v0.8: Prepare for the next release

.github/workflows/ci.yml

@@ -35,9 +35,9 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - rust: '1.61'
+          - rust: '1.63'
             os: ubuntu-latest
-          - rust: '1.61'
+          - rust: '1.63'
             os: windows-latest
           - rust: stable
             os: ubuntu-latest
@@ -136,10 +136,10 @@ jobs:
           if ! git diff --exit-code; then
               git add .
               git commit -m "Update no_atomic.rs"
-              echo "::set-output name=success::false"
+              echo 'success=false' >>"${GITHUB_OUTPUT}"
           fi
         if: github.repository_owner == 'crossbeam-rs' && github.event_name == 'schedule'
-      - uses: peter-evans/create-pull-request@v5
+      - uses: peter-evans/create-pull-request@v7
         with:
           title: Update no_atomic.rs
           body: |

Cargo.toml

@@ -71,3 +71,7 @@ unexpected_cfgs = { level = "warn", check-cfg = [
   'cfg(crossbeam_loom)',
   'cfg(crossbeam_sanitize)',
 ] }
+[workspace.lints.clippy]
+# Suppress buggy or noisy clippy lints
+declare_interior_mutable_const = { level = "allow", priority = 1 } # https://github.com/rust-lang/rust-clippy/issues/7665
+lint_groups_priority = { level = "allow", priority = 1 } # https://github.com/rust-lang/rust-clippy/issues/12920

ci/no_atomic.sh

@@ -8,45 +8,24 @@ cd "$(dirname "$0")"/..
 # Usage:
 #    ./ci/no_atomic.sh
 
-file="no_atomic.rs"
+file=no_atomic.rs
 
-no_atomic=()
-for target_spec in $(RUSTC_BOOTSTRAP=1 rustc +stable -Z unstable-options --print all-target-specs-json | jq -c '. | to_entries | .[]'); do
-    target=$(jq <<<"${target_spec}" -r '.key')
-    target_spec=$(jq <<<"${target_spec}" -c '.value')
-    res=$(jq <<<"${target_spec}" -r 'select(."atomic-cas" == false)')
-    [[ -z "${res}" ]] || no_atomic_cas+=("${target}")
-    max_atomic_width=$(jq <<<"${target_spec}" -r '."max-atomic-width"')
-    min_atomic_width=$(jq <<<"${target_spec}" -r '."min-atomic-width"')
-    case "${max_atomic_width}" in
-        # `"max-atomic-width" == 0` means that atomic is not supported at all.
-        # We do not have a cfg for targets with {8,16}-bit atomic only, so
-        # for now we treat them the same as targets that do not support atomic.
-        0) no_atomic+=("${target}") ;;
-        # It is not clear exactly what `"max-atomic-width" == null` means, but they
-        # actually seem to have the same max-atomic-width as the target-pointer-width.
-        # The targets currently included in this group are "mipsel-sony-psp",
-        # "thumbv4t-none-eabi", "thumbv6m-none-eabi", all of which are
-        # `"target-pointer-width" == "32"`, so assuming them `"max-atomic-width" == 32`
-        # for now.
-        null | 8 | 16 | 32 | 64 | 128) ;;
-        *) exit 1 ;;
-    esac
-    case "${min_atomic_width}" in
-        8 | null)  ;;
-        *) no_atomic+=("${target}") ;;
-    esac
-done
+# `"max-atomic-width" == 0` means that atomic is not supported at all.
+# We do not have a cfg for targets with {8,16}-bit atomic only, so
+# for now we treat them the same as targets that do not support atomic.
+# It is not clear exactly what `"max-atomic-width" == null` means, but they
+# actually seem to have the same max-atomic-width as the target-pointer-width.
+# The targets currently included in this group are "mipsel-sony-psp",
+# "thumbv4t-none-eabi", "thumbv6m-none-eabi", all of which are
+# `"target-pointer-width" == "32"`, so assuming them `"max-atomic-width" == 32`
+# for now.
+no_atomic=$(RUSTC_BOOTSTRAP=1 rustc +stable -Z unstable-options --print all-target-specs-json | jq -r '. | to_entries[] | select((.value."max-atomic-width" == 0) or (.value."min-atomic-width" and .value."min-atomic-width" != 8)) | "    \"" + .key + "\","')
 
 cat >"${file}" <<EOF
-// This file is @generated by $(basename "$0").
+// This file is @generated by ${0##*/}.
 // It is not intended for manual editing.
 
 const NO_ATOMIC: &[&str] = &[
-EOF
-for target in "${no_atomic[@]}"; do
-    echo "    \"${target}\"," >>"${file}"
-done
-cat >>"${file}" <<EOF
+${no_atomic}
 ];
 EOF

crossbeam-channel/CHANGELOG.md

@@ -1,3 +1,10 @@
+# Version 0.5.14
+
+- Fix stack overflow when sending large value to unbounded channel. (#1146, #1147)
+- Add `Select::new_biased` function. (#1150)
+- Remove inefficient spinning. (#1154)
+- Suppress buggy `clippy::zero_repeat_side_effects` lint in macro generated code. (#1123)
+
 # Version 0.5.13
 
 - Add `select_biased!` macro. (#1040)

crossbeam-channel/Cargo.toml

@@ -4,7 +4,7 @@ name = "crossbeam-channel"
 # - Update CHANGELOG.md
 # - Update README.md (when increasing major or minor version)
 # - Run './tools/publish.sh crossbeam-channel <version>'
-version = "0.5.13"
+version = "0.5.14"
 edition = "2021"
 rust-version = "1.60"
 license = "MIT OR Apache-2.0"

crossbeam-channel/src/context.rs

@@ -138,21 +138,6 @@ impl Context {
     /// If the deadline is reached, `Selected::Aborted` will be selected.
     #[inline]
     pub fn wait_until(&self, deadline: Option<Instant>) -> Selected {
-        // Spin for a short time, waiting until an operation is selected.
-        let backoff = Backoff::new();
-        loop {
-            let sel = Selected::from(self.inner.select.load(Ordering::Acquire));
-            if sel != Selected::Waiting {
-                return sel;
-            }
-
-            if backoff.is_completed() {
-                break;
-            } else {
-                backoff.snooze();
-            }
-        }
-
         loop {
             // Check whether an operation has been selected.
             let sel = Selected::from(self.inner.select.load(Ordering::Acquire));

crossbeam-channel/src/flavors/list.rs

@@ -1,5 +1,6 @@
 //! Unbounded channel implemented as a linked list.
 
+use std::alloc::{alloc_zeroed, handle_alloc_error, Layout};
 use std::boxed::Box;
 use std::cell::UnsafeCell;
 use std::marker::PhantomData;
@@ -50,11 +51,6 @@ struct Slot<T> {
 }
 
 impl<T> Slot<T> {
-    const UNINIT: Self = Self {
-        msg: UnsafeCell::new(MaybeUninit::uninit()),
-        state: AtomicUsize::new(0),
-    };
-
     /// Waits until a message is written into the slot.
     fn wait_write(&self) {
         let backoff = Backoff::new();
@@ -76,12 +72,31 @@ struct Block<T> {
 }
 
 impl<T> Block<T> {
+    const LAYOUT: Layout = {
+        let layout = Layout::new::<Self>();
+        assert!(
+            layout.size() != 0,
+            "Block should never be zero-sized, as it has an AtomicPtr field"
+        );
+        layout
+    };
+
     /// Creates an empty block.
-    fn new() -> Block<T> {
-        Self {
-            next: AtomicPtr::new(ptr::null_mut()),
-            slots: [Slot::UNINIT; BLOCK_CAP],
+    fn new() -> Box<Self> {
+        // SAFETY: layout is not zero-sized
+        let ptr = unsafe { alloc_zeroed(Self::LAYOUT) };
+        // Handle allocation failure
+        if ptr.is_null() {
+            handle_alloc_error(Self::LAYOUT)
         }
+        // SAFETY: This is safe because:
+        //  [1] `Block::next` (AtomicPtr) may be safely zero initialized.
+        //  [2] `Block::slots` (Array) may be safely zero initialized because of [3, 4].
+        //  [3] `Slot::msg` (UnsafeCell) may be safely zero initialized because it
+        //       holds a MaybeUninit.
+        //  [4] `Slot::state` (AtomicUsize) may be safely zero initialized.
+        // TODO: unsafe { Box::new_zeroed().assume_init() }
+        unsafe { Box::from_raw(ptr.cast()) }
     }
 
     /// Waits until the next pointer is set.
@@ -223,13 +238,13 @@ impl<T> Channel<T> {
             // If we're going to have to install the next block, allocate it in advance in order to
             // make the wait for other threads as short as possible.
             if offset + 1 == BLOCK_CAP && next_block.is_none() {
-                next_block = Some(Box::new(Block::<T>::new()));
+                next_block = Some(Block::<T>::new());
             }
 
             // If this is the first message to be sent into the channel, we need to allocate the
             // first block and install it.
             if block.is_null() {
-                let new = Box::into_raw(Box::new(Block::<T>::new()));
+                let new = Box::into_raw(Block::<T>::new());
 
                 if self
                     .tail

crossbeam-channel/src/select.rs

@@ -611,6 +611,9 @@ pub struct Select<'a> {
 
     /// The next index to assign to an operation.
     next_index: usize,
+
+    /// Whether to use the index of handles as bias for selecting ready operations.
+    biased: bool,
 }
 
 unsafe impl Send for Select<'_> {}
@@ -633,6 +636,28 @@ impl<'a> Select<'a> {
         Select {
             handles: Vec::with_capacity(4),
             next_index: 0,
+            biased: false,
+        }
+    }
+
+    /// Creates an empty list of channel operations with biased selection.
+    ///
+    /// When multiple handles are ready, this will select the operation with the lowest index.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use crossbeam_channel::Select;
+    ///
+    /// let mut sel = Select::new_biased();
+    ///
+    /// // The list of operations is empty, which means no operation can be selected.
+    /// assert!(sel.try_select().is_err());
+    /// ```
+    pub fn new_biased() -> Self {
+        Self {
+            biased: true,
+            ..Default::default()
         }
     }
 
@@ -774,7 +799,7 @@ impl<'a> Select<'a> {
     /// }
     /// ```
     pub fn try_select(&mut self) -> Result<SelectedOperation<'a>, TrySelectError> {
-        try_select(&mut self.handles, false)
+        try_select(&mut self.handles, self.biased)
     }
 
     /// Blocks until one of the operations becomes ready and selects it.
@@ -821,7 +846,7 @@ impl<'a> Select<'a> {
     /// }
     /// ```
     pub fn select(&mut self) -> SelectedOperation<'a> {
-        select(&mut self.handles, false)
+        select(&mut self.handles, self.biased)
     }
 
     /// Blocks for a limited time until one of the operations becomes ready and selects it.
@@ -871,7 +896,7 @@ impl<'a> Select<'a> {
         &mut self,
         timeout: Duration,
     ) -> Result<SelectedOperation<'a>, SelectTimeoutError> {
-        select_timeout(&mut self.handles, timeout, false)
+        select_timeout(&mut self.handles, timeout, self.biased)
     }
 
     /// Blocks until a given deadline, or until one of the operations becomes ready and selects it.
@@ -923,7 +948,7 @@ impl<'a> Select<'a> {
         &mut self,
         deadline: Instant,
     ) -> Result<SelectedOperation<'a>, SelectTimeoutError> {
-        select_deadline(&mut self.handles, deadline, false)
+        select_deadline(&mut self.handles, deadline, self.biased)
     }
 
     /// Attempts to find a ready operation without blocking.
@@ -962,7 +987,7 @@ impl<'a> Select<'a> {
     /// }
     /// ```
     pub fn try_ready(&mut self) -> Result<usize, TryReadyError> {
-        match run_ready(&mut self.handles, Timeout::Now, false) {
+        match run_ready(&mut self.handles, Timeout::Now, self.biased) {
             None => Err(TryReadyError),
             Some(index) => Ok(index),
         }
@@ -1015,7 +1040,7 @@ impl<'a> Select<'a> {
             panic!("no operations have been added to `Select`");
         }
 
-        run_ready(&mut self.handles, Timeout::Never, false).unwrap()
+        run_ready(&mut self.handles, Timeout::Never, self.biased).unwrap()
     }
 
     /// Blocks for a limited time until one of the operations becomes ready.
@@ -1108,7 +1133,7 @@ impl<'a> Select<'a> {
     /// }
     /// ```
     pub fn ready_deadline(&mut self, deadline: Instant) -> Result<usize, ReadyTimeoutError> {
-        match run_ready(&mut self.handles, Timeout::At(deadline), false) {
+        match run_ready(&mut self.handles, Timeout::At(deadline), self.biased) {
             None => Err(ReadyTimeoutError),
             Some(index) => Ok(index),
         }
@@ -1120,6 +1145,7 @@ impl<'a> Clone for Select<'a> {
         Select {
             handles: self.handles.clone(),
             next_index: self.next_index,
+            biased: self.biased,
         }
     }
 }

crossbeam-channel/src/select_macro.rs

@@ -687,7 +687,7 @@ macro_rules! crossbeam_channel_internal {
         const _LEN: usize = $crate::crossbeam_channel_internal!(@count ($($cases)*));
         let _handle: &dyn $crate::internal::SelectHandle = &$crate::never::<()>();
 
-        #[allow(unused_mut)]
+        #[allow(unused_mut, clippy::zero_repeat_side_effects)]
         let mut _sel = [(_handle, 0, ::std::ptr::null()); _LEN];
 
         $crate::crossbeam_channel_internal!(

crossbeam-channel/tests/list.rs

@@ -580,3 +580,18 @@ fn channel_through_channel() {
     })
     .unwrap();
 }
+
+// If `Block` is created on the stack, the array of slots will multiply this `BigStruct` and
+// probably overflow the thread stack. It's now directly created on the heap to avoid this.
+#[test]
+fn stack_overflow() {
+    const N: usize = 32_768;
+    struct BigStruct {
+        _data: [u8; N],
+    }
+
+    let (sender, receiver) = unbounded::<BigStruct>();
+    sender.send(BigStruct { _data: [0u8; N] }).unwrap();
+
+    for _data in receiver.try_iter() {}
+}

crossbeam-channel/tests/select_macro.rs

@@ -858,6 +858,7 @@ fn fairness1() {
     assert!(hits.iter().all(|x| *x >= COUNT / hits.len() / 2));
 }
 
+#[cfg_attr(crossbeam_sanitize, ignore)] // TODO: flaky: https://github.com/crossbeam-rs/crossbeam/issues/1094
 #[test]
 fn fairness2() {
     #[cfg(miri)]

crossbeam-deque/CHANGELOG.md

@@ -1,3 +1,7 @@
+# Version 0.8.6
+
+- Fix stack overflow when pushing large value to `Injector`. (#1146, #1147, #1159)
+
 # Version 0.8.5
 
 - Remove dependency on `cfg-if`. (#1072)

crossbeam-deque/Cargo.toml

@@ -4,7 +4,7 @@ name = "crossbeam-deque"
 # - Update CHANGELOG.md
 # - Update README.md (when increasing major or minor version)
 # - Run './tools/publish.sh crossbeam-deque <version>'
-version = "0.8.5"
+version = "0.8.6"
 edition = "2021"
 rust-version = "1.61"
 license = "MIT OR Apache-2.0"