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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add a public C-API function to iterate over GC’able objects","articleBody":"# Feature or enhancement\r\nAn API similar to:\r\n```\r\n/* Visit all live GC-capable objects, similar to gc.get_objects(None).\r\n*\r\n* Users should avoid allocating or deallocating objects on the Python heap in\r\n* the callback. */\r\ntypedef void (*gcvisitobjects_t)(PyObject *, void *);\r\nPyAPI_FUNC(void) PyGC_VisitObjects(gcvisitobjects_t callback, void *arg);\r\n```\r\n\r\nWhich could be used as:\r\n```\r\nvoid count_functions(PyObject *op, void *arg) {\r\n  if (PyFunction_Check(op)) {\r\n    (*(int*)arg)++;\r\n  }\r\n}\r\n\r\nint get_num_functions() {\r\n  int count;\r\n  PyGC_VisitObjects(count_functions, \u0026count);\r\n  return count;\r\n}\r\n```\r\n\r\n# Pitch\r\nWe have a version of this in [Cinder](https://github.com/facebookincubator/cinder) already and right now and use it to [identify all generator objects so they can be de-opted when our JIT is shutdown](https://github.com/facebookincubator/cinder/blob/cinder/3.10/Jit/pyjit.cpp#L1871). In future we plan to use it for things like discovering existing PyFunction objects, and then using gh-91049 to mark them as JIT’able. This could facilitate loading the JIT feature at a later time (e.g. as part of a module).\r\n\r\n[Edited] In general, there already exists a Python API for iterating over GC’able objects via [gc.get_objects()](https://docs.python.org/3/library/gc.html#gc.get_objects), however there is no good way of doing this from native extensions. While it is technically possible to import the `gc` module and extract the `gc_objects` function in C this is cumbersome, and more importantly might lead to unexpected behavior if Python code has replaced the `gc_objects` function.\r\n\r\n\u003c!-- gh-linked-prs --\u003e\r\n### Linked PRs\r\n* gh-102014\r\n* gh-115560\n\u003c!-- /gh-linked-prs --\u003e\r\n","author":{"url":"https://github.com/jbower-fb","@type":"Person","name":"jbower-fb"},"datePublished":"2023-02-18T00:45:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":12},"url":"https://github.com/102013/cpython/issues/102013"}