[issue44483] Fatal error in type union

[Ken Jin]

Ken Jin  added the comment:

Oh, that's a good point too. Thanks for the explanation, reviews and merge 
Serhiy.

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[issue44483] Fatal error in type union

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Yes, Checking each result individually is a right way. Not only because 
performance, but because calling any Python code while an error is set will 
cause a crash in debug build and weird bugs in release build. It is better to 
return as fast as you have an error.

Thank you for your PR Ken Jin.

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

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[issue44483] Fatal error in type union

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:


New changeset 7e6cad7e303b3991360a0fe332b0d21aa0f6fe5e by Miss Islington (bot) 
in branch '3.10':
bpo-44483: Fix crash in union object with bad ``__module__`` (GH-26848) 
(GH-26852)
https://github.com/python/cpython/commit/7e6cad7e303b3991360a0fe332b0d21aa0f6fe5e


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[issue44483] Fatal error in type union

[miss-islington]

Change by miss-islington :


--
nosy: +miss-islington
nosy_count: 2.0 -> 3.0
pull_requests: +25433
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/26852

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[issue44483] Fatal error in type union

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:


New changeset adfa1ba398c74720b42f16f06fd3ec0353599fa5 by Ken Jin in branch 
'main':
bpo-44483: Fix crash in union object with bad ``__module__`` (GH-26848)
https://github.com/python/cpython/commit/adfa1ba398c74720b42f16f06fd3ec0353599fa5


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[issue44483] Fatal error in type union

[Ken Jin]

Ken Jin  added the comment:

A possible simple fix is to change these lines 
https://github.com/python/cpython/blob/main/Objects/unionobject.c#L294-L301

to:
```
return (
is_typevar(obj) |
is_new_type(obj) |
is_special_form(obj) |
PyType_Check(obj) |
PyObject_TypeCheck(obj, _GenericAliasType) |
(int)(type == &_Py_UnionType));
```

However, that may slow down union a little since we lose the short-circuiting 
that `||` provides over `|`, and all checks have to be evaluated.

Checking each result individually and mimicking the short circuiting behavior 
works too, so I did that. What do you think Serhiy?

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[issue44483] Fatal error in type union

[Ken Jin]

Change by Ken Jin :


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keywords: +patch
nosy: +kj
nosy_count: 1.0 -> 2.0
pull_requests: +25429
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/26848

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[issue44483] Fatal error in type union

[Serhiy Storchaka]

New submission from Serhiy Storchaka :

The following example crashes:

class TypeVar:
@property
def __module__(self):
1/0

str | TypeVar()


Output:
Fatal Python error: _Py_CheckSlotResult: Slot | of type type succeeded with an 
exception set
Python runtime state: initialized
Traceback (most recent call last):
  File "", line 4, in __module__
ZeroDivisionError: division by zero
Aborted (core dumped)

The problem in Objects/unionobject.c is that is_typing_module() (and therefore 
is_typevar() and is_special_form()) can return not only 0 and 1, but -1 as a 
signal of error, but is_unionable() does not check results for error and 
interprets it as boolean true.

--
assignee: serhiy.storchaka
components: Interpreter Core
messages: 396307
nosy: serhiy.storchaka
priority: normal
severity: normal
status: open
title: Fatal error in type union
type: crash
versions: Python 3.10, Python 3.11

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