8 files changed, 66 insertions, 244 deletions

diff --git a/library/std/src/sys_common/condvar.rs b/library/std/src/sys_common/condvar.rs
deleted file mode 100644
index 8bc5b2411..000000000
--- a/library/std/src/sys_common/condvar.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-use crate::sys::locks as imp;
-use crate::sys_common::mutex::MovableMutex;
-use crate::time::Duration;
-
-mod check;
-
-type CondvarCheck = <imp::MovableMutex as check::CondvarCheck>::Check;
-
-/// An OS-based condition variable.
-pub struct Condvar {
-    inner: imp::MovableCondvar,
-    check: CondvarCheck,
-}
-
-impl Condvar {
-    /// Creates a new condition variable for use.
-    #[inline]
-    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
-    pub const fn new() -> Self {
-        Self { inner: imp::MovableCondvar::new(), check: CondvarCheck::new() }
-    }
-
-    /// Signals one waiter on this condition variable to wake up.
-    #[inline]
-    pub fn notify_one(&self) {
-        unsafe { self.inner.notify_one() };
-    }
-
-    /// Awakens all current waiters on this condition variable.
-    #[inline]
-    pub fn notify_all(&self) {
-        unsafe { self.inner.notify_all() };
-    }
-
-    /// Waits for a signal on the specified mutex.
-    ///
-    /// Behavior is undefined if the mutex is not locked by the current thread.
-    ///
-    /// May panic if used with more than one mutex.
-    #[inline]
-    pub unsafe fn wait(&self, mutex: &MovableMutex) {
-        self.check.verify(mutex);
-        self.inner.wait(mutex.raw())
-    }
-
-    /// Waits for a signal on the specified mutex with a timeout duration
-    /// specified by `dur` (a relative time into the future).
-    ///
-    /// Behavior is undefined if the mutex is not locked by the current thread.
-    ///
-    /// May panic if used with more than one mutex.
-    #[inline]
-    pub unsafe fn wait_timeout(&self, mutex: &MovableMutex, dur: Duration) -> bool {
-        self.check.verify(mutex);
-        self.inner.wait_timeout(mutex.raw(), dur)
-    }
-}
diff --git a/library/std/src/sys_common/condvar/check.rs b/library/std/src/sys_common/condvar/check.rs
deleted file mode 100644
index 4ac9e62bf..000000000
--- a/library/std/src/sys_common/condvar/check.rs
+++ /dev/null
@@ -1,58 +0,0 @@
-use crate::ptr;
-use crate::sync::atomic::{AtomicPtr, Ordering};
-use crate::sys::locks as imp;
-use crate::sys_common::lazy_box::{LazyBox, LazyInit};
-use crate::sys_common::mutex::MovableMutex;
-
-pub trait CondvarCheck {
-    type Check;
-}
-
-/// For boxed mutexes, a `Condvar` will check it's only ever used with the same
-/// mutex, based on its (stable) address.
-impl<T: LazyInit> CondvarCheck for LazyBox<T> {
-    type Check = SameMutexCheck;
-}
-
-pub struct SameMutexCheck {
-    addr: AtomicPtr<()>,
-}
-
-#[allow(dead_code)]
-impl SameMutexCheck {
-    pub const fn new() -> Self {
-        Self { addr: AtomicPtr::new(ptr::null_mut()) }
-    }
-    pub fn verify(&self, mutex: &MovableMutex) {
-        let addr = mutex.raw() as *const imp::Mutex as *const () as *mut _;
-        // Relaxed is okay here because we never read through `self.addr`, and only use it to
-        // compare addresses.
-        match self.addr.compare_exchange(
-            ptr::null_mut(),
-            addr,
-            Ordering::Relaxed,
-            Ordering::Relaxed,
-        ) {
-            Ok(_) => {}               // Stored the address
-            Err(n) if n == addr => {} // Lost a race to store the same address
-            _ => panic!("attempted to use a condition variable with two mutexes"),
-        }
-    }
-}
-
-/// Unboxed mutexes may move, so `Condvar` can not require its address to stay
-/// constant.
-impl CondvarCheck for imp::Mutex {
-    type Check = NoCheck;
-}
-
-pub struct NoCheck;
-
-#[allow(dead_code)]
-impl NoCheck {
-    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
-    pub const fn new() -> Self {
-        Self
-    }
-    pub fn verify(&self, _: &MovableMutex) {}
-}
diff --git a/library/std/src/sys_common/mod.rs b/library/std/src/sys_common/mod.rs
index 8c19f9332..b1987aa0f 100644
--- a/library/std/src/sys_common/mod.rs
+++ b/library/std/src/sys_common/mod.rs
@@ -21,20 +21,18 @@
 mod tests;
 
 pub mod backtrace;
-pub mod condvar;
 pub mod fs;
 pub mod io;
 pub mod lazy_box;
 pub mod memchr;
-pub mod mutex;
 pub mod once;
 pub mod process;
 pub mod remutex;
-pub mod rwlock;
 pub mod thread;
 pub mod thread_info;
 pub mod thread_local_dtor;
 pub mod thread_parker;
+pub mod wstr;
 pub mod wtf8;
 
 cfg_if::cfg_if! {
diff --git a/library/std/src/sys_common/mutex.rs b/library/std/src/sys_common/mutex.rs
deleted file mode 100644
index 98046f20f..000000000
--- a/library/std/src/sys_common/mutex.rs
+++ /dev/null
@@ -1,50 +0,0 @@
-use crate::sys::locks as imp;
-
-/// An OS-based mutual exclusion lock.
-///
-/// This mutex cleans up its resources in its `Drop` implementation, may safely
-/// be moved (when not borrowed), and does not cause UB when used reentrantly.
-///
-/// This mutex does not implement poisoning.
-///
-/// This is either a wrapper around `LazyBox<imp::Mutex>` or `imp::Mutex`,
-/// depending on the platform. It is boxed on platforms where `imp::Mutex` may
-/// not be moved.
-pub struct MovableMutex(imp::MovableMutex);
-
-unsafe impl Sync for MovableMutex {}
-
-impl MovableMutex {
-    /// Creates a new mutex.
-    #[inline]
-    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
-    pub const fn new() -> Self {
-        Self(imp::MovableMutex::new())
-    }
-
-    pub(super) fn raw(&self) -> &imp::Mutex {
-        &self.0
-    }
-
-    /// Locks the mutex blocking the current thread until it is available.
-    #[inline]
-    pub fn raw_lock(&self) {
-        unsafe { self.0.lock() }
-    }
-
-    /// Attempts to lock the mutex without blocking, returning whether it was
-    /// successfully acquired or not.
-    #[inline]
-    pub fn try_lock(&self) -> bool {
-        unsafe { self.0.try_lock() }
-    }
-
-    /// Unlocks the mutex.
-    ///
-    /// Behavior is undefined if the current thread does not actually hold the
-    /// mutex.
-    #[inline]
-    pub unsafe fn raw_unlock(&self) {
-        self.0.unlock()
-    }
-}
diff --git a/library/std/src/sys_common/once/generic.rs b/library/std/src/sys_common/once/generic.rs
index acf5f2471..d953a6745 100644
--- a/library/std/src/sys_common/once/generic.rs
+++ b/library/std/src/sys_common/once/generic.rs
@@ -107,6 +107,7 @@ struct WaiterQueue<'a> {
 
 impl Once {
     #[inline]
+    #[rustc_const_stable(feature = "const_once_new", since = "1.32.0")]
     pub const fn new() -> Once {
         Once { state_and_queue: AtomicPtr::new(ptr::invalid_mut(INCOMPLETE)) }
     }
diff --git a/library/std/src/sys_common/remutex.rs b/library/std/src/sys_common/remutex.rs
index b448ae3a9..4c054da64 100644
--- a/library/std/src/sys_common/remutex.rs
+++ b/library/std/src/sys_common/remutex.rs
@@ -1,11 +1,11 @@
 #[cfg(all(test, not(target_os = "emscripten")))]
 mod tests;
 
-use super::mutex as sys;
 use crate::cell::UnsafeCell;
 use crate::ops::Deref;
 use crate::panic::{RefUnwindSafe, UnwindSafe};
 use crate::sync::atomic::{AtomicUsize, Ordering::Relaxed};
+use crate::sys::locks as sys;
 
 /// A re-entrant mutual exclusion
 ///
@@ -39,7 +39,7 @@ use crate::sync::atomic::{AtomicUsize, Ordering::Relaxed};
 /// synchronization is left to the mutex, making relaxed memory ordering for
 /// the `owner` field fine in all cases.
 pub struct ReentrantMutex<T> {
-    mutex: sys::MovableMutex,
+    mutex: sys::Mutex,
     owner: AtomicUsize,
     lock_count: UnsafeCell<u32>,
     data: T,
@@ -74,7 +74,7 @@ impl<T> ReentrantMutex<T> {
     /// Creates a new reentrant mutex in an unlocked state.
     pub const fn new(t: T) -> ReentrantMutex<T> {
         ReentrantMutex {
-            mutex: sys::MovableMutex::new(),
+            mutex: sys::Mutex::new(),
             owner: AtomicUsize::new(0),
             lock_count: UnsafeCell::new(0),
             data: t,
@@ -100,7 +100,7 @@ impl<T> ReentrantMutex<T> {
             if self.owner.load(Relaxed) == this_thread {
                 self.increment_lock_count();
             } else {
-                self.mutex.raw_lock();
+                self.mutex.lock();
                 self.owner.store(this_thread, Relaxed);
                 debug_assert_eq!(*self.lock_count.get(), 0);
                 *self.lock_count.get() = 1;
@@ -162,7 +162,7 @@ impl<T> Drop for ReentrantMutexGuard<'_, T> {
             *self.lock.lock_count.get() -= 1;
             if *self.lock.lock_count.get() == 0 {
                 self.lock.owner.store(0, Relaxed);
-                self.lock.mutex.raw_unlock();
+                self.lock.mutex.unlock();
             }
         }
     }
diff --git a/library/std/src/sys_common/rwlock.rs b/library/std/src/sys_common/rwlock.rs
deleted file mode 100644
index 042981dac..000000000
--- a/library/std/src/sys_common/rwlock.rs
+++ /dev/null
@@ -1,71 +0,0 @@
-use crate::sys::locks as imp;
-
-/// An OS-based reader-writer lock.
-///
-/// This rwlock cleans up its resources in its `Drop` implementation and may
-/// safely be moved (when not borrowed).
-///
-/// This rwlock does not implement poisoning.
-///
-/// This is either a wrapper around `LazyBox<imp::RwLock>` or `imp::RwLock`,
-/// depending on the platform. It is boxed on platforms where `imp::RwLock` may
-/// not be moved.
-pub struct MovableRwLock(imp::MovableRwLock);
-
-impl MovableRwLock {
-    /// Creates a new reader-writer lock for use.
-    #[inline]
-    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
-    pub const fn new() -> Self {
-        Self(imp::MovableRwLock::new())
-    }
-
-    /// Acquires shared access to the underlying lock, blocking the current
-    /// thread to do so.
-    #[inline]
-    pub fn read(&self) {
-        unsafe { self.0.read() }
-    }
-
-    /// Attempts to acquire shared access to this lock, returning whether it
-    /// succeeded or not.
-    ///
-    /// This function does not block the current thread.
-    #[inline]
-    pub fn try_read(&self) -> bool {
-        unsafe { self.0.try_read() }
-    }
-
-    /// Acquires write access to the underlying lock, blocking the current thread
-    /// to do so.
-    #[inline]
-    pub fn write(&self) {
-        unsafe { self.0.write() }
-    }
-
-    /// Attempts to acquire exclusive access to this lock, returning whether it
-    /// succeeded or not.
-    ///
-    /// This function does not block the current thread.
-    #[inline]
-    pub fn try_write(&self) -> bool {
-        unsafe { self.0.try_write() }
-    }
-
-    /// Unlocks previously acquired shared access to this lock.
-    ///
-    /// Behavior is undefined if the current thread does not have shared access.
-    #[inline]
-    pub unsafe fn read_unlock(&self) {
-        self.0.read_unlock()
-    }
-
-    /// Unlocks previously acquired exclusive access to this lock.
-    ///
-    /// Behavior is undefined if the current thread does not currently have
-    /// exclusive access.
-    #[inline]
-    pub unsafe fn write_unlock(&self) {
-        self.0.write_unlock()
-    }
-}
diff --git a/library/std/src/sys_common/wstr.rs b/library/std/src/sys_common/wstr.rs
new file mode 100644
index 000000000..b230fd1a8
--- /dev/null
+++ b/library/std/src/sys_common/wstr.rs
@@ -0,0 +1,59 @@
+//! This module contains constructs to work with 16-bit characters (UCS-2 or UTF-16)
+#![allow(dead_code)]
+
+use crate::marker::PhantomData;
+use crate::num::NonZeroU16;
+use crate::ptr::NonNull;
+
+/// A safe iterator over a LPWSTR
+/// (aka a pointer to a series of UTF-16 code units terminated by a NULL).
+pub struct WStrUnits<'a> {
+    // The pointer must never be null...
+    lpwstr: NonNull<u16>,
+    // ...and the memory it points to must be valid for this lifetime.
+    lifetime: PhantomData<&'a [u16]>,
+}
+
+impl WStrUnits<'_> {
+    /// Create the iterator. Returns `None` if `lpwstr` is null.
+    ///
+    /// SAFETY: `lpwstr` must point to a null-terminated wide string that lives
+    /// at least as long as the lifetime of this struct.
+    pub unsafe fn new(lpwstr: *const u16) -> Option<Self> {
+        Some(Self { lpwstr: NonNull::new(lpwstr as _)?, lifetime: PhantomData })
+    }
+
+    pub fn peek(&self) -> Option<NonZeroU16> {
+        // SAFETY: It's always safe to read the current item because we don't
+        // ever move out of the array's bounds.
+        unsafe { NonZeroU16::new(*self.lpwstr.as_ptr()) }
+    }
+
+    /// Advance the iterator while `predicate` returns true.
+    /// Returns the number of items it advanced by.
+    pub fn advance_while<P: FnMut(NonZeroU16) -> bool>(&mut self, mut predicate: P) -> usize {
+        let mut counter = 0;
+        while let Some(w) = self.peek() {
+            if !predicate(w) {
+                break;
+            }
+            counter += 1;
+            self.next();
+        }
+        counter
+    }
+}
+
+impl Iterator for WStrUnits<'_> {
+    // This can never return zero as that marks the end of the string.
+    type Item = NonZeroU16;
+    fn next(&mut self) -> Option<NonZeroU16> {
+        // SAFETY: If NULL is reached we immediately return.
+        // Therefore it's safe to advance the pointer after that.
+        unsafe {
+            let next = self.peek()?;
+            self.lpwstr = NonNull::new_unchecked(self.lpwstr.as_ptr().add(1));
+            Some(next)
+        }
+    }
+}