The problem here would be exactly the same regardless of what form this type took. The issue is fundamental to any low level language: the size of a type is a part of its public API (well, ABI), by definition. This is true in C++ with private fields as well, for example: if you add a private field to a class, or change the type of a private field with one of a different size, all code using that class has to be re-built. The only way to abstract this is to use types strictly through pointers, the way Java does.