diff --git a/src/liblog/lib.rs b/src/liblog/lib.rs
index 4ee5b2d5e8349..7642c866d6081 100644
--- a/src/liblog/lib.rs
+++ b/src/liblog/lib.rs
@@ -177,7 +177,7 @@ use std::mem;
 use std::os;
 use std::rt;
 use std::slice;
-use std::sync::{Once, ONCE_INIT};
+use std::sync::{Once, ONCE_INIT, StaticMutex, MUTEX_INIT};
 
 use regex::Regex;
 
@@ -193,6 +193,8 @@ pub const MAX_LOG_LEVEL: u32 = 255;
 /// The default logging level of a crate if no other is specified.
 const DEFAULT_LOG_LEVEL: u32 = 1;
 
+static LOCK: StaticMutex = MUTEX_INIT;
+
 /// An unsafe constant that is the maximum logging level of any module
 /// specified. This is the first line of defense to determining whether a
 /// logging statement should be run.
@@ -279,9 +281,18 @@ impl Drop for DefaultLogger {
 pub fn log(level: u32, loc: &'static LogLocation, args: fmt::Arguments) {
     // Test the literal string from args against the current filter, if there
     // is one.
-    match unsafe { FILTER.as_ref() } {
-        Some(filter) if !filter.is_match(args.to_string()[]) => return,
-        _ => {}
+    unsafe {
+        let _g = LOCK.lock();
+        match FILTER as uint {
+            0 => {}
+            1 => panic!("cannot log after main thread has exited"),
+            n => {
+                let filter = mem::transmute::<_, &Regex>(n);
+                if !filter.is_match(args.to_string().as_slice()) {
+                    return
+                }
+            }
+        }
     }
 
     // Completely remove the local logger from TLS in case anyone attempts to
@@ -363,9 +374,15 @@ pub fn mod_enabled(level: u32, module: &str) -> bool {
 
     // This assertion should never get tripped unless we're in an at_exit
     // handler after logging has been torn down and a logging attempt was made.
-    assert!(unsafe { !DIRECTIVES.is_null() });
 
-    enabled(level, module, unsafe { (*DIRECTIVES).iter() })
+    let _g = LOCK.lock();
+    unsafe {
+        assert!(DIRECTIVES as uint != 0);
+        assert!(DIRECTIVES as uint != 1,
+                "cannot log after the main thread has exited");
+
+        enabled(level, module, (*DIRECTIVES).iter())
+    }
 }
 
 fn enabled(level: u32,
@@ -421,14 +438,15 @@ fn init() {
 
         // Schedule the cleanup for the globals for when the runtime exits.
         rt::at_exit(move |:| {
+            let _g = LOCK.lock();
             assert!(!DIRECTIVES.is_null());
             let _directives: Box<Vec<directive::LogDirective>> =
                 mem::transmute(DIRECTIVES);
-            DIRECTIVES = 0 as *const Vec<directive::LogDirective>;
+            DIRECTIVES = 1 as *const Vec<directive::LogDirective>;
 
             if !FILTER.is_null() {
                 let _filter: Box<Regex> = mem::transmute(FILTER);
-                FILTER = 0 as *const _;
+                FILTER = 1 as *const _;
             }
         });
     }
diff --git a/src/libstd/io/stdio.rs b/src/libstd/io/stdio.rs
index cd991c5f884f5..af6daaf261ef2 100644
--- a/src/libstd/io/stdio.rs
+++ b/src/libstd/io/stdio.rs
@@ -25,30 +25,21 @@
 //! out.write(b"Hello, world!");
 //! ```
 
+use prelude::v1::*;
 use self::StdSource::*;
 
-use boxed::Box;
 use cell::RefCell;
-use clone::Clone;
 use failure::LOCAL_STDERR;
 use fmt;
-use io::{Reader, Writer, IoResult, IoError, OtherIoError, Buffer,
-         standard_error, EndOfFile, LineBufferedWriter, BufferedReader};
-use kinds::{Sync, Send};
+use io::{IoResult, IoError, OtherIoError};
+use io::{standard_error, EndOfFile, LineBufferedWriter, BufferedReader};
 use libc;
 use mem;
-use option::Option;
-use option::Option::{Some, None};
-use ops::{Deref, DerefMut, FnOnce};
-use result::Result::{Ok, Err};
+use ops::{Deref, DerefMut};
 use rt;
-use slice::SliceExt;
-use str::StrExt;
-use string::String;
+use sync::{Arc, Mutex, MutexGuard, StaticMutex, MUTEX_INIT};
 use sys::{fs, tty};
-use sync::{Arc, Mutex, MutexGuard, Once, ONCE_INIT};
 use uint;
-use vec::Vec;
 
 // And so begins the tale of acquiring a uv handle to a stdio stream on all
 // platforms in all situations. Our story begins by splitting the world into two
@@ -217,14 +208,15 @@ impl Reader for StdinReader {
 pub fn stdin() -> StdinReader {
     // We're following the same strategy as kimundi's lazy_static library
     static mut STDIN: *const StdinReader = 0 as *const StdinReader;
-    static ONCE: Once = ONCE_INIT;
+    static LOCK: StaticMutex = MUTEX_INIT;
 
     unsafe {
-        ONCE.call_once(|| {
-            // The default buffer capacity is 64k, but apparently windows doesn't like
-            // 64k reads on stdin. See #13304 for details, but the idea is that on
-            // windows we use a slightly smaller buffer that's been seen to be
-            // acceptable.
+        let _g = LOCK.lock();
+        if STDIN as uint == 0 {
+            // The default buffer capacity is 64k, but apparently windows
+            // doesn't like 64k reads on stdin. See #13304 for details, but the
+            // idea is that on windows we use a slightly smaller buffer that's
+            // been seen to be acceptable.
             let stdin = if cfg!(windows) {
                 BufferedReader::with_capacity(8 * 1024, stdin_raw())
             } else {
@@ -237,11 +229,15 @@ pub fn stdin() -> StdinReader {
 
             // Make sure to free it at exit
             rt::at_exit(|| {
-                mem::transmute::<_, Box<StdinReader>>(STDIN);
-                STDIN = 0 as *const _;
+                let g = LOCK.lock();
+                let stdin = STDIN;
+                STDIN = 1 as *const _;
+                drop(g);
+                mem::transmute::<_, Box<StdinReader>>(stdin);
             });
-        });
-
+        } else if STDIN as uint == 1 {
+            panic!("accessing stdin after the main thread has exited")
+        }
         (*STDIN).clone()
     }
 }
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 7c8aab2b31dae..078aed003242d 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -230,13 +230,13 @@ pub mod task;
 pub mod thread;
 pub mod sync;
 
+#[path = "sys/common/mod.rs"] mod sys_common;
+
 #[cfg(unix)]
 #[path = "sys/unix/mod.rs"] mod sys;
 #[cfg(windows)]
 #[path = "sys/windows/mod.rs"] mod sys;
 
-#[path = "sys/common/mod.rs"] mod sys_common;
-
 pub mod rt;
 mod failure;
 
diff --git a/src/libstd/rt/at_exit_imp.rs b/src/libstd/rt/at_exit_imp.rs
index 5823f8453d84a..08dabd3b0b603 100644
--- a/src/libstd/rt/at_exit_imp.rs
+++ b/src/libstd/rt/at_exit_imp.rs
@@ -29,6 +29,8 @@ type Queue = Vec<Thunk>;
 static LOCK: Mutex = MUTEX_INIT;
 static mut QUEUE: *mut Queue = 0 as *mut Queue;
 
+const DTOR_RUN_ITERS: uint = 10;
+
 unsafe fn init() {
     if QUEUE.is_null() {
         let state: Box<Queue> = box Vec::new();
@@ -49,7 +51,7 @@ pub fn cleanup() {
     unsafe {
         LOCK.lock();
         let queue = QUEUE;
-        QUEUE = 1 as *mut _;
+        QUEUE = 1u as *mut _;
         LOCK.unlock();
 
         // make sure we're not recursively cleaning up
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index 68aaa1b3ae55d..5df702dde1e91 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -93,9 +93,7 @@ fn lang_start(main: *const u8, argc: int, argv: *const *const u8) -> int {
         // but we just do this to name the main thread and to give it correct
         // info about the stack bounds.
         let thread: Thread = NewThread::new(Some("<main>".to_string()));
-        thread_info::set((my_stack_bottom, my_stack_top),
-                         sys::thread::guard::main(),
-                         thread);
+        thread_info::set(sys::thread::guard::main(), thread);
 
         // By default, some platforms will send a *signal* when a EPIPE error
         // would otherwise be delivered. This runtime doesn't install a SIGPIPE
@@ -134,20 +132,14 @@ fn lang_start(main: *const u8, argc: int, argv: *const *const u8) -> int {
     }
 }
 
-/// Enqueues a procedure to run when the runtime is cleaned up
-///
-/// The procedure passed to this function will be executed as part of the
-/// runtime cleanup phase. For normal rust programs, this means that it will run
-/// after all other threads have exited.
-///
-/// The procedure is *not* executed with a local `Thread` available to it, so
-/// primitives like logging, I/O, channels, spawning, etc, are *not* available.
-/// This is meant for "bare bones" usage to clean up runtime details, this is
-/// not meant as a general-purpose "let's clean everything up" function.
+/// Enqueues a procedure to run when the main thread exits.
 ///
 /// It is forbidden for procedures to register more `at_exit` handlers when they
 /// are running, and doing so will lead to a process abort.
-pub fn at_exit<F:FnOnce()+Send>(f: F) {
+///
+/// Note that other threads may still be running when `at_exit` routines start
+/// running.
+pub fn at_exit<F: FnOnce() + Send>(f: F) {
     at_exit_imp::push(Thunk::new(f));
 }
 
@@ -163,8 +155,5 @@ pub fn at_exit<F:FnOnce()+Send>(f: F) {
 pub unsafe fn cleanup() {
     args::cleanup();
     sys::stack_overflow::cleanup();
-    // FIXME: (#20012): the resources being cleaned up by at_exit
-    // currently are not prepared for cleanup to happen asynchronously
-    // with detached threads using the resources; for now, we leak.
-    // at_exit_imp::cleanup();
+    at_exit_imp::cleanup();
 }
diff --git a/src/libstd/rt/unwind.rs b/src/libstd/rt/unwind.rs
index 6f6be2e111df4..b34195c9d7e0d 100644
--- a/src/libstd/rt/unwind.rs
+++ b/src/libstd/rt/unwind.rs
@@ -68,7 +68,7 @@ use intrinsics;
 use libc::c_void;
 use mem;
 use sync::atomic;
-use sync::{Once, ONCE_INIT};
+use sys_common::mutex::{Mutex, MUTEX_INIT};
 
 use rt::libunwind as uw;
 
@@ -529,11 +529,20 @@ pub fn begin_unwind<M: Any + Send>(msg: M, file_line: &(&'static str, uint)) ->
 /// Doing this split took the LLVM IR line counts of `fn main() { panic!()
 /// }` from ~1900/3700 (-O/no opts) to 180/590.
 #[inline(never)] #[cold] // this is the slow path, please never inline this
-fn begin_unwind_inner(msg: Box<Any + Send>, file_line: &(&'static str, uint)) -> ! {
+fn begin_unwind_inner(msg: Box<Any + Send>,
+                      file_line: &(&'static str, uint)) -> ! {
     // Make sure the default failure handler is registered before we look at the
     // callbacks.
-    static INIT: Once = ONCE_INIT;
-    INIT.call_once(|| unsafe { register(failure::on_fail); });
+    unsafe {
+        static LOCK: Mutex = MUTEX_INIT;
+        static mut INIT: bool = false;
+        LOCK.lock();
+        if !INIT {
+            register(failure::on_fail);
+            INIT = true;
+        }
+        LOCK.unlock();
+    }
 
     // First, invoke call the user-defined callbacks triggered on thread panic.
     //
diff --git a/src/libstd/sys/common/helper_thread.rs b/src/libstd/sys/common/helper_thread.rs
index bdf1bf3dfd02c..09d22387c4478 100644
--- a/src/libstd/sys/common/helper_thread.rs
+++ b/src/libstd/sys/common/helper_thread.rs
@@ -20,6 +20,8 @@
 //! can be created in the future and there must be no active timers at that
 //! time.
 
+#![macro_escape]
+
 use prelude::v1::*;
 
 use cell::UnsafeCell;
@@ -69,6 +71,17 @@ struct RaceBox(helper_signal::signal);
 unsafe impl Send for RaceBox {}
 unsafe impl Sync for RaceBox {}
 
+macro_rules! helper_init { (static $name:ident: Helper<$m:ty>) => (
+    static $name: Helper<$m> = Helper {
+        lock: ::sync::MUTEX_INIT,
+        cond: ::sync::CONDVAR_INIT,
+        chan: ::cell::UnsafeCell { value: 0 as *mut Sender<$m> },
+        signal: ::cell::UnsafeCell { value: 0 },
+        initialized: ::cell::UnsafeCell { value: false },
+        shutdown: ::cell::UnsafeCell { value: false },
+    };
+) }
+
 impl<M: Send> Helper<M> {
     /// Lazily boots a helper thread, becoming a no-op if the helper has already
     /// been spawned.
@@ -85,7 +98,7 @@ impl<M: Send> Helper<M> {
     {
         unsafe {
             let _guard = self.lock.lock().unwrap();
-            if !*self.initialized.get() {
+            if *self.chan.get() as uint == 0 {
                 let (tx, rx) = channel();
                 *self.chan.get() = mem::transmute(box tx);
                 let (receive, send) = helper_signal::new();
@@ -94,15 +107,17 @@ impl<M: Send> Helper<M> {
                 let receive = RaceBox(receive);
 
                 let t = f();
-                Thread::spawn(move |:| {
+                Thread::spawn(move || {
                     helper(receive.0, rx, t);
                     let _g = self.lock.lock().unwrap();
                     *self.shutdown.get() = true;
                     self.cond.notify_one()
                 }).detach();
 
-                rt::at_exit(move|:| { self.shutdown() });
+                rt::at_exit(move || { self.shutdown() });
                 *self.initialized.get() = true;
+            } else if *self.chan.get() as uint == 1 {
+                panic!("cannot continue usage after shutdown");
             }
         }
     }
@@ -117,7 +132,9 @@ impl<M: Send> Helper<M> {
             // Must send and *then* signal to ensure that the child receives the
             // message. Otherwise it could wake up and go to sleep before we
             // send the message.
-            assert!(!self.chan.get().is_null());
+            assert!(*self.chan.get() as uint != 0);
+            assert!(*self.chan.get() as uint != 1,
+                    "cannot continue usage after shutdown");
             (**self.chan.get()).send(msg).unwrap();
             helper_signal::signal(*self.signal.get() as helper_signal::signal);
         }
@@ -130,9 +147,13 @@ impl<M: Send> Helper<M> {
             // returns.
             let mut guard = self.lock.lock().unwrap();
 
+            let ptr = *self.chan.get();
+            if ptr as uint == 1 {
+                panic!("cannot continue usage after shutdown");
+            }
             // Close the channel by destroying it
             let chan: Box<Sender<M>> = mem::transmute(*self.chan.get());
-            *self.chan.get() = 0 as *mut Sender<M>;
+            *self.chan.get() = 1 as *mut Sender<M>;
             drop(chan);
             helper_signal::signal(*self.signal.get() as helper_signal::signal);
 
diff --git a/src/libstd/sys/common/mod.rs b/src/libstd/sys/common/mod.rs
index 97015f74a4a10..fe9f669789566 100644
--- a/src/libstd/sys/common/mod.rs
+++ b/src/libstd/sys/common/mod.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 #![allow(missing_docs)]
-#![allow(dead_code)]
+#![macro_escape]
 
 use io::{mod, IoError, IoResult};
 use prelude::v1::*;
diff --git a/src/libstd/sys/common/mutex.rs b/src/libstd/sys/common/mutex.rs
index 567c26956efe9..322d2f202f772 100644
--- a/src/libstd/sys/common/mutex.rs
+++ b/src/libstd/sys/common/mutex.rs
@@ -29,6 +29,7 @@ impl Mutex {
     /// Behavior is undefined if the mutex is moved after the first method is
     /// called on the mutex.
     #[inline]
+    #[allow(dead_code)] // sys is not exported yet
     pub unsafe fn new() -> Mutex { Mutex(imp::Mutex::new()) }
 
     /// Lock the mutex blocking the current thread until it is available.
diff --git a/src/libstd/sys/common/net.rs b/src/libstd/sys/common/net.rs
index 94a2c9b78faef..2132f2b2b6d64 100644
--- a/src/libstd/sys/common/net.rs
+++ b/src/libstd/sys/common/net.rs
@@ -24,7 +24,9 @@ use ptr::{mod, null, null_mut};
 use sys::{mod, retry, c, sock_t, last_error, last_net_error, last_gai_error, close_sock,
           wrlen, msglen_t, os, wouldblock, set_nonblocking, timer, ms_to_timeval,
           decode_error_detailed};
-use sync::{Arc, Mutex, MutexGuard};
+use sync::{Arc, Mutex};
+#[cfg(not(target_os = "linux"))]
+use sync::MutexGuard;
 use sys_common::{mod, keep_going, short_write, timeout};
 use cmp;
 use io;
@@ -611,11 +613,13 @@ impl Drop for Inner {
     fn drop(&mut self) { unsafe { close_sock(self.fd); } }
 }
 
+#[cfg(not(target_os = "linux"))]
 pub struct Guard<'a> {
     pub fd: sock_t,
     pub guard: MutexGuard<'a, ()>,
 }
 
+#[cfg(not(target_os = "linux"))]
 #[unsafe_destructor]
 impl<'a> Drop for Guard<'a> {
     fn drop(&mut self) {
diff --git a/src/libstd/sys/common/rwlock.rs b/src/libstd/sys/common/rwlock.rs
index df016b9e293b7..b7c4cfcd0f5fe 100644
--- a/src/libstd/sys/common/rwlock.rs
+++ b/src/libstd/sys/common/rwlock.rs
@@ -26,6 +26,7 @@ impl RWLock {
     /// Usage of an RWLock is undefined if it is moved after its first use (any
     /// function calls below).
     #[inline]
+    #[allow(dead_code)] // sys is not exported yet
     pub unsafe fn new() -> RWLock { RWLock(imp::RWLock::new()) }
 
     /// Acquire shared access to the underlying lock, blocking the current
diff --git a/src/libstd/sys/common/stack.rs b/src/libstd/sys/common/stack.rs
index 2a88e20c8fa1f..1966a9544e1a5 100644
--- a/src/libstd/sys/common/stack.rs
+++ b/src/libstd/sys/common/stack.rs
@@ -121,37 +121,6 @@ pub unsafe fn record_os_managed_stack_bounds(stack_lo: uint, _stack_hi: uint) {
     record_sp_limit(stack_lo + RED_ZONE);
 }
 
-#[inline(always)]
-pub unsafe fn record_rust_managed_stack_bounds(stack_lo: uint, stack_hi: uint) {
-    // When the old runtime had segmented stacks, it used a calculation that was
-    // "limit + RED_ZONE + FUDGE". The red zone was for things like dynamic
-    // symbol resolution, llvm function calls, etc. In theory this red zone
-    // value is 0, but it matters far less when we have gigantic stacks because
-    // we don't need to be so exact about our stack budget. The "fudge factor"
-    // was because LLVM doesn't emit a stack check for functions < 256 bytes in
-    // size. Again though, we have giant stacks, so we round all these
-    // calculations up to the nice round number of 20k.
-    record_sp_limit(stack_lo + RED_ZONE);
-
-    return target_record_stack_bounds(stack_lo, stack_hi);
-
-    #[cfg(not(windows))] #[inline(always)]
-    unsafe fn target_record_stack_bounds(_stack_lo: uint, _stack_hi: uint) {}
-
-    #[cfg(all(windows, target_arch = "x86"))] #[inline(always)]
-    unsafe fn target_record_stack_bounds(stack_lo: uint, stack_hi: uint) {
-        // stack range is at TIB: %fs:0x04 (top) and %fs:0x08 (bottom)
-        asm!("mov $0, %fs:0x04" :: "r"(stack_hi) :: "volatile");
-        asm!("mov $0, %fs:0x08" :: "r"(stack_lo) :: "volatile");
-    }
-    #[cfg(all(windows, target_arch = "x86_64"))] #[inline(always)]
-    unsafe fn target_record_stack_bounds(stack_lo: uint, stack_hi: uint) {
-        // stack range is at TIB: %gs:0x08 (top) and %gs:0x10 (bottom)
-        asm!("mov $0, %gs:0x08" :: "r"(stack_hi) :: "volatile");
-        asm!("mov $0, %gs:0x10" :: "r"(stack_lo) :: "volatile");
-    }
-}
-
 /// Records the current limit of the stack as specified by `end`.
 ///
 /// This is stored in an OS-dependent location, likely inside of the thread
diff --git a/src/libstd/sys/common/thread_info.rs b/src/libstd/sys/common/thread_info.rs
index 92b936e74f654..dd1106fe0b192 100644
--- a/src/libstd/sys/common/thread_info.rs
+++ b/src/libstd/sys/common/thread_info.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![allow(dead_code)] // stack_guard isn't used right now on all platforms
+
 use core::prelude::*;
 
 use cell::RefCell;
@@ -16,10 +18,6 @@ use thread::Thread;
 use thread_local::State;
 
 struct ThreadInfo {
-    // This field holds the known bounds of the stack in (lo, hi)
-    // form. Not all threads necessarily know their precise bounds,
-    // hence this is optional.
-    stack_bounds: (uint, uint),
     stack_guard: uint,
     thread: Thread,
 }
@@ -36,7 +34,6 @@ impl ThreadInfo {
         THREAD_INFO.with(move |c| {
             if c.borrow().is_none() {
                 *c.borrow_mut() = Some(ThreadInfo {
-                    stack_bounds: (0, 0),
                     stack_guard: 0,
                     thread: NewThread::new(None),
                 })
@@ -54,10 +51,9 @@ pub fn stack_guard() -> uint {
     ThreadInfo::with(|info| info.stack_guard)
 }
 
-pub fn set(stack_bounds: (uint, uint), stack_guard: uint, thread: Thread) {
+pub fn set(stack_guard: uint, thread: Thread) {
     THREAD_INFO.with(|c| assert!(c.borrow().is_none()));
     THREAD_INFO.with(move |c| *c.borrow_mut() = Some(ThreadInfo{
-        stack_bounds: stack_bounds,
         stack_guard: stack_guard,
         thread: thread,
     }));
diff --git a/src/libstd/sys/common/thread_local.rs b/src/libstd/sys/common/thread_local.rs
index 9d7188a37bcdf..1ca64d288f803 100644
--- a/src/libstd/sys/common/thread_local.rs
+++ b/src/libstd/sys/common/thread_local.rs
@@ -55,11 +55,11 @@
 //! ```
 
 #![allow(non_camel_case_types)]
+#![allow(dead_code)] // sys isn't exported yet
 
 use prelude::v1::*;
 
 use sync::atomic::{mod, AtomicUint};
-use sync::{Mutex, Once, ONCE_INIT};
 
 use sys::thread_local as imp;
 
@@ -140,9 +140,6 @@ pub const INIT_INNER: StaticKeyInner = StaticKeyInner {
     key: atomic::ATOMIC_UINT_INIT,
 };
 
-static INIT_KEYS: Once = ONCE_INIT;
-static mut KEYS: *mut Mutex<Vec<imp::Key>> = 0 as *mut _;
-
 impl StaticKey {
     /// Gets the value associated with this TLS key
     ///
diff --git a/src/libstd/sys/unix/backtrace.rs b/src/libstd/sys/unix/backtrace.rs
index 9e26475f814b7..b0fca87d73630 100644
--- a/src/libstd/sys/unix/backtrace.rs
+++ b/src/libstd/sys/unix/backtrace.rs
@@ -83,12 +83,12 @@
 /// to symbols. This is a bit of a hokey implementation as-is, but it works for
 /// all unix platforms we support right now, so it at least gets the job done.
 
+use prelude::v1::*;
+
 use c_str::CString;
-use io::{IoResult, Writer};
+use io::IoResult;
 use libc;
 use mem;
-use option::Option::{mod, Some, None};
-use result::Result::{Ok, Err};
 use sync::{StaticMutex, MUTEX_INIT};
 
 use sys_common::backtrace::*;
@@ -151,7 +151,7 @@ pub fn write(w: &mut Writer) -> IoResult<()> {
     // I/O done here is blocking I/O, not green I/O, so we don't have to
     // worry about this being a native vs green mutex.
     static LOCK: StaticMutex = MUTEX_INIT;
-    let _g = unsafe { LOCK.lock() };
+    let _g = LOCK.lock();
 
     try!(writeln!(w, "stack backtrace:"));
 
@@ -241,12 +241,8 @@ fn print(w: &mut Writer, idx: int, addr: *mut libc::c_void) -> IoResult<()> {
 
 #[cfg(not(any(target_os = "macos", target_os = "ios")))]
 fn print(w: &mut Writer, idx: int, addr: *mut libc::c_void) -> IoResult<()> {
-    use iter::{Iterator, IteratorExt};
     use os;
-    use path::GenericPath;
-    use ptr::PtrExt;
     use ptr;
-    use slice::SliceExt;
 
     ////////////////////////////////////////////////////////////////////////
     // libbacktrace.h API
diff --git a/src/libstd/sys/unix/mod.rs b/src/libstd/sys/unix/mod.rs
index 4199cbc1bb9f5..46a1bf31c00b4 100644
--- a/src/libstd/sys/unix/mod.rs
+++ b/src/libstd/sys/unix/mod.rs
@@ -10,30 +10,14 @@
 
 #![allow(missing_docs)]
 #![allow(non_camel_case_types)]
-#![allow(unused_imports)]
-#![allow(dead_code)]
-#![allow(unused_unsafe)]
-#![allow(unused_mut)]
 
 extern crate libc;
 
-use num;
 use num::{Int, SignedInt};
 use prelude::v1::*;
 use io::{mod, IoResult, IoError};
 use sys_common::mkerr_libc;
 
-macro_rules! helper_init { (static $name:ident: Helper<$m:ty>) => (
-    static $name: Helper<$m> = Helper {
-        lock: ::sync::MUTEX_INIT,
-        cond: ::sync::CONDVAR_INIT,
-        chan: ::cell::UnsafeCell { value: 0 as *mut Sender<$m> },
-        signal: ::cell::UnsafeCell { value: 0 },
-        initialized: ::cell::UnsafeCell { value: false },
-        shutdown: ::cell::UnsafeCell { value: false },
-    };
-) }
-
 pub mod backtrace;
 pub mod c;
 pub mod ext;
diff --git a/src/libstd/sys/unix/mutex.rs b/src/libstd/sys/unix/mutex.rs
index 81f8659d6ae08..c9cb46b0289f1 100644
--- a/src/libstd/sys/unix/mutex.rs
+++ b/src/libstd/sys/unix/mutex.rs
@@ -11,7 +11,6 @@
 use cell::UnsafeCell;
 use kinds::Sync;
 use sys::sync as ffi;
-use sys_common::mutex;
 
 pub struct Mutex { inner: UnsafeCell<ffi::pthread_mutex_t> }
 
@@ -26,6 +25,7 @@ pub const MUTEX_INIT: Mutex = Mutex {
 
 unsafe impl Sync for Mutex {}
 
+#[allow(dead_code)] // sys isn't exported yet
 impl Mutex {
     #[inline]
     pub unsafe fn new() -> Mutex {
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 6a8f55e79c872..d838ff82905fe 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -10,17 +10,16 @@
 
 //! Implementation of `std::os` functionality for unix systems
 
+#![allow(unused_imports)] // lots of cfg code here
+
 use prelude::v1::*;
 
 use c_str::ToCStr;
-use error::{FromError, Error};
-use fmt;
 use io::{IoError, IoResult};
-use libc::{mod, c_int, c_char, c_void};
+use libc::{mod, c_int, c_char};
 use os;
-use path::{BytesContainer};
+use path::BytesContainer;
 use ptr;
-use sync::atomic::{AtomicInt, SeqCst};
 use sys::fs::FileDesc;
 
 use os::TMPBUF_SZ;
diff --git a/src/libstd/sys/unix/pipe.rs b/src/libstd/sys/unix/pipe.rs
index 623f3f6a89c9d..e4fd36d8abc12 100644
--- a/src/libstd/sys/unix/pipe.rs
+++ b/src/libstd/sys/unix/pipe.rs
@@ -142,7 +142,7 @@ impl UnixStream {
     fn lock_nonblocking<'a>(&'a self) -> Guard<'a> {
         let ret = Guard {
             fd: self.fd(),
-            guard: unsafe { self.inner.lock.lock().unwrap() },
+            guard: self.inner.lock.lock().unwrap(),
         };
         assert!(set_nonblocking(self.fd(), true).is_ok());
         ret
diff --git a/src/libstd/sys/unix/process.rs b/src/libstd/sys/unix/process.rs
index af09bf4fbd0a2..b9b43389be7c1 100644
--- a/src/libstd/sys/unix/process.rs
+++ b/src/libstd/sys/unix/process.rs
@@ -12,10 +12,10 @@ use prelude::v1::*;
 use self::Req::*;
 
 use c_str::{CString, ToCStr};
-use collections;
+use collections::HashMap;
 use hash::Hash;
 use io::process::{ProcessExit, ExitStatus, ExitSignal};
-use io::{mod, IoResult, IoError, EndOfFile};
+use io::{IoResult, EndOfFile};
 use libc::{mod, pid_t, c_void, c_int};
 use mem;
 use os;
@@ -328,7 +328,7 @@ impl Process {
         // The actual communication between the helper thread and this thread is
         // quite simple, just a channel moving data around.
 
-        unsafe { HELPER.boot(register_sigchld, waitpid_helper) }
+        HELPER.boot(register_sigchld, waitpid_helper);
 
         match self.try_wait() {
             Some(ret) => return Ok(ret),
@@ -336,7 +336,7 @@ impl Process {
         }
 
         let (tx, rx) = channel();
-        unsafe { HELPER.send(NewChild(self.pid, tx, deadline)); }
+        HELPER.send(NewChild(self.pid, tx, deadline));
         return match rx.recv() {
             Ok(e) => Ok(e),
             Err(..) => Err(timeout("wait timed out")),
@@ -420,8 +420,15 @@ impl Process {
                             Ok(NewChild(pid, tx, deadline)) => {
                                 active.push((pid, tx, deadline));
                             }
+                            // Once we've been disconnected it means the main
+                            // thread is exiting (at_exit has run). We could
+                            // still have active waiter for other threads, so
+                            // we're just going to drop them all on the floor.
+                            // This means that they won't receive a "you're
+                            // done" message in which case they'll be considered
+                            // as timed out, but more generally errors will
+                            // start propagating.
                             Err(TryRecvError::Disconnected) => {
-                                assert!(active.len() == 0);
                                 break 'outer;
                             }
                             Err(TryRecvError::Empty) => break,
@@ -553,7 +560,7 @@ fn with_argv<T,F>(prog: &CString, args: &[CString],
     cb(ptrs.as_ptr())
 }
 
-fn with_envp<K,V,T,F>(env: Option<&collections::HashMap<K, V>>,
+fn with_envp<K,V,T,F>(env: Option<&HashMap<K, V>>,
                       cb: F)
                       -> T
     where F : FnOnce(*const c_void) -> T,
diff --git a/src/libstd/sys/unix/rwlock.rs b/src/libstd/sys/unix/rwlock.rs
index 0d63ff14ff26b..4f9b06685ec0c 100644
--- a/src/libstd/sys/unix/rwlock.rs
+++ b/src/libstd/sys/unix/rwlock.rs
@@ -17,6 +17,7 @@ pub const RWLOCK_INIT: RWLock = RWLock {
     inner: UnsafeCell { value: ffi::PTHREAD_RWLOCK_INITIALIZER },
 };
 
+#[allow(dead_code)] // sys isn't exported yet
 impl RWLock {
     #[inline]
     pub unsafe fn new() -> RWLock {
diff --git a/src/libstd/sys/unix/stack_overflow.rs b/src/libstd/sys/unix/stack_overflow.rs
index 95ab9b459d671..647619fa23161 100644
--- a/src/libstd/sys/unix/stack_overflow.rs
+++ b/src/libstd/sys/unix/stack_overflow.rs
@@ -34,7 +34,6 @@ impl Drop for Handler {
 
 #[cfg(any(target_os = "linux", target_os = "macos"))]
 mod imp {
-    use core::prelude::*;
     use sys_common::stack;
 
     use super::Handler;
diff --git a/src/libstd/sys/unix/tcp.rs b/src/libstd/sys/unix/tcp.rs
index 13ccf685fd7fc..26c2bb8ed600e 100644
--- a/src/libstd/sys/unix/tcp.rs
+++ b/src/libstd/sys/unix/tcp.rs
@@ -136,10 +136,6 @@ impl TcpAcceptor {
         Err(sys_common::eof())
     }
 
-    pub fn socket_name(&mut self) -> IoResult<ip::SocketAddr> {
-        net::sockname(self.fd(), libc::getsockname)
-    }
-
     pub fn set_timeout(&mut self, timeout: Option<u64>) {
         self.deadline = timeout.map(|a| sys::timer::now() + a).unwrap_or(0);
     }
diff --git a/src/libstd/sys/unix/timer.rs b/src/libstd/sys/unix/timer.rs
index 80f93dd2f618c..8cd69f236cf34 100644
--- a/src/libstd/sys/unix/timer.rs
+++ b/src/libstd/sys/unix/timer.rs
@@ -100,7 +100,7 @@ pub fn now() -> u64 {
 fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
     let mut set: c::fd_set = unsafe { mem::zeroed() };
 
-    let mut fd = FileDesc::new(input, true);
+    let fd = FileDesc::new(input, true);
     let mut timeout: libc::timeval = unsafe { mem::zeroed() };
 
     // active timers are those which are able to be selected upon (and it's a
@@ -168,8 +168,15 @@ fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
             1 => {
                 loop {
                     match messages.try_recv() {
+                        // Once we've been disconnected it means the main thread
+                        // is exiting (at_exit has run). We could still have
+                        // active timers for other threads, so we're just going
+                        // to drop them all on the floor. This is all we can
+                        // really do, however, to prevent resource leakage. The
+                        // remaining timers will likely start panicking quickly
+                        // as they attempt to re-use this thread but are
+                        // disallowed to do so.
                         Err(TryRecvError::Disconnected) => {
-                            assert!(active.len() == 0);
                             break 'outer;
                         }
 
diff --git a/src/libstd/sys/unix/tty.rs b/src/libstd/sys/unix/tty.rs
index 4ef687d41d8ee..d8cb067b946a6 100644
--- a/src/libstd/sys/unix/tty.rs
+++ b/src/libstd/sys/unix/tty.rs
@@ -44,5 +44,4 @@ impl TTY {
     pub fn get_winsize(&mut self) -> IoResult<(int, int)> {
         Err(sys_common::unimpl())
     }
-    pub fn isatty(&self) -> bool { false }
 }
diff --git a/src/libstd/sys/windows/backtrace.rs b/src/libstd/sys/windows/backtrace.rs
index 319a458087b9b..ee80ae731a36d 100644
--- a/src/libstd/sys/windows/backtrace.rs
+++ b/src/libstd/sys/windows/backtrace.rs
@@ -7,19 +7,22 @@
 // <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.
-/// As always, windows has something very different than unix, we mainly want
-/// to avoid having to depend too much on libunwind for windows.
-///
-/// If you google around, you'll find a fair bit of references to built-in
-/// functions to get backtraces on windows. It turns out that most of these are
-/// in an external library called dbghelp. I was unable to find this library
-/// via `-ldbghelp`, but it is apparently normal to do the `dlopen` equivalent
-/// of it.
-///
-/// You'll also find that there's a function called CaptureStackBackTrace
-/// mentioned frequently (which is also easy to use), but sadly I didn't have a
-/// copy of that function in my mingw install (maybe it was broken?). Instead,
-/// this takes the route of using StackWalk64 in order to walk the stack.
+
+//! As always, windows has something very different than unix, we mainly want
+//! to avoid having to depend too much on libunwind for windows.
+//!
+//! If you google around, you'll find a fair bit of references to built-in
+//! functions to get backtraces on windows. It turns out that most of these are
+//! in an external library called dbghelp. I was unable to find this library
+//! via `-ldbghelp`, but it is apparently normal to do the `dlopen` equivalent
+//! of it.
+//!
+//! You'll also find that there's a function called CaptureStackBackTrace
+//! mentioned frequently (which is also easy to use), but sadly I didn't have a
+//! copy of that function in my mingw install (maybe it was broken?). Instead,
+//! this takes the route of using StackWalk64 in order to walk the stack.
+
+#![allow(dead_code)] // constants/fields aren't always used on all platforms
 
 use c_str::CString;
 use intrinsics;
@@ -294,7 +297,7 @@ pub fn write(w: &mut Writer) -> IoResult<()> {
     // According to windows documentation, all dbghelp functions are
     // single-threaded.
     static LOCK: StaticMutex = MUTEX_INIT;
-    let _g = unsafe { LOCK.lock() };
+    let _g = LOCK.lock();
 
     // Open up dbghelp.dll, we don't link to it explicitly because it can't
     // always be found. Additionally, it's nice having fewer dependencies.
diff --git a/src/libstd/sys/windows/c.rs b/src/libstd/sys/windows/c.rs
index 1ee57434fb91a..b563c356a7634 100644
--- a/src/libstd/sys/windows/c.rs
+++ b/src/libstd/sys/windows/c.rs
@@ -15,7 +15,6 @@
 #![allow(non_camel_case_types)]
 
 use libc;
-use prelude::v1::*;
 
 pub const WSADESCRIPTION_LEN: uint = 256;
 pub const WSASYS_STATUS_LEN: uint = 128;
diff --git a/src/libstd/sys/windows/fs.rs b/src/libstd/sys/windows/fs.rs
index 523d60c71aa8b..e893a7dea6b78 100644
--- a/src/libstd/sys/windows/fs.rs
+++ b/src/libstd/sys/windows/fs.rs
@@ -10,21 +10,17 @@
 
 //! Blocking Windows-based file I/O
 
-use alloc::arc::Arc;
 use libc::{mod, c_int};
 
-use c_str::CString;
+use io;
 use mem;
-use sys::os::fill_utf16_buf_and_decode;
-use path;
 use ptr;
-use str;
-use io;
+use sys::os::fill_utf16_buf_and_decode;
 
 use prelude::v1::*;
 use sys;
 use sys::os;
-use sys_common::{keep_going, eof, mkerr_libc};
+use sys_common::{unimpl, mkerr_libc};
 
 use io::{FilePermission, Write, UnstableFileStat, Open, FileAccess, FileMode};
 use io::{IoResult, IoError, FileStat, SeekStyle};
@@ -445,7 +441,7 @@ pub fn stat(p: &Path) -> IoResult<FileStat> {
 // FIXME: move this to platform-specific modules (for now)?
 pub fn lstat(_p: &Path) -> IoResult<FileStat> {
     // FIXME: implementation is missing
-    Err(super::unimpl())
+    Err(unimpl())
 }
 
 pub fn utime(p: &Path, atime: u64, mtime: u64) -> IoResult<()> {
diff --git a/src/libstd/sys/windows/mod.rs b/src/libstd/sys/windows/mod.rs
index 1034f0615d994..797a4db2de39c 100644
--- a/src/libstd/sys/windows/mod.rs
+++ b/src/libstd/sys/windows/mod.rs
@@ -11,31 +11,14 @@
 #![allow(missing_docs)]
 #![allow(non_camel_case_types)]
 #![allow(non_snake_case)]
-#![allow(unused_imports)]
-#![allow(dead_code)]
-#![allow(unused_unsafe)]
-#![allow(unused_mut)]
-
-extern crate libc;
 
 use prelude::v1::*;
 
-use num;
-use mem;
 use io::{mod, IoResult, IoError};
+use libc;
+use mem;
 use sync::{Once, ONCE_INIT};
 
-macro_rules! helper_init { (static $name:ident: Helper<$m:ty>) => (
-    static $name: Helper<$m> = Helper {
-        lock: ::sync::MUTEX_INIT,
-        cond: ::sync::CONDVAR_INIT,
-        chan: ::cell::UnsafeCell { value: 0 as *mut ::sync::mpsc::Sender<$m> },
-        signal: ::cell::UnsafeCell { value: 0 },
-        initialized: ::cell::UnsafeCell { value: false },
-        shutdown: ::cell::UnsafeCell { value: false },
-    };
-) }
-
 pub mod backtrace;
 pub mod c;
 pub mod ext;
@@ -181,14 +164,6 @@ pub fn init_net() {
     }
 }
 
-pub fn unimpl() -> IoError {
-    IoError {
-        kind: io::IoUnavailable,
-        desc: "operation is not implemented",
-        detail: None,
-    }
-}
-
 pub fn to_utf16(s: Option<&str>) -> IoResult<Vec<u16>> {
     match s {
         Some(s) => Ok({
diff --git a/src/libstd/sys/windows/os.rs b/src/libstd/sys/windows/os.rs
index dfdee0e0385c5..825d5699ab7d2 100644
--- a/src/libstd/sys/windows/os.rs
+++ b/src/libstd/sys/windows/os.rs
@@ -15,7 +15,6 @@
 
 use prelude::v1::*;
 
-use fmt;
 use io::{IoResult, IoError};
 use iter::repeat;
 use libc::{c_int, c_void};
diff --git a/src/libstd/sys/windows/pipe.rs b/src/libstd/sys/windows/pipe.rs
index f173d5fc6d4cb..17fe8d5ce76e0 100644
--- a/src/libstd/sys/windows/pipe.rs
+++ b/src/libstd/sys/windows/pipe.rs
@@ -365,7 +365,7 @@ impl UnixStream {
         // acquire the lock.
         //
         // See comments in close_read() about why this lock is necessary.
-        let guard = unsafe { self.inner.lock.lock() };
+        let guard = self.inner.lock.lock();
         if self.read_closed() {
             return Err(eof())
         }
@@ -441,7 +441,7 @@ impl UnixStream {
             // going after we woke up.
             //
             // See comments in close_read() about why this lock is necessary.
-            let guard = unsafe { self.inner.lock.lock() };
+            let guard = self.inner.lock.lock();
             if self.write_closed() {
                 return Err(epipe())
             }
@@ -516,14 +516,14 @@ impl UnixStream {
         // close_read() between steps 1 and 2. By atomically executing steps 1
         // and 2 with a lock with respect to close_read(), we're guaranteed that
         // no thread will erroneously sit in a read forever.
-        let _guard = unsafe { self.inner.lock.lock() };
+        let _guard = self.inner.lock.lock();
         self.inner.read_closed.store(true, atomic::SeqCst);
         self.cancel_io()
     }
 
     pub fn close_write(&mut self) -> IoResult<()> {
         // see comments in close_read() for why this lock is necessary
-        let _guard = unsafe { self.inner.lock.lock() };
+        let _guard = self.inner.lock.lock();
         self.inner.write_closed.store(true, atomic::SeqCst);
         self.cancel_io()
     }
diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index cb99a886ce4fc..42086106f7708 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -10,24 +10,22 @@
 
 use prelude::v1::*;
 
-use libc::{pid_t, c_void, c_int};
+use libc::{pid_t, c_void};
 use libc;
 use c_str::{CString, ToCStr};
 use io;
 use mem;
 use os;
 use ptr;
-use io::process::{ProcessExit, ExitStatus, ExitSignal};
+use io::process::{ProcessExit, ExitStatus};
 use collections;
 use path::BytesContainer;
 use hash::Hash;
 use io::{IoResult, IoError};
 
-use sys::fs;
-use sys::{mod, retry, c, wouldblock, set_nonblocking, ms_to_timeval, timer};
+use sys::timer;
 use sys::fs::FileDesc;
-use sys_common::helper_thread::Helper;
-use sys_common::{AsInner, mkerr_libc, timeout};
+use sys_common::{AsInner, timeout};
 
 use io::fs::PathExtensions;
 
@@ -122,8 +120,6 @@ impl Process {
         use libc::funcs::extra::msvcrt::get_osfhandle;
 
         use mem;
-        use iter::{Iterator, IteratorExt};
-        use str::StrExt;
 
         if cfg.gid().is_some() || cfg.uid().is_some() {
             return Err(IoError {
diff --git a/src/libstd/sys/windows/stack_overflow.rs b/src/libstd/sys/windows/stack_overflow.rs
index e8b447022cbf4..67f185a2e4d32 100644
--- a/src/libstd/sys/windows/stack_overflow.rs
+++ b/src/libstd/sys/windows/stack_overflow.rs
@@ -14,7 +14,7 @@ use ptr;
 use mem;
 use libc;
 use libc::types::os::arch::extra::{LPVOID, DWORD, LONG, BOOL};
-use sys_common::{stack, thread_info};
+use sys_common::stack;
 
 pub struct Handler {
     _data: *mut libc::c_void
@@ -30,14 +30,6 @@ impl Drop for Handler {
     fn drop(&mut self) {}
 }
 
-// get_task_info is called from an exception / signal handler.
-// It returns the guard page of the current task or 0 if that
-// guard page doesn't exist. None is returned if there's currently
-// no local task.
-unsafe fn get_task_guard_page() -> uint {
-    thread_info::stack_guard()
-}
-
 // This is initialized in init() and only read from after
 static mut PAGE_SIZE: uint = 0;
 
diff --git a/src/libstd/sys/windows/tcp.rs b/src/libstd/sys/windows/tcp.rs
index 5a929f6b2b5ff..ce241f05a533b 100644
--- a/src/libstd/sys/windows/tcp.rs
+++ b/src/libstd/sys/windows/tcp.rs
@@ -8,17 +8,17 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use prelude::v1::*;
+
 use io::net::ip;
 use io::IoResult;
 use libc;
 use mem;
 use ptr;
-use prelude::v1::*;
-use super::{last_error, last_net_error, retry, sock_t};
+use super::{last_error, last_net_error, sock_t};
 use sync::{Arc, atomic};
-use sys::fs::FileDesc;
 use sys::{mod, c, set_nonblocking, wouldblock, timer};
-use sys_common::{mod, timeout, eof, net};
+use sys_common::{timeout, eof, net};
 
 pub use sys_common::net::TcpStream;
 
@@ -205,10 +205,6 @@ impl TcpAcceptor {
         Err(eof())
     }
 
-    pub fn socket_name(&mut self) -> IoResult<ip::SocketAddr> {
-        net::sockname(self.socket(), libc::getsockname)
-    }
-
     pub fn set_timeout(&mut self, timeout: Option<u64>) {
         self.deadline = timeout.map(|a| timer::now() + a).unwrap_or(0);
     }
diff --git a/src/libstd/sys/windows/thread.rs b/src/libstd/sys/windows/thread.rs
index 4498f56c00a1e..59ab5f5c4d990 100644
--- a/src/libstd/sys/windows/thread.rs
+++ b/src/libstd/sys/windows/thread.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use core::prelude::*;
-
 use boxed::Box;
 use cmp;
 use mem;
diff --git a/src/libstd/sys/windows/thread_local.rs b/src/libstd/sys/windows/thread_local.rs
index b96e26c7a86a6..8d0f413b4db08 100644
--- a/src/libstd/sys/windows/thread_local.rs
+++ b/src/libstd/sys/windows/thread_local.rs
@@ -137,9 +137,9 @@ unsafe fn init_dtors() {
     rt::at_exit(move|| {
         DTOR_LOCK.lock();
         let dtors = DTORS;
-        DTORS = 0 as *mut _;
+        DTORS = 1 as *mut _;
         mem::transmute::<_, Box<Vec<(Key, Dtor)>>>(dtors);
-        assert!(DTORS.is_null()); // can't re-init after destructing
+        assert!(DTORS as uint == 1); // can't re-init after destructing
         DTOR_LOCK.unlock();
     });
 }
@@ -147,6 +147,9 @@ unsafe fn init_dtors() {
 unsafe fn register_dtor(key: Key, dtor: Dtor) {
     DTOR_LOCK.lock();
     init_dtors();
+    assert!(DTORS as uint != 0);
+    assert!(DTORS as uint != 1,
+            "cannot create new TLS keys after the main thread has exited");
     (*DTORS).push((key, dtor));
     DTOR_LOCK.unlock();
 }
@@ -154,6 +157,9 @@ unsafe fn register_dtor(key: Key, dtor: Dtor) {
 unsafe fn unregister_dtor(key: Key) -> bool {
     DTOR_LOCK.lock();
     init_dtors();
+    assert!(DTORS as uint != 0);
+    assert!(DTORS as uint != 1,
+            "cannot unregister destructors after the main thread has exited");
     let ret = {
         let dtors = &mut *DTORS;
         let before = dtors.len();
@@ -232,6 +238,7 @@ unsafe extern "system" fn on_tls_callback(h: LPVOID,
     }
 }
 
+#[allow(dead_code)] // not actually dead
 unsafe fn run_dtors() {
     let mut any_run = true;
     for _ in range(0, 5i) {
diff --git a/src/libstd/sys/windows/timer.rs b/src/libstd/sys/windows/timer.rs
index 343b78543bfd0..f026cf72cb92f 100644
--- a/src/libstd/sys/windows/timer.rs
+++ b/src/libstd/sys/windows/timer.rs
@@ -20,17 +20,14 @@
 //! Other than that, the implementation is pretty straightforward in terms of
 //! the other two implementations of timers with nothing *that* new showing up.
 
-use self::Req::*;
 use prelude::v1::*;
+use self::Req::*;
 
 use libc;
 use ptr;
-
 use io::IoResult;
-use sync::mpsc::{channel, Sender, Receiver, TryRecvError};
-use sys::c;
-use sys::fs::FileDesc;
 use sys_common::helper_thread::Helper;
+use sync::mpsc::{channel, TryRecvError, Sender, Receiver};
 
 helper_init! { static HELPER: Helper<Req> }
 
@@ -80,9 +77,10 @@ fn helper(input: libc::HANDLE, messages: Receiver<Req>, _: ()) {
                             None => {}
                         }
                     }
+                    // See the comment in unix::timer for why we don't have any
+                    // asserts here and why we're likely just leaving timers on
+                    // the floor as we exit.
                     Err(TryRecvError::Disconnected) => {
-                        assert_eq!(objs.len(), 1);
-                        assert_eq!(chans.len(), 0);
                         break 'outer;
                     }
                     Err(..) => break
diff --git a/src/libstd/sys/windows/tty.rs b/src/libstd/sys/windows/tty.rs
index 7591025d76d6f..393e3cd4f2a85 100644
--- a/src/libstd/sys/windows/tty.rs
+++ b/src/libstd/sys/windows/tty.rs
@@ -37,9 +37,10 @@ use str::from_utf8;
 use super::c::{ENABLE_ECHO_INPUT, ENABLE_EXTENDED_FLAGS};
 use super::c::{ENABLE_INSERT_MODE, ENABLE_LINE_INPUT};
 use super::c::{ENABLE_PROCESSED_INPUT, ENABLE_QUICK_EDIT_MODE};
-use super::c::{ERROR_ILLEGAL_CHARACTER};
 use super::c::{ReadConsoleW, WriteConsoleW, GetConsoleMode, SetConsoleMode};
 
+use sys_common::unimpl;
+
 fn invalid_encoding() -> IoError {
     IoError {
         kind: io::InvalidInput,
@@ -151,11 +152,8 @@ impl TTY {
         // Make a CONSOLE_SCREEN_BUFFER_INFO
         // Call GetConsoleScreenBufferInfo
         // Maybe call GetLargestConsoleWindowSize instead?
-        Err(super::unimpl())
+        Err(unimpl())
     }
-
-    // Let us magically declare this as a TTY
-    pub fn isatty(&self) -> bool { true }
 }
 
 impl Drop for TTY {
diff --git a/src/libstd/thread.rs b/src/libstd/thread.rs
index 3c87309dabcf3..97f61b08bcbcc 100644
--- a/src/libstd/thread.rs
+++ b/src/libstd/thread.rs
@@ -232,13 +232,10 @@ impl Builder {
             let my_stack_top = addr as uint;
             let my_stack_bottom = my_stack_top - stack_size + 1024;
             unsafe {
-                stack::record_os_managed_stack_bounds(my_stack_bottom, my_stack_top);
+                stack::record_os_managed_stack_bounds(my_stack_bottom,
+                                                      my_stack_top);
+                thread_info::set(imp::guard::current(), their_thread);
             }
-            thread_info::set(
-                (my_stack_bottom, my_stack_top),
-                unsafe { imp::guard::current() },
-                their_thread
-            );
 
             let mut output = None;
             let f: Thunk<(), T> = if stdout.is_some() || stderr.is_some() {