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Auto merge of #31440 - reem:rwlock-map-fix, r=alexcrichton

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Also update the instability reason to include a note about a possible
bad interaction with condition variables on systems that allow
waiting on a RwLock guard.
This commit is contained in:
bors 2016-02-07 00:16:58 +00:00
commit 3623797ebb
1 changed files with 6 additions and 4 deletions
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10
src/libstd/sync/rwlock.rs
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@ -454,10 +454,11 @@ impl<'rwlock, T: ?Sized> RwLockReadGuard<'rwlock, T> {
/// assert_eq!(*y, 1); /// assert_eq!(*y, 1);
/// ``` /// ```
#[unstable(feature = "guard_map", #[unstable(feature = "guard_map",
reason = "recently added, needs RFC for stabilization", reason = "recently added, needs RFC for stabilization,
questionable interaction with Condvar",
issue = "27746")] issue = "27746")]
pub fn map<U: ?Sized, F>(this: Self, cb: F) -> RwLockReadGuard<'rwlock, U> pub fn map<U: ?Sized, F>(this: Self, cb: F) -> RwLockReadGuard<'rwlock, U>
where F: FnOnce(&'rwlock T) -> &'rwlock U where F: FnOnce(&T) -> &U
{ {
let new = RwLockReadGuard { let new = RwLockReadGuard {
__lock: this.__lock, __lock: this.__lock,
@ -504,10 +505,11 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
/// assert_eq!(&**x.read().unwrap(), &[10, 2]); /// assert_eq!(&**x.read().unwrap(), &[10, 2]);
/// ``` /// ```
#[unstable(feature = "guard_map", #[unstable(feature = "guard_map",
reason = "recently added, needs RFC for stabilization", reason = "recently added, needs RFC for stabilization,
questionable interaction with Condvar",
issue = "27746")] issue = "27746")]
pub fn map<U: ?Sized, F>(this: Self, cb: F) -> RwLockWriteGuard<'rwlock, U> pub fn map<U: ?Sized, F>(this: Self, cb: F) -> RwLockWriteGuard<'rwlock, U>
where F: FnOnce(&'rwlock mut T) -> &'rwlock mut U where F: FnOnce(&mut T) -> &mut U
{ {
// Compute the new data while still owning the original lock // Compute the new data while still owning the original lock
// in order to correctly poison if the callback panics. // in order to correctly poison if the callback panics.