## 1 `gc.c/subtract_refs` references an obsolete constant `GC_REACHABLE` https://github.com/python/cpython/blob/34d7351ac770ac49875fc39396b2a97828ba05ad/Python/gc.c#L572-L577 It is obsolete since https://github.com/python/cpython/pull/7043 ## 2 `gc.c/SCAN_RATE_DIVISOR` has obsolete comment about calculating incremental threshold based on count of survivors. It is obsolete since https://github.com/python/cpython/pull/117120 https://github.com/python/cpython/blob/34d7351ac770ac49875fc39396b2a97828ba05ad/Python/gc.c#L1345-L1362 ## 3 Reference https://github.com/python/cpython/issues/135552 instead of https://github.com/python/cpython/issues/91636 when writing about deallocated objects in the type cache. <!-- gh-linked-prs --> ### Linked PRs * gh-137563 * gh-137564 * gh-137614 <!-- /gh-linked-prs -->