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-rw-r--r--library/alloc/src/alloc.rs4
-rw-r--r--library/alloc/src/boxed.rs33
-rw-r--r--library/alloc/src/collections/btree/map.rs15
-rw-r--r--library/alloc/src/collections/btree/node.rs17
-rw-r--r--library/alloc/src/collections/btree/set.rs10
-rw-r--r--library/alloc/src/collections/vec_deque/mod.rs27
-rw-r--r--library/alloc/src/collections/vec_deque/spec_extend.rs6
-rw-r--r--library/alloc/src/collections/vec_deque/spec_from_iter.rs1
-rw-r--r--library/alloc/src/ffi/c_str.rs7
-rw-r--r--library/alloc/src/lib.rs10
-rw-r--r--library/alloc/src/raw_vec/mod.rs168
-rw-r--r--library/alloc/src/raw_vec/tests.rs10
-rw-r--r--library/alloc/src/rc.rs15
-rw-r--r--library/alloc/src/string.rs13
-rw-r--r--library/alloc/src/sync.rs27
-rw-r--r--library/alloc/src/vec/cow.rs1
-rw-r--r--library/alloc/src/vec/extract_if.rs64
-rw-r--r--library/alloc/src/vec/in_place_collect.rs2
-rw-r--r--library/alloc/src/vec/mod.rs78
-rw-r--r--library/alloc/src/vec/spec_extend.rs6
-rw-r--r--library/alloc/src/vec/spec_from_elem.rs4
-rw-r--r--library/alloc/src/vec/spec_from_iter.rs2
-rw-r--r--library/alloc/src/vec/spec_from_iter_nested.rs2
-rw-r--r--library/alloc/src/vec/splice.rs2
24 files changed, 275 insertions, 249 deletions
diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 76630a746dd..65c8206e9d4 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -408,12 +408,12 @@ pub const fn handle_alloc_error(layout: Layout) -> ! {
         }
     }
 
-    #[cfg(not(feature = "panic_immediate_abort"))]
+    #[cfg(not(panic = "immediate-abort"))]
     {
         core::intrinsics::const_eval_select((layout,), ct_error, rt_error)
     }
 
-    #[cfg(feature = "panic_immediate_abort")]
+    #[cfg(panic = "immediate-abort")]
     ct_error(layout)
 }
 
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 1c549f7b6ba..49ff768bed1 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -619,6 +619,37 @@ impl<T, A: Allocator> Box<T, A> {
     pub fn into_inner(boxed: Self) -> T {
         *boxed
     }
+
+    /// Consumes the `Box` without consuming its allocation, returning the wrapped value and a `Box`
+    /// to the uninitialized memory where the wrapped value used to live.
+    ///
+    /// This can be used together with [`write`](Box::write) to reuse the allocation for multiple
+    /// boxed values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(box_take)]
+    ///
+    /// let c = Box::new(5);
+    ///
+    /// // take the value out of the box
+    /// let (value, uninit) = Box::take(c);
+    /// assert_eq!(value, 5);
+    ///
+    /// // reuse the box for a second value
+    /// let c = Box::write(uninit, 6);
+    /// assert_eq!(*c, 6);
+    /// ```
+    #[unstable(feature = "box_take", issue = "147212")]
+    pub fn take(boxed: Self) -> (T, Box<mem::MaybeUninit<T>, A>) {
+        unsafe {
+            let (raw, alloc) = Box::into_raw_with_allocator(boxed);
+            let value = raw.read();
+            let uninit = Box::from_raw_in(raw.cast::<mem::MaybeUninit<T>>(), alloc);
+            (value, uninit)
+        }
+    }
 }
 
 impl<T> Box<[T]> {
@@ -1706,7 +1737,7 @@ impl Default for Box<str> {
 }
 
 #[cfg(not(no_global_oom_handling))]
-#[stable(feature = "pin_default_impls", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "pin_default_impls", since = "1.91.0")]
 impl<T> Default for Pin<Box<T>>
 where
     T: ?Sized,
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index cebd25c6039..adcb444d08c 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -194,6 +194,9 @@ pub struct BTreeMap<
     root: Option<Root<K, V>>,
     length: usize,
     /// `ManuallyDrop` to control drop order (needs to be dropped after all the nodes).
+    // Although some of the accessory types store a copy of the allocator, the nodes do not.
+    // Because allocations will remain live as long as any copy (like this one) of the allocator
+    // is live, it's unnecessary to store the allocator in each node.
     pub(super) alloc: ManuallyDrop<A>,
     // For dropck; the `Box` avoids making the `Unpin` impl more strict than before
     _marker: PhantomData<crate::boxed::Box<(K, V), A>>,
@@ -1453,7 +1456,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
     /// assert_eq!(low.keys().copied().collect::<Vec<_>>(), [0, 1, 2, 3]);
     /// assert_eq!(high.keys().copied().collect::<Vec<_>>(), [4, 5, 6, 7]);
     /// ```
-    #[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+    #[stable(feature = "btree_extract_if", since = "1.91.0")]
     pub fn extract_if<F, R>(&mut self, range: R, pred: F) -> ExtractIf<'_, K, V, R, F, A>
     where
         K: Ord,
@@ -1940,7 +1943,7 @@ impl<K, V> Default for Values<'_, K, V> {
 }
 
 /// An iterator produced by calling `extract_if` on BTreeMap.
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct ExtractIf<
     'a,
@@ -1973,7 +1976,7 @@ pub(super) struct ExtractIfInner<'a, K, V, R> {
     range: R,
 }
 
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 impl<K, V, R, F, A> fmt::Debug for ExtractIf<'_, K, V, R, F, A>
 where
     K: fmt::Debug,
@@ -1985,7 +1988,7 @@ where
     }
 }
 
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 impl<K, V, R, F, A: Allocator + Clone> Iterator for ExtractIf<'_, K, V, R, F, A>
 where
     K: PartialOrd,
@@ -2059,7 +2062,7 @@ impl<'a, K, V, R> ExtractIfInner<'a, K, V, R> {
     }
 }
 
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 impl<K, V, R, F> FusedIterator for ExtractIf<'_, K, V, R, F>
 where
     K: PartialOrd,
@@ -2410,7 +2413,7 @@ impl<K, V> Default for BTreeMap<K, V> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<K: PartialEq, V: PartialEq, A: Allocator + Clone> PartialEq for BTreeMap<K, V, A> {
     fn eq(&self, other: &BTreeMap<K, V, A>) -> bool {
-        self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
+        self.iter().eq(other)
     }
 }
 
diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs
index b233e1740b7..a87259e7c58 100644
--- a/library/alloc/src/collections/btree/node.rs
+++ b/library/alloc/src/collections/btree/node.rs
@@ -117,10 +117,11 @@ impl<K, V> InternalNode<K, V> {
     /// initialized and valid edge. This function does not set up
     /// such an edge.
     unsafe fn new<A: Allocator + Clone>(alloc: A) -> Box<Self, A> {
+        let mut node = Box::<Self, _>::new_uninit_in(alloc);
         unsafe {
-            let mut node = Box::<Self, _>::new_uninit_in(alloc);
-            // We only need to initialize the data; the edges are MaybeUninit.
+            // SAFETY: argument points to the `node.data` `LeafNode`
             LeafNode::init(&raw mut (*node.as_mut_ptr()).data);
+            // SAFETY: `node.data` was just initialized and `node.edges` is MaybeUninit.
             node.assume_init()
         }
     }
@@ -224,7 +225,11 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::Leaf> {
     }
 
     fn from_new_leaf<A: Allocator + Clone>(leaf: Box<LeafNode<K, V>, A>) -> Self {
-        NodeRef { height: 0, node: NonNull::from(Box::leak(leaf)), _marker: PhantomData }
+        // The allocator must be dropped, not leaked.  See also `BTreeMap::alloc`.
+        let (leaf, _alloc) = Box::into_raw_with_allocator(leaf);
+        // SAFETY: the node was just allocated.
+        let node = unsafe { NonNull::new_unchecked(leaf) };
+        NodeRef { height: 0, node, _marker: PhantomData }
     }
 }
 
@@ -242,7 +247,11 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::Internal> {
         height: usize,
     ) -> Self {
         debug_assert!(height > 0);
-        let node = NonNull::from(Box::leak(internal)).cast();
+        // The allocator must be dropped, not leaked.  See also `BTreeMap::alloc`.
+        let (internal, _alloc) = Box::into_raw_with_allocator(internal);
+        // SAFETY: the node was just allocated.
+        let internal = unsafe { NonNull::new_unchecked(internal) };
+        let node = internal.cast();
         let mut this = NodeRef { height, node, _marker: PhantomData };
         this.borrow_mut().correct_all_childrens_parent_links();
         this
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index e6b0a1f6323..6e6996bcbd6 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -1218,7 +1218,7 @@ impl<T, A: Allocator + Clone> BTreeSet<T, A> {
     /// assert_eq!(low.into_iter().collect::<Vec<_>>(), [0, 1, 2, 3]);
     /// assert_eq!(high.into_iter().collect::<Vec<_>>(), [4, 5, 6, 7]);
     /// ```
-    #[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+    #[stable(feature = "btree_extract_if", since = "1.91.0")]
     pub fn extract_if<F, R>(&mut self, range: R, pred: F) -> ExtractIf<'_, T, R, F, A>
     where
         T: Ord,
@@ -1553,7 +1553,7 @@ impl<'a, T, A: Allocator + Clone> IntoIterator for &'a BTreeSet<T, A> {
 }
 
 /// An iterator produced by calling `extract_if` on BTreeSet.
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 pub struct ExtractIf<
     'a,
@@ -1568,7 +1568,7 @@ pub struct ExtractIf<
     alloc: A,
 }
 
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 impl<T, R, F, A> fmt::Debug for ExtractIf<'_, T, R, F, A>
 where
     T: fmt::Debug,
@@ -1581,7 +1581,7 @@ where
     }
 }
 
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 impl<T, R, F, A: Allocator + Clone> Iterator for ExtractIf<'_, T, R, F, A>
 where
     T: PartialOrd,
@@ -1601,7 +1601,7 @@ where
     }
 }
 
-#[stable(feature = "btree_extract_if", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "btree_extract_if", since = "1.91.0")]
 impl<T, R, F, A: Allocator + Clone> FusedIterator for ExtractIf<'_, T, R, F, A>
 where
     T: PartialOrd,
diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs
index d589860524b..ac619a42d35 100644
--- a/library/alloc/src/collections/vec_deque/mod.rs
+++ b/library/alloc/src/collections/vec_deque/mod.rs
@@ -103,7 +103,6 @@ pub struct VecDeque<
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Clone, A: Allocator + Clone> Clone for VecDeque<T, A> {
-    #[track_caller]
     fn clone(&self) -> Self {
         let mut deq = Self::with_capacity_in(self.len(), self.allocator().clone());
         deq.extend(self.iter().cloned());
@@ -114,7 +113,6 @@ impl<T: Clone, A: Allocator + Clone> Clone for VecDeque<T, A> {
     ///
     /// This method is preferred over simply assigning `source.clone()` to `self`,
     /// as it avoids reallocation if possible.
-    #[track_caller]
     fn clone_from(&mut self, source: &Self) {
         self.clear();
         self.extend(source.iter().cloned());
@@ -577,7 +575,6 @@ impl<T> VecDeque<T> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
-    #[track_caller]
     pub fn with_capacity(capacity: usize) -> VecDeque<T> {
         Self::with_capacity_in(capacity, Global)
     }
@@ -633,7 +630,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// let deque: VecDeque<u32> = VecDeque::with_capacity(10);
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[track_caller]
     pub fn with_capacity_in(capacity: usize, alloc: A) -> VecDeque<T, A> {
         VecDeque { head: 0, len: 0, buf: RawVec::with_capacity_in(capacity, alloc) }
     }
@@ -799,7 +795,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     ///
     /// [`reserve`]: VecDeque::reserve
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     pub fn reserve_exact(&mut self, additional: usize) {
         let new_cap = self.len.checked_add(additional).expect("capacity overflow");
         let old_cap = self.capacity();
@@ -830,7 +825,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[cfg_attr(not(test), rustc_diagnostic_item = "vecdeque_reserve")]
-    #[track_caller]
     pub fn reserve(&mut self, additional: usize) {
         let new_cap = self.len.checked_add(additional).expect("capacity overflow");
         let old_cap = self.capacity();
@@ -962,7 +956,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert!(buf.capacity() >= 4);
     /// ```
     #[stable(feature = "deque_extras_15", since = "1.5.0")]
-    #[track_caller]
     pub fn shrink_to_fit(&mut self) {
         self.shrink_to(0);
     }
@@ -988,7 +981,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert!(buf.capacity() >= 4);
     /// ```
     #[stable(feature = "shrink_to", since = "1.56.0")]
-    #[track_caller]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         let target_cap = min_capacity.max(self.len);
 
@@ -1891,7 +1883,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(d.front(), Some(&2));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     pub fn push_front(&mut self, value: T) {
         let _ = self.push_front_mut(value);
     }
@@ -1910,7 +1901,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(d.front(), Some(&7));
     /// ```
     #[unstable(feature = "push_mut", issue = "135974")]
-    #[track_caller]
     #[must_use = "if you don't need a reference to the value, use `VecDeque::push_front` instead"]
     pub fn push_front_mut(&mut self, value: T) -> &mut T {
         if self.is_full() {
@@ -1937,7 +1927,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_confusables("push", "put", "append")]
-    #[track_caller]
     pub fn push_back(&mut self, value: T) {
         let _ = self.push_back_mut(value);
     }
@@ -1956,7 +1945,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(d.back(), Some(&10));
     /// ```
     #[unstable(feature = "push_mut", issue = "135974")]
-    #[track_caller]
     #[must_use = "if you don't need a reference to the value, use `VecDeque::push_back` instead"]
     pub fn push_back_mut(&mut self, value: T) -> &mut T {
         if self.is_full() {
@@ -2071,7 +2059,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(vec_deque, &['a', 'd', 'b', 'c', 'e']);
     /// ```
     #[stable(feature = "deque_extras_15", since = "1.5.0")]
-    #[track_caller]
     pub fn insert(&mut self, index: usize, value: T) {
         let _ = self.insert_mut(index, value);
     }
@@ -2099,7 +2086,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(vec_deque, &[1, 12, 2, 3]);
     /// ```
     #[unstable(feature = "push_mut", issue = "135974")]
-    #[track_caller]
     #[must_use = "if you don't need a reference to the value, use `VecDeque::insert` instead"]
     pub fn insert_mut(&mut self, index: usize, value: T) -> &mut T {
         assert!(index <= self.len(), "index out of bounds");
@@ -2205,7 +2191,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     #[inline]
     #[must_use = "use `.truncate()` if you don't need the other half"]
     #[stable(feature = "split_off", since = "1.4.0")]
-    #[track_caller]
     pub fn split_off(&mut self, at: usize) -> Self
     where
         A: Clone,
@@ -2272,7 +2257,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// ```
     #[inline]
     #[stable(feature = "append", since = "1.4.0")]
-    #[track_caller]
     pub fn append(&mut self, other: &mut Self) {
         if T::IS_ZST {
             self.len = self.len.checked_add(other.len).expect("capacity overflow");
@@ -2395,7 +2379,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     // be called in cold paths.
     // This may panic or abort
     #[inline(never)]
-    #[track_caller]
     fn grow(&mut self) {
         // Extend or possibly remove this assertion when valid use-cases for growing the
         // buffer without it being full emerge
@@ -2434,7 +2417,6 @@ impl<T, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(buf, [5, 10, 101, 102, 103]);
     /// ```
     #[stable(feature = "vec_resize_with", since = "1.33.0")]
-    #[track_caller]
     pub fn resize_with(&mut self, new_len: usize, generator: impl FnMut() -> T) {
         let len = self.len;
 
@@ -2981,7 +2963,6 @@ impl<T: Clone, A: Allocator> VecDeque<T, A> {
     /// assert_eq!(buf, [5, 10, 20, 20, 20]);
     /// ```
     #[stable(feature = "deque_extras", since = "1.16.0")]
-    #[track_caller]
     pub fn resize(&mut self, new_len: usize, value: T) {
         if new_len > self.len() {
             let extra = new_len - self.len();
@@ -3101,7 +3082,6 @@ impl<T, A: Allocator> IndexMut<usize> for VecDeque<T, A> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> FromIterator<T> for VecDeque<T> {
-    #[track_caller]
     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> VecDeque<T> {
         SpecFromIter::spec_from_iter(iter.into_iter())
     }
@@ -3141,19 +3121,16 @@ impl<'a, T, A: Allocator> IntoIterator for &'a mut VecDeque<T, A> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, A: Allocator> Extend<T> for VecDeque<T, A> {
-    #[track_caller]
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
         <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter());
     }
 
     #[inline]
-    #[track_caller]
     fn extend_one(&mut self, elem: T) {
         self.push_back(elem);
     }
 
     #[inline]
-    #[track_caller]
     fn extend_reserve(&mut self, additional: usize) {
         self.reserve(additional);
     }
@@ -3169,19 +3146,16 @@ impl<T, A: Allocator> Extend<T> for VecDeque<T, A> {
 
 #[stable(feature = "extend_ref", since = "1.2.0")]
 impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for VecDeque<T, A> {
-    #[track_caller]
     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
         self.spec_extend(iter.into_iter());
     }
 
     #[inline]
-    #[track_caller]
     fn extend_one(&mut self, &elem: &'a T) {
         self.push_back(elem);
     }
 
     #[inline]
-    #[track_caller]
     fn extend_reserve(&mut self, additional: usize) {
         self.reserve(additional);
     }
@@ -3279,7 +3253,6 @@ impl<T, const N: usize> From<[T; N]> for VecDeque<T> {
     /// let deq2: VecDeque<_> = [1, 2, 3, 4].into();
     /// assert_eq!(deq1, deq2);
     /// ```
-    #[track_caller]
     fn from(arr: [T; N]) -> Self {
         let mut deq = VecDeque::with_capacity(N);
         let arr = ManuallyDrop::new(arr);
diff --git a/library/alloc/src/collections/vec_deque/spec_extend.rs b/library/alloc/src/collections/vec_deque/spec_extend.rs
index 7c7072c4c3a..6c2199135e0 100644
--- a/library/alloc/src/collections/vec_deque/spec_extend.rs
+++ b/library/alloc/src/collections/vec_deque/spec_extend.rs
@@ -8,7 +8,6 @@ use crate::vec;
 
 // Specialization trait used for VecDeque::extend
 pub(super) trait SpecExtend<T, I> {
-    #[track_caller]
     fn spec_extend(&mut self, iter: I);
 }
 
@@ -16,7 +15,6 @@ impl<T, I, A: Allocator> SpecExtend<T, I> for VecDeque<T, A>
 where
     I: Iterator<Item = T>,
 {
-    #[track_caller]
     default fn spec_extend(&mut self, mut iter: I) {
         // This function should be the moral equivalent of:
         //
@@ -47,7 +45,6 @@ impl<T, I, A: Allocator> SpecExtend<T, I> for VecDeque<T, A>
 where
     I: TrustedLen<Item = T>,
 {
-    #[track_caller]
     default fn spec_extend(&mut self, iter: I) {
         // This is the case for a TrustedLen iterator.
         let (low, high) = iter.size_hint();
@@ -81,7 +78,6 @@ where
 
 #[cfg(not(test))]
 impl<T, A: Allocator> SpecExtend<T, vec::IntoIter<T>> for VecDeque<T, A> {
-    #[track_caller]
     fn spec_extend(&mut self, mut iterator: vec::IntoIter<T>) {
         let slice = iterator.as_slice();
         self.reserve(slice.len());
@@ -99,7 +95,6 @@ where
     I: Iterator<Item = &'a T>,
     T: Copy,
 {
-    #[track_caller]
     default fn spec_extend(&mut self, iterator: I) {
         self.spec_extend(iterator.copied())
     }
@@ -109,7 +104,6 @@ impl<'a, T: 'a, A: Allocator> SpecExtend<&'a T, slice::Iter<'a, T>> for VecDeque
 where
     T: Copy,
 {
-    #[track_caller]
     fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
         let slice = iterator.as_slice();
         self.reserve(slice.len());
diff --git a/library/alloc/src/collections/vec_deque/spec_from_iter.rs b/library/alloc/src/collections/vec_deque/spec_from_iter.rs
index c80a30c2103..557666ea3b8 100644
--- a/library/alloc/src/collections/vec_deque/spec_from_iter.rs
+++ b/library/alloc/src/collections/vec_deque/spec_from_iter.rs
@@ -9,7 +9,6 @@ impl<T, I> SpecFromIter<T, I> for VecDeque<T>
 where
     I: Iterator<Item = T>,
 {
-    #[track_caller]
     default fn spec_from_iter(iterator: I) -> Self {
         // Since converting is O(1) now, just re-use the `Vec` logic for
         // anything where we can't do something extra-special for `VecDeque`,
diff --git a/library/alloc/src/ffi/c_str.rs b/library/alloc/src/ffi/c_str.rs
index b0c8c4b1ca4..3e78d680ea6 100644
--- a/library/alloc/src/ffi/c_str.rs
+++ b/library/alloc/src/ffi/c_str.rs
@@ -970,17 +970,14 @@ impl Default for Rc<CStr> {
     /// This may or may not share an allocation with other Rcs on the same thread.
     #[inline]
     fn default() -> Self {
-        let rc = Rc::<[u8]>::from(*b"\0");
-        // `[u8]` has the same layout as `CStr`, and it is `NUL` terminated.
-        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
+        Rc::from(c"")
     }
 }
 
 #[stable(feature = "default_box_extra", since = "1.17.0")]
 impl Default for Box<CStr> {
     fn default() -> Box<CStr> {
-        let boxed: Box<[u8]> = Box::from([0]);
-        unsafe { Box::from_raw(Box::into_raw(boxed) as *mut CStr) }
+        Box::from(c"")
     }
 }
 
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index cba1ce40f75..fc3266b7479 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -64,14 +64,7 @@
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
 )]
-#![doc(cfg_hide(
-    not(test),
-    no_global_oom_handling,
-    not(no_global_oom_handling),
-    not(no_rc),
-    not(no_sync),
-    target_has_atomic = "ptr"
-))]
+#![doc(auto_cfg(hide(no_global_oom_handling, no_rc, no_sync, target_has_atomic = "ptr")))]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
 #![no_std]
@@ -195,7 +188,6 @@
 //
 // Rustdoc features:
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 // Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
 // blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
 // that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
diff --git a/library/alloc/src/raw_vec/mod.rs b/library/alloc/src/raw_vec/mod.rs
index b0027e964e4..bc9692f5b6c 100644
--- a/library/alloc/src/raw_vec/mod.rs
+++ b/library/alloc/src/raw_vec/mod.rs
@@ -23,8 +23,7 @@ mod tests;
 // ensure that the code generation related to these panics is minimal as there's
 // only one location which panics rather than a bunch throughout the module.
 #[cfg(not(no_global_oom_handling))]
-#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
-#[track_caller]
+#[cfg_attr(not(panic = "immediate-abort"), inline(never))]
 fn capacity_overflow() -> ! {
     panic!("capacity overflow");
 }
@@ -123,7 +122,6 @@ impl<T> RawVec<T, Global> {
     #[cfg(not(any(no_global_oom_handling, test)))]
     #[must_use]
     #[inline]
-    #[track_caller]
     pub(crate) fn with_capacity(capacity: usize) -> Self {
         Self { inner: RawVecInner::with_capacity(capacity, T::LAYOUT), _marker: PhantomData }
     }
@@ -132,7 +130,6 @@ impl<T> RawVec<T, Global> {
     #[cfg(not(any(no_global_oom_handling, test)))]
     #[must_use]
     #[inline]
-    #[track_caller]
     pub(crate) fn with_capacity_zeroed(capacity: usize) -> Self {
         Self {
             inner: RawVecInner::with_capacity_zeroed_in(capacity, Global, T::LAYOUT),
@@ -145,7 +142,6 @@ impl RawVecInner<Global> {
     #[cfg(not(any(no_global_oom_handling, test)))]
     #[must_use]
     #[inline]
-    #[track_caller]
     fn with_capacity(capacity: usize, elem_layout: Layout) -> Self {
         match Self::try_allocate_in(capacity, AllocInit::Uninitialized, Global, elem_layout) {
             Ok(res) => res,
@@ -177,6 +173,8 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// the returned `RawVec`.
     #[inline]
     pub(crate) const fn new_in(alloc: A) -> Self {
+        // Check assumption made in `current_memory`
+        const { assert!(T::LAYOUT.size() % T::LAYOUT.align() == 0) };
         Self { inner: RawVecInner::new_in(alloc, Alignment::of::<T>()), _marker: PhantomData }
     }
 
@@ -184,7 +182,6 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// allocator for the returned `RawVec`.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     pub(crate) fn with_capacity_in(capacity: usize, alloc: A) -> Self {
         Self {
             inner: RawVecInner::with_capacity_in(capacity, alloc, T::LAYOUT),
@@ -206,7 +203,6 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// of allocator for the returned `RawVec`.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     pub(crate) fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self {
         Self {
             inner: RawVecInner::with_capacity_zeroed_in(capacity, alloc, T::LAYOUT),
@@ -326,18 +322,18 @@ impl<T, A: Allocator> RawVec<T, A> {
     /// Aborts on OOM.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     pub(crate) fn reserve(&mut self, len: usize, additional: usize) {
-        self.inner.reserve(len, additional, T::LAYOUT)
+        // SAFETY: All calls on self.inner pass T::LAYOUT as the elem_layout
+        unsafe { self.inner.reserve(len, additional, T::LAYOUT) }
     }
 
     /// A specialized version of `self.reserve(len, 1)` which requires the
     /// caller to ensure `len == self.capacity()`.
     #[cfg(not(no_global_oom_handling))]
     #[inline(never)]
-    #[track_caller]
     pub(crate) fn grow_one(&mut self) {
-        self.inner.grow_one(T::LAYOUT)
+        // SAFETY: All calls on self.inner pass T::LAYOUT as the elem_layout
+        unsafe { self.inner.grow_one(T::LAYOUT) }
     }
 
     /// The same as `reserve`, but returns on errors instead of panicking or aborting.
@@ -346,7 +342,8 @@ impl<T, A: Allocator> RawVec<T, A> {
         len: usize,
         additional: usize,
     ) -> Result<(), TryReserveError> {
-        self.inner.try_reserve(len, additional, T::LAYOUT)
+        // SAFETY: All calls on self.inner pass T::LAYOUT as the elem_layout
+        unsafe { self.inner.try_reserve(len, additional, T::LAYOUT) }
     }
 
     /// Ensures that the buffer contains at least enough space to hold `len +
@@ -367,9 +364,9 @@ impl<T, A: Allocator> RawVec<T, A> {
     ///
     /// Aborts on OOM.
     #[cfg(not(no_global_oom_handling))]
-    #[track_caller]
     pub(crate) fn reserve_exact(&mut self, len: usize, additional: usize) {
-        self.inner.reserve_exact(len, additional, T::LAYOUT)
+        // SAFETY: All calls on self.inner pass T::LAYOUT as the elem_layout
+        unsafe { self.inner.reserve_exact(len, additional, T::LAYOUT) }
     }
 
     /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting.
@@ -378,7 +375,8 @@ impl<T, A: Allocator> RawVec<T, A> {
         len: usize,
         additional: usize,
     ) -> Result<(), TryReserveError> {
-        self.inner.try_reserve_exact(len, additional, T::LAYOUT)
+        // SAFETY: All calls on self.inner pass T::LAYOUT as the elem_layout
+        unsafe { self.inner.try_reserve_exact(len, additional, T::LAYOUT) }
     }
 
     /// Shrinks the buffer down to the specified capacity. If the given amount
@@ -392,10 +390,10 @@ impl<T, A: Allocator> RawVec<T, A> {
     ///
     /// Aborts on OOM.
     #[cfg(not(no_global_oom_handling))]
-    #[track_caller]
     #[inline]
     pub(crate) fn shrink_to_fit(&mut self, cap: usize) {
-        self.inner.shrink_to_fit(cap, T::LAYOUT)
+        // SAFETY: All calls on self.inner pass T::LAYOUT as the elem_layout
+        unsafe { self.inner.shrink_to_fit(cap, T::LAYOUT) }
     }
 }
 
@@ -417,7 +415,6 @@ impl<A: Allocator> RawVecInner<A> {
 
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     fn with_capacity_in(capacity: usize, alloc: A, elem_layout: Layout) -> Self {
         match Self::try_allocate_in(capacity, AllocInit::Uninitialized, alloc, elem_layout) {
             Ok(this) => {
@@ -442,7 +439,6 @@ impl<A: Allocator> RawVecInner<A> {
 
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     fn with_capacity_zeroed_in(capacity: usize, alloc: A, elem_layout: Layout) -> Self {
         match Self::try_allocate_in(capacity, AllocInit::Zeroed, alloc, elem_layout) {
             Ok(res) => res,
@@ -518,8 +514,12 @@ impl<A: Allocator> RawVecInner<A> {
         &self.alloc
     }
 
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
     #[inline]
-    fn current_memory(&self, elem_layout: Layout) -> Option<(NonNull<u8>, Layout)> {
+    unsafe fn current_memory(&self, elem_layout: Layout) -> Option<(NonNull<u8>, Layout)> {
         if elem_layout.size() == 0 || self.cap.as_inner() == 0 {
             None
         } else {
@@ -535,48 +535,65 @@ impl<A: Allocator> RawVecInner<A> {
         }
     }
 
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
-    fn reserve(&mut self, len: usize, additional: usize, elem_layout: Layout) {
+    unsafe fn reserve(&mut self, len: usize, additional: usize, elem_layout: Layout) {
         // Callers expect this function to be very cheap when there is already sufficient capacity.
         // Therefore, we move all the resizing and error-handling logic from grow_amortized and
         // handle_reserve behind a call, while making sure that this function is likely to be
         // inlined as just a comparison and a call if the comparison fails.
         #[cold]
-        fn do_reserve_and_handle<A: Allocator>(
+        unsafe fn do_reserve_and_handle<A: Allocator>(
             slf: &mut RawVecInner<A>,
             len: usize,
             additional: usize,
             elem_layout: Layout,
         ) {
-            if let Err(err) = slf.grow_amortized(len, additional, elem_layout) {
+            // SAFETY: Precondition passed to caller
+            if let Err(err) = unsafe { slf.grow_amortized(len, additional, elem_layout) } {
                 handle_error(err);
             }
         }
 
         if self.needs_to_grow(len, additional, elem_layout) {
-            do_reserve_and_handle(self, len, additional, elem_layout);
+            unsafe {
+                do_reserve_and_handle(self, len, additional, elem_layout);
+            }
         }
     }
 
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
-    fn grow_one(&mut self, elem_layout: Layout) {
-        if let Err(err) = self.grow_amortized(self.cap.as_inner(), 1, elem_layout) {
+    unsafe fn grow_one(&mut self, elem_layout: Layout) {
+        // SAFETY: Precondition passed to caller
+        if let Err(err) = unsafe { self.grow_amortized(self.cap.as_inner(), 1, elem_layout) } {
             handle_error(err);
         }
     }
 
-    fn try_reserve(
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
+    unsafe fn try_reserve(
         &mut self,
         len: usize,
         additional: usize,
         elem_layout: Layout,
     ) -> Result<(), TryReserveError> {
         if self.needs_to_grow(len, additional, elem_layout) {
-            self.grow_amortized(len, additional, elem_layout)?;
+            // SAFETY: Precondition passed to caller
+            unsafe {
+                self.grow_amortized(len, additional, elem_layout)?;
+            }
         }
         unsafe {
             // Inform the optimizer that the reservation has succeeded or wasn't needed
@@ -585,22 +602,33 @@ impl<A: Allocator> RawVecInner<A> {
         Ok(())
     }
 
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
     #[cfg(not(no_global_oom_handling))]
-    #[track_caller]
-    fn reserve_exact(&mut self, len: usize, additional: usize, elem_layout: Layout) {
-        if let Err(err) = self.try_reserve_exact(len, additional, elem_layout) {
+    unsafe fn reserve_exact(&mut self, len: usize, additional: usize, elem_layout: Layout) {
+        // SAFETY: Precondition passed to caller
+        if let Err(err) = unsafe { self.try_reserve_exact(len, additional, elem_layout) } {
             handle_error(err);
         }
     }
 
-    fn try_reserve_exact(
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
+    unsafe fn try_reserve_exact(
         &mut self,
         len: usize,
         additional: usize,
         elem_layout: Layout,
     ) -> Result<(), TryReserveError> {
         if self.needs_to_grow(len, additional, elem_layout) {
-            self.grow_exact(len, additional, elem_layout)?;
+            // SAFETY: Precondition passed to caller
+            unsafe {
+                self.grow_exact(len, additional, elem_layout)?;
+            }
         }
         unsafe {
             // Inform the optimizer that the reservation has succeeded or wasn't needed
@@ -609,11 +637,15 @@ impl<A: Allocator> RawVecInner<A> {
         Ok(())
     }
 
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
+    /// - `cap` must be less than or equal to `self.capacity(elem_layout.size())`
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
-    fn shrink_to_fit(&mut self, cap: usize, elem_layout: Layout) {
-        if let Err(err) = self.shrink(cap, elem_layout) {
+    unsafe fn shrink_to_fit(&mut self, cap: usize, elem_layout: Layout) {
+        if let Err(err) = unsafe { self.shrink(cap, elem_layout) } {
             handle_error(err);
         }
     }
@@ -632,7 +664,13 @@ impl<A: Allocator> RawVecInner<A> {
         self.cap = unsafe { Cap::new_unchecked(cap) };
     }
 
-    fn grow_amortized(
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
+    /// - The sum of `len` and `additional` must be greater than or equal to
+    ///   `self.capacity(elem_layout.size())`
+    unsafe fn grow_amortized(
         &mut self,
         len: usize,
         additional: usize,
@@ -657,14 +695,25 @@ impl<A: Allocator> RawVecInner<A> {
 
         let new_layout = layout_array(cap, elem_layout)?;
 
-        let ptr = finish_grow(new_layout, self.current_memory(elem_layout), &mut self.alloc)?;
-        // SAFETY: layout_array would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items
+        // SAFETY:
+        // - For the `current_memory` call: Precondition passed to caller
+        // - For the `finish_grow` call: Precondition passed to caller
+        //   + `current_memory` does the right thing
+        let ptr =
+            unsafe { finish_grow(new_layout, self.current_memory(elem_layout), &mut self.alloc)? };
 
+        // SAFETY: layout_array would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items
         unsafe { self.set_ptr_and_cap(ptr, cap) };
         Ok(())
     }
 
-    fn grow_exact(
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
+    /// - The sum of `len` and `additional` must be greater than or equal to
+    ///   `self.capacity(elem_layout.size())`
+    unsafe fn grow_exact(
         &mut self,
         len: usize,
         additional: usize,
@@ -679,7 +728,12 @@ impl<A: Allocator> RawVecInner<A> {
         let cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
         let new_layout = layout_array(cap, elem_layout)?;
 
-        let ptr = finish_grow(new_layout, self.current_memory(elem_layout), &mut self.alloc)?;
+        // SAFETY:
+        // - For the `current_memory` call: Precondition passed to caller
+        // - For the `finish_grow` call: Precondition passed to caller
+        //   + `current_memory` does the right thing
+        let ptr =
+            unsafe { finish_grow(new_layout, self.current_memory(elem_layout), &mut self.alloc)? };
         // SAFETY: layout_array would have resulted in a capacity overflow if we tried to allocate more than `isize::MAX` items
         unsafe {
             self.set_ptr_and_cap(ptr, cap);
@@ -687,9 +741,14 @@ impl<A: Allocator> RawVecInner<A> {
         Ok(())
     }
 
+    /// # Safety
+    /// - `elem_layout` must be valid for `self`, i.e. it must be the same `elem_layout` used to
+    ///   initially construct `self`
+    /// - `elem_layout`'s size must be a multiple of its alignment
+    /// - `cap` must be less than or equal to `self.capacity(elem_layout.size())`
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    fn shrink(&mut self, cap: usize, elem_layout: Layout) -> Result<(), TryReserveError> {
+    unsafe fn shrink(&mut self, cap: usize, elem_layout: Layout) -> Result<(), TryReserveError> {
         assert!(cap <= self.capacity(elem_layout.size()), "Tried to shrink to a larger capacity");
         // SAFETY: Just checked this isn't trying to grow
         unsafe { self.shrink_unchecked(cap, elem_layout) }
@@ -711,8 +770,12 @@ impl<A: Allocator> RawVecInner<A> {
         cap: usize,
         elem_layout: Layout,
     ) -> Result<(), TryReserveError> {
-        let (ptr, layout) =
-            if let Some(mem) = self.current_memory(elem_layout) { mem } else { return Ok(()) };
+        // SAFETY: Precondition passed to caller
+        let (ptr, layout) = if let Some(mem) = unsafe { self.current_memory(elem_layout) } {
+            mem
+        } else {
+            return Ok(());
+        };
 
         // If shrinking to 0, deallocate the buffer. We don't reach this point
         // for the T::IS_ZST case since current_memory() will have returned
@@ -748,7 +811,8 @@ impl<A: Allocator> RawVecInner<A> {
     /// Ideally this function would take `self` by move, but it cannot because it exists to be
     /// called from a `Drop` impl.
     unsafe fn deallocate(&mut self, elem_layout: Layout) {
-        if let Some((ptr, layout)) = self.current_memory(elem_layout) {
+        // SAFETY: Precondition passed to caller
+        if let Some((ptr, layout)) = unsafe { self.current_memory(elem_layout) } {
             unsafe {
                 self.alloc.deallocate(ptr, layout);
             }
@@ -756,10 +820,17 @@ impl<A: Allocator> RawVecInner<A> {
     }
 }
 
+/// # Safety
+/// If `current_memory` matches `Some((ptr, old_layout))`:
+/// - `ptr` must denote a block of memory *currently allocated* via `alloc`
+/// - `old_layout` must *fit* that block of memory
+/// - `new_layout` must have the same alignment as `old_layout`
+/// - `new_layout.size()` must be greater than or equal to `old_layout.size()`
+/// If `current_memory` is `None`, this function is safe.
 // not marked inline(never) since we want optimizers to be able to observe the specifics of this
 // function, see tests/codegen-llvm/vec-reserve-extend.rs.
 #[cold]
-fn finish_grow<A>(
+unsafe fn finish_grow<A>(
     new_layout: Layout,
     current_memory: Option<(NonNull<u8>, Layout)>,
     alloc: &mut A,
@@ -785,7 +856,6 @@ where
 #[cfg(not(no_global_oom_handling))]
 #[cold]
 #[optimize(size)]
-#[track_caller]
 fn handle_error(e: TryReserveError) -> ! {
     match e.kind() {
         CapacityOverflow => capacity_overflow(),
diff --git a/library/alloc/src/raw_vec/tests.rs b/library/alloc/src/raw_vec/tests.rs
index 700fa922739..15f48c03dc5 100644
--- a/library/alloc/src/raw_vec/tests.rs
+++ b/library/alloc/src/raw_vec/tests.rs
@@ -85,7 +85,7 @@ struct ZST;
 fn zst_sanity<T>(v: &RawVec<T>) {
     assert_eq!(v.capacity(), usize::MAX);
     assert_eq!(v.ptr(), core::ptr::Unique::<T>::dangling().as_ptr());
-    assert_eq!(v.inner.current_memory(T::LAYOUT), None);
+    assert_eq!(unsafe { v.inner.current_memory(T::LAYOUT) }, None);
 }
 
 #[test]
@@ -126,12 +126,12 @@ fn zst() {
     assert_eq!(v.try_reserve_exact(101, usize::MAX - 100), cap_err);
     zst_sanity(&v);
 
-    assert_eq!(v.inner.grow_amortized(100, usize::MAX - 100, ZST::LAYOUT), cap_err);
-    assert_eq!(v.inner.grow_amortized(101, usize::MAX - 100, ZST::LAYOUT), cap_err);
+    assert_eq!(unsafe { v.inner.grow_amortized(100, usize::MAX - 100, ZST::LAYOUT) }, cap_err);
+    assert_eq!(unsafe { v.inner.grow_amortized(101, usize::MAX - 100, ZST::LAYOUT) }, cap_err);
     zst_sanity(&v);
 
-    assert_eq!(v.inner.grow_exact(100, usize::MAX - 100, ZST::LAYOUT), cap_err);
-    assert_eq!(v.inner.grow_exact(101, usize::MAX - 100, ZST::LAYOUT), cap_err);
+    assert_eq!(unsafe { v.inner.grow_exact(100, usize::MAX - 100, ZST::LAYOUT) }, cap_err);
+    assert_eq!(unsafe { v.inner.grow_exact(101, usize::MAX - 100, ZST::LAYOUT) }, cap_err);
     zst_sanity(&v);
 }
 
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index fcb466778a3..023238a00db 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -277,7 +277,9 @@ use crate::vec::Vec;
 // This is repr(C) to future-proof against possible field-reordering, which
 // would interfere with otherwise safe [into|from]_raw() of transmutable
 // inner types.
-#[repr(C)]
+// repr(align(2)) (forcing alignment to at least 2) is required because usize
+// has 1-byte alignment on AVR.
+#[repr(C, align(2))]
 struct RcInner<T: ?Sized> {
     strong: Cell<usize>,
     weak: Cell<usize>,
@@ -480,8 +482,6 @@ impl<T> Rc<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::rc::Rc;
     ///
     /// let mut five = Rc::<u32>::new_uninit();
@@ -572,7 +572,6 @@ impl<T> Rc<T> {
     ///
     /// ```
     /// #![feature(allocator_api)]
-    /// #![feature(get_mut_unchecked)]
     ///
     /// use std::rc::Rc;
     ///
@@ -1014,8 +1013,6 @@ impl<T> Rc<[T]> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::rc::Rc;
     ///
     /// let mut values = Rc::<[u32]>::new_uninit_slice(3);
@@ -1181,8 +1178,6 @@ impl<T, A: Allocator> Rc<mem::MaybeUninit<T>, A> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::rc::Rc;
     ///
     /// let mut five = Rc::<u32>::new_uninit();
@@ -1218,8 +1213,6 @@ impl<T, A: Allocator> Rc<[mem::MaybeUninit<T>], A> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::rc::Rc;
     ///
     /// let mut values = Rc::<[u32]>::new_uninit_slice(3);
@@ -2386,7 +2379,7 @@ impl<T> Default for Rc<[T]> {
 }
 
 #[cfg(not(no_global_oom_handling))]
-#[stable(feature = "pin_default_impls", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "pin_default_impls", since = "1.91.0")]
 impl<T> Default for Pin<Rc<T>>
 where
     T: ?Sized,
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index e669c4708ad..ae30cabf5af 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -1105,7 +1105,6 @@ impl String {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_confusables("append", "push")]
     #[rustc_diagnostic_item = "string_push_str"]
@@ -1208,7 +1207,6 @@ impl String {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn reserve(&mut self, additional: usize) {
         self.vec.reserve(additional)
@@ -1260,7 +1258,6 @@ impl String {
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     pub fn reserve_exact(&mut self, additional: usize) {
         self.vec.reserve_exact(additional)
     }
@@ -1356,7 +1353,6 @@ impl String {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn shrink_to_fit(&mut self) {
         self.vec.shrink_to_fit()
@@ -1384,7 +1380,6 @@ impl String {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     #[stable(feature = "shrink_to", since = "1.56.0")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.vec.shrink_to(min_capacity)
@@ -1406,7 +1401,6 @@ impl String {
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     pub fn push(&mut self, ch: char) {
         let len = self.len();
         let ch_len = ch.len_utf8();
@@ -2115,7 +2109,6 @@ impl String {
     #[stable(feature = "box_str", since = "1.4.0")]
     #[must_use = "`self` will be dropped if the result is not used"]
     #[inline]
-    #[track_caller]
     pub fn into_boxed_str(self) -> Box<str> {
         let slice = self.vec.into_boxed_slice();
         unsafe { from_boxed_utf8_unchecked(slice) }
@@ -2293,7 +2286,6 @@ impl Error for FromUtf16Error {}
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Clone for String {
-    #[track_caller]
     fn clone(&self) -> Self {
         String { vec: self.vec.clone() }
     }
@@ -2302,7 +2294,6 @@ impl Clone for String {
     ///
     /// This method is preferred over simply assigning `source.clone()` to `self`,
     /// as it avoids reallocation if possible.
-    #[track_caller]
     fn clone_from(&mut self, source: &Self) {
         self.vec.clone_from(&source.vec);
     }
@@ -2477,13 +2468,11 @@ impl<'a> Extend<Cow<'a, str>> for String {
 #[unstable(feature = "ascii_char", issue = "110998")]
 impl Extend<core::ascii::Char> for String {
     #[inline]
-    #[track_caller]
     fn extend<I: IntoIterator<Item = core::ascii::Char>>(&mut self, iter: I) {
         self.vec.extend(iter.into_iter().map(|c| c.to_u8()));
     }
 
     #[inline]
-    #[track_caller]
     fn extend_one(&mut self, c: core::ascii::Char) {
         self.vec.push(c.to_u8());
     }
@@ -2493,13 +2482,11 @@ impl Extend<core::ascii::Char> for String {
 #[unstable(feature = "ascii_char", issue = "110998")]
 impl<'a> Extend<&'a core::ascii::Char> for String {
     #[inline]
-    #[track_caller]
     fn extend<I: IntoIterator<Item = &'a core::ascii::Char>>(&mut self, iter: I) {
         self.extend(iter.into_iter().cloned());
     }
 
     #[inline]
-    #[track_caller]
     fn extend_one(&mut self, c: &'a core::ascii::Char) {
         self.vec.push(c.to_u8());
     }
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 32396cccb8f..6432bdfbbed 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -341,7 +341,7 @@ pub struct Weak<
     // but it is not necessarily a valid pointer.
     // `Weak::new` sets this to `usize::MAX` so that it doesn’t need
     // to allocate space on the heap. That's not a value a real pointer
-    // will ever have because RcInner has alignment at least 2.
+    // will ever have because ArcInner has alignment at least 2.
     ptr: NonNull<ArcInner<T>>,
     alloc: A,
 }
@@ -366,7 +366,9 @@ impl<T: ?Sized, A: Allocator> fmt::Debug for Weak<T, A> {
 // This is repr(C) to future-proof against possible field-reordering, which
 // would interfere with otherwise safe [into|from]_raw() of transmutable
 // inner types.
-#[repr(C)]
+// Unlike RcInner, repr(align(2)) is not strictly required because atomic types
+// have the alignment same as its size, but we use it for consistency and clarity.
+#[repr(C, align(2))]
 struct ArcInner<T: ?Sized> {
     strong: Atomic<usize>,
 
@@ -480,8 +482,6 @@ impl<T> Arc<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let mut five = Arc::<u32>::new_uninit();
@@ -586,7 +586,6 @@ impl<T> Arc<T> {
     ///
     /// ```
     /// #![feature(allocator_api)]
-    /// #![feature(get_mut_unchecked)]
     ///
     /// use std::sync::Arc;
     ///
@@ -1156,8 +1155,6 @@ impl<T> Arc<[T]> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let mut values = Arc::<[u32]>::new_uninit_slice(3);
@@ -1326,8 +1323,6 @@ impl<T, A: Allocator> Arc<mem::MaybeUninit<T>, A> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let mut five = Arc::<u32>::new_uninit();
@@ -1364,8 +1359,6 @@ impl<T, A: Allocator> Arc<[mem::MaybeUninit<T>], A> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(get_mut_unchecked)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let mut values = Arc::<[u32]>::new_uninit_slice(3);
@@ -1622,9 +1615,9 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     pub fn as_ptr(this: &Self) -> *const T {
         let ptr: *mut ArcInner<T> = NonNull::as_ptr(this.ptr);
 
-        // SAFETY: This cannot go through Deref::deref or RcInnerPtr::inner because
+        // SAFETY: This cannot go through Deref::deref or ArcInnerPtr::inner because
         // this is required to retain raw/mut provenance such that e.g. `get_mut` can
-        // write through the pointer after the Rc is recovered through `from_raw`.
+        // write through the pointer after the Arc is recovered through `from_raw`.
         unsafe { &raw mut (*ptr).data }
     }
 
@@ -2459,7 +2452,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     /// If any other `Arc` or [`Weak`] pointers to the same allocation exist, then
     /// they must not be dereferenced or have active borrows for the duration
     /// of the returned borrow, and their inner type must be exactly the same as the
-    /// inner type of this Rc (including lifetimes). This is trivially the case if no
+    /// inner type of this Arc (including lifetimes). This is trivially the case if no
     /// such pointers exist, for example immediately after `Arc::new`.
     ///
     /// # Examples
@@ -3031,7 +3024,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
             // Otherwise, we're guaranteed the pointer came from a nondangling Weak.
             // SAFETY: data_offset is safe to call, as ptr references a real (potentially dropped) T.
             let offset = unsafe { data_offset(ptr) };
-            // Thus, we reverse the offset to get the whole RcInner.
+            // Thus, we reverse the offset to get the whole ArcInner.
             // SAFETY: the pointer originated from a Weak, so this offset is safe.
             unsafe { ptr.byte_sub(offset) as *mut ArcInner<T> }
         };
@@ -3645,7 +3638,7 @@ impl<T> Default for Arc<[T]> {
 }
 
 #[cfg(not(no_global_oom_handling))]
-#[stable(feature = "pin_default_impls", since = "CURRENT_RUSTC_VERSION")]
+#[stable(feature = "pin_default_impls", since = "1.91.0")]
 impl<T> Default for Pin<Arc<T>>
 where
     T: ?Sized,
@@ -4024,7 +4017,7 @@ impl<T: ?Sized, A: Allocator> Unpin for Arc<T, A> {}
 /// valid instance of T, but the T is allowed to be dropped.
 unsafe fn data_offset<T: ?Sized>(ptr: *const T) -> usize {
     // Align the unsized value to the end of the ArcInner.
-    // Because RcInner is repr(C), it will always be the last field in memory.
+    // Because ArcInner is repr(C), it will always be the last field in memory.
     // SAFETY: since the only unsized types possible are slices, trait objects,
     // and extern types, the input safety requirement is currently enough to
     // satisfy the requirements of align_of_val_raw; this is an implementation
diff --git a/library/alloc/src/vec/cow.rs b/library/alloc/src/vec/cow.rs
index 4deb35efffc..c18091705a6 100644
--- a/library/alloc/src/vec/cow.rs
+++ b/library/alloc/src/vec/cow.rs
@@ -58,7 +58,6 @@ impl<'a, T> FromIterator<T> for Cow<'a, [T]>
 where
     T: Clone,
 {
-    #[track_caller]
     fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {
         Cow::Owned(FromIterator::from_iter(it))
     }
diff --git a/library/alloc/src/vec/extract_if.rs b/library/alloc/src/vec/extract_if.rs
index a456d3d9e60..cb9e14f554d 100644
--- a/library/alloc/src/vec/extract_if.rs
+++ b/library/alloc/src/vec/extract_if.rs
@@ -64,27 +64,37 @@ where
     type Item = T;
 
     fn next(&mut self) -> Option<T> {
-        unsafe {
-            while self.idx < self.end {
-                let i = self.idx;
-                let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
-                let drained = (self.pred)(&mut v[i]);
-                // Update the index *after* the predicate is called. If the index
-                // is updated prior and the predicate panics, the element at this
-                // index would be leaked.
-                self.idx += 1;
-                if drained {
-                    self.del += 1;
-                    return Some(ptr::read(&v[i]));
-                } else if self.del > 0 {
-                    let del = self.del;
-                    let src: *const T = &v[i];
-                    let dst: *mut T = &mut v[i - del];
-                    ptr::copy_nonoverlapping(src, dst, 1);
+        while self.idx < self.end {
+            let i = self.idx;
+            // SAFETY:
+            //  We know that `i < self.end` from the if guard and that `self.end <= self.old_len` from
+            //  the validity of `Self`. Therefore `i` points to an element within `vec`.
+            //
+            //  Additionally, the i-th element is valid because each element is visited at most once
+            //  and it is the first time we access vec[i].
+            //
+            //  Note: we can't use `vec.get_unchecked_mut(i)` here since the precondition for that
+            //  function is that i < vec.len(), but we've set vec's length to zero.
+            let cur = unsafe { &mut *self.vec.as_mut_ptr().add(i) };
+            let drained = (self.pred)(cur);
+            // Update the index *after* the predicate is called. If the index
+            // is updated prior and the predicate panics, the element at this
+            // index would be leaked.
+            self.idx += 1;
+            if drained {
+                self.del += 1;
+                // SAFETY: We never touch this element again after returning it.
+                return Some(unsafe { ptr::read(cur) });
+            } else if self.del > 0 {
+                // SAFETY: `self.del` > 0, so the hole slot must not overlap with current element.
+                // We use copy for move, and never touch this element again.
+                unsafe {
+                    let hole_slot = self.vec.as_mut_ptr().add(i - self.del);
+                    ptr::copy_nonoverlapping(cur, hole_slot, 1);
                 }
             }
-            None
         }
+        None
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -95,14 +105,18 @@ where
 #[stable(feature = "extract_if", since = "1.87.0")]
 impl<T, F, A: Allocator> Drop for ExtractIf<'_, T, F, A> {
     fn drop(&mut self) {
-        unsafe {
-            if self.idx < self.old_len && self.del > 0 {
-                let ptr = self.vec.as_mut_ptr();
-                let src = ptr.add(self.idx);
-                let dst = src.sub(self.del);
-                let tail_len = self.old_len - self.idx;
-                src.copy_to(dst, tail_len);
+        if self.del > 0 {
+            // SAFETY: Trailing unchecked items must be valid since we never touch them.
+            unsafe {
+                ptr::copy(
+                    self.vec.as_ptr().add(self.idx),
+                    self.vec.as_mut_ptr().add(self.idx - self.del),
+                    self.old_len - self.idx,
+                );
             }
+        }
+        // SAFETY: After filling holes, all items are in contiguous memory.
+        unsafe {
             self.vec.set_len(self.old_len - self.del);
         }
     }
diff --git a/library/alloc/src/vec/in_place_collect.rs b/library/alloc/src/vec/in_place_collect.rs
index b98a118048f..8a7c0b92ecc 100644
--- a/library/alloc/src/vec/in_place_collect.rs
+++ b/library/alloc/src/vec/in_place_collect.rs
@@ -229,7 +229,6 @@ where
     I: Iterator<Item = T> + InPlaceCollect,
     <I as SourceIter>::Source: AsVecIntoIter,
 {
-    #[track_caller]
     default fn from_iter(iterator: I) -> Self {
         // Select the implementation in const eval to avoid codegen of the dead branch to improve compile times.
         let fun: fn(I) -> Vec<T> = const {
@@ -247,7 +246,6 @@ where
     }
 }
 
-#[track_caller]
 fn from_iter_in_place<I, T>(mut iterator: I) -> Vec<T>
 where
     I: Iterator<Item = T> + InPlaceCollect,
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 10c7ee4f6c8..45d6c28e186 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -515,7 +515,6 @@ impl<T> Vec<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
     #[rustc_diagnostic_item = "vec_with_capacity"]
-    #[track_caller]
     pub fn with_capacity(capacity: usize) -> Self {
         Self::with_capacity_in(capacity, Global)
     }
@@ -926,7 +925,6 @@ impl<T, A: Allocator> Vec<T, A> {
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[track_caller]
     pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
         Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
     }
@@ -1335,7 +1333,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     #[rustc_diagnostic_item = "vec_reserve"]
     pub fn reserve(&mut self, additional: usize) {
         self.buf.reserve(self.len, additional);
@@ -1367,7 +1364,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     pub fn reserve_exact(&mut self, additional: usize) {
         self.buf.reserve_exact(self.len, additional);
     }
@@ -1471,7 +1467,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     #[inline]
     pub fn shrink_to_fit(&mut self) {
         // The capacity is never less than the length, and there's nothing to do when
@@ -1502,7 +1497,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "shrink_to", since = "1.56.0")]
-    #[track_caller]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         if self.capacity() > min_capacity {
             self.buf.shrink_to_fit(cmp::max(self.len, min_capacity));
@@ -1536,7 +1530,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[track_caller]
     pub fn into_boxed_slice(mut self) -> Box<[T], A> {
         unsafe {
             self.shrink_to_fit();
@@ -2020,8 +2013,7 @@ impl<T, A: Allocator> Vec<T, A> {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn swap_remove(&mut self, index: usize) -> T {
         #[cold]
-        #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
-        #[track_caller]
+        #[cfg_attr(not(panic = "immediate-abort"), inline(never))]
         #[optimize(size)]
         fn assert_failed(index: usize, len: usize) -> ! {
             panic!("swap_remove index (is {index}) should be < len (is {len})");
@@ -2102,7 +2094,7 @@ impl<T, A: Allocator> Vec<T, A> {
     #[must_use = "if you don't need a reference to the value, use `Vec::insert` instead"]
     pub fn insert_mut(&mut self, index: usize, element: T) -> &mut T {
         #[cold]
-        #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+        #[cfg_attr(not(panic = "immediate-abort"), inline(never))]
         #[track_caller]
         #[optimize(size)]
         fn assert_failed(index: usize, len: usize) -> ! {
@@ -2166,16 +2158,44 @@ impl<T, A: Allocator> Vec<T, A> {
     #[rustc_confusables("delete", "take")]
     pub fn remove(&mut self, index: usize) -> T {
         #[cold]
-        #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+        #[cfg_attr(not(panic = "immediate-abort"), inline(never))]
         #[track_caller]
         #[optimize(size)]
         fn assert_failed(index: usize, len: usize) -> ! {
             panic!("removal index (is {index}) should be < len (is {len})");
         }
 
+        match self.try_remove(index) {
+            Some(elem) => elem,
+            None => assert_failed(index, self.len()),
+        }
+    }
+
+    /// Remove and return the element at position `index` within the vector,
+    /// shifting all elements after it to the left, or [`None`] if it does not
+    /// exist.
+    ///
+    /// Note: Because this shifts over the remaining elements, it has a
+    /// worst-case performance of *O*(*n*). If you'd like to remove
+    /// elements from the beginning of the `Vec`, consider using
+    /// [`VecDeque::pop_front`] instead.
+    ///
+    /// [`VecDeque::pop_front`]: crate::collections::VecDeque::pop_front
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(vec_try_remove)]
+    /// let mut v = vec![1, 2, 3];
+    /// assert_eq!(v.try_remove(0), Some(1));
+    /// assert_eq!(v.try_remove(2), None);
+    /// ```
+    #[unstable(feature = "vec_try_remove", issue = "146954")]
+    #[rustc_confusables("delete", "take", "remove")]
+    pub fn try_remove(&mut self, index: usize) -> Option<T> {
         let len = self.len();
         if index >= len {
-            assert_failed(index, len);
+            return None;
         }
         unsafe {
             // infallible
@@ -2191,7 +2211,7 @@ impl<T, A: Allocator> Vec<T, A> {
                 ptr::copy(ptr.add(1), ptr, len - index - 1);
             }
             self.set_len(len - 1);
-            ret
+            Some(ret)
         }
     }
 
@@ -2540,7 +2560,6 @@ impl<T, A: Allocator> Vec<T, A> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_confusables("push_back", "put", "append")]
-    #[track_caller]
     pub fn push(&mut self, value: T) {
         let _ = self.push_mut(value);
     }
@@ -2617,7 +2636,6 @@ impl<T, A: Allocator> Vec<T, A> {
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[unstable(feature = "push_mut", issue = "135974")]
-    #[track_caller]
     #[must_use = "if you don't need a reference to the value, use `Vec::push` instead"]
     pub fn push_mut(&mut self, value: T) -> &mut T {
         // Inform codegen that the length does not change across grow_one().
@@ -2765,7 +2783,6 @@ impl<T, A: Allocator> Vec<T, A> {
     #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[stable(feature = "append", since = "1.4.0")]
-    #[track_caller]
     pub fn append(&mut self, other: &mut Self) {
         unsafe {
             self.append_elements(other.as_slice() as _);
@@ -2776,7 +2793,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// Appends elements to `self` from other buffer.
     #[cfg(not(no_global_oom_handling))]
     #[inline]
-    #[track_caller]
     unsafe fn append_elements(&mut self, other: *const [T]) {
         let count = other.len();
         self.reserve(count);
@@ -2955,7 +2971,7 @@ impl<T, A: Allocator> Vec<T, A> {
         A: Clone,
     {
         #[cold]
-        #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+        #[cfg_attr(not(panic = "immediate-abort"), inline(never))]
         #[track_caller]
         #[optimize(size)]
         fn assert_failed(at: usize, len: usize) -> ! {
@@ -3011,7 +3027,6 @@ impl<T, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "vec_resize_with", since = "1.33.0")]
-    #[track_caller]
     pub fn resize_with<F>(&mut self, new_len: usize, f: F)
     where
         F: FnMut() -> T,
@@ -3276,7 +3291,6 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "vec_resize", since = "1.5.0")]
-    #[track_caller]
     pub fn resize(&mut self, new_len: usize, value: T) {
         let len = self.len();
 
@@ -3307,7 +3321,6 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
     /// [`extend`]: Vec::extend
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
-    #[track_caller]
     pub fn extend_from_slice(&mut self, other: &[T]) {
         self.spec_extend(other.iter())
     }
@@ -3338,7 +3351,6 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "vec_extend_from_within", since = "1.53.0")]
-    #[track_caller]
     pub fn extend_from_within<R>(&mut self, src: R)
     where
         R: RangeBounds<usize>,
@@ -3399,7 +3411,6 @@ impl<T, A: Allocator, const N: usize> Vec<[T; N], A> {
 
 impl<T: Clone, A: Allocator> Vec<T, A> {
     #[cfg(not(no_global_oom_handling))]
-    #[track_caller]
     /// Extend the vector by `n` clones of value.
     fn extend_with(&mut self, n: usize, value: T) {
         self.reserve(n);
@@ -3460,7 +3471,6 @@ impl<T: PartialEq, A: Allocator> Vec<T, A> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_diagnostic_item = "vec_from_elem"]
-#[track_caller]
 pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
     <T as SpecFromElem>::from_elem(elem, n, Global)
 }
@@ -3468,7 +3478,6 @@ pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
 #[doc(hidden)]
 #[cfg(not(no_global_oom_handling))]
 #[unstable(feature = "allocator_api", issue = "32838")]
-#[track_caller]
 pub fn from_elem_in<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> {
     <T as SpecFromElem>::from_elem(elem, n, alloc)
 }
@@ -3559,7 +3568,6 @@ unsafe impl<T, A: Allocator> ops::DerefPure for Vec<T, A> {}
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
-    #[track_caller]
     fn clone(&self) -> Self {
         let alloc = self.allocator().clone();
         <[T]>::to_vec_in(&**self, alloc)
@@ -3587,7 +3595,6 @@ impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
     /// // And no reallocation occurred
     /// assert_eq!(yp, y.as_ptr());
     /// ```
-    #[track_caller]
     fn clone_from(&mut self, source: &Self) {
         crate::slice::SpecCloneIntoVec::clone_into(source.as_slice(), self);
     }
@@ -3678,7 +3685,6 @@ impl<T, I: SliceIndex<[T]>, A: Allocator> IndexMut<I> for Vec<T, A> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> FromIterator<T> for Vec<T> {
     #[inline]
-    #[track_caller]
     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
         <Self as SpecFromIter<T, I::IntoIter>>::from_iter(iter.into_iter())
     }
@@ -3747,19 +3753,16 @@ impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec<T, A> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T, A: Allocator> Extend<T> for Vec<T, A> {
     #[inline]
-    #[track_caller]
     fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
         <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter())
     }
 
     #[inline]
-    #[track_caller]
     fn extend_one(&mut self, item: T) {
         self.push(item);
     }
 
     #[inline]
-    #[track_caller]
     fn extend_reserve(&mut self, additional: usize) {
         self.reserve(additional);
     }
@@ -3779,7 +3782,6 @@ impl<T, A: Allocator> Vec<T, A> {
     // leaf method to which various SpecFrom/SpecExtend implementations delegate when
     // they have no further optimizations to apply
     #[cfg(not(no_global_oom_handling))]
-    #[track_caller]
     fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
         // This is the case for a general iterator.
         //
@@ -3807,7 +3809,6 @@ impl<T, A: Allocator> Vec<T, A> {
     // specific extend for `TrustedLen` iterators, called both by the specializations
     // and internal places where resolving specialization makes compilation slower
     #[cfg(not(no_global_oom_handling))]
-    #[track_caller]
     fn extend_trusted(&mut self, iterator: impl iter::TrustedLen<Item = T>) {
         let (low, high) = iterator.size_hint();
         if let Some(additional) = high {
@@ -3985,19 +3986,16 @@ impl<T, A: Allocator> Vec<T, A> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "extend_ref", since = "1.2.0")]
 impl<'a, T: Copy + 'a, A: Allocator> Extend<&'a T> for Vec<T, A> {
-    #[track_caller]
     fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
         self.spec_extend(iter.into_iter())
     }
 
     #[inline]
-    #[track_caller]
     fn extend_one(&mut self, &item: &'a T) {
         self.push(item);
     }
 
     #[inline]
-    #[track_caller]
     fn extend_reserve(&mut self, additional: usize) {
         self.reserve(additional);
     }
@@ -4108,7 +4106,6 @@ impl<T: Clone> From<&[T]> for Vec<T> {
     /// ```
     /// assert_eq!(Vec::from(&[1, 2, 3][..]), vec![1, 2, 3]);
     /// ```
-    #[track_caller]
     fn from(s: &[T]) -> Vec<T> {
         s.to_vec()
     }
@@ -4124,7 +4121,6 @@ impl<T: Clone> From<&mut [T]> for Vec<T> {
     /// ```
     /// assert_eq!(Vec::from(&mut [1, 2, 3][..]), vec![1, 2, 3]);
     /// ```
-    #[track_caller]
     fn from(s: &mut [T]) -> Vec<T> {
         s.to_vec()
     }
@@ -4140,7 +4136,6 @@ impl<T: Clone, const N: usize> From<&[T; N]> for Vec<T> {
     /// ```
     /// assert_eq!(Vec::from(&[1, 2, 3]), vec![1, 2, 3]);
     /// ```
-    #[track_caller]
     fn from(s: &[T; N]) -> Vec<T> {
         Self::from(s.as_slice())
     }
@@ -4156,7 +4151,6 @@ impl<T: Clone, const N: usize> From<&mut [T; N]> for Vec<T> {
     /// ```
     /// assert_eq!(Vec::from(&mut [1, 2, 3]), vec![1, 2, 3]);
     /// ```
-    #[track_caller]
     fn from(s: &mut [T; N]) -> Vec<T> {
         Self::from(s.as_mut_slice())
     }
@@ -4172,7 +4166,6 @@ impl<T, const N: usize> From<[T; N]> for Vec<T> {
     /// ```
     /// assert_eq!(Vec::from([1, 2, 3]), vec![1, 2, 3]);
     /// ```
-    #[track_caller]
     fn from(s: [T; N]) -> Vec<T> {
         <[T]>::into_vec(Box::new(s))
     }
@@ -4197,7 +4190,6 @@ where
     /// let b: Cow<'_, [i32]> = Cow::Borrowed(&[1, 2, 3]);
     /// assert_eq!(Vec::from(o), Vec::from(b));
     /// ```
-    #[track_caller]
     fn from(s: Cow<'a, [T]>) -> Vec<T> {
         s.into_owned()
     }
@@ -4244,7 +4236,6 @@ impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
     ///
     /// assert_eq!(Box::from(vec), vec![1, 2, 3].into_boxed_slice());
     /// ```
-    #[track_caller]
     fn from(v: Vec<T, A>) -> Self {
         v.into_boxed_slice()
     }
@@ -4260,7 +4251,6 @@ impl From<&str> for Vec<u8> {
     /// ```
     /// assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']);
     /// ```
-    #[track_caller]
     fn from(s: &str) -> Vec<u8> {
         From::from(s.as_bytes())
     }
diff --git a/library/alloc/src/vec/spec_extend.rs b/library/alloc/src/vec/spec_extend.rs
index b98db669059..7085bceef5b 100644
--- a/library/alloc/src/vec/spec_extend.rs
+++ b/library/alloc/src/vec/spec_extend.rs
@@ -6,7 +6,6 @@ use crate::alloc::Allocator;
 
 // Specialization trait used for Vec::extend
 pub(super) trait SpecExtend<T, I> {
-    #[track_caller]
     fn spec_extend(&mut self, iter: I);
 }
 
@@ -14,7 +13,6 @@ impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
 where
     I: Iterator<Item = T>,
 {
-    #[track_caller]
     default fn spec_extend(&mut self, iter: I) {
         self.extend_desugared(iter)
     }
@@ -24,14 +22,12 @@ impl<T, I, A: Allocator> SpecExtend<T, I> for Vec<T, A>
 where
     I: TrustedLen<Item = T>,
 {
-    #[track_caller]
     default fn spec_extend(&mut self, iterator: I) {
         self.extend_trusted(iterator)
     }
 }
 
 impl<T, A: Allocator> SpecExtend<T, IntoIter<T>> for Vec<T, A> {
-    #[track_caller]
     fn spec_extend(&mut self, mut iterator: IntoIter<T>) {
         unsafe {
             self.append_elements(iterator.as_slice() as _);
@@ -45,7 +41,6 @@ where
     I: Iterator<Item = &'a T>,
     T: Clone,
 {
-    #[track_caller]
     default fn spec_extend(&mut self, iterator: I) {
         self.spec_extend(iterator.cloned())
     }
@@ -55,7 +50,6 @@ impl<'a, T: 'a, A: Allocator> SpecExtend<&'a T, slice::Iter<'a, T>> for Vec<T, A
 where
     T: Copy,
 {
-    #[track_caller]
     fn spec_extend(&mut self, iterator: slice::Iter<'a, T>) {
         let slice = iterator.as_slice();
         unsafe { self.append_elements(slice) };
diff --git a/library/alloc/src/vec/spec_from_elem.rs b/library/alloc/src/vec/spec_from_elem.rs
index 6c7b4d89f2d..96d701e15d4 100644
--- a/library/alloc/src/vec/spec_from_elem.rs
+++ b/library/alloc/src/vec/spec_from_elem.rs
@@ -10,7 +10,6 @@ pub(super) trait SpecFromElem: Sized {
 }
 
 impl<T: Clone> SpecFromElem for T {
-    #[track_caller]
     default fn from_elem<A: Allocator>(elem: Self, n: usize, alloc: A) -> Vec<Self, A> {
         let mut v = Vec::with_capacity_in(n, alloc);
         v.extend_with(n, elem);
@@ -20,7 +19,6 @@ impl<T: Clone> SpecFromElem for T {
 
 impl<T: Clone + IsZero> SpecFromElem for T {
     #[inline]
-    #[track_caller]
     default fn from_elem<A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> {
         if elem.is_zero() {
             return Vec { buf: RawVec::with_capacity_zeroed_in(n, alloc), len: n };
@@ -33,7 +31,6 @@ impl<T: Clone + IsZero> SpecFromElem for T {
 
 impl SpecFromElem for i8 {
     #[inline]
-    #[track_caller]
     fn from_elem<A: Allocator>(elem: i8, n: usize, alloc: A) -> Vec<i8, A> {
         if elem == 0 {
             return Vec { buf: RawVec::with_capacity_zeroed_in(n, alloc), len: n };
@@ -49,7 +46,6 @@ impl SpecFromElem for i8 {
 
 impl SpecFromElem for u8 {
     #[inline]
-    #[track_caller]
     fn from_elem<A: Allocator>(elem: u8, n: usize, alloc: A) -> Vec<u8, A> {
         if elem == 0 {
             return Vec { buf: RawVec::with_capacity_zeroed_in(n, alloc), len: n };
diff --git a/library/alloc/src/vec/spec_from_iter.rs b/library/alloc/src/vec/spec_from_iter.rs
index ad7688e1c59..e1f0b639bdf 100644
--- a/library/alloc/src/vec/spec_from_iter.rs
+++ b/library/alloc/src/vec/spec_from_iter.rs
@@ -29,14 +29,12 @@ impl<T, I> SpecFromIter<T, I> for Vec<T>
 where
     I: Iterator<Item = T>,
 {
-    #[track_caller]
     default fn from_iter(iterator: I) -> Self {
         SpecFromIterNested::from_iter(iterator)
     }
 }
 
 impl<T> SpecFromIter<T, IntoIter<T>> for Vec<T> {
-    #[track_caller]
     fn from_iter(iterator: IntoIter<T>) -> Self {
         // A common case is passing a vector into a function which immediately
         // re-collects into a vector. We can short circuit this if the IntoIter
diff --git a/library/alloc/src/vec/spec_from_iter_nested.rs b/library/alloc/src/vec/spec_from_iter_nested.rs
index 22eed238798..77f7761d22f 100644
--- a/library/alloc/src/vec/spec_from_iter_nested.rs
+++ b/library/alloc/src/vec/spec_from_iter_nested.rs
@@ -15,7 +15,6 @@ impl<T, I> SpecFromIterNested<T, I> for Vec<T>
 where
     I: Iterator<Item = T>,
 {
-    #[track_caller]
     default fn from_iter(mut iterator: I) -> Self {
         // Unroll the first iteration, as the vector is going to be
         // expanded on this iteration in every case when the iterable is not
@@ -48,7 +47,6 @@ impl<T, I> SpecFromIterNested<T, I> for Vec<T>
 where
     I: TrustedLen<Item = T>,
 {
-    #[track_caller]
     fn from_iter(iterator: I) -> Self {
         let mut vector = match iterator.size_hint() {
             (_, Some(upper)) => Vec::with_capacity(upper),
diff --git a/library/alloc/src/vec/splice.rs b/library/alloc/src/vec/splice.rs
index ed1a0dda76d..d571e35828a 100644
--- a/library/alloc/src/vec/splice.rs
+++ b/library/alloc/src/vec/splice.rs
@@ -52,7 +52,6 @@ impl<I: Iterator, A: Allocator> ExactSizeIterator for Splice<'_, I, A> {}
 
 #[stable(feature = "vec_splice", since = "1.21.0")]
 impl<I: Iterator, A: Allocator> Drop for Splice<'_, I, A> {
-    #[track_caller]
     fn drop(&mut self) {
         self.drain.by_ref().for_each(drop);
         // At this point draining is done and the only remaining tasks are splicing
@@ -124,7 +123,6 @@ impl<T, A: Allocator> Drain<'_, T, A> {
     }
 
     /// Makes room for inserting more elements before the tail.
-    #[track_caller]
     unsafe fn move_tail(&mut self, additional: usize) {
         let vec = unsafe { self.vec.as_mut() };
         let len = self.tail_start + self.tail_len;