Here is a proposed patch that unifies the two print-backtrace-and-quit
cases (batch mode and the failsafe). The patch is large mostly because
of required reindenting, in fact only 15-20 lines are changed. I
tested that it works as expected in batch mode, but don't know how to
test the failsafe, I never did this. Please test yourself. I also
verified that it doesn't change the normal (interactive) backtrace.

How I tested in batch mode:

$ emacs --batch --eval "(let ((debug-on-error t)) (require 'registry)
(defun bar () (bar)) (defun foo (x) (bar)) (foo (registry-db)))"

- must use `cl-prin1' for the dummy registry object;
- must properly cut out the middle from the intentionally very long backtrace.

I don't have access to Emacs repository, so I cannot apply it myself.
I can only write emails and hope that someone applies the patches or
otherwise does something about the problem.

Paul

On Sun, 5 Jan 2020 at 00:31, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> > noninteractive)" condition. In the patch I didn't try to unify your
> > "failsafe" mode with non-interactive use, since I don't really know
> > what you wrote the commit for.
>
> The commit was specifically prompted by the case mentioned in the comment:
>
>       ;; This happens for example while handling an error in code from
>       ;; early-init.el with --debug-init.
>
> I can't remember the exact previous behavior, but it was not right (you
> got neither a good *backtrace* because the GUI wasn't up, nor a clean
> stacktrace on stdout/stderr).
>
>
>         Stefan
>