Merge from rustc

alloc/Cargo.toml

@@ -10,7 +10,7 @@ edition = "2021"
 
 [dependencies]
 core = { path = "../core" }
-compiler_builtins = { version = "0.1.123", features = ['rustc-dep-of-std'] }
+compiler_builtins = { version = "0.1.125", features = ['rustc-dep-of-std'] }
 
 [dev-dependencies]
 rand = { version = "0.8.5", default-features = false, features = ["alloc"] }

alloc/src/alloc.rs

@@ -89,6 +89,7 @@ pub use std::alloc::Global;
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn alloc(layout: Layout) -> *mut u8 {
     unsafe {
         // Make sure we don't accidentally allow omitting the allocator shim in
@@ -113,6 +114,7 @@ pub unsafe fn alloc(layout: Layout) -> *mut u8 {
 /// See [`GlobalAlloc::dealloc`].
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
 }
@@ -132,6 +134,7 @@ pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
     unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
 }
@@ -166,13 +169,15 @@ pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
     unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
 }
 
 #[cfg(not(test))]
 impl Global {
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
         match layout.size() {
             0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
@@ -187,6 +192,7 @@ impl Global {
 
     // SAFETY: Same as `Allocator::grow`
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn grow_impl(
         &self,
         ptr: NonNull<u8>,
@@ -237,16 +243,19 @@ impl Global {
 #[cfg(not(test))]
 unsafe impl Allocator for Global {
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
         self.alloc_impl(layout, false)
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
         self.alloc_impl(layout, true)
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
         if layout.size() != 0 {
             // SAFETY: `layout` is non-zero in size,
@@ -256,6 +265,7 @@ unsafe impl Allocator for Global {
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn grow(
         &self,
         ptr: NonNull<u8>,
@@ -267,6 +277,7 @@ unsafe impl Allocator for Global {
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn grow_zeroed(
         &self,
         ptr: NonNull<u8>,
@@ -278,6 +289,7 @@ unsafe impl Allocator for Global {
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn shrink(
         &self,
         ptr: NonNull<u8>,
@@ -325,6 +337,7 @@ unsafe impl Allocator for Global {
 #[cfg(all(not(no_global_oom_handling), not(test)))]
 #[lang = "exchange_malloc"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
     match Global.allocate(layout) {

alloc/src/boxed.rs

@@ -250,6 +250,7 @@ impl<T> Box<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
     #[rustc_diagnostic_item = "box_new"]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub fn new(x: T) -> Self {
         #[rustc_box]
         Box::new(x)

alloc/src/collections/vec_deque/mod.rs

@@ -554,8 +554,8 @@ impl<T> VecDeque<T> {
     #[rustc_const_stable(feature = "const_vec_deque_new", since = "1.68.0")]
     #[must_use]
     pub const fn new() -> VecDeque<T> {
-        // FIXME: This should just be `VecDeque::new_in(Global)` once that hits stable.
-        VecDeque { head: 0, len: 0, buf: RawVec::NEW }
+        // FIXME(const-hack): This should just be `VecDeque::new_in(Global)` once that hits stable.
+        VecDeque { head: 0, len: 0, buf: RawVec::new() }
     }
 
     /// Creates an empty deque with space for at least `capacity` elements.

alloc/src/raw_vec.rs

@@ -96,13 +96,6 @@ struct RawVecInner<A: Allocator = Global> {
 }
 
 impl<T> RawVec<T, Global> {
-    /// HACK(Centril): This exists because stable `const fn` can only call stable `const fn`, so
-    /// they cannot call `Self::new()`.
-    ///
-    /// If you change `RawVec<T>::new` or dependencies, please take care to not introduce anything
-    /// that would truly const-call something unstable.
-    pub const NEW: Self = Self::new();
-
     /// Creates the biggest possible `RawVec` (on the system heap)
     /// without allocating. If `T` has positive size, then this makes a
     /// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a
@@ -111,7 +104,7 @@ impl<T> RawVec<T, Global> {
     #[must_use]
     #[rustc_const_stable(feature = "raw_vec_internals_const", since = "1.81")]
     pub const fn new() -> Self {
-        Self { inner: RawVecInner::new::<T>(), _marker: PhantomData }
+        Self::new_in(Global)
     }
 
     /// Creates a `RawVec` (on the system heap) with exactly the
@@ -149,12 +142,6 @@ impl<T> RawVec<T, Global> {
 }
 
 impl RawVecInner<Global> {
-    #[must_use]
-    #[rustc_const_stable(feature = "raw_vec_internals_const", since = "1.81")]
-    const fn new<T>() -> Self {
-        Self::new_in(Global, core::mem::align_of::<T>())
-    }
-
     #[cfg(not(any(no_global_oom_handling, test)))]
     #[must_use]
     #[inline]

alloc/src/vec/in_place_collect.rs

@@ -191,7 +191,7 @@ const fn in_place_collectible<DEST, SRC>(
 
 const fn needs_realloc<SRC, DEST>(src_cap: usize, dst_cap: usize) -> bool {
     if const { mem::align_of::<SRC>() != mem::align_of::<DEST>() } {
-        // FIXME: use unreachable! once that works in const
+        // FIXME(const-hack): use unreachable! once that works in const
         panic!("in_place_collectible() prevents this");
     }
 

alloc/src/vec/into_iter.rs

@@ -142,7 +142,7 @@ impl<T, A: Allocator> IntoIter<T, A> {
         // struct and then overwriting &mut self.
         // this creates less assembly
         self.cap = 0;
-        self.buf = RawVec::NEW.non_null();
+        self.buf = RawVec::new().non_null();
         self.ptr = self.buf;
         self.end = self.buf.as_ptr();
 

alloc/src/vec/mod.rs

@@ -419,7 +419,7 @@ impl<T> Vec<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use]
     pub const fn new() -> Self {
-        Vec { buf: RawVec::NEW, len: 0 }
+        Vec { buf: RawVec::new(), len: 0 }
     }
 
     /// Constructs a new, empty `Vec<T>` with at least the specified capacity.

core/src/char/convert.rs

@@ -11,7 +11,7 @@ use crate::ub_checks::assert_unsafe_precondition;
 #[must_use]
 #[inline]
 pub(super) const fn from_u32(i: u32) -> Option<char> {
-    // FIXME: once Result::ok is const fn, use it here
+    // FIXME(const-hack): once Result::ok is const fn, use it here
     match char_try_from_u32(i) {
         Ok(c) => Some(c),
         Err(_) => None,

core/src/char/methods.rs

@@ -383,7 +383,7 @@ impl char {
             // Force the 6th bit to be set to ensure ascii is lower case.
             digit = (self as u32 | 0b10_0000).wrapping_sub('a' as u32).saturating_add(10);
         }
-        // FIXME: once then_some is const fn, use it here
+        // FIXME(const-hack): once then_some is const fn, use it here
         if digit < radix { Some(digit) } else { None }
     }
 

core/src/lib.rs

@@ -149,7 +149,6 @@
 #![feature(const_size_of_val_raw)]
 #![feature(const_slice_from_raw_parts_mut)]
 #![feature(const_slice_from_ref)]
-#![feature(const_slice_index)]
 #![feature(const_slice_split_at_mut)]
 #![feature(const_str_from_utf8_unchecked_mut)]
 #![feature(const_strict_overflow_ops)]

core/src/num/mod.rs

@@ -6,7 +6,7 @@ use crate::str::FromStr;
 use crate::ub_checks::assert_unsafe_precondition;
 use crate::{ascii, intrinsics, mem};
 
-// Used because the `?` operator is not allowed in a const context.
+// FIXME(const-hack): Used because the `?` operator is not allowed in a const context.
 macro_rules! try_opt {
     ($e:expr) => {
         match $e {

core/src/option.rs

@@ -739,6 +739,7 @@ impl<T> Option<T> {
     #[stable(feature = "pin", since = "1.33.0")]
     #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
     pub const fn as_pin_ref(self: Pin<&Self>) -> Option<Pin<&T>> {
+        // FIXME(const-hack): use `map` once that is possible
         match Pin::get_ref(self).as_ref() {
             // SAFETY: `x` is guaranteed to be pinned because it comes from `self`
             // which is pinned.
@@ -758,6 +759,7 @@ impl<T> Option<T> {
         // SAFETY: `get_unchecked_mut` is never used to move the `Option` inside `self`.
         // `x` is guaranteed to be pinned because it comes from `self` which is pinned.
         unsafe {
+            // FIXME(const-hack): use `map` once that is possible
             match Pin::get_unchecked_mut(self).as_mut() {
                 Some(x) => Some(Pin::new_unchecked(x)),
                 None => None,
@@ -1290,10 +1292,7 @@ impl<T> Option<T> {
     where
         T: Deref,
     {
-        match self.as_ref() {
-            Some(t) => Some(t.deref()),
-            None => None,
-        }
+        self.as_ref().map(|t| t.deref())
     }
 
     /// Converts from `Option<T>` (or `&mut Option<T>`) to `Option<&mut T::Target>`.
@@ -1316,10 +1315,7 @@ impl<T> Option<T> {
     where
         T: DerefMut,
     {
-        match self.as_mut() {
-            Some(t) => Some(t.deref_mut()),
-            None => None,
-        }
+        self.as_mut().map(|t| t.deref_mut())
     }
 
     /////////////////////////////////////////////////////////////////////////
@@ -1632,13 +1628,7 @@ impl<T> Option<T> {
     #[inline]
     #[stable(feature = "option_entry", since = "1.20.0")]
     pub fn get_or_insert(&mut self, value: T) -> &mut T {
-        if let None = *self {
-            *self = Some(value);
-        }
-
-        // SAFETY: a `None` variant for `self` would have been replaced by a `Some`
-        // variant in the code above.
-        unsafe { self.as_mut().unwrap_unchecked() }
+        self.get_or_insert_with(|| value)
     }
 
     /// Inserts the default value into the option if it is [`None`], then
@@ -1724,7 +1714,7 @@ impl<T> Option<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_option", issue = "67441")]
     pub const fn take(&mut self) -> Option<T> {
-        // FIXME replace `mem::replace` by `mem::take` when the latter is const ready
+        // FIXME(const-hack) replace `mem::replace` by `mem::take` when the latter is const ready
         mem::replace(self, None)
     }
 

core/src/panic.rs

@@ -140,6 +140,31 @@ pub macro unreachable_2021 {
     ),
 }
 
+/// Invokes a closure, aborting if the closure unwinds.
+///
+/// When compiled with aborting panics, this function is effectively a no-op.
+/// With unwinding panics, an unwind results in another call into the panic
+/// hook followed by a process abort.
+///
+/// # Notes
+///
+/// Instead of using this function, code should attempt to support unwinding.
+/// Implementing [`Drop`] allows you to restore invariants uniformly in both
+/// return and unwind paths.
+///
+/// If an unwind can lead to logical issues but not soundness issues, you
+/// should allow the unwind. Opting out of [`UnwindSafe`] indicates to your
+/// consumers that they need to consider correctness in the face of unwinds.
+///
+/// If an unwind would be unsound, then this function should be used in order
+/// to prevent unwinds. However, note that `extern "C" fn` will automatically
+/// convert unwinds to aborts, so using this function isn't necessary for FFI.
+#[unstable(feature = "abort_unwind", issue = "130338")]
+#[rustc_nounwind]
+pub fn abort_unwind<F: FnOnce() -> R, R>(f: F) -> R {
+    f()
+}
+
 /// An internal trait used by std to pass data from std to `panic_unwind` and
 /// other panic runtimes. Not intended to be stabilized any time soon, do not
 /// use.

core/src/ptr/alignment.rs

@@ -199,7 +199,6 @@ impl From<Alignment> for usize {
     }
 }
 
-#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
 impl cmp::Ord for Alignment {
     #[inline]
@@ -208,7 +207,6 @@ impl cmp::Ord for Alignment {
     }
 }
 
-#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
 impl cmp::PartialOrd for Alignment {
     #[inline]