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Add a precondition check for Layout::from_size_align_unchecked

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This commit is contained in:
Ben Kimock 2024-06-16 12:58:08 -04:00
parent 27b93da8de
commit 7f5d282185
2 changed files with 27 additions and 7 deletions
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32
library/core/src/alloc/layout.rs
View File

@ -6,7 +6,7 @@
use crate::error::Error;
use crate::ptr::{Alignment, NonNull};
use crate::{cmp, fmt, mem};
use crate::{assert_unsafe_precondition, cmp, fmt, mem};
// While this function is used in one place and its implementation
// could be inlined, the previous attempts to do so made rustc
@ -66,12 +66,25 @@ impl Layout {
#[inline]
#[rustc_allow_const_fn_unstable(ptr_alignment_type)]
pub const fn from_size_align(size: usize, align: usize) -> Result<Self, LayoutError> {
if !align.is_power_of_two() {
return Err(LayoutError);
if Layout::is_size_align_valid(size, align) {
// SAFETY: Layout::is_size_align_valid checks the preconditions for this call.
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
Ok(layout)
} else {
Err(LayoutError)
}
}
// SAFETY: just checked that align is a power of two.
Layout::from_size_alignment(size, unsafe { Alignment::new_unchecked(align) })
const fn is_size_align_valid(size: usize, align: usize) -> bool {
if !align.is_power_of_two() {
return false;
}
// SAFETY: Precondition checked directly above.
let align = unsafe { Alignment::new_unchecked(align) };
if size > Self::max_size_for_align(align) {
return false;
}
true
}
#[inline(always)]
@ -116,6 +129,15 @@ const fn from_size_alignment(size: usize, align: Alignment) -> Result<Self, Layo
#[inline]
#[rustc_allow_const_fn_unstable(ptr_alignment_type)]
pub const unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Self {
assert_unsafe_precondition!(
check_library_ub,
"Layout::from_size_align_unchecked requires that align is a power of 2 \
and the rounded-up allocation size does not exceed isize::MAX",
(
size: usize = size,
align: usize = align,
) => Layout::is_size_align_valid(size, align)
);
// SAFETY: the caller is required to uphold the preconditions.
unsafe { Layout { size, align: Alignment::new_unchecked(align) } }
}

2
library/core/src/result.rs
View File

@ -1481,7 +1481,6 @@ pub fn unwrap_or_else<F: FnOnce(E) -> T>(self, op: F) -> T {
#[track_caller]
#[stable(feature = "option_result_unwrap_unchecked", since = "1.58.0")]
pub unsafe fn unwrap_unchecked(self) -> T {
debug_assert!(self.is_ok());
match self {
Ok(t) => t,
// SAFETY: the safety contract must be upheld by the caller.
@ -1513,7 +1512,6 @@ pub unsafe fn unwrap_unchecked(self) -> T {
#[track_caller]
#[stable(feature = "option_result_unwrap_unchecked", since = "1.58.0")]
pub unsafe fn unwrap_err_unchecked(self) -> E {
debug_assert!(self.is_err());
match self {
// SAFETY: the safety contract must be upheld by the caller.
Ok(_) => unsafe { hint::unreachable_unchecked() },