GH-117195: Avoid assertion error in object.__sizeof__ (GH-117220)

markshannon · web-flow · commit 406ffb5293a8 · 2024-05-23T11:06:10.000+01:00
diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py
@@ -1639,6 +1639,8 @@ class MyInt(int):
                     MyInt.__basicsize__ + MyInt.__itemsize__ * ndigits
                 )
 
+        # GH-117195 -- This shouldn't crash
+        object.__sizeof__(1)
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-03-25-15-07-01.gh-issue-117195.OWakgD.rst b/Misc/NEWS.d/next/Core and Builtins/2024-03-25-15-07-01.gh-issue-117195.OWakgD.rst
@@ -0,0 +1,2 @@
+Avoid assertion failure for debug builds when calling
+``object.__sizeof__(1)``
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
@@ -7144,8 +7144,11 @@ object___sizeof___impl(PyObject *self)
 
     res = 0;
     isize = Py_TYPE(self)->tp_itemsize;
-    if (isize > 0)
-        res = Py_SIZE(self) * isize;
+    if (isize > 0) {
+        /* This assumes that ob_size is valid if tp_itemsize is not 0,
+         which isn't true for PyLongObject. */
+        res = _PyVarObject_CAST(self)->ob_size * isize;
+    }
     res += Py_TYPE(self)->tp_basicsize;
 
     return PyLong_FromSsize_t(res);

Original file line number	Diff line number	Diff line change
`@@ -1639,6 +1639,8 @@ class MyInt(int):`
`1639`	`1639`	`MyInt.__basicsize__ + MyInt.__itemsize__ * ndigits`
`1640`	`1640`	`)`
`1641`	`1641`
	`1642`	`+ # GH-117195 -- This shouldn't crash`
	`1643`	`+ object.__sizeof__(1)`
`1642`	`1644`
`1643`	`1645`	`if __name__ == "__main__":`
`1644`	`1646`	`unittest.main()`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Avoid assertion failure for debug builds when calling`
	`2`	+``object.__sizeof__(1)``