René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inconsistency handling of immortal objects in gc","articleBody":"# Bug report\n\n### Bug description:\n\nThere is some inconsistency in handling of immortal objects in default-build's GC.\n\nIn `update_refs` immortal objects just untracked (all immortal objects that we face in GC is an accidentally immortalized). https://github.com/python/cpython/blob/1e69cd1634e4f0f8c375be85d11925bd12deef23/Python/gc.c#L495-L500\n\n`update_refs` called for all collections (young, increment and full). But for incremental collection if `increment_size \u003c gcstate-\u003ework_to_do` we steal some objects from neighbor gen and call `expand_region_transitively_reachable` where immortal objects moved to permanent generation: https://github.com/python/cpython/blob/1e69cd1634e4f0f8c375be85d11925bd12deef23/Python/gc.c#L1397-L1402\n\nSo, one part of immortal objects can be untracked, and other part can be moved to perm gen. \n\nAs I understand from https://github.com/python/cpython/pull/127519 it is preferring to untrack immortal objects in all cases.\n\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-137111\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/sergey-miryanov","@type":"Person","name":"sergey-miryanov"},"datePublished":"2025-07-25T19:08:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/137110/cpython/issues/137110"}