[debbugs-tracker] bug#30846: closed (26.0.91; debug-watch of kill-all-local-variables triggers 'assertion failed: found == !EQ (blv->defcell, blv->valcell)')

[GNU bug Tracking System]

Your message dated Fri, 23 Mar 2018 11:29:55 -0400
with message-id <address@hidden>
and subject line Re: bug#30846: 26.0.91; debug-watch of 
kill-all-local-variables triggers 'assertion failed: found == !EQ 
(blv->defcell, blv->valcell)'
has caused the debbugs.gnu.org bug report #30846,
regarding 26.0.91; debug-watch of kill-all-local-variables triggers 'assertion 
failed: found == !EQ (blv->defcell, blv->valcell)'
to be marked as done.

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-- 
30846: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=30846
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--- Begin Message --- Subject: 26.0.91; debug-watch of kill-all-local-variables triggers 'assertion failed: found == !EQ (blv->defcell, blv->valcell)' Date: Sun, 18 Mar 2018 09:10:41 -0400

Evaluate the following from 'emacs -Q':

    (setq-local foo 1)

    ;; Simulate (debug-watch 'foo) + continue from *Backtrace*
    (add-variable-watcher 'foo (lambda (symbol newval operation where)
                                 (with-temp-buffer
                                   (kill-all-local-variables))))
    (fundamental-mode)

This results in

../../src/data.c:98: Emacs fatal error: assertion failed: found == !EQ 
(blv->defcell, blv->valcell)

Backtrace attached.  I guess it has something to do with the recursive
`kill-all-local-variables' call, although I'm not familiar enough with
the local variable machinery to say more about it.

assert-fail-backtrace.log
Description: gdb backtrace

In GNU Emacs 26.0.91 (build 54, x86_64-pc-linux-gnu, X toolkit, Xaw scroll bars)
 of 2018-03-18 built on zebian
Repository revision: 10bd3b3af8acfc226acadc654298865cffc19cc9

Configured using:
 'configure --cache-file=../../debug-config.cache 'CC=ccache gcc'
 'CFLAGS=-O0 -g3 -march=native' --enable-checking=yes
 --enable-check-lisp-object-type --with-x-toolkit=lucid
 --with-toolkit-scroll-bars --with-gif=no --with-jpeg=no'

--- End Message ---

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#30846: 26.0.91; debug-watch of kill-all-local-variables triggers 'assertion failed: found == !EQ (blv->defcell, blv->valcell)'
>
>
>
>
> Date: 
>
> Fri, 23 Mar 2018 11:29:55 -0400
>
>
>
>
> User-agent: 
>
> Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)
>
>
>
>
> Version: 27.1
>
> > The patch doesn't only fix this problem, it also changes the time at
> > which we run the watcher: in the current emacs-26 code,
>
> Installed into master,
>
>
>         Stefan
>
>
> --- End Message ---