I can definitely see the advantage in some cases of good breakpoint debugging with a nice IDE, but personally I like to see realtime what is happening while run

I can definitely see the advantage in some cases of good breakpoint debugging with a nice IDE, but personally I like to see realtime what is happening while running the program and changing things around, without having to stop,break,continue and repeat this cycle which stops the flow. But each to his own. And like answered already, the YouCompleteMe uses clang to provide intelligent autocompletion for C/C++.