foo.cc: In function ‘int main()’:
foo.cc:9:18: warning: ‘s’ may be used uninitialized [-Wmaybe-uninitialized]
    9 |                 s+=i;
      |                 ~^~~
foo.cc:5:19: note: ‘s’ was declared here
    5 |         int x1,x2,s;
      |                   ^