Wt

A short example:

void postSig()
{
    Wt::WApplication::UpdateLock lock(wApp);
    if (lock)
    {
        qDebug() << "postSig" << "docroot:" << wApp->docRoot().c_str();
    }
    else
    {
        qDebug() << "something terrible";
    }
}

void sendSig()
{
    qDebug() << "sendSig" << "docroot:" << wApp->docRoot().c_str();

    Wt::WServer::instance()->post(wApp->sessionId(), boost::bind(&postSig));
}


Wt::WApplication* createApplication(const Wt::WEnvironment& env)
{
    Wt::WApplication *app = new Wt::WApplication(env);
    app->enableUpdates(true);

    qDebug() << "create" << "docroot:" << app->docRoot().c_str();

    Wt::WPushButton *b = new Wt::WPushButton("send sig", app->root());
    b->clicked().connect(boost::bind(&sendSig));

    return app;
}

WApplication::docRoot returns empty string in the postSig function. In other functions it returns correct value.

I use Wt 3.3.1