Run bevy_ecs in miri on CI

[bjorn3]

What problem does this solve or what need does it fill?

Bevy_ecs contains a lot of unsafe code. Unsafe code in Bevy has been proven to be unsound on multiple occasions.

What solution would you like?

Run the bevy_ecs test suite in miri to detect UB. Preferably miri would also manually be run on #1525 before it is merged.

What alternative(s) have you considered?

Remove all unsafe code.

Will regress performance by a lot.

Formally verify all unsafe code.

Way too much work.

Manually verify all unsafe code.

Takes a lot of time and will miss some unsoundness.

[cart]

Makes sense to me! Given that miri is pretty slow and the change frequency of bevy_ecs internals is also low, I'm thinking this should probably be a periodic test (daily?). I ran miri prior to creating #1525. I'll do it again before merging.

On main (and #1525), the parallel executor's async-channel usage fails with:

A few days ago I also ran miri on the async-channel crate's tests, which passed. So it's unclear if this is a bevy-call-context issue that exposes a problem in async-channel, a bevy issue, or a miri bug (the error says the rule is experimental).

Additionally, if the test above is commented out, miri has an internal compiler error on another test (which seems to be an indicator that bevy's Future code can't be tested by miri yet):

[bjorn3]

Could you report an issue on rust-lang/rust for the ICE?

[cart]

Sure thing!

[cart]

Looks like a dupe of rust-lang/miri#1038

[NathanSWard]

I would love to try and get miri integrated with CI, however we do seem to be blocked by rust-lang/miri#1038.
(At least for bevy_ecs)

[RalfJung]

rust-lang/miri#1038 is fixed now, btw. :)
Once rust-lang/rust#95144 lands, this will be in the next nightly.