RE: Max-specpdl-size Bug in Emacs Lisp Interpreter?

[Herbert Euler]

Having read "(elisp)Local Variables", I know that it is a known feature.
But if so I think the name 'max-specpdl-size' should be altered, since
normally a maximum value needs explicitly change, i.e. there should be
a particular function to change a maximum value.  Such a way that
change it implicitly would makes people who don't know about it
confused about its "maximum" trait.

Regards,
Guanpeng Xu


> From: "Herbert Euler" <address@hidden>
> To: address@hidden
> Subject: Max-specpdl-size Bug in Emacs Lisp Interpreter?
> Date: Sat, 15 Apr 2006 16:24:56 +0800
>
> 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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