the player returns to the same coordinates. However, the routine’s loop fails to populate the table at all, leaving it empty while objects appear to move correctly, making detection difficult without a low‑level memory debugger. The author, a C programmer, notes that such memory corruption is considered a severe fault, and that the problem originates from a compiler issue in the ZIL code that generates the Z‑machine bytecode.

Because the error resides in the core object‑management system, it could affect any playthrough that involves dropping items in the endless desert, potentially leading to unpredictable behavior or crashes on affected machines. The discovery highlights the challenges of preserving and debugging legacy interactive‑fiction engines, especially when source‑level tools are scarce. It also serves as a reminder that even well‑known classics can harbor deep technical flaws that only surface under detailed inspection, prompting renewed interest in reverse‑engineering and fixing vintage game code.

⚡ Effects Interpreter