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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"_PyEval_SetTrace() fails with RuntimeError: Cannot install a trace function while another trace function is being installed","articleBody":"The test_concurrency() of test_import fails randomly on sys.settrace(). Example:\r\n\r\n```\r\n$ ./python -m test test_import -m test_concurrency -v -j30 -F --fail-env-changed \r\n(...)\r\n0:00:13 load avg: 12.46 [ 97/1] test_import failed (env changed)\r\ntest_concurrency (test.test_import.ImportTests) ... ok\r\n\r\n----------------------------------------------------------------------\r\nRan 1 test in 0.487s\r\n\r\nOK\r\nWarning -- Uncaught thread exception: RuntimeError\r\nException in thread Thread-13 (run):\r\nTraceback (most recent call last):\r\n  File \"/home/vstinner/python/3.10/Lib/threading.py\", line 1016, in _bootstrap_inner\r\n    self.run()\r\n  File \"/home/vstinner/python/3.10/Lib/threading.py\", line 953, in run\r\n    self._target(*self._args, **self._kwargs)\r\n  File \"/home/vstinner/python/3.10/Lib/test/test_import/__init__.py\", line 457, in run\r\n    sys.settrace(None)\r\nRuntimeError: Cannot install a trace function while another trace function is being installed\r\n(...)\r\n```\r\n\r\nThe problem is that the _PyEval_SetTrace() function fails with RuntimeError(\"Cannot install a trace function while another trace function is being installed\") on ``Py_XDECREF(traceobj);`` indirectly calls ``sys.settrace()``.\r\n\r\nIMO ``Py_XDECREF(traceobj);`` should be called *after* ``reentrant = 0;``, at the end of the function.","author":{"url":"https://github.com/vstinner","@type":"Person","name":"vstinner"},"datePublished":"2022-10-14T10:19:05.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/98257/cpython/issues/98257"}