Rollup of 4 pull requests

src/doc/unstable-book/src/library-features/fnbox.md

@@ -0,0 +1,32 @@
+# `fnbox`
+
+The tracking issue for this feature is [#28796]
+
+[#28796]: https://github.com/rust-lang/rust/issues/28796
+
+------------------------
+
+This had been a temporary alternative to the following impls:
+
+```rust,ignore
+impl<A, F> FnOnce for Box<F> where F: FnOnce<A> + ?Sized {}
+impl<A, F> FnMut for Box<F> where F: FnMut<A> + ?Sized {}
+impl<A, F> Fn for Box<F> where F: Fn<A> + ?Sized {}
+```
+
+The impls are parallel to these (relatively old) impls:
+
+```rust,ignore
+impl<A, F> FnOnce for &mut F where F: FnMut<A> + ?Sized {}
+impl<A, F> FnMut for &mut F where F: FnMut<A> + ?Sized {}
+impl<A, F> Fn for &mut F where F: Fn<A> + ?Sized {}
+impl<A, F> FnOnce for &F where F: Fn<A> + ?Sized {}
+impl<A, F> FnMut for &F where F: Fn<A> + ?Sized {}
+impl<A, F> Fn for &F where F: Fn<A> + ?Sized {}
+```
+
+Before the introduction of [`unsized_locals`][unsized_locals], we had been unable to provide the former impls. That means, unlike `&dyn Fn()` or `&mut dyn FnMut()` we could not use `Box<dyn FnOnce()>` at that time.
+
+[unsized_locals]: language-features/unsized-locals.html
+
+`FnBox()` is an alternative approach to `Box<dyn FnBox()>` is delegated to `FnBox::call_box` which doesn't need unsized locals. As we now have `Box<dyn FnOnce()>` working, the `fnbox` feature is going to be removed.

src/liballoc/boxed.rs

@@ -81,7 +81,7 @@ use core::ops::{
     CoerceUnsized, DispatchFromDyn, Deref, DerefMut, Receiver, Generator, GeneratorState
 };
 use core::ptr::{self, NonNull, Unique};
-use core::task::{Waker, Poll};
+use core::task::{Context, Poll};
 
 use crate::vec::Vec;
 use crate::raw_vec::RawVec;
@@ -694,6 +694,28 @@ impl<I: ExactSizeIterator + ?Sized> ExactSizeIterator for Box<I> {
 #[stable(feature = "fused", since = "1.26.0")]
 impl<I: FusedIterator + ?Sized> FusedIterator for Box<I> {}
 
+#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
+impl<A, F: FnOnce<A> + ?Sized> FnOnce<A> for Box<F> {
+    type Output = <F as FnOnce<A>>::Output;
+
+    extern "rust-call" fn call_once(self, args: A) -> Self::Output {
+        <F as FnOnce<A>>::call_once(*self, args)
+    }
+}
+
+#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
+impl<A, F: FnMut<A> + ?Sized> FnMut<A> for Box<F> {
+    extern "rust-call" fn call_mut(&mut self, args: A) -> Self::Output {
+        <F as FnMut<A>>::call_mut(self, args)
+    }
+}
+
+#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
+impl<A, F: Fn<A> + ?Sized> Fn<A> for Box<F> {
+    extern "rust-call" fn call(&self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(self, args)
+    }
+}
 
 /// `FnBox` is a version of the `FnOnce` intended for use with boxed
 /// closure objects. The idea is that where one would normally store a
@@ -735,9 +757,7 @@ impl<I: FusedIterator + ?Sized> FusedIterator for Box<I> {}
 #[rustc_paren_sugar]
 #[unstable(feature = "fnbox",
            reason = "will be deprecated if and when `Box<FnOnce>` becomes usable", issue = "28796")]
-pub trait FnBox<A> {
-    type Output;
-
+pub trait FnBox<A>: FnOnce<A> {
     fn call_box(self: Box<Self>, args: A) -> Self::Output;
 }
 
@@ -746,33 +766,11 @@ pub trait FnBox<A> {
 impl<A, F> FnBox<A> for F
     where F: FnOnce<A>
 {
-    type Output = F::Output;
-
     fn call_box(self: Box<F>, args: A) -> F::Output {
         self.call_once(args)
     }
 }
 
-#[unstable(feature = "fnbox",
-           reason = "will be deprecated if and when `Box<FnOnce>` becomes usable", issue = "28796")]
-impl<A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + '_> {
-    type Output = R;
-
-    extern "rust-call" fn call_once(self, args: A) -> R {
-        self.call_box(args)
-    }
-}
-
-#[unstable(feature = "fnbox",
-           reason = "will be deprecated if and when `Box<FnOnce>` becomes usable", issue = "28796")]
-impl<A, R> FnOnce<A> for Box<dyn FnBox<A, Output = R> + Send + '_> {
-    type Output = R;
-
-    extern "rust-call" fn call_once(self, args: A) -> R {
-        self.call_box(args)
-    }
-}
-
 #[unstable(feature = "coerce_unsized", issue = "27732")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Box<U>> for Box<T> {}
 
@@ -914,7 +912,7 @@ impl<G: ?Sized + Generator> Generator for Pin<Box<G>> {
 impl<F: ?Sized + Future + Unpin> Future for Box<F> {
     type Output = F::Output;
 
-    fn poll(mut self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output> {
-        F::poll(Pin::new(&mut *self), waker)
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        F::poll(Pin::new(&mut *self), cx)
     }
 }

src/liballoc/lib.rs

@@ -107,6 +107,7 @@
 #![feature(unboxed_closures)]
 #![feature(unicode_internals)]
 #![feature(unsize)]
+#![feature(unsized_locals)]
 #![feature(allocator_internals)]
 #![feature(on_unimplemented)]
 #![feature(rustc_const_unstable)]

src/libcore/future/future.rs

@@ -5,7 +5,7 @@
 use marker::Unpin;
 use ops;
 use pin::Pin;
-use task::{Poll, Waker};
+use task::{Context, Poll};
 
 /// A future represents an asynchronous computation.
 ///
@@ -44,8 +44,9 @@ pub trait Future {
     /// Once a future has finished, clients should not `poll` it again.
     ///
     /// When a future is not ready yet, `poll` returns `Poll::Pending` and
-    /// stores a clone of the [`Waker`] to be woken once the future can
-    /// make progress. For example, a future waiting for a socket to become
+    /// stores a clone of the [`Waker`] copied from the current [`Context`].
+    /// This [`Waker`] is then woken once the future can make progress.
+    /// For example, a future waiting for a socket to become
     /// readable would call `.clone()` on the [`Waker`] and store it.
     /// When a signal arrives elsewhere indicating that the socket is readable,
     /// `[Waker::wake]` is called and the socket future's task is awoken.
@@ -88,16 +89,17 @@ pub trait Future {
     ///
     /// [`Poll::Pending`]: ../task/enum.Poll.html#variant.Pending
     /// [`Poll::Ready(val)`]: ../task/enum.Poll.html#variant.Ready
+    /// [`Context`]: ../task/struct.Context.html
     /// [`Waker`]: ../task/struct.Waker.html
     /// [`Waker::wake`]: ../task/struct.Waker.html#method.wake
-    fn poll(self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output>;
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>;
 }
 
 impl<F: ?Sized + Future + Unpin> Future for &mut F {
     type Output = F::Output;
 
-    fn poll(mut self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output> {
-        F::poll(Pin::new(&mut **self), waker)
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        F::poll(Pin::new(&mut **self), cx)
     }
 }
 
@@ -108,7 +110,7 @@ where
 {
     type Output = <<P as ops::Deref>::Target as Future>::Output;
 
-    fn poll(self: Pin<&mut Self>, waker: &Waker) -> Poll<Self::Output> {
-        Pin::get_mut(self).as_mut().poll(waker)
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Pin::get_mut(self).as_mut().poll(cx)
     }
 }

src/libcore/task/mod.rs

@@ -8,4 +8,4 @@ mod poll;
 pub use self::poll::Poll;
 
 mod wake;
-pub use self::wake::{Waker, RawWaker, RawWakerVTable};
+pub use self::wake::{Context, Waker, RawWaker, RawWakerVTable};

src/libcore/task/wake.rs

@@ -3,7 +3,7 @@
             issue = "50547")]
 
 use fmt;
-use marker::Unpin;
+use marker::{PhantomData, Unpin};
 
 /// A `RawWaker` allows the implementor of a task executor to create a [`Waker`]
 /// which provides customized wakeup behavior.
@@ -36,6 +36,10 @@ impl RawWaker {
     /// The `vtable` customizes the behavior of a `Waker` which gets created
     /// from a `RawWaker`. For each operation on the `Waker`, the associated
     /// function in the `vtable` of the underlying `RawWaker` will be called.
+    #[rustc_promotable]
+    #[unstable(feature = "futures_api",
+            reason = "futures in libcore are unstable",
+            issue = "50547")]
     pub const fn new(data: *const (), vtable: &'static RawWakerVTable) -> RawWaker {
         RawWaker {
             data,
@@ -63,21 +67,103 @@ pub struct RawWakerVTable {
     /// required for this additional instance of a [`RawWaker`] and associated
     /// task. Calling `wake` on the resulting [`RawWaker`] should result in a wakeup
     /// of the same task that would have been awoken by the original [`RawWaker`].
-    pub clone: unsafe fn(*const ()) -> RawWaker,
+    clone: unsafe fn(*const ()) -> RawWaker,
 
     /// This function will be called when `wake` is called on the [`Waker`].
     /// It must wake up the task associated with this [`RawWaker`].
     ///
     /// The implemention of this function must not consume the provided data
     /// pointer.
-    pub wake: unsafe fn(*const ()),
+    wake: unsafe fn(*const ()),
+
+    /// This function gets called when a [`RawWaker`] gets dropped.
+    ///
+    /// The implementation of this function must make sure to release any
+    /// resources that are associated with this instance of a [`RawWaker`] and
+    /// associated task.
+    drop: unsafe fn(*const ()),
+}
 
+impl RawWakerVTable {
+    /// Creates a new `RawWakerVTable` from the provided `clone`, `wake`, and
+    /// `drop` functions.
+    ///
+    /// # `clone`
+    ///
+    /// This function will be called when the [`RawWaker`] gets cloned, e.g. when
+    /// the [`Waker`] in which the [`RawWaker`] is stored gets cloned.
+    ///
+    /// The implementation of this function must retain all resources that are
+    /// required for this additional instance of a [`RawWaker`] and associated
+    /// task. Calling `wake` on the resulting [`RawWaker`] should result in a wakeup
+    /// of the same task that would have been awoken by the original [`RawWaker`].
+    ///
+    /// # `wake`
+    ///
+    /// This function will be called when `wake` is called on the [`Waker`].
+    /// It must wake up the task associated with this [`RawWaker`].
+    ///
+    /// The implemention of this function must not consume the provided data
+    /// pointer.
+    ///
+    /// # `drop`
+    ///
     /// This function gets called when a [`RawWaker`] gets dropped.
     ///
     /// The implementation of this function must make sure to release any
     /// resources that are associated with this instance of a [`RawWaker`] and
     /// associated task.
-    pub drop: unsafe fn(*const ()),
+    #[rustc_promotable]
+    #[unstable(feature = "futures_api",
+            reason = "futures in libcore are unstable",
+            issue = "50547")]
+    pub const fn new(
+        clone: unsafe fn(*const ()) -> RawWaker,
+        wake: unsafe fn(*const ()),
+        drop: unsafe fn(*const ()),
+    ) -> Self {
+        Self {
+            clone,
+            wake,
+            drop,
+        }
+    }
+}
+
+/// The `Context` of an asynchronous task.
+///
+/// Currently, `Context` only serves to provide access to a `&Waker`
+/// which can be used to wake the current task.
+pub struct Context<'a> {
+    waker: &'a Waker,
+    // Ensure we future-proof against variance changes by including
+    // an `&mut` reference with the provided lifetime.
+    _marker: PhantomData<&'a mut ()>,
+}
+
+impl<'a> Context<'a> {
+    /// Create a new `Context` from a `&Waker`.
+    #[inline]
+    pub fn from_waker(waker: &'a Waker) -> Self {
+        Context {
+            waker,
+            _marker: PhantomData,
+        }
+    }
+
+    /// Returns a reference to the `Waker` for the current task.
+    #[inline]
+    pub fn waker(&self) -> &'a Waker {
+        &self.waker
+    }
+}
+
+impl fmt::Debug for Context<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Context")
+            .field("waker", &self.waker)
+            .finish()
+    }
 }
 
 /// A `Waker` is a handle for waking up a task by notifying its executor that it
@@ -98,6 +184,7 @@ unsafe impl Sync for Waker {}
 
 impl Waker {
     /// Wake up the task associated with this `Waker`.
+    #[inline]
     pub fn wake(&self) {
         // The actual wakeup call is delegated through a virtual function call
         // to the implementation which is defined by the executor.
@@ -115,6 +202,7 @@ impl Waker {
     /// returns `true`, it is guaranteed that the `Waker`s will awaken the same task.
     ///
     /// This function is primarily used for optimization purposes.
+    #[inline]
     pub fn will_wake(&self, other: &Waker) -> bool {
         self.waker == other.waker
     }
@@ -124,6 +212,7 @@ impl Waker {
     /// The behavior of the returned `Waker` is undefined if the contract defined
     /// in [`RawWaker`]'s and [`RawWakerVTable`]'s documentation is not upheld.
     /// Therefore this method is unsafe.
+    #[inline]
     pub unsafe fn new_unchecked(waker: RawWaker) -> Waker {
         Waker {
             waker,
@@ -132,6 +221,7 @@ impl Waker {
 }
 
 impl Clone for Waker {
+    #[inline]
     fn clone(&self) -> Self {
         Waker {
             // SAFETY: This is safe because `Waker::new_unchecked` is the only way
@@ -143,6 +233,7 @@ impl Clone for Waker {
 }
 
 impl Drop for Waker {
+    #[inline]
     fn drop(&mut self) {
         // SAFETY: This is safe because `Waker::new_unchecked` is the only way
         // to initialize `drop` and `data` requiring the user to acknowledge

src/librustc_codegen_llvm/back/link.rs

@@ -1396,10 +1396,6 @@ fn add_upstream_rust_crates(cmd: &mut dyn Linker,
 
     // Same thing as above, but for dynamic crates instead of static crates.
     fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
-        // If we're performing LTO, then it should have been previously required
-        // that all upstream rust dependencies were available in an rlib format.
-        assert!(!are_upstream_rust_objects_already_included(sess));
-
         // Just need to tell the linker about where the library lives and
         // what its name is
         let parent = cratepath.parent();

src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs

@@ -21,6 +21,15 @@ pub fn target() -> Result<Target, String> {
         "-Wl,--no-undefined-version",
         "-Wl,-Bsymbolic",
         "-Wl,--export-dynamic",
+        // The following symbols are needed by libunwind, which is linked after
+        // libstd. Make sure they're included in the link.
+        "-Wl,-u,__rust_abort",
+        "-Wl,-u,__rust_c_alloc",
+        "-Wl,-u,__rust_c_dealloc",
+        "-Wl,-u,__rust_print_err",
+        "-Wl,-u,__rust_rwlock_rdlock",
+        "-Wl,-u,__rust_rwlock_unlock",
+        "-Wl,-u,__rust_rwlock_wrlock",
     ];
 
     const EXPORT_SYMBOLS: &[&str] = &[