Avoid flushing empty mmaps

Author: somethingelseentirely

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Changelog
 
 ## Unreleased
+- avoid flushing empty memory maps in `Section::freeze` to prevent macOS errors
 - derived zerocopy traits for `SectionHandle` to allow storing handles in `ByteArea` sections
 - added example demonstrating `ByteArea` with multiple typed sections, concurrent mutations, and freezing or persisting the area
 - added example combining Python bindings with winnow parsing

INVENTORY.md

@@ -5,6 +5,7 @@
 
 ## Desired Functionality
 - Add Kani proofs for winnow view helpers.
+- Add test covering freezing an empty section to guard against flush errors on macOS.
 
 ## Discovered Issues
 - None at the moment.

src/area.rs

@@ -176,7 +176,9 @@ where
 
     /// Freeze the section and return immutable [`Bytes`].
     pub fn freeze(self) -> io::Result<Bytes> {
-        self.mmap.flush()?;
+        if self.mmap.len() > 0 {
+            self.mmap.flush()?;
+        }
         let len_bytes = self.elems * core::mem::size_of::<T>();
         let offset = self.offset;
         // Convert the writable mapping into a read-only view instead of