Auto merge of rust-lang#125552 - matthiaskrgr:rollup-f1yybpn, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#121377 (Stabilize `LazyCell` and `LazyLock`)
 - rust-lang#122986 (Fix c_char on AIX)
 - rust-lang#123803 (Fix `VecDeque::shrink_to` UB when `handle_alloc_error` unwinds.)
 - rust-lang#124080 (Some unstable changes to where opaque types get defined)
 - rust-lang#124667 (Stabilize `div_duration`)
 - rust-lang#125472 (tidy: validate LLVM component names in tests)
 - rust-lang#125523 (Exit the process a short time after entering our ctrl-c handler)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -309,7 +309,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
         }
 
         if let ConstContext::Static(_) = ccx.const_kind() {
-            err.note("consider wrapping this expression in `Lazy::new(|| ...)` from the `once_cell` crate: https://crates.io/crates/once_cell");
+            err.note("consider wrapping this expression in `std::sync::LazyLock::new(|| ...)`");
         }
 
         err

compiler/rustc_data_structures/src/lib.rs

@@ -24,7 +24,6 @@
 #![feature(extend_one)]
 #![feature(hash_raw_entry)]
 #![feature(hasher_prefixfree_extras)]
-#![feature(lazy_cell)]
 #![feature(lint_reasons)]
 #![feature(macro_metavar_expr)]
 #![feature(map_try_insert)]

compiler/rustc_driver_impl/src/lib.rs

@@ -57,7 +57,7 @@ use std::process::{self, Command, Stdio};
 use std::str;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, OnceLock};
-use std::time::{Instant, SystemTime};
+use std::time::{Duration, Instant, SystemTime};
 use time::OffsetDateTime;
 use tracing::trace;
 
@@ -1502,14 +1502,13 @@ pub fn init_logger(early_dcx: &EarlyDiagCtxt, cfg: rustc_log::LoggerConfig) {
 pub fn install_ctrlc_handler() {
     #[cfg(not(target_family = "wasm"))]
     ctrlc::set_handler(move || {
-        // Indicate that we have been signaled to stop. If we were already signaled, exit
-        // immediately. In our interpreter loop we try to consult this value often, but if for
-        // whatever reason we don't get to that check or the cleanup we do upon finding that
-        // this bool has become true takes a long time, the exit here will promptly exit the
-        // process on the second Ctrl-C.
-        if CTRL_C_RECEIVED.swap(true, Ordering::Relaxed) {
-            std::process::exit(1);
-        }
+        // Indicate that we have been signaled to stop, then give the rest of the compiler a bit of
+        // time to check CTRL_C_RECEIVED and run its own shutdown logic, but after a short amount
+        // of time exit the process. This sleep+exit ensures that even if nobody is checking
+        // CTRL_C_RECEIVED, the compiler exits reasonably promptly.
+        CTRL_C_RECEIVED.store(true, Ordering::Relaxed);
+        std::thread::sleep(Duration::from_millis(100));
+        std::process::exit(1);
     })
     .expect("Unable to install ctrlc handler");
 }

compiler/rustc_error_messages/src/lib.rs

@@ -1,6 +1,5 @@
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
-#![feature(lazy_cell)]
 #![feature(rustc_attrs)]
 #![feature(type_alias_impl_trait)]
 #![allow(internal_features)]

compiler/rustc_feature/src/lib.rs

@@ -14,7 +14,6 @@
 #![allow(internal_features)]
 #![feature(rustdoc_internals)]
 #![doc(rust_logo)]
-#![feature(lazy_cell)]
 
 mod accepted;
 mod builtin_attrs;

compiler/rustc_hir_analysis/src/lib.rs

@@ -68,7 +68,6 @@ This API is completely unstable and subject to change.
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
 #![feature(never_type)]
-#![feature(lazy_cell)]
 #![feature(slice_partition_dedup)]
 #![feature(try_blocks)]
 

compiler/rustc_interface/src/lib.rs

@@ -1,5 +1,4 @@
 #![feature(decl_macro)]
-#![feature(lazy_cell)]
 #![feature(let_chains)]
 #![feature(thread_spawn_unchecked)]
 #![feature(try_blocks)]

compiler/rustc_lint_defs/src/builtin.rs

@@ -1316,10 +1316,8 @@ declare_lint! {
     /// * If you are trying to perform a one-time initialization of a global:
     ///     * If the value can be computed at compile-time, consider using
     ///       const-compatible values (see [Constant Evaluation]).
-    ///     * For more complex single-initialization cases, consider using a
-    ///       third-party crate, such as [`lazy_static`] or [`once_cell`].
-    ///     * If you are using the [nightly channel], consider the new
-    ///       [`lazy`] module in the standard library.
+    ///     * For more complex single-initialization cases, consider using
+    ///       [`std::sync::LazyLock`].
     /// * If you truly need a mutable global, consider using a [`static`],
     ///   which has a variety of options:
     ///   * Simple data types can be directly defined and mutated with an
@@ -1334,9 +1332,7 @@ declare_lint! {
     /// [Constant Evaluation]: https://doc.rust-lang.org/reference/const_eval.html
     /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
     /// [mutable `static`]: https://doc.rust-lang.org/reference/items/static-items.html#mutable-statics
-    /// [`lazy`]: https://doc.rust-lang.org/nightly/std/lazy/index.html
-    /// [`lazy_static`]: https://crates.io/crates/lazy_static
-    /// [`once_cell`]: https://crates.io/crates/once_cell
+    /// [`std::sync::LazyLock`]: https://doc.rust-lang.org/stable/std/sync/struct.LazyLock.html
     /// [`atomic`]: https://doc.rust-lang.org/std/sync/atomic/index.html
     /// [`Mutex`]: https://doc.rust-lang.org/std/sync/struct.Mutex.html
     pub CONST_ITEM_MUTATION,

compiler/rustc_session/src/lib.rs

@@ -1,5 +1,4 @@
 #![feature(let_chains)]
-#![feature(lazy_cell)]
 #![feature(option_get_or_insert_default)]
 #![feature(rustc_attrs)]
 #![feature(map_many_mut)]

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2539,7 +2539,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         let InferOk { obligations, .. } = self
             .infcx
             .at(&cause, obligation.param_env)
-            .eq(DefineOpaqueTypes::No, placeholder_obligation_trait_ref, impl_trait_ref)
+            .eq(DefineOpaqueTypes::Yes, placeholder_obligation_trait_ref, impl_trait_ref)
             .map_err(|e| {
                 debug!("match_impl: failed eq_trait_refs due to `{}`", e.to_string(self.tcx()))
             })?;
@@ -2594,7 +2594,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                         self.infcx
                             .at(&obligation.cause, obligation.param_env)
                             .eq(
-                                DefineOpaqueTypes::No,
+                                DefineOpaqueTypes::Yes,
                                 upcast_principal.map_bound(|trait_ref| {
                                     ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
                                 }),
@@ -2631,7 +2631,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                     nested.extend(
                         self.infcx
                             .at(&obligation.cause, obligation.param_env)
-                            .eq(DefineOpaqueTypes::No, source_projection, target_projection)
+                            .eq(DefineOpaqueTypes::Yes, source_projection, target_projection)
                             .map_err(|_| SelectionError::Unimplemented)?
                             .into_obligations(),
                     );

library/alloc/Cargo.toml

@@ -20,6 +20,10 @@ rand_xorshift = "0.3.0"
 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"

library/alloc/src/collections/vec_deque/mod.rs

@@ -982,6 +982,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
         // `head` and `len` are at most `isize::MAX` and `target_cap < self.capacity()`, so nothing can
         // overflow.
         let tail_outside = (target_cap + 1..=self.capacity()).contains(&(self.head + self.len));
+        // Used in the drop guard below.
+        let old_head = self.head;
 
         if self.len == 0 {
             self.head = 0;
@@ -1034,12 +1036,74 @@ impl<T, A: Allocator> VecDeque<T, A> {
             }
             self.head = new_head;
         }
-        self.buf.shrink_to_fit(target_cap);
+
+        struct Guard<'a, T, A: Allocator> {
+            deque: &'a mut VecDeque<T, A>,
+            old_head: usize,
+            target_cap: usize,
+        }
+
+        impl<T, A: Allocator> Drop for Guard<'_, T, A> {
+            #[cold]
+            fn drop(&mut self) {
+                unsafe {
+                    // SAFETY: This is only called if `buf.shrink_to_fit` unwinds,
+                    // which is the only time it's safe to call `abort_shrink`.
+                    self.deque.abort_shrink(self.old_head, self.target_cap)
+                }
+            }
+        }
+
+        let guard = Guard { deque: self, old_head, target_cap };
+
+        guard.deque.buf.shrink_to_fit(target_cap);
+
+        // Don't drop the guard if we didn't unwind.
+        mem::forget(guard);
 
         debug_assert!(self.head < self.capacity() || self.capacity() == 0);
         debug_assert!(self.len <= self.capacity());
     }
 
+    /// Reverts the deque back into a consistent state in case `shrink_to` failed.
+    /// This is necessary to prevent UB if the backing allocator returns an error
+    /// from `shrink` and `handle_alloc_error` subsequently unwinds (see #123369).
+    ///
+    /// `old_head` refers to the head index before `shrink_to` was called. `target_cap`
+    /// is the capacity that it was trying to shrink to.
+    unsafe fn abort_shrink(&mut self, old_head: usize, target_cap: usize) {
+        // Moral equivalent of self.head + self.len <= target_cap. Won't overflow
+        // because `self.len <= target_cap`.
+        if self.head <= target_cap - self.len {
+            // The deque's buffer is contiguous, so no need to copy anything around.
+            return;
+        }
+
+        // `shrink_to` already copied the head to fit into the new capacity, so this won't overflow.
+        let head_len = target_cap - self.head;
+        // `self.head > target_cap - self.len` => `self.len > target_cap - self.head =: head_len` so this must be positive.
+        let tail_len = self.len - head_len;
+
+        if tail_len <= cmp::min(head_len, self.capacity() - target_cap) {
+            // There's enough spare capacity to copy the tail to the back (because `tail_len < self.capacity() - target_cap`),
+            // and copying the tail should be cheaper than copying the head (because `tail_len <= head_len`).
+
+            unsafe {
+                // The old tail and the new tail can't overlap because the head slice lies between them. The
+                // head slice ends at `target_cap`, so that's where we copy to.
+                self.copy_nonoverlapping(0, target_cap, tail_len);
+            }
+        } else {
+            // Either there's not enough spare capacity to make the deque contiguous, or the head is shorter than the tail
+            // (and therefore hopefully cheaper to copy).
+            unsafe {
+                // The old and the new head slice can overlap, so we can't use `copy_nonoverlapping` here.
+                self.copy(self.head, old_head, head_len);
+                self.head = old_head;
+            }
+        }
+    }
+
     /// Shortens the deque, keeping the first `len` elements and dropping
     /// the rest.
     ///

library/alloc/tests/vec_deque_alloc_error.rs

@@ -0,0 +1,49 @@
+#![feature(alloc_error_hook, allocator_api)]
+
+use std::{
+    alloc::{set_alloc_error_hook, AllocError, Allocator, Layout, System},
+    collections::VecDeque,
+    panic::{catch_unwind, AssertUnwindSafe},
+    ptr::NonNull,
+};
+
+#[test]
+fn test_shrink_to_unwind() {
+    // This tests that `shrink_to` leaves the deque in a consistent state when
+    // the call to `RawVec::shrink_to_fit` unwinds. The code is adapted from #123369
+    // but changed to hopefully not have any UB even if the test fails.
+
+    struct BadAlloc;
+
+    unsafe impl Allocator for BadAlloc {
+        fn allocate(&self, l: Layout) -> Result<NonNull<[u8]>, AllocError> {
+            // We allocate zeroed here so that the whole buffer of the deque
+            // is always initialized. That way, even if the deque is left in
+            // an inconsistent state, no uninitialized memory should be accessed.
+            System.allocate_zeroed(l)
+        }
+
+        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+            unsafe { System.deallocate(ptr, layout) }
+        }
+
+        unsafe fn shrink(
+            &self,
+            _ptr: NonNull<u8>,
+            _old_layout: Layout,
+            _new_layout: Layout,
+        ) -> Result<NonNull<[u8]>, AllocError> {
+            Err(AllocError)
+        }
+    }
+
+    set_alloc_error_hook(|_| panic!("alloc error"));
+
+    let mut v = VecDeque::with_capacity_in(15, BadAlloc);
+    v.push_back(1);
+    v.push_front(2);
+    // This should unwind because it calls `BadAlloc::shrink` and then `handle_alloc_error` which unwinds.
+    assert!(catch_unwind(AssertUnwindSafe(|| v.shrink_to_fit())).is_err());
+    // This should only pass if the deque is left in a consistent state.
+    assert_eq!(v, [2, 1]);
+}

library/core/src/cell.rs

@@ -245,7 +245,7 @@ use crate::ptr::{self, NonNull};
 mod lazy;
 mod once;
 
-#[unstable(feature = "lazy_cell", issue = "109736")]
+#[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
 pub use lazy::LazyCell;
 #[stable(feature = "once_cell", since = "1.70.0")]
 pub use once::OnceCell;

library/core/src/cell/lazy.rs

@@ -18,8 +18,6 @@ enum State<T, F> {
 /// # Examples
 ///
 /// ```
-/// #![feature(lazy_cell)]
-///
 /// use std::cell::LazyCell;
 ///
 /// let lazy: LazyCell<i32> = LazyCell::new(|| {
@@ -36,7 +34,7 @@ enum State<T, F> {
 /// //   92
 /// //   92
 /// ```
-#[unstable(feature = "lazy_cell", issue = "109736")]
+#[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
 pub struct LazyCell<T, F = fn() -> T> {
     state: UnsafeCell<State<T, F>>,
 }
@@ -47,8 +45,6 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(lazy_cell)]
-    ///
     /// use std::cell::LazyCell;
     ///
     /// let hello = "Hello, World!".to_string();
@@ -58,7 +54,8 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     /// assert_eq!(&*lazy, "HELLO, WORLD!");
     /// ```
     #[inline]
-    #[unstable(feature = "lazy_cell", issue = "109736")]
+    #[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_const_stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
     pub const fn new(f: F) -> LazyCell<T, F> {
         LazyCell { state: UnsafeCell::new(State::Uninit(f)) }
     }
@@ -70,7 +67,6 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(lazy_cell)]
     /// #![feature(lazy_cell_consume)]
     ///
     /// use std::cell::LazyCell;
@@ -99,8 +95,6 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(lazy_cell)]
-    ///
     /// use std::cell::LazyCell;
     ///
     /// let lazy = LazyCell::new(|| 92);
@@ -109,7 +103,7 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     /// assert_eq!(&*lazy, &92);
     /// ```
     #[inline]
-    #[unstable(feature = "lazy_cell", issue = "109736")]
+    #[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
     pub fn force(this: &LazyCell<T, F>) -> &T {
         // SAFETY:
         // This invalidates any mutable references to the data. The resulting
@@ -173,7 +167,7 @@ impl<T, F> LazyCell<T, F> {
     }
 }
 
-#[unstable(feature = "lazy_cell", issue = "109736")]
+#[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
 impl<T, F: FnOnce() -> T> Deref for LazyCell<T, F> {
     type Target = T;
     #[inline]
@@ -182,7 +176,7 @@ impl<T, F: FnOnce() -> T> Deref for LazyCell<T, F> {
     }
 }
 
-#[unstable(feature = "lazy_cell", issue = "109736")]
+#[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
 impl<T: Default> Default for LazyCell<T> {
     /// Creates a new lazy value using `Default` as the initializing function.
     #[inline]
@@ -191,7 +185,7 @@ impl<T: Default> Default for LazyCell<T> {
     }
 }
 
-#[unstable(feature = "lazy_cell", issue = "109736")]
+#[stable(feature = "lazy_cell", since = "CURRENT_RUSTC_VERSION")]
 impl<T: fmt::Debug, F> fmt::Debug for LazyCell<T, F> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut d = f.debug_tuple("LazyCell");

library/core/src/ffi/mod.rs

@@ -133,7 +133,8 @@ mod c_char_definition {
                 any(target_arch = "aarch64", target_arch = "riscv64")
             ),
             all(target_os = "nto", target_arch = "aarch64"),
-            target_os = "horizon"
+            target_os = "horizon",
+            target_os = "aix",
         ))] {
             pub type c_char = u8;
         } else {