dnn: prevent unloading of InferenceEngine plugins

modules/dnn/src/op_inf_engine.cpp

@@ -564,11 +564,45 @@ static std::map<std::string, InferenceEngine::InferenceEnginePluginPtr>& getShar
     return sharedPlugins;
 }
 #else
-InferenceEngine::Core& getCore()
+static bool init_IE_plugins()
+{
+    // load and hold IE plugins
+    static InferenceEngine::Core* init_core = new InferenceEngine::Core();  // 'delete' is never called
+    (void)init_core->GetAvailableDevices();
+    return true;
+}
+static InferenceEngine::Core& create_IE_Core_instance()
 {
     static InferenceEngine::Core core;
     return core;
 }
+static InferenceEngine::Core& create_IE_Core_pointer()
+{
+    // load and hold IE plugins
+    static InferenceEngine::Core* core = new InferenceEngine::Core();  // 'delete' is never called
+    return *core;
+}
+InferenceEngine::Core& getCore()
+{
+    // to make happy memory leak tools use:
+    // - OPENCV_DNN_INFERENCE_ENGINE_HOLD_PLUGINS=0
+    // - OPENCV_DNN_INFERENCE_ENGINE_CORE_LIFETIME_WORKAROUND=0
+    static bool param_DNN_INFERENCE_ENGINE_HOLD_PLUGINS = utils::getConfigurationParameterBool("OPENCV_DNN_INFERENCE_ENGINE_HOLD_PLUGINS", true);
+    static bool init_IE_plugins_ = param_DNN_INFERENCE_ENGINE_HOLD_PLUGINS && init_IE_plugins(); CV_UNUSED(init_IE_plugins_);
+
+    static bool param_DNN_INFERENCE_ENGINE_CORE_LIFETIME_WORKAROUND =
+            utils::getConfigurationParameterBool("OPENCV_DNN_INFERENCE_ENGINE_CORE_LIFETIME_WORKAROUND",
+#ifdef _WIN32
+                true
+#else
+                false
+#endif
+            );
+    static InferenceEngine::Core& core = param_DNN_INFERENCE_ENGINE_CORE_LIFETIME_WORKAROUND
+            ? create_IE_Core_pointer()
+            : create_IE_Core_instance();
+    return core;
+}
 #endif
 
 #if !defined(OPENCV_DNN_IE_VPU_TYPE_DEFAULT)