The QWaitCondition::wait method has the parameter timeout, which is unsigned long.
But on Linux a new method is introduced in QT 5.7:qt_abstime_for_timeout. This method is called by QWaitConditionPrivate::wait_relative (in line 132 in file qwaitcondition_unix.cpp).
The problem is, that the timeout parameter of "qt_abstime_for_timeout" method is int, so the unsigned long timeout is converted implicitly to int at the calling, therefore all timeout values are greater INT32_MAX will be converted to zero.