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AB Unittest: self-referencing explicit exception cause results in infinite loop · Issue #98458 · python/cpython · GitHub
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Unittest: self-referencing explicit exception cause results in infinite loop #98458

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AlexTate opened this issue Oct 19, 2022 · 1 comment · Fixed by #98459
Closed

Unittest: self-referencing explicit exception cause results in infinite loop #98458

AlexTate opened this issue Oct 19, 2022 · 1 comment · Fixed by #98459
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type-bug An unexpected behavior, bug, or error

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@AlexTate
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AlexTate commented Oct 19, 2022 •
edited by bedevere-bot
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Bug report

If an exception is raised with a self-referencing __cause__ or __context__ then TestResult._clean_tracebacks() in result.py enters an infinite loop.

Minimal example 1:

try:
    raise Exception()
except Exception as e:
    raise e from e

Minimal example 2:

try:
    e = Exception()
    raise e from e
except Exception as e:
    raise e

Identified Cause

Self-references are not checked while unwinding the chained exception on line 216 of result.py

Your environment

  • CPython versions tested on: 3.9, 3.10
  • Operating system and architecture: macOS

Linked PRs
@AlexTate AlexTate added the type-bug An unexpected behavior, bug, or error label Oct 19, 2022
@AlexTate AlexTate mentioned this issue Oct 19, 2022
Merged
This was referenced Dec 4, 2022
Merged
Merged
gpshead pushed a commit that referenced this issue Dec 4, 2022
@AlexTate
gh-98458: unittest: bugfix for infinite loop while handling chained e…
72ec518 
…xceptions that contain cycles (#98459)

* Bugfix addressing infinite loop while handling self-referencing chained exception in TestResult._clean_tracebacks()
* Bugfix extended to properly handle exception cycles in _clean_tracebacks. The "seen" set follows the approach used in the TracebackException class (thank you @iritkatriel for pointing it out)
* adds a test for a single chained exception that holds a self-loop in its __cause__ and __context__ attributes
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Dec 4, 2022
@AlexTate @miss-islington
pythongh-98458: unittest: bugfix for infinite loop while handling cha…
7354ce6 
…ined exceptions that contain cycles (pythonGH-98459)

* Bugfix addressing infinite loop while handling self-referencing chained exception in TestResult._clean_tracebacks()
* Bugfix extended to properly handle exception cycles in _clean_tracebacks. The "seen" set follows the approach used in the TracebackException class (thank you @iritkatriel for pointing it out)
* adds a test for a single chained exception that holds a self-loop in its __cause__ and __context__ attributes
(cherry picked from commit 72ec518)

Co-authored-by: AlexTate <0xalextate@gmail.com>
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Dec 4, 2022
@AlexTate @miss-islington
pythongh-98458: unittest: bugfix for infinite loop while handling cha…
ad4f59a 
…ined exceptions that contain cycles (pythonGH-98459)

* Bugfix addressing infinite loop while handling self-referencing chained exception in TestResult._clean_tracebacks()
* Bugfix extended to properly handle exception cycles in _clean_tracebacks. The "seen" set follows the approach used in the TracebackException class (thank you @iritkatriel for pointing it out)
* adds a test for a single chained exception that holds a self-loop in its __cause__ and __context__ attributes
(cherry picked from commit 72ec518)

Co-authored-by: AlexTate <0xalextate@gmail.com>
@gpshead
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gpshead commented Dec 4, 2022

Thanks! A bit of an unusual issue but no doubt a pain to debug when something winds up with this happening.
The backport PRs should automerge after CI runs.

miss-islington added a commit that referenced this issue Dec 4, 2022
@miss-islington @AlexTate
gh-98458: unittest: bugfix for infinite loop while handling chained e…
e699e5c 
…xceptions that contain cycles (GH-98459)

* Bugfix addressing infinite loop while handling self-referencing chained exception in TestResult._clean_tracebacks()
* Bugfix extended to properly handle exception cycles in _clean_tracebacks. The "seen" set follows the approach used in the TracebackException class (thank you @iritkatriel for pointing it out)
* adds a test for a single chained exception that holds a self-loop in its __cause__ and __context__ attributes
(cherry picked from commit 72ec518)

Co-authored-by: AlexTate <0xalextate@gmail.com>
miss-islington added a commit that referenced this issue Dec 4, 2022
@miss-islington @AlexTate
gh-98458: unittest: bugfix for infinite loop while handling chained e…
9bcc68b 
…xceptions that contain cycles (GH-98459)

* Bugfix addressing infinite loop while handling self-referencing chained exception in TestResult._clean_tracebacks()
* Bugfix extended to properly handle exception cycles in _clean_tracebacks. The "seen" set follows the approach used in the TracebackException class (thank you @iritkatriel for pointing it out)
* adds a test for a single chained exception that holds a self-loop in its __cause__ and __context__ attributes
(cherry picked from commit 72ec518)

Co-authored-by: AlexTate <0xalextate@gmail.com>
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