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JIT (correctness): Different UnboundLocalError for same code with JIT on or off #140104
Description
Bug report
Bug description:
The following code results in two different UnboundLocalError exceptions depending on whether it's run with the JIT on or off:
def f():
if 0:
class Class:
pass
if 0:
instance = Class()
for _ in range(5000):
try:
_ = instance.f()
except Exception:
pass
Class.__bases__ = (object,)
f()With JIT on, the UnboundLocalError points to 'instance', while with JIT off it points to 'Class'.
Traceback with JIT on:
Traceback (most recent call last):
File "/home/danzin/divergences/divergence_child_6010_3_1.py", line 17, in <module>
f()
~^^
File "/home/danzin/divergences/divergence_child_6010_3_1.py", line 12, in f
_ = instance.f()
^^^^^^^^
UnboundLocalError: cannot access local variable 'instance' where it is not associated with a valueTraceback with JIT off:
Traceback (most recent call last):
File "/home/danzin/divergences/divergence_child_6010_3_1.py", line 17, in <module>
f()
~^^
File "/home/danzin/divergences/divergence_child_6010_3_1.py", line 15, in f
Class.__bases__ = (object,)
^^^^^
UnboundLocalError: cannot access local variable 'Class' where it is not associated with a valueOutput for PYTHON_LLTRACE=4:
divergence_01_lltrace.txt
Output for PYTHON_OPT_DEBUG=4:
divergence_01_opt_debug.txt
Please let me know whether you're able to reproduce this issue.
Found using lafleur.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux
Linked PRs
- gh-140104: Set next_instr properly in the JIT during exceptions #140233
- [3.14] gh-140104: Set next_instr properly in the JIT during exceptions (GH-140233) #140687
- [3.14] gh-140104: Revert "Set next_instr properly in the JIT during exceptions (GH-140233) (GH-140687)" #140890
- [3.14] gh-140104: Set next_instr properly in the JIT during exceptions (GH-140233) #141495
Activity
Fidget-Spinner commentedon Oct 14, 2025
It's possible #139109 might end up fixing this inadvertently, so let's not fix this for now maybe? Or we could fix it with the knowledge the code will be ripped out soon.
devdanzin commentedon Oct 15, 2025
Here's a simpler reproducer for what seems to be the same issue:
This one runs to completion without the JIT and raises an exception with it.
gh-140104: Set next_instr properly in the JIT during exceptions (GH-1…
efimov-mikhail commentedon Oct 27, 2025
We need a backport for 3.14, don't we?
Or we ignore backports since JIT is in expiremental stage?
Fidget-Spinner commentedon Oct 27, 2025
Let's backport to 3.14 but not 3.13.
Fidget-Spinner commentedon Oct 27, 2025
Backport failed, maybe I should open up the backport to anyone who wants to try please?
efimov-mikhail commentedon Oct 27, 2025
I'd like to provide this backport.
pythongh-140104: Set next_instr properly in the JIT during exceptions (…
[3.14] gh-140104: Set next_instr properly in the JIT during exceptions (
Fidget-Spinner commentedon Nov 1, 2025
This is still broken on 3.14 sadly.
Revert "[3.14] pythongh-140104: Set next_instr properly in the JIT du…
efimov-mikhail commentedon Nov 1, 2025
I'm sorry. It seems that I've tested incorrectly.
It's actually still broken on 3.14.
Fidget-Spinner commentedon Nov 1, 2025
No worries. I didn't realize CI didn't trigger for JIT on the backport either!
[3.14] gh-140104: Revert "Set next_instr properly in the JIT during e…
[3.14] gh-140104: Set next_instr properly in the JIT during exceptions (
pythongh-140104: Set next_instr properly in the JIT during exceptions (…