bpo-45691: Make array of small ints static to fix use-after-free error.

[markshannon]

https://bugs.python.org/issue45691

[ericsnowcurrently]

Note the small ints have been in PyInterpreterState for a while. We didn't get use-after-free until gh-29274. So perhaps we could just revert that one? The general underlying problem in bpo-45691 is one we'll have to fix regardless, so there's no need to go all the way back to using a static global.

Otherwise this looks fine.

(I'm approving assuming that you'll take my feedback into consideration before merging and discuss if you disagree.)

[markshannon]

As I stated in bpo-45691, we need to make everything static or per-interpreter. Right now that means static.

The best way to move towards multiple interpreters is to merge all the static state into a single struct. That way there is only one static value to convert to per-interpreter when we are ready.

We can start with the small ints 🙂

[ericsnowcurrently]

The best way to move towards multiple interpreters is to merge all the static state into a single struct.

FYI, that's exactly what _PyRuntimeState is (with a handful of things that will stay global). 🙂

[ericsnowcurrently]

I'm good with this.