/in/foo.cc: In function 'int main()':
/in/foo.cc:14:25: warning: array subscript i is outside array bounds of 'double [0]' [-Warray-bounds]
   14 |                 sum+=b[i]*a[i];
      |                      ~~~^
/in/foo.cc:4:8: note: while referencing 'b'
    4 | double b[]={};
      |        ^
/in/foo.cc:10:25: warning: array subscript i is outside array bounds of 'double [0]' [-Warray-bounds]
   10 |                 cin>>b[i];
      |                      ~~~^
/in/foo.cc:4:8: note: while referencing 'b'
    4 | double b[]={};
      |        ^