From: "Mauricio Fernández" <batsman.geo@...>
Date: 2003-04-16T16:27:59+09:00
Subject: Re: tutorial on embedding ruby (review)

On Wed, Apr 16, 2003 at 10:09:25AM +0900, Steve Hart wrote:
> Err....
> Perhaps I should have mentioned I am using swig.
> OK Here is an example
> 
> main()
> {
> 	ruby_init();
> 	etc
> 
> 	test()
> 	rb_gc();
> }
> 
> void test()
> {
> 	VALUE v = create me a ruby obj i dont care how
> }
> 
> So what happens to v?

Gets GC'ed because v goes out of scope and there's thus no reference to
the Ruby object in the C stack anymore.
 
> or
> 
> main()
> {
> 
> 	VALUE 	v;
> 
> 	ruby_init();
> 	etc
> 
> 	test(&v)
> 	rb_gc();
> 
> 	do some stuff that uses v
> }
> 
> void test(
> VALUE *v)
> {
> 	*v = create me a ruby obj i dont care how
> }

GC'ed too because the base of the stack is recorded in ruby_init, so v
won't be in the memory area the GC scans for VALUEs.

Workaround:

int
main()
{
 ruby_init();
 do_stuff();
}

do_stuff()
{
 VALUE v;
 test(&v);
 rb_gc();

 do some stuff that uses v
}

> My understanding is that v gets deleted in both cases (well, at least
> the first, can't remember what the thread said about the second case -
> but there again. I've read so many!). Look, it's 1.30 in the morning.
> I have a live transmission in 2 weweks time on BBC national TV. I sold

Guess that's as hard a deadline as it gets :|

> ruby/swig/OpenGL/Qt to my bosses over their choice for using NT (those
> fools!). I KNOW this will work so please help all you ruby/swig
> developers or else I am going to give it all up and become a dustman
> (pun intended!)
> My colleague says I should not post this but hey.....

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