QApplication exec() creates new thread / process?

In QApplication if we call exec() then doe开发者_Go百科s a new process / thread start?

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No, calling exec will:

Enters the main event loop and waits until exit() is called, then returns the value that was set to exit() (which is 0 if exit() is called via quit()).

It is necessary to call this function to start event handling. The main event loop receives events from the window system and dispatches these to the application widgets.