Hey Steve G. Bjorg,

CoreRT is being actively developed, but is still in alpha and has 285 open issues as of writing. I actually raised an issue as part of developing LambdaNative.

That issue was about the fact they hadn’t implemented Environment.SetEnvironmentVariable, which was required to implement a custom runtime properly. They turned around an implementation in 4 days which was pretty cool. In the meantime, I had to do this workaround that they suggested on the same day I raised the issue.

Under CoreRT, SetEnvironmentVariable previously threw a NotImplementedException, which means I didn’t know what was going on until that piece of code was hit. I don’t know how many other missing features or incorrectly implemented things there are (most of it seems to be copied from coreclr, but still). I wish it was all compile-time, but since it isn’t, we probably can’t call it production-ready until they release an RTM version. I have no idea how far away that is.

Having said that, I’ve been telling people I’d happily recommend it if their use case was well covered by tests. As long as it compiles and passes all the tests, there’s not much else that can go wrong™ and the performance gains are very compelling.

Personally, I haven’t run it on anything more than benchmarks and demos. Though, I did get it building and deploying through our CI/CD pipeline at work :)