Define global var that is type of QScriptEngine throws exception

[qstudy]

in common.h i declare global var as
@
extern QScriptEngine engine;
@
in main.cpp, i define it as

@
#include "common.h"

QScriptEngine engine;

int main(int argc, char *argv[])
{
QApplication a(argc, argv);

MainWindow w;
w.show();

return a.exec();

}
@
when i start application, it throws Excetpion:

this application has requested the Runtime to terminate it in an unusual way.
please contact the application's support team for more information.

return code 3

Any idea what I can do?

Thanks a lot.

Edit: Fixed code tags. Please wrap with @; mlong

[lgeyer]

You cannot create a script engine (and many other Qt objects) as long as you haven't created a Q(Core)Application.
@
QScriptEngine* engine;

int main(int argc, char *argv[])
{
QApplication a(argc, argv);

engine = new QScriptEngine(&a);

MainWindow w; 
w.show(); 

return a.exec();

}
@
Passing the script engine as a global variable is a very questionable design decision. A better choice would be subclassing QApplication and adding it as a member or storing it as a property of QApplication (the QApplication instance is accessible from anywhere using qApp() or QCoreApplication::instance()).