Make rcl_client_t have stable location

This prevents another client initializing at the same location.
Therefore preventing conflicts in a trace.

r2r/src/clients.rs

@@ -318,11 +318,10 @@ impl Client_ for UntypedClient_ {
     }
 }
 
-pub fn create_client_helper(
-    node: *mut rcl_node_t, service_name: &str, service_ts: *const rosidl_service_type_support_t,
-    qos_profile: QosProfile,
-) -> Result<rcl_client_t> {
-    let mut client_handle = unsafe { rcl_get_zero_initialized_client() };
+pub unsafe fn create_client_helper(
+    client_handle: &mut rcl_client_t, node: *mut rcl_node_t, service_name: &str,
+    service_ts: *const rosidl_service_type_support_t, qos_profile: QosProfile,
+) -> Result<()> {
     let service_name_c_string =
         CString::new(service_name).map_err(|_| Error::RCL_RET_INVALID_ARGUMENT)?;
 
@@ -330,15 +329,16 @@ pub fn create_client_helper(
         let mut client_options = rcl_client_get_default_options();
         client_options.qos = qos_profile.into();
         rcl_client_init(
-            &mut client_handle,
+            client_handle,
             node,
             service_ts,
             service_name_c_string.as_ptr(),
             &client_options,
         )
     };
+
     if result == RCL_RET_OK as i32 {
-        Ok(client_handle)
+        Ok(())
     } else {
         Err(Error::from_rcl_error(result))
     }

r2r/src/nodes.rs

@@ -849,19 +849,30 @@ impl Node {
     where
         T: WrappedServiceTypeSupport,
     {
-        let client_handle = create_client_helper(
-            self.node_handle.as_mut(),
-            service_name,
-            T::get_ts(),
-            qos_profile,
-        )?;
-        let ws = TypedClient::<T> {
-            rcl_handle: client_handle,
+        // SAFETY: The `rcl_handle` is zero initialized (partial initialization) in this block.
+        let mut client_arc = Arc::new(Mutex::new(TypedClient::<T> {
+            rcl_handle: unsafe { rcl_get_zero_initialized_client() },
             response_channels: Vec::new(),
             poll_available_channels: Vec::new(),
+        }));
+        let client_ref = Arc::get_mut(&mut client_arc)
+            .unwrap() // No other Arc should exist. The Arc was just created.
+            .get_mut()
+            .unwrap(); // The mutex was just created. It should not be poisoned.
+
+        // SAFETY:
+        // The client was zero initialized above.
+        // Full initialization happens in `create_client_helper`.
+        unsafe {
+            create_client_helper(
+                &mut client_ref.rcl_handle,
+                self.node_handle.as_mut(),
+                service_name,
+                T::get_ts(),
+                qos_profile,
+            )?;
         };
 
-        let client_arc = Arc::new(Mutex::new(ws));
         let c = make_client(Arc::downgrade(&client_arc));
         self.clients.push(client_arc);
         Ok(c)
@@ -877,20 +888,32 @@ impl Node {
         &mut self, service_name: &str, service_type: &str, qos_profile: QosProfile,
     ) -> Result<ClientUntyped> {
         let service_type = UntypedServiceSupport::new_from(service_type)?;
-        let client_handle = create_client_helper(
-            self.node_handle.as_mut(),
-            service_name,
-            service_type.ts,
-            qos_profile,
-        )?;
-        let client = UntypedClient_ {
+
+        // SAFETY: The `rcl_handle` is zero initialized (partial initialization) in this block.
+        let mut client_arc = Arc::new(Mutex::new(UntypedClient_ {
             service_type,
-            rcl_handle: client_handle,
+            rcl_handle: unsafe { rcl_get_zero_initialized_client() },
             response_channels: Vec::new(),
             poll_available_channels: Vec::new(),
+        }));
+        let client_ref = Arc::get_mut(&mut client_arc)
+            .unwrap() // No other Arc should exist. The Arc was just created.
+            .get_mut()
+            .unwrap(); // The mutex was just created. It should not be poisoned.
+
+        // SAFETY:
+        // The client was zero initialized above.
+        // Full initialization happens in `create_client_helper`.
+        unsafe {
+            create_client_helper(
+                &mut client_ref.rcl_handle,
+                self.node_handle.as_mut(),
+                service_name,
+                client_ref.service_type.ts,
+                qos_profile,
+            )?;
         };
 
-        let client_arc = Arc::new(Mutex::new(client));
         let c = make_untyped_client(Arc::downgrade(&client_arc));
         self.clients.push(client_arc);
         Ok(c)