foo.cc: In function ‘int main()’:
foo.cc:8:23: warning: ‘n’ is used uninitialized [-Wuninitialized]
    8 |         for (int i=1;i<=n;i++)
      |                      ~^~~
foo.cc:7:9: note: ‘n’ was declared here
    7 |     int n,sum;
      |         ^
foo.cc:12:28: warning: ‘sum’ may be used uninitialized [-Wmaybe-uninitialized]
   12 |                         sum+=i;
      |                         ~~~^~~
foo.cc:7:11: note: ‘sum’ was declared here
    7 |     int n,sum;
      |           ^~~