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Schrödinger's pointer

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It's aligned *and* not aligned!
This commit is contained in:
Lukas Markeffsky 2022-10-23 00:47:21 +02:00
parent df0bcfe644
commit 4696e8906d
2 changed files with 84 additions and 0 deletions
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42
library/core/src/ptr/const_ptr.rs
View file

@ -1402,6 +1402,27 @@ impl<T: ?Sized> *const T {
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // At compiletime, neither `CONST_PTR` nor `CONST_PTR + 1` is aligned.
/// const CONST_PTR: *const i32 = &42;
/// const _: () = assert!(!CONST_PTR.cast::<i64>().is_aligned());
/// const _: () = assert!(!CONST_PTR.wrapping_add(1).cast::<i64>().is_aligned());
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = CONST_PTR;
/// assert_ne!(
/// runtime_ptr.cast::<i64>().is_aligned(),
/// runtime_ptr.wrapping_add(1).cast::<i64>().is_aligned(),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
@ -1492,6 +1513,27 @@ impl<T: ?Sized> *const T {
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // At compiletime, neither `CONST_PTR` nor `CONST_PTR + 1` is aligned.
/// const CONST_PTR: *const i32 = &42;
/// const _: () = assert!(!CONST_PTR.is_aligned_to(8));
/// const _: () = assert!(!CONST_PTR.wrapping_add(1).is_aligned_to(8));
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = CONST_PTR;
/// assert_ne!(
/// runtime_ptr.is_aligned_to(8),
/// runtime_ptr.wrapping_add(1).is_aligned_to(8),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///

42
library/core/src/ptr/mut_ptr.rs
View file

@ -1670,6 +1670,27 @@ impl<T: ?Sized> *mut T {
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // At compiletime, neither `CONST_PTR` nor `CONST_PTR + 1` is aligned.
/// const CONST_PTR: *const i32 = &42;
/// const _: () = assert!(!CONST_PTR.cast::<i64>().is_aligned());
/// const _: () = assert!(!CONST_PTR.wrapping_add(1).cast::<i64>().is_aligned());
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = CONST_PTR;
/// assert_ne!(
/// runtime_ptr.cast::<i64>().is_aligned(),
/// runtime_ptr.wrapping_add(1).cast::<i64>().is_aligned(),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
@ -1760,6 +1781,27 @@ impl<T: ?Sized> *mut T {
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // At compiletime, neither `CONST_PTR` nor `CONST_PTR + 1` is aligned.
/// const CONST_PTR: *const i32 = &42;
/// const _: () = assert!(!CONST_PTR.is_aligned_to(8));
/// const _: () = assert!(!CONST_PTR.wrapping_add(1).is_aligned_to(8));
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = CONST_PTR;
/// assert_ne!(
/// runtime_ptr.is_aligned_to(8),
/// runtime_ptr.wrapping_add(1).is_aligned_to(8),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///