cpp

--- fileA.h ---

struct Singleton()
{
  static Singleton* Get()
  {
     static Singleton the_instance;
     return &the_instance;
  }

  map<string, int*> addresses;
};

void foo();
void bar();

--- fileB.cpp ---

static int the_global = 42;

void foo()
{
    Singleton::Get()->addresses.insert(make_tuple(("nice"), &the_global));
}

--- fileC.cpp ---

static int the_global = 69;

void bar()
{
    Singleton::Get()->addresses.insert(make_tuple(("nice"), &the_global));
}


--- fileD.cpp ---

void piyo()
{
   foo();   
   bar();   
   assert(*Singleton::Get()->insert.find("nice") == 69);
}

void hoge()
{
   bar();   
   foo();   
   assert(*Singleton::Get()->insert.find("nice") == 42); // Not nice
}