Check validity of rx submatch-n number

* lisp/emacs-lisp/rx.el (rx-submatch): Type and range check (Bug#34373).

diff --git a/lisp/emacs-lisp/rx.el b/lisp/emacs-lisp/rx.el
index 8ef78fd69e6a6ed063a54db3a598cda8c93fd12b..2130e3e1aea23c919ce3dfabf981d1422abbe5ba 100644 (file)
--- a/lisp/emacs-lisp/rx.el
+++ b/lisp/emacs-lisp/rx.el
@@ -725,6 +725,8 @@ FORM is either `(repeat N FORM1)' or `(repeat N M FORMS...)'."
 (defun rx-submatch-n (form)
   "Parse and produce code from FORM, which is `(submatch-n N ...)'."
   (let ((n (nth 1 form)))
+    (unless (and (integerp n) (> n 0))
+      (error "rx `submatch-n' argument must be positive"))
     (concat "\\(?" (number-to-string n) ":"
            (if (= 3 (length form))
                ;; Only one sub-form.