Rollup merge of #38421 - apasel422:issue-36934, r=alexcrichton

Replace invalid use of `&mut` with `UnsafeCell` in `std::sync::mpsc`

Closes #36934

r? @alexcrichton

1 files changed, 85 insertions, 107 deletions

diff --git a/src/libstd/sync/mpsc/mod.rs b/src/libstd/sync/mpsc/mod.rs
index 63745388eb6..8bcf008649f 100644
--- a/src/libstd/sync/mpsc/mod.rs
+++ b/src/libstd/sync/mpsc/mod.rs
@@ -348,7 +348,7 @@ impl<T> !Sync for Sender<T> { }
 /// owned by one thread, but it can be cloned to send to other threads.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct SyncSender<T> {
-    inner: Arc<UnsafeCell<sync::Packet<T>>>,
+    inner: Arc<sync::Packet<T>>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -426,10 +426,10 @@ pub enum TrySendError<T> {
 }
 
 enum Flavor<T> {
-    Oneshot(Arc<UnsafeCell<oneshot::Packet<T>>>),
-    Stream(Arc<UnsafeCell<stream::Packet<T>>>),
-    Shared(Arc<UnsafeCell<shared::Packet<T>>>),
-    Sync(Arc<UnsafeCell<sync::Packet<T>>>),
+    Oneshot(Arc<oneshot::Packet<T>>),
+    Stream(Arc<stream::Packet<T>>),
+    Shared(Arc<shared::Packet<T>>),
+    Sync(Arc<sync::Packet<T>>),
 }
 
 #[doc(hidden)]
@@ -487,7 +487,7 @@ impl<T> UnsafeFlavor<T> for Receiver<T> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
-    let a = Arc::new(UnsafeCell::new(oneshot::Packet::new()));
+    let a = Arc::new(oneshot::Packet::new());
     (Sender::new(Flavor::Oneshot(a.clone())), Receiver::new(Flavor::Oneshot(a)))
 }
 
@@ -532,7 +532,7 @@ pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn sync_channel<T>(bound: usize) -> (SyncSender<T>, Receiver<T>) {
-    let a = Arc::new(UnsafeCell::new(sync::Packet::new(bound)));
+    let a = Arc::new(sync::Packet::new(bound));
     (SyncSender::new(a.clone()), Receiver::new(Flavor::Sync(a)))
 }
 
@@ -578,38 +578,30 @@ impl<T> Sender<T> {
     pub fn send(&self, t: T) -> Result<(), SendError<T>> {
         let (new_inner, ret) = match *unsafe { self.inner() } {
             Flavor::Oneshot(ref p) => {
-                unsafe {
-                    let p = p.get();
-                    if !(*p).sent() {
-                        return (*p).send(t).map_err(SendError);
-                    } else {
-                        let a =
-                            Arc::new(UnsafeCell::new(stream::Packet::new()));
-                        let rx = Receiver::new(Flavor::Stream(a.clone()));
-                        match (*p).upgrade(rx) {
-                            oneshot::UpSuccess => {
-                                let ret = (*a.get()).send(t);
-                                (a, ret)
-                            }
-                            oneshot::UpDisconnected => (a, Err(t)),
-                            oneshot::UpWoke(token) => {
-                                // This send cannot panic because the thread is
-                                // asleep (we're looking at it), so the receiver
-                                // can't go away.
-                                (*a.get()).send(t).ok().unwrap();
-                                token.signal();
-                                (a, Ok(()))
-                            }
+                if !p.sent() {
+                    return p.send(t).map_err(SendError);
+                } else {
+                    let a = Arc::new(stream::Packet::new());
+                    let rx = Receiver::new(Flavor::Stream(a.clone()));
+                    match p.upgrade(rx) {
+                        oneshot::UpSuccess => {
+                            let ret = a.send(t);
+                            (a, ret)
+                        }
+                        oneshot::UpDisconnected => (a, Err(t)),
+                        oneshot::UpWoke(token) => {
+                            // This send cannot panic because the thread is
+                            // asleep (we're looking at it), so the receiver
+                            // can't go away.
+                            a.send(t).ok().unwrap();
+                            token.signal();
+                            (a, Ok(()))
                         }
                     }
                 }
             }
-            Flavor::Stream(ref p) => return unsafe {
-                (*p.get()).send(t).map_err(SendError)
-            },
-            Flavor::Shared(ref p) => return unsafe {
-                (*p.get()).send(t).map_err(SendError)
-            },
+            Flavor::Stream(ref p) => return p.send(t).map_err(SendError),
+            Flavor::Shared(ref p) => return p.send(t).map_err(SendError),
             Flavor::Sync(..) => unreachable!(),
         };
 
@@ -624,41 +616,43 @@ impl<T> Sender<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Clone for Sender<T> {
     fn clone(&self) -> Sender<T> {
-        let (packet, sleeper, guard) = match *unsafe { self.inner() } {
+        let packet = match *unsafe { self.inner() } {
             Flavor::Oneshot(ref p) => {
-                let a = Arc::new(UnsafeCell::new(shared::Packet::new()));
-                unsafe {
-                    let guard = (*a.get()).postinit_lock();
+                let a = Arc::new(shared::Packet::new());
+                {
+                    let guard = a.postinit_lock();
                     let rx = Receiver::new(Flavor::Shared(a.clone()));
-                    match (*p.get()).upgrade(rx) {
+                    let sleeper = match p.upgrade(rx) {
                         oneshot::UpSuccess |
-                        oneshot::UpDisconnected => (a, None, guard),
-                        oneshot::UpWoke(task) => (a, Some(task), guard)
-                    }
+                        oneshot::UpDisconnected => None,
+                        oneshot::UpWoke(task) => Some(task),
+                    };
+                    a.inherit_blocker(sleeper, guard);
                 }
+                a
             }
             Flavor::Stream(ref p) => {
-                let a = Arc::new(UnsafeCell::new(shared::Packet::new()));
-                unsafe {
-                    let guard = (*a.get()).postinit_lock();
+                let a = Arc::new(shared::Packet::new());
+                {
+                    let guard = a.postinit_lock();
                     let rx = Receiver::new(Flavor::Shared(a.clone()));
-                    match (*p.get()).upgrade(rx) {
+                    let sleeper = match p.upgrade(rx) {
                         stream::UpSuccess |
-                        stream::UpDisconnected => (a, None, guard),
-                        stream::UpWoke(task) => (a, Some(task), guard),
-                    }
+                        stream::UpDisconnected => None,
+                        stream::UpWoke(task) => Some(task),
+                    };
+                    a.inherit_blocker(sleeper, guard);
                 }
+                a
             }
             Flavor::Shared(ref p) => {
-                unsafe { (*p.get()).clone_chan(); }
+                p.clone_chan();
                 return Sender::new(Flavor::Shared(p.clone()));
             }
             Flavor::Sync(..) => unreachable!(),
         };
 
         unsafe {
-            (*packet.get()).inherit_blocker(sleeper, guard);
-
             let tmp = Sender::new(Flavor::Shared(packet.clone()));
             mem::swap(self.inner_mut(), tmp.inner_mut());
         }
@@ -669,10 +663,10 @@ impl<T> Clone for Sender<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Drop for Sender<T> {
     fn drop(&mut self) {
-        match *unsafe { self.inner_mut() } {
-            Flavor::Oneshot(ref mut p) => unsafe { (*p.get()).drop_chan(); },
-            Flavor::Stream(ref mut p) => unsafe { (*p.get()).drop_chan(); },
-            Flavor::Shared(ref mut p) => unsafe { (*p.get()).drop_chan(); },
+        match *unsafe { self.inner() } {
+            Flavor::Oneshot(ref p) => p.drop_chan(),
+            Flavor::Stream(ref p) => p.drop_chan(),
+            Flavor::Shared(ref p) => p.drop_chan(),
             Flavor::Sync(..) => unreachable!(),
         }
     }
@@ -690,7 +684,7 @@ impl<T> fmt::Debug for Sender<T> {
 ////////////////////////////////////////////////////////////////////////////////
 
 impl<T> SyncSender<T> {
-    fn new(inner: Arc<UnsafeCell<sync::Packet<T>>>) -> SyncSender<T> {
+    fn new(inner: Arc<sync::Packet<T>>) -> SyncSender<T> {
         SyncSender { inner: inner }
     }
 
@@ -710,7 +704,7 @@ impl<T> SyncSender<T> {
     /// information.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn send(&self, t: T) -> Result<(), SendError<T>> {
-        unsafe { (*self.inner.get()).send(t).map_err(SendError) }
+        self.inner.send(t).map_err(SendError)
     }
 
     /// Attempts to send a value on this channel without blocking.
@@ -724,14 +718,14 @@ impl<T> SyncSender<T> {
     /// receiver has received the data or not if this function is successful.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn try_send(&self, t: T) -> Result<(), TrySendError<T>> {
-        unsafe { (*self.inner.get()).try_send(t) }
+        self.inner.try_send(t)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Clone for SyncSender<T> {
     fn clone(&self) -> SyncSender<T> {
-        unsafe { (*self.inner.get()).clone_chan(); }
+        self.inner.clone_chan();
         SyncSender::new(self.inner.clone())
     }
 }
@@ -739,7 +733,7 @@ impl<T> Clone for SyncSender<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Drop for SyncSender<T> {
     fn drop(&mut self) {
-        unsafe { (*self.inner.get()).drop_chan(); }
+        self.inner.drop_chan();
     }
 }
 
@@ -772,7 +766,7 @@ impl<T> Receiver<T> {
         loop {
             let new_port = match *unsafe { self.inner() } {
                 Flavor::Oneshot(ref p) => {
-                    match unsafe { (*p.get()).try_recv() } {
+                    match p.try_recv() {
                         Ok(t) => return Ok(t),
                         Err(oneshot::Empty) => return Err(TryRecvError::Empty),
                         Err(oneshot::Disconnected) => {
@@ -782,7 +776,7 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Stream(ref p) => {
-                    match unsafe { (*p.get()).try_recv() } {
+                    match p.try_recv() {
                         Ok(t) => return Ok(t),
                         Err(stream::Empty) => return Err(TryRecvError::Empty),
                         Err(stream::Disconnected) => {
@@ -792,7 +786,7 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Shared(ref p) => {
-                    match unsafe { (*p.get()).try_recv() } {
+                    match p.try_recv() {
                         Ok(t) => return Ok(t),
                         Err(shared::Empty) => return Err(TryRecvError::Empty),
                         Err(shared::Disconnected) => {
@@ -801,7 +795,7 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Sync(ref p) => {
-                    match unsafe { (*p.get()).try_recv() } {
+                    match p.try_recv() {
                         Ok(t) => return Ok(t),
                         Err(sync::Empty) => return Err(TryRecvError::Empty),
                         Err(sync::Disconnected) => {
@@ -875,7 +869,7 @@ impl<T> Receiver<T> {
         loop {
             let new_port = match *unsafe { self.inner() } {
                 Flavor::Oneshot(ref p) => {
-                    match unsafe { (*p.get()).recv(None) } {
+                    match p.recv(None) {
                         Ok(t) => return Ok(t),
                         Err(oneshot::Disconnected) => return Err(RecvError),
                         Err(oneshot::Upgraded(rx)) => rx,
@@ -883,7 +877,7 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Stream(ref p) => {
-                    match unsafe { (*p.get()).recv(None) } {
+                    match p.recv(None) {
                         Ok(t) => return Ok(t),
                         Err(stream::Disconnected) => return Err(RecvError),
                         Err(stream::Upgraded(rx)) => rx,
@@ -891,15 +885,13 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Shared(ref p) => {
-                    match unsafe { (*p.get()).recv(None) } {
+                    match p.recv(None) {
                         Ok(t) => return Ok(t),
                         Err(shared::Disconnected) => return Err(RecvError),
                         Err(shared::Empty) => unreachable!(),
                     }
                 }
-                Flavor::Sync(ref p) => return unsafe {
-                    (*p.get()).recv(None).map_err(|_| RecvError)
-                }
+                Flavor::Sync(ref p) => return p.recv(None).map_err(|_| RecvError),
             };
             unsafe {
                 mem::swap(self.inner_mut(), new_port.inner_mut());
@@ -952,7 +944,7 @@ impl<T> Receiver<T> {
         loop {
             let port_or_empty = match *unsafe { self.inner() } {
                 Flavor::Oneshot(ref p) => {
-                    match unsafe { (*p.get()).recv(Some(deadline)) } {
+                    match p.recv(Some(deadline)) {
                         Ok(t) => return Ok(t),
                         Err(oneshot::Disconnected) => return Err(Disconnected),
                         Err(oneshot::Upgraded(rx)) => Some(rx),
@@ -960,7 +952,7 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Stream(ref p) => {
-                    match unsafe { (*p.get()).recv(Some(deadline)) } {
+                    match p.recv(Some(deadline)) {
                         Ok(t) => return Ok(t),
                         Err(stream::Disconnected) => return Err(Disconnected),
                         Err(stream::Upgraded(rx)) => Some(rx),
@@ -968,14 +960,14 @@ impl<T> Receiver<T> {
                     }
                 }
                 Flavor::Shared(ref p) => {
-                    match unsafe { (*p.get()).recv(Some(deadline)) } {
+                    match p.recv(Some(deadline)) {
                         Ok(t) => return Ok(t),
                         Err(shared::Disconnected) => return Err(Disconnected),
                         Err(shared::Empty) => None,
                     }
                 }
                 Flavor::Sync(ref p) => {
-                    match unsafe { (*p.get()).recv(Some(deadline)) } {
+                    match p.recv(Some(deadline)) {
                         Ok(t) => return Ok(t),
                         Err(sync::Disconnected) => return Err(Disconnected),
                         Err(sync::Empty) => None,
@@ -1020,23 +1012,19 @@ impl<T> select::Packet for Receiver<T> {
         loop {
             let new_port = match *unsafe { self.inner() } {
                 Flavor::Oneshot(ref p) => {
-                    match unsafe { (*p.get()).can_recv() } {
+                    match p.can_recv() {
                         Ok(ret) => return ret,
                         Err(upgrade) => upgrade,
                     }
                 }
                 Flavor::Stream(ref p) => {
-                    match unsafe { (*p.get()).can_recv() } {
+                    match p.can_recv() {
                         Ok(ret) => return ret,
                         Err(upgrade) => upgrade,
                     }
                 }
-                Flavor::Shared(ref p) => {
-                    return unsafe { (*p.get()).can_recv() };
-                }
-                Flavor::Sync(ref p) => {
-                    return unsafe { (*p.get()).can_recv() };
-                }
+                Flavor::Shared(ref p) => return p.can_recv(),
+                Flavor::Sync(ref p) => return p.can_recv(),
             };
             unsafe {
                 mem::swap(self.inner_mut(),
@@ -1049,25 +1037,21 @@ impl<T> select::Packet for Receiver<T> {
         loop {
             let (t, new_port) = match *unsafe { self.inner() } {
                 Flavor::Oneshot(ref p) => {
-                    match unsafe { (*p.get()).start_selection(token) } {
+                    match p.start_selection(token) {
                         oneshot::SelSuccess => return Installed,
                         oneshot::SelCanceled => return Abort,
                         oneshot::SelUpgraded(t, rx) => (t, rx),
                     }
                 }
                 Flavor::Stream(ref p) => {
-                    match unsafe { (*p.get()).start_selection(token) } {
+                    match p.start_selection(token) {
                         stream::SelSuccess => return Installed,
                         stream::SelCanceled => return Abort,
                         stream::SelUpgraded(t, rx) => (t, rx),
                     }
                 }
-                Flavor::Shared(ref p) => {
-                    return unsafe { (*p.get()).start_selection(token) };
-                }
-                Flavor::Sync(ref p) => {
-                    return unsafe { (*p.get()).start_selection(token) };
-                }
+                Flavor::Shared(ref p) => return p.start_selection(token),
+                Flavor::Sync(ref p) => return p.start_selection(token),
             };
             token = t;
             unsafe {
@@ -1080,16 +1064,10 @@ impl<T> select::Packet for Receiver<T> {
         let mut was_upgrade = false;
         loop {
             let result = match *unsafe { self.inner() } {
-                Flavor::Oneshot(ref p) => unsafe { (*p.get()).abort_selection() },
-                Flavor::Stream(ref p) => unsafe {
-                    (*p.get()).abort_selection(was_upgrade)
-                },
-                Flavor::Shared(ref p) => return unsafe {
-                    (*p.get()).abort_selection(was_upgrade)
-                },
-                Flavor::Sync(ref p) => return unsafe {
-                    (*p.get()).abort_selection()
-                },
+                Flavor::Oneshot(ref p) => p.abort_selection(),
+                Flavor::Stream(ref p) => p.abort_selection(was_upgrade),
+                Flavor::Shared(ref p) => return p.abort_selection(was_upgrade),
+                Flavor::Sync(ref p) => return p.abort_selection(),
             };
             let new_port = match result { Ok(b) => return b, Err(p) => p };
             was_upgrade = true;
@@ -1142,11 +1120,11 @@ impl <T> IntoIterator for Receiver<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Drop for Receiver<T> {
     fn drop(&mut self) {
-        match *unsafe { self.inner_mut() } {
-            Flavor::Oneshot(ref mut p) => unsafe { (*p.get()).drop_port(); },
-            Flavor::Stream(ref mut p) => unsafe { (*p.get()).drop_port(); },
-            Flavor::Shared(ref mut p) => unsafe { (*p.get()).drop_port(); },
-            Flavor::Sync(ref mut p) => unsafe { (*p.get()).drop_port(); },
+        match *unsafe { self.inner() } {
+            Flavor::Oneshot(ref p) => p.drop_port(),
+            Flavor::Stream(ref p) => p.drop_port(),
+            Flavor::Shared(ref p) => p.drop_port(),
+            Flavor::Sync(ref p) => p.drop_port(),
         }
     }
 }