alttypes.c:19:20: Function f2 inconsistently redeclared to return alternate
    types int | bool (types match, but alternates are not identical, so
    checking may not be correct)
   alttypes.c:17:20: Previous declaration of f2: int | void
alttypes.c:25:20: Variable x inconsistently redeclared with alternate types int
    | char (types match, but alternates are not identical, so checking may not
    be correct)
   alttypes.c:24:33: Previous declaration of x: int | char | bool

Finished checking --- 2 code warnings, as expected