From: "Iñaki Baz Castillo" <ibc@...>
Date: 2012-05-18T04:19:29+09:00
Subject: Re: rb_gc_register_address() or rb_gc_mark()?

2012/5/17 Iñaki Baz Castillo <ibc@aliax.net>:
> - MyClass_alloc() function mallocs a C struct.
> - The C struct contains a "my_string" VALUE field and I assign there
> i.e. a Ruby String (which does not exist in Ruby land).
> - Of course MyClass_free() function should free the C struct.
>
> But, what about "my_string" VALUE within the C struct?
>
> - Let's say that I've an instance of MyClass in a global variable $my_class.
> - Then I run GC.start. Would it free my_string VALUE? (yes/no)
> - In case of yes, should then I provide a MyClass_mark() function
> which does this?:
>
>    rb_gc_mark(data->my_string)


Ok, after some experiment I'm confused:

- I run GC.startt every 0.1 seconds.

- While my_class instance (which wraps the C struct referencing
my_string VALUE) remains in the scope (or stored in a global variable)
my_string is NOT GC'd. I know it because I've stored its object_id and
used it in ObjectSpace._id2ref(id) and it returns my_string.

So... even if I've seen the usage of rb_gc_mark() in some C
extensions, in my experiments it does nothing. Any help would be
appreciated.

Thanks a lot.


-- 
Iñaki Baz Castillo
<ibc@aliax.net>