Qt 脚本多线程

Question

我需要同时运行多个（最多 50 个或更多）Qt 脚本函数。使用脚本函数运行两个或三个线程就可以了，但是当我运行大约 50 个线程时，我得到一个错误并且我的程序崩溃了。

ASSERTION FAILED: globalData().dynamicGlobalObject (..\3rdparty\javascriptcore\JavaScriptCore\runtime/JSGlobalObject.h:411 QTJSC::JSGlobalObject* QTJSC::ExecState::dynamicGlobalObject())

我的 main.cpp 看起来像这样：

#include <QCoreApplication>
#include <QScriptEngine>
#include <threadworker.h>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QScriptEngine engine;
    QScriptValue val = engine.evaluate("(function() {var r = Math.random(); while(1>0) print(r);})");
    ThreadWorker *worker[50];
    for(int i=0;i<50;i++) {
        worker[i] = new ThreadWorker(val);
        QObject::connect(worker[i], SIGNAL(needsStarting()), worker[i], SLOT(startScript()));
        emit worker[i]->needsStarting();
    }
    return a.exec();
}

这是我的 threadworker.h：

#ifndef THREADWORKER_H
#define THREADWORKER_H

#include <QObject>
#include <QScriptValue>
#include <QThread>

class ThreadWorker : public QObject
{
    Q_OBJECT
public:
    explicit ThreadWorker(QObject *parent = 0);

    explicit ThreadWorker(QScriptValue function);

signals:
    needsStarting();
public slots:
    void startScript();
private:
    QScriptValue value;
    QThread thread;
};

#endif // THREADWORKER_H

这是我的 threadworker.cpp：

#include "threadworker.h"
#include <QDebug>

ThreadWorker::ThreadWorker(QObject *parent) : QObject(parent)
{
}

ThreadWorker::ThreadWorker(QScriptValue function)
{
    value = function;
    this->moveToThread(&thread);
    thread.start();
}

void ThreadWorker::startScript()
{
    value.call();
}

我预计，无论数量多少，Qt 脚本线程都可以正常运行，但我不明白是什么导致了这种相反的行为。

Answer 1

将QScriptEngine 放在worker 类上，让moveToThread 将其移至worker 线程，似乎可以解决：

class Worker : public QObject
{
    Q_OBJECT
public:
    explicit Worker(QObject *parent = 0);

public slots:
    void startScript(const QString &function);

private:
    QScriptEngine engine;
    QScriptValue value;
};

但是，创建这么多线程并在应用程序退出时正确释放它们将是一个挑战。我建议你使用池线程，例如QtConcurrent。 QtConcurrent 允许您（例如但不限于）仅具有函数的多线程，而不是必需的类，并且使用 QFutureSyncronyzer 您可以在一个调用中等待您想要完成的所有线程。见QtConcurrent:

#include <QtScript>
#include <QtConcurrent>

#define THREADS 50

void worker_function(const QString &function)
{
    QScriptEngine engine;
    QScriptValue value;

    value = engine.evaluate(function);
    value.call();
}

...
QFutureSynchronizer<void> synchronizer;

//Set the max pooled threads
QThreadPool::globalInstance()->setMaxThreadCount(THREADS);

//Start all threads and add them to the future synchronizer
for (int i = 0; i < THREADS; i++)
    synchronizer.addFuture(QtConcurrent::run(worker_function, QString("(function() {var r = Math.random(); while(1>0) print(r);})")));

//Wait for all threads to finish
synchronizer.waitForFinished();
...