[jacquesm]

That's a very good point, in fact I always use the various global state variables of a program to explain the complexity of the program to others to show them why they can't possibly know their programs do not contain bugs simply because they have not tested all possible states.

Thank you for pointing this out, it is a very important thing to realize and it applies to configurables, global variables and feature switches alike. The more you have seen of the guts of complex systems the more amazed you will be that they work at all.