bug#36431: Crash in marker.c:337

[Stefan Monnier]

> OK, I finally saw that we don't actually call set-buffer-multibyte but
> instead we just set bset_enable_multibyte_characters.  I'm beginning to
> understand better.

Alright, so here one way to make this "transient" inconsistent state
escape its transientness (should it be "transienticity"?) and crash Emacs:

    (catch 'toto
      (let ((set-auto-coding-function (lambda (rest _) (throw 'toto nil))))
        (erase-buffer)
        (insert-file-contents "~/tmp/foo-c3c3.txt")))
        
where `~/tmp/foo-c3c3.txt` is a file that contains some invalid
utf-8 byte sequence (in my case I used two bytes C3 together).


        Stefan