implement __sizeof__ for SimpleQueue to account for ring-buffer storage

Author: Aniketsy

Lib/test/test_queue.py

@@ -9,6 +9,7 @@
 from test.support import gc_collect, bigmemtest
 from test.support import import_helper
 from test.support import threading_helper
+import ctypes
 
 # queue module depends on threading primitives
 threading_helper.requires_working_threading(module=True)
@@ -1031,6 +1032,16 @@ def test_is_default(self):
         self.assertIs(self.type2test, self.queue.SimpleQueue)
         self.assertIs(self.type2test, self.queue.SimpleQueue)
 
+    def test_simplequeue_sizeof_reflects_buffer_growth(self):
+        q = self.type2test()
+        before = q.__sizeof__()
+        for _ in range(1000):
+            q.put(object())
+        after = q.__sizeof__()
+        self.assertGreater(after, before)
+        ptr = ctypes.sizeof(ctypes.c_void_p)
+        self.assertEqual((after - before) % ptr, 0)
+
     def test_reentrancy(self):
         # bpo-14976: put() may be called reentrantly in an asynchronous
         # callback.

Modules/_queuemodule.c

@@ -238,6 +238,18 @@ simplequeue_traverse(PyObject *op, visitproc visit, void *arg)
     Py_VISIT(Py_TYPE(self));
     return 0;
 }
+static PyObject *
+simplequeue_sizeof(PyObject *op, PyObject *Py_UNUSED(ignored))
+{
+    simplequeueobject *self = simplequeueobject_CAST(op);
+    Py_ssize_t size = Py_TYPE(self)->tp_basicsize;
+
+    if (self->buf.items != NULL) {
+        size += (Py_ssize_t)self->buf.items_cap * (Py_ssize_t)sizeof(PyObject *);
+    }
+
+    return PyLong_FromSsize_t(size);
+}
 
 /*[clinic input]
 @classmethod
@@ -534,6 +546,7 @@ static PyMethodDef simplequeue_methods[] = {
     _QUEUE_SIMPLEQUEUE_PUT_METHODDEF
     _QUEUE_SIMPLEQUEUE_PUT_NOWAIT_METHODDEF
     _QUEUE_SIMPLEQUEUE_QSIZE_METHODDEF
+    {"__sizeof__", (PyCFunction)simplequeue_sizeof, METH_NOARGS, NULL},
     {"__class_getitem__",    Py_GenericAlias,
     METH_O|METH_CLASS,       PyDoc_STR("See PEP 585")},
     {NULL,           NULL}              /* sentinel */