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Rollup merge of #121935 - RalfJung:ptr-without-prov, r=scottmcm

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library/ptr: mention that ptr::without_provenance is equivalent to deriving from the null ptr

This might help clarify why you can't do memory accesses with it.
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Matthias Krüger 2024-03-03 22:56:14 +01:00 committed by GitHub
commit dc8b71ae2b
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library/core/src/ptr/mod.rs
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@ -574,6 +574,8 @@ pub const fn null_mut<T: ?Sized + Thin>() -> *mut T {
/// Creates a pointer with the given address and no provenance.
///
/// This is equivalent to `ptr::null().with_addr(addr)`.
///
/// Without provenance, this pointer is not associated with any actual allocation. Such a
/// no-provenance pointer may be used for zero-sized memory accesses (if suitably aligned), but
/// non-zero-sized memory accesses with a no-provenance pointer are UB. No-provenance pointers are
@ -616,6 +618,8 @@ pub const fn dangling<T>() -> *const T {
/// Creates a pointer with the given address and no provenance.
///
/// This is equivalent to `ptr::null_mut().with_addr(addr)`.
///
/// Without provenance, this pointer is not associated with any actual allocation. Such a
/// no-provenance pointer may be used for zero-sized memory accesses (if suitably aligned), but
/// non-zero-sized memory accesses with a no-provenance pointer are UB. No-provenance pointers are