From: Sean O'Dell <sean@...>
Date: 2004-07-30T23:34:34+09:00
Subject: Re: C ext: GC claiming objects early

On Friday 30 July 2004 07:06, Tilman Sauerbeck wrote:
> ts <decoux@moulon.inra.fr> [2004-07-30 15:43]:
> > >>>>> "T" == Tilman Sauerbeck <tilman@code-monkey.de> writes:
> >
> > T> "some_meth" will instantiate a new "Result" object. Using this Result
> > T> object, the caller can wait for the function to succeed, he can
> > register T> callbacks etc.
> >
> >  Well it's best if you post the *real* C code : it's easy to understand
> >  than this strange language, called english.
>
> Heh :)
>
> Here's the code for the method "some_meth", let's just call it
> "playback_playtime" now ;D
>
> static VALUE c_playback_playtime (VALUE self)
> {
> 	xmmsc_result_t *res;
>
> 	/* this just wraps Data_Get_Struct */
> 	GET_OBJ (self, xmmsc_connection_t *, xmms);
>
> 	res = xmmsc_playback_playtime (*xmms);
>
> 	/* now create a new Result object from the C struct */
> 	return TO_XMMS_CLIENT_RESULT (self, res);
> }
>
> VALUE TO_XMMS_CLIENT_RESULT (VALUE parent, xmmsc_result_t *res)
> {
> 	VALUE self;
> 	RbResult *rbres = NULL;
>
> 	if (!res)
> 		return Qnil;
>
> 	self = Data_Make_Struct (cResult, RbResult, c_mark, c_free, rbres);
> 	rbres->real = res;
> 	rbres->parent = parent;
> 	rbres->callback = Qnil;
>
> 	rb_obj_call_init (rbres->self, 0, NULL);
>
> 	return self;
> }
>
> 'parent' is the Ruby object that the object marks in c_mark
>
> This is the "notifier" method of the Result object and the callback used
> to call the given block:
>
> static void on_signal (xmmsc_result_t *res2, void *data)
> {
> 	/* call the block and create a new Result object from res2, too */
> 	rb_funcall ((VALUE) data, rb_intern ("call"), 1,
> 	            TO_XMMS_CLIENT_RESULT (Qnil, res2));
> }
>
> static VALUE c_notifier_set (VALUE self)
> {
> 	GET_OBJ (self, RbResult, res);
>
> 	if (!rb_block_given_p ())
> 		return Qnil;
>
> 	res->callback = rb_block_proc ();
> 	xmmsc_result_notifier_set (res->real, on_signal, (void *) res->callback);
>
> 	return Qnil;
> }
>
> It's pretty straight-forward and the comment should explain it all :)

Show me a couple more things.  Show me the Ruby code you call, and tell me 
what object is getting collected and where it happens.  Your original Ruby 
code example was pseudocode and I can't tell what maps to what.

	Sean O'Dell