From: Eric Hodel <drbrain@...7.net>
Date: 2012-05-19T09:04:28+09:00
Subject: Re: rb_gc_register_address() or rb_gc_mark()?

On May 18, 2012, at 00:20, Hans Mackowiak wrote:
> Eric Hodel wrote in post #1061208:
>> On May 17, 2012, at 12:31, Hans Mackowiak wrote:
>>> i create an hash from the C-side, mark them with rb_global_variable and
>>> then store my objects into them
>>> 
>>> this protects my objects from being deleted.
>> 
>> 
>> This is probably wrong.
>> 
>> By using rb_global_variable the object can never be reclaimed by the
>> garbage collector.
>> 
>> You should either:
>> 
>> Return a ruby object to the user that stores your Hash.
>> 
>> Use Data_Wrap_Struct/Data_Make_Struct to store your Hash and use
>> rb_gc_mark to indicate it is still alive.
>> 
>> Use a constant, class or instance variable on a pre-defined class to
>> store your Hash.
> 
> no its correct i want the control when the GC gets the object or not.
> thats why i use a hash, when my binding removes the object out of the 
> hash, GC deleteds it. but no earlier

I was unclear, you should probably not use rb_global_variable on your Hash.  You should instead bind your Hash as a regular ruby constant, wrap it in a struct, or return it as part of a regular ruby object.