Running QThread::run() immediately crashes the application

I start coding a small qt application to compute checksums. After the unthreaded code run fine I moved to a more responsive way since the mainwindow blocks while computing a hash of a bigger file.

But calling the run() method failes for unknown reason. I even cleared out the run-method completely. No matter what I do: SIGSEV.

Other threaded code from the qt help compile and run without problems - even threaded code in other apps I coded still run, but this not:

the header:

#include <QThread>
class Hasher : public QThread
{
    Q_OBJECT

public:
    Hasher();
    void computeHash();

protected:
    void run();

};

the impleme开发者_高级运维ntation

#include "hasher.h"

Hasher::Hasher()
{
}

void Hasher::computeHash() {
    start();
}

void Hasher::run() {
    // compute the hash, but for now simply return
}

caller

Hasher h
h.computeHash();

As I said above all works well without threads but crashes when using threads. I am using QT 4.7.3 on a 64bit ARCH-Linux - and I am really clueless about this. Maybe someone can help.

---

If you do like this your thread will be created on stack and it will be destroyed while the thread is still running !

void myfunction ()
{
 Hasher h
 h.computeHash();

}

NeilMonday's example works because he has a return a.exec(); in his code which keeps Hasher thread alive on the stack. So you have to make your thread live longer.

1. Either make it a member variable of you class or
2. Create it on the heap like Hasher* h = new Hasher (); or
3. Use QtConcurrentRun and QFuture and do not mess with threads.

---

The code you posted runs on my machine. I just have a main.cpp, haser.h, and hasher.cpp. The file hasher.h looks the same as yours, but here are my other files.

Here is what my main.cpp looks like:

#include "hasher.h"
#include <iostream>
#include <QtCore/QCoreApplication>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    Hasher h;
    h.start();

    while(true)
    {
        std::cout<<"test1" << std::endl;
    }
    return a.exec();
}

and here is hasher.cpp:

#include "hasher.h"
#include <iostream>
Hasher::Hasher()
{
}

void Hasher::computeHash() {
}

void Hasher::run() {
    // compute the hash, but for now simply return
    while(true)
    {
        std::cout<<"TEST 2" << std::endl;
    }
}

I am running on Windows 7 64 with Qt 4.6.3 though.

Also, I assume your code is more complex than this, and it is very important to do Mutual Exclusion. See QMutex if you haven't already.