Skip to content
Permalink
Browse files

ManuallyDrop != MaybeUninit

  • Loading branch information...
RalfJung committed Feb 27, 2019
1 parent f5b5f92 commit 4e7d4c7778a00371ba707fb8f9022bcbb443bb29
Showing with 8 additions and 0 deletions.
  1. +8 −0 src/libcore/mem.rs
@@ -900,10 +900,16 @@ pub fn discriminant<T>(v: &T) -> Discriminant<T> {
}
}

// FIXME: Reference `MaybeUninit` from these docs, once that is stable.
/// A wrapper to inhibit compiler from automatically calling `T`’s destructor.
///
/// This wrapper is 0-cost.
///
/// `ManuallyDrop<T>` is subject to the same layout optimizations as `T`.
/// As a consequence, it has *no effect* on the assumptions that the compiler makes
/// about all values being initialized at their type. In particular, initializing
/// a `ManuallyDrop<&T>` with [`mem::zeroed`] is undefined behavior.
///
/// # Examples
///
/// This wrapper helps with explicitly documenting the drop order dependencies between fields of
@@ -935,6 +941,8 @@ pub fn discriminant<T>(v: &T) -> Discriminant<T> {
/// }
/// }
/// ```
///
/// [`mem::zeroed']: fn.zeroed.html
#[stable(feature = "manually_drop", since = "1.20.0")]
#[lang = "manually_drop"]
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]

0 comments on commit 4e7d4c7

Please sign in to comment.
You can’t perform that action at this time.