On Sat, Aug 27, 2011 at 1:52 PM, Dave Abrahams <dave@boostpro.com> wrote:
on Sat Aug 27 2011, Gottlob Frege <gottlobfrege-AT-gmail.com> wrote:
There is no "synchronizes with" (standard's wording) because synch-with requires thread 2 to *read* the value written into the atomic by thread 1. We have no reads here - no if statement - so reordering doesn't matter. I don't think the standard disallows the reordering of i and j, even if they are atomics.
IIUC from the point of view of programs without undefined behavior, the standard disallows reordering in both cases.
-- Dave Abrahams BoostPro Computing http://www.boostpro.com
But without a read, there is no visible behaviour. There is probably no such thing as "reordering" in the standard. Just whether a second thread reads what a first thread wrote, and if it does, what can be assumed by that (you can assume synch-with, if you follow the rules). I guess I haven't read very closely the SC parts of the standard, where it talks about data races. I concentrated on the synch-with parts. Maybe we need a better example? Tony