Auto merge of #32800 - Manishearth:rollup, r=Manishearth

Rollup of 7 pull requests

- Successful merges: #32687, #32729, #32731, #32732, #32734, #32737, #32741
- Failed merges:

22 files changed, 222 insertions, 136 deletions

diff --git a/configure b/configure
index da5468a0ce6..fdef550a645 100755
--- a/configure
+++ b/configure
@@ -717,18 +717,6 @@ if [ -n "$CFG_ENABLE_DEBUG_JEMALLOC" ]; then putvar CFG_ENABLE_DEBUG_JEMALLOC; f
 
 if [ -n "$CFG_ENABLE_ORBIT" ]; then putvar CFG_ENABLE_ORBIT; fi
 
-# A magic value that allows the compiler to use unstable features
-# during the bootstrap even when doing so would normally be an error
-# because of feature staging or because the build turns on
-# warnings-as-errors and unstable features default to warnings.  The
-# build has to match this key in an env var. Meant to be a mild
-# deterrent from users just turning on unstable features on the stable
-# channel.
-# Basing CFG_BOOTSTRAP_KEY on CFG_BOOTSTRAP_KEY lets it get picked up
-# during a Makefile reconfig.
-CFG_BOOTSTRAP_KEY="${CFG_BOOTSTRAP_KEY-`date +%H:%M:%S`}"
-putvar CFG_BOOTSTRAP_KEY
-
 step_msg "looking for build programs"
 
 probe_need CFG_CURLORWGET  curl wget
diff --git a/mk/main.mk b/mk/main.mk
index a32658ddcef..9b8080f9661 100644
--- a/mk/main.mk
+++ b/mk/main.mk
@@ -24,6 +24,17 @@ CFG_PRERELEASE_VERSION=.1
 # versions in the same place
 CFG_FILENAME_EXTRA=$(shell printf '%s' $(CFG_RELEASE)$(CFG_EXTRA_FILENAME) | $(CFG_HASH_COMMAND))
 
+# A magic value that allows the compiler to use unstable features during the
+# bootstrap even when doing so would normally be an error because of feature
+# staging or because the build turns on warnings-as-errors and unstable features
+# default to warnings. The build has to match this key in an env var.
+#
+# This value is keyed off the release to ensure that all compilers for one
+# particular release have the same bootstrap key. Note that this is
+# intentionally not "secure" by any definition, this is largely just a deterrent
+# from users enabling unstable features on the stable compiler.
+CFG_BOOTSTRAP_KEY=$(CFG_FILENAME_EXTRA)
+
 ifeq ($(CFG_RELEASE_CHANNEL),stable)
 # This is the normal semver version string, e.g. "0.12.0", "0.12.0-nightly"
 CFG_RELEASE=$(CFG_RELEASE_NUM)
diff --git a/src/build_helper/lib.rs b/src/build_helper/lib.rs
index 092a1cabc74..8e1da69cf02 100644
--- a/src/build_helper/lib.rs
+++ b/src/build_helper/lib.rs
@@ -43,10 +43,16 @@ pub fn cc2ar(cc: &Path, target: &str) -> PathBuf {
     if target.contains("musl") || target.contains("msvc") {
         PathBuf::from("ar")
     } else {
+        let parent = cc.parent().unwrap();
         let file = cc.file_name().unwrap().to_str().unwrap();
-        cc.parent().unwrap().join(file.replace("gcc", "ar")
-                                      .replace("cc", "ar")
-                                      .replace("clang", "ar"))
+        for suffix in &["gcc", "cc", "clang"] {
+            if let Some(idx) = file.rfind(suffix) {
+                let mut file = file[..idx].to_owned();
+                file.push_str("ar");
+                return parent.join(&file);
+            }
+        }
+        parent.join(file)
     }
 }
 
diff --git a/src/liballoc/arc.rs b/src/liballoc/arc.rs
index e1f698cb484..4aba567fa1c 100644
--- a/src/liballoc/arc.rs
+++ b/src/liballoc/arc.rs
@@ -124,9 +124,7 @@ const MAX_REFCOUNT: usize = (isize::MAX) as usize;
 #[unsafe_no_drop_flag]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Arc<T: ?Sized> {
-    // FIXME #12808: strange name to try to avoid interfering with
-    // field accesses of the contained type via Deref
-    _ptr: Shared<ArcInner<T>>,
+    ptr: Shared<ArcInner<T>>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -144,9 +142,7 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Arc<U>> for Arc<T> {}
 #[unsafe_no_drop_flag]
 #[stable(feature = "arc_weak", since = "1.4.0")]
 pub struct Weak<T: ?Sized> {
-    // FIXME #12808: strange name to try to avoid interfering with
-    // field accesses of the contained type via Deref
-    _ptr: Shared<ArcInner<T>>,
+    ptr: Shared<ArcInner<T>>,
 }
 
 #[stable(feature = "arc_weak", since = "1.4.0")]
@@ -198,7 +194,7 @@ impl<T> Arc<T> {
             weak: atomic::AtomicUsize::new(1),
             data: data,
         };
-        Arc { _ptr: unsafe { Shared::new(Box::into_raw(x)) } }
+        Arc { ptr: unsafe { Shared::new(Box::into_raw(x)) } }
     }
 
     /// Unwraps the contained value if the `Arc<T>` has exactly one strong reference.
@@ -230,11 +226,11 @@ impl<T> Arc<T> {
         atomic::fence(Acquire);
 
         unsafe {
-            let ptr = *this._ptr;
+            let ptr = *this.ptr;
             let elem = ptr::read(&(*ptr).data);
 
             // Make a weak pointer to clean up the implicit strong-weak reference
-            let _weak = Weak { _ptr: this._ptr };
+            let _weak = Weak { ptr: this.ptr };
             mem::forget(this);
 
             Ok(elem)
@@ -275,7 +271,7 @@ impl<T: ?Sized> Arc<T> {
             // synchronize with the write coming from `is_unique`, so that the
             // events prior to that write happen before this read.
             match this.inner().weak.compare_exchange_weak(cur, cur + 1, Acquire, Relaxed) {
-                Ok(_) => return Weak { _ptr: this._ptr },
+                Ok(_) => return Weak { ptr: this.ptr },
                 Err(old) => cur = old,
             }
         }
@@ -304,13 +300,13 @@ impl<T: ?Sized> Arc<T> {
         // `ArcInner` structure itself is `Sync` because the inner data is
         // `Sync` as well, so we're ok loaning out an immutable pointer to these
         // contents.
-        unsafe { &**self._ptr }
+        unsafe { &**self.ptr }
     }
 
     // Non-inlined part of `drop`.
     #[inline(never)]
     unsafe fn drop_slow(&mut self) {
-        let ptr = *self._ptr;
+        let ptr = *self.ptr;
 
         // Destroy the data at this time, even though we may not free the box
         // allocation itself (there may still be weak pointers lying around).
@@ -368,7 +364,7 @@ impl<T: ?Sized> Clone for Arc<T> {
             }
         }
 
-        Arc { _ptr: self._ptr }
+        Arc { ptr: self.ptr }
     }
 }
 
@@ -436,7 +432,7 @@ impl<T: Clone> Arc<T> {
 
             // Materialize our own implicit weak pointer, so that it can clean
             // up the ArcInner as needed.
-            let weak = Weak { _ptr: this._ptr };
+            let weak = Weak { ptr: this.ptr };
 
             // mark the data itself as already deallocated
             unsafe {
@@ -444,7 +440,7 @@ impl<T: Clone> Arc<T> {
                 // here (due to zeroing) because data is no longer accessed by
                 // other threads (due to there being no more strong refs at this
                 // point).
-                let mut swap = Arc::new(ptr::read(&(**weak._ptr).data));
+                let mut swap = Arc::new(ptr::read(&(**weak.ptr).data));
                 mem::swap(this, &mut swap);
                 mem::forget(swap);
             }
@@ -457,7 +453,7 @@ impl<T: Clone> Arc<T> {
         // As with `get_mut()`, the unsafety is ok because our reference was
         // either unique to begin with, or became one upon cloning the contents.
         unsafe {
-            let inner = &mut **this._ptr;
+            let inner = &mut **this.ptr;
             &mut inner.data
         }
     }
@@ -489,7 +485,7 @@ impl<T: ?Sized> Arc<T> {
             // the Arc itself to be `mut`, so we're returning the only possible
             // reference to the inner data.
             unsafe {
-                let inner = &mut **this._ptr;
+                let inner = &mut **this.ptr;
                 Some(&mut inner.data)
             }
         } else {
@@ -558,7 +554,7 @@ impl<T: ?Sized> Drop for Arc<T> {
         // This structure has #[unsafe_no_drop_flag], so this drop glue may run
         // more than once (but it is guaranteed to be zeroed after the first if
         // it's run more than once)
-        let thin = *self._ptr as *const ();
+        let thin = *self.ptr as *const ();
 
         if thin as usize == mem::POST_DROP_USIZE {
             return;
@@ -639,7 +635,7 @@ impl<T: ?Sized> Weak<T> {
 
             // Relaxed is valid for the same reason it is on Arc's Clone impl
             match inner.strong.compare_exchange_weak(n, n + 1, Relaxed, Relaxed) {
-                Ok(_) => return Some(Arc { _ptr: self._ptr }),
+                Ok(_) => return Some(Arc { ptr: self.ptr }),
                 Err(old) => n = old,
             }
         }
@@ -648,7 +644,7 @@ impl<T: ?Sized> Weak<T> {
     #[inline]
     fn inner(&self) -> &ArcInner<T> {
         // See comments above for why this is "safe"
-        unsafe { &**self._ptr }
+        unsafe { &**self.ptr }
     }
 }
 
@@ -682,7 +678,7 @@ impl<T: ?Sized> Clone for Weak<T> {
             }
         }
 
-        return Weak { _ptr: self._ptr };
+        return Weak { ptr: self.ptr };
     }
 }
 
@@ -714,7 +710,7 @@ impl<T: ?Sized> Drop for Weak<T> {
     /// } // implicit drop
     /// ```
     fn drop(&mut self) {
-        let ptr = *self._ptr;
+        let ptr = *self.ptr;
         let thin = ptr as *const ();
 
         // see comments above for why this check is here
@@ -886,7 +882,7 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for Arc<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> fmt::Pointer for Arc<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::Pointer::fmt(&*self._ptr, f)
+        fmt::Pointer::fmt(&*self.ptr, f)
     }
 }
 
@@ -931,7 +927,7 @@ impl<T> Weak<T> {
                issue = "30425")]
     pub fn new() -> Weak<T> {
         unsafe {
-            Weak { _ptr: Shared::new(Box::into_raw(box ArcInner {
+            Weak { ptr: Shared::new(Box::into_raw(box ArcInner {
                 strong: atomic::AtomicUsize::new(0),
                 weak: atomic::AtomicUsize::new(1),
                 data: uninitialized(),
diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index da803f57a59..c2f0a961327 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -184,9 +184,7 @@ struct RcBox<T: ?Sized> {
 #[unsafe_no_drop_flag]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Rc<T: ?Sized> {
-    // FIXME #12808: strange names to try to avoid interfering with field
-    // accesses of the contained type via Deref
-    _ptr: Shared<RcBox<T>>,
+    ptr: Shared<RcBox<T>>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -215,7 +213,7 @@ impl<T> Rc<T> {
                 // pointers, which ensures that the weak destructor never frees
                 // the allocation while the strong destructor is running, even
                 // if the weak pointer is stored inside the strong one.
-                _ptr: Shared::new(Box::into_raw(box RcBox {
+                ptr: Shared::new(Box::into_raw(box RcBox {
                     strong: Cell::new(1),
                     weak: Cell::new(1),
                     value: value,
@@ -254,7 +252,7 @@ impl<T> Rc<T> {
                 // pointer while also handling drop logic by just crafting a
                 // fake Weak.
                 this.dec_strong();
-                let _weak = Weak { _ptr: this._ptr };
+                let _weak = Weak { ptr: this.ptr };
                 forget(this);
                 Ok(val)
             }
@@ -287,7 +285,7 @@ impl<T: ?Sized> Rc<T> {
     #[stable(feature = "rc_weak", since = "1.4.0")]
     pub fn downgrade(this: &Self) -> Weak<T> {
         this.inc_weak();
-        Weak { _ptr: this._ptr }
+        Weak { ptr: this.ptr }
     }
 
     /// Get the number of weak references to this value.
@@ -348,7 +346,7 @@ impl<T: ?Sized> Rc<T> {
     #[stable(feature = "rc_unique", since = "1.4.0")]
     pub fn get_mut(this: &mut Self) -> Option<&mut T> {
         if Rc::is_unique(this) {
-            let inner = unsafe { &mut **this._ptr };
+            let inner = unsafe { &mut **this.ptr };
             Some(&mut inner.value)
         } else {
             None
@@ -390,7 +388,7 @@ impl<T: Clone> Rc<T> {
         } else if Rc::weak_count(this) != 0 {
             // Can just steal the data, all that's left is Weaks
             unsafe {
-                let mut swap = Rc::new(ptr::read(&(**this._ptr).value));
+                let mut swap = Rc::new(ptr::read(&(**this.ptr).value));
                 mem::swap(this, &mut swap);
                 swap.dec_strong();
                 // Remove implicit strong-weak ref (no need to craft a fake
@@ -404,7 +402,7 @@ impl<T: Clone> Rc<T> {
         // reference count is guaranteed to be 1 at this point, and we required
         // the `Rc<T>` itself to be `mut`, so we're returning the only possible
         // reference to the inner value.
-        let inner = unsafe { &mut **this._ptr };
+        let inner = unsafe { &mut **this.ptr };
         &mut inner.value
     }
 }
@@ -449,7 +447,7 @@ impl<T: ?Sized> Drop for Rc<T> {
     #[unsafe_destructor_blind_to_params]
     fn drop(&mut self) {
         unsafe {
-            let ptr = *self._ptr;
+            let ptr = *self.ptr;
             let thin = ptr as *const ();
 
             if thin as usize != mem::POST_DROP_USIZE {
@@ -490,7 +488,7 @@ impl<T: ?Sized> Clone for Rc<T> {
     #[inline]
     fn clone(&self) -> Rc<T> {
         self.inc_strong();
-        Rc { _ptr: self._ptr }
+        Rc { ptr: self.ptr }
     }
 }
 
@@ -691,7 +689,7 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for Rc<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> fmt::Pointer for Rc<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::Pointer::fmt(&*self._ptr, f)
+        fmt::Pointer::fmt(&*self.ptr, f)
     }
 }
 
@@ -711,9 +709,7 @@ impl<T> From<T> for Rc<T> {
 #[unsafe_no_drop_flag]
 #[stable(feature = "rc_weak", since = "1.4.0")]
 pub struct Weak<T: ?Sized> {
-    // FIXME #12808: strange names to try to avoid interfering with
-    // field accesses of the contained type via Deref
-    _ptr: Shared<RcBox<T>>,
+    ptr: Shared<RcBox<T>>,
 }
 
 #[stable(feature = "rc_weak", since = "1.4.0")]
@@ -749,7 +745,7 @@ impl<T: ?Sized> Weak<T> {
             None
         } else {
             self.inc_strong();
-            Some(Rc { _ptr: self._ptr })
+            Some(Rc { ptr: self.ptr })
         }
     }
 }
@@ -783,7 +779,7 @@ impl<T: ?Sized> Drop for Weak<T> {
     /// ```
     fn drop(&mut self) {
         unsafe {
-            let ptr = *self._ptr;
+            let ptr = *self.ptr;
             let thin = ptr as *const ();
 
             if thin as usize != mem::POST_DROP_USIZE {
@@ -816,7 +812,7 @@ impl<T: ?Sized> Clone for Weak<T> {
     #[inline]
     fn clone(&self) -> Weak<T> {
         self.inc_weak();
-        Weak { _ptr: self._ptr }
+        Weak { ptr: self.ptr }
     }
 }
 
@@ -848,7 +844,7 @@ impl<T> Weak<T> {
     pub fn new() -> Weak<T> {
         unsafe {
             Weak {
-                _ptr: Shared::new(Box::into_raw(box RcBox {
+                ptr: Shared::new(Box::into_raw(box RcBox {
                     strong: Cell::new(0),
                     weak: Cell::new(1),
                     value: uninitialized(),
@@ -910,8 +906,8 @@ impl<T: ?Sized> RcBoxPtr<T> for Rc<T> {
             // the contract anyway.
             // This allows the null check to be elided in the destructor if we
             // manipulated the reference count in the same function.
-            assume(!(*(&self._ptr as *const _ as *const *const ())).is_null());
-            &(**self._ptr)
+            assume(!(*(&self.ptr as *const _ as *const *const ())).is_null());
+            &(**self.ptr)
         }
     }
 }
@@ -924,8 +920,8 @@ impl<T: ?Sized> RcBoxPtr<T> for Weak<T> {
             // the contract anyway.
             // This allows the null check to be elided in the destructor if we
             // manipulated the reference count in the same function.
-            assume(!(*(&self._ptr as *const _ as *const *const ())).is_null());
-            &(**self._ptr)
+            assume(!(*(&self.ptr as *const _ as *const *const ())).is_null());
+            &(**self.ptr)
         }
     }
 }
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index b2cbc29b1c7..a1c7a293af0 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -390,8 +390,8 @@ impl<T: ?Sized> RefCell<T> {
     pub fn borrow(&self) -> Ref<T> {
         match BorrowRef::new(&self.borrow) {
             Some(b) => Ref {
-                _value: unsafe { &*self.value.get() },
-                _borrow: b,
+                value: unsafe { &*self.value.get() },
+                borrow: b,
             },
             None => panic!("RefCell<T> already mutably borrowed"),
         }
@@ -438,8 +438,8 @@ impl<T: ?Sized> RefCell<T> {
     pub fn borrow_mut(&self) -> RefMut<T> {
         match BorrowRefMut::new(&self.borrow) {
             Some(b) => RefMut {
-                _value: unsafe { &mut *self.value.get() },
-                _borrow: b,
+                value: unsafe { &mut *self.value.get() },
+                borrow: b,
             },
             None => panic!("RefCell<T> already borrowed"),
         }
@@ -491,7 +491,7 @@ impl<T: ?Sized + PartialEq> PartialEq for RefCell<T> {
 impl<T: ?Sized + Eq> Eq for RefCell<T> {}
 
 struct BorrowRef<'b> {
-    _borrow: &'b Cell<BorrowFlag>,
+    borrow: &'b Cell<BorrowFlag>,
 }
 
 impl<'b> BorrowRef<'b> {
@@ -501,7 +501,7 @@ impl<'b> BorrowRef<'b> {
             WRITING => None,
             b => {
                 borrow.set(b + 1);
-                Some(BorrowRef { _borrow: borrow })
+                Some(BorrowRef { borrow: borrow })
             },
         }
     }
@@ -510,9 +510,9 @@ impl<'b> BorrowRef<'b> {
 impl<'b> Drop for BorrowRef<'b> {
     #[inline]
     fn drop(&mut self) {
-        let borrow = self._borrow.get();
+        let borrow = self.borrow.get();
         debug_assert!(borrow != WRITING && borrow != UNUSED);
-        self._borrow.set(borrow - 1);
+        self.borrow.set(borrow - 1);
     }
 }
 
@@ -521,10 +521,10 @@ impl<'b> Clone for BorrowRef<'b> {
     fn clone(&self) -> BorrowRef<'b> {
         // Since this Ref exists, we know the borrow flag
         // is not set to WRITING.
-        let borrow = self._borrow.get();
+        let borrow = self.borrow.get();
         debug_assert!(borrow != WRITING && borrow != UNUSED);
-        self._borrow.set(borrow + 1);
-        BorrowRef { _borrow: self._borrow }
+        self.borrow.set(borrow + 1);
+        BorrowRef { borrow: self.borrow }
     }
 }
 
@@ -534,10 +534,8 @@ impl<'b> Clone for BorrowRef<'b> {
 /// See the [module-level documentation](index.html) for more.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Ref<'b, T: ?Sized + 'b> {
-    // FIXME #12808: strange name to try to avoid interfering with
-    // field accesses of the contained type via Deref
-    _value: &'b T,
-    _borrow: BorrowRef<'b>,
+    value: &'b T,
+    borrow: BorrowRef<'b>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -546,7 +544,7 @@ impl<'b, T: ?Sized> Deref for Ref<'b, T> {
 
     #[inline]
     fn deref(&self) -> &T {
-        self._value
+        self.value
     }
 }
 
@@ -565,8 +563,8 @@ impl<'b, T: ?Sized> Ref<'b, T> {
     #[inline]
     pub fn clone(orig: &Ref<'b, T>) -> Ref<'b, T> {
         Ref {
-            _value: orig._value,
-            _borrow: orig._borrow.clone(),
+            value: orig.value,
+            borrow: orig.borrow.clone(),
         }
     }
 
@@ -594,8 +592,8 @@ impl<'b, T: ?Sized> Ref<'b, T> {
         where F: FnOnce(&T) -> &U
     {
         Ref {
-            _value: f(orig._value),
-            _borrow: orig._borrow,
+            value: f(orig.value),
+            borrow: orig.borrow,
         }
     }
 
@@ -627,9 +625,9 @@ impl<'b, T: ?Sized> Ref<'b, T> {
     pub fn filter_map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Option<Ref<'b, U>>
         where F: FnOnce(&T) -> Option<&U>
     {
-        f(orig._value).map(move |new| Ref {
-            _value: new,
-            _borrow: orig._borrow,
+        f(orig.value).map(move |new| Ref {
+            value: new,
+            borrow: orig.borrow,
         })
     }
 }
@@ -667,8 +665,8 @@ impl<'b, T: ?Sized> RefMut<'b, T> {
         where F: FnOnce(&mut T) -> &mut U
     {
         RefMut {
-            _value: f(orig._value),
-            _borrow: orig._borrow,
+            value: f(orig.value),
+            borrow: orig.borrow,
         }
     }
 
@@ -706,24 +704,24 @@ impl<'b, T: ?Sized> RefMut<'b, T> {
     pub fn filter_map<U: ?Sized, F>(orig: RefMut<'b, T>, f: F) -> Option<RefMut<'b, U>>
         where F: FnOnce(&mut T) -> Option<&mut U>
     {
-        let RefMut { _value, _borrow } = orig;
-        f(_value).map(move |new| RefMut {
-            _value: new,
-            _borrow: _borrow,
+        let RefMut { value, borrow } = orig;
+        f(value).map(move |new| RefMut {
+            value: new,
+            borrow: borrow,
         })
     }
 }
 
 struct BorrowRefMut<'b> {
-    _borrow: &'b Cell<BorrowFlag>,
+    borrow: &'b Cell<BorrowFlag>,
 }
 
 impl<'b> Drop for BorrowRefMut<'b> {
     #[inline]
     fn drop(&mut self) {
-        let borrow = self._borrow.get();
+        let borrow = self.borrow.get();
         debug_assert!(borrow == WRITING);
-        self._borrow.set(UNUSED);
+        self.borrow.set(UNUSED);
     }
 }
 
@@ -733,7 +731,7 @@ impl<'b> BorrowRefMut<'b> {
         match borrow.get() {
             UNUSED => {
                 borrow.set(WRITING);
-                Some(BorrowRefMut { _borrow: borrow })
+                Some(BorrowRefMut { borrow: borrow })
             },
             _ => None,
         }
@@ -745,10 +743,8 @@ impl<'b> BorrowRefMut<'b> {
 /// See the [module-level documentation](index.html) for more.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RefMut<'b, T: ?Sized + 'b> {
-    // FIXME #12808: strange name to try to avoid interfering with
-    // field accesses of the contained type via Deref
-    _value: &'b mut T,
-    _borrow: BorrowRefMut<'b>,
+    value: &'b mut T,
+    borrow: BorrowRefMut<'b>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -757,7 +753,7 @@ impl<'b, T: ?Sized> Deref for RefMut<'b, T> {
 
     #[inline]
     fn deref(&self) -> &T {
-        self._value
+        self.value
     }
 }
 
@@ -765,7 +761,7 @@ impl<'b, T: ?Sized> Deref for RefMut<'b, T> {
 impl<'b, T: ?Sized> DerefMut for RefMut<'b, T> {
     #[inline]
     fn deref_mut(&mut self) -> &mut T {
-        self._value
+        self.value
     }
 }
 
diff --git a/src/librustc_trans/abi.rs b/src/librustc_trans/abi.rs
index 961a32170d0..cb29f27b83f 100644
--- a/src/librustc_trans/abi.rs
+++ b/src/librustc_trans/abi.rs
@@ -80,6 +80,8 @@ pub struct ArgType {
     /// Only later will `original_ty` aka `%Foo` be used in the LLVM function
     /// pointer type, without ever having introspected it.
     pub ty: Type,
+    /// Signedness for integer types, None for other types
+    pub signedness: Option<bool>,
     /// Coerced LLVM Type
     pub cast: Option<Type>,
     /// Dummy argument, which is emitted before the real argument
@@ -94,6 +96,7 @@ impl ArgType {
             kind: ArgKind::Direct,
             original_ty: original_ty,
             ty: ty,
+            signedness: None,
             cast: None,
             pad: None,
             attrs: llvm::Attributes::default()
@@ -123,6 +126,19 @@ impl ArgType {
         self.kind = ArgKind::Ignore;
     }
 
+    pub fn extend_integer_width_to(&mut self, bits: u64) {
+        // Only integers have signedness
+        if let Some(signed) = self.signedness {
+            if self.ty.int_width() < bits {
+                self.attrs.set(if signed {
+                    llvm::Attribute::SExt
+                } else {
+                    llvm::Attribute::ZExt
+                });
+            }
+        }
+    }
+
     pub fn is_indirect(&self) -> bool {
         self.kind == ArgKind::Indirect
     }
@@ -268,6 +284,9 @@ impl FnType {
             } else {
                 let mut arg = ArgType::new(type_of::type_of(ccx, ty),
                                            type_of::sizing_type_of(ccx, ty));
+                if ty.is_integral() {
+                    arg.signedness = Some(ty.is_signed());
+                }
                 if llsize_of_real(ccx, arg.ty) == 0 {
                     // For some forsaken reason, x86_64-pc-windows-gnu
                     // doesn't ignore zero-sized struct arguments.
diff --git a/src/librustc_trans/cabi_aarch64.rs b/src/librustc_trans/cabi_aarch64.rs
index 4903af2a6ff..fc11e3888d3 100644
--- a/src/librustc_trans/cabi_aarch64.rs
+++ b/src/librustc_trans/cabi_aarch64.rs
@@ -163,6 +163,7 @@ fn is_homogenous_aggregate_ty(ty: Type) -> Option<(Type, u64)> {
 
 fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType) {
     if is_reg_ty(ret.ty) {
+        ret.extend_integer_width_to(32);
         return;
     }
     if let Some((base_ty, members)) = is_homogenous_aggregate_ty(ret.ty) {
@@ -190,6 +191,7 @@ fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType) {
 
 fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType) {
     if is_reg_ty(arg.ty) {
+        arg.extend_integer_width_to(32);
         return;
     }
     if let Some((base_ty, members)) = is_homogenous_aggregate_ty(arg.ty) {
diff --git a/src/librustc_trans/cabi_arm.rs b/src/librustc_trans/cabi_arm.rs
index 35099399e31..68a2e8aa8ce 100644
--- a/src/librustc_trans/cabi_arm.rs
+++ b/src/librustc_trans/cabi_arm.rs
@@ -131,6 +131,7 @@ fn ty_size(ty: Type, align_fn: TyAlignFn) -> usize {
 
 fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType, align_fn: TyAlignFn) {
     if is_reg_ty(ret.ty) {
+        ret.extend_integer_width_to(32);
         return;
     }
     let size = ty_size(ret.ty, align_fn);
@@ -150,6 +151,7 @@ fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType, align_fn: TyAlignFn) {
 
 fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType, align_fn: TyAlignFn) {
     if is_reg_ty(arg.ty) {
+        arg.extend_integer_width_to(32);
         return;
     }
     let align = align_fn(arg.ty);
diff --git a/src/librustc_trans/cabi_mips.rs b/src/librustc_trans/cabi_mips.rs
index be9d4cad1db..680310e195a 100644
--- a/src/librustc_trans/cabi_mips.rs
+++ b/src/librustc_trans/cabi_mips.rs
@@ -86,6 +86,14 @@ fn ty_size(ty: Type) -> usize {
     }
 }
 
+fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType) {
+    if is_reg_ty(ret.ty) {
+        ret.extend_integer_width_to(32);
+    } else {
+        ret.make_indirect(ccx);
+    }
+}
+
 fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType, offset: &mut usize) {
     let orig_offset = *offset;
     let size = ty_size(arg.ty) * 8;
@@ -98,6 +106,8 @@ fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType, offset: &mut usize) {
     if !is_reg_ty(arg.ty) {
         arg.cast = Some(struct_ty(ccx, arg.ty));
         arg.pad = padding_ty(ccx, align, orig_offset);
+    } else {
+        arg.extend_integer_width_to(32);
     }
 }
 
@@ -146,8 +156,8 @@ fn struct_ty(ccx: &CrateContext, ty: Type) -> Type {
 }
 
 pub fn compute_abi_info(ccx: &CrateContext, fty: &mut FnType) {
-    if !fty.ret.is_ignore() && !is_reg_ty(fty.ret.ty) {
-        fty.ret.make_indirect(ccx);
+    if !fty.ret.is_ignore() {
+        classify_ret_ty(ccx, &mut fty.ret);
     }
 
     let mut offset = if fty.ret.is_indirect() { 4 } else { 0 };
diff --git a/src/librustc_trans/cabi_powerpc.rs b/src/librustc_trans/cabi_powerpc.rs
index d118cc86f24..efbdce67a8b 100644
--- a/src/librustc_trans/cabi_powerpc.rs
+++ b/src/librustc_trans/cabi_powerpc.rs
@@ -82,6 +82,14 @@ fn ty_size(ty: Type) -> usize {
     }
 }
 
+fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType) {
+    if is_reg_ty(ret.ty) {
+        ret.extend_integer_width_to(32);
+    } else {
+        ret.make_indirect(ccx);
+    }
+}
+
 fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType, offset: &mut usize) {
     let orig_offset = *offset;
     let size = ty_size(arg.ty) * 8;
@@ -94,6 +102,8 @@ fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType, offset: &mut usize) {
     if !is_reg_ty(arg.ty) {
         arg.cast = Some(struct_ty(ccx, arg.ty));
         arg.pad = padding_ty(ccx, align, orig_offset);
+    } else {
+        arg.extend_integer_width_to(32);
     }
 }
 
@@ -141,8 +151,8 @@ fn struct_ty(ccx: &CrateContext, ty: Type) -> Type {
 }
 
 pub fn compute_abi_info(ccx: &CrateContext, fty: &mut FnType) {
-    if !fty.ret.is_ignore() && !is_reg_ty(fty.ret.ty) {
-        fty.ret.make_indirect(ccx);
+    if !fty.ret.is_ignore() {
+        classify_ret_ty(ccx, &mut fty.ret);
     }
 
     let mut offset = if fty.ret.is_indirect() { 4 } else { 0 };
diff --git a/src/librustc_trans/cabi_powerpc64.rs b/src/librustc_trans/cabi_powerpc64.rs
index 7bc41d26f8b..ba54e369fd8 100644
--- a/src/librustc_trans/cabi_powerpc64.rs
+++ b/src/librustc_trans/cabi_powerpc64.rs
@@ -153,6 +153,7 @@ fn is_homogenous_aggregate_ty(ty: Type) -> Option<(Type, u64)> {
 
 fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType) {
     if is_reg_ty(ret.ty) {
+        ret.extend_integer_width_to(64);
         return;
     }
 
@@ -187,6 +188,7 @@ fn classify_ret_ty(ccx: &CrateContext, ret: &mut ArgType) {
 
 fn classify_arg_ty(ccx: &CrateContext, arg: &mut ArgType) {
     if is_reg_ty(arg.ty) {
+        arg.extend_integer_width_to(64);
         return;
     }
 
diff --git a/src/librustc_trans/cabi_x86.rs b/src/librustc_trans/cabi_x86.rs
index 415579eb221..b52231fa6b4 100644
--- a/src/librustc_trans/cabi_x86.rs
+++ b/src/librustc_trans/cabi_x86.rs
@@ -15,25 +15,29 @@ use super::common::*;
 use super::machine::*;
 
 pub fn compute_abi_info(ccx: &CrateContext, fty: &mut FnType) {
-    if !fty.ret.is_ignore() && fty.ret.ty.kind() == Struct {
-        // Returning a structure. Most often, this will use
-        // a hidden first argument. On some platforms, though,
-        // small structs are returned as integers.
-        //
-        // Some links:
-        // http://www.angelcode.com/dev/callconv/callconv.html
-        // Clang's ABI handling is in lib/CodeGen/TargetInfo.cpp
-        let t = &ccx.sess().target.target;
-        if t.options.is_like_osx || t.options.is_like_windows {
-            match llsize_of_alloc(ccx, fty.ret.ty) {
-                1 => fty.ret.cast = Some(Type::i8(ccx)),
-                2 => fty.ret.cast = Some(Type::i16(ccx)),
-                4 => fty.ret.cast = Some(Type::i32(ccx)),
-                8 => fty.ret.cast = Some(Type::i64(ccx)),
-                _ => fty.ret.make_indirect(ccx)
+    if !fty.ret.is_ignore() {
+        if fty.ret.ty.kind() == Struct {
+            // Returning a structure. Most often, this will use
+            // a hidden first argument. On some platforms, though,
+            // small structs are returned as integers.
+            //
+            // Some links:
+            // http://www.angelcode.com/dev/callconv/callconv.html
+            // Clang's ABI handling is in lib/CodeGen/TargetInfo.cpp
+            let t = &ccx.sess().target.target;
+            if t.options.is_like_osx || t.options.is_like_windows {
+                match llsize_of_alloc(ccx, fty.ret.ty) {
+                    1 => fty.ret.cast = Some(Type::i8(ccx)),
+                    2 => fty.ret.cast = Some(Type::i16(ccx)),
+                    4 => fty.ret.cast = Some(Type::i32(ccx)),
+                    8 => fty.ret.cast = Some(Type::i64(ccx)),
+                    _ => fty.ret.make_indirect(ccx)
+                }
+            } else {
+                fty.ret.make_indirect(ccx);
             }
         } else {
-            fty.ret.make_indirect(ccx);
+            fty.ret.extend_integer_width_to(32);
         }
     }
 
@@ -42,6 +46,8 @@ pub fn compute_abi_info(ccx: &CrateContext, fty: &mut FnType) {
         if arg.ty.kind() == Struct {
             arg.make_indirect(ccx);
             arg.attrs.set(Attribute::ByVal);
+        } else {
+            arg.extend_integer_width_to(32);
         }
     }
 }
diff --git a/src/librustc_trans/cabi_x86_64.rs b/src/librustc_trans/cabi_x86_64.rs
index e9e9e266c77..805c7d345a0 100644
--- a/src/librustc_trans/cabi_x86_64.rs
+++ b/src/librustc_trans/cabi_x86_64.rs
@@ -400,6 +400,8 @@ pub fn compute_abi_info(ccx: &CrateContext, fty: &mut FnType) {
             } else {
                 arg.cast = Some(llreg_ty(ccx, &cls));
             }
+        } else {
+            arg.extend_integer_width_to(32);
         }
     }
 
diff --git a/src/librustc_trans/cabi_x86_win64.rs b/src/librustc_trans/cabi_x86_win64.rs
index a5077f68fb5..71ecb6e9ca1 100644
--- a/src/librustc_trans/cabi_x86_win64.rs
+++ b/src/librustc_trans/cabi_x86_win64.rs
@@ -26,6 +26,8 @@ pub fn compute_abi_info(ccx: &CrateContext, fty: &mut FnType) {
                 8 => a.cast = Some(Type::i64(ccx)),
                 _ => a.make_indirect(ccx)
             }
+        } else {
+            a.extend_integer_width_to(32);
         }
     };
 
diff --git a/src/librustc_trans/debuginfo/metadata.rs b/src/librustc_trans/debuginfo/metadata.rs
index 822155f8c36..5014186d13b 100644
--- a/src/librustc_trans/debuginfo/metadata.rs
+++ b/src/librustc_trans/debuginfo/metadata.rs
@@ -50,7 +50,9 @@ use syntax::{ast, codemap};
 use syntax::parse::token;
 
 
-const DW_LANG_RUST: c_uint = 0x9000;
+// From DWARF 5.
+// See http://www.dwarfstd.org/ShowIssue.php?issue=140129.1
+const DW_LANG_RUST: c_uint = 0x1c;
 #[allow(non_upper_case_globals)]
 const DW_ATE_boolean: c_uint = 0x02;
 #[allow(non_upper_case_globals)]
diff --git a/src/libstd/os/dragonfly/fs.rs b/src/libstd/os/dragonfly/fs.rs
index eb09800a18c..db672e56435 100644
--- a/src/libstd/os/dragonfly/fs.rs
+++ b/src/libstd/os/dragonfly/fs.rs
@@ -63,10 +63,6 @@ pub trait MetadataExt {
     #[stable(feature = "metadata_ext2", since = "1.8.0")]
     fn st_ctime_nsec(&self) -> i64;
     #[stable(feature = "metadata_ext2", since = "1.8.0")]
-    fn st_birthtime(&self) -> i64;
-    #[stable(feature = "metadata_ext2", since = "1.8.0")]
-    fn st_birthtime_nsec(&self) -> i64;
-    #[stable(feature = "metadata_ext2", since = "1.8.0")]
     fn st_blksize(&self) -> u64;
     #[stable(feature = "metadata_ext2", since = "1.8.0")]
     fn st_blocks(&self) -> u64;
@@ -129,12 +125,6 @@ impl MetadataExt for Metadata {
     fn st_ctime_nsec(&self) -> i64 {
         self.as_inner().as_inner().st_ctime_nsec as i64
     }
-    fn st_birthtime(&self) -> i64 {
-        self.as_inner().as_inner().st_birthtime as i64
-    }
-    fn st_birthtime_nsec(&self) -> i64 {
-        self.as_inner().as_inner().st_birthtime_nsec as i64
-    }
     fn st_blksize(&self) -> u64 {
         self.as_inner().as_inner().st_blksize as u64
     }
diff --git a/src/libstd/sys/common/unwind/gcc.rs b/src/libstd/sys/common/unwind/gcc.rs
index ff6a11951dc..da7a340af35 100644
--- a/src/libstd/sys/common/unwind/gcc.rs
+++ b/src/libstd/sys/common/unwind/gcc.rs
@@ -224,8 +224,13 @@ pub mod eabi {
         context: *mut uw::_Unwind_Context
     ) -> uw::_Unwind_Reason_Code
     {
+        // Backtraces on ARM will call the personality routine with
+        // state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
+        // we want to continue unwinding the stack, otherwise all our backtraces
+        // would end at __rust_try.
         if (state as c_int & uw::_US_ACTION_MASK as c_int)
-                           == uw::_US_VIRTUAL_UNWIND_FRAME as c_int { // search phase
+                           == uw::_US_VIRTUAL_UNWIND_FRAME as c_int
+               && (state as c_int & uw::_US_FORCE_UNWIND as c_int) == 0 { // search phase
             uw::_URC_HANDLER_FOUND // catch!
         }
         else { // cleanup phase
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index eed62c9ecfd..94ebbd70ae8 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -36,6 +36,7 @@ const TMPBUF_SZ: usize = 128;
 static ENV_LOCK: StaticMutex = StaticMutex::new();
 
 /// Returns the platform-specific value of errno
+#[cfg(not(target_os = "dragonfly"))]
 pub fn errno() -> i32 {
     extern {
         #[cfg_attr(any(target_os = "linux", target_os = "emscripten"),
@@ -47,7 +48,6 @@ pub fn errno() -> i32 {
                        target_env = "newlib"),
                    link_name = "__errno")]
         #[cfg_attr(target_os = "solaris", link_name = "___errno")]
-        #[cfg_attr(target_os = "dragonfly", link_name = "__dfly_error")]
         #[cfg_attr(any(target_os = "macos",
                        target_os = "ios",
                        target_os = "freebsd"),
@@ -60,6 +60,16 @@ pub fn errno() -> i32 {
     }
 }
 
+#[cfg(target_os = "dragonfly")]
+pub fn errno() -> i32 {
+    extern {
+        #[thread_local]
+        static errno: c_int;
+    }
+
+    errno as i32
+}
+
 /// Gets a detailed string description for the given error number.
 pub fn error_string(errno: i32) -> String {
     extern {
diff --git a/src/libstd/sys/unix/time.rs b/src/libstd/sys/unix/time.rs
index 1444cf31e85..cc7abe25e35 100644
--- a/src/libstd/sys/unix/time.rs
+++ b/src/libstd/sys/unix/time.rs
@@ -303,8 +303,13 @@ mod inner {
         }
     }
 
+    #[cfg(not(target_os = "dragonfly"))]
+    pub type clock_t = libc::c_int;
+    #[cfg(target_os = "dragonfly")]
+    pub type clock_t = libc::c_ulong;
+
     impl Timespec {
-        pub fn now(clock: libc::c_int) -> Timespec {
+        pub fn now(clock: clock_t) -> Timespec {
             let mut t = Timespec {
                 t: libc::timespec {
                     tv_sec: 0,
diff --git a/src/rt/rust_test_helpers.c b/src/rt/rust_test_helpers.c
index 00bfa63e6fe..d2ebdcca80c 100644
--- a/src/rt/rust_test_helpers.c
+++ b/src/rt/rust_test_helpers.c
@@ -243,3 +243,7 @@ double rust_interesting_average(uint64_t n, ...) {
     va_end(pairs);
     return sum / n;
 }
+
+int32_t rust_int8_to_int32(int8_t x) {
+    return (int32_t)x;
+}
diff --git a/src/test/run-pass/cabi-int-widening.rs b/src/test/run-pass/cabi-int-widening.rs
new file mode 100644
index 00000000000..c7a22759333
--- /dev/null
+++ b/src/test/run-pass/cabi-int-widening.rs
@@ -0,0 +1,22 @@
+// Copyright 2016 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.
+
+#[link(name = "rust_test_helpers")]
+extern {
+    fn rust_int8_to_int32(_: i8) -> i32;
+}
+
+fn main() {
+    let x = unsafe {
+        rust_int8_to_int32(-1)
+    };
+
+    assert!(x == -1);
+}