emacs-27 aa0c679: Avoid unbounded growth of cl-random-state components (bug#38753)

[Mattias Engdegård]

branch: emacs-27
commit aa0c679f484347d20ab6f7c0f75f32f5e360cb89
Author: Mattias Engdegård <address@hidden>
Commit: Mattias Engdegård <address@hidden>

    Avoid unbounded growth of cl-random-state components (bug#38753)
    
    * lisp/emacs-lisp/cl-extra.el (cl-random):
    Perform the modulo 2**23 operation before updating the state instead
    of after.  The result is always the same, but it prevents the state
    from growing into arbitrary large bignums.
    
    Patch from Christopher Wellons.
---
 lisp/emacs-lisp/cl-extra.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/emacs-lisp/cl-extra.el b/lisp/emacs-lisp/cl-extra.el
index 7e9d8fe..2e0b37c 100644
--- a/lisp/emacs-lisp/cl-extra.el
+++ b/lisp/emacs-lisp/cl-extra.el
@@ -469,7 +469,7 @@ Optional second arg STATE is a random-state object."
          (while (< (setq i (1+ i)) 200) (cl-random 2 state))))
     (let* ((i (cl-callf (lambda (x) (% (1+ x) 55)) (cl--random-state-i state)))
           (j (cl-callf (lambda (x) (% (1+ x) 55)) (cl--random-state-j state)))
-          (n (logand 8388607 (aset vec i (- (aref vec i) (aref vec j))))))
+          (n (aset vec i (logand 8388607 (- (aref vec i) (aref vec j))))))
       (if (integerp lim)
          (if (<= lim 512) (% n lim)
            (if (> lim 8388607) (setq n (+ (ash n 9) (cl-random 512 state))))