Python 3.11.0a2+ (heads/main:8a45ca542a, Nov 30 2021, 22:40:56) [Clang 13.0.0 (clang-1300.0.29.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> help("modules")

Please wait a moment while I gather a list of all available modules...

/Users/iritkatriel/src/cpython/Lib/pkgutil.py:92: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
  __import__(info.name)
/Users/iritkatriel/src/cpython/Lib/pkgutil.py:92: DeprecationWarning: lib2to3 package is deprecated and may not be able to parse Python 3.10+
  __import__(info.name)
test_sqlite3: testing with version '2.6.0', sqlite_version '3.32.3'
/Users/iritkatriel/src/cpython/Lib/distutils/command/build_ext.py:13: DeprecationWarning: The distutils.sysconfig module is deprecated, use sysconfig instead
  from distutils.sysconfig import customize_compiler, get_python_version
zsh: segmentation fault  ./python.exe

On the debugger: 

>>> help("modules")

Please wait a moment while I gather a list of all available modules...

/Users/iritkatriel/src/cpython/Lib/pkgutil.py:92: DeprecationWarning: The distutils package is deprecated and slated for removal in Python 3.12. Use setuptools or check PEP 632 for potential alternatives
  __import__(info.name)
/Users/iritkatriel/src/cpython/Lib/pkgutil.py:92: DeprecationWarning: lib2to3 package is deprecated and may not be able to parse Python 3.10+
  __import__(info.name)
test_sqlite3: testing with version '2.6.0', sqlite_version '3.32.3'
/Users/iritkatriel/src/cpython/Lib/distutils/command/build_ext.py:13: DeprecationWarning: The distutils.sysconfig module is deprecated, use sysconfig instead
  from distutils.sysconfig import customize_compiler, get_python_version
Process 88596 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x0000000100160046 python.exe`_PyObject_GenericGetAttrWithDict(obj=0x0000000106acfa50, name=0x0000000100fe91c0, dict=0x0000000000000000, suppress=0) at object.c:1305:17
   1302	        PyDictValues **values_ptr = _PyObject_ValuesPointer(obj);
   1303	        if (values_ptr && *values_ptr) {
   1304	            if (PyUnicode_CheckExact(name)) {
-> 1305	                assert(*_PyObject_DictPointer(obj) == NULL);
   1306	                res = _PyObject_GetInstanceAttribute(obj, *values_ptr, name);
   1307	                if (res != NULL) {
   1308	                    goto done;
Target 0: (python.exe) stopped.
(lldb) p _PyObject_Dump(name)
object address  : 0x100fe91c0
object refcount : 165
object type     : 0x10051aec0
object type name: str
object repr     : 'string'
(lldb) p _PyObject_Dump(*_PyObject_DictPointer(obj))
error: Execution was interrupted, reason: Attempted to dereference an invalid pointer..
The process has been returned to the state before expression evaluation.
(lldb) p _PyObject_Dump(obj)
object address  : 0x106acfa50
object refcount : 7
object type     : 0x105add590
object type name: _cffi_backend.FFI
object repr     : <_cffi_backend.FFI object at 0x106acfa50>

It works for me on 3.10.

It's failing in this assertion which was added in https://github.com/python/cpython/pull/28802 :

https://github.com/python/cpython/blob/8a45ca542a65ea27e7acaa44a4c833a27830e796/Objects/object.c#L1305

Works for me on Ubuntu.

Python 3.11.0a2+ (heads/main:0aa0bd0563, Dec  1 2021, 11:39:40) [GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> help("modules")

[lots of output, but no assertion failure or segfault]

>>> 


I note that your debug output includes `_cffi_backend.FFI object`
Is this a cffi bug?

When I say "cffi bug", I should say "is cffi not ported to 3.11 yet?"

Unable to reproduce on macOS 12 with latest 3.11 official build, and my most recent dev build (HEAD at b394af13f69c1a2ac0e7d32dabf6d86443606ab2).

Also unable to reproduce with HEAD at 49444fb807ecb396462c8e5f547eeb5c6bc5d4de.

I'm using MacOS 11.6.

Also unable to reproduce with HEAD at 8a45ca542a65ea27e7acaa44a4c833a27830e796. Perhaps it is related to your build/dev environment?

I'm unable to reproduce on macOS 11.6 as well (head at 49444fb807ecb396462c8e5f547eeb5c6bc5d4de).

* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x000000010015fd26 python.exe`_PyObject_GenericGetAttrWithDict(obj=0x000000013feb7a50, name=0x0000000100fe9350, dict=0x0000000000000000, suppress=0) at object.c:1305:17
   1302	        PyDictValues **values_ptr = _PyObject_ValuesPointer(obj);
   1303	        if (values_ptr && *values_ptr) {
   1304	            if (PyUnicode_CheckExact(name)) {
-> 1305	                assert(*_PyObject_DictPointer(obj) == NULL);
   1306	                res = _PyObject_GetInstanceAttribute(obj, *values_ptr, name);
   1307	                if (res != NULL) {
   1308	                    goto done;
Target 0: (python.exe) stopped.
(lldb) p obj
(PyObject *) $0 = 0x000000013feb7a50
(lldb) p _PyObject_Dump((PyObject*)obj->ob_type)
object address  : 0x13ff25590
object refcount : 32
object type     : 0x100518680
object type name: type
object repr     : <class '_cffi_backend.FFI'>
(lldb) p (PyObject*)obj->ob_type
(PyObject *) $1 = 0x000000013ff25590
(lldb) p (PyObject*)obj->ob_type->tp_dict
(PyObject *) $2 = 0x000000013fedd910
(lldb) p _PyObject_Dump((PyObject*)obj->ob_type->tp_dict)
object address  : 0x13fedd910
object refcount : 1
object type     : 0x100511d50
object type name: dict
object repr     : {'__new__': <built-in method __new__ of type object at 0x13ff25590>, '__getattribute__': <slot wrapper '__getattribute__' of '_cffi_backend.FFI' objects>, '__init__': <slot wrapper '__init__' of '_cffi_backend.FFI' objects>, 'addressof': <method 'addressof' of '_cffi_backend.FFI' objects>, 'alignof': <method 'alignof' of '_cffi_backend.FFI' objects>, 'def_extern': <method 'def_extern' of '_cffi_backend.FFI' objects>, 'callback': <method 'callback' of '_cffi_backend.FFI' objects>, 'cast': <method 'cast' of '_cffi_backend.FFI' objects>, 'dlclose': <method 'dlclose' of '_cffi_backend.FFI' objects>, 'dlopen': <method 'dlopen' of '_cffi_backend.FFI' objects>, 'from_buffer': <method 'from_buffer' of '_cffi_backend.FFI' objects>, 'from_handle': <method 'from_handle' of '_cffi_backend.FFI' objects>, 'gc': <method 'gc' of '_cffi_backend.FFI' objects>, 'getctype': <method 'getctype' of '_cffi_backend.FFI' objects>, 'init_once': <method 'init_once' of '_cffi_backend.FFI' objects>, 'integer_const': <method 'integer_const' of '_cffi_backend.FFI' objects>, 'list_types': <method 'list_types' of '_cffi_backend.FFI' objects>, 'memmove': <method 'memmove' of '_cffi_backend.FFI' objects>, 'new': <method 'new' of '_cffi_backend.FFI' objects>, 'new_allocator': <method 'new_allocator' of '_cffi_backend.FFI' objects>, 'new_handle': <method 'new_handle' of '_cffi_backend.FFI' objects>, 'offsetof': <method 'offsetof' of '_cffi_backend.FFI' objects>, 'release': <method 'release' of '_cffi_backend.FFI' objects>, 'sizeof': <method 'sizeof' of '_cffi_backend.FFI' objects>, 'string': <method 'string' of '_cffi_backend.FFI' objects>, 'typeof': <method 'typeof' of '_cffi_backend.FFI' objects>, 'unpack': <method 'unpack' of '_cffi_backend.FFI' objects>, 'errno': <attribute 'errno' of '_cffi_backend.FFI' objects>, '__doc__': None, 'NULL': <cdata 'void *' NULL>, 'error': <class 'ffi.error'>, 'CType': <class '_cffi_backend.CType'>, 'CData': <class '_cffi_backend._CDataBase'>, 'buffer': <class '_cffi_backend.buffer'>, 'RTLD_LAZY': 1, 'RTLD_NOW': 2, 'RTLD_GLOBAL': 8, 'RTLD_LOCAL': 4, 'RTLD_NODELETE': 128, 'RTLD_NOLOAD': 16}
(lldb) p (PyObject*)obj->ob_type->tp_dictoffset
(PyObject *) $3 = NULL



Because the tp_dictoffset is 0, _PyObject_DictPointer(obj) returns NULL and in the assertion, where the return value is dereferenced, it crashes.

(Note: it's not that the assertion is failing, we don't get that far).

This looks like an issue with 3rd party software cffi. Are you using a fresh build of cffi? The internal ABI of an alpha build changes very often.

How do I check that?

The easiest way is to remove and rebuild 3rd party software.

Christian - that's what it was. I uninstalled cffi and now it works.