bug#35191: 27.0.50; Error signaled by undo--wrap-and-run-primitive-undo

bug#35191: 27.0.50; Error signaled by undo--wrap-and-run-primitive-undo

[Stefan Monnier]

[-- Attachment #1: Type: text/plain, Size: 1540 bytes --]

Package: Emacs
Version: 27.0.50


Save the file below and then open it as follows:

    % emacs -Q ..../zones.el
    C-M-f C-M-b                   ;; Move before first form
    C-M-SPC M-;                   ;; Comment out first form
    C-x u                         ;; Undo last change

When I do that, I see an error message in the echo area that says:

    Changes to be undone by function different than announced

If I redo this after enabling the debugger on error, I get the following
backtrace:

Debugger entered--Lisp error: (error "Changes to be undone by function different than an...")
  signal(error ("Changes to be undone by function different than an..."))
  error("Changes to be undone by function different than an...")
  primitive-undo(1 ((apply -4 44189 44226 undo--wrap-and-run-primitive-undo 44189 44226 ((44189 . 44192) (#(" " 0 1 (fontified t)) . -44223) (#<marker (moves after insertion) in no buffer> . 1) (44222 . 44223) 44189)) nil (apply 3 44189 44223 undo--wrap-and-run-primitive-undo 44189 44223 ((#("\n" 0 1 (face font-lock-comment-face fontified t)) . 44222) (44223 . 44224) (#(";; " 0 3 (face font-lock-comment-delimiter-face fontified t)) . 44189))) nil (apply -4 44189 44226 undo--wrap-and-run-primitive-undo 44189 44226 ((44189 . 44192) (#(" " 0 1 (fontified t)) . -44223) (#<marker (moves after insertion) in no buffer> . 1) (44222 . 44223) 44189)) (t 23723 17250 171044 280000)))
  undo-more(1)
  undo(nil)
  funcall-interactively(undo nil)
  call-interactively(undo nil nil)
  command-execute(undo)



[-- Attachment #2: zones.el --]
[-- Type: application/emacs-lisp, Size: 138263 bytes --]

bug#35191: 27.0.50; Error signaled by undo--wrap-and-run-primitive-undo

[Noam Postavsky]

retitle 35191 27.0.50; undo of comment-region signals error (when comment-combine-change-calls=t)
tags 35191 + confirmed
quit

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

> Save the file below and then open it as follows:

It's enough to use a single line

    foo ;; bar

in emacs-lisp-mode.  And the problem only happens with
comment-combine-change-calls set to t (the default).

>     % emacs -Q ..../zones.el
>     C-M-f C-M-b                   ;; Move before first form
>     C-M-SPC M-;                   ;; Comment out first form
>     C-x u                         ;; Undo last change
>
> When I do that, I see an error message in the echo area that says:
>
>     Changes to be undone by function different than announced

bug#35191: 27.0.50; undo of comment-region signals error (when comment-combine-change-calls=t)

[Lars Ingebrigtsen]

Noam Postavsky <npostavs@gmail.com> writes:

>> Save the file below and then open it as follows:
>
> It's enough to use a single line
>
>     foo ;; bar
>
> in emacs-lisp-mode.  And the problem only happens with
> comment-combine-change-calls set to t (the default).
>
>>     % emacs -Q ..../zones.el
>>     C-M-f C-M-b                   ;; Move before first form
>>     C-M-SPC M-;                   ;; Comment out first form
>>     C-x u                         ;; Undo last change
>>
>> When I do that, I see an error message in the echo area that says:
>>
>>     Changes to be undone by function different than announced

I'm unable to reproduce this on the trunk (or in Emacs 27.1) -- because 

>>     C-M-SPC M-;                   ;; Comment out first form

doesn't comment anything out (it just moves point to the comment), and
then there's nothing to undo.  Is there something missing in the recipe?  

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no