This was tested using `https://github.com/node-dot-cpp/alloc-test` plus a few other by-hand tests.
It seems to work for the case we care about (sysmodules without thread cache-ing).
External users are advised to build with assertions on and contact SciresM if you find issues.
This is a lot of code to have gotten right in one go, and it was written mostly after midnight while sick, so there are probably un-noticed issues.
