/in/foo.cc: In function 'int main()':
/in/foo.cc:18:9: warning: unused variable 'b' [-Wunused-variable]
  int a, b, c;
         ^
/in/foo.cc:18:12: warning: unused variable 'c' [-Wunused-variable]
  int a, b, c;
            ^
/in/foo.cc:22:6: warning: unused variable 'weishu' [-Wunused-variable]
  int weishu = 0;
      ^~~~~~
/in/foo.cc:23:7: warning: unused variable 'huiwen' [-Wunused-variable]
  bool huiwen = true;
       ^~~~~~