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    Bug 
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    Resolution: Done
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    P3: Somewhat important 
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    5.4.1
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    None
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    Windows 8.1 with Qt5.4.1
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        847d5d1309a4365af7d0f4fa1bff5754b8286e34 (qtbase/5.6, 23.9.2015, 5.6b)
On Windows 8.1 with Qt5.4.1, QGuiApplication::sessionId returns an empty string whereas QCoreApplication::sessionId on Windows Vista with Qt4.7.2 was returning a non-empty one.
Qt Forums think it is a regression.
https://forum.qt.io/topic/57596/qguiapplication-sessionid-returns-an-empty-string/2