gh-140025: Fix queue.SimpleQueue.__sizeof__()

Lib/test/test_queue.py

@@ -9,6 +9,8 @@
 from test.support import gc_collect, bigmemtest
 from test.support import import_helper
 from test.support import threading_helper
+import sys
+from test import support
 
 # queue module depends on threading primitives
 threading_helper.requires_working_threading(module=True)
@@ -1031,6 +1033,16 @@ 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 = sys.getsizeof(q)
+        for _ in range(1000):
+            q.put(object())
+        after = sys.getsizeof(q)
+        self.assertGreater(after, before)
+        ptr = support.calcobjsize("P") - support.calcobjsize("")
+        self.assertEqual((after - before) % ptr, 0)
+
     def test_reentrancy(self):
         # bpo-14976: put() may be called reentrantly in an asynchronous
         # callback.

Misc/NEWS.d/next/Library/2026-01-02-09-32-43.gh-issue-140025.zOX58_.rst

@@ -0,0 +1 @@
+Fix ``queue.SimpleQueue.__sizeof__()`` computation.

Modules/_queuemodule.c

@@ -239,6 +239,21 @@ simplequeue_traverse(PyObject *op, visitproc visit, void *arg)
     return 0;
 }
 
+/*[clinic input]
+@critical_section
+_queue.SimpleQueue.__sizeof__ -> Py_ssize_t
+
+Returns size in memory, in bytes.
+[clinic start generated code]*/
+
+static Py_ssize_t
+_queue_SimpleQueue___sizeof___impl(simplequeueobject *self)
+/*[clinic end generated code: output=58ce4e3bbc078fd4 input=a3a7f05c9616598f]*/
+{
+    Py_ssize_t res = sizeof(simplequeueobject);
+    res += self->buf.items_cap * sizeof(PyObject *);
+    return res;
+}
 /*[clinic input]
 @classmethod
 _queue.SimpleQueue.__new__ as simplequeue_new
@@ -534,6 +549,7 @@ static PyMethodDef simplequeue_methods[] = {
     _QUEUE_SIMPLEQUEUE_PUT_METHODDEF
     _QUEUE_SIMPLEQUEUE_PUT_NOWAIT_METHODDEF
     _QUEUE_SIMPLEQUEUE_QSIZE_METHODDEF
+    _QUEUE_SIMPLEQUEUE___SIZEOF___METHODDEF
     {"__class_getitem__",    Py_GenericAlias,
     METH_O|METH_CLASS,       PyDoc_STR("See PEP 585")},
     {NULL,           NULL}              /* sentinel */