Re: Odd warning about `customize-variable'

[Stefan Monnier]

Lars Ingebrigtsen [2022-05-11 12:57:20] wrote:
> org/org.el:15523:6: Warning: the function `customize-variable' might not be 
> defined at runtime.
>
> This is odd, because loaddefs has:
>
> (defalias 'customize-variable 'customize-option)
> (autoload 'customize-option "cus-edit" "\

Here's what happens:

org.el does:

    (eval-when-compile (require 'gnus-sum))

which ends up loading `message` which loads `eudc-capf` which loads
`eudc` which calls `custom-menu-create` which loads `cus-edit`.

Loading `cus-edit` (re)defines `customize-variable` as an actual
function (rather than an alias) and adds a corresponding entry in
`load-history`.

At the end of `eval-when-compile`, `byte-compile-eval` looks at that
`load-history` and (mistakenly) thinks that `customize-variable` was
previously not defined.

This is because it does:

                    (`(defun . ,f)
                     (unless (seq-some #'autoloadp
                                       (get f 'function-history))
                        (push f byte-compile-noruntime-functions)))))))))))))

so it only skips the case where the function used to be defined as an
autoload, but not when it used to be defined as an alias.

I installed the patch below which should fix this false positive,
hopefully without introducing too many false negatives.

Another way to attack the problem could be to change `defalias` so it
doesn't push any entry into `load-history` when the new value is equal
to the old one.


        Stefan


diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index cbf2659109a..de51a7731eb 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -1056,8 +1056,14 @@ byte-compile-eval
                (dolist (s xs)
                  (pcase s
                    (`(defun . ,f)
-                    (unless (seq-some #'autoloadp
-                                      (get (cdr s) 'function-history))
+                    ;; If `f' has a history, it's presumably because
+                    ;; it was already defined beforehand (typically
+                    ;; as an autoload).  It could also be because it
+                    ;; was defined twice during `form', in which case
+                    ;; we arguably should add it to b-c-noruntime-functions,
+                     ;; but it's not clear it's worth the trouble
+                    ;; trying to recognize that case.
+                    (unless (get f 'function-history)
                        (push f byte-compile-noruntime-functions)))))))))))))
 
 (defun byte-compile-eval-before-compile (form)