4 files changed, 24 insertions, 8 deletions
diff --git a/library/alloc/src/boxed/thin.rs b/library/alloc/src/boxed/thin.rs
index 21425b9846e..1cce36606d2 100644
--- a/library/alloc/src/boxed/thin.rs
+++ b/library/alloc/src/boxed/thin.rs
@@ -5,7 +5,7 @@
 use core::error::Error;
 use core::fmt::{self, Debug, Display, Formatter};
 #[cfg(not(no_global_oom_handling))]
-use core::intrinsics::const_allocate;
+use core::intrinsics::{const_allocate, const_make_global};
 use core::marker::PhantomData;
 #[cfg(not(no_global_oom_handling))]
 use core::marker::Unsize;
@@ -340,9 +340,10 @@ impl<H> WithHeader<H> {
                     alloc.add(metadata_offset).cast();
                 // SAFETY: `*metadata_ptr` is within the allocation.
                 metadata_ptr.write(ptr::metadata::<Dyn>(ptr::dangling::<T>() as *const Dyn));
-
+                // SAFETY: valid heap allocation
+                const_make_global(alloc);
                 // SAFETY: we have just written the metadata.
-                &*(metadata_ptr)
+                &*metadata_ptr
             }
         };
 
diff --git a/library/alloc/src/fmt.rs b/library/alloc/src/fmt.rs
index 30f42050ac8..d0ba9c39886 100644
--- a/library/alloc/src/fmt.rs
+++ b/library/alloc/src/fmt.rs
@@ -348,13 +348,13 @@
 //! format := '{' [ argument ] [ ':' format_spec ] [ ws ] * '}'
 //! argument := integer | identifier
 //!
-//! format_spec := [[fill]align][sign]['#']['0'][width]['.' precision]type
+//! format_spec := [[fill]align][sign]['#']['0'][width]['.' precision][type]
 //! fill := character
 //! align := '<' | '^' | '>'
 //! sign := '+' | '-'
 //! width := count
 //! precision := count | '*'
-//! type := '' | '?' | 'x?' | 'X?' | identifier
+//! type := '?' | 'x?' | 'X?' | identifier
 //! count := parameter | integer
 //! parameter := argument '$'
 //! ```
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 4ad65e678c3..6b6e4df4cba 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -155,6 +155,7 @@
 #![feature(try_trait_v2)]
 #![feature(try_with_capacity)]
 #![feature(tuple_trait)]
+#![feature(ub_checks)]
 #![feature(unicode_internals)]
 #![feature(unsize)]
 #![feature(unwrap_infallible)]
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 1df6ab672ea..9856e9c18ec 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -64,7 +64,7 @@ use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
 use core::ops::{self, Index, IndexMut, Range, RangeBounds};
 use core::ptr::{self, NonNull};
 use core::slice::{self, SliceIndex};
-use core::{fmt, intrinsics};
+use core::{fmt, intrinsics, ub_checks};
 
 #[stable(feature = "extract_if", since = "1.87.0")]
 pub use self::extract_if::ExtractIf;
@@ -1058,6 +1058,11 @@ impl<T, A: Allocator> Vec<T, A> {
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self {
+        ub_checks::assert_unsafe_precondition!(
+            check_library_ub,
+            "Vec::from_raw_parts_in requires that length <= capacity",
+            (length: usize = length, capacity: usize = capacity) => length <= capacity
+        );
         unsafe { Vec { buf: RawVec::from_raw_parts_in(ptr, capacity, alloc), len: length } }
     }
 
@@ -1174,6 +1179,11 @@ impl<T, A: Allocator> Vec<T, A> {
     #[unstable(feature = "allocator_api", reason = "new API", issue = "32838")]
     // #[unstable(feature = "box_vec_non_null", issue = "130364")]
     pub unsafe fn from_parts_in(ptr: NonNull<T>, length: usize, capacity: usize, alloc: A) -> Self {
+        ub_checks::assert_unsafe_precondition!(
+            check_library_ub,
+            "Vec::from_parts_in requires that length <= capacity",
+            (length: usize = length, capacity: usize = capacity) => length <= capacity
+        );
         unsafe { Vec { buf: RawVec::from_nonnull_in(ptr, capacity, alloc), len: length } }
     }
 
@@ -1950,7 +1960,11 @@ impl<T, A: Allocator> Vec<T, A> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub unsafe fn set_len(&mut self, new_len: usize) {
-        debug_assert!(new_len <= self.capacity());
+        ub_checks::assert_unsafe_precondition!(
+            check_library_ub,
+            "Vec::set_len requires that new_len <= capacity()",
+            (new_len: usize = new_len, capacity: usize = self.capacity()) => new_len <= capacity
+        );
 
         self.len = new_len;
     }
@@ -3695,7 +3709,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// This is optimal if:
     ///
     /// * The tail (elements in the vector after `range`) is empty,
-    /// * or `replace_with` yields fewer or equal elements than `range`’s length
+    /// * or `replace_with` yields fewer or equal elements than `range`'s length
     /// * or the lower bound of its `size_hint()` is exact.
     ///
     /// Otherwise, a temporary vector is allocated and the tail is moved twice.