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Revert isize::MAX changes to Layout helpers

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The isize::MAX is enforced by the constructor; let it handle it.
This commit is contained in:
Christopher Durham 2022-06-29 23:17:15 -04:00
parent 7b58193f90
commit c4b4c64804
1 changed files with 16 additions and 37 deletions
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53
library/core/src/alloc/layout.rs
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@ -1,5 +1,4 @@
use crate::cmp; use crate::cmp;
use crate::convert::TryFrom;
use crate::fmt; use crate::fmt;
use crate::mem; use crate::mem;
use crate::num::NonZeroUsize; use crate::num::NonZeroUsize;
@ -303,18 +302,10 @@ impl Layout {
// > must not overflow isize (i.e., the rounded value must be // > must not overflow isize (i.e., the rounded value must be
// > less than or equal to `isize::MAX`) // > less than or equal to `isize::MAX`)
let padded_size = self.size() + self.padding_needed_for(self.align()); let padded_size = self.size() + self.padding_needed_for(self.align());
// Size manipulation is done in isize space to avoid overflowing isize. let alloc_size = padded_size.checked_mul(n).ok_or(LayoutError)?;
let n = isize::try_from(n).map_err(|_| LayoutError)?;
let alloc_size = (padded_size as isize).checked_mul(n).ok_or(LayoutError)?;
// SAFETY: self.align is already known to be valid and alloc_size has been // The safe constructor is called here to enforce the isize size limit.
// padded already. Layout::from_size_align(alloc_size, self.align()).map(|layout| (layout, padded_size))
unsafe {
Ok((
Layout::from_size_align_unchecked(alloc_size as usize, self.align()),
padded_size as usize,
))
}
} }
/// Creates a layout describing the record for `self` followed by /// Creates a layout describing the record for `self` followed by
@ -368,12 +359,12 @@ impl Layout {
let new_align = cmp::max(self.align(), next.align()); let new_align = cmp::max(self.align(), next.align());
let pad = self.padding_needed_for(next.align()); let pad = self.padding_needed_for(next.align());
// Size manipulation is done in isize space to avoid overflowing isize. let offset = self.size().checked_add(pad).ok_or(LayoutError)?;
let offset = (self.size() as isize).checked_add(pad as isize).ok_or(LayoutError)?; let new_size = offset.checked_add(next.size()).ok_or(LayoutError)?;
let new_size = offset.checked_add(next.size() as isize).ok_or(LayoutError)?;
let layout = Layout::from_size_align(new_size as usize, new_align)?; // The safe constructor is called here to enforce the isize size limit.
Ok((layout, offset as usize)) let layout = Layout::from_size_align(new_size, new_align)?;
Ok((layout, offset))
} }
/// Creates a layout describing the record for `n` instances of /// Creates a layout describing the record for `n` instances of
@ -391,9 +382,8 @@ impl Layout {
#[unstable(feature = "alloc_layout_extra", issue = "55724")] #[unstable(feature = "alloc_layout_extra", issue = "55724")]
#[inline] #[inline]
pub fn repeat_packed(&self, n: usize) -> Result<Self, LayoutError> { pub fn repeat_packed(&self, n: usize) -> Result<Self, LayoutError> {
// Size manipulation is done in isize space to avoid overflowing isize. let size = self.size().checked_mul(n).ok_or(LayoutError)?;
let n = isize::try_from(n).map_err(|_| LayoutError)?; // The safe constructor is called here to enforce the isize size limit.
let size = (self.size() as isize).checked_mul(n).ok_or(LayoutError)?;
Layout::from_size_align(size as usize, self.align()) Layout::from_size_align(size as usize, self.align())
} }
@ -406,10 +396,9 @@ impl Layout {
#[unstable(feature = "alloc_layout_extra", issue = "55724")] #[unstable(feature = "alloc_layout_extra", issue = "55724")]
#[inline] #[inline]
pub fn extend_packed(&self, next: Self) -> Result<Self, LayoutError> { pub fn extend_packed(&self, next: Self) -> Result<Self, LayoutError> {
// Size manipulation is done in isize space to avoid overflowing isize. let new_size = self.size().checked_add(next.size()).ok_or(LayoutError)?;
let new_size = // The safe constructor is called here to enforce the isize size limit.
(self.size() as isize).checked_add(next.size() as isize).ok_or(LayoutError)?; Layout::from_size_align(new_size, self.align())
Layout::from_size_align(new_size as usize, self.align())
} }
/// Creates a layout describing the record for a `[T; n]`. /// Creates a layout describing the record for a `[T; n]`.
@ -418,19 +407,9 @@ impl Layout {
#[stable(feature = "alloc_layout_manipulation", since = "1.44.0")] #[stable(feature = "alloc_layout_manipulation", since = "1.44.0")]
#[inline] #[inline]
pub fn array<T>(n: usize) -> Result<Self, LayoutError> { pub fn array<T>(n: usize) -> Result<Self, LayoutError> {
// Size manipulation is done in isize space to avoid overflowing isize. let array_size = mem::size_of::<T>().checked_mul(n).ok_or(LayoutError)?;
let n = isize::try_from(n).map_err(|_| LayoutError)?; // The safe constructor is called here to enforce the isize size limit.
let array_size = (mem::size_of::<T>() as isize).checked_mul(n).ok_or(LayoutError)?; Layout::from_size_align(array_size, mem::align_of::<T>())
// SAFETY:
// - Size: `array_size` cannot be too big because `size_of::<T>()` must
// be a multiple of `align_of::<T>()`. Therefore, `array_size`
// rounded up to the nearest multiple of `align_of::<T>()` is just
// `array_size`. And `array_size` cannot be too big because it was
// just checked by the `checked_mul()`.
// - Alignment: `align_of::<T>()` will always give an acceptable
// (non-zero, power of two) alignment.
Ok(unsafe { Layout::from_size_align_unchecked(array_size as usize, mem::align_of::<T>()) })
} }
} }