Hi, Yep, that seems to be the problem. So Gcc 7 (and I guess gcc 8) with -O2 and our code seems to optimise into a problem. Thanks. bruce -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.squeakfoundation.org/pipermail/vm-dev/attachments/20191021/799e51cc/attachment.html>