From 317f494c72aead3fecd73788569983fd2f8ea8a3 Mon Sep 17 00:00:00 2001
From: Murarth <murarth@gmail.com>
Date: Wed, 7 Nov 2018 10:59:25 -0700
Subject: Fix Rc/Arc allocation layout

* Rounds allocation layout up to a multiple of alignment
* Adds a convenience method `Layout::pad_to_align` to perform rounding
---
 src/liballoc/rc.rs   | 6 ++++--
 src/liballoc/sync.rs | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

(limited to 'src/liballoc')

diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 45f035ad04f..bb52d7990ff 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -672,14 +672,16 @@ impl<T: ?Sized> Rc<T> {
         // Previously, layout was calculated on the expression
         // `&*(ptr as *const RcBox<T>)`, but this created a misaligned
         // reference (see #54908).
-        let (layout, _) = Layout::new::<RcBox<()>>()
-            .extend(Layout::for_value(&*ptr)).unwrap();
+        let layout = Layout::new::<RcBox<()>>()
+            .extend(Layout::for_value(&*ptr)).unwrap().0
+            .pad_to_align().unwrap();
 
         let mem = Global.alloc(layout)
             .unwrap_or_else(|_| handle_alloc_error(layout));
 
         // Initialize the RcBox
         let inner = set_data_ptr(ptr as *mut T, mem.as_ptr() as *mut u8) as *mut RcBox<T>;
+        debug_assert_eq!(Layout::for_value(&*inner), layout);
 
         ptr::write(&mut (*inner).strong, Cell::new(1));
         ptr::write(&mut (*inner).weak, Cell::new(1));
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index 2c396b3b06b..b63b3684964 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -575,14 +575,16 @@ impl<T: ?Sized> Arc<T> {
         // Previously, layout was calculated on the expression
         // `&*(ptr as *const ArcInner<T>)`, but this created a misaligned
         // reference (see #54908).
-        let (layout, _) = Layout::new::<ArcInner<()>>()
-            .extend(Layout::for_value(&*ptr)).unwrap();
+        let layout = Layout::new::<ArcInner<()>>()
+            .extend(Layout::for_value(&*ptr)).unwrap().0
+            .pad_to_align().unwrap();
 
         let mem = Global.alloc(layout)
             .unwrap_or_else(|_| handle_alloc_error(layout));
 
         // Initialize the ArcInner
         let inner = set_data_ptr(ptr as *mut T, mem.as_ptr() as *mut u8) as *mut ArcInner<T>;
+        debug_assert_eq!(Layout::for_value(&*inner), layout);
 
         ptr::write(&mut (*inner).strong, atomic::AtomicUsize::new(1));
         ptr::write(&mut (*inner).weak, atomic::AtomicUsize::new(1));
-- 
cgit 1.4.1-3-g733a5