Fix memory leak on beef::lean::Cow

src/fat.rs

@@ -40,4 +40,30 @@ impl Capacity for Wide {
     fn maybe(_: usize, capacity: Option<NonZeroUsize>) -> Option<NonZeroUsize> {
         capacity
     }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Cow;
+
+    #[test]
+    fn stress_test_owned() {
+        let mut expected = String::from("Hello... ");
+        let mut cow: Cow<str> = Cow::borrowed("Hello... ");
+
+        for i in 0..1024 {
+            if i % 3 == 0 {
+                cow = cow.clone();
+            }
+
+            let mut owned = cow.into_owned();
+
+            expected.push_str("Hello?.. ");
+            owned.push_str("Hello?.. ");
+
+            cow = owned.into();
+        }
+
+        assert_eq!(expected, cow.into_owned());
+    }
 }

src/lean.rs

@@ -20,7 +20,7 @@ mod internal {
 use internal::Lean;
 
 const MASK_LO: usize = u32::max_value() as usize;
-const MASK_HI: usize = !u32::max_value() as usize;
+const MASK_HI: usize = !(u32::max_value() as usize);
 
 impl Capacity for Lean {
     type Field = Lean;
@@ -40,14 +40,14 @@ impl Capacity for Lean {
 
     #[inline]
     fn store<T>(ptr: *mut T, len: usize, capacity: usize) -> (*mut [T], Lean) {
-        if capacity > MASK_LO {
+        if capacity & MASK_HI != 0 {
             panic!("beef::lean::Cow: Capacity out of bounds");
         }
 
         (
             slice_from_raw_parts_mut(
                 ptr,
-                (len & MASK_LO) | ((capacity & MASK_HI) << 32),
+                (len & MASK_LO) | ((capacity & MASK_LO) << 32),
             ),
             Lean,
         )
@@ -79,7 +79,10 @@ mod tests {
 
         for i in 0..1024 {
             if i % 3 == 0 {
-                cow = cow.clone();
+                let mut old = std::mem::ManuallyDrop::new(cow);
+                cow = (*old).clone();
+
+                unsafe { std::mem::ManuallyDrop::drop(&mut old); }
             }
 
             let mut owned = cow.into_owned();

src/traits.rs

@@ -100,7 +100,7 @@ pub(crate) mod internal {
         where
             U: Capacity,
         {
-            let len = (*inner.as_ptr()).len();
+            let len = (&*inner.as_ptr()).len();
             let (len, cap) = U::unpack(len, capacity);
 
             String::from_utf8_unchecked(
@@ -154,7 +154,7 @@ pub(crate) mod internal {
         where
             U: Capacity,
         {
-            let len = (*inner.as_ptr()).len();
+            let len = (&*inner.as_ptr()).len();
             let (len, cap) = U::unpack(len, capacity);
 
             Vec::from_raw_parts(inner.cast().as_ptr(), len, cap)