anchor.diff:  
   check_undefined_function_calls(_Config) ->
       {ok, UndefinedCalls0} = xref:analyze(xref, undefined_function_calls),
  -
       UndefinedCalls = [{find_mfa_source(Caller), format_fa(Caller), format_mfa(Target)} ||
                            {Caller, Target} <- UndefinedCalls0],
       [?CONSOLE("~s:~w: Warning ~s calls undefined function ~s\n",
  
positive.code: 
  code_path() ->
      [P || P <- code:get_path(),
            filelib:is_dir(P)].
  
  %%
  %% Ignore behaviour functions, and explicitly marked functions
  
negative.code:             ok
      end,
  
      %% Restore the original code path
      code:set_path(OrigPath),
  
      ok.
  
  foobar() ->
  