msg_socket: make usize fixed size

Seems like an accidental ommission.  All other numeric types are
fixed-size, and usize is serialized as a u64 anyway.

1 files changed, 2 insertions, 2 deletions

diff --git a/msg_socket/src/msg_on_socket.rs b/msg_socket/src/msg_on_socket.rs
index 3dc59c0..ddf8622 100644
--- a/msg_socket/src/msg_on_socket.rs
+++ b/msg_socket/src/msg_on_socket.rs
@@ -347,8 +347,8 @@ rawfd_impl!(SharedMemory);
 
 // usize could be different sizes on different targets. We always use u64.
 impl MsgOnSocket for usize {
-    fn msg_size(&self) -> usize {
-        size_of::<u64>()
+    fn fixed_size() -> Option<usize> {
+        Some(size_of::<u64>())
     }
     unsafe fn read_from_buffer(buffer: &[u8], _fds: &[RawFd]) -> MsgResult<(Self, usize)> {
         if buffer.len() < size_of::<u64>() {