Static variable initialization - clarification

Question

I have a static variable of a class in another class.

class1.h

class1
{
public:
static class2 check;
}

class2.cpp
class2 class1::check;

Now class2.cpp has the following default constructor

class2()
{
  size = G_SIZE; //this G_SIZE is an extern variable, which gets initialized after main() is called.
}

Since the static initialization happens before the extern variable is initialized, I get 0 initialized to size. How do I handle this?

EDIT : Not sure why it is being downvoted.

Answer 1

You should never have static variables depend on other variables (especially other static variables). But that is exactly what you are doing.

The first recommendation: Don't do it. Find a better design.

The next recommendation: if you must do it (and in this case, most certainly you do not), you can wrap your access in a function, which will delay until runtime, when the values are guaranteed to be setup. See here: What is the lifetime of a static variable in a C++ function? and here: C++ static initialization order

Answer 2

By telling compiler 'static' - you will most probably get that variable initialized during mainCRTstartup - that's before main is called. If you're performing variable initialization during main, other data initialization must happen after that - you could have doInitialize() like function call, which would perform initialization of your 'check' variable.

It's also possible to have static written inside function itself - then static gets initialized when that function gets called - you could place 'static' after you initialize G_SIZE in main itself.

Playing around with order or constructors / destructors is always bit of luck game (Dangerous) - order to constructors and destructors is not guaranteed, and it's possible that you'll hit uninitialized data when initializing in static - simply because another variable was not initialized yet.

But sometimes even destructor call order might needs to be altered. -

FYI:
http://www.codeproject.com/Articles/442784/Best-gotchas-of-Cplusplus-CLI
CrtDestroyStatics.