QThread::getCurrentThread() from non-Qt thread

multithreading, qt

Solution

`QThread` is just a wrapper, behind the scene it uses native threads.

`QThread::currentThread` creates and initialises a `Q(Adopted)Thread` instance if it doesn't exist yet.

In case of unix it uses `pthread`s.

#include <iostream>
#include <thread>
#include <pthread.h>

#include <QThread>
#include <QDebug>

void run() {
    QThread *thread = QThread::currentThread();

    qDebug() << thread;
    std::cout << QThread::currentThreadId() << std::endl;
    std::cout << std::this_thread::get_id() << std::endl;
    std::cout << pthread_self() << std::endl;

    thread->sleep(1);
    std::cout << "finished\n";
}

int main() {
    std::thread t1(run);
    t1.join();
}

Output:

QThread(0x7fce51410fd0) 
0x10edb6000
0x10edb6000
0x10edb6000
finished

I see that there is initialisation of Qt application main thread:

data->threadId = (Qt::HANDLE)pthread_self();
if (!QCoreApplicationPrivate::theMainThread)
    QCoreApplicationPrivate::theMainThread = data->thread;

So there might be some side effects.

I'd advise not to mix QThread with non-Qt threads.

Problem

Original source