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bpo-46891: Fix creating a new instance of a module subclass with slots #31643

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Merged
markshannon merged 2 commits into from
Mar 3, 2022
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bpo-46891: Fix creating a new instance of a module subclass with slots #31643

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Make sure slots are NULLed when creating a subclass of type.ModuleType.
markshannon Mar 2, 2022
8a7e32a
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markshannon Mar 2, 2022
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19 changes: 19 additions & 0 deletions Lib/test/test_module.py
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Original file line number Diff line number Diff line change
Expand Up @@ -346,6 +346,25 @@ def test_repeated_attribute_pops(self):

# frozen and namespace module reprs are tested in importlib.

def test_subclass_with_slots(self):
# In 3.11alpha this crashed, as the slots weren't NULLed.

class ModuleWithSlots(ModuleType):
__slots__ = ("a", "b")

def __init__(self, name):
super().__init__(name)

@vstinner vstinner Mar 2, 2022

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What's the purpose of this method? Maybe assign a and/or b attribute if you want to keep it? Or remove it?

@ronaldoussoren ronaldoussoren Mar 2, 2022

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The important bit is having __slots__ in the class definition, I just checked and leaving out the __init__ method still reproduces the crash that this PR fixes.

@vstinner vstinner Mar 2, 2022

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Well, I approved the PR. @markshannon can decide to keep or remove the method, it doesn't really matter ;-)


m = ModuleWithSlots("name")
with self.assertRaises(AttributeError):
m.a
with self.assertRaises(AttributeError):
m.b
m.a, m.b = 1, 2
self.assertEqual(m.a, 1)
self.assertEqual(m.b, 2)



if __name__ == '__main__':
unittest.main()
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-03-02-15-04-08.bpo-46891.aIAgTD.rst
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@@ -0,0 +1,3 @@
Fix bug introduced during 3.11alpha where subclasses of ``types.ModuleType``
with ``__slots__`` were not initialized correctly, resulting in an
interpreter crash.
3 changes: 2 additions & 1 deletion Objects/moduleobject.c
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Expand Up @@ -4,6 +4,7 @@
#include "Python.h"
#include "pycore_call.h" // _PyObject_CallNoArgs()
#include "pycore_interp.h" // PyInterpreterState.importlib
#include "pycore_object.h" // _PyType_AllocNoTrack
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_moduleobject.h" // _PyModule_GetDef()
#include "structmember.h" // PyMemberDef
Expand Down Expand Up @@ -80,7 +81,7 @@ static PyModuleObject *
new_module_notrack(PyTypeObject *mt)
{
PyModuleObject *m;
m = PyObject_GC_New(PyModuleObject, mt);
m = (PyModuleObject *)_PyType_AllocNoTrack(mt, 0);
if (m == NULL)
return NULL;
m->md_def = NULL;
Expand Down