/in/foo.cc: In function 'int main()':
/in/foo.cc:6:9: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  cout<<a+b+c+d<<endl;
        ~^~
/in/foo.cc:6:9: warning: 'b' is used uninitialized in this function [-Wuninitialized]
/in/foo.cc:6:11: warning: 'c' is used uninitialized in this function [-Wuninitialized]
  cout<<a+b+c+d<<endl;
        ~~~^~
/in/foo.cc:6:14: warning: 'd' is used uninitialized in this function [-Wuninitialized]
  cout<<a+b+c+d<<endl;
              ^