message: avoid importing C functions in alloc_write_race test
diff: // ignore-windows: Concurrency on Windows is not supported yet.
  +#![feature(new_uninit)]
  use std::thread::spawn;
  use std::ptr::null_mut;
  @@ -10,11 +11,6 @@ struct EvilSend<T>(pub T);
  unsafe impl<T> Send for EvilSend<T> {}
  unsafe impl<T> Sync for EvilSend<T> {}
  -extern "C" {
  - fn malloc(size: usize) -> *mut u8;
  - fn free(ptr: *mut u8);
  -}
  -
  pub fn main() {
  // Shared atomic pointer
  let pointer = AtomicPtr::new(null_mut::<usize>());
  @@ -33,7 +29,7 @@ pub fn main() {
  // Uses relaxed semantics to not generate
  // a release sequence.
  let pointer = &*ptr.0;
  - pointer.store(malloc(std::mem::size_of::<usize>()) as *mut usize, Ordering::Relaxed);
  + pointer.store(Box::into_raw(Box::<usize>::new_uninit()) as *mut usize, Ordering::Relaxed);
  });
  let j2 = spawn(move || {
  @@ -45,6 +41,6 @@ pub fn main() {
  j2.join().unwrap();
  // Clean up memory, will never be executed
  - free(pointer.load(Ordering::Relaxed) as *mut _);
  + drop(Box::from_raw(pointer.load(Ordering::Relaxed)));
  }
  }
  