Subj : Re: object serialization
To   : Jens Thiele <karme@unforgettable.com>
From : Brendan Eich <brendan@meer.net>
Date : Thu Apr 08 2004 11:38 am

Jens Thiele wrote:

> currently i use (in my code):
>   ECMA_BEGIN_FUNC(hashObject)
>   {
>     ECMA_CHECK_NUM_ARGS(1);
>     if (!JSVAL_IS_OBJECT(argv[0])) ECMA_ERROR("object required as
> argument");
>     JSObject *o=JSVAL_TO_OBJECT(argv[0]);
>     if (!o) return JS_FALSE;
>     *rval=INT_TO_JSVAL(o);
>     return JS_TRUE;
>   }


My patch should work better.  Your patch will cast o to an integer type, 
shift it left, and | 1 with it to tag it as an int jsval, which might at 
the limit create an id that aliases two objects.  Very unlikely, but not 
fully general.

The patch I posted is general, because object pointers are guaranteed to 
be aligned on 0 mod 8 boundaries, so |'ing 1 loses no data; nothing is 
shifted.


> are object pointers guaranteed to remain constant during the lifetime of
> a object?


See http://lxr.mozilla.org/mozilla/source/js/src/jsapi.h#916:

/be

.