Cobbler: A Primitive C Object System

Cobbler is an attempt to add objects to the C language in order to better understand the implementations of dynamic object systems such as that of Smalltalk and Objective-C.

Objects, known as primitives, are created using C Macros to define their properties and behavior. Memory management is handled through reference counting, using the own and disown functions. With autodiswon, primitives can be assigned to a thread-specific pool of objects to automatically release at the end of some scope.

Basic Usage

To define a new primitive object, use the primitive_define() macro function. Pass in the name of the primitive, the super primitive, a structure to represent the data, and any virtual methods used. Virtual methods are added using the using_virtual() macro function after the structure is defined.

primitive_define(my_primitive, primitive, {
		int a_number;
		char a_char;
	},
	virtual(my_primitive, create),
	virtual(my_primitive, destroy));

You can forward-declare the primitive using the primitive_declare() macro. This can be useful when using the method() macro for declaring virtual methods for the primitive before you define the primitive itself.

primitive_declare(my_primitive)

my_primitive *method(my_primitive, create, int a_number, char a_char);
void          method(my_primitive, destroy);
int           method(my_primitive, getNumber);

primitive_define(my_primitive, primitive, {
		int a_number;
		char a_char;
	},
	virtual(my_primitive, create),
	virtual(my_primitive, destroy),
	virtual(my_primitive, getNumber));

The method() macro can be used for defining non-virtual methods too.

int method(my_primitive, non_virtual_method);

Virtual methods are called using the virtual_call() macro function, whereas non-virtual methods can either be called directly or through the static_call() macro function.

The virtual_call() macro must be supplied with the return type, followed by the virtual method name, the primitive instance, and then finally any function arguments for the method.

The static_call() macro must be supplied with the primitive name, followed by the method name, the primitive instance, and then finally any function arguments for the method.

my_primitive *p = create(my_primitive, 10, 'a');

int result = virtual_call(int, getNumber, p);
int other  = static_call(my_primitive, non_virtual_method, p);