/in/foo.c: In function 'main':
/in/foo.c:7:6: warning: 'n' is used uninitialized in this function [-Wuninitialized]
    if(i<=n)
      ^
/in/foo.c:9:9: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
      sum+=i*i;
      ~~~^~~~~