[Qt-interest] return to command line but the GUI is still alive

[Thiago Macieira]

Em Terça-feira 26. Janeiro 2010, às 04.19.06, Forest Yang escreveu:
> > int main(int argc, char** argv)
> > {
> >   pid_t pid;
> > 
> >   pid=fork();
> >   if (pid==0)
> >   {
> >     /* we're the child */
> >     QApplication qapp(argc, argv);
> >     MainWindow mainWindow;
> >     mainWindow.show();
> > 
> >     qapp.setMainWidget(&mainWindow);
> >     qapp.exec();
> >   }
> > }

Remember these rules about fork():

1) one side must either execve() or _exit(). That's a strict rule and 
independent of Qt. 

If neither side does exec (like the example above), then one of the two must 
exit via _exit. So the code above is incorrect since both sides exit via 
return from main.

2) if you used Qt code before the fork, then only one side of the fork can use 
it afterwards. If you managed not to use in either side, then it's ok to use 
it in both.

Note that using Qt in static objects counts as using Qt before the fork. This 
includes any Qt code that happens before main() as well.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358
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