Emergency Self-Construct

@slayoo thank you for the confirmation, I have updated the labels accordingly.

This still reproduces, on OSX even with current `master` (cbb4301852d0950f15eef0a2b8c0478db5d57201): ``` 💣 zsh» python issu6640.py :( Traceback (most recent call last): File "/Users/vhaenel/git/numba/numba/core/pythonapi.py", line 1371, in serialize_object gv = self.module.__serialized[obj]...

@tombh thanks I can confirm I am seeing this on `master` (5f6859908e7b73f7e1baf30381bac9e863640210) too.

This may be potentially related: https://github.com/numba/numba/issues/3772

Code for the `set` in Numba is here: https://github.com/numba/numba/blob/master/numba/cpython/setobj.py

also, it is perhaps worth noting that `ctrl-c` (`SIGINT`) will not kill the running process, only `ctrl-z` (`SIGSSTOP`) followed by `kill -9` will.

@icezyclon can I ask, how did you go about crafting these reproducers? Is there any way we can find a shorter one? Or do you have any hunches as to...

@icezyclon I see, so basically you used fuzzing to find a broken case, very intersting. I have debugged this today, and I believe the lookup breaks when "slots" in the...

@icezyclon thanks for looking into this. I also ran the `test_sets.py` code with my experimental patch and they do pass. Probably this is an indicator that the test coverage is...

@icezyclon here is the next iteration to fix this: ``` diff --git c/numba/cpython/setobj.py i/numba/cpython/setobj.py index 88532f3d45..e9000b68b5 100644 --- c/numba/cpython/setobj.py +++ i/numba/cpython/setobj.py @@ -216,10 +216,11 @@ class _SetPayload(object): # The index...