static unordered_map is erased when putting into different compilation unit in XCode

Question

I have a static unordered_map in my class C. I experience difference in behaviour if I put my class definition and declaration in different files from the file containing functi

Answer 1

Thanks, guys! Following Dietmar's advice, I did this:

class C{
//...
private:
  static unordered_map& m();
};

unordered_map& C::m()
{
  static unordered_map m;
  return m;
}

and then I kept referring to m(). It is strange that it did not happen before. I guess I got lucky. But then, this should be a case for a warning message, shouldn't it?

---

To avoid mistakes like this I will use the following macros to declare and define static variables:

/// Use this macro in classes to declare static variables
#define DECLARE_STATIC(type, name) static type& name();

/// Use this macro in definition files to define static variables
#define DEFINE_STATIC(type, name) type& name(){static type local; return local;}

Usage in this case:

class C{
//...
private:
  DECLARE_STATIC(unordered_map, m);
}
DEFINE_STATIC(unordered_map, m)