gdc and gcc object linking issues

[Kagamin]

A class declaration is simply a declaration, it doesn't allocate 
storage, so members end up being implicitly extern (or static 
inline for methods with bodies) except for instance fields, whose 
storage is allocated with the new operator. As static inlining a 
field has no sense, it becomes extern. You can declare extern 
variables in C too (try it). Extern declarations are included 
into each including module, but you can't do it with the 
variable's storage itself, so you should *define* the variable in 
a module where it will actually keep its value. If you define a 
variable in the header, it will be included in each including 
module and you'll get several instances of the variable and 
symbol collision at link time.

You can think of a class as an interface declaration which 
happens to expose some implementation details to you.