More correct buffer allocation

The current one does not cause real problems at this time because the
size allocated is large enough, but it's better to use the more correct
one.

crossbeam-deque/src/deque.rs

@@ -2,8 +2,9 @@ use std::cell::{Cell, UnsafeCell};
 use std::cmp;
 use std::fmt;
 use std::marker::PhantomData;
-use std::mem::{self, ManuallyDrop, MaybeUninit};
+use std::mem::{self, MaybeUninit};
 use std::ptr;
+use std::slice;
 use std::sync::atomic::{self, AtomicIsize, AtomicPtr, AtomicUsize, Ordering};
 use std::sync::Arc;
 
@@ -37,15 +38,22 @@ impl<T> Buffer<T> {
     fn alloc(cap: usize) -> Buffer<T> {
         debug_assert_eq!(cap, cap.next_power_of_two());
 
-        let mut v = ManuallyDrop::new(Vec::with_capacity(cap));
-        let ptr = v.as_mut_ptr();
+        let ptr = Box::into_raw(
+            (0..cap)
+                .map(|_| MaybeUninit::<T>::uninit())
+                .collect::<Box<[_]>>(),
+        )
+        .cast::<T>();
 
         Buffer { ptr, cap }
     }
 
     /// Deallocates the buffer.
     unsafe fn dealloc(self) {
-        drop(Vec::from_raw_parts(self.ptr, 0, self.cap));
+        drop(Box::from_raw(slice::from_raw_parts_mut(
+            self.ptr.cast::<MaybeUninit<T>>(),
+            self.cap,
+        )));
     }
 
     /// Returns a pointer to the task at the specified `index`.

crossbeam-epoch/src/collector.rs

@@ -403,9 +403,10 @@ mod tests {
             }
 
             let len = v.len();
-            let ptr = ManuallyDrop::new(v).as_mut_ptr() as usize;
+            let cap = v.capacity();
+            let ptr = ManuallyDrop::new(v).as_mut_ptr();
             guard.defer_unchecked(move || {
-                drop(Vec::from_raw_parts(ptr as *const i32 as *mut i32, len, len));
+                drop(Vec::from_raw_parts(ptr, len, cap));
                 DESTROYS.fetch_add(len, Ordering::Relaxed);
             });
             guard.flush();