Object-orientation in C

Question

What would be a set of nifty preprocessor hacks (ANSI C89/ISO C90 compatible) which enable some kind of ugly (but usable) object-orientation in C?

I am familiar with

Answer 1

For me object orientation in C should have these features:

1. Encapsulation and data hiding (can be achieved using structs/opaque pointers)

2. Inheritance and support for polymorphism (single inheritance can be achieved using structs - make sure the abstract base is not instantiable)

3. Constructor and destructor functionality (not easy to achieve)

4. Type checking (at least for user-defined types as C doesn't enforce any)

5. Reference counting (or something to implement RAII)

6. Limited support for exception handling (setjmp and longjmp)

On top of the above it should rely on ANSI/ISO specifications and should not rely on compiler-specific functionality.