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

[AC]

On October 16, 2020 4:29:18 AM EDT, Lars Ingebrigtsen <larsi@gnus.org> wrote:
>AC <achirvasub@gmail.com> writes:
>
>> I compile emacs off the emacs-27 branch. On those machines, opening
>> certain file types results in the above error.
>>
>> For .js files for instance, the full error is 
>>
>> 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)")
>
>(This bug report unfortunately got no attention at the time.)
>
>I'm unable to reproduce this bug in Emacs 27 or Emacs 28.  Do you have
>a
>recipe for reproducing this bug, starting from "emacs -Q"?
>

Yes. 

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.