Minor mode that highlights suspicious C and C++ constructions.
Suspicious constructs are highlighted using `font-lock-warning-face'.
Note, in addition to enabling this minor mode, the major mode must
be included in the variable `cwarn-configuration'. By default C and
C++ modes are included.
With a prefix argument ARG, enable the mode if ARG is positive,
and disable it otherwise. If called from Lisp, enable the mode
if ARG is omitted or nil. (fn &optional ARG)