Calling javascript functions via QJSEngine from multiple threads possible?

[jimknopf]

Hi,

I am working on a multithreaded application, and I try to use Javascript functions in this application, i.e. the worker threads would evaluate some JS code during their execution. What I found is the following:
when I use the new QJSEngine (the v8 stuff), and when I try the following (by calling run()), the program crashes:

@
QJSEngine *script_engine; // global variable
function run_func()
{
QJSValue result = engine->evaluate("1+1");
}

function run()
{
script_engine = new QScriptEngine;
QList<int> jobs;
for (int i=0;i<100;++i) jobs.append(i);
qDebug() << "starting jobs...";
QtConcurrent::blockingMap (jobs, run_func );
qDebug() << "jobs finished";
delete script_engine;
}
@

it plots an message [after the "starting jobs..." line]:
@

Fatal error in q:\qt5_workdir\w\s\qtjsbackend\src\3rdparty\v8\src\isolate.h, line 446

CHECK(isolate != 0) failed

@
I use Qt 5.1.1, and MSVC2010 32bit.

For me it looks as if only one thread can use the JS-Engine (note: this is a console app, no GUI or QML around). However, https://bugreports.qt-project.org/browse/QTBUG-23099 hints otherwise (and is closed). I did not find much in the documentation about that...
I tried the same thing with the "old" QScriptEngine, and the result was similar, i.e. a crash but here without a nice warning.

So the questions are:
(1) can a Javascript engine be used from multiple threads (QtConcurrent)?
(2) can I use multiple Javascript-engines in parallel (one engine for each thread) [I tried this briefly but got the same CHECK-error in "isolate.h"]?
(3) are there differences between QJsEngine and QScriptEngine with regard to multithreaded script execution?

thanks a lot for your answers!

best,
werner

[GoKuNiX]

Hi,

I encountered the same problem and filed a bugreport on it.
Please upvote it.

https://bugreports.qt-project.org/browse/QTBUG-33705