Objective-C through a preprocessor

Question

Answer

A program translating Objective-C to C needs to perform the following actions:

• Translate instance variable declarations in a class interface into a structure definition. Each generated structure describes all instance variables of the class' instances.
• Translate every method implementation into a function with exactly the same arguments as the method, plus the implicit first two arguments self and _cmd. Within the method, all references to an instance variable ivar translate to self->ivar.
• Translate every method invocation into a lookup of the function implementing the method for this object, followed by an invocation of that function. (On NeXT's runtime, both the lookup and invocation are performed by a single function).
• For every message sent to a named class, like alloc in [[MyClass alloc] init], invoke a runtime library function to obtain the class object to which the factory message can be sent.
• For every object file created, build the data structures used by the runtime for every class implementation and protocol declaration. Also output a constructor function to have the runtime library add the information in this object file to its data structures.
• All Objective-C specific warnings and errors must be generated by the translator, since obviously the C compiler has no notion of Objective-C concepts.

An existing, available Objective-C Translator is OCT though a quick glance shows it seems both rather Amiga oriented and old (i.e. there is no ./configure, me spoiled brat).