Auto merge of #42212 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 15 pull requests

- Successful merges: #41980, #42071, #42120, #42134, #42141, #42142, #42149, #42150, #42159, #42177, #42186, #42191, #42195, #42198, #42211
- Failed merges:

6 files changed, 64 insertions, 57 deletions

diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index f497734e249..a5a1b5e5f09 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -247,7 +247,9 @@ impl OsString {
         self.inner.shrink_to_fit()
     }
 
-    /// Converts this `OsString` into a boxed `OsStr`.
+    /// Converts this `OsString` into a boxed [`OsStr`].
+    ///
+    /// [`OsStr`]: struct.OsStr.html
     ///
     /// # Examples
     ///
@@ -482,12 +484,13 @@ impl OsStr {
     /// Returns the length of this `OsStr`.
     ///
     /// Note that this does **not** return the number of bytes in this string
-    /// as, for example, OS strings on Windows are encoded as a list of `u16`
+    /// as, for example, OS strings on Windows are encoded as a list of [`u16`]
     /// rather than a list of bytes. This number is simply useful for passing to
     /// other methods like [`OsString::with_capacity`] to avoid reallocations.
     ///
     /// See `OsStr` introduction for more information about encoding.
     ///
+    /// [`u16`]: ../primitive.u16.html
     /// [`OsString::with_capacity`]: struct.OsString.html#method.with_capacity
     ///
     /// # Examples
@@ -506,7 +509,10 @@ impl OsStr {
         self.inner.inner.len()
     }
 
-    /// Converts a `Box<OsStr>` into an `OsString` without copying or allocating.
+    /// Converts a [`Box`]`<OsStr>` into an [`OsString`] without copying or allocating.
+    ///
+    /// [`Box`]: ../boxed/struct.Box.html
+    /// [`OsString`]: struct.OsString.html
     #[unstable(feature = "into_boxed_os_str", issue = "40380")]
     pub fn into_os_string(self: Box<OsStr>) -> OsString {
         let inner: Box<Slice> = unsafe { mem::transmute(self) };
diff --git a/src/libstd/rt.rs b/src/libstd/rt.rs
index acff7faf8a7..06fd838ea06 100644
--- a/src/libstd/rt.rs
+++ b/src/libstd/rt.rs
@@ -35,6 +35,8 @@ fn lang_start(main: fn(), argc: isize, argv: *const *const u8) -> isize {
     use sys_common;
     use sys_common::thread_info;
     use thread::Thread;
+    #[cfg(not(feature = "backtrace"))]
+    use mem;
 
     sys::init();
 
@@ -53,9 +55,12 @@ fn lang_start(main: fn(), argc: isize, argv: *const *const u8) -> isize {
         sys::args::init(argc, argv);
 
         // Let's run some code!
+        #[cfg(feature = "backtrace")]
         let res = panic::catch_unwind(|| {
             ::sys_common::backtrace::__rust_begin_short_backtrace(main)
         });
+        #[cfg(not(feature = "backtrace"))]
+        let res = panic::catch_unwind(mem::transmute::<_, fn()>(main));
         sys_common::cleanup();
         res.is_err()
     };
diff --git a/src/libstd/sync/mpsc/mpsc_queue.rs b/src/libstd/sync/mpsc/mpsc_queue.rs
index 8d80f942ff7..296773d20f6 100644
--- a/src/libstd/sync/mpsc/mpsc_queue.rs
+++ b/src/libstd/sync/mpsc/mpsc_queue.rs
@@ -1,29 +1,12 @@
-/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- *    1. Redistributions of source code must retain the above copyright notice,
- *       this list of conditions and the following disclaimer.
- *
- *    2. Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in the
- *       documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
- * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * The views and conclusions contained in the software and documentation are
- * those of the authors and should not be interpreted as representing official
- * policies, either expressed or implied, of Dmitry Vyukov.
- */
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
 
 //! A mostly lock-free multi-producer, single consumer queue.
 //!
diff --git a/src/libstd/sync/mpsc/spsc_queue.rs b/src/libstd/sync/mpsc/spsc_queue.rs
index 5858e4b6ddb..1148bc66fba 100644
--- a/src/libstd/sync/mpsc/spsc_queue.rs
+++ b/src/libstd/sync/mpsc/spsc_queue.rs
@@ -1,31 +1,12 @@
-/* Copyright (c) 2010-2011 Dmitry Vyukov. All rights reserved.
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- *    1. Redistributions of source code must retain the above copyright notice,
- *       this list of conditions and the following disclaimer.
- *
- *    2. Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in the
- *       documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY DMITRY VYUKOV "AS IS" AND ANY EXPRESS OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
- * SHALL DMITRY VYUKOV OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
- * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * The views and conclusions contained in the software and documentation are
- * those of the authors and should not be interpreted as representing official
- * policies, either expressed or implied, of Dmitry Vyukov.
- */
-
-// http://www.1024cores.net/home/lock-free-algorithms/queues/unbounded-spsc-queue
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
 
 //! A single-producer single-consumer concurrent queue
 //!
@@ -33,6 +14,8 @@
 //! concurrently between two threads. This data structure is safe to use and
 //! enforces the semantics that there is one pusher and one popper.
 
+// http://www.1024cores.net/home/lock-free-algorithms/queues/unbounded-spsc-queue
+
 use alloc::boxed::Box;
 use core::ptr;
 use core::cell::UnsafeCell;
diff --git a/src/libstd/sys/redox/thread_local.rs b/src/libstd/sys/redox/thread_local.rs
index abdd9ace795..cacd84e2102 100644
--- a/src/libstd/sys/redox/thread_local.rs
+++ b/src/libstd/sys/redox/thread_local.rs
@@ -64,3 +64,8 @@ pub unsafe fn set(key: Key, value: *mut u8) {
 pub unsafe fn destroy(key: Key) {
     keys().remove(&key);
 }
+
+#[inline]
+pub fn requires_synchronized_create() -> bool {
+    false
+}
diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs
index 154406a1d8b..d0e3b00d75f 100644
--- a/src/libstd/thread/mod.rs
+++ b/src/libstd/thread/mod.rs
@@ -359,9 +359,12 @@ impl Builder {
             }
             unsafe {
                 thread_info::set(imp::guard::current(), their_thread);
+                #[cfg(feature = "backtrace")]
                 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
                     ::sys_common::backtrace::__rust_begin_short_backtrace(f)
                 }));
+                #[cfg(not(feature = "backtrace"))]
+                let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f));
                 *their_packet.get() = Some(try_result);
             }
         };
@@ -394,6 +397,26 @@ impl Builder {
 /// want to specify the stack size or the name of the thread, use this API
 /// instead.
 ///
+/// As you can see in the signature of `spawn` there are two constraints on
+/// both the closure given to `spawn` and its return value, let's explain them:
+///
+/// - The `'static` constraint means that the closure and its return value
+///   must have a lifetime of the whole program execution. The reason for this
+///   is that threads can `detach` and outlive the lifetime they have been
+///   created in.
+///   Indeed if the thread, and by extension its return value, can outlive their
+///   caller, we need to make sure that they will be valid afterwards, and since
+///   we *can't* know when it will return we need to have them valid as long as
+///   possible, that is until the end of the program, hence the `'static`
+///   lifetime.
+/// - The [`Send`] constraint is because the closure will need to be passed
+///   *by value* from the thread where it is spawned to the new thread. Its
+///   return value will need to be passed from the new thread to the thread
+///   where it is `join`ed.
+///   As a reminder, the [`Send`] marker trait, expresses that it is safe to be
+///   passed from thread to thread. [`Sync`] expresses that it is safe to have a
+///   reference be passed from thread to thread.
+///
 /// # Panics
 ///
 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
@@ -460,6 +483,8 @@ impl Builder {
 /// [`panic`]: ../../std/macro.panic.html
 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
 /// [`Builder`]: ../../std/thread/struct.Builder.html
+/// [`Send`]: ../../std/marker/trait.Send.html
+/// [`Sync`]: ../../std/marker/trait.Sync.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
     F: FnOnce() -> T, F: Send + 'static, T: Send + 'static