NFD » ndn-cxx

ndn::Data d;
std::cout << d;

results in:

boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<ndn::Signature::Error> >: Signature is invalid

I think it's quite unexpected that an operator<< throws in this case, or in any other case where the object being printed is not valid according to the network protocol, but doesn't violate any class invariants (if it did, the constructor should have thrown). Instead, I'd expect operator<< to print "invalid signature" and not throw any exceptions.