/in/foo.cc:81:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:91:13: warning: 'rt' may be used uninitialized in this function [-Wmaybe-uninitialized]
  dfs2(rt,rt);
             ^