I encountered a weird bug with deserializing JSON in a JRuby app during an OpenJDK upgrade - it would sporadically throw a parse error for no apparent reason. I was upgrading to OpenJDK 15, but another user experienced the same regression with an LTS upgrade from 8 to 11.
The end result of my own investigation led to this quite satisfying thread on hotspot-compiler-dev, in which an engineer starts with my minimal reproduction of the problem and posts a workaround within 24 hours: https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2021...
There's also a tip there: try a fastdebug build and see if you can convert it into an assertion failure you can look up.
The end result of my own investigation led to this quite satisfying thread on hotspot-compiler-dev, in which an engineer starts with my minimal reproduction of the problem and posts a workaround within 24 hours: https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2021...
There's also a tip there: try a fastdebug build and see if you can convert it into an assertion failure you can look up.