Is a stacked borrows error in iced-x86 a problem?

[LunNova]

Is the stacked borrows error: Undefined Behavior: trying to retag from <2907067> for SharedReadOnly permission at alloc355283[0x1], but that tag does not exist in the borrow stack for this location error described in more detail at icedland/iced#455 due to a bug in iced-x86?

[saethlin]

It's nice to hear about people using Miri on iced, I've used that crate as a stress test.

I think you are asking about rust-lang/unsafe-code-guidelines#134 or rust-lang/unsafe-code-guidelines#256 (those issues are about the same situation but have slightly different discussion).

The fact that Stacked Borrows does not accommodate the &Header pattern is generally accepted as a problem with the model. There is an alternative model available in Miri via MIRIFLAGS=-Zmiri-tree-borrows which permits the &Header pattern but it is still somewhat under-construction, #3067 for example.

I would have more confidence in my code being well-behaved if it is accepted by Stacked Borrows. But if you can get Miri to execute more of your code by turning on Tree Borrows instead, that's a good practical option.

[LunNova]

Closing as your answer explains why it failed and it looks like there's existing in progress work. Thanks for the help!