/in/foo.cc: In function 'int main()':
/in/foo.cc:9:4: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  n = a;
  ~~^~~
/in/foo.cc:10:4: warning: 'b' is used uninitialized in this function [-Wuninitialized]
  a = b;
  ~~^~~