Namespaces with external linkage

Question

The problem I have is basically the same as \'greentype\' mentions at http://www.cplusplus.com/forum/beginner/12458/

I\'m sharing variables through namespaces and a

Answer 1

The header file should say:

namespace nn {
    extern int i;
}

This is a "declaration" not a "definition". You then want a definition in one and only one file:

namespace nn {
    int i = 1;
}

Of course, a much better approach is just to not have globals at all.