/in/foo.cc: In function 'int dao(int)':
/in/foo.cc:9:2: error: return-statement with no value, in function returning 'int' [-fpermissive]
  return;
  ^~~~~~
/in/foo.cc:5:10: warning: unused variable 'b' [-Wunused-variable]
  int m,r,b;
          ^