/in/foo.cc: In function 'node* set_union(node*, node*)':
/in/foo.cc:46:12: warning: 'p1' may be used uninitialized in this function [-Wmaybe-uninitialized]
    p1->next=tem_node;
    ~~~~~~~~^~~~~~~~~
/in/foo.cc: In function 'node* input(int)':
/in/foo.cc:73:9: warning: 'list' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return list;
         ^~~~