EVENTHANDLER_FAST_DEREGISTER macro is syntactically broken (missing underscore in list symbol) and the entire FAST handler API is dead code

Summary

eventhandler.h:95-96 defines EVENTHANDLER_FAST_DEREGISTER(name, tag) as eventhandler_deregister(Xeventhandler_list ## name, tag) — the token concat produces 'Xeventhandler_list' instead of 'Xeventhandler_list_' (compare the correct form at :68/:78/:83/:93), so any use is a compile error. Grep confirms EVENTHANDLER_FAST_* have zero users in-tree: the whole fast-handler path (static lists outside the registry) is dead code that nonetheless encodes the lock-free-dispatch pattern DF-0246 lives in. Fix: delete the FAST API (preferred) or correct the typo; if kept, FAST_INVOKE must take evlist_token to close the DF-0246-class race for fast lists.

Timeline

• 2026-09-02 Discovered during pass-2 audit of subr_eventhandler.c (GLM 5.3). DF-0246 re-verified still present, not re-reported.