From: Joel VanderWerf <joelvanderwerf@...>
Date: 2011-07-03T04:34:01+09:00
Subject: Re: Ruby C API:How to prevent a VALUE being collected by the garbage collecter?

On 07/02/2011 11:35 AM, Kim Burgestrand wrote:
>
> On Saturday, 2 July 2011 at 18:35, Quintus wrote:
>
>>> Ruby C API:How to prevent a VALUE being collected by the garbage
>>> collecter? Is there any function to call?
> If you want it to never be collected, make it a global variable. rb_gc_mark will
> only do what you want until the next GC cycle.

That's right. Take a look at README.EXT in ruby source, which says:

> GC should know about global variables which refer to Ruby's objects, but
> are not exported to the Ruby world.  You need to protect them by
>
>   void rb_global_variable(VALUE *var)

So if you do this:

VALUE my_global;
...
   rb_global_variable(&my_global);

Then whatever object is referenced by my_global when GC runs will not be 
collected.

If you just want to protect some VALUEs that are not necessarily pointed 
to by C variables, you could just keep them in a (ruby) array or other 
data structure, as long as that array is reachable from some variable 
known to ruby.