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allow references to point to invalid values #2335

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allow references to point to invalid values #2335

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2 changes: 1 addition & 1 deletion src/behavior-considered-undefined.md
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Expand Up @@ -148,7 +148,7 @@ r[undefined.validity.union]
* For a `union`, the exact validity requirements are not decided yet. Obviously, all values that can be created entirely in safe code are valid. If the union has a [zero-sized] field, then every possible value is valid. Further details are [still being debated](https://github.com/rust-lang/unsafe-code-guidelines/issues/438).

r[undefined.validity.reference-box]
* A reference or [`Box<T>`] must be aligned and non-null, it cannot be [dangling], and it must point to a valid value (in case of dynamically sized types, using the actual dynamic type of the pointee as determined by the [metadata]). Note that the last point (about pointing to a valid value) remains a subject of some debate.
* A reference or [`Box<T>`] must be aligned and non-null, and cannot be [dangling].

@RalfJung RalfJung Aug 23, 2026 •
edited by rustbot
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This is missing the requirement that the pointee type must be inhabited (and there is a bit of subtlety around what exactly "inhabited" means).

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r[undefined.validity.wide]
* The [metadata] of a wide reference, [`Box<T>`], or raw pointer must match the type of the [unsized tail]:
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