Merge pull request #235 from japaric/well-aligned-dangling-pointer

CAS Pool: make dangling Ptr well aligned

Author: korken89

src/pool/cas.rs

@@ -177,7 +177,8 @@ impl<T> Ptr<T> {
     }
 
     pub fn dangling() -> Self {
-        unsafe { Self::from_parts(initial_tag_value(), 1) }
+        // `anchor()` returns a well-aligned pointer so an offset of 0 will also produce a well-aligned pointer
+        unsafe { Self::from_parts(initial_tag_value(), 0) }
     }
 
     pub unsafe fn as_ref(&self) -> &T {

src/pool/singleton.rs

@@ -354,6 +354,25 @@ mod tests {
         assert_eq!(*A::alloc().unwrap().init(1), 1);
     }
 
+    #[test]
+    fn boxed_zst_is_well_aligned() {
+        #[repr(align(2))]
+        pub struct Zst2;
+
+        pool!(A: Zst2);
+
+        let x = A::alloc().unwrap().init(Zst2);
+        assert_eq!(0, &*x as *const Zst2 as usize % 2);
+
+        #[repr(align(4096))]
+        pub struct Zst4096;
+
+        pool!(B: Zst4096);
+
+        let x = B::alloc().unwrap().init(Zst4096);
+        assert_eq!(0, &*x as *const Zst4096 as usize % 4096);
+    }
+
     #[test]
     fn destructors() {
         static COUNT: AtomicUsize = AtomicUsize::new(0);