print callback logs to std::cerr, add null check to setCallbackSink for the callback param

Author: martygrant

sycl/source/detail/ur.cpp

@@ -79,7 +79,7 @@ ur_code_location_t codeLocationCallback(void *);
 
 void urLoggerCallback([[maybe_unused]] ur_logger_level_t level, const char *msg,
                       [[maybe_unused]] void *userData) {
-  std::cout << msg << std::endl;
+  std::cerr << msg << std::endl;
 }
 
 namespace ur {

unified-runtime/source/adapters/cuda/adapter.cpp

@@ -121,7 +121,8 @@ UR_APIEXPORT ur_result_t UR_APICALL urAdapterSetLoggerCallback(
     ur_adapter_handle_t, ur_logger_callback_t pfnLoggerCallback,
     void *pUserData, ur_logger_level_t level = UR_LOGGER_LEVEL_QUIET) {
 
-  ur::cuda::adapter->logger.setCallbackSink(pfnLoggerCallback, pUserData, level);
+  ur::cuda::adapter->logger.setCallbackSink(pfnLoggerCallback, pUserData,
+                                            level);
 
   return UR_RESULT_SUCCESS;
 }

unified-runtime/source/adapters/level_zero/ur_interface_loader.hpp

@@ -125,13 +125,16 @@ class Logger {
     this->standardSink = std::move(legacySink);
   }
 
-  void setCallbackSink(ur_logger_callback_t cb, void *pUserData,
+  void setCallbackSink(ur_logger_callback_t callBack, void *pUserData,
                        ur_logger_level_t level = UR_LOGGER_LEVEL_QUIET) {
     if (!callbackSink) {
       callbackSink = std::make_unique<CallbackSink>("UR_LOG_CALLBACK");
     }
-    callbackSinkLevel = level;
-    callbackSink->setCallback(cb, pUserData);
+
+    if (callBack) {
+      callbackSink->setCallback(callBack, pUserData);
+      callbackSinkLevel = level;
+    }
   }
 
   void setCallbackLevel(ur_logger_level_t level) {