PhantomData layout guarantees

rust-lang · Nov 7, 2022 · 72a9029 · 72a9029
1 parent 7eef946
commit 72a9029
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
@@ -621,6 +621,12 @@ 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")]