From 2f04a793ae0b9331f6d853a971a670c8ea99b0b7 Mon Sep 17 00:00:00 2001
From: Waffle <waffle.lapkin@gmail.com>
Date: Sat, 27 Feb 2021 00:20:46 +0300
Subject: Revert `Vec::spare_capacity_mut` impl to prevent pointers
 invalidation

---
 library/alloc/src/vec/mod.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

(limited to 'library/alloc/src/vec')

diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index b1b26194283..e5545d2a77f 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -1879,7 +1879,15 @@ impl<T, A: Allocator> Vec<T, A> {
     #[unstable(feature = "vec_spare_capacity", issue = "75017")]
     #[inline]
     pub fn spare_capacity_mut(&mut self) -> &mut [MaybeUninit<T>] {
-        self.split_at_spare_mut().1
+        // Note:
+        // This method is not implemented in terms of `split_at_spare_mut`,
+        // to prevent invalidation of pointers to the buffer.
+        unsafe {
+            slice::from_raw_parts_mut(
+                self.as_mut_ptr().add(self.len) as *mut MaybeUninit<T>,
+                self.buf.capacity() - self.len,
+            )
+        }
     }
 
     /// Returns vector content as a slice of `T`, along with the remaining spare
-- 
cgit 1.4.1-3-g733a5