Remove int2ptr cast in bevy_ptr::dangling_with_align and remove -Zmiri-permissive-provenance in CI
#15311
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SkiFire13
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bevy_ptr::dangling_with_alignbevy_ptr::dangling_with_align and remove -Zmiri-permissive-provenance in CI
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bevy_ptr::dangling_with_align and remove -Zmiri-permissive-provenance in CIbevy_ptr::dangling_with_align and remove -Zmiri-permissive-provenance in CI
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Co-authored-by: François Mockers <[email protected]>
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# Objective - `bevy_ptr::dangling_with_align()` is only used once, in `bevy_ecs`'s `BlobArray::with_capacity()`, and it isn't generally useful outside of the engine's internals. We can remove the function and inline its implementation into its call site. - Additionally, `bevy_ptr::dangling_with_align()` has a TODO comment that was leftover from #15311 (comment), where it was suggested that `dangling_with_align()` should use `without_provenance()`. - `with_addr()`, mentioned in the TODO comment, could also be used, but it's a more roundabout solution. The reason it was mentioned was because the original author thought it would be stabilized before `without_provenance()`. ## Solution - Remove `dangling_with_align()`. - Replace its usage with `NonNull::without_provenance()` (since it is now stable and doesn't require `unsafe` or pointer math) ## Testing - I ran Miri with strict provenance checking enabled to ensure the behavior is maintained. - `MIRIFLAGS="-Zmiri-strict-provenance" cargo +nightly miri test` ## But what is this provenance thingy? [The official docs provide a more in-depth explanation](https://doc.rust-lang.org/stable/std/ptr/index.html#provenance), but basically a pointer is more than just a number referring to a memory address. Pointers have _permissions_ associated with them that track: - What set of memory addresses are allowed to be accessed - When the pointer is allowed to access those addresses - If the pointer is allowed to mutate the memory, or just read it These permissions are pointer provenance. They aren't stored at runtime, the Rust compiler doesn't know them at compile time! Miri is the only tool that I know of that tracks provenance, which it uses to ensure pointers adheres to their spatial, temporal, and mutability permissions. That's why I mentioned Miri in the Testing section. :)
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Objective
bevy_ptr::dangling_with_align-Zmiri-permissive-provenanceis used (like in CI)-Zmiri-permissive-provenancein CISolution
std::ptr::without_provenancedoes, i.e. by starting from a null pointer.