checkdoc-defun is an interactive autoloaded compiled Lisp function in `checkdoc.el'.

(checkdoc-defun &optional NO-ERROR)

Examine the doc string of the function or variable under point.
Call `error' if the doc string has problems. If NO-ERROR is
non-nil, then do not call error, but call `message' instead.
If the doc string passes the test, then check the function for rogue white
space at the end of each line.