Subject: 24.3; Sanity check of ARGLIST when calling `defun'
From: Nicolas Richard <[email-masked]>
To: [email-masked]
Date: Fri, 25 Oct 2013 14:27:06 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

Hello,

As suggested here http://permalink.gmane.org/gmane.emacs.help/94196 I
attach a patch to make (defun ...) check that the arglist is an actual
list of symbols when defining a function, and otherwise signal an error.

Without this, code like (defun test-foobar ...) succeeds although the
function is doomed to fail at runtime.

This won't catch every missing "arglist" but that looks impossible
anyway.

diff --git a/lisp/emacs-lisp/byte-run.el b/lisp/emacs-lisp/byte-run.el
index 0bb0495..d671892 100644
--- a/lisp/emacs-lisp/byte-run.el
+++ b/lisp/emacs-lisp/byte-run.el
@@ -180,6 +180,10 @@ The return value is undefined.
   ;; from
   ;;    (defun foo (arg) (toto)).
   (declare (doc-string 3))
+  (if (null
+       (and (listp arglist)
+            (null (delq t (mapcar #'symbolp arglist)))))
+      (error "Malformed arglist: %s" arglist))
   (let ((decls (cond
                 ((eq (car-safe docstring) 'declare)
                  (prog1 (cdr docstring) (setq docstring nil)))
@@ -209,7 +213,7 @@ The return value is undefined.
                     nil)
                    (t (message "Warning: Unknown defun property `%S' in %S"
                                (car x) name)))))
-                   decls))
+            decls))
           (def (list 'defalias
                      (list 'quote name)
                      (list 'function
-- 
1.8.1.5

It was also suggested in that thread by P.J. Bourguignon to use
alternate methods, but both required parts of cl (for "every" and
"dolist"), hence I'm submitting this version (and checked that "make
bootstrap" succeeds).

Another version would be something along the lines of:
  (mapc (function (lambda (elt)
                    (if (null (symbolp elt))
                        (error "Malformed arglist: %s" arglist))))
        (if (listp arglist)
            arglist
          '("")))
but it doesn't look more efficient from my (very limited) test.

-- 
Nico.