Fix memory leak of DynValue

Author: mulimoen

hdf5-types/src/dyn_value.rs

@@ -702,7 +702,7 @@ impl Display for DynValue<'_> {
 
 pub struct OwnedDynValue {
     tp: TypeDescriptor,
-    buf: Vec<u8>,
+    buf: Box<[u8]>,
 }
 
 impl OwnedDynValue {
@@ -711,7 +711,7 @@ impl OwnedDynValue {
         let len = mem::size_of_val(&value);
         let buf = unsafe { std::slice::from_raw_parts(ptr, len) };
         mem::forget(value);
-        Self { tp: T::type_descriptor(), buf: buf.to_owned() }
+        Self { tp: T::type_descriptor(), buf: buf.to_owned().into_boxed_slice() }
     }
 
     pub fn get(&self) -> DynValue {
@@ -728,9 +728,19 @@ impl OwnedDynValue {
     }
 
     #[doc(hidden)]
-    pub unsafe fn from_raw(tp: TypeDescriptor, buf: Vec<u8>) -> Self {
+    pub unsafe fn from_raw(tp: TypeDescriptor, buf: Box<[u8]>) -> Self {
         Self { tp, buf }
     }
+
+    #[doc(hidden)]
+    /// Use this if the values should still be used after the buffer has been
+    /// copied to the concrete type
+    pub fn drop_nonrecursive(mut self) {
+        // We can't take ownership of the contents of self,
+        // but we can replace the items with a zero-sized object
+        self.tp = <[u8; 0] as H5Type>::type_descriptor();
+        self.buf = Box::new([]);
+    }
 }
 
 impl<T: H5Type> From<T> for OwnedDynValue {

src/hl/plist/dataset_create.rs

@@ -723,11 +723,11 @@ impl DatasetCreate {
             FillValue::Default | FillValue::UserDefined => {
                 let dtype = Datatype::from_descriptor(tp)?;
                 let mut buf: Vec<u8> = Vec::with_capacity(tp.size());
+                h5try!(H5Pget_fill_value(self.id(), dtype.id(), buf.as_mut_ptr().cast()));
                 unsafe {
                     buf.set_len(tp.size());
                 }
-                h5try!(H5Pget_fill_value(self.id(), dtype.id(), buf.as_mut_ptr().cast()));
-                Ok(Some(unsafe { OwnedDynValue::from_raw(tp.clone(), buf) }))
+                Ok(Some(unsafe { OwnedDynValue::from_raw(tp.clone(), buf.into_boxed_slice()) }))
             }
             _ => Ok(None),
         }
@@ -741,11 +741,13 @@ impl DatasetCreate {
     pub fn get_fill_value_as<T: H5Type>(&self) -> Result<Option<T>> {
         let dtype = Datatype::from_type::<T>()?;
         Ok(self.get_fill_value(&dtype.to_descriptor()?)?.map(|value| unsafe {
-            let mut out: T = mem::zeroed();
+            let mut out: mem::MaybeUninit<T> = mem::MaybeUninit::uninit();
             let buf = value.get_buf();
-            ptr::copy_nonoverlapping(buf.as_ptr(), (&mut out as *mut T).cast(), buf.len());
-            mem::forget(value);
-            out
+            ptr::copy_nonoverlapping(buf.as_ptr(), out.as_mut_ptr().cast(), buf.len());
+            // Drop the Box<[u8]>, but not subfields
+            value.drop_nonrecursive();
+            // We now have exclusive access to all subfields
+            out.assume_init()
         }))
     }