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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add a mechanism for single-phase init modules to declare free-threading compatibility","articleBody":"# Feature or enhancement\r\n\r\n### Proposal:\r\n\r\ngh-116322 only works for modules using multi-phase init; we need an alternative mechanism for for single-phase init modules since they can't provide `m_slots`.\r\n\r\nWe originally considered indicating compatibility in the symbol table of the `.so` containing the module, either by the presence of a magic symbol, or by providing an alternate init function with a `PyInitT_` prefix. As pointed out by @Yhg1s in Discord, that solution doesn't work with modules added to inittab.\r\n\r\nThe current proposal is:\r\n- Before calling any module init function, enable the GIL if it is disabled (this will most likely be done as part of gh-116882).\r\n- In free-threaded builds, add a `void *md_gil` member to `PyModuleObject`. It defaults to `Py_MOD_GIL_USED` (the same constant from gh-116322).\r\n- Introduce a new public C API function `PyModule_SetGIL(PyObject *mod, void *gil)`. If a single-phase init module can run without the GIL, it will call `PyModule_SetGIL(mod, Py_MOD_GIL_NOT_USED)` in its init function. This function will be a no-op in normal builds, and will set `md_gil` to its argument in free-threaded builds.\r\n- After the init function returns, if the module's `md_gil` member is set to `Py_MOD_GIL_NOT_USED` and the GIL was disabled before calling the init function, disable the GIL.","author":{"url":"https://github.com/swtaarrs","@type":"Person","name":"swtaarrs"},"datePublished":"2024-04-03T22:29:07.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/117526/cpython/issues/117526"}