https://github.com/s-expressionists/wscl/blob/main/wscl-issues/proposed/fill-pointer-valid-fill-pointer

--- CCL 1.12.1 -----------------------------------------------------------------
SIMPLE-ERRORs signaled.

--- ECL 23.9.9 -----------------------------------------------------------------
SIMPLE-TYPE-ERRORs signaled.

--- Clasp 2.5.0 ----------------------------------------------------------------
SIMPLE-TYPE-ERRORs signaled.

--- CLISP 2.49.92 --------------------------------------------------------------
SIMPLE-TYPE-ERRORs signaled.

--- GCL 2.6.14 -----------------------------------------------------------------
CONDITIONS::INTERNAL-SIMPLE-ERRORs signaled.
(Actually, #<CONDITIONS::INTERNAL-SIMPLE-ERROR.0> and
#<CONDITIONS::INTERNAL-SIMPLE-ERROR.1>, whatever those are.)