Subject: bug#60768: 30.0.50; edebug-instrument-function off by one

From: No Wayman <[email-masked]>
Date: Thu, 13 Jul 2023 08:03:55 -0400

Eli Zaretskii <[email-masked]> writes:

>> From: No Wayman <[email-masked]>
>> Date: Thu, 12 Jan 2023 21:27:06 -0500
>> 
>> 1. Save the following elisp to /tmp/test.el:
>> 
>> 
>> --8<---------------cut 
>> here---------------start------------->8---
>> ;; -*- lexical-binding: t; -*-
>> 
>> ;;;###autoload
>> (defun one ()
>>   "ONE"
>>   (1+ 0))
>> 
>> (defun two ()
>>   "TWO"
>>   (1+ (one)))
>> 
>> (defun three ()
>>   "THREE"
>>   (1+ (two)))
>> 
>> (provide 'test)
>> --8<---------------cut 
>> here---------------end--------------->8---
>> 
>> 2. Run emacs from the command line with the following:
>> 
>> emacs -Q --batch -l /tmp/test.el --eval "(progn (require 
>> 'edebug) 
>> (edebug-instrument-function #'one))"
>> 
>> Expected output: Edebug: one
>> Actual output: Edebug: two
>> 
>> If you repeat the test with an additional autoload cookie added 
>> above function "two", function one is correctly instrumented.
>> 
>> If you repeat it with an autoload cookie only above function 
>> "three", function two is, incorrectly, instrumented.
>> 
>> My hunch is find-function-search-for-symbol being thrown off 
>> somehow.
>
> It's not a real problem, and it has nothing to do with the 
> autoload
> cookie, AFAICT.  If you modify edebug.el like below:
>
> diff --git a/lisp/emacs-lisp/edebug.el 
> b/lisp/emacs-lisp/edebug.el
> index 2f7d03e..0ac51ad 100644
> --- a/lisp/emacs-lisp/edebug.el
> +++ b/lisp/emacs-lisp/edebug.el
> @@ -518,6 +518,7 @@ edebug-read-top-level-form
>          ;; Don't enter Edebug while doing that, in case we're 
>          trying to
>          ;; instrument things like end-of-defun.
>          (edebug-active t))
> +    (save-excursion (end-of-defun))
>      (end-of-defun)
>      (beginning-of-defun)
>      (prog1
>
> i.e., add one call to end-of-defun whose result is thrown away, 
> before
> the _real_ call to end-of-defun, the problems go away.
>
> The reason seems to be that end-of-defun calls scan-sexps, and 
> the
> first call to scan-sexps does something that wasn't done before.
>
> Stefan, any ideas what could that be?  Any hints where to look?

Any chance of applying this workaround with a note to investigate 
more for a proper fix?