Keep traceback alive for WITH_EXCEPT_START

Author: DinoV

Python/bytecodes.c

@@ -3297,20 +3297,18 @@ dummy_func(
 
             assert(val_o && PyExceptionInstance_Check(val_o));
             exc = PyExceptionInstance_Class(val_o);
-            tb = PyException_GetTraceback(val_o);
+            PyObject *original_tb = tb = PyException_GetTraceback(val_o);
             if (tb == NULL) {
                 tb = Py_None;
             }
-            else {
-                Py_DECREF(tb);
-            }
             assert(PyStackRef_LongCheck(lasti));
             (void)lasti; // Shut up compiler warning if asserts are off
             PyObject *stack[5] = {NULL, PyStackRef_AsPyObjectBorrow(exit_self), exc, val_o, tb};
             int has_self = !PyStackRef_IsNull(exit_self);
             PyObject *res_o = PyObject_Vectorcall(exit_func_o, stack + 2 - has_self,
                     (3 + has_self) | PY_VECTORCALL_ARGUMENTS_OFFSET, NULL);
             ERROR_IF(res_o == NULL, error);
+            Py_XDECREF(original_tb);
             res = PyStackRef_FromPyObjectSteal(res_o);
         }