# finalizer.
def __del__(self):
- # 5. Create a weakref to `func` now. If we had created
- # it earlier, it would have been cleared by the
- # garbage collector before calling the finalizers.
+ # 5. Create a weakref to `func` now. In previous
+ # versions of Python, this would avoid having it
+ # cleared by the garbage collector before calling
+ # the finalizers. Now, weakrefs get cleared after
+ # calling finalizers.
self[1].ref = weakref.ref(self[0])
# 6. Drop the global reference to `latefin`. The only
# which will find `cyc` and `func` as garbage.
gc.collect()
- # 9. Previously, this would crash because `func_qualname`
- # had been NULL-ed out by func_clear().
+ # 9. Previously, this would crash because the weakref
+ # created in the finalizer revealed the function after
+ # `tp_clear` was called and `func_qualname`
+ # had been NULL-ed out by func_clear(). Now, we clear
+ # weakrefs to unreachable objects before calling `tp_clear`
+ # but after calling finalizers.
print(f"{func=}")
"""
- # We're mostly just checking that this doesn't crash.
rc, stdout, stderr = assert_python_ok("-c", code)
self.assertEqual(rc, 0)
- self.assertRegex(stdout, rb"""\A\s*func=<function at \S+>\s*\z""")
+ # The `func` global is None because the weakref was cleared.
+ self.assertRegex(stdout, rb"""\A\s*func=None""")
self.assertFalse(stderr)
@refcount_test
--- /dev/null
+While performing garbage collection, clear weakrefs to unreachable objects
+that are created during running of finalizers. If those weakrefs were are
+not cleared, they could reveal unreachable objects.
* no object in `unreachable` is weakly referenced anymore.
*/
static int
-handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
+handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old, bool allow_callbacks)
{
PyGC_Head *gc;
PyObject *op; /* generally FROM_GC(gc) */
PyGC_Head *next;
int num_freed = 0;
- gc_list_init(&wrcb_to_call);
+ if (allow_callbacks) {
+ gc_list_init(&wrcb_to_call);
+ }
/* Clear all weakrefs to the objects in unreachable. If such a weakref
* also has a callback, move it into `wrcb_to_call` if the callback
_PyObject_ASSERT((PyObject *)wr, wr->wr_object == op);
_PyWeakref_ClearRef(wr);
_PyObject_ASSERT((PyObject *)wr, wr->wr_object == Py_None);
+
+ if (!allow_callbacks) {
+ continue;
+ }
+
if (wr->wr_callback == NULL) {
/* no callback */
continue;
}
}
+ if (!allow_callbacks) {
+ return 0;
+ }
+
/* Invoke the callbacks we decided to honor. It's safe to invoke them
* because they can't reference unreachable objects.
*/
}
/* Clear weakrefs and invoke callbacks as necessary. */
- stats->collected += handle_weakrefs(&unreachable, to);
+ stats->collected += handle_weakrefs(&unreachable, to, true);
gc_list_validate_space(to, gcstate->visited_space);
validate_list(to, collecting_clear_unreachable_clear);
validate_list(&unreachable, collecting_set_unreachable_clear);
gc_list_init(&final_unreachable);
handle_resurrected_objects(&unreachable, &final_unreachable, to);
+ /* Clear weakrefs to objects in the unreachable set. No Python-level
+ * code must be allowed to access those unreachable objects. During
+ * delete_garbage(), finalizers outside the unreachable set might run
+ * and create new weakrefs. If those weakrefs were not cleared, they
+ * could reveal unreachable objects. Callbacks are not executed.
+ */
+ handle_weakrefs(&final_unreachable, NULL, false);
+
/* Call tp_clear on objects in the final_unreachable set. This will cause
* the reference cycles to be broken. It may also cause some objects
* in finalizers to be freed.
}
// Clear all weakrefs to unreachable objects. Weakrefs with callbacks are
-// enqueued in `wrcb_to_call`, but not invoked yet.
+// optionally enqueued in `wrcb_to_call`, but not invoked yet.
static void
-clear_weakrefs(struct collection_state *state)
+clear_weakrefs(struct collection_state *state, bool enqueue_callbacks)
{
PyObject *op;
WORKSTACK_FOR_EACH(&state->unreachable, op) {
_PyWeakref_ClearRef(wr);
_PyObject_ASSERT((PyObject *)wr, wr->wr_object == Py_None);
+ if (!enqueue_callbacks) {
+ continue;
+ }
+
// We do not invoke callbacks for weakrefs that are themselves
// unreachable. This is partly for historical reasons: weakrefs
// predate safe object finalization, and a weakref that is itself
interp->gc.long_lived_total = state->long_lived_total;
// Clear weakrefs and enqueue callbacks (but do not call them).
- clear_weakrefs(state);
+ clear_weakrefs(state, true);
_PyEval_StartTheWorld(interp);
// Deallocate any object from the refcount merge step
call_weakref_callbacks(state);
finalize_garbage(state);
- // Handle any objects that may have resurrected after the finalization.
_PyEval_StopTheWorld(interp);
+ // Handle any objects that may have resurrected after the finalization.
err = handle_resurrected_objects(state);
// Clear free lists in all threads
_PyGC_ClearAllFreeLists(interp);
+ if (err == 0) {
+ // Clear weakrefs to objects in the unreachable set. No Python-level
+ // code must be allowed to access those unreachable objects. During
+ // delete_garbage(), finalizers outside the unreachable set might
+ // run and create new weakrefs. If those weakrefs were not cleared,
+ // they could reveal unreachable objects.
+ clear_weakrefs(state, false);
+ }
_PyEval_StartTheWorld(interp);
if (err < 0) {
projects / thirdparty / Python / cpython.git / commitdiff
