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Document unsafety for *const T and *mut T #71760

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Merged
merged 1 commit into from
May 2, 2020
Merged

Document unsafety for *const T and *mut T #71760

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6 changes: 4 additions & 2 deletions src/libcore/ptr/const_ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,6 @@ use crate::cmp::Ordering::{self, Equal, Greater, Less};
use crate::intrinsics;
use crate::mem;

// ignore-tidy-undocumented-unsafe

#[lang = "const_ptr"]
impl<T: ?Sized> *const T {
/// Returns `true` if the pointer is null.
Expand Down Expand Up @@ -215,6 +213,7 @@ impl<T: ?Sized> *const T {
where
T: Sized,
{
// SAFETY: the `arith_offset` intrinsic has no prerequisites to be called.
unsafe { intrinsics::arith_offset(self, count) }
}

Expand Down Expand Up @@ -702,6 +701,7 @@ impl<T: ?Sized> *const T {
if !align.is_power_of_two() {
panic!("align_offset: align is not a power-of-two");
}
// SAFETY: `align` has been checked to be a power of 2 above
unsafe { align_offset(self, align) }
}
}
Expand Down Expand Up @@ -729,6 +729,8 @@ impl<T> *const [T] {
#[unstable(feature = "slice_ptr_len", issue = "71146")]
#[rustc_const_unstable(feature = "const_slice_ptr_len", issue = "71146")]
pub const fn len(self) -> usize {
// SAFETY: this is safe because `*const [T]` and `FatPtr<T>` have the same layout.
// Only `std` can make this guarantee.
unsafe { Repr { rust: self }.raw }.len
}
}
Expand Down
6 changes: 4 additions & 2 deletions src/libcore/ptr/mut_ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,6 @@ use super::*;
use crate::cmp::Ordering::{self, Equal, Greater, Less};
use crate::intrinsics;

// ignore-tidy-undocumented-unsafe

#[lang = "mut_ptr"]
impl<T: ?Sized> *mut T {
/// Returns `true` if the pointer is null.
Expand Down Expand Up @@ -208,6 +206,7 @@ impl<T: ?Sized> *mut T {
where
T: Sized,
{
// SAFETY: the `arith_offset` intrinsic has no prerequisites to be called.
unsafe { intrinsics::arith_offset(self, count) as *mut T }
}

Expand Down Expand Up @@ -890,6 +889,7 @@ impl<T: ?Sized> *mut T {
if !align.is_power_of_two() {
panic!("align_offset: align is not a power-of-two");
}
// SAFETY: `align` has been checked to be a power of 2 above
unsafe { align_offset(self, align) }
}
}
Expand Down Expand Up @@ -917,6 +917,8 @@ impl<T> *mut [T] {
#[unstable(feature = "slice_ptr_len", issue = "71146")]
#[rustc_const_unstable(feature = "const_slice_ptr_len", issue = "71146")]
pub const fn len(self) -> usize {
// SAFETY: this is safe because `*const [T]` and `FatPtr<T>` have the same layout.
// Only `std` can make this guarantee.
unsafe { Repr { rust_mut: self }.raw }.len
}
}
Expand Down