Mike Ash 406ebaddfc [Runtime] Implement overflow check for weak refcounts (#14023) ...

* Check for overflow in incrementWeak().

This mirrors what is currently done for unowned reference counts, where overflowing the side table field produces a fatal error. Without this, the count silently wrapped from 2^31-1 to 0, which then caused breakage when the balancing releases happened (possibly including use-after-free bugs).

* Fix the implementation of RefCounts::getWeakCount().

The previous implementation was only appropriate for heap objects, but not side tables. This resulted in the weak count always returning 0 or 1. This change specializes the implementation for the two different cases and returns the correct count for side tables.

* Test large weak retain counts.

This tests the largest allowed weak retain count, as well as the overflow check when that count is exceeded.

2018-01-19 19:13:47 -08:00

7.2 KiB

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