rpc: added `#[repr(C)]` for structs.

src/runtime/src/rpc.rs

@@ -73,6 +73,7 @@ async unsafe fn recv_value<F>(stream: &TcpStream, tag: Tag<'async_recursion>, da
             Ok(())
         }
         Tag::List(it) | Tag::Array(it) => {
+            #[repr(C)]
             struct List { elements: *mut (), length: u32 };
             consume_value!(List, |ptr| {
                 (*ptr).length = proto_async::read_i32(stream).await? as u32;
@@ -174,6 +175,7 @@ unsafe fn send_value<W>(writer: &mut W, tag: Tag, data: &mut *const ())
             Ok(())
         }
         Tag::Keyword(it) => {
+            #[repr(C)]
             struct Keyword<'a> { name: CSlice<'a, u8> };
             consume_value!(Keyword, |ptr| {
                 writer.write_string(str::from_utf8((*ptr).name.as_ref()).unwrap())?;
@@ -185,6 +187,7 @@ unsafe fn send_value<W>(writer: &mut W, tag: Tag, data: &mut *const ())
             // to accurately advance data.
         }
         Tag::Object => {
+            #[repr(C)]
             struct Object { id: u32 };
             consume_value!(*const Object, |ptr|
                 writer.write_u32((**ptr).id))