From: Eric Hodel <drbrain@...7.net>
Date: 2011-08-03T05:03:16+09:00
Subject: Re: Help in Pointer

On Aug 1, 2011, at 6:11 PM, Tridib Bandopadhyay wrote:
> I got to know from this forum before that the Garbage Collector just 
> scans the stack looking for pointers. So, if we allocate a pointer and 
> hide data behind the pointer the Garbage Collector won't see pointers 
> which aren't on the stack.
> 
> As I am working on Garbage Collector and want to implement manual memory 
> deallocation so I need to hide data from the garbage collector applying 
> the above technique.

You can inform the garbage collector of your pointer through Data_Wrap_Struct and Data_Make_Struct.  From README.EXT:

> 3.3 Encapsulate C data into a Ruby object
> 
> To wrap and objectify a C pointer as a Ruby object (so called
> DATA), use Data_Wrap_Struct().
> 
>   Data_Wrap_Struct(klass, mark, free, ptr)
> 
> Data_Wrap_Struct() returns a created DATA object.  The klass argument
> is the class for the DATA object.  The mark argument is the function
> to mark Ruby objects pointed by this data.  The free argument is the
> function to free the pointer allocation.  If this is -1, the pointer
> will be just freed.  The functions mark and free will be called from
> garbage collector.

Does this answer your questions?

For further reading:

http://svn.ruby-lang.org/cgi-bin/viewvc.cgi/trunk/README.EXT?view=markup