How to read QProcess output

Question

In the main thread of a Gui Application I am starting a QProcess of another GUI application that will log some messages over time in stdout using fputs(). The problem is that after some time the GUI application started with QProcess will freeze because it's output is not consumed by the parent. I know that this is the problem because if I am starting the QProcess with QIODevice::NotOpen or QIODevice::Unbuffered argument, it will not get stuck but the output will never be reached. I've tried to connect the readyRead, readyReadStandardError, readyReadStandardOutput signals of the subprocess to a slot in the parent, but for some reasons the signals are never emitted. I am also flushing the stdout after each write. My question is how to force QProcess to send some data in real time without closing it?

The connection of the signals, (T- is a wrapper for QProcess):

process->setWorkingDirectory(workingDir);
process->start(prog, argumentsList);
process->waitForStarted();
T* reciver = new V8QProcess(process);
QObject::connect(process, &QProcess::readyRead, reciver, &V8QProcess::OnMessageRecieved);
QObject::connect(process, &QProcess::readyReadStandardError, reciver, &V8QProcess::OnMessageRecieved);
QObject::connect(process, &QProcess::readyReadStandardOutput, reciver, &V8QProcess::OnMessageRecieved);

The code of the subprocess that will log in stdout:

QByteArray bytes = LogMsg::getDisplayable(logMsg, 0).toUtf8();
fputs(bytes.constData(), stdout);
fflush(stdout);

The code of the OnMessageRecieved:

 if (!p) { // p is the QProcess
    return;
}
QByteArray output;
output.append(p->readAllStandardError()).append(p->readAll());
QString message = QString::fromStdString(output.toStdString()); 

This approach is working when running a shell script or other simple program.

Answer 1

I found out what the problem was on my case: Because I was starting the QProcess in a std::Thread, the events(signals) that occur were skipped because std::Thread don't have a queue of events as QThread or QApplication does. The solution that I use is: 1. Use QThread instead of std::thread 2. Call QCoreApplication::proccesEvents() from time to time.

The proper solution is to use QThread::exec() in order to create an event loop, but this approach would block the GUI Application, so in my case is no good.