If we:

1. heap allocate a struct-based helix object (e.g. Duration::new)
2. GC runs

It will GC the Ruby object associated with the helix object, because the GC couldn't see the VALUE pointer on the stack

See sparklemotion/nokogiri@0a1556a
and http://blog.reverberate.org/2016/06/12/native-extensions-memory-management-part1-ruby-mri.html