/in/foo.cc: In function 'void work()':
/in/foo.cc:36:29: warning: 'y4' may be used uninitialized in this function [-Wmaybe-uninitialized]
   P[++cnt].x = x4, P[cnt].y = y4, P[cnt].c = i;
                    ~~~~~~~~~^~~~
/in/foo.cc:36:14: warning: 'x4' may be used uninitialized in this function [-Wmaybe-uninitialized]
   P[++cnt].x = x4, P[cnt].y = y4, P[cnt].c = i;
   ~~~~~~~~~~~^~~~