-;;; an internal tag for marking empty slots
-;;;
-;;; CMU CL 18b used :EMPTY for this purpose, which was somewhat nasty
-;;; since it's easily accessible to the user, so that e.g.
-;;; (DEFVAR *HT* (MAKE-HASH-TABLE))
-;;; (SETF (GETHASH :EMPTY *HT*) :EMPTY)
-;;; (MAPHASH (LAMBDA (K V) (FORMAT T "~&~S ~S~%" K V)))
-;;; gives no output -- oops!
-;;;
-;;; Note that as of version 0.6.6 there's a dependence in the gencgc.c
-;;; code on this value being a symbol. (This is only one of many nasty
-;;; dependencies between that code and this, alas.)
-(defconstant +empty-ht-slot+ '%empty-ht-slot%)
-;;; KLUDGE: Using a private symbol still leaves us vulnerable to users
-;;; getting nonconforming behavior by messing around with
-;;; DO-ALL-SYMBOLS. That seems like a fairly obscure problem, so for
-;;; now we just don't worry about it. If for some reason it becomes
-;;; worrisome and the magic value needs replacement:
-;;; * The replacement value needs to be LOADable with EQL preserved,
-;;; so that macroexpansion for WITH-HASH-TABLE-ITERATOR will work
-;;; when compiled into a file and loaded back into SBCL.
-;;; (Thus, just uninterning %EMPTY-HT-SLOT% doesn't work.)
-;;; * The replacement value needs to be acceptable to the
-;;; low-level gencgc.lisp hash table scavenging code.
-;;; * The change will break binary compatibility, since comparisons
-;;; against the value used at the time of compilation are wired
-;;; into FASL files.
-;;; -- WHN 20000622
-