impl CloneToUninit for Path and OsStr

2 files changed, 29 insertions, 0 deletions

diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index a501bcc98cf..f68ea3c562a 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -3,10 +3,13 @@
 #[cfg(test)]
 mod tests;
 
+use core::clone::CloneToUninit;
+
 use crate::borrow::{Borrow, Cow};
 use crate::collections::TryReserveError;
 use crate::hash::{Hash, Hasher};
 use crate::ops::{self, Range};
+use crate::ptr::addr_of_mut;
 use crate::rc::Rc;
 use crate::str::FromStr;
 use crate::sync::Arc;
@@ -1261,6 +1264,15 @@ impl Clone for Box<OsStr> {
     }
 }
 
+#[unstable(feature = "clone_to_uninit", issue = "126799")]
+unsafe impl CloneToUninit for OsStr {
+    #[cfg_attr(debug_assertions, track_caller)]
+    unsafe fn clone_to_uninit(&self, dst: *mut Self) {
+        // SAFETY: we're just a wrapper around a platform-specific Slice
+        unsafe { self.inner.clone_to_uninit(addr_of_mut!((*dst).inner)) }
+    }
+}
+
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl From<OsString> for Arc<OsStr> {
     /// Converts an [`OsString`] into an <code>[Arc]<[OsStr]></code> by moving the [`OsString`]
diff --git a/library/std/src/ffi/os_str/tests.rs b/library/std/src/ffi/os_str/tests.rs
index 5b39b9e34d8..67147934b4d 100644
--- a/library/std/src/ffi/os_str/tests.rs
+++ b/library/std/src/ffi/os_str/tests.rs
@@ -1,4 +1,6 @@
 use super::*;
+use crate::mem::MaybeUninit;
+use crate::ptr;
 
 #[test]
 fn test_os_string_with_capacity() {
@@ -286,3 +288,18 @@ fn slice_surrogate_edge() {
     assert_eq!(post_crab.slice_encoded_bytes(..4), "🦀");
     assert_eq!(post_crab.slice_encoded_bytes(4..), surrogate);
 }
+
+#[test]
+fn clone_to_uninit() {
+    let a = OsStr::new("hello.txt");
+
+    let mut storage = vec![MaybeUninit::<u8>::uninit(); size_of_val::<OsStr>(a)];
+    unsafe { a.clone_to_uninit(ptr::from_mut::<[_]>(storage.as_mut_slice()) as *mut OsStr) };
+    assert_eq!(a.as_encoded_bytes(), unsafe { MaybeUninit::slice_assume_init_ref(&storage) });
+
+    let mut b: Box<OsStr> = OsStr::new("world.exe").into();
+    assert_eq!(size_of_val::<OsStr>(a), size_of_val::<OsStr>(&b));
+    assert_ne!(a, &*b);
+    unsafe { a.clone_to_uninit(ptr::from_mut::<OsStr>(&mut b)) };
+    assert_eq!(a, &*b);
+}