gh-116099: Fix refcounting bug in `_queueobj_shared()` (gh-116164)

This code decrefs `qidobj` twice in some paths. Since `qidobj` isn't used after
the first `Py_DECREF()`, remove the others, and replace the `Py_DECREF()` with
`Py_CLEAR()` to make it clear that the variable is dead.

With this fix, `python -mtest test_interpreters -R 3:3 -mtest_queues` no longer
fails with `_Py_NegativeRefcount: Assertion failed: object has negative ref
count`.

diff --git a/Modules/_xxinterpqueuesmodule.c b/Modules/_xxinterpqueuesmodule.c
index 715bb766cac624e7c2bace96edd11867f20384ae..21ba817785cdfe0e4f0517b7f66f707bb8e50af0 100644 (file)
--- a/Modules/_xxinterpqueuesmodule.c
+++ b/Modules/_xxinterpqueuesmodule.c
@@ -1189,7 +1189,7 @@ _queueobj_shared(PyThreadState *tstate, PyObject *queueobj,
         .label = "queue ID",
     };
     int res = idarg_int64_converter(qidobj, &converted);
-    Py_DECREF(qidobj);
+    Py_CLEAR(qidobj);
     if (!res) {
         assert(PyErr_Occurred());
         return -1;
@@ -1197,12 +1197,10 @@ _queueobj_shared(PyThreadState *tstate, PyObject *queueobj,
 
     void *raw = _queueid_xid_new(converted.id);
     if (raw == NULL) {
-        Py_DECREF(qidobj);
         return -1;
     }
     _PyCrossInterpreterData_Init(data, tstate->interp, raw, NULL,
                                  _queueobj_from_xid);
-    Py_DECREF(qidobj);
     _PyCrossInterpreterData_SET_FREE(data, _queueid_xid_free);
     return 0;
 }