QT4.6.2 Windows, Q_SIGNAL is not moc'ed while Q_SIGNALS is

I am still learning QT, I read somewhere that it is more portable to use Q_SIGNAL(S) instead of signal(s) in case the code is going to use 3rd party signaling in the future (unlikely but who knows).

It took me one day to figure out that "protected Q_SIGNAL:" is different from "Q_SIGNALS:", while the latter is moc'ed correctly, the former does not create the necessary functions inside moc_file.cpp, and thus I get "undefined reference to signalfunction" compile errors!
As soon as I change it ti Q_SIGNALS the problem vanishes, not that for Q_SLOT and Q_SLOTS both work fine.

Is this some known issue? if yes where can I find other issues like this?, thanks