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| author | Dylan DPC <99973273+Dylan-DPC@users.noreply.github.com> | 2022-04-09 18:26:25 +0200 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2022-04-09 18:26:25 +0200 |
| commit | e4b4bf1535ab3539c4573c8d960214c6e49eb138 (patch) | |
| tree | 4d1f4e3804268b1973d078805dc4f6537473cc99 /library/core/src/alloc | |
| parent | 1ced0b61a43d67ef209fc2fa8c4da783daa2471e (diff) | |
| parent | fe0c08a4f24ff7e6fb03b61656436bfa5ff29ac7 (diff) | |
| download | rust-e4b4bf1535ab3539c4573c8d960214c6e49eb138.tar.gz rust-e4b4bf1535ab3539c4573c8d960214c6e49eb138.zip | |
Rollup merge of #95361 - scottmcm:valid-align, r=Mark-Simulacrum
Make non-power-of-two alignments a validity error in `Layout` Inspired by the zulip conversation about how `Layout` should better enforce `size <= isize::MAX as usize`, this uses an N-variant enum on N-bit platforms to require at the validity level that the existing invariant of "must be a power of two" is upheld. This was MIRI can catch it, and means there's a more-specific type for `Layout` to store than just `NonZeroUsize`. It's left as `pub(crate)` here; a future PR could consider giving it a tracking issue for non-internal usage.
Diffstat (limited to 'library/core/src/alloc')
| -rw-r--r-- | library/core/src/alloc/layout.rs | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/library/core/src/alloc/layout.rs b/library/core/src/alloc/layout.rs index db6898c1308..612e366cedf 100644 --- a/library/core/src/alloc/layout.rs +++ b/library/core/src/alloc/layout.rs @@ -1,7 +1,6 @@ use crate::cmp; use crate::fmt; -use crate::mem; -use crate::num::NonZeroUsize; +use crate::mem::{self, ValidAlign}; use crate::ptr::NonNull; // While this function is used in one place and its implementation @@ -40,7 +39,7 @@ pub struct Layout { // // (However, we do not analogously require `align >= sizeof(void*)`, // even though that is *also* a requirement of `posix_memalign`.) - align_: NonZeroUsize, + align_: ValidAlign, } impl Layout { @@ -97,8 +96,8 @@ impl Layout { #[must_use] #[inline] pub const unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Self { - // SAFETY: the caller must ensure that `align` is greater than zero. - Layout { size_: size, align_: unsafe { NonZeroUsize::new_unchecked(align) } } + // SAFETY: the caller must ensure that `align` is a power of two. + Layout { size_: size, align_: unsafe { ValidAlign::new_unchecked(align) } } } /// The minimum size in bytes for a memory block of this layout. @@ -117,7 +116,7 @@ impl Layout { without modifying the layout"] #[inline] pub const fn align(&self) -> usize { - self.align_.get() + self.align_.as_nonzero().get() } /// Constructs a `Layout` suitable for holding a value of type `T`. |