Max-specpdl-size Bug in Emacs Lisp Interpreter?

["Herbert Euler" <herberteuler@hotmail.com>]

Hello,

These days I read source for 'catch' and 'throw' of emacs lisp.
Then I traced into unbind-to in eval.c, and some functions
operating 'specpdl'.  I created some hypothesises to understand
them.  Since 'let' invokes 'specbind' as well, I guessed I can
verify these hypothesises with let.  Here is what I did (I'm using
Emacs Unicode 2 from CVS, latest check Apr. 8, 2006):

(defmacro create-let (n)
  (let ((i 0)
	list)
    `(let ,(progn
	     (while (< i n)
	       (setq list (cons (intern (concat "v" (number-to-string i))) list))
	       (setq i (1+ i)))
	     list)
       (message "hello"))))
     => create-let

max-specpdl-size
     => 1000

(create-let 1000)
     => [error: Variable binding depth exceeds max-specpdl-size]

max-specpdl-size
     => 1000

(create-let 1000)
     => "hello"

(create-let 2000)
     => [error: Variable binding depth exceeds max-specpdl-size]

max-specpdl-size
     => 1101

(create-let 1200)
     => "hello"

max-specpdl-size
     => 1242

I just executed them sequentially.  The behavior of last several
evaluations may be different, but they are always not correct in
my Emacs (judged by 'max-specpdl-size' should not be modified
and 'create-let' should fail if its argument exceeds 'max-specpdl
-size').

Does this imply a bug in Emacs Lisp interpreter?

Regards,
Guanpeng Xu

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