foo.cc: In function ‘int main()’:
foo.cc:7:17: warning: right operand of comma operator has no effect [-Wunused-value]
    7 |         cin>>a,b;
      |                 ^
foo.cc:8:17: warning: ‘b’ is used uninitialized [-Wuninitialized]
    8 |         cout<<a+b;
      |                 ^
foo.cc:6:15: note: ‘b’ was declared here
    6 |         int a,b;
      |               ^