> "periodically reset the refcount for immortal objects (only enable this > if a stable ABI extension is imported?)" -- that sounds quite expensive, > both at runtime and maintenance-wise.
As I understand it, the plan is to represent an immortal object by setting two high-order bits to 1. The higher bit is the actual test, and the one representing half of that is a safety margin. When reducing the reference count, CPython already checks whether the refcount's new value is 0. It could instead check whether refcount & (not !immortal_bit) is 0, which would detect when the safety margin has been reduced to 0 -- and could then add it back in. Since the bit manipulation is not conditional, the only extra branch will occur when an object is about to be de-allocated, and that might be rare enough to be an acceptable cost. (It still doesn't prevent rollover from too many increfs, but ... that should indeed be rare in the wild.) -jJ _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/O324Q4KMMXL2UHOQIZZWS52U7YHJGYEI/ Code of Conduct: http://python.org/psf/codeofconduct/
