1. Start Emacs with emacs -Q
2. Evaluate the following Lisp code:
;; Define a keymap
(defvar my-dummy-map (make-keymap))
;; Now use the remap feature to remap delete-backward-char
(define-key my-dummy-map
(vector 'remap 'delete-backward-char) 'backward-char)
;; Create a buffer and actually install that map. This step
;; seems to be necessary for the bug to occcur.
(switch-to-buffer (get-buffer-create "foo"))
(use-local-map my-dummy-map)
3. Now, start calc with `M-x calc RET'.
4. If you now check the definition of the DEL key, for example with
`C-h k DEL', you will see that in calc-mode, this key is now bound
to `backward-char', even though the remapping was done in
`my-dummy-map'. When calc binds the DEL key, it actually scans the
global map for any key bound to `delete-backward-char' using
(where-is-internal 'delete-backward-char global-map)
This search seems to fail after the code above, i.e. something
seems to have changed in global map which should not have changed.
Nothing has changed in global-map. When I do the same call to
where-is-internal in some other buffer, it correctly returns ([127]).