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, 17 insertions, 2 deletions

diff --git a/Python/pystate.c b/Python/pystate.c
index e214f50..4ac05d6 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -255,6 +255,9 @@ PyState_FindModule(struct PyModuleDef* module)
     Py_ssize_t index = module->m_base.m_index;
     PyInterpreterState *state = PyThreadState_GET()->interp;
     PyObject *res;
+    if (module->m_slots) {
+        return NULL;
+    }
     if (index == 0)
         return NULL;
     if (state->modules_by_index == NULL)
@@ -268,7 +271,13 @@ PyState_FindModule(struct PyModuleDef* module)
 int
 _PyState_AddModule(PyObject* module, struct PyModuleDef* def)
 {
-    PyInterpreterState *state = PyThreadState_GET()->interp;
+    PyInterpreterState *state;
+    if (def->m_slots) {
+        PyErr_SetString(PyExc_SystemError,
+                        "PyState_AddModule called on module with slots");
+        return -1;
+    }
+    state = PyThreadState_GET()->interp;
     if (!def)
         return -1;
     if (!state->modules_by_index) {
@@ -308,8 +317,14 @@ PyState_AddModule(PyObject* module, struct PyModuleDef* def)
 int
 PyState_RemoveModule(struct PyModuleDef* def)
 {
+    PyInterpreterState *state;
     Py_ssize_t index = def->m_base.m_index;
-    PyInterpreterState *state = PyThreadState_GET()->interp;
+    if (def->m_slots) {
+        PyErr_SetString(PyExc_SystemError,
+                        "PyState_RemoveModule called on module with slots");
+        return -1;
+    }
+    state = PyThreadState_GET()->interp;
     if (index == 0) {
         Py_FatalError("PyState_RemoveModule: Module index invalid.");
         return -1;