avoid risk of stale pointers by looking up Cython types module on each request...

avoid risk of stale pointers by looking up Cython types module on each request (shouldn't hurt much to do it a couple of times during module initialisation)

Cython/Utility/CommonTypes.c

@@ -5,13 +5,13 @@ static PyTypeObject* __Pyx_FetchCommonType(PyTypeObject* type);
 /////////////// FetchCommonType ///////////////
 
 static PyTypeObject* __Pyx_FetchCommonType(PyTypeObject* type) {
-    static PyObject* fake_module = NULL;
+    PyObject* fake_module;
     PyTypeObject* cached_type = NULL;
     const char* cython_module = "_cython_" CYTHON_ABI;
-    if (!fake_module) {
+
     fake_module = PyImport_AddModule(cython_module);
-        if (!fake_module) goto bad;
-    }
+    if (!fake_module) return NULL;
+    Py_INCREF(fake_module);
 
     cached_type = (PyTypeObject*) PyObject_GetAttrString(fake_module, type->tp_name);
     if (!cached_type) {
@@ -25,6 +25,7 @@ static PyTypeObject* __Pyx_FetchCommonType(PyTypeObject* type) {
     }
 
 bad:
+    Py_DECREF(fake_module);
     // NOTE: always returns owned reference, or NULL on error
     return cached_type;
 }