New submission from Serhiy Storchaka: First, the documentation says that syntax for 'O!' conversion is object(type='name_of_Python_type'), but actually the type argument should be the name of C structure which represents Python type. I.e. object(type='list') is rejected, and object(type='PyList_Type') is accepted. Second, from this declaration /*[clinic] module spam spam.ham items: object(type='PyList_Type') / [clinic]*/ Argument Clinic generates following parsing code: if (!PyArg_ParseTuple(args, "O!:ham", PyList_Type, &items)) goto exit; It is wrong, should be &PyList_Type. ---------- assignee: docs@python components: Build, Documentation messages: 207430 nosy: docs@python, larry, serhiy.storchaka priority: release blocker severity: normal status: open title: Argument Clinic: broken support for 'O!' type: crash versions: Python 3.4 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue20141> _______________________________________