How to troubleshoot a key binding prompting for more key presses?

Question

I have a function bound to Ctrl-b, this runs a command immediately, however after some time running emacs, pressing this binding shows text C-b in the message bar, prompting for other keys to be pressed.

If I press Enter, it runs the command, otherwise it keeps accepting key and mouse input.

C-h k still shows up this key binding as being associated with the function I expect it to run.

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How to troubleshoot emacs expecting further input for a key binding?

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Edit: the command (which I wasn't sure if it was important) is to build.

(defun generic-build ()
  (interactive)
  (cond
    ((string= major-mode "c-mode")
      (call-interactively 'cmake-ide-compile))
    ((string= major-mode "c++-mode")
      (call-interactively 'cmake-ide-compile))
    )
  )

(global-set-key (kbd "C-b") 'generic-build)
(eval-after-load "evil-maps"
  (define-key evil-motion-state-map "\C-b" nil))

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Update 1:

This happens if I try to exit too, Pressing Ctrk-b, Ctrl-h shows this message.

This would have to be related to my configuration, the issue just never came up until recently.

Type SPC or ‘y’ to save the current buffer;
DEL or ‘n’ to skip the current buffer;
RET or ‘q’ to give up on the save (skip all remaining buffers);
C-g to quit (cancel the whole command);
! to save all remaining buffers;
C-r to view this buffer;
d to view changes in this buffer;
or . (period) to save the current buffer and exit.

I'm using:

(setq use-dialog-box nil)

Which has been working up until now.

Using emacs -Q, then setting (setq use-dialog-box nil) still prompts for file save.

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Update 2:

Found the root cause, posting in answer since its confusing to include here.

Answer 1

Glad to know you resolved the problem. Since your question is about troubleshooting keybindings I'd like to chip in with my key troubleshooting process.

Try using C-h b when you can't properly query C-h k for the command bound to a key.
The C-h b (M-x describe-bindings) command describes all active key bindings for the buffer.

It's easy to scan this table for any clashes with an existing prefix command. A clash of this type could explain why your key was waiting for more key stroke input.

When a problem happens only after I've been interacting with Emacs for some time this is often because I indirectly loaded features when searching for their documentation with C-h f and C-h v.

In this case comparing the output of C-h m could help find problems introduced when a new mode is loaded, maybe unexpectedly or inadvertently.

Answer 2

This problem is messages are being suppressed by this advice-function.

somehow it's not limited to ispell-init-process:

(defun message-off-advice (oldfun &rest args)
  "Quiet down messages in adviced OLDFUN."
  (let ((message-off (make-symbol "message-off")))
    (unwind-protect
    (progn
      (advice-add #'message :around #'ignore (list 'name message-off))
      (apply oldfun args))
      (advice-remove #'message message-off))))

(advice-add #'ispell-init-process :around #'message-off-advice)

See answer: https://emacs.stackexchange.com/a/36626/2418