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make ptr::invalid not the same as a regular int2ptr cast #97219

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May 21, 2022
Merged

make ptr::invalid not the same as a regular int2ptr cast #97219

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12 changes: 10 additions & 2 deletions library/core/src/ptr/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -555,7 +555,11 @@ pub const fn null_mut<T>() -> *mut T {
#[unstable(feature = "strict_provenance", issue = "95228")]
pub const fn invalid<T>(addr: usize) -> *const T {
// FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.
addr as *const T
// We use transmute rather than a cast so tools like Miri can tell that this
// is *not* the same as from_exposed_addr.
// SAFETY: every valid integer is also a valid pointer (as long as you don't dereference that
// pointer).
unsafe { mem::transmute(addr) }
}

/// Creates an invalid mutable pointer with the given address.
Expand All @@ -582,7 +586,11 @@ pub const fn invalid<T>(addr: usize) -> *const T {
#[unstable(feature = "strict_provenance", issue = "95228")]
pub const fn invalid_mut<T>(addr: usize) -> *mut T {
// FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.
addr as *mut T
// We use transmute rather than a cast so tools like Miri can tell that this
// is *not* the same as from_exposed_addr.
// SAFETY: every valid integer is also a valid pointer (as long as you don't dereference that
// pointer).
unsafe { mem::transmute(addr) }
}

/// Convert an address back to a pointer, picking up a previously 'exposed' provenance.
Expand Down