Also, because I usually split the project into small modules I have a bunch of extern declarations here..

It sounds a bit like you have some externs defined system wide. Normally I only have "public" variables available in the .h file on a module by module basis, so that the variables are not "exposed" to modules that don't need them. It's not a horribly dangerous situation, but it's tidier I think. Even better is to use Get() and Set() functions on the module and not expose the variable at all. That kind of depends on having the CPU resources to do it. Of course most good programming practice has a cost.