On Sat, 10 Jun 2017 19:15:11 -0500, Walt Farrell wrote: >On Sat, 10 Jun 2017 16:41:16 -0700, Charles Mills wrote: > >>A refreshable program may modify itself, right? REFR does not say "I don't >>modify myself" it says "you can reload me if you want." Almost >the same >>thing, but not quite. > >The key, I think, is that the system may reload the program at _any_ time, >even on the instruction immediately after it modifies itself. Therefore, there >is no _safe_ way for a refreshable program to do such a modification, as it >cannot make any assumptions about how long the modification will survive. At >least a RENT program can use serialization to allow safe modifications (FSVO >"safe"), but a REFR program doesn't have that ability. > Yet, until the advent of REFRPROT (still not the default!), REFR programs were allowed to modify themselves.
Repeating my earlier suggestion: set a flag in initialization (would CS suffice?) test the flag before and after critical code sections; re-initialize if necessary. I'm not saying it's worth it, nor that I recommend it, only that IBM allows it. At least REFRPROT should be the default. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
