/in/foo.cc: In function 'int main()':
/in/foo.cc:6:11: warning: variable 'a3' set but not used [-Wunused-but-set-variable]
  int a[3],a3,a4;
           ^~
/in/foo.cc:6:14: warning: variable 'a4' set but not used [-Wunused-but-set-variable]
  int a[3],a3,a4;
              ^~
/in/foo.cc:22:2: warning: 'a1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if(a1==a2)
  ^~
/in/foo.cc:22:2: warning: 'a2' may be used uninitialized in this function [-Wmaybe-uninitialized]