/in/foo.cc: In function 'void dfs(TreeNode&, TreeNode&, int&)':
/in/foo.cc:26:42: warning: self-comparison always evaluates to true [-Wtautological-compare]
  if(n0.r == n1.r && n0.l == n1.l && n0.v == n0.v)
                                     ~~~~~^~~~~~~
/in/foo.cc: In function 'int comp(TreeNode*, TreeNode*)':
/in/foo.cc:39:6: warning: unused variable 'eq' [-Wunused-variable]
  int eq = 0;
      ^~
/in/foo.cc:42:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^