Change loom tests to use cfg(loom) internally (#314)

src/bytes_mut.rs

@@ -1427,3 +1427,38 @@ unsafe fn shared_v_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize)
     let shared = (*data.get_mut()) as *mut Shared;
     release_shared(shared as *mut Shared);
 }
+
+// fuzz tests
+#[cfg(all(test, loom))]
+mod fuzz {
+    use std::sync::Arc;
+    use loom::thread;
+
+    use crate::Bytes;
+    use super::BytesMut;
+
+    #[test]
+    fn bytes_mut_cloning_frozen() {
+        loom::model(|| {
+            let a = BytesMut::from(&b"abcdefgh"[..]).split().freeze();
+            let addr = a.as_ptr() as usize;
+
+            // test the Bytes::clone is Sync by putting it in an Arc
+            let a1 = Arc::new(a);
+            let a2 = a1.clone();
+
+            let t1 = thread::spawn(move || {
+                let b: Bytes = (*a1).clone();
+                assert_eq!(b.as_ptr() as usize, addr);
+            });
+
+            let t2 = thread::spawn(move || {
+                let b: Bytes = (*a2).clone();
+                assert_eq!(b.as_ptr() as usize, addr);
+            });
+
+            t1.join().unwrap();
+            t2.join().unwrap();
+        });
+    }
+}