alt Hacker News> Is the intent to hold LuaJIT fixed against some earlier Lua version (I guess 5.1)
Yeah. PUC-Rio went in a direction that Mike Pall didn't want to follow. Something to do with garbage collector finalizers, if I remember correctly, which is a notoriously thorny issue in every language it exists.
I think it was more the extra layers of indirection added to function environment\effectively global variable access added in 5.2 .
The removal of scanning for changed userdata finalizer meta method in 5.2 is just a commonsense fix for bad design that made GC atomic phase run time, thats not incremental scale up with the number of GC userdata objects alive no matter if they have a finalizer or not.