Add comment

encukou · encukou · commit 03bc32b33b3d · 2024-12-04T11:35:18.000+01:00
diff --git a/Lib/test/test_ctypes/test_struct_fields.py b/Lib/test/test_ctypes/test_struct_fields.py
@@ -77,13 +77,20 @@ def __init_subclass__(cls, **kwargs):
             class Subclass(BrokenStructure): ...
 
     def test_max_field_size_gh126937(self):
+        # Classes for big structs should be created successfully.
+        # (But they most likely can't be instantiated.)
+        # Here we test the exact limit: the number of *bits* must fit
+        # in Py_ssize_t.
+
         class X(self.cls):
             _fields_ = [('char', c_char),]
         max_field_size = sys.maxsize // 8
+
         class Y(self.cls):
             _fields_ = [('largeField', X * max_field_size)]
         class Z(self.cls):
             _fields_ = [('largeField', c_char * max_field_size)]
+
         with self.assertRaises(ValueError):
             class TooBig(self.cls):
                 _fields_ = [('largeField', X * (max_field_size + 1))]
