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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: macOS backend lacks several autorelease pools","articleBody":"### Bug summary\n\nI'm investigating #31106.\n\nAt the time `show(PyObject* self)` is called, the window in question has a `-retainCount` of 600+. This is due to AppKit and other macOS frameworks calling `[[theWindow retain] autorelease]` across several internal methods.\n\nThe window is retained and added to the autorelease pool at the top of the stack, which is either the one set up in `wait_for_stdin()` or in `[NSApp run]`. In any case, the pool has never been drained by the time `show()` is called. Even after the user closes the window, the pool has still not been drained.\n\nGenerally, if you are calling from non-Objective-C code to Objective-C code, you need to set up an autorelease pool before crossing the boundary and release it after returning. Using an `@autoreleasepool` block makes this easy; however, it involves touching a lot of C functions inside of `_macosx.m`.\n\nI'm not experienced with Python extension modules. Is there a way to have Python automatically call a function before and after calling the C function assigned to each PyMethodDef?\n\n### Code for reproduction\n\n```Python\nimport matplotlib.pyplot as plt\n\nfor i in range(0, 4):\n    plt.subplots()\n\nplt.show()\n```\n\n### Actual outcome\n\nEach `NSWindow` still has a retain count of 600+ after closing.\n\n### Expected outcome\n\nEach `NSWindow` hits a retain count of 0 on close and `-dealloc` is called.\n\n### Additional information\n\n_No response_\n\n### Operating system\n\n_No response_\n\n### Matplotlib Version\n\n0.2.0.dev54528+unknown.gf4cf12592.d20260526\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\n_No response_\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\nNone","author":{"url":"https://github.com/iccir","@type":"Person","name":"iccir"},"datePublished":"2026-05-26T18:40:20.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/31751/matplotlib/issues/31751"}