Merge from rustc

Author: The Miri Cronjob Bot

alloc/src/alloc.rs

@@ -10,25 +10,28 @@ use core::ptr::{self, NonNull};
 
 unsafe extern "Rust" {
     // These are the magic symbols to call the global allocator. rustc generates
-    // them to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
+    // them to call the global allocator if there is a `#[global_allocator]` attribute
     // (the code expanding that attribute macro generates those functions), or to call
     // the default implementations in std (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)
     // otherwise.
-    // The rustc fork of LLVM 14 and earlier also special-cases these function names to be able to optimize them
-    // like `malloc`, `realloc`, and `free`, respectively.
     #[rustc_allocator]
     #[rustc_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
     fn __rust_alloc(size: usize, align: usize) -> *mut u8;
     #[rustc_deallocator]
     #[rustc_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
     fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
     #[rustc_reallocator]
     #[rustc_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
     fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
     #[rustc_allocator_zeroed]
     #[rustc_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
     fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
 
+    #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
     static __rust_no_alloc_shim_is_unstable: u8;
 }
 
@@ -357,6 +360,7 @@ unsafe extern "Rust" {
     // This is the magic symbol to call the global alloc error handler. rustc generates
     // it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the
     // default implementations below (`__rdl_oom`) otherwise.
+    #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
     fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
 }
 
@@ -423,6 +427,7 @@ pub mod __alloc_error_handler {
         unsafe extern "Rust" {
             // This symbol is emitted by rustc next to __rust_alloc_error_handler.
             // Its value depends on the -Zoom={panic,abort} compiler option.
+            #[cfg_attr(not(bootstrap), rustc_std_internal_symbol)]
             static __rust_alloc_error_handler_should_panic: u8;
         }
 

alloc/src/rc.rs

@@ -1327,11 +1327,14 @@ impl<T: ?Sized> Rc<T> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Rc::into_raw`, the
-    /// associated `Rc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Rc::into_raw` and must satisfy the
+    /// same layout requirements specified in [`Rc::from_raw_in`][from_raw_in].
+    /// The associated `Rc` instance must be valid (i.e. the strong count must be at
     /// least 1) for the duration of this method, and `ptr` must point to a block of memory
     /// allocated by the global allocator.
     ///
+    /// [from_raw_in]: Rc::from_raw_in
+    ///
     /// # Examples
     ///
     /// ```
@@ -1360,12 +1363,15 @@ impl<T: ?Sized> Rc<T> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Rc::into_raw`, the
-    /// associated `Rc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Rc::into_raw`and must satisfy the
+    /// same layout requirements specified in [`Rc::from_raw_in`][from_raw_in].
+    /// The associated `Rc` instance must be valid (i.e. the strong count must be at
     /// least 1) when invoking this method, and `ptr` must point to a block of memory
     /// allocated by the global allocator. This method can be used to release the final `Rc` and
     /// backing storage, but **should not** be called after the final `Rc` has been released.
     ///
+    /// [from_raw_in]: Rc::from_raw_in
+    ///
     /// # Examples
     ///
     /// ```
@@ -1623,10 +1629,13 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Rc::into_raw`, the
-    /// associated `Rc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Rc::into_raw` and must satisfy the
+    /// same layout requirements specified in [`Rc::from_raw_in`][from_raw_in].
+    /// The associated `Rc` instance must be valid (i.e. the strong count must be at
     /// least 1) for the duration of this method, and `ptr` must point to a block of memory
-    /// allocated by `alloc`
+    /// allocated by `alloc`.
+    ///
+    /// [from_raw_in]: Rc::from_raw_in
     ///
     /// # Examples
     ///
@@ -1665,11 +1674,14 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Rc::into_raw`, the
-    /// associated `Rc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Rc::into_raw`and must satisfy the
+    /// same layout requirements specified in [`Rc::from_raw_in`][from_raw_in].
+    /// The associated `Rc` instance must be valid (i.e. the strong count must be at
     /// least 1) when invoking this method, and `ptr` must point to a block of memory
-    /// allocated by `alloc`. This method can be used to release the final `Rc` and backing storage,
-    /// but **should not** be called after the final `Rc` has been released.
+    /// allocated by `alloc`. This method can be used to release the final `Rc` and
+    /// backing storage, but **should not** be called after the final `Rc` has been released.
+    ///
+    /// [from_raw_in]: Rc::from_raw_in
     ///
     /// # Examples
     ///

alloc/src/sync.rs

@@ -84,9 +84,29 @@ macro_rules! acquire {
 ///
 /// Shared references in Rust disallow mutation by default, and `Arc` is no
 /// exception: you cannot generally obtain a mutable reference to something
-/// inside an `Arc`. If you need to mutate through an `Arc`, use
-/// [`Mutex`][mutex], [`RwLock`][rwlock], or one of the [`Atomic`][atomic]
-/// types.
+/// inside an `Arc`. If you do need to mutate through an `Arc`, you have several options:
+///
+/// 1. Use interior mutability with synchronization primitives like [`Mutex`][mutex],
+///    [`RwLock`][rwlock], or one of the [`Atomic`][atomic] types.
+///
+/// 2. Use clone-on-write semantics with [`Arc::make_mut`] which provides efficient mutation
+///    without requiring interior mutability. This approach clones the data only when
+///    needed (when there are multiple references) and can be more efficient when mutations
+///    are infrequent.
+///
+/// 3. Use [`Arc::get_mut`] when you know your `Arc` is not shared (has a reference count of 1),
+///    which provides direct mutable access to the inner value without any cloning.
+///
+/// ```
+/// use std::sync::Arc;
+///
+/// let mut data = Arc::new(vec![1, 2, 3]);
+///
+/// // This will clone the vector only if there are other references to it
+/// Arc::make_mut(&mut data).push(4);
+///
+/// assert_eq!(*data, vec![1, 2, 3, 4]);
+/// ```
 ///
 /// **Note**: This type is only available on platforms that support atomic
 /// loads and stores of pointers, which includes all platforms that support
@@ -1453,11 +1473,14 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Arc::into_raw`, and the
-    /// associated `Arc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Arc::into_raw` and must satisfy the
+    /// same layout requirements specified in [`Arc::from_raw_in`][from_raw_in].
+    /// The associated `Arc` instance must be valid (i.e. the strong count must be at
     /// least 1) for the duration of this method, and `ptr` must point to a block of memory
     /// allocated by the global allocator.
     ///
+    /// [from_raw_in]: Arc::from_raw_in
+    ///
     /// # Examples
     ///
     /// ```
@@ -1488,13 +1511,16 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Arc::into_raw`, and the
-    /// associated `Arc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Arc::into_raw` and must satisfy the
+    /// same layout requirements specified in [`Arc::from_raw_in`][from_raw_in].
+    /// The associated `Arc` instance must be valid (i.e. the strong count must be at
     /// least 1) when invoking this method, and `ptr` must point to a block of memory
     /// allocated by the global allocator. This method can be used to release the final
     /// `Arc` and backing storage, but **should not** be called after the final `Arc` has been
     /// released.
     ///
+    /// [from_raw_in]: Arc::from_raw_in
+    ///
     /// # Examples
     ///
     /// ```
@@ -1806,11 +1832,14 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Arc::into_raw`, and the
-    /// associated `Arc` instance must be valid (i.e. the strong count must be at
-    /// least 1) for the duration of this method,, and `ptr` must point to a block of memory
+    /// The pointer must have been obtained through `Arc::into_raw` and must satisfy the
+    /// same layout requirements specified in [`Arc::from_raw_in`][from_raw_in].
+    /// The associated `Arc` instance must be valid (i.e. the strong count must be at
+    /// least 1) for the duration of this method, and `ptr` must point to a block of memory
     /// allocated by `alloc`.
     ///
+    /// [from_raw_in]: Arc::from_raw_in
+    ///
     /// # Examples
     ///
     /// ```
@@ -1850,13 +1879,16 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     ///
     /// # Safety
     ///
-    /// The pointer must have been obtained through `Arc::into_raw`,  the
-    /// associated `Arc` instance must be valid (i.e. the strong count must be at
+    /// The pointer must have been obtained through `Arc::into_raw` and must satisfy the
+    /// same layout requirements specified in [`Arc::from_raw_in`][from_raw_in].
+    /// The associated `Arc` instance must be valid (i.e. the strong count must be at
     /// least 1) when invoking this method, and `ptr` must point to a block of memory
     /// allocated by `alloc`. This method can be used to release the final
     /// `Arc` and backing storage, but **should not** be called after the final `Arc` has been
     /// released.
     ///
+    /// [from_raw_in]: Arc::from_raw_in
+    ///
     /// # Examples
     ///
     /// ```

alloc/src/vec/mod.rs

@@ -1252,6 +1252,19 @@ impl<T, A: Allocator> Vec<T, A> {
     /// vec.push(42);
     /// assert!(vec.capacity() >= 10);
     /// ```
+    ///
+    /// A vector with zero-sized elements will always have a capacity of usize::MAX:
+    ///
+    /// ```
+    /// #[derive(Clone)]
+    /// struct ZeroSized;
+    ///
+    /// fn main() {
+    ///     assert_eq!(std::mem::size_of::<ZeroSized>(), 0);
+    ///     let v = vec![ZeroSized; 0];
+    ///     assert_eq!(v.capacity(), usize::MAX);
+    /// }
+    /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_vec_string_slice", since = "CURRENT_RUSTC_VERSION")]

core/src/any.rs

@@ -109,7 +109,7 @@ use crate::{fmt, hash, intrinsics};
 // unsafe traits and unsafe methods (i.e., `type_id` would still be safe to call,
 // but we would likely want to indicate as such in documentation).
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg_attr(not(test), rustc_diagnostic_item = "Any")]
+#[rustc_diagnostic_item = "Any"]
 pub trait Any: 'static {
     /// Gets the `TypeId` of `self`.
     ///

core/src/array/ascii.rs

@@ -1,6 +1,5 @@
 use crate::ascii;
 
-#[cfg(not(test))]
 impl<const N: usize> [u8; N] {
     /// Converts this array of bytes into an array of ASCII characters,
     /// or returns `None` if any of the characters is non-ASCII.

core/src/bool.rs

@@ -56,7 +56,7 @@ impl bool {
     /// ```
     #[doc(alias = "then_with")]
     #[stable(feature = "lazy_bool_to_option", since = "1.50.0")]
-    #[cfg_attr(not(test), rustc_diagnostic_item = "bool_then")]
+    #[rustc_diagnostic_item = "bool_then"]
     #[inline]
     pub fn then<T, F: FnOnce() -> T>(self, f: F) -> Option<T> {
         if self { Some(f()) } else { None }

core/src/cell.rs

@@ -304,7 +304,7 @@ pub use once::OnceCell;
 /// ```
 ///
 /// See the [module-level documentation](self) for more.
-#[cfg_attr(not(test), rustc_diagnostic_item = "Cell")]
+#[rustc_diagnostic_item = "Cell"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[repr(transparent)]
 #[rustc_pub_transparent]
@@ -725,7 +725,7 @@ impl<T, const N: usize> Cell<[T; N]> {
 /// A mutable memory location with dynamically checked borrow rules
 ///
 /// See the [module-level documentation](self) for more.
-#[cfg_attr(not(test), rustc_diagnostic_item = "RefCell")]
+#[rustc_diagnostic_item = "RefCell"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RefCell<T: ?Sized> {
     borrow: Cell<BorrowFlag>,

core/src/char/methods.rs

@@ -1178,7 +1178,7 @@ impl char {
     #[must_use]
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
     #[rustc_const_stable(feature = "const_char_is_ascii", since = "1.32.0")]
-    #[cfg_attr(not(test), rustc_diagnostic_item = "char_is_ascii")]
+    #[rustc_diagnostic_item = "char_is_ascii"]
     #[inline]
     pub const fn is_ascii(&self) -> bool {
         *self as u32 <= 0x7F