bug#34686: 26.1; unload-feature doesn't remove functions locally from hooks

bug#34686: 26.1; unload-feature doesn't remove functions locally from hooks

[Braun Gábor]

Create in the current directory the following two files:

------------------------- test.el -------------------------------------
(with-temp-buffer
  (load-file "./test-unload.el")
  (add-hook 'test-hook #'test-function nil t)
  (unload-feature 'test-unload)
  (run-hooks 'test-hook))
-----------------------------------------------------------------------

------------------------- test-unload.el ------------------------------
(defun test-function () "Test function, does nothing." nil)
(provide 'test-unload)
-----------------------------------------------------------------------

Start Emacs via

emacs -Q --eval '(setq debug-on-error t)' -l test.el

Expectation: Emacs starts up with no error.
(`unload-feature' should remove `test-function' from `test-hook' as
documented, so `(run-hooks 'test-hook)' should be a no-op.)

A split frame is shown with buffer *Backtrace* having the following 
content:

-------------------- buffer *Backtrace* -------------------------------
Debugger entered--Lisp error: (void-function test-function)
  test-function()
  run-hooks(test-hook)
  (progn (load-file "./test-unload.el") (add-hook 'test-hook (function 
test-function) nil t) (unload-feature 'test-unload) (run-hooks 'test-
hook))
  (unwind-protect (progn (load-file "./test-unload.el") (add-hook 'test-
hook (function test-function) nil t) (unload-feature 'test-unload) (run-
hooks 'test-hook)) (and (buffer-name temp-buffer) (kill-buffer temp-
buffer)))
  (save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(load-file "./test-unload.el") (add-hook 'test-hook (function test-
function) nil t) (unload-feature 'test-unload) (run-hooks 'test-hook)) 
(and (buffer-name temp-buffer) (kill-buffer temp-buffer))))
  (let ((temp-buffer (generate-new-buffer " *temp*"))) (save-current-
buffer (set-buffer temp-buffer) (unwind-protect (progn (load-file "./
test-unload.el") (add-hook 'test-hook (function test-function) nil t) 
(unload-feature 'test-unload) (run-hooks 'test-hook)) (and (buffer-name 
temp-buffer) (kill-buffer temp-buffer)))))
  eval-buffer(#<buffer  *load*> nil "/run/shm/test.el" nil t)  ; Reading 
at buffer position 155
  load-with-code-conversion("/run/shm/test.el" "/run/shm/test.el" nil t)
  load("/run/shm/test.el" nil t)
  command-line-1(("--eval" "(setq debug-on-error t)" "-l" "test.el"))
  command-line()
  normal-top-level()
-----------------------------------------------------------------------

Best wishes,

     Gábor Braun

System information:

In GNU Emacs 26.1 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.2)
 of 2018-12-26, modified by Debian built on x86-ubc-01
Windowing system distributor 'The X.Org Foundation', version 
11.0.12003000
System Description:	Debian GNU/Linux buster/sid

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading /run/shm/test-unload.el (source)...done
Entering debugger...

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --enable-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.1/site-
lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.1/site-lisp:/
usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --build
 x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
 --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.1/site-
lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.1/site-lisp:/
usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --with-x=yes
 --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -fdebug-prefix-map=/build/emacs-3ThesY/emacs-26.1+1=. -fstack-
protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 THREADS LIBSYSTEMD LCMS2

Important settings:
  value of $LANG: hu_HU.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Debugger

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq dired
dired-loaddefs format-spec rfc822 mml mml-sec password-cache epa derived
epg epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils help-mode
easymenu cl-print debug loadhist byte-opt gv bytecomp byte-compile
cl-loaddefs cl-lib cconv elec-pair time-date mule-util tooltip eldoc
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel term/x-win
x-win term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
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button faces cus-face macroexp files text-properties overlay sha1 md5
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backquote dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 99661 8330)
 (symbols 48 20573 1)
 (miscs 40 65 104)
 (strings 32 28942 1190)
 (string-bytes 1 759566)
 (vectors 16 14967)
 (vector-slots 8 500780 7422)
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 (buffers 992 14))

bug#34686: 26.1; unload-feature doesn't remove functions locally from hooks

[Eli Zaretskii]

> From: Braun Gábor <braungb88@gmail.com>
> Date: Sat, 23 Feb 2019 22:16:45 +0100
> 
> Create in the current directory the following two files:
> 
> ------------------------- test.el -------------------------------------
> (with-temp-buffer
>   (load-file "./test-unload.el")
>   (add-hook 'test-hook #'test-function nil t)
>   (unload-feature 'test-unload)
>   (run-hooks 'test-hook))
> -----------------------------------------------------------------------
> 
> ------------------------- test-unload.el ------------------------------
> (defun test-function () "Test function, does nothing." nil)
> (provide 'test-unload)
> -----------------------------------------------------------------------
> 
> Start Emacs via
> 
> emacs -Q --eval '(setq debug-on-error t)' -l test.el
> 
> Expectation: Emacs starts up with no error.
> (`unload-feature' should remove `test-function' from `test-hook' as
> documented, so `(run-hooks 'test-hook)' should be a no-op.)

Where do you see it documented that the hook should be removed?  All I
see is this:

  Standard unloading activities include restoring old autoloads for
  functions defined by the library, undoing any additions that the
  library has made to hook variables or to ‘auto-mode-alist’[...]

This says that hooks are removed if they were added by the library
being unloaded.  But in your example, the hook was not added by
test-unload.el, it was added by test.el, a different library.

bug#34686: 26.1; unload-feature doesn't remove functions locally from hooks

[Robert Pluim]

Eli Zaretskii <eliz@gnu.org> writes:

>> Expectation: Emacs starts up with no error.
>> (`unload-feature' should remove `test-function' from `test-hook' as
>> documented, so `(run-hooks 'test-hook)' should be a no-op.)
>
> Where do you see it documented that the hook should be removed?  All I
> see is this:
>
>   Standard unloading activities include restoring old autoloads for
>   functions defined by the library, undoing any additions that the
>   library has made to hook variables or to ‘auto-mode-alist’[...]
>
> This says that hooks are removed if they were added by the library
> being unloaded.  But in your example, the hook was not added by
> test-unload.el, it was added by test.el, a different library.

In "(elisp) Unloading" it says:

     Before restoring the previous definitions, ‘unload-feature’ runs
     ‘remove-hook’ to remove functions in the library from certain
     hooks.  These hooks include variables whose names end in ‘-hook’
     (or the deprecated suffix ‘-hooks’), plus those listed in
     ‘unload-feature-special-hooks’, as well as ‘auto-mode-alist’.  This
     is to prevent Emacs from ceasing to function because important
     hooks refer to functions that are no longer defined.

and a quick look at the code confirms that it at least *tries* to do
that.

Robert

bug#34686: 26.1; unload-feature doesn't remove functions locally from hooks

[Robert Pluim]

(please donʼt drop the bug address from the CC)

Braun Gábor <braungb88@gmail.com> writes:

> Hi,
>
>> > Standard unloading activities include restoring old autoloads for
>> > functions defined by the library, undoing any additions that the
>> > library has made to hook variables or to ‘auto-mode-alist’[...]
>
> Obviously, this part of the docstring of unload-feature contradicts
> the info manual.
>  
>> In "(elisp) Unloading" it says:
>> 
>>      Before restoring the previous definitions, ‘unload-feature’ runs
>>      ‘remove-hook’ to remove functions in the library from certain
>>      hooks.  These hooks include variables whose names end in ‘-hook’
>>      (or the deprecated suffix ‘-hooks’), plus those listed in
>>      ‘unload-feature-special-hooks’, as well as ‘auto-mode-alist’.  This
>>      is to prevent Emacs from ceasing to function because important
>>      hooks refer to functions that are no longer defined.
>> 
>> and a quick look at the code confirms that it at least *tries* to do
>> that.
>
> And as far as I understand the code, it does remove functions from the 
> global value of the hooks, but not from the buffer-local values.
>
> IMHO, the stated reason in the info manual (keep Emacs functioning) 
> justifies removing functions from the hooks (both their global and local 
> values) which become undefined.

Yes, Iʼd tend to agree. Would you have a patch to offer?

Thanks

Robert

bug#34686: 26.1; unload-feature doesn't remove functions locally from hooks

[Braun Gábor]

> > IMHO, the stated reason in the info manual (keep Emacs functioning)
> > justifies removing functions from the hooks (both their global and 
local
> > values) which become undefined.
> 
> Yes, Iʼd tend to agree. Would you have a patch to offer?

What about the following?

Gábor

--- lisp/loadhist.el	2019-02-28 20:52:14.852487704 +0100
+++ lisp/loadhist.el	2019-02-28 20:51:40.008386599 +0100
@@ -295,7 +295,13 @@
 	     (dolist (y unload-function-defs-list)
 	       (when (and (eq (car-safe y) 'defun)
 			  (not (get (cdr y) 'autoload)))
-		 (remove-hook x (cdr y)))))))
+		 (let ((f (cdr y)))
+		   (remove-hook x f)
+		   ;; Remove also from buffer-local value.
+		   (save-current-buffer
+		     (dolist (buf (buffer-list))
+		       (set-buffer buf)
+		       (remove-hook x f t)))))))))
 	;; Remove any feature-symbols from auto-mode-alist as well.
 	(dolist (y unload-function-defs-list)
 	  (when (and (eq (car-safe y) 'defun)