bjoernager/rust
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Clarify the text of some comments

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Scott McMurray 2023-03-12 16:30:51 -07:00
parent f6a57c1955
commit e97505704e
1 changed files with 5 additions and 1 deletions
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6
library/core/src/option.rs
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@ -745,6 +745,9 @@ impl<T> Option<T> {
/// It's guaranteed to be a multiple of alignment (so will always give a /// It's guaranteed to be a multiple of alignment (so will always give a
/// correctly-aligned location) and to be within the allocated object, so /// correctly-aligned location) and to be within the allocated object, so
/// is valid to use with `offset` and to use for a zero-sized read. /// is valid to use with `offset` and to use for a zero-sized read.
///
/// FIXME: This is a horrible hack, but allows a nice optimization. It should
/// be replaced with `offset_of!` once that works on enum variants.
const SOME_BYTE_OFFSET_GUESS: isize = { const SOME_BYTE_OFFSET_GUESS: isize = {
let some_uninit = Some(mem::MaybeUninit::<T>::uninit()); let some_uninit = Some(mem::MaybeUninit::<T>::uninit());
let payload_ref = some_uninit.as_ref().unwrap(); let payload_ref = some_uninit.as_ref().unwrap();
@ -762,7 +765,8 @@ impl<T> Option<T> {
let max_offset = mem::size_of::<Self>() - mem::size_of::<T>(); let max_offset = mem::size_of::<Self>() - mem::size_of::<T>();
if offset as usize <= max_offset { if offset as usize <= max_offset {
// The offset is at least inside the object, so let's try it. // There's enough space after this offset for a `T` to exist without
// overflowing the bounds of the object, so let's try it.
offset offset
} else { } else {
// The offset guess is definitely wrong, so use the address // The offset guess is definitely wrong, so use the address