In this case, we not need thread-safe for CCLogger::Get.
CCLogger::Get should call first in CodeCompletion::CodeCompletion():
So you're admitting that you're using this singleton as glorified global variable? 
That's exactly how the entire project is organized, every "...Manager" class, whether it's configuration, project, buildtargets or whatever.
You can debate whether that's bad design or not, whether singletons are better or worse or the same as global variables, but that's what it is, really. Someone (most probably Yiannis?) started it that way, and everyone (including me) continued that way. The fact that we use singletons everywhere didn't cause a lot of trouble during the years either. Yes, we won't win the first prize in the OOP design contest, so what. The point is, it works, and it works in a kind-of-defined way.
In at least one case (config) there is an urgent reason behind it too, in most other cases I guess one cold probably do otherwise, if one cares to spend many hours rewriting a lot of code.
