ldebug.c in Lua 5.4.0 allows a negation overflow and segmentation fault in getlocal and setlocal, as demonstrated by getlocal(3,2^31).
Lua 5.4.0 (fixed in 5.4.1) has a segmentation fault in changedline in ldebug.c (e.g., when called by luaGtraceexec) because it incorrectly expects that an oldpc value is always updated upon a return of the flow of control to a function.