Display a call graph of a specified file.
This lists which functions have been called, what functions called
them, and what functions they call. The list includes all functions
whose definitions have been compiled in this Emacs session, as well as
all functions called by those functions.
The call graph does not include macros, inline functions, or
primitives that the byte-code interpreter knows about directly (eq,
The call tree also lists those functions which are not known to be called
(that is, to which no calls have been compiled), and which cannot be
invoked interactively. (fn &optional FILENAME)