re:
(defvar *default-special-bindings* nil
"This variable holds an alist associating special variable symbols
to forms to evaluate. Special variables named in this list will
be locally bound in the new thread before it begins executing user
code.
This variable may be rebound around calls to MAKE-THREAD to
add/alter default bindings. The effect of mutating this list is
undefined, but earlier forms take precedence over later forms for
the same symbol, so defaults may be overridden by consing to the
head of the list.")
at least for sbcl and clozure, one needs to append to the list.
does the spec say something else somewhere?
* (progv '(a s a) '(1 2 3) a)
; in: LAMBDA NIL
; (PROGV '(A S A) '(1 2 3) A)
; --> LET UNWIND-PROTECT FLET BLOCK MULTIPLE-VALUE-BIND MULTIPLE-
VALUE-CALL
; --> BLOCK SB-C::%WITHIN-CLEANUP RETURN-FROM
; ==>
; (PROGN
; (LABELS ((#:UNBIND1 (SB-C::VARS)
; (DECLARE #)
; (LET #
; #))
; (#:BIND0 (SB-C::VARS SB-C::VALS)
; (DECLARE #)
; (COND # # #)))
; (#:BIND0 '(A S A) '(1 2 3)))
; NIL
; A)
;
; caught WARNING:
; undefined variable: A
;
; compilation unit finished
; Undefined variable:
; A
; caught 1 WARNING condition
3
*