/in/foo.cc: In function 'int main()':
/in/foo.cc:5:9: warning: unused variable 'a' [-Wunused-variable]
  double a,b,c;
         ^
/in/foo.cc:5:11: warning: variable 'b' set but not used [-Wunused-but-set-variable]
  double a,b,c;
           ^
/in/foo.cc:5:13: warning: unused variable 'c' [-Wunused-variable]
  double a,b,c;
             ^