Error(s):

source_file.cpp:14:19: error: 'A' is not polymorphic
  void* pointer = dynamic_cast<void*>(&a); // is this value well-defined?
                  ^                   ~~
source_file.cpp:16:6: error: 'B' is not polymorphic
  if(dynamic_cast<void*>(&b) == dynamic_cast<void*>(base_ptr))
     ^                   ~~
source_file.cpp:16:33: error: 'A' is not polymorphic
  if(dynamic_cast<void*>(&b) == dynamic_cast<void*>(base_ptr))
                                ^                   ~~~~~~~~
3 errors generated.