[issue46891] Crash in ModuleType subclass with __slots__

[Mark Shannon]

Change by Mark Shannon :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue46891] Crash in ModuleType subclass with __slots__

[Mark Shannon]

Mark Shannon  added the comment:


New changeset 751c9ed801ad1189272ca10f0749bfc9d49b5038 by Mark Shannon in 
branch 'main':
bpo-46891: Fix creating a new instance of a module subclass with slots 
(GH-31643)
https://github.com/python/cpython/commit/751c9ed801ad1189272ca10f0749bfc9d49b5038


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[issue46891] Crash in ModuleType subclass with __slots__

[Ronald Oussoren]

Ronald Oussoren  added the comment:

I don't feel qualified to review the PR, but can confirm that this PR fixes 
this issue as well as the crash in PyObjC that I extracted my reproducer from.

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[issue46891] Crash in ModuleType subclass with __slots__

[Mark Shannon]

Change by Mark Shannon :


--
keywords: +patch
pull_requests: +29763
stage: needs patch -> patch review
pull_request: https://github.com/python/cpython/pull/31643

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[issue46891] Crash in ModuleType subclass with __slots__

[Mark Shannon]

Mark Shannon  added the comment:

Dennis, thanks for bisecting this.

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[issue46891] Crash in ModuleType subclass with __slots__

[Mark Shannon]

Change by Mark Shannon :


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assignee:  -> Mark.Shannon

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[issue46891] Crash in ModuleType subclass with __slots__

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

Marking this as release blocker.

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priority: normal -> release blocker

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[issue46891] Crash in ModuleType subclass with __slots__

[Ronald Oussoren]

Ronald Oussoren  added the comment:

@Pablo: this is a possible release blocker, hard crash for code that works in 
earlier releases. 

That said, I have a workaround on my end and IMHO a fix could wait for the next 
alpha.

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nosy: +pablogsal

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[issue46891] Crash in ModuleType subclass with __slots__

[Dennis Sweeney]

Change by Dennis Sweeney :


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nosy: +Mark.Shannon

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[issue46891] Crash in ModuleType subclass with __slots__

[Dennis Sweeney]

Dennis Sweeney  added the comment:

Bisected to here:

c3f52b4d707a78eb342372a2be00f3eb846a05b9 is the first bad commit
commit c3f52b4d707a78eb342372a2be00f3eb846a05b9
Author: Mark Shannon 
Date:   Wed Jun 23 10:00:43 2021 +0100

bpo-44486: Make sure that modules always have a dictionary. (GH-26847)

* Make sure that modules always have a dictionary.

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nosy: +Dennis Sweeney

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[issue46891] Crash in ModuleType subclass with __slots__

[Ronald Oussoren]

Ronald Oussoren  added the comment:

The debug build seems to indicate that slot memory is not initiated properly, a 
stack trace (note the argument to visit_validate at frame #7):


  * frame #0: 0x00019b60d9b8 libsystem_kernel.dylib`__pthread_kill + 8
frame #1: 0x00019b640eb0 libsystem_pthread.dylib`pthread_kill + 288
frame #2: 0x00019b57e314 libsystem_c.dylib`abort + 164
frame #3: 0x00010030c4f4 python.exe`fatal_error_exit(status=-1) at 
pylifecycle.c:2624:9
frame #4: 0x00010030c3cc python.exe`fatal_error(fd=2, header=1, 
prefix="_PyObject_AssertFailed", msg="_PyObject_AssertFailed", status=-1) at 
pylifecycle.c:2805:5
frame #5: 0x00010030be20 
python.exe`_Py_FatalErrorFunc(func="_PyObject_AssertFailed", 
msg="_PyObject_AssertFailed") at pylifecycle.c:2821:5
frame #6: 0x000100169fe0 
python.exe`_PyObject_AssertFailed(obj=0x000100d63690, 
expr=0x, msg="PyObject_GC_Track() object is not valid", 
file="../Modules/gcmodule.c", line=2187, function="visit_validate") at 
object.c:2293:5
frame #7: 0x000100351184 
python.exe`visit_validate(op=0xcdcdcdcdcdcdcdcd, parent_raw=0x000100d63690) 
at gcmodule.c:2186:9
frame #8: 0x00010019845c 
python.exe`traverse_slots(type=0x000101813230, self=0x000100d63690, 
visit=(python.exe`visit_validate at gcmodule.c:2183), arg=0x000100d63690) 
at typeobject.c:1207:27
frame #9: 0x000100197fe8 
python.exe`subtype_traverse(self=0x000100d63690, 
visit=(python.exe`visit_validate at gcmodule.c:2183), arg=0x000100d63690) 
at typeobject.c:1228:23
frame #10: 0x000100350fdc 
python.exe`PyObject_GC_Track(op_raw=0x000100d63690) at gcmodule.c:2212:11

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[issue46891] Crash in ModuleType subclass with __slots__

[Ronald Oussoren]

Ronald Oussoren  added the comment:

The crash itself happens during garbage collection:

% python3.11 -Xdev t.py 
  
(master)pyobjc-8
Fatal Python error: Segmentation fault

Current thread 0x000104ce0580 (most recent call first):
  Garbage-collecting
  


And when using a debug build and -Xdev:

../Modules/gcmodule.c:2187: visit_validate: Assertion failed: 
PyObject_GC_Track() object is not valid
Enable tracemalloc to get the memory block allocation traceback

object address  : 0x101a5f690
object refcount : 1
object type : 0x15503f230
object type name: MyModule
object repr : 

Fatal Python error: _PyObject_AssertFailed: _PyObject_AssertFailed
Python runtime state: initialized

Current thread 0x0001019c0580 (most recent call first):
  File "/Users/ronald/Projects/Forks/cpython/build/t.py", line 12 in 
zsh: abort  ./python.exe -Xdev t.py

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[issue46891] Crash in ModuleType subclass with __slots__

[Ronald Oussoren]

Ronald Oussoren  added the comment:

This is with python 3.11 alpha 5 using the installer for macOS.

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[issue46891] Crash in ModuleType subclass with __slots__

[Ronald Oussoren]

New submission from Ronald Oussoren :

The following crashes the interpreter in Python 3.11, and works fine in older 
versions:

# --- script.py 
import types

class MyModule (types.ModuleType):
__slots__ = (
"_MyModule__a",
"_MyModule__b",
)

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

m = MyModule("name")
# -- end of file

The key in this is the ``__slots__`` definition: The script does not crash 
without ``__slots__``, or with a slots tuple with 1 item.

This is a reproducer based on code in PyObjC.

--
components: Interpreter Core
keywords: 3.11regression
messages: 414294
nosy: ronaldoussoren
priority: normal
severity: normal
stage: needs patch
status: open
title: Crash in ModuleType subclass with __slots__
type: crash
versions: Python 3.11

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