Question

I have a static map that is a private data member. How do I initialize it in the implementation file so that it’s initial containers are empty? It is not const. It is important that nothing is in this container at start.

Answer 1

Header:

class XXX {
private:
    static std::map<X,Y> the_map; // declares static member
// ...

Implementation file:

std::map<X,Y> XXX::the_map; // defines static member

That will insert a constructor call for your map into your program initialization code (and a destructor into the cleanup). Be careful though – the order of static constructors like this between different translation units is undefined.