@SGaist Multithreading with requirement of no interlocking. Because QJSEngine is not thread safe, the only way I see for now is to clone original prepared instance for each worker thread. Anything else requires syncronisation between threads, which means interlocking.

@jsulm said in QJSEngine crashes when used in multithreading program: @mdma2 said in QJSEngine crashes when used in multithreading program: I've found a bugreport that is similar to my problem Did you read the comments there? Especially this one: "You have to create the engine in the same thread as the one where you are using it. And you cannot create your function in one thread and call it in a different one.". You can't make it thread safe without changing its implementation. Is there a reason why you wantr to use it from different threads? Yeah, there's need of evaluating JS code and accessing a QJSEngine object from different threads because of my program specificity. However there should be workaround to make it possible, like switching to the engine's thread before accessing to QJSEngine object. All I have found is using signal/slot system or QMetaObject:: invokeMethod (the last one is provided in the bugreport) to do that, but none of them work at the test code, I don't know why.

Does it work in another way in Qt 6.1 or 5.15? Since you mention JavaScript, perhaps it's "trigger happy" attitude towards converting types is interfering here? To be absolutely sure which method will be called, use different method names.

Hops i forget to make the new object a type of already register with the newmetaonject

It was Nice to be able to register a meyatype converter and the QJSEngine convert for that object to a data type. Until now i create a class of QIcon and add and invokable method that returns *this. Like that i can recive on c++ a QIcon as reference Is there something that Im missing? If i create a object in c++ with QJSEngine::toScriptVale of a QIcon it works as well but like that i canto create a new object of that type and if i Change the value it chances for all c++ calls, in JavaScript is nota trivial to clone a object it was Nice to be able to clone it and fonte destroy the Last calls.

That's just a wild guess but you might be able to use Selenium as usual if your application is built for WASM. Otherwise, AFAIK, the reference tool is Squish.

Anyone can contribute to the documentation, the code, etc. You have to follow the procedures and rules but it's not some walled garden.

@NewMoon see QTBUG-38181 It's a known limitation of QJSEngine. If you can, switch to QScriptEngine (QML).

@p3c0 Thank you for your help. The problem is that what I really want in the end is a way to catch errors thrown by C++ functions transparently to the user that writes JavaScript. So, the user can just write a script like: var X = myCppFunction(foo); var Y = myOtherCppFunction(bar); etc. And when it is executed (myEngine.evaluate) the errors are catched by the C++ code of my application. Something like: try { QJSValue theVal = myEngine.evaluate(the JavaScript script); if(theVal.isError) {//if there are errors in the JS code enter here} } catch( ) { // If there is an error in the Cpp functions called by the JS code enter here } I have seen in this post that this is not currently possible with QJSEngine. In addition, I have seen that a ticket is already open. Therefore, I will have to think something to get around and wait untill the functionality is implemented. Thank you for your help.

Thanks for the reply, I will take this to the mailing list!

@zerocom I had the same issue and your comment helped me to solve it. but this solution seems to be working for predefined number of arguments for invokable functions. is there any way to create an invokable function with variable argument number similar to what we used to do by QScriptContext?

@TheHawk Have you tried giving argument to addGraph()? I don't remember whether the default argument translate well to javascript. If that still doesn't work, you can try to make add a dummy QObject class with Q_INVOKABLE functions to your engine to see if the problem is in your code or some possible interaction with QCustomPlot

I managed using the following additional lines in CustomCode QString function = "test(1)"; QJSValue testfunction = myEngine.evaluate(function); qDebug() << testfunction.toString(); With my script CustomLogic.qs looking like this: function test(x) { var a = "tested!"; a = a + x.toString(); return a; } Returns "tested!1" in the application output