From 4577da75f4badd66a337eb15da76ca836ab1ad6e Mon Sep 17 00:00:00 2001
From: Mike Hommey <mh@glandium.org>
Date: Wed, 4 Apr 2018 19:30:46 +0900
Subject: [PATCH] Use box syntax instead of Box::new in Mutex::remutex on
 Windows

The Box::new(mem::uninitialized()) pattern actually actively copies
uninitialized bytes from the stack into the box, which is a waste of
time. Using the box syntax instead avoids the useless copy.
---
 src/libstd/sys/windows/mutex.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libstd/sys/windows/mutex.rs b/src/libstd/sys/windows/mutex.rs
index 85560368590..9bf9f749d4d 100644
--- a/src/libstd/sys/windows/mutex.rs
+++ b/src/libstd/sys/windows/mutex.rs
@@ -117,7 +117,7 @@ impl Mutex {
             0 => {}
             n => return n as *mut _,
         }
-        let mut re = Box::new(ReentrantMutex::uninitialized());
+        let mut re = box ReentrantMutex::uninitialized();
         re.init();
         let re = Box::into_raw(re);
         match self.lock.compare_and_swap(0, re as usize, Ordering::SeqCst) {