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An errornous __length_hint__ can make list() raise a SystemError #45894

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avassalotti opened this issue Dec 4, 2007 · 4 comments
Closed

An errornous __length_hint__ can make list() raise a SystemError #45894

avassalotti opened this issue Dec 4, 2007 · 4 comments
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@rhettinger
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type-bug An unexpected behavior, bug, or error

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@avassalotti
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BPO 1553
Nosy @rhettinger, @tiran, @avassalotti

Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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GitHub fields:

assignee = 'https://github.com/rhettinger'
closed_at = <Date 2007-12-05.12:54:32.701>
created_at = <Date 2007-12-04.05:43:57.401>
labels = ['type-bug']
title = 'An errornous __length_hint__ can make list() raise a SystemError'
updated_at = <Date 2007-12-05.12:54:32.671>
user = 'https://github.com/avassalotti'

bugs.python.org fields:

activity = <Date 2007-12-05.12:54:32.671>
actor = 'christian.heimes'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2007-12-05.12:54:32.701>
closer = 'christian.heimes'
components = []
creation = <Date 2007-12-04.05:43:57.401>
creator = 'alexandre.vassalotti'
dependencies = []
files = []
hgrepos = []
issue_num = 1553
keywords = []
message_count = 4.0
messages = ['58176', '58178', '58208', '58213']
nosy_count = 3.0
nosy_names = ['rhettinger', 'christian.heimes', 'alexandre.vassalotti']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue1553'
versions = ['Python 2.6', 'Python 2.5', 'Python 3.0']
@avassalotti
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If an iterator with a __length_hint__ method that returns a negative
integer is passed to list(), a SystemError is raised.

>>> class A:
...     def __iter__(self):
...         return self
...     def __length_hint__(self):
...         return -1
... 
>>> list(A())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
SystemError: NULL result without error in PyObject_Call

@avassalotti avassalotti added the type-bug An unexpected behavior, bug, or error label Dec 4, 2007
@avassalotti
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Fixed for Py3k in r59316.

Should this gets backported?

@rhettinger
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Please post the patch here. I'll take a look to see if it should be
backported.

@rhettinger rhettinger self-assigned this Dec 5, 2007
@tiran
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tiran commented Dec 5, 2007

I've backported the fix to 2.5 and trunk. They suffered from the same
problem.

@tiran tiran closed this as completed Dec 5, 2007
@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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