Rollup merge of #104081 - joshlf:patch-6, r=dtolnay

PhantomData layout guarantees
rust-lang · Jan 7, 2023 · 08653c8 · 08653c8
2 parents 405e48f + 72a9029
commit 08653c8
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
@@ -623,6 +623,12 @@ impl<T: ?Sized> !Sync for *mut T {}
 /// (ideally) or `PhantomData<*const T>` (if no lifetime applies), so
 /// as not to indicate ownership.
 ///
+/// ## Layout
+///
+/// For all `T`, the following are guaranteed:
+/// * `size_of::<PhantomData<T>>() == 0`
+/// * `align_of::<PhantomData<T>>() == 1`
+///
 /// [drop check]: ../../nomicon/dropck.html
 #[lang = "phantom_data"]
 #[stable(feature = "rust1", since = "1.0.0")]