qapplication with open(/dev/name,O_RDWR) crashed???

[ttbug]

//my demo program
main(argc,argv)
{
QApplication a(argc,argv);
int fp = open("/dev/devname",O_RDWR);
//open err
}
//
main(argc,argv)
{
int fp = open("/dev/devname",O_RDWR);
QApplication a(argc,argv);
//open() is correct, but QApplication a(argc,argv) cannot stop;
}

any body can help me????