bug#43037: Eval error in the ‘c-lang-defvar’ or ‘c-lang-setvar’

[AC]

Thank you for confirming it happens!

Some additional info: I can reproduce this consistently on 3 machines, all 
running Ubuntu (20.04 and 18.04); the procedure is the same on all of them 
(compile the current emacs-27 branch from the repo). I don't know if this (the 
Ubuntu base) matters..

On the other hand, the "standard" Emacs 27.1 that comes with Arch Linux does 
not exhibit this.

On October 16, 2020 6:45:34 AM EDT, Eli Zaretskii <eliz@gnu.org> wrote:
>> Date: Fri, 16 Oct 2020 06:14:17 -0400
>> From: AC <achirvasub@gmail.com>
>> Cc: 43037@debbugs.gnu.org
>> 
>> Literally seconds ago I compiled emacs-27, started it up with 'emacs
>-Q' and then visited the blank file '~/new.js'. That error popped up.
>
>I cannot reproduce this with stock Emacs 27.1, but I can reproduce
>with the current emacs-27 branch.  The more detailed error message is
>this:
>
>Eval error in the ‘c-lang-defvar’ or ‘c-lang-setvar’ for
>‘font-lock-comment-end-skip’ (fallback source eval - js-mode compiled
>with CC Mode 5.34 but loaded with 5.34.1): (error
>"‘c-font-lock-comment-end-skip’ got no (prior) value in js-mode (might
>be a cyclic reference)")
>
>Alan, can you take a look, please?