Implement trashcan behavior

src/capi/object.cpp

@@ -1154,10 +1154,33 @@ PyObject* _PyTrash_delete_later = NULL;
 }
 
 extern "C" void _PyTrash_thread_deposit_object(PyObject* op) noexcept {
-    Py_FatalError("unimplemented");
+    PyThreadState* tstate = PyThreadState_GET();
+    assert(PyObject_IS_GC(op));
+    assert(_Py_AS_GC(op)->gc.gc_refs == _PyGC_REFS_UNTRACKED);
+    assert(op->ob_refcnt == 0);
+    _Py_AS_GC(op)->gc.gc_prev = (PyGC_Head*)tstate->trash_delete_later;
+    tstate->trash_delete_later = op;
 }
+
 extern "C" void _PyTrash_thread_destroy_chain() noexcept {
-    Py_FatalError("unimplemented");
+    PyThreadState* tstate = PyThreadState_GET();
+    while (tstate->trash_delete_later) {
+        PyObject* op = tstate->trash_delete_later;
+        destructor dealloc = Py_TYPE(op)->tp_dealloc;
+
+        tstate->trash_delete_later = (PyObject*)_Py_AS_GC(op)->gc.gc_prev;
+
+        /* Call the deallocator directly.  This used to try to
+         * fool Py_DECREF into calling it indirectly, but
+         * Py_DECREF was already called on this object, and in
+         * assorted non-release builds calling Py_DECREF again ends
+         * up distorting allocation statistics.
+         */
+        assert(op->ob_refcnt == 0);
+        ++tstate->trash_delete_nesting;
+        (*dealloc)(op);
+        --tstate->trash_delete_nesting;
+    }
 }
 
 #ifdef Py_TRACE_REFS

test/tests/trashcan_test.py

+t = ()
+for i in xrange(10000):
+    t = (t,)