std: Re-enable at_exit()

The new semantics of this function are that the callbacks are run when the *main
thread* exits, not when all threads have exited. This implies that other threads
may still be running when the `at_exit` callbacks are invoked and users need to
be prepared for this situation.

Users in the standard library have been audited in accordance to these new rules
as well.

Closes #20012

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.

src/libstd/sys/windows/c.rs

@@ -15,7 +15,6 @@
 #![allow(non_camel_case_types)]
 
 use libc;
-use prelude::*;
 
 pub const WSADESCRIPTION_LEN: uint = 256;
 pub const WSASYS_STATUS_LEN: uint = 128;

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 mem;
-use sys::os::fill_utf16_buf_and_decode;
-use path;
-use ptr;
-use str;
 use io;
+use mem;
+use ptr;
+use sys::os::fill_utf16_buf_and_decode;
 
 use prelude::*;
 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<()> {

src/libstd/sys/windows/mod.rs

@@ -11,30 +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 num;
 use mem;
 use prelude::*;
 use io::{mod, IoResult, IoError};
 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 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;
@@ -179,14 +163,6 @@ 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({

src/libstd/sys/windows/os.rs

@@ -15,14 +15,12 @@
 
 use prelude::*;
 
-use fmt;
 use io::{IoResult, IoError};
-use libc::{c_int, c_char, c_void};
+use libc::{c_int, c_void};
 use libc;
 use os;
 use path::BytesContainer;
 use ptr;
-use sync::atomic::{AtomicInt, INIT_ATOMIC_INT, SeqCst};
 use sys::fs::FileDesc;
 use slice;
 

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()
     }

src/libstd/sys/windows/process.rs

@@ -8,25 +8,24 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use libc::{pid_t, c_void, c_int};
+use prelude::*;
+
+use libc::{pid_t, c_void};
 use libc;
 use c_str::CString;
 use io;
 use mem;
 use os;
 use ptr;
-use prelude::*;
-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;
 
@@ -121,8 +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 {

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;
 

src/libstd/sys/windows/tcp.rs

@@ -14,11 +14,10 @@ use libc;
 use mem;
 use ptr;
 use prelude::*;
-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 +204,6 @@ 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);
     }

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;

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) {

src/libstd/sys/windows/timer.rs

@@ -26,8 +26,6 @@ use libc;
 use ptr;
 use comm;
 
-use sys::c;
-use sys::fs::FileDesc;
 use sys_common::helper_thread::Helper;
 use prelude::*;
 use io::IoResult;
@@ -80,9 +78,10 @@ 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(comm::Disconnected) => {
-                        assert_eq!(objs.len(), 1);
-                        assert_eq!(chans.len(), 0);
                         break 'outer;
                     }
                     Err(..) => break

src/libstd/sys/windows/tty.rs

@@ -26,7 +26,6 @@
 //! to working in raw UTF-16, with such a wrapper around it.
 
 use super::c::{ReadConsoleW, WriteConsoleW, GetConsoleMode, SetConsoleMode};
-use super::c::{ERROR_ILLEGAL_CHARACTER};
 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};
@@ -38,6 +37,8 @@ use prelude::*;
 use ptr;
 use str::from_utf8;
 
+use sys_common::unimpl;
+
 fn invalid_encoding() -> IoError {
     IoError {
         kind: io::InvalidInput,
@@ -149,11 +150,8 @@ 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 {