/in/foo.cc: In function 'int main()':
/in/foo.cc:17:21: warning: 'x3' may be used uninitialized in this function [-Wmaybe-uninitialized]
  long long sum=x1+x2+x3;
                ~~~~~^~~
/in/foo.cc:18:21: warning: 'x2' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<x1<<" "<<x2<<" "<<x3<<" "<<sum<<endl;
                     ^~~
/in/foo.cc:18:12: warning: 'x1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<x1<<" "<<x2<<" "<<x3<<" "<<sum<<endl;
            ^~~