Merge subtree update for toolchain nightly-2025-03-13 (#274)

This is an automated PR to merge library subtree updates
from 2025-02-11 (6171d94)
to 2025-03-13 (249cb84) (inclusive)
into main. `git merge` resulted in conflicts, which require manual
resolution.
Files were commited with merge conflict markers.

---------

Co-authored-by: gitbot <git@bot>
Co-authored-by: Michael Tautschnig <tautschn@amazon.com>

Author: 3 people

library/Cargo.lock

@@ -4,6 +4,7 @@ members = [
   "std",
   "sysroot",
   "coretests",
+  "alloctests",
 ]
 
 exclude = [

library/Cargo.toml

@@ -1,3 +1,5 @@
+cargo-features = ["public-dependency"]
+
 [package]
 name = "alloc"
 version = "0.0.0"
@@ -8,33 +10,15 @@ autotests = false
 autobenches = false
 edition = "2021"
 
+[lib]
+test = false
+bench = false
+
 [dependencies]
-core = { path = "../core" }
-compiler_builtins = { version = "=0.1.145", features = ['rustc-dep-of-std'] }
+core = { path = "../core", public = true }
+compiler_builtins = { version = "=0.1.151", features = ['rustc-dep-of-std'] }
 safety = { path = "../contracts/safety" }
 
-[dev-dependencies]
-rand = { version = "0.8.5", default-features = false, features = ["alloc"] }
-rand_xorshift = "0.3.0"
-
-[[test]]
-name = "alloctests"
-path = "tests/lib.rs"
-
-[[test]]
-name = "vec_deque_alloc_error"
-path = "tests/vec_deque_alloc_error.rs"
-
-[[bench]]
-name = "allocbenches"
-path = "benches/lib.rs"
-test = true
-
-[[bench]]
-name = "vec_deque_append_bench"
-path = "benches/vec_deque_append.rs"
-harness = false
-
 [features]
 compiler-builtins-mem = ['compiler_builtins/mem']
 compiler-builtins-c = ["compiler_builtins/c"]

library/alloc/Cargo.toml

@@ -5,12 +5,10 @@
 #[stable(feature = "alloc_module", since = "1.28.0")]
 #[doc(inline)]
 pub use core::alloc::*;
-#[cfg(not(test))]
 use core::hint;
-#[cfg(not(test))]
 use core::ptr::{self, NonNull};
 
-extern "Rust" {
+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
     // (the code expanding that attribute macro generates those functions), or to call
@@ -44,14 +42,10 @@ extern "Rust" {
 /// accessed through the [free functions in `alloc`](self#functions).
 #[unstable(feature = "allocator_api", issue = "32838")]
 #[derive(Copy, Clone, Default, Debug)]
-#[cfg(not(test))]
 // the compiler needs to know when a Box uses the global allocator vs a custom one
 #[lang = "global_alloc_ty"]
 pub struct Global;
 
-#[cfg(test)]
-pub use std::alloc::Global;
-
 /// Allocates memory with the global allocator.
 ///
 /// This function forwards calls to the [`GlobalAlloc::alloc`] method
@@ -180,7 +174,6 @@ pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
     }
 }
 
-#[cfg(not(test))]
 impl Global {
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
@@ -246,7 +239,6 @@ impl Global {
 }
 
 #[unstable(feature = "allocator_api", issue = "32838")]
-#[cfg(not(test))]
 unsafe impl Allocator for Global {
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
@@ -264,8 +256,14 @@ unsafe impl Allocator for Global {
     #[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,
-            // other conditions must be upheld by the caller
+            // SAFETY:
+            // * We have checked that `layout` is non-zero in size.
+            // * The caller is obligated to provide a layout that "fits", and in this case,
+            //   "fit" always means a layout that is equal to the original, because our
+            //   `allocate()`, `grow()`, and `shrink()` implementations never returns a larger
+            //   allocation than requested.
+            // * Other conditions must be upheld by the caller, as per `Allocator::deallocate()`'s
+            //   safety documentation.
             unsafe { dealloc(ptr.as_ptr(), layout) }
         }
     }
@@ -340,7 +338,7 @@ unsafe impl Allocator for Global {
 }
 
 /// The allocator for `Box`.
-#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[cfg(not(no_global_oom_handling))]
 #[lang = "exchange_malloc"]
 #[inline]
 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
@@ -355,7 +353,7 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
 // # Allocation error handler
 
 #[cfg(not(no_global_oom_handling))]
-extern "Rust" {
+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.
@@ -389,7 +387,7 @@ extern "Rust" {
 /// [no_std]: https://doc.rust-lang.org/reference/names/preludes.html#the-no_std-attribute
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]
-#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[cfg(not(no_global_oom_handling))]
 #[cold]
 #[optimize(size)]
 pub const fn handle_alloc_error(layout: Layout) -> ! {
@@ -413,11 +411,7 @@ pub const fn handle_alloc_error(layout: Layout) -> ! {
     ct_error(layout)
 }
 
-// For alloc test `std::alloc::handle_alloc_error` can be used directly.
-#[cfg(all(not(no_global_oom_handling), test))]
-pub use std::alloc::handle_alloc_error;
-
-#[cfg(all(not(no_global_oom_handling), not(test)))]
+#[cfg(not(no_global_oom_handling))]
 #[doc(hidden)]
 #[allow(unused_attributes)]
 #[unstable(feature = "alloc_internals", issue = "none")]
@@ -426,7 +420,7 @@ pub mod __alloc_error_handler {
     // `#[alloc_error_handler]`.
     #[rustc_std_internal_symbol]
     pub unsafe fn __rdl_oom(size: usize, _align: usize) -> ! {
-        extern "Rust" {
+        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.
             static __rust_alloc_error_handler_should_panic: u8;

library/alloc/src/alloc.rs

@@ -32,7 +32,7 @@ where
 /// implementing the `Clone` trait. But `Clone` works only for going from `&T`
 /// to `T`. The `ToOwned` trait generalizes `Clone` to construct owned data
 /// from any borrow of a given type.
-#[cfg_attr(not(test), rustc_diagnostic_item = "ToOwned")]
+#[rustc_diagnostic_item = "ToOwned"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait ToOwned {
     /// The resulting type after obtaining ownership.
@@ -54,7 +54,7 @@ pub trait ToOwned {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[must_use = "cloning is often expensive and is not expected to have side effects"]
-    #[cfg_attr(not(test), rustc_diagnostic_item = "to_owned_method")]
+    #[rustc_diagnostic_item = "to_owned_method"]
     fn to_owned(&self) -> Self::Owned;
 
     /// Uses borrowed data to replace owned data, usually by cloning.
@@ -175,7 +175,7 @@ where
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg_attr(not(test), rustc_diagnostic_item = "Cow")]
+#[rustc_diagnostic_item = "Cow"]
 pub enum Cow<'a, B: ?Sized + 'a>
 where
     B: ToOwned,
@@ -340,8 +340,18 @@ where
     }
 }
 
+// `Cow<'_, T>` can only implement `DerefPure` if `<T::Owned as Borrow<T>>` (and `BorrowMut<T>`) is trusted.
+// For now, we restrict `DerefPure for Cow<T>` to `T: Sized` (`T as Borrow<T>` is trusted),
+// `str` (`String as Borrow<str>` is trusted) and `[T]` (`Vec<T> as Borrow<[T]>` is trusted).
+// In the future, a `BorrowPure<T>` trait analogous to `DerefPure` might generalize this.
 #[unstable(feature = "deref_pure_trait", issue = "87121")]
-unsafe impl<B: ?Sized + ToOwned> DerefPure for Cow<'_, B> where B::Owned: Borrow<B> {}
+unsafe impl<T: Clone> DerefPure for Cow<'_, T> {}
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "deref_pure_trait", issue = "87121")]
+unsafe impl DerefPure for Cow<'_, str> {}
+#[cfg(not(no_global_oom_handling))]
+#[unstable(feature = "deref_pure_trait", issue = "87121")]
+unsafe impl<T: Clone> DerefPure for Cow<'_, [T]> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {}