http://jqyzxhjk6psc6ul5jnfwloamhtyh7si74b4743k2qgpskwwxrzhsxmad.onion/docs/faq.html.en
If you can't find a core, run "ulimit -c unlimited", restart Tor, and try
to make it crash again. (This core thing will only work on Unix -- alas,
tracking down bugs on Windows is harder. If you're on Windows, can you get
somebody to duplicate your bug on Unix?)