Subj : Re: JS_AddRoot & finalize problem
To   : anton muhin
From : Brendan Eich
Date : Thu Jul 22 2004 01:22 pm

anton muhin wrote:
> Hello, dear gurus!
> 
> I have the following problem that I still cannot solve after googling & 
> documentation reading.
> 
> I want to store in private data a reference (intenationally vagous term) 
> to JS Array. Here the way I go:
> 
> In construct object:
> 
>         JSObject * const a = JS_NewArrayObject(cx, nElements, elements);
> 
>         JSObject * * root = new (JSObject*)(a);
>         JS_AddRoot(cx, root);
> 
>         if (!JS_SetPrivate(cx, obj, root)) {
>             JS_RemoveRoot(cx, root);
>         return JS_FALSE;
>         }
> 
>         return JS_TRUE;
> 
> In finalizer:
> 
>         JSObject * * root = (JSOBject**)JS_GetPrivate(cx, obj);
> 
>         JS_RemoveRoot(cx, root);
> 
>     delete root;
> 
> However, in this case finalizer isn't get called!!!


The GC root protects the array, and I bet you have a reference from an 
element in a (one of the jsvals in the |elements| vector in your code) 
that refers to |obj|, directly or indirectly.

Instead of using a root *and* private data, you should simply store the 
array object, |a|, be a slot in the object.  You don't need to allocate 
the private data slot, so remove JSCLASS_HAS_PRIVATE from your JSClass 
flags.  Instead, add JSCLASS_HAS_RESERVED_SLOTS(1), and use JS_Get- and 
JS_SetReservedSlot with reserved slot index 0.  Don't forget to use 
JSVAL_TO_OBJECT on Get and OBJECT_TO_JSVAL on Set.

/be

.