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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Macro Py_CLEAR references argument two times.","articleBody":"# Bug report\r\n\r\nThe macro `Py_CLEAR(op)` references the argument `op` two times. If the macro is called with an expression it will be evaluated two times, for example `Py_CLEAR(p++)`.\r\n\r\n# Your environment\r\n\r\nx86_64\r\n\r\n- CPython versions tested on:\r\nPython 3.7m\r\n- Operating system and architecture:\r\nDebian Stable\r\n\r\nI suggest a fix similar to this (old version commented out with #if 0):\r\n\r\n```\r\n#if 0\r\n#define Py_CLEAR(op)                            \\\r\n    do {                                        \\\r\n        PyObject *_py_tmp = (PyObject *)(op);   \\\r\n        if (_py_tmp != NULL) {                  \\\r\n            (op) = NULL;                        \\\r\n            Py_DECREF(_py_tmp);                 \\\r\n        }                                       \\\r\n    } while (0)\r\n#else\r\n#define Py_CLEAR(op)                                         \\\r\n    do {                                                     \\\r\n        PyObject **_py_tmp = (PyObject **)\u0026(op);             \\\r\n        if (*_py_tmp != NULL) {                              \\\r\n            PyObject *_py_tmp2 = *_py_tmp;                   \\\r\n            (*_py_tmp) = NULL;                               \\\r\n            Py_DECREF(_py_tmp2);                             \\\r\n        }                                                    \\\r\n    } while (0)\r\n#endif\r\n```\r\n\r\nI am not sure if this has happened anywhere, but I see a possible problem here. I think the compiler will optimize out the additional temporary variable in most cases.\n\n\u003c!-- gh-pr-number: gh-99100 --\u003e\n* PR: gh-99100\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99288 --\u003e\n* PR: gh-99288\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99292 --\u003e\n* PR: gh-99292\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99573 --\u003e\n* PR: gh-99573\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99737 --\u003e\n* PR: gh-99737\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99739 --\u003e\n* PR: gh-99739\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-99781 --\u003e\n* PR: gh-99781\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-100070 --\u003e\n* PR: gh-100070\n\u003c!-- /gh-pr-number --\u003e\n\n\n\u003c!-- gh-pr-number: gh-100121 --\u003e\n* PR: gh-100121\n\u003c!-- /gh-pr-number --\u003e\n","author":{"url":"https://github.com/hochl","@type":"Person","name":"hochl"},"datePublished":"2022-10-26T14:59:18.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":36},"url":"https://github.com/98724/cpython/issues/98724"}