It should be documented that QFile::setPermissions() cannot be used to change the file permissions on Windows

There is not mentioned in the QFile::setPermissions() (or QFileDevice::Permission) that it is not possible to change the file permissions on Windows with that function. It only checks if the file is read-only or not.

http://qt-project.org/doc/qt-5/qfile.html#setPermissions
http://qt-project.org/doc/qt-5/qfiledevice.html#Permission-enum