fix(ChakraJavaScriptExecutor): Ensure JS arguments are not GC'd (microsoft#752)

rozele · web-flow · commit 9070e9967e18 · 2016-10-07T10:03:57.000-04:00
A number of users were seeing AccessViolationExceptions, especially in Release builds, where JS strings were being GC'd prior to use. I suspect this is because we need to increment the ref count of the marshalled arguments so they are not collected before use as call arguments. Fixes microsoft#751
diff --git a/ReactWindows/ReactNative/Chakra/Executor/ChakraJavaScriptExecutor.cs b/ReactWindows/ReactNative/Chakra/Executor/ChakraJavaScriptExecutor.cs
@@ -64,13 +64,26 @@ public JToken CallFunctionReturnFlushedQueue(string moduleName, string methodNam
             if (arguments == null)
                 throw new ArgumentNullException(nameof(arguments));
 
-            var method = EnsureCallFunction();
+            var moduleNameValue = JavaScriptValue.FromString(moduleName);
+            moduleNameValue.AddRef();
+            var methodNameValue = JavaScriptValue.FromString(methodName);
+            methodNameValue.AddRef();
+            var argumentsValue = ConvertJson(arguments);
+            argumentsValue.AddRef();
+
             var callArguments = new JavaScriptValue[4];
             callArguments[0] = EnsureGlobalObject();
-            callArguments[1] = JavaScriptValue.FromString(moduleName);
-            callArguments[2] = JavaScriptValue.FromString(methodName);
-            callArguments[3] = ConvertJson(arguments);
-            return ConvertJson(method.CallFunction(callArguments));
+            callArguments[1] = moduleNameValue;
+            callArguments[2] = methodNameValue;
+            callArguments[3] = argumentsValue;
+            var method = EnsureCallFunction();
+            var flushedQueue = ConvertJson(method.CallFunction(callArguments));
+
+            argumentsValue.Release();
+            methodNameValue.Release();
+            moduleNameValue.Release();
+
+            return flushedQueue;
         }
 
         /// <summary>
@@ -96,12 +109,22 @@ public JToken InvokeCallbackAndReturnFlushedQueue(int callbackId, JArray argumen
             if (arguments == null)
                 throw new ArgumentNullException(nameof(arguments));
 
-            var method = EnsureInvokeFunction();
+            var callbackIdValue = JavaScriptValue.FromInt32(callbackId);
+            callbackIdValue.AddRef();
+            var argumentsValue = ConvertJson(arguments);
+            argumentsValue.AddRef();
+
             var callArguments = new JavaScriptValue[3];
             callArguments[0] = EnsureGlobalObject();
-            callArguments[1] = JavaScriptValue.FromInt32(callbackId);
-            callArguments[2] = ConvertJson(arguments);
-            return ConvertJson(method.CallFunction(callArguments));
+            callArguments[1] = callbackIdValue;
+            callArguments[2] = argumentsValue;
+            var method = EnsureInvokeFunction();
+            var flushedQueue = ConvertJson(method.CallFunction(callArguments));
+
+            argumentsValue.Release();
+            callbackIdValue.Release();
+
+            return flushedQueue;
         }
 
         /// <summary>
@@ -229,22 +252,23 @@ private JToken ConvertJson(JavaScriptValue value)
 #else
         private JavaScriptValue ConvertJson(JToken token)
         {
+            var jsonString = token.ToString(Formatting.None);
+            var jsonStringValue = JavaScriptValue.FromString(jsonString);
+            jsonStringValue.AddRef();
             var parseFunction = EnsureParseFunction();
-
-            var json = token.ToString(Formatting.None);
-            var jsonValue = JavaScriptValue.FromString(json);
-
-            return parseFunction.CallFunction(_globalObject, jsonValue);
+            var jsonValue = parseFunction.CallFunction(_globalObject, jsonStringValue);
+            jsonStringValue.Release();
+            return jsonValue;
         }
 
         private JToken ConvertJson(JavaScriptValue value)
         {
             var stringifyFunction = EnsureStringifyFunction();
-
-            var jsonValue = stringifyFunction.CallFunction(_globalObject, value);
-            var json = jsonValue.ToString();
-
-            return JToken.Parse(json);
+            var jsonStringValue = stringifyFunction.CallFunction(_globalObject, value);
+            jsonStringValue.AddRef();
+            var jsonString = jsonStringValue.ToString();
+            jsonStringValue.Release();
+            return JToken.Parse(jsonString);
         }
 #endif
 
