On 3/26/14 6:44 PM, Francesco Abbate wrote: > Hi Richard, > > thank you very much this is going to help me, for the foment I'm > working to obtain the same bytecode generated by luajit. > > I guess the flag gets defined during parsing in lj_parse.c, I'll give a look. Yep, pretty much everything you need happens in lj_parse.c. If it were me, I'd probably mark upvalues during `ctx:op_uset()` inside bytecode.lua with a `uval.mutable = true` or something and then fix the flags during `write_body` where it's being done now. Probably a 4 line change in total ;-)