D380 - A fault in this project's own code names the nearest implementation

Status: decided Date: 2026-08-29

A fault address inside this project's own binary is reported against the nearest preceding entry in a sorted table of implementation start addresses, printed as a name plus offset; a formatted string argument is followed only when it falls inside a range the run has published, and prints as unmapped otherwise.

Why: The binary carries no symbols and is relocated per run, so a raw fault address is meaningless on its own; the nearest implementation and its distance says whether the fault is inside a routine or in support code called from one. Following every pointer a guest passes is right for guest-computed addresses but wrong for uninitialized stack contents an overflowing format string exposes; there the honest answer is that the address is not known to be valid, not an invented placeholder string.

Rejected:

• Reporting only the last import called: names which function the guest wanted, not where the fault actually is.
• Dereferencing every string argument unconditionally: an address outside every published range is not safe to read and not worth guessing at.