/in/foo.cc: In function 'int main()':
/in/foo.cc:36:7: warning: unused variable 'm1' [-Wunused-variable]
   int m1, m2, m3, m4;
       ^~
/in/foo.cc:36:11: warning: unused variable 'm2' [-Wunused-variable]
   int m1, m2, m3, m4;
           ^~
/in/foo.cc:36:15: warning: unused variable 'm3' [-Wunused-variable]
   int m1, m2, m3, m4;
               ^~
/in/foo.cc:36:19: warning: unused variable 'm4' [-Wunused-variable]
   int m1, m2, m3, m4;
                   ^~