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Rollup merge of #75943 - elichai:2020-align_offset-docs, r=RalfJung

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Fix potential UB in align_offset doc examples

Currently it takes a pointer only to the first element in the array, this changes the code to take a pointer to the whole array.
miri can't catch this right now because it later calls `x.len()` which re-tags the pointer for the whole array.

https://github.com/rust-lang/miri/issues/1526#issuecomment-680897144
This commit is contained in:
Pietro Albini 2020-08-28 10:23:59 +02:00 committed by GitHub
commit be1b304ea4
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2 changed files with 2 additions and 2 deletions
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2
library/core/src/ptr/const_ptr.rs
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@ -836,7 +836,7 @@ impl<T: ?Sized> *const T {
/// # use std::mem::align_of;
/// # unsafe {
/// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
/// let ptr = &x[n] as *const u8;
/// let ptr = x.as_ptr().add(n) as *const u8;
/// let offset = ptr.align_offset(align_of::<u16>());
/// if offset < x.len() - n - 1 {
/// let u16_ptr = ptr.add(offset) as *const u16;

2
library/core/src/ptr/mut_ptr.rs
View File

@ -1094,7 +1094,7 @@ impl<T: ?Sized> *mut T {
/// # use std::mem::align_of;
/// # unsafe {
/// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
/// let ptr = &x[n] as *const u8;
/// let ptr = x.as_ptr().add(n) as *const u8;
/// let offset = ptr.align_offset(align_of::<u16>());
/// if offset < x.len() - n - 1 {
/// let u16_ptr = ptr.add(offset) as *const u16;