A manual garbage collector for C

	Copyright (c) 2008 ,
	 	Cloud Wu . All rights reserved.

	http://code.google.com/p/manualgc/
	http://www.codingnow.com

	ANY USE IS AT YOUR OWN RISK

At first, you should call "gc_init" to initialize the environment. 
You may not call "gc_exit" at the end, becuase the OS will release
all the resouce used by your process.

	void
	gc_init();

	void
	gc_exit();

Then, you can use 'gc_malloc' to allocate a memory block . It's return
value is the pointer to the memory (like malloc).

	void* 
	gc_malloc(size_t sz,void *parent,void (*finalizer)(void *));

	void* 
	gc_realloc(void *p,size_t sz,void *parent);

	*sz* is the the size requested

	*parent* should be the memory's life time depend on.
		*parent* can be 0 , that is to say the memory is temporary.

	*finalizer* will be called when the memory collect.
		*finalizer* can be 0 , collector will do nothing.

"gc_enter" and "gc_leave" is important , they tell the collector the
life time of temporary memory blocks. All the memory allocated by 
"gc_new" after a "gc_enter" can be collect after "gc_leave", only if
you link them to the others be related to the root , or tell "gc_leave"
what you want to extend the life time.

	void 
	gc_enter();

	void 
	gc_leave(void *p,...);

You don't need put enter/leave in every function. If your program have a
main loop, put one "gc_enter" before entering the main loop, and put one 
"gc_leave" is enough. For example:

	while (!quit) {
		gc_enter();
		quit=mainloop();
		gc_leave(0);
	}

You can use "gc_link" to establish or remove the relationship of two 
memory block. (ps. Pass parent into gc_malloc or gc_realloc will establish 
the relationship automatic)

	void 
	gc_link(void *parent,void *prev,void *now);

	Unlink "prev" from "parent" first, and then link "now" to the 
	"parent". For example, If you do 

		a->b = c;	// a and c are both gc memory block
	
	Then you should call

		gc_link(a,a->b,c);

	You can also link a memory block to the root by pass "parent" 0.
	This is useful when you want to hold a global variable.

Collector will not be executed automatically. 

	void 
	gc_collect();

	This will collect all the memory block that can no longer be 
	otherwise accessed. Before free it , collector will call the 
	finalizer if you provided.

	void 
	gc_dryrun();

	Only for debug, it will print some useful information instead of 
	collecting the garbage.