diff --git a/src/kernel/synch.rs b/src/kernel/synch.rs
index 5a9eb93..b3a52f0 100644
--- a/src/kernel/synch.rs
+++ b/src/kernel/synch.rs
@@ -1,4 +1,5 @@
 use crate::utility::list::List;
+use crate::utility::objaddr::*;
 use crate::kernel::thread::Thread;
 use crate::simulator::interrupt::InterruptStatus::InterruptOff;
 use crate::simulator::machine::Machine;
@@ -16,6 +17,8 @@ pub struct Semaphore {
 
 }
 
+impl SynchObj for Semaphore {}
+
 impl Semaphore {
 
     ///     Initializes a semaphore, so that it can be used for synchronization.
@@ -89,6 +92,8 @@ pub struct Lock{
 
 }
 
+impl SynchObj for Lock {}
+
 impl Lock {
 
     ///    Initialize a Lock, so that it can be used for synchronization.
@@ -193,6 +198,8 @@ pub struct Condition{
     
 }
 
+impl SynchObj for Condition {}
+
 impl Condition {
 
     /// Initializes a Condition, so that it can be used for synchronization.
diff --git a/src/utility/objaddr.rs b/src/utility/objaddr.rs
index d876056..c402f5d 100644
--- a/src/utility/objaddr.rs
+++ b/src/utility/objaddr.rs
@@ -15,7 +15,7 @@ pub trait SynchObj { }
 /// A method allows to detect of an object corresponding to a given
 /// identifier exists; this is used to check the parameters of system
 /// calls.
-struct ObjAddr<'a> {
+pub struct ObjAddr<'a> {
     last_id: i32,
     map: HashMap<i32, &'a dyn SynchObj>
 }