Merge #877

877: Bump MSRV to Rust 1.38 r=taiki-e a=taiki-e

It was released [nearly 3 years ago](https://blog.rust-lang.org/2019/09/26/Rust-1.38.0.html) and meets our MSRV policy.

This allows using const_in_array_repeat_expressions (rust-lang/rust#49147) and `<pointer>.cast()`.

Co-authored-by: Taiki Endo <te316e89@gmail.com>

.clippy.toml

@@ -1 +1 @@
-msrv = "1.36"
+msrv = "1.38"

.github/workflows/ci.yml

@@ -30,9 +30,9 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - rust: 1.36.0
+          - rust: '1.38'
             os: ubuntu-latest
-          - rust: 1.36.0
+          - rust: '1.38'
             os: windows-latest
           - rust: stable
             os: ubuntu-latest
@@ -75,7 +75,7 @@ jobs:
       fail-fast: false
       matrix:
         rust:
-          - 1.36.0
+          - '1.38'
           - nightly
     runs-on: ubuntu-latest
     steps:

Cargo.toml

@@ -6,7 +6,7 @@ name = "crossbeam"
 # - Create "crossbeam-X.Y.Z" git tag
 version = "0.8.1"
 edition = "2018"
-rust-version = "1.36"
+rust-version = "1.38"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/crossbeam-rs/crossbeam"
 homepage = "https://github.com/crossbeam-rs/crossbeam"

README.md

@@ -8,7 +8,7 @@ https://github.com/crossbeam-rs/crossbeam#license)
 https://crates.io/crates/crossbeam)
 [![Documentation](https://docs.rs/crossbeam/badge.svg)](
 https://docs.rs/crossbeam)
-[![Rust 1.36+](https://img.shields.io/badge/rust-1.36+-lightgray.svg)](
+[![Rust 1.38+](https://img.shields.io/badge/rust-1.38+-lightgray.svg)](
 https://www.rust-lang.org)
 [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
 
@@ -94,7 +94,7 @@ crossbeam = "0.8"
 
 Crossbeam supports stable Rust releases going back at least six months,
 and every time the minimum supported Rust version is increased, a new minor
-version is released. Currently, the minimum supported Rust version is 1.36.
+version is released. Currently, the minimum supported Rust version is 1.38.
 
 ## Contributing
 

crossbeam-channel/Cargo.toml

@@ -6,7 +6,7 @@ name = "crossbeam-channel"
 # - Create "crossbeam-channel-X.Y.Z" git tag
 version = "0.5.5"
 edition = "2018"
-rust-version = "1.36"
+rust-version = "1.38"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/crossbeam-rs/crossbeam"
 homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-channel"

crossbeam-channel/README.md

@@ -8,7 +8,7 @@ https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-channel#license)
 https://crates.io/crates/crossbeam-channel)
 [![Documentation](https://docs.rs/crossbeam-channel/badge.svg)](
 https://docs.rs/crossbeam-channel)
-[![Rust 1.36+](https://img.shields.io/badge/rust-1.36+-lightgray.svg)](
+[![Rust 1.38+](https://img.shields.io/badge/rust-1.38+-lightgray.svg)](
 https://www.rust-lang.org)
 [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
 
@@ -48,7 +48,7 @@ crossbeam-channel = "0.5"
 
 Crossbeam Channel supports stable Rust releases going back at least six months,
 and every time the minimum supported Rust version is increased, a new minor
-version is released. Currently, the minimum supported Rust version is 1.36.
+version is released. Currently, the minimum supported Rust version is 1.38.
 
 ## License
 

crossbeam-channel/src/flavors/array.rs

@@ -216,7 +216,7 @@ impl<T> Channel<T> {
             return Err(msg);
         }
 
-        let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
+        let slot: &Slot<T> = &*token.array.slot.cast::<Slot<T>>();
 
         // Write the message into the slot and update the stamp.
         slot.msg.get().write(MaybeUninit::new(msg));
@@ -307,7 +307,7 @@ impl<T> Channel<T> {
             return Err(());
         }
 
-        let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
+        let slot: &Slot<T> = &*token.array.slot.cast::<Slot<T>>();
 
         // Read the message from the slot and update the stamp.
         let msg = slot.msg.get().read().assume_init();

crossbeam-channel/src/flavors/list.rs

@@ -49,6 +49,11 @@ 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();
@@ -72,13 +77,10 @@ struct Block<T> {
 impl<T> Block<T> {
     /// Creates an empty block.
     fn new() -> Block<T> {
-        // 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.
-        unsafe { MaybeUninit::zeroed().assume_init() }
+        Self {
+            next: AtomicPtr::new(ptr::null_mut()),
+            slots: [Slot::UNINIT; BLOCK_CAP],
+        }
     }
 
     /// Waits until the next pointer is set.
@@ -283,7 +285,7 @@ impl<T> Channel<T> {
         }
 
         // Write the message into the slot.
-        let block = token.list.block as *mut Block<T>;
+        let block = token.list.block.cast::<Block<T>>();
         let offset = token.list.offset;
         let slot = (*block).slots.get_unchecked(offset);
         slot.msg.get().write(MaybeUninit::new(msg));

crossbeam-channel/src/flavors/zero.rs

@@ -190,7 +190,7 @@ impl<T> Channel<T> {
             // heap-allocated packet.
             packet.wait_ready();
             let msg = packet.msg.get().replace(None).unwrap();
-            drop(Box::from_raw(token.zero.0 as *mut Packet<T>));
+            drop(Box::from_raw(token.zero.0.cast::<Packet<T>>()));
             Ok(msg)
         }
     }
@@ -409,15 +409,15 @@ impl<T> SelectHandle for Receiver<'_, T> {
         let mut inner = self.0.inner.lock().unwrap();
         inner
             .receivers
-            .register_with_packet(oper, packet as *mut (), cx);
+            .register_with_packet(oper, packet.cast::<()>(), cx);
         inner.senders.notify();
         inner.senders.can_select() || inner.is_disconnected
     }
 
     fn unregister(&self, oper: Operation) {
         if let Some(operation) = self.0.inner.lock().unwrap().receivers.unregister(oper) {
             unsafe {
-                drop(Box::from_raw(operation.packet as *mut Packet<T>));
+                drop(Box::from_raw(operation.packet.cast::<Packet<T>>()));
             }
         }
     }
@@ -459,15 +459,15 @@ impl<T> SelectHandle for Sender<'_, T> {
         let mut inner = self.0.inner.lock().unwrap();
         inner
             .senders
-            .register_with_packet(oper, packet as *mut (), cx);
+            .register_with_packet(oper, packet.cast::<()>(), cx);
         inner.receivers.notify();
         inner.receivers.can_select() || inner.is_disconnected
     }
 
     fn unregister(&self, oper: Operation) {
         if let Some(operation) = self.0.inner.lock().unwrap().senders.unregister(oper) {
             unsafe {
-                drop(Box::from_raw(operation.packet as *mut Packet<T>));
+                drop(Box::from_raw(operation.packet.cast::<Packet<T>>()));
             }
         }
     }

crossbeam-deque/Cargo.toml

@@ -6,7 +6,7 @@ name = "crossbeam-deque"
 # - Create "crossbeam-deque-X.Y.Z" git tag
 version = "0.8.1"
 edition = "2018"
-rust-version = "1.36"
+rust-version = "1.38"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/crossbeam-rs/crossbeam"
 homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-deque"

crossbeam-deque/README.md

@@ -8,7 +8,7 @@ https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-deque#license)
 https://crates.io/crates/crossbeam-deque)
 [![Documentation](https://docs.rs/crossbeam-deque/badge.svg)](
 https://docs.rs/crossbeam-deque)
-[![Rust 1.36+](https://img.shields.io/badge/rust-1.36+-lightgray.svg)](
+[![Rust 1.38+](https://img.shields.io/badge/rust-1.38+-lightgray.svg)](
 https://www.rust-lang.org)
 [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
 
@@ -28,7 +28,7 @@ crossbeam-deque = "0.8"
 
 Crossbeam Deque supports stable Rust releases going back at least six months,
 and every time the minimum supported Rust version is increased, a new minor
-version is released. Currently, the minimum supported Rust version is 1.36.
+version is released. Currently, the minimum supported Rust version is 1.38.
 
 ## License
 

crossbeam-deque/src/deque.rs

@@ -64,7 +64,7 @@ impl<T> Buffer<T> {
     /// that would be more expensive and difficult to implement generically for all types `T`.
     /// Hence, as a hack, we use a volatile write instead.
     unsafe fn write(&self, index: isize, task: MaybeUninit<T>) {
-        ptr::write_volatile(self.at(index) as *mut MaybeUninit<T>, task)
+        ptr::write_volatile(self.at(index).cast::<MaybeUninit<T>>(), task)
     }
 
     /// Reads a task from the specified `index`.
@@ -74,7 +74,7 @@ impl<T> Buffer<T> {
     /// that would be more expensive and difficult to implement generically for all types `T`.
     /// Hence, as a hack, we use a volatile load instead.
     unsafe fn read(&self, index: isize) -> MaybeUninit<T> {
-        ptr::read_volatile(self.at(index) as *mut MaybeUninit<T>)
+        ptr::read_volatile(self.at(index).cast::<MaybeUninit<T>>())
     }
 }
 
@@ -1119,6 +1119,11 @@ struct Slot<T> {
 }
 
 impl<T> Slot<T> {
+    const UNINIT: Self = Self {
+        task: UnsafeCell::new(MaybeUninit::uninit()),
+        state: AtomicUsize::new(0),
+    };
+
     /// Waits until a task is written into the slot.
     fn wait_write(&self) {
         let backoff = Backoff::new();
@@ -1142,13 +1147,10 @@ struct Block<T> {
 impl<T> Block<T> {
     /// Creates an empty block that starts at `start_index`.
     fn new() -> Block<T> {
-        // 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::task` (UnsafeCell) may be safely zero initialized because it
-        //       holds a MaybeUninit.
-        //  [4] `Slot::state` (AtomicUsize) may be safely zero initialized.
-        unsafe { MaybeUninit::zeroed().assume_init() }
+        Self {
+            next: AtomicPtr::new(ptr::null_mut()),
+            slots: [Slot::UNINIT; BLOCK_CAP],
+        }
     }
 
     /// Waits until the next pointer is set.

crossbeam-epoch/Cargo.toml

@@ -6,7 +6,7 @@ name = "crossbeam-epoch"
 # - Create "crossbeam-epoch-X.Y.Z" git tag
 version = "0.9.9"
 edition = "2018"
-rust-version = "1.36"
+rust-version = "1.38"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/crossbeam-rs/crossbeam"
 homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-epoch"

crossbeam-epoch/README.md

@@ -8,7 +8,7 @@ https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-epoch#license)
 https://crates.io/crates/crossbeam-epoch)
 [![Documentation](https://docs.rs/crossbeam-epoch/badge.svg)](
 https://docs.rs/crossbeam-epoch)
-[![Rust 1.36+](https://img.shields.io/badge/rust-1.36+-lightgray.svg)](
+[![Rust 1.38+](https://img.shields.io/badge/rust-1.38+-lightgray.svg)](
 https://www.rust-lang.org)
 [![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
 
@@ -35,7 +35,7 @@ crossbeam-epoch = "0.9"
 
 Crossbeam Epoch supports stable Rust releases going back at least six months,
 and every time the minimum supported Rust version is increased, a new minor
-version is released. Currently, the minimum supported Rust version is 1.36.
+version is released. Currently, the minimum supported Rust version is 1.38.
 
 ## License
 

crossbeam-epoch/src/atomic.rs

@@ -252,7 +252,7 @@ impl<T> Pointable for [MaybeUninit<T>] {
         let size = mem::size_of::<Array<T>>() + mem::size_of::<MaybeUninit<T>>() * len;
         let align = mem::align_of::<Array<T>>();
         let layout = alloc::Layout::from_size_align(size, align).unwrap();
-        let ptr = alloc::alloc(layout) as *mut Array<T>;
+        let ptr = alloc::alloc(layout).cast::<Array<T>>();
         if ptr.is_null() {
             alloc::handle_alloc_error(layout);
         }

crossbeam-epoch/src/deferred.rs

@@ -29,6 +29,15 @@ impl fmt::Debug for Deferred {
 }
 
 impl Deferred {
+    pub(crate) const NO_OP: Self = {
+        fn no_op_call(_raw: *mut u8) {}
+        Self {
+            call: no_op_call,
+            data: MaybeUninit::uninit(),
+            _marker: PhantomData,
+        }
+    };
+
     /// Constructs a new `Deferred` from a `FnOnce()`.
     pub(crate) fn new<F: FnOnce()>(f: F) -> Self {
         let size = mem::size_of::<F>();
@@ -37,10 +46,10 @@ impl Deferred {
         unsafe {
             if size <= mem::size_of::<Data>() && align <= mem::align_of::<Data>() {
                 let mut data = MaybeUninit::<Data>::uninit();
-                ptr::write(data.as_mut_ptr() as *mut F, f);
+                ptr::write(data.as_mut_ptr().cast::<F>(), f);
 
                 unsafe fn call<F: FnOnce()>(raw: *mut u8) {
-                    let f: F = ptr::read(raw as *mut F);
+                    let f: F = ptr::read(raw.cast::<F>());
                     f();
                 }
 
@@ -52,12 +61,12 @@ impl Deferred {
             } else {
                 let b: Box<F> = Box::new(f);
                 let mut data = MaybeUninit::<Data>::uninit();
-                ptr::write(data.as_mut_ptr() as *mut Box<F>, b);
+                ptr::write(data.as_mut_ptr().cast::<Box<F>>(), b);
 
                 unsafe fn call<F: FnOnce()>(raw: *mut u8) {
                     // It's safe to cast `raw` from `*mut u8` to `*mut Box<F>`, because `raw` is
                     // originally derived from `*mut Box<F>`.
-                    let b: Box<F> = ptr::read(raw as *mut Box<F>);
+                    let b: Box<F> = ptr::read(raw.cast::<Box<F>>());
                     (*b)();
                 }
 
@@ -74,7 +83,7 @@ impl Deferred {
     #[inline]
     pub(crate) fn call(mut self) {
         let call = self.call;
-        unsafe { call(self.data.as_mut_ptr() as *mut u8) };
+        unsafe { call(self.data.as_mut_ptr().cast::<u8>()) };
     }
 }