struct Vtable{

    size_t offset;

    size_t function(void* ) getId;

}

struct Base{

    immutable Vtable* vptr;

    this(immutable Vtable* vptr){

        assert(vptr !is null);

        this.vptr = vptr;

    }

    size_t getId(){

        return vptr.getId((cast(void*)&this) - vptr.offset);

    }

}

​

struct Foo(size_t id){

    static immutable Vtable vtable;

    Base base;

    this(typeof(null) nil){

        this.base = Base(&vtable);

    }

    static size_t virtual_getId(Foo* foo){

        return id;

    }

    static void vtable_init(){

        Vtable* vtable = cast(Vtable*)&vtable;

        vtable.offset = base.offsetof;

        vtable.getId = cast(typeof(Vtable.getId))&virtual_getId;

    }

}

​

pragma(crt_constructor)

extern(C)void shared_static_this(){

    Foo!1.vtable_init();

    Foo!2.vtable_init();

    //Foo!3.vtable_init();

}

​

extern(C) void main(){

    auto foo1 = Foo!1(null);

    auto foo2 = Foo!2(null);

    auto foo3 = Foo!3(null);

    Base* b1 = &foo1.base;

    Base* b2 = &foo2.base;

    Base* b3 = &foo3.base;

    assert(b1.getId() == 1);

    assert(b2.getId() == 2);

    //assert(b3.getId() == 3);  //vtable is not initialized

}