[Qt-interest] query on QCoreApplication:exec()

[Prasanta Sadhukhan]

Prasanta Sadhukhan wrote:
> Hi,
>
> From http://doc.trolltech.com/4.4/threads.html, I found that
> /Note that QCoreApplication::exec 
> <http://doc.trolltech.com/4.4/qcoreapplication.html#exec>() must 
> always be called from the main thread (the thread that executes 
> main()), not from a QThread 
> <http://doc.trolltech.com/4.4/qthread.html>. In GUI applications, the 
> main thread is also called the GUI thread because it's the only thread 
> that is allowed to perform GUI-related operations.
>
> /but in the attached application, I tried creating a linux thread from 
> main and tries to call exec from the spawned thread and exec works.
> I guess as per above line, exec() should only be calling from thread 
> running main() and not from the spawned thread, am I right?
> My question is is any thread a main thread so long it's not spawned by 
> QThread api?
>
I also saw that from QCoreApplication::exec() that

Qt Code:

   1.
      int QCoreApplication
      <http://doc.trolltech.com/latest/QCoreApplication.html>::exec()
   2.
      {
   3.
          if (!QCoreApplicationPrivate::checkInstance("exec"))
   4.
              return -1;
   5.
       
   6.
          QThreadData *threadData = self->d_func()->threadData;
   7.
          if (threadData != QThreadData::current()) {
   8.
              *qWarning("%s::exec: Must be called from the main
      thread",</b> self->metaObject()->className());*
   9.
              return -1;
  10.
          }
  11.
          

that it will throw an warning as shown above if not called from main 
thread but I did not get any warning, so I guess any thread can call 
exec() so long the thread also does QApplication(argc, argv) and it's 
not spawned by QThread api?
Can you please confirm?

Thanks
Prasanta
> Regards
> Prasanta

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