PEP 489: Multi-phase extension module initialization

Known limitations of the current implementation:

- documentation changes are incomplete
- there's a reference leak I haven't tracked down yet

The leak is most visible by running:

  ./python -m test -R3:3 test_importlib

However, you can also see it by running:

  ./python -X showrefcount

Importing the array or _testmultiphase modules, and
then deleting them from both sys.modules and the local
namespace shows significant increases in the total
number of active references each cycle. By contrast,
with _testcapi (which continues to use single-phase
initialisation) the global refcounts stabilise after
a couple of cycles.

1 files changed, 567 insertions, 0 deletions

diff --git a/Modules/_testmultiphase.c b/Modules/_testmultiphase.c
new file mode 100644
index 0000000000..3e8e5d5c6c
--- /dev/null
+++ b/Modules/_testmultiphase.c
@@ -0,0 +1,567 @@
+
+/* Testing module for multi-phase initialization of extension modules (PEP 489)
+ */
+
+#include "Python.h"
+
+/* Example objects */
+typedef struct {
+    PyObject_HEAD
+    PyObject            *x_attr;        /* Attributes dictionary */
+} ExampleObject;
+
+/* Example methods */
+
+static void
+Example_dealloc(ExampleObject *self)
+{
+    Py_XDECREF(self->x_attr);
+    PyObject_Del(self);
+}
+
+static PyObject *
+Example_demo(ExampleObject *self, PyObject *args)
+{
+    PyObject *o = NULL;
+    if (!PyArg_ParseTuple(args, "|O:demo", &o))
+        return NULL;
+    if (o != NULL && PyUnicode_Check(o)) {
+        Py_INCREF(o);
+        return o;
+    }
+    Py_INCREF(Py_None);
+    return Py_None;
+}
+
+
+static PyMethodDef Example_methods[] = {
+    {"demo",            (PyCFunction)Example_demo,  METH_VARARGS,
+        PyDoc_STR("demo() -> None")},
+    {NULL,              NULL}           /* sentinel */
+};
+
+static PyObject *
+Example_getattro(ExampleObject *self, PyObject *name)
+{
+    if (self->x_attr != NULL) {
+        PyObject *v = PyDict_GetItem(self->x_attr, name);
+        if (v != NULL) {
+            Py_INCREF(v);
+            return v;
+        }
+    }
+    return PyObject_GenericGetAttr((PyObject *)self, name);
+}
+
+static int
+Example_setattr(ExampleObject *self, char *name, PyObject *v)
+{
+    if (self->x_attr == NULL) {
+        self->x_attr = PyDict_New();
+        if (self->x_attr == NULL)
+            return -1;
+    }
+    if (v == NULL) {
+        int rv = PyDict_DelItemString(self->x_attr, name);
+        if (rv < 0)
+            PyErr_SetString(PyExc_AttributeError,
+                "delete non-existing Example attribute");
+        return rv;
+    }
+    else
+        return PyDict_SetItemString(self->x_attr, name, v);
+}
+
+static PyType_Slot Example_Type_slots[] = {
+    {Py_tp_doc, "The Example type"},
+    {Py_tp_dealloc, Example_dealloc},
+    {Py_tp_getattro, Example_getattro},
+    {Py_tp_setattr, Example_setattr},
+    {Py_tp_methods, Example_methods},
+    {0, 0},
+};
+
+static PyType_Spec Example_Type_spec = {
+    "_testimportexec.Example",
+    sizeof(ExampleObject),
+    0,
+    Py_TPFLAGS_DEFAULT,
+    Example_Type_slots
+};
+
+/* Function of two integers returning integer */
+
+PyDoc_STRVAR(testexport_foo_doc,
+"foo(i,j)\n\
+\n\
+Return the sum of i and j.");
+
+static PyObject *
+testexport_foo(PyObject *self, PyObject *args)
+{
+    long i, j;
+    long res;
+    if (!PyArg_ParseTuple(args, "ll:foo", &i, &j))
+        return NULL;
+    res = i + j;
+    return PyLong_FromLong(res);
+}
+
+/* Test that PyState registration fails  */
+
+PyDoc_STRVAR(call_state_registration_func_doc,
+"register_state(0): call PyState_FindModule()\n\
+register_state(1): call PyState_AddModule()\n\
+register_state(2): call PyState_RemoveModule()");
+
+static PyObject *
+call_state_registration_func(PyObject *mod, PyObject *args)
+{
+    int i, ret;
+    PyModuleDef *def = PyModule_GetDef(mod);
+    if (def == NULL) {
+        return NULL;
+    }
+    if (!PyArg_ParseTuple(args, "i:call_state_registration_func", &i))
+        return NULL;
+    switch (i) {
+        case 0:
+            mod = PyState_FindModule(def);
+            if (mod == NULL) {
+                Py_RETURN_NONE;
+            }
+            return mod;
+        case 1:
+            ret = PyState_AddModule(mod, def);
+            if (ret != 0) {
+                return NULL;
+            }
+            break;
+        case 2:
+            ret = PyState_RemoveModule(def);
+            if (ret != 0) {
+                return NULL;
+            }
+            break;
+    }
+    Py_RETURN_NONE;
+}
+
+
+static PyType_Slot Str_Type_slots[] = {
+    {Py_tp_base, NULL}, /* filled out in module exec function */
+    {0, 0},
+};
+
+static PyType_Spec Str_Type_spec = {
+    "_testimportexec.Str",
+    0,
+    0,
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+    Str_Type_slots
+};
+
+static PyMethodDef testexport_methods[] = {
+    {"foo",             testexport_foo,         METH_VARARGS,
+        testexport_foo_doc},
+    {"call_state_registration_func",  call_state_registration_func,
+        METH_VARARGS, call_state_registration_func_doc},
+    {NULL,              NULL}           /* sentinel */
+};
+
+static int execfunc(PyObject *m)
+{
+    PyObject *temp = NULL;
+
+    /* Due to cross platform compiler issues the slots must be filled
+     * here. It's required for portability to Windows without requiring
+     * C++. */
+    Str_Type_slots[0].pfunc = &PyUnicode_Type;
+
+    /* Add a custom type */
+    temp = PyType_FromSpec(&Example_Type_spec);
+    if (temp == NULL)
+        goto fail;
+    if (PyModule_AddObject(m, "Example", temp) != 0)
+        goto fail;
+
+    /* Add an exception type */
+    temp = PyErr_NewException("_testimportexec.error", NULL, NULL);
+    if (temp == NULL)
+        goto fail;
+    if (PyModule_AddObject(m, "error", temp) != 0)
+        goto fail;
+
+    /* Add Str */
+    temp = PyType_FromSpec(&Str_Type_spec);
+    if (temp == NULL)
+        goto fail;
+    if (PyModule_AddObject(m, "Str", temp) != 0)
+        goto fail;
+
+    if (PyModule_AddIntConstant(m, "int_const", 1969) != 0)
+        goto fail;
+
+    if (PyModule_AddStringConstant(m, "str_const", "something different") != 0)
+        goto fail;
+
+    return 0;
+ fail:
+    return -1;
+}
+
+/* Helper for module definitions; there'll be a lot of them */
+#define TEST_MODULE_DEF(name, slots, methods) { \
+    PyModuleDef_HEAD_INIT,                      /* m_base */ \
+    name,                                       /* m_name */ \
+    PyDoc_STR("Test module " name),             /* m_doc */ \
+    0,                                          /* m_size */ \
+    methods,                                    /* m_methods */ \
+    slots,                                      /* m_slots */ \
+    NULL,                                       /* m_traverse */ \
+    NULL,                                       /* m_clear */ \
+    NULL,                                       /* m_free */ \
+}
+
+PyModuleDef_Slot main_slots[] = {
+    {Py_mod_exec, execfunc},
+    {0, NULL},
+};
+
+static PyModuleDef main_def = TEST_MODULE_DEF("main", main_slots, testexport_methods);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase(PyObject *spec)
+{
+    return PyModuleDef_Init(&main_def);
+}
+
+
+/**** Importing a non-module object ****/
+
+static PyModuleDef def_nonmodule;
+
+/* Create a SimpleNamespace(three=3) */
+static PyObject*
+createfunc_nonmodule(PyObject *spec, PyModuleDef *def)
+{
+    PyObject *dct, *ns, *three;
+
+    if (def != &def_nonmodule) {
+        PyErr_SetString(PyExc_SystemError, "def does not match");
+        return NULL;
+    }
+
+    dct = PyDict_New();
+    if (dct == NULL)
+        return NULL;
+
+    three = PyLong_FromLong(3);
+    if (three == NULL) {
+        Py_DECREF(dct);
+        return NULL;
+    }
+    PyDict_SetItemString(dct, "three", three);
+
+    ns = _PyNamespace_New(dct);
+    Py_DECREF(dct);
+    return ns;
+}
+
+static PyModuleDef_Slot slots_create_nonmodule[] = {
+    {Py_mod_create, createfunc_nonmodule},
+    {0, NULL},
+};
+
+static PyModuleDef def_nonmodule = TEST_MODULE_DEF(
+    "_testmultiphase_nonmodule", slots_create_nonmodule, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_nonmodule(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_nonmodule);
+}
+
+/**** Non-ASCII-named modules ****/
+
+static PyModuleDef def_nonascii_latin = { \
+    PyModuleDef_HEAD_INIT,                      /* m_base */
+    "_testmultiphase_nonascii_latin",           /* m_name */
+    PyDoc_STR("Module named in Czech"),         /* m_doc */
+    0,                                          /* m_size */
+    NULL,                                       /* m_methods */
+    NULL,                                       /* m_slots */
+    NULL,                                       /* m_traverse */
+    NULL,                                       /* m_clear */
+    NULL,                                       /* m_free */
+};
+
+PyMODINIT_FUNC
+PyInitU__testmultiphase_zkouka_naten_evc07gi8e(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_nonascii_latin);
+}
+
+static PyModuleDef def_nonascii_kana = { \
+    PyModuleDef_HEAD_INIT,                      /* m_base */
+    "_testmultiphase_nonascii_kana",            /* m_name */
+    PyDoc_STR("Module named in Japanese"),      /* m_doc */
+    0,                                          /* m_size */
+    NULL,                                       /* m_methods */
+    NULL,                                       /* m_slots */
+    NULL,                                       /* m_traverse */
+    NULL,                                       /* m_clear */
+    NULL,                                       /* m_free */
+};
+
+PyMODINIT_FUNC
+PyInitU_eckzbwbhc6jpgzcx415x(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_nonascii_kana);
+}
+
+/**** Testing NULL slots ****/
+
+static PyModuleDef null_slots_def = TEST_MODULE_DEF(
+    "_testmultiphase_null_slots", NULL, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_null_slots(PyObject *spec)
+{
+    return PyModuleDef_Init(&null_slots_def);
+}
+
+/**** Problematic modules ****/
+
+static PyModuleDef_Slot slots_bad_large[] = {
+    {_Py_mod_LAST_SLOT + 1, NULL},
+    {0, NULL},
+};
+
+static PyModuleDef def_bad_large = TEST_MODULE_DEF(
+    "_testmultiphase_bad_slot_large", slots_bad_large, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_bad_slot_large(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_bad_large);
+}
+
+static PyModuleDef_Slot slots_bad_negative[] = {
+    {-1, NULL},
+    {0, NULL},
+};
+
+static PyModuleDef def_bad_negative = TEST_MODULE_DEF(
+    "_testmultiphase_bad_slot_negative", slots_bad_negative, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_bad_slot_negative(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_bad_negative);
+}
+
+static PyModuleDef def_create_int_with_state = { \
+    PyModuleDef_HEAD_INIT,                      /* m_base */
+    "create_with_state",                        /* m_name */
+    PyDoc_STR("Not a PyModuleObject object, but requests per-module state"),
+    10,                                         /* m_size */
+    NULL,                                       /* m_methods */
+    slots_create_nonmodule,                     /* m_slots */
+    NULL,                                       /* m_traverse */
+    NULL,                                       /* m_clear */
+    NULL,                                       /* m_free */
+};
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_create_int_with_state(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_create_int_with_state);
+}
+
+
+static PyModuleDef def_negative_size = { \
+    PyModuleDef_HEAD_INIT,                      /* m_base */
+    "negative_size",                            /* m_name */
+    PyDoc_STR("PyModuleDef with negative m_size"),
+    -1,                                         /* m_size */
+    NULL,                                       /* m_methods */
+    slots_create_nonmodule,                     /* m_slots */
+    NULL,                                       /* m_traverse */
+    NULL,                                       /* m_clear */
+    NULL,                                       /* m_free */
+};
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_negative_size(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_negative_size);
+}
+
+
+static PyModuleDef uninitialized_def = TEST_MODULE_DEF("main", main_slots, testexport_methods);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_export_uninitialized(PyObject *spec)
+{
+    return (PyObject*) &uninitialized_def;
+}
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_export_null(PyObject *spec)
+{
+    return NULL;
+}
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_export_raise(PyObject *spec)
+{
+    PyErr_SetString(PyExc_SystemError, "bad export function");
+    return NULL;
+}
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_export_unreported_exception(PyObject *spec)
+{
+    PyErr_SetString(PyExc_SystemError, "bad export function");
+    return PyModuleDef_Init(&main_def);
+}
+
+static PyObject*
+createfunc_null(PyObject *spec, PyModuleDef *def)
+{
+    return NULL;
+}
+
+PyModuleDef_Slot slots_create_null[] = {
+    {Py_mod_create, createfunc_null},
+    {0, NULL},
+};
+
+static PyModuleDef def_create_null = TEST_MODULE_DEF(
+    "_testmultiphase_create_null", slots_create_null, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_create_null(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_create_null);
+}
+
+static PyObject*
+createfunc_raise(PyObject *spec, PyModuleDef *def)
+{
+    PyErr_SetString(PyExc_SystemError, "bad create function");
+    return NULL;
+}
+
+static PyModuleDef_Slot slots_create_raise[] = {
+    {Py_mod_create, createfunc_raise},
+    {0, NULL},
+};
+
+static PyModuleDef def_create_raise = TEST_MODULE_DEF(
+    "_testmultiphase_create_null", slots_create_raise, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_create_raise(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_create_raise);
+}
+
+static PyObject*
+createfunc_unreported_exception(PyObject *spec, PyModuleDef *def)
+{
+    PyErr_SetString(PyExc_SystemError, "bad create function");
+    return PyModule_New("foo");
+}
+
+static PyModuleDef_Slot slots_create_unreported_exception[] = {
+    {Py_mod_create, createfunc_unreported_exception},
+    {0, NULL},
+};
+
+static PyModuleDef def_create_unreported_exception = TEST_MODULE_DEF(
+    "_testmultiphase_create_unreported_exception", slots_create_unreported_exception, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_create_unreported_exception(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_create_unreported_exception);
+}
+
+static PyModuleDef_Slot slots_nonmodule_with_exec_slots[] = {
+    {Py_mod_create, createfunc_nonmodule},
+    {Py_mod_exec, execfunc},
+    {0, NULL},
+};
+
+static PyModuleDef def_nonmodule_with_exec_slots = TEST_MODULE_DEF(
+    "_testmultiphase_nonmodule_with_exec_slots", slots_nonmodule_with_exec_slots, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_nonmodule_with_exec_slots(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_nonmodule_with_exec_slots);
+}
+
+static int
+execfunc_err(PyObject *mod)
+{
+    return -1;
+}
+
+static PyModuleDef_Slot slots_exec_err[] = {
+    {Py_mod_exec, execfunc_err},
+    {0, NULL},
+};
+
+static PyModuleDef def_exec_err = TEST_MODULE_DEF(
+    "_testmultiphase_exec_err", slots_exec_err, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_exec_err(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_exec_err);
+}
+
+static int
+execfunc_raise(PyObject *spec)
+{
+    PyErr_SetString(PyExc_SystemError, "bad exec function");
+    return -1;
+}
+
+static PyModuleDef_Slot slots_exec_raise[] = {
+    {Py_mod_exec, execfunc_raise},
+    {0, NULL},
+};
+
+static PyModuleDef def_exec_raise = TEST_MODULE_DEF(
+    "_testmultiphase_exec_raise", slots_exec_raise, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_exec_raise(PyObject *mod)
+{
+    return PyModuleDef_Init(&def_exec_raise);
+}
+
+static int
+execfunc_unreported_exception(PyObject *mod)
+{
+    PyErr_SetString(PyExc_SystemError, "bad exec function");
+    return 0;
+}
+
+static PyModuleDef_Slot slots_exec_unreported_exception[] = {
+    {Py_mod_exec, execfunc_unreported_exception},
+    {0, NULL},
+};
+
+static PyModuleDef def_exec_unreported_exception = TEST_MODULE_DEF(
+    "_testmultiphase_exec_unreported_exception", slots_exec_unreported_exception, NULL);
+
+PyMODINIT_FUNC
+PyInit__testmultiphase_exec_unreported_exception(PyObject *spec)
+{
+    return PyModuleDef_Init(&def_exec_unreported_exception);
+}