Auto merge of #97791 - m-ou-se:const-locks, r=m-ou-se

Make {Mutex, Condvar, RwLock}::new() const.

This makes it possible to have `static M: Mutex<_> = Mutex::new(..);` 🎉

Our implementations [on Linux](https://github.com/rust-lang/rust/pull/95035), [on Windows](https://github.com/rust-lang/rust/pull/77380), and various BSDs and some tier 3 platforms have already been using a non-allocating const-constructible implementation. As of https://github.com/rust-lang/rust/pull/97647, the remaining platforms (most notably macOS) now have a const-constructible implementation as well. This means we can finally make these functions publicly const.

Tracking issue: https://github.com/rust-lang/rust/issues/93740

15 files changed, 26 insertions, 6 deletions

diff --git a/library/std/src/sync/condvar.rs b/library/std/src/sync/condvar.rs
index 7ff2f330f8a..eb1e7135a6e 100644
--- a/library/std/src/sync/condvar.rs
+++ b/library/std/src/sync/condvar.rs
@@ -122,8 +122,10 @@ impl Condvar {
     /// let condvar = Condvar::new();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
     #[must_use]
-    pub fn new() -> Condvar {
+    #[inline]
+    pub const fn new() -> Condvar {
         Condvar { inner: sys::Condvar::new() }
     }
 
diff --git a/library/std/src/sync/mutex.rs b/library/std/src/sync/mutex.rs
index 31342a89054..e0d13cd648c 100644
--- a/library/std/src/sync/mutex.rs
+++ b/library/std/src/sync/mutex.rs
@@ -213,7 +213,9 @@ impl<T> Mutex<T> {
     /// let mutex = Mutex::new(0);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn new(t: T) -> Mutex<T> {
+    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
+    #[inline]
+    pub const fn new(t: T) -> Mutex<T> {
         Mutex {
             inner: sys::MovableMutex::new(),
             poison: poison::Flag::new(),
diff --git a/library/std/src/sync/poison.rs b/library/std/src/sync/poison.rs
index 9c918be3387..741312d5537 100644
--- a/library/std/src/sync/poison.rs
+++ b/library/std/src/sync/poison.rs
@@ -19,6 +19,7 @@ pub struct Flag {
 // all cases.
 
 impl Flag {
+    #[inline]
     pub const fn new() -> Flag {
         Flag { failed: AtomicBool::new(false) }
     }
diff --git a/library/std/src/sync/rwlock.rs b/library/std/src/sync/rwlock.rs
index 9517e7e1f03..1192c08cb1a 100644
--- a/library/std/src/sync/rwlock.rs
+++ b/library/std/src/sync/rwlock.rs
@@ -146,7 +146,9 @@ impl<T> RwLock<T> {
     /// let lock = RwLock::new(5);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn new(t: T) -> RwLock<T> {
+    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
+    #[inline]
+    pub const fn new(t: T) -> RwLock<T> {
         RwLock {
             inner: sys::MovableRwLock::new(),
             poison: poison::Flag::new(),
diff --git a/library/std/src/sys/itron/mutex.rs b/library/std/src/sys/itron/mutex.rs
index 2ba8454ff92..715e94c3b3d 100644
--- a/library/std/src/sys/itron/mutex.rs
+++ b/library/std/src/sys/itron/mutex.rs
@@ -26,6 +26,7 @@ fn new_mtx() -> Result<abi::ID, ItronError> {
 }
 
 impl Mutex {
+    #[inline]
     pub const fn new() -> Mutex {
         Mutex { mtx: SpinIdOnceCell::new() }
     }
diff --git a/library/std/src/sys/solid/rwlock.rs b/library/std/src/sys/solid/rwlock.rs
index 433abc895f5..0a770cf03f2 100644
--- a/library/std/src/sys/solid/rwlock.rs
+++ b/library/std/src/sys/solid/rwlock.rs
@@ -23,6 +23,7 @@ fn new_rwl() -> Result<abi::ID, ItronError> {
 }
 
 impl RwLock {
+    #[inline]
     pub const fn new() -> RwLock {
         RwLock { rwl: SpinIdOnceCell::new() }
     }
diff --git a/library/std/src/sys/unsupported/locks/condvar.rs b/library/std/src/sys/unsupported/locks/condvar.rs
index f27bf2b26bd..e703fd0d269 100644
--- a/library/std/src/sys/unsupported/locks/condvar.rs
+++ b/library/std/src/sys/unsupported/locks/condvar.rs
@@ -6,6 +6,7 @@ pub struct Condvar {}
 pub type MovableCondvar = Condvar;
 
 impl Condvar {
+    #[inline]
     pub const fn new() -> Condvar {
         Condvar {}
     }
diff --git a/library/std/src/sys/unsupported/locks/mutex.rs b/library/std/src/sys/unsupported/locks/mutex.rs
index 56bad71b189..d7cb12e0cf9 100644
--- a/library/std/src/sys/unsupported/locks/mutex.rs
+++ b/library/std/src/sys/unsupported/locks/mutex.rs
@@ -11,6 +11,7 @@ unsafe impl Send for Mutex {}
 unsafe impl Sync for Mutex {} // no threads on this platform
 
 impl Mutex {
+    #[inline]
     pub const fn new() -> Mutex {
         Mutex { locked: Cell::new(false) }
     }
diff --git a/library/std/src/sys/unsupported/locks/rwlock.rs b/library/std/src/sys/unsupported/locks/rwlock.rs
index bf6e2d3d080..aca5fb7152c 100644
--- a/library/std/src/sys/unsupported/locks/rwlock.rs
+++ b/library/std/src/sys/unsupported/locks/rwlock.rs
@@ -11,6 +11,7 @@ unsafe impl Send for RwLock {}
 unsafe impl Sync for RwLock {} // no threads on this platform
 
 impl RwLock {
+    #[inline]
     pub const fn new() -> RwLock {
         RwLock { mode: Cell::new(0) }
     }
diff --git a/library/std/src/sys/windows/locks/condvar.rs b/library/std/src/sys/windows/locks/condvar.rs
index 59e2c1be0f0..be9a2abbe35 100644
--- a/library/std/src/sys/windows/locks/condvar.rs
+++ b/library/std/src/sys/windows/locks/condvar.rs
@@ -14,6 +14,7 @@ unsafe impl Send for Condvar {}
 unsafe impl Sync for Condvar {}
 
 impl Condvar {
+    #[inline]
     pub const fn new() -> Condvar {
         Condvar { inner: UnsafeCell::new(c::CONDITION_VARIABLE_INIT) }
     }
diff --git a/library/std/src/sys/windows/locks/mutex.rs b/library/std/src/sys/windows/locks/mutex.rs
index 08f55844a0e..f91e8f9f59a 100644
--- a/library/std/src/sys/windows/locks/mutex.rs
+++ b/library/std/src/sys/windows/locks/mutex.rs
@@ -33,6 +33,7 @@ pub unsafe fn raw(m: &Mutex) -> c::PSRWLOCK {
 }
 
 impl Mutex {
+    #[inline]
     pub const fn new() -> Mutex {
         Mutex { srwlock: UnsafeCell::new(c::SRWLOCK_INIT) }
     }
diff --git a/library/std/src/sys/windows/locks/rwlock.rs b/library/std/src/sys/windows/locks/rwlock.rs
index a32df85e2f6..fa5ffe5749f 100644
--- a/library/std/src/sys/windows/locks/rwlock.rs
+++ b/library/std/src/sys/windows/locks/rwlock.rs
@@ -11,6 +11,7 @@ unsafe impl Send for RwLock {}
 unsafe impl Sync for RwLock {}
 
 impl RwLock {
+    #[inline]
     pub const fn new() -> RwLock {
         RwLock { inner: UnsafeCell::new(c::SRWLOCK_INIT) }
     }
diff --git a/library/std/src/sys_common/condvar.rs b/library/std/src/sys_common/condvar.rs
index 1def0518e0a..f3ac1061b89 100644
--- a/library/std/src/sys_common/condvar.rs
+++ b/library/std/src/sys_common/condvar.rs
@@ -14,7 +14,8 @@ pub struct Condvar {
 
 impl Condvar {
     /// Creates a new condition variable for use.
-    pub fn new() -> Self {
+    #[inline]
+    pub const fn new() -> Self {
         Self { inner: imp::MovableCondvar::new(), check: CondvarCheck::new() }
     }
 
diff --git a/library/std/src/sys_common/mutex.rs b/library/std/src/sys_common/mutex.rs
index 36ea888d8de..81eefa1133f 100644
--- a/library/std/src/sys_common/mutex.rs
+++ b/library/std/src/sys_common/mutex.rs
@@ -15,6 +15,7 @@ unsafe impl Sync for StaticMutex {}
 
 impl StaticMutex {
     /// Creates a new mutex for use.
+    #[inline]
     pub const fn new() -> Self {
         Self(imp::Mutex::new())
     }
@@ -60,7 +61,8 @@ unsafe impl Sync for MovableMutex {}
 
 impl MovableMutex {
     /// Creates a new mutex.
-    pub fn new() -> Self {
+    #[inline]
+    pub const fn new() -> Self {
         Self(imp::MovableMutex::new())
     }
 
diff --git a/library/std/src/sys_common/rwlock.rs b/library/std/src/sys_common/rwlock.rs
index abc9fd561f1..265cebfdc3e 100644
--- a/library/std/src/sys_common/rwlock.rs
+++ b/library/std/src/sys_common/rwlock.rs
@@ -10,6 +10,7 @@ pub struct StaticRwLock(imp::RwLock);
 
 impl StaticRwLock {
     /// Creates a new rwlock for use.
+    #[inline]
     pub const fn new() -> Self {
         Self(imp::RwLock::new())
     }
@@ -73,7 +74,8 @@ pub struct MovableRwLock(imp::MovableRwLock);
 
 impl MovableRwLock {
     /// Creates a new reader-writer lock for use.
-    pub fn new() -> Self {
+    #[inline]
+    pub const fn new() -> Self {
         Self(imp::MovableRwLock::new())
     }