Re: new fboundp behavior weird

[Vitalie Spinu]

  >> Vitalie Spinu <address@hidden>
  >> on Sun, 30 Dec 2012 11:25:25 +0100 wrote:

  >> Thierry Volpiatto <address@hidden>
  >> on Sat, 29 Dec 2012 22:36:16 +0100 wrote:

  VS> [...]

  TV> (defalias 'toto 'titi)

  TV> (debugger-special-form-p 'toto) ; Used in 24.2
  TV> =>nil ; OK

  TV> (special-form-p 'toto) ; Used in 24.3
  TV> =>
  TV> Debugger entered--Lisp error: (void-function toto)
  TV> indirect-function(toto)
  TV> (setq object (indirect-function object))
  TV> (if (and (symbolp object) (fboundp object)) (setq object 
(indirect-function object)))

  VS> Interesting. This part from emacs 24.2 debugger-special-form-p is
  VS> apparently missing:

  VS>        (subrp (symbol-function symbol))

  VS> Does that mean that emacs 24.3 has special forms that are not built-in?

Well, not really. I have just checked the trunk; indirect-function call
misses 'no-error argument. It probably should be:


Modified   lisp/subr.el
diff --git a/lisp/subr.el b/lisp/subr.el
index 1e50903..3b27e7b 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2805,7 +2805,7 @@ Otherwise, return nil."
 (defun special-form-p (object)
   "Non-nil if and only if OBJECT is a special form."
   (if (and (symbolp object) (fboundp object))
-      (setq object (indirect-function object)))
+      (setq object (indirect-function object 'no-error)))
   (and (subrp object) (eq (cdr (subr-arity object)) 'unevalled)))
 
 (defun field-at-pos (pos)

This fixes the problem.


A slightly off topic naive question. Why is the function cell void by
default and not nil? Is this useful for anything?

Vitalie