Did you actually build a debug version of your app? If you are using Qt Creator, are you running it in debug mode (that is, is your build target a debug build)?

Crashes on startup are usually due to trying to use an uninitialized or null pointer but could also be the result of accessing beyond the bounds of an array (eg. an incorrect index, or trying to read / write an uninitialized array). It won't be a bug in Qt.