In Qt Creator, create a new Qt Quick Controls 2 application "testDeploy", in c:\Code\testDeploy.

Build this app in release mode. under the default c:\Code\build-testDeploy-Desktop_Qt_5_8_0_MSVC2013_64bit-Release

Run it (just to be sure it runs before running windeploy_qt).

Next go to command line and run windeploy_qt:

c:\Code\build-testDeploy-Desktop_Qt_5_8_0_MSVC2013_64bit-Release\release>c:\Qt\5.8\msvc2013_64\bin\windeployqt.exe --qmldir c:\Code\testDeploy testDeploy.exe

Next, try to run it again from Qt Creator or from Explorer. You will receive an error that qrc:/main.qml:-1 cannot be found.

QQmlApplicationEngine failed to load component
qrc:/main.qml:-1 File not found

This problem does not exhibit in 5.7.