Small changes.

tests/compile-fail/sync/libc_pthread_rwlock_read_wrong_owner.rs

@@ -0,0 +1,32 @@
+// ignore-windows: No libc on Windows
+
+#![feature(rustc_private)]
+
+extern crate libc;
+
+use std::cell::UnsafeCell;
+use std::sync::Arc;
+use std::thread;
+
+struct RwLock(UnsafeCell<libc::pthread_rwlock_t>);
+
+unsafe impl Send for RwLock {}
+unsafe impl Sync for RwLock {}
+
+fn new_lock() -> Arc<RwLock> {
+    Arc::new(RwLock(UnsafeCell::new(libc::PTHREAD_RWLOCK_INITIALIZER)))
+}
+
+fn main() {
+    unsafe {
+        let lock = new_lock();
+        assert_eq!(libc::pthread_rwlock_rdlock(lock.0.get() as *mut _), 0);
+
+        let lock_copy = lock.clone();
+        thread::spawn(move || {
+            assert_eq!(libc::pthread_rwlock_unlock(lock_copy.0.get() as *mut _), 0); //~ ERROR: Undefined Behavior: unlocked an rwlock that was not locked by the active thread
+        })
+        .join()
+        .unwrap();
+    }
+}

tests/compile-fail/sync/libc_pthread_rwlock_write_wrong_owner.rs

@@ -0,0 +1,32 @@
+// ignore-windows: No libc on Windows
+
+#![feature(rustc_private)]
+
+extern crate libc;
+
+use std::cell::UnsafeCell;
+use std::sync::Arc;
+use std::thread;
+
+struct RwLock(UnsafeCell<libc::pthread_rwlock_t>);
+
+unsafe impl Send for RwLock {}
+unsafe impl Sync for RwLock {}
+
+fn new_lock() -> Arc<RwLock> {
+    Arc::new(RwLock(UnsafeCell::new(libc::PTHREAD_RWLOCK_INITIALIZER)))
+}
+
+fn main() {
+    unsafe {
+        let lock = new_lock();
+        assert_eq!(libc::pthread_rwlock_wrlock(lock.0.get() as *mut _), 0);
+
+        let lock_copy = lock.clone();
+        thread::spawn(move || {
+            assert_eq!(libc::pthread_rwlock_unlock(lock_copy.0.get() as *mut _), 0); //~ ERROR: Undefined Behavior: unlocked an rwlock that was not locked by the active thread
+        })
+        .join()
+        .unwrap();
+    }
+}