When does Emacs Lisp's lexical-let leak memory?

Question

I read about lexical-let's memory leak, for example here: Are there any problems with lexical-let or other cl-macros??? - Users list for the GNU Emacs text editor - ArchiveOrange

It says:

"Note that variables bound with lexical-let are never released, even if they are never used. Try

(loop for i from 1 to 100000 collect (lexical-let ((x i)) '()))

and watch it eat memory."

But I think this code eats memory just because the list made by loop grows. So, I wrote a few elisp codes to check when it occurs but I could not find a example of the leak.

This is how memory grows with time when I execute the code below.

(require 'cl)

(defvar num-loop-1 30)
(defvar num-loop-2 100000)

(loop for i from 1 to num-loop-1 do
      (loop for j from 1 to num-loop-2 collect
            (lexical-let ((x `(,i ,j))) (lambda () x))))

It looks like there is no leak.

See more examples here: https://gist.github.com/1703325

ADDED: This is how the first example eats memory. As I said, I think it is an artifact.

Answer 1

I just found this in emacs-devel:

When does Emacs Lisp's lexical-let leak memory? So... Is it true, that "variables bound with lexical-let are never released, even if they are never used"?

Not that I know. Of course, this code is not bug-free, but I don't know of any concrete case that bumps into such a bug.

-- Re: lexical-let cause memory leaks?