From: Rolando Abarca <funkaster@...>
Date: 2009-05-07T06:08:06+09:00
Subject: Re: storing c pointers in ruby hash

also, if I try to inspect the contents of the hash, I also get a core  
dump.

On May 6, 2009, at 4:59 PM, Rolando Abarca wrote:

> Hi all,
> I'm been banging my head on the keyboard the whole day trying to  
> track a bug.
> I have a embedded ruby (branch 1_9_1, checked out today) running on  
> a Objective-C project (if anyone's interested, it's this project: http://github.com/funkaster/shinycocos/tree/master) 
> .
> The idea is to keep a reference to the ruby counterpart of the Obj-C  
> object. Right now, I'm using a "global" hash table, defined as this:
>
> 	VALUE sc_object_hash = rb_hash_new();
>
> The variable has been registered to the GC as suggested in the  
> README.EXT:
>
> 	rb_global_variable(&sc_object_hash);
>
> An objc object is associated to a new ruby object (the ruby version  
> of the objc class) this way:
>
> 	node = [[SomeClass alloc] init];
> 	VALUE rb_obj = common_init(klass, nil, node, argc, argv, YES);
> 	common_link(node, rb_obj);
>
> common_init is a function defined as follows:
>
> VALUE common_init(VALUE klass, cocos_holder **ret_ptr, id object,  
> int argc, VALUE *argv, BOOL release_on_free) {
> 	VALUE obj;
> 	cocos_holder *ptr;
> 	if (release_on_free)
> 		obj = Data_Make_Struct(klass, cocos_holder, 0, common_free, ptr);
> 	else
> 		obj = Data_Make_Struct(klass, cocos_holder, 0,  
> common_free_no_release, ptr);
> 	ptr->_obj = object;
> 	rb_obj_call_init(obj, argc, argv);
> 	if (ret_ptr != nil)
> 		*ret_ptr = ptr;
> 	return obj;
> }
>
> and common_link is an inline function:
>
> static inline void common_link(id obj1, VALUE obj2) {
> 	rb_hash_aset(sc_object_hash, INT2FIX((long)obj1), obj2);
> }
>
> Some times, the objc framework will call a method in the objc  
> object. When this happens, I need to call the proper ruby method in  
> the corresponding ruby object:
>
> - (void)someMethodCalledByTheFramework {
> 	VALUE rb_obj = common_link_ref(self);
> 	rb_funcall(rb_obj, id_cb_on_enter, 0, 0);
> }
>
> common_link_ref is the counterpart of common_link (basically calls  
> rb_hash_aref on the same hash)
> The thing is, that the rb_obj is crashing the ruby interpreter. If I  
> try to call any method on it (even inspect) I get a bad access  
> error. It was working with a ruby 1.8 version, but now that I've  
> ruby 1.9, it refuses to work... Any idea of what I could be doing  
> wrong here?
> Is there a better way to link a ruby object with a c pointer? I need  
> to get the associated ruby object to a given objc object. Not the  
> other way around (which is easy using Data_Get_Struct)... that's why  
> I'm using a hash table.


thanks,
-- 
Rolando Abarca M.