[issue25782] CPython hangs on error __context__ set to the error itself

[Dong-hee Na]

Dong-hee Na  added the comment:

> Serhiy, I'm not closing this yet in case you'd like to finish implementing 
> your PR. If not, feel free to close.

I check that PR 20543 makes CPython works correctly with msg399281 code.

--
nosy: +corona10

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Łukasz Langa]

Łukasz Langa  added the comment:

Serhiy, I'm not closing this yet in case you'd like to finish implementing your 
PR. If not, feel free to close.

--
assignee:  -> serhiy.storchaka

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[miss-islington]

miss-islington  added the comment:


New changeset d86bbe3cff0abefc13e5462cca1fb3344d4a5b52 by Miss Islington (bot) 
in branch '3.10':
bpo-25782: avoid hang in PyErr_SetObject when current exception has a cycle in 
its context chain (GH-27626)
https://github.com/python/cpython/commit/d86bbe3cff0abefc13e5462cca1fb3344d4a5b52


--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Łukasz Langa]

Łukasz Langa  added the comment:


New changeset 6f4cdeddb97532144f93ca37b8b21451f445c7bf by Miss Islington (bot) 
in branch '3.9':
bpo-25782: avoid hang in PyErr_SetObject when current exception has a cycle in 
its context chain (GH-27626) (GH-27707)
https://github.com/python/cpython/commit/6f4cdeddb97532144f93ca37b8b21451f445c7bf


--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[miss-islington]

Change by miss-islington :


--
pull_requests: +26192
pull_request: https://github.com/python/cpython/pull/27707

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[miss-islington]

Change by miss-islington :


--
nosy: +miss-islington
nosy_count: 14.0 -> 15.0
pull_requests: +26191
pull_request: https://github.com/python/cpython/pull/27706

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Łukasz Langa]

Łukasz Langa  added the comment:


New changeset d5c217475c4957a8084ac3f92ae012ece5edc7cb by Irit Katriel in 
branch 'main':
bpo-25782: avoid hang in PyErr_SetObject when current exception has a cycle in 
its context chain (GH-27626)
https://github.com/python/cpython/commit/d5c217475c4957a8084ac3f92ae012ece5edc7cb


--
nosy: +lukasz.langa

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Nikita Sobolev]

Nikita Sobolev  added the comment:

There's also a similar case with python3.9:

```python
>>> class MyError(Exception):
...   ...
... 
>>> e = MyError('e')
>>> e.__context__ = e
>>> 
>>> try:
...   raise e
... except MyError:
...   print('done')
... 
done  # hangs after this
^C^Z
```

The same code works with python3.8
We got hit by this in RustPython: 
https://github.com/RustPython/RustPython/pull/2820

--
nosy: +sobolevn

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

Note that my PR can (and should) be backported, while a change in the semantics 
of __context__ assignment, I'm not sure.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

> Preventing creation of the loop will fix all other code that iterate the 
> __context__ chain.

We can still do / discuss that following Irit's proposed change, which is an 
improvement, IMO.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

> My argument is the loop creation should be prevented at first place.

I agree, but avoiding the hang is higher priority.

> Preventing creation of the loop will fix all other code that iterate the 
> __context__ chain.

There could still be a cycles involving both __context__ and __cause__ links. 
This is why the traceback code uses a visited set to detect cycles.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

My argument is the loop creation should be prevented at first place. 
PyErr_SetObject() is not the only C code that can hang or overflow the stack 
when iterate a loop. Preventing creation of the loop will fix all other code 
that iterate the __context__ chain.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

> No, I meant C -> A -> B -> C -> A 

Oh, good. I support your reasoning and approach, by the way.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

> > the result is  C -> A -> B -> C

> Did you mean C -> A -> B?

No, I meant C -> A -> B -> C -> A 
the cycle remains unchanged.

> By the way, if you applied to this example your reasoning that  
> PyErr_SetObject shouldn't try to fix user bugs, should this example  instead 
> be C -> A -> B -> C -> ... (leaving the cycle as is but just not hanging)? 

Yes, exactly, see above.

> Is it not being changed then because the reasoning doesn't apply, or because 
> we're restricted in what we can do by backwards compatibility?

The reason for leaving the cycle unchanged is not backwards compatibility, it's 
that this function cannot break the cycle in a meaningful way (this is why it's 
hard to agree on how it should do that).

It can't be that A happened in the context of B at the same time that B 
happened in the context of A. So a cycle means there was a bug somewhere, and 
the exception's history is corrupt, so changing it will only make it more 
corrupt and harder to debug.

Note that PyErr_SetObject avoids creating cycles, so the cycle was not created 
by someone catching an exception e and doing "raise e". It was caused by some 
other code tampering with the __context__ in an incorrect way.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

> the result is  C -> A -> B -> C

Did you mean C -> A -> B?

By the way, if you applied to this example your reasoning that PyErr_SetObject 
shouldn't try to fix user bugs, should this example instead be C -> A -> B -> C 
-> ... (leaving the cycle as is but just not hanging)? Is it not being changed 
then because the reasoning doesn't apply, or because we're restricted in what 
we can do by backwards compatibility?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

My patch doesn't change that at all, so it will be the same as it is currently: 
 the result is  C -> A -> B -> C.  (But with my patch if you try to raise 
something in the context of C, it won't hang.)

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

That's okay. I didn't mean to suggest I thought your patch needed to handle 
that case or that we needed to decide it before moving forward. I was just 
wondering what would happen with your patch with it, even if it means a hang. 
Or were you saying that example can't arise in the code path you're modifying?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

Serhiy's patch is modifying a different part of this system - he changes the 
Exception object's SetContext to break cycles when they are first created. 
Dennis and I targeted the place where an exception is about to be raised and it 
gets a __context__ that may contain a cycle already.

I think it's possible to take the more drastic step of preventing the cycles 
being created altogether, as Serhiy did. I would prefer that we raise an 
exception and refuse to create the cycle rather than try to fix it.  I don't 
think we can come up with a meaningful fix to what is, really, a user bug.

In any case, at the moment we have a situation where user bugs (like 
Issue40696) can cause the interpreter to hang, and if we need more time to 
decide about the full strategy, we should at least prevent the hang.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

Yes, that seems like a good approach. And how about with Serhiy's example from 
above?

> If there is a chain A -> B -> C -> D -> E, after assignment C.__context__ = A 
> ...

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Jack O'Connor]

Change by Jack O'Connor :


--
nosy:  -oconnor663

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

Like Dennis' patch, mine changes PyErr_SetObject. The difference is that 
Dennis' patch gets rid of the cycle while mine leaves it as it is, just avoids 
hanging on it.

So in this case:

when trying to set the exception A on top of
B -> C -> D -> E -> C -> ...,

The result would be simply

A -> B -> C -> D -> E -> C -> ...,

As I said in msg391637, a pre-existing cycle is due to a bug somewhere, and I 
don't think PyErr_SetObject can or should try to fix that bug.  Nonsense in, 
nonsense out. If we change it we probably just make it more nonsensical.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

Thanks, Irit. Can you show how your patch behaves using some representative 
examples (maybe using arrow examples from above)? And if it behaves differently 
from Dennis's patch, can you include an example showing that, too?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Larry Hastings]

Change by Larry Hastings :


--
nosy:  -larry

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

I added a third patch to the discussion.  (It overlaps Dennis's suggestion, and 
I'm happy to close it in favour of a tweaked version of Dennis' patch, but I 
thought this would be the simplest way to say what I mean, and hopefully push 
the discussion along).

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Change by Irit Katriel :


--
pull_requests: +26120
pull_request: https://github.com/python/cpython/pull/27626

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Change by Irit Katriel :


--
versions: +Python 3.11 -Python 3.6, Python 3.7, Python 3.8

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Irit Katriel]

Irit Katriel  added the comment:

I agree with Chris that the issue of not hanging is independent of the question 
what to do about the cycle.  The ExitStack issue that brought this issue about 
is now fixed in ExitStack (see issue25786, issue27122).

If we take a step back from that, the situation is this: SetObject's cycle 
detection loop is intended to prevent the creation of new cycles when adding a 
new context link. It hangs when the exception chain has a pre-existing cycle.  
That pre-existing cycle is arguably a bug, and I'm not sure it's SetObject's 
job to do anything about it.

So I would suggest to:
(1) Make it not hang, ASAP because this is a bug in SetObject.
(2) Leave the cycle alone.

--
nosy: +iritkatriel

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[STINNER Victor]

Change by STINNER Victor :


--
nosy:  -vstinner

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Chris Jerdonek  added the comment:

I think this issue needs deeper discussion to know how to proceed.

> If there is a chain A -> B -> C -> D -> E, after assignment C.__context__ = A 
> we will get a chain C -> A -> B -> D -> E. No exception is lost.

I understand not wanting to lose exceptions here. However, if there were a 
separate exception F and the assignment were instead C.__context__ = F without 
raising C, the new chain would be A -> B -> C -> F. We would again lose D -> E. 
So why is that not a problem here, and yet it's a problem above? If we really 
didn't want to lose the exception, we could make it A -> B -> C -> F -> D -> E 
(and if raising C, it would become C -> F -> D -> E).

Thus, I think we may want to consider separately the cases of explicitly 
setting the context (calling PyException_SetContext) and implicitly setting it 
(calling PyErr_SetObject). Maybe when setting explicitly, losing the previous 
value is okay.

Also, there's another option for the top example in the implicit case of 
raising C. We could create a copy C' of C, so the new chain would be C -> A -> 
B -> C' -> D -> E. The code already has logic to create a new exception in 
certain cases: both _PyErr_SetObject and _PyErr_NormalizeException call 
_PyErr_CreateException. There are yet more options but I don't want to lengthen 
this comment further.

Lastly, regarding Dennis's patch, I think the question of how to detect cycles 
should be discussed separately from what the behavior should be.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Chris Jerdonek]

Change by Chris Jerdonek :


--
nosy: +chris.jerdonek

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Dennis Sweeney]

Change by Dennis Sweeney :


--
pull_requests: +19788
pull_request: https://github.com/python/cpython/pull/20539

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Change by Serhiy Storchaka :


--
pull_requests: +19787
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/20543

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Dennis Sweeney]

Dennis Sweeney  added the comment:

For clarification, the existing behavior on master:
When trying to raise the exception H,
F -> G -> H -> I -> NULL
becomes
H -> F -> G -> NULL

But when trying to set the exception A on top of
B -> C -> D -> E -> C -> ...,
it gets stuck in an infinite loop from the existing cycle.

My PR 20539 keeps the first behavior and resolves the infinite loop by making it
A -> B -> C -> D -> E -> NULL,
which seems consistent with the existing behavior.

So it should be strictly a bugfix. It also only changes the PyErr_SetObject 
code and not the PyException_SetContext code.

--
nosy: +Dennis Sweeney

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Gregory P. Smith]

Change by Gregory P. Smith :


--
nosy:  -gregory.p.smith

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Issue40696 is other example of creating a cycle.

I think we should solve general problem preventing loops by merging one of 
proposed patches.

--
resolution: fixed -> 
stage: commit review -> 
status: closed -> open
versions: +Python 3.10, Python 3.7, Python 3.8, Python 3.9 -Python 3.5

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Gregory P. Smith]

Gregory P. Smith  added the comment:

I believe the original issue is fixed, the original problem and the one Jack 
followed up with no longer work in modern Python 3.

But there is discussion about possibly doing something better, if anyone is 
interested in doing that I suggest opening a new Enhancement issue and turning 
the patches floating around into PRs for discussion.

i'm closing this as the worst reported behavior has been fixed.

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

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

What should we do with this issue? Does it need opening a topic on Python-Dev?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Guido van Rossum]

Changes by Guido van Rossum :


--
nosy:  -gvanrossum

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Because we have two alternate solutions, issue25782_5.patch and 
set_context_reordering2.patch.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Larry Hastings]

Larry Hastings added the comment:

Why is this still open?  GPS: didn't your checkin last June fix this?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[larsonreever]

larsonreever added the comment:

My patch works for your example too.  Since it checks for loops in __context__ 
setter, you shouldn't be able to create complicated loops. However, since 
PyException_SetContext and PyException_SetCause are public APIs, and their 
return type is 'void', I can't raise an error when a C code introduces a cycle, 
in that case, the exc->cause/exc->context will be set to NULL.(I came to this 
bug via the ExitStack + subprocess issue27122 which merely has a suggested 
workaround patch as a band aid that might help until this is fixed) 
Thanks: http://driverwhiz.com/device-drivers

--
nosy: +larsonreever

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Terry J. Reedy]

Terry J. Reedy added the comment:

Issue #28962 appears to be an example of this issue.  It uses 'raise e from e' 
to create the loop.

--
nosy: +terry.reedy

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

For reference: the correct issue number is #27122.

Are there examples of creating a loop not involving ExitStack or explicit 
setting the __context__ attribute?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Roundup Robot]

Roundup Robot added the comment:

New changeset 9ee36b74b432 by Gregory P. Smith in branch '3.5':
Issue #27123: When an exception is raised within the context being
https://hg.python.org/cpython/rev/9ee36b74b432

New changeset 9fadeee05880 by Gregory P. Smith in branch 'default':
Issue #27123: When an exception is raised within the context being
https://hg.python.org/cpython/rev/9fadeee05880

--
nosy: +python-dev

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Gregory P. Smith]

Gregory P. Smith added the comment:

I think I'm with Nick on this, the re-ordering fix is the closest to the right 
thing to do for 3.5 as it at least leaves all exceptions present in the chain.

As a more accurate long term fix, it would be great if we could express the 
tree via tuples in exception context in 3.6 or later.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Nick Coghlan]

Nick Coghlan added the comment:

> But fixing this issue by reordering the exception chain will only mask bugs 
> that just better to be fixed.  And sometimes, this will cause weird 
> exceptions chains, that will make *some* people spend a lot of time 
> debugging/googling to understand what's going on.

Right, but the way to fix that is to figure out a more coherent linearisation 
strategy (and/or move away from linearisation by allowing __context__ to be a 
tuple). Both #18861 and the frame annotation idea it spawned in #19585 have 
some ideas on how we might be able to improve that situation.

Adding *yet another* exception to an already confused exception chain isn't 
likely to make it easier to debug, and may mask the original exception that 
triggered the misbehaving error handler (entirely defeating the point of adding 
exception chaining in the first place).

I'm not saying Serhiy's patch is the right long term solution - I'm saying I 
think it's a better short term mitigation measure, since it doesn't lose 
information the way nulling out the __context__ may do.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> issue27122_broken_cm.py also shows why I think "make it work" is the right 
> answer here [..]

But fixing this issue by reordering the exception chain will only mask bugs 
that just better to be fixed.  And sometimes, this will cause weird exceptions 
chains, that will make *some* people spend a lot of time debugging/googling to 
understand what's going on.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Nick Coghlan]

Nick Coghlan added the comment:

Thanks Serhiy. I've attached a new file (issue27122_broken_cm.py) with a 
context manager that is deliberately buggy in the same way as 
contextlib._GeneratorContextManager is currently, so the new test can be made 
independent of #27122 being fixed (Greg Smith has a pending patch to make that 
CM well behaved again, which would currently lead to your new test passing for 
the wrong reasons)

issue27122_broken_cm.py also shows why I think "make it work" is the right 
answer here - the odd context chaining is tolerated in the case where the 
interpreter is implicitly setting the exception context, so I believe it should 
also be tolerated when ExitStack sets the context explicitly. If we "do the 
right thing" (where "right" = "the same as what the interpreter does") in the 
setter, then not only ExitStack, but anyone else setting __context__ should 
automatically benefit from the adjustment.

--
Added file: http://bugs.python.org/file43382/issue27122_broken_cm.py

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

With Yury's path the issue27122 test need to be changed (RuntimeError is now 
raised instead of original exception). Here is updated patch.

--
Added file: http://bugs.python.org/file43381/Issue25782_5.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

With reordering the issue27122 test is passed without changes. No changes in 
ExitStack is needed. Here is updated patch.

--
Added file: http://bugs.python.org/file43380/set_context_reordering2.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Nick Coghlan]

Nick Coghlan added the comment:

For both of the proposed patches, could we add a test case based on 
contextlib.ExitStack and a variant of Victor's #27122 reproducer script at 
http://bugs.python.org/file42999/hang_bug2.py that uses a deliberately broken 
__exit__ implementation that always re-raises the exception thrown into the 
underlying generator?

As discussed on that issue, I'm wondering if we need some additional defensive 
coding in ExitStack itself, or if resolving this underlying problem will be 
enough to also categorically prevent the hang in ExitStack.

As far as possible resolutions go, I tend to prefer lying about the shape of 
the exception state over changing the type of the raised exception - we already 
know the true exception state is a tree rather than a chain (see #18861 for 
some related discussions), and we should be able to ensure that all active 
exceptions remain somewhere in the chain, even if their order is a bit 
surprising.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> Yury's raises a RuntimeError in the loop situation.

> Serhiy's simply reorders the exception context to put the referred to one at 
> the front of the chain in the event of a loop.

Right, and I believe that my solution is more Pythonic.  Reordering feels 
highly unintuitive to me.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Larry Hastings]

Larry Hastings added the comment:

I'm not the right person to decide this.

As RM, all I can do is decide whether or not to hold up a release based on the 
bug.  The answer: no.  Since this isn't fixed yet in the 3.5 branch, 3.5.2 will 
go out without it being fixed.  Sorry folks.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Gregory P. Smith]

Changes by Gregory P. Smith :


--
stage: commit review -> patch review

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Gregory P. Smith]

Gregory P. Smith added the comment:

Patch review: I see two competing solutions with differing behaviors. 

Yury's raises a RuntimeError in the loop situation.

Serhiy's simply reorders the exception context to put the referred to one at 
the front of the chain in the event of a loop.

The 3.5 Release manager or someone familiar with the contextlib ExitStack code 
where this is triggered should make the decision as to the best way to fix this.

(I came to this bug via the ExitStack + subprocess issue27122 which merely has 
a suggested workaround patch as a band aid that might help until this is fixed)

--
nosy: +gregory.p.smith

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Rotem Yaari]

Changes by Rotem Yaari :


--
nosy: +Rotem Yaari

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

And added more comments to your patch.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


Added file: http://bugs.python.org/file41354/set_context_reordering.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


Removed file: http://bugs.python.org/file41353/set_context_reordering.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Here is a patch that illustrates my idea (the documentation could be better).

--
Added file: http://bugs.python.org/file41353/set_context_reordering.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> Serhiy Storchaka added the comment:
> 
> The patch LGTM (but I prefer reordering solution).

Serhiy, could you please describe your solution in more detail? An elaborate 
example would help. Perhaps I just misunderstand your idea. And thanks for the 
review!

--
nosy: +Yury.Selivanov

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

The patch LGTM (but I prefer reordering solution).

--
stage: patch review -> commit review
type:  -> behavior
versions:  -Python 3.3, Python 3.4

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

A new patch is attached.  Please review.

I decided to remove the fix for recursive __cause__.  Currently, `raise e from 
e` doesn't cause any problem, and if we fix the interpreter to raise an 
RuntimeError in such cases it will be a backwards incompatible change.  I don't 
see any point in introducing such a change in a bugfix Python release.  We can 
open a separate issue for 3.6 though.

Fixing __context__ in 3.5.2 is way more important, since the interpreter can 
actually infinitely loop itself in some places.  And since there is no syntax 
for setting __context__ manually (as opposed to __cause__ via raise .. from), I 
suspect that there will be much less people affected by this fix.

--
stage:  -> patch review
Added file: http://bugs.python.org/file41341/Issue25782_4.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Larry Hastings]

Larry Hastings added the comment:

I'm not going to hold up 3.5.1 for this.

--
priority: release blocker -> high

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Changes by Yury Selivanov :


--
nosy: +georg.brandl, larry
priority: normal -> release blocker

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

Looks like this is the original code committed in CPython in 2ee09afee126.  
Patch by Antoine Pitrou.

Antoine, how would you fix this?

--
nosy: +pitrou

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

New submission from Yury Selivanov:

try:
raise Exception
except Exception as ex:
ex.__context__ = ex
hasattr(1, 'aa')

--
components: Interpreter Core
messages: 255731
nosy: gvanrossum, haypo, ncoghlan, yselivanov
priority: normal
severity: normal
status: open
title: CPython hangs on error __context__ set to the error itself
versions: Python 3.3, Python 3.4, Python 3.5, Python 3.6

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

I would change __context__ setter to check if it creates a loop.

--
nosy: +serhiy.storchaka

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

The bug is in "PyErr_SetObject":

while ((context = PyException_GetContext(o))) {
Py_DECREF(context);
if (context == value) {
PyException_SetContext(o, NULL);
break;
}
o = context;
}

The loop can be infinite.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

Serhiy, good idea, thanks!  Please review the attached patch.

Larry, I view this as a very serious bug.  Can we ship 3.5.1 with it fixed?

--
keywords: +patch
Added file: http://bugs.python.org/file41212/Issue25782.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Jack O'Connor]

Jack O'Connor added the comment:

Yury, do we need to handle more complicated infinite loops, where "self" 
doesn't actually show up in the loop? Here's an example:

try:
raise Exception
except Exception as ex:
loop1 = Exception()
loop2 = Exception()
loop1.__context__ = loop2
loop2.__context__ = loop1
ex.__context__ = loop1
hasattr(1, 'aa')

I'm unfamiliar with CPython, so I don't know whether full-blown loop detection 
belongs here. Maybe we could add a hardcoded limit like "fail if we loop more 
than X times"?

--
nosy: +oconnor663

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

>Don't do that, a few hours (!) is not enough to test a fix. It's too
late after a RC1 for such critical change (exceptions).

Maybe we can add an RC2?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> If there is a chain A -> B -> C -> D -> E, after assignment C.__context__ = A 
> we will get a chain C -> A -> B -> D -> E. No exception is lost.

What to do when you try to chain "C -> C"?  

I'm not sure I like this reordering idea -- it might introduce some *very* hard 
to find bugs -- you expected one type of exception, then you used some external 
library, and after that you have a completely different exception.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[STINNER Victor]

STINNER Victor added the comment:

> Maybe we can add an RC2?

Seriously? I'm waiting Python 3.5.1 since 3.5.0 was released. I'm amazed how 
much time it takes to release a first bugfix version, 3.5.0 was full a bugs 
(see the changelog).

It's very easy to workaround this issue in pure Python. Why do you want the fix 
*RIGHT NOW*?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[STINNER Victor]

STINNER Victor added the comment:

Yury Selivanov added the comment:
> Please look at http://bugs.python.org/issue25779.  I think we either should 
> fix this issue, or fix http://bugs.python.org/issue25786 in 3.5.1, since I 
> can't find a workaround for it.  The latter issue is probably easier to get 
> into 3.5.1?

It's a choice for the release manager. But IHMO there will always be
bugs :-) It looks like you found a lot of issues related to exceptions
handling. Maybe it would be better to fix all the them "at once" in
3.5.2? And then ask Larry to release it early?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> Should we do the same for __cause__? Is it possible to create __context__ or 
> __cause__ loop without assigning these attributes directly?

Yes, let's mirror the __context__ behaviour for __cause__.  New patch attached.


Serhiy, Guido,

The new patch raises a TypeError in __cause__ and __context__ setters when a 
cycle was introduced, so in pure Python the following won't work:


   # will throw TypeError("cycle in exception context chain")
   ex.__context__ = ex chain")

   # will throw TypeError("cycle in exception cause chain")
   ex.__cause__ = ex


However, since PyException_SetContext and PyException_SetCause are public APIs, 
and their return type is 'void', I can't raise an error when a C code 
introduces a cycle, in that case, the exc->cause/exc->context will be set to 
NULL.

Thoughts?

I think that this approach is the only sane one here.  We can certainly fix the 
infinite loop in PyErr_SetObject, but it will only be a matter of time until we 
discover a similar loop somewhere else.

--
Added file: http://bugs.python.org/file41214/Issue25782_2.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> Setting it to NULL is one option -- silently ignoring the assignment
(leaving whatever was there) might also be good? In 90% of the cases it
would be the same thing right? 

But leaving the old __context__ there will completely mask the bug...

And as for pure python code -- do you agree we better raise a TypeError if a 
cycle is about to be introduced?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Guido van Rossum]

Guido van Rossum added the comment:

> But leaving the old __context__ there will completely mask the bug...
OK, NULL is fine then.

>we better raise a TypeError if a cycle is about to be introduced?
Yes.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Yet one option is the emersion of the exception. Affected exception is removed 
from the chain and added at it head.

If there is a chain A -> B -> C -> D -> E, after assignment C.__context__ = A 
we will get a chain C -> A -> B -> D -> E. No exception is lost.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[STINNER Victor]

STINNER Victor added the comment:

> Larry, I view this as a very serious bug.  Can we ship 3.5.1 with it fixed?

Don't do that, a few hours (!) is not enough to test a fix. It's too
late after a RC1 for such critical change (exceptions).

The bug was here since at least Python 3.3, there is no urgency to fix it.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> Yury, do we need to handle more complicated infinite loops, where "self" 
> doesn't actually show up in the loop? Here's an example:

My patch works for your example too.  Since it checks for loops in __context__ 
setter, you shouldn't be able to create complicated loops.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> It's very easy to workaround this issue in pure Python. Why do you want the 
> fix *RIGHT NOW*?

Please look at http://bugs.python.org/issue25779.  I think we either should fix 
this issue, or fix http://bugs.python.org/issue25786 in 3.5.1, since I can't 
find a workaround for it.  The latter issue is probably easier to get into 
3.5.1?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Should we do the same for __cause__? Is it possible to create __context__ or 
__cause__ loop without assigning these attributes directly?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Guido van Rossum]

Guido van Rossum added the comment:

Ouch, it's unfortunate those APIs don't have an error return. :-(

Setting it to NULL is one option -- silently ignoring the assignment
(leaving whatever was there) might also be good? In 90% of the cases it
would be the same thing right? (I'm not familiar with this part of the code
TBH.)

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

> What to do when you try to chain "C -> C"?

Nothing. Or may be raise an exception (because C.__context__ can't be set to 
what you try).

> you expected one type of exception, then you used some external library, and 
> after that you have a completely different exception.

I don't understand what new can add the reordering. It doesn't change original 
exception, it only changes __context__, but you change it in any case. If 
silently ignore the loop, you would get __context__ different from what you 
expected. If raise TypeError, you would get TypeError instead of expected 
exception.

And if the decision will be to raise TypeError, may be RuntimeError is more 
appropriate?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Larry Hastings]

Larry Hastings added the comment:

> Please look at http://bugs.python.org/issue25779.

You closed that one and marked it "not a bug"...?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

> You closed that one and marked it "not a bug"...?

That particular issue was about asyncio.  After reducing it, I created two new 
issues -- this one, and another one about another bug in contextlib.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Yury Selivanov]

Yury Selivanov added the comment:

Serhiy, Victor, thank you for your reviews. Another version of the patch is 
attached.

--
Added file: http://bugs.python.org/file41219/Issue25782_3.patch

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue25782] CPython hangs on error __context__ set to the error itself

[Antoine Pitrou]

Changes by Antoine Pitrou :


--
nosy:  -pitrou

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com