/in/foo.cc: In function 'int main()':
/in/foo.cc:23:3: warning: 'a' is used uninitialized in this function [-Wuninitialized]
  f(n,a,b,c);
  ~^~~~~~~~~
/in/foo.cc:23:3: warning: 'b' is used uninitialized in this function [-Wuninitialized]
/in/foo.cc:23:3: warning: 'c' is used uninitialized in this function [-Wuninitialized]