auto merge of #12235 : huonw/rust/raii-lock, r=alexcrichton

- adds a `LockGuard` type returned by `.lock` and `.trylock` that unlocks the mutex in the destructor
- renames `mutex::Mutex` to `StaticNativeMutex` 
- adds a `NativeMutex` type with a destructor
- removes `LittleLock`
- adds `#[must_use]` to `sync::mutex::Guard` to remind people to use it

1 files changed, 6 insertions, 13 deletions

diff --git a/src/libstd/rt/args.rs b/src/libstd/rt/args.rs
index c417ea375fd..6f73265978b 100644
--- a/src/libstd/rt/args.rs
+++ b/src/libstd/rt/args.rs
@@ -68,12 +68,11 @@ mod imp {
     use option::{Option, Some, None};
     use ptr::RawPtr;
     use iter::Iterator;
-    use unstable::finally::Finally;
-    use unstable::mutex::{Mutex, MUTEX_INIT};
+    use unstable::mutex::{StaticNativeMutex, NATIVE_MUTEX_INIT};
     use mem;
 
     static mut global_args_ptr: uint = 0;
-    static mut lock: Mutex = MUTEX_INIT;
+    static mut lock: StaticNativeMutex = NATIVE_MUTEX_INIT;
 
     #[cfg(not(test))]
     pub unsafe fn init(argc: int, argv: **u8) {
@@ -111,16 +110,10 @@ mod imp {
     }
 
     fn with_lock<T>(f: || -> T) -> T {
-        (|| {
-            unsafe {
-                lock.lock();
-                f()
-            }
-        }).finally(|| {
-            unsafe {
-                lock.unlock();
-            }
-        })
+        unsafe {
+            let _guard = lock.lock();
+            f()
+        }
     }
 
     fn get_global_ptr() -> *mut Option<~~[~[u8]]> {