Add tp_alloc test and fix the inheritance issues it exposed

src/capi/typeobject.cpp

@@ -1599,7 +1599,6 @@ extern "C" int PyType_Ready(PyTypeObject* cls) noexcept {
     RELEASE_ASSERT(cls->tp_iternext == NULL, "");
     RELEASE_ASSERT(cls->tp_descr_get == NULL, "");
     RELEASE_ASSERT(cls->tp_descr_set == NULL, "");
-    RELEASE_ASSERT(cls->tp_alloc == NULL || cls->tp_alloc == PyType_GenericAlloc, "");
     RELEASE_ASSERT(cls->tp_free == NULL || cls->tp_free == PyObject_Del, "");
     RELEASE_ASSERT(cls->tp_is_gc == NULL, "");
     RELEASE_ASSERT(cls->tp_mro == NULL, "");
@@ -1637,10 +1636,6 @@ extern "C" int PyType_Ready(PyTypeObject* cls) noexcept {
     if (!cls->tp_new && base != object_cls)
         cls->tp_new = base->tp_new;
 
-    if (!cls->tp_alloc) {
-        cls->tp_alloc = reinterpret_cast<decltype(cls->tp_alloc)>(PyType_GenericAlloc);
-    }
-
     try {
         add_operators(cls);
     } catch (Box* b) {
@@ -1662,6 +1657,9 @@ extern "C" int PyType_Ready(PyTypeObject* cls) noexcept {
 
     PystonType_Ready(cls);
 
+    if (cls->tp_alloc == &PystonType_GenericAlloc)
+        cls->tp_alloc = &PyType_GenericAlloc;
+
     cls->gc_visit = &conservativeGCHandler;
     cls->is_user_defined = true;
 

src/runtime/objmodel.cpp

@@ -355,6 +355,8 @@ BoxedClass::BoxedClass(BoxedClass* base, gcvisit_func gc_visit, int attrs_offset
     tp_flags |= Py_TPFLAGS_HEAPTYPE;
     tp_flags |= Py_TPFLAGS_CHECKTYPES;
     tp_flags |= Py_TPFLAGS_BASETYPE;
+    tp_flags |= Py_TPFLAGS_HAVE_CLASS;
+    tp_flags |= Py_TPFLAGS_HAVE_GC;
 
     tp_base = base;
 
@@ -3353,8 +3355,10 @@ Box* typeNew(Box* _cls, Box* arg1, Box* arg2, Box** _args) {
     PystonType_Ready(made);
     fixup_slot_dispatchers(made);
 
-    made->tp_alloc = base->tp_alloc;
-    assert(made->tp_alloc);
+    if (base->tp_alloc == &PystonType_GenericAlloc)
+        made->tp_alloc = PystonType_GenericAlloc;
+    else
+        made->tp_alloc = PyType_GenericAlloc;
 
     return made;
 }

test/test_extension/slots_test.c

@@ -37,6 +37,13 @@ slots_tester_init(PyObject *self, PyObject *args, PyObject *kwds)
     return 0;
 }
 
+static PyObject*
+slots_tester_alloc(PyTypeObject* type, Py_ssize_t nitems) {
+    printf("slots_tester_seq.tp_alloc, %s %ld\n", type->tp_name, nitems);
+
+    return PyType_GenericAlloc(type, nitems);
+}
+
 static long slots_tester_seq_hash(slots_tester_object* obj) {
     printf("slots_tester_seq.__hash__\n");
     return obj->n ^ 1;
@@ -139,7 +146,7 @@ static PyTypeObject slots_tester_seq = {
     0,                                  /* tp_descr_set */
     0,                                  /* tp_dictoffset */
     slots_tester_init,                  /* tp_init */
-    0,                                  /* tp_alloc */
+    (allocfunc)slots_tester_alloc,                 /* tp_alloc */
     slots_tester_new,                   /* tp_new */
     0,                                  /* tp_free */
 };