post-command-hook is a variable defined in `C source code'.
Its value is
(vcursor-post-command eldoc-schedule-timer)

  • This variable may be risky if used as a file-local variable.

Normal hook run after each command is executed.
If an unhandled error happens in running this hook,
the function in which the error occurred is unconditionally removed, since
otherwise the error might happen repeatedly and make Emacs nonfunctional.