expression in assignments are evaluated and can cause pylint to run out of memory or time

[jkrinke]

Steps to reproduce

1. Create a file that only contains v=999999999999999**999999999999999
2. Run pylon on it.

Current behavior

Pylint seems to evaluate the expression of the assignment which will take a very long time and in the end will run out of time.

Expected behavior

Pylint should not attempt evaluation expressions.

pylint --version output

pylint 2.6.0
astroid 2.4.2
Python 3.8.6 (default, Sep 28 2020, 04:41:02)
[Clang 11.0.3 (clang-1103.0.32.62)]

[hippo91]

@jkrinke thanks for this report. However i'm not sure this is really an issue.
astroid, the inference engine used by pylint, has to evaluate some simple expression to be able to infer correctly more complex expressions. Moreover if plyint takes a long time to evaluate, then python will do so.
It may be interesting to monitor this execution time and raise a warning if it takes too much time.

[jkrinke]

@hippo91 the behaviour is problematic in a CI/CD setting where one expects that a static analysis tool would not crash (run out of memory) or not terminate.

I am currently running pylint on the above file. After 48h of run time, the process now uses 4GB of main memory. I expect that the machine would come to a grinding halt within 96h of run time. Let's assume an extremely fast processor - then pylint would crash running out of main memory within a short time. I would consider this a bug...

[jkrinke]

It may be a problem of Python 3 in general: https://stackoverflow.com/questions/34113609/why-does-python-preemptively-hang-when-trying-to-calculate-a-very-large-number

[hippo91]

@jkrinke it seems indeed that it is not related to pylint.
I close the issue but will reopen it if needed.