Subj : Re: Spidermonkey:  Need a 2nd set of eyes to find what I did wrong
To   : netscape.public.mozilla.jseng
From : "Izman" <cburdon@tampabay.rr.com>
Date : Tue Sep 16 2003 11:21 am

Thank you for your help Brendan.  I am using the win32 debug build of
js-1.5-rc5a.tar.gz file downloaded from ftp://ftp.mozilla.org/pub/js/.  I
tried using the win32 release build but it crashes my app every time I try
and use a script, even though the app and js32.dll compile with no errors or
warnings.  I use VS6 and compile through the IDE.  I did make the changes
you suggested and will document them at the end of this message.  The
results I receive this time are identical to before (with the exception that
prop_one is returning -1 instead of 0 as per the new enum values).

Changes:

Added decreasing negative values to the property enum:
 enum {
  prop1 =  -1,
  prop2 = -2,
 };

Removed the JS_DefineProperties statement and changed first NULL in the
JS_InitClass statement to define properties from MyObject_properties:
JSObject *JSMyObject::JSInit(JSContext *cx, JSObject *obj, JSObject *proto)
{
 JSObject *newObj = JS_InitClass(cx, obj, proto, &MyObjectClass,
  JSMyObject::JSConstructor, 0,
  JSMyObject::MyObject_properties, JSMyObject::MyObject_methods,
  NULL, NULL);
 //JS_DefineProperties(cx, newObj, JSMyObject::MyObject_properties);
 return newObj;
}

Added error checking to the constructor and set rval to the obj:
JSBool JSMyObject::JSConstructor(JSContext *cx, JSObject *obj, uintN argc,
                                     jsval *argv, jsval *rval)
{
 JSMyObject *p = new JSMyObject();

 if (!p)
  return JS_FALSE;

 if(!(JS_SetPrivate(cx, obj, p)))
  return JS_FALSE;

 *rval = OBJECT_TO_JSVAL(obj);

 return JS_TRUE;
}

Removed the trivial "p = NULL;" statement:
void JSChar::JSDestructor(JSContext *cx, JSObject *obj)
{
 JSChar *p = (JSChar *)JS_GetPrivate(cx, obj);
 delete p;
 //p = NULL;
}


"Brendan Eich" <brendan@meer.net> wrote in message
news:3F6646D4.7030000@meer.net...
> Izman wrote:
>
> >When running a script that accesses the properties:
> >
> >        The value returned from JSGetProperty is 0 when accessing prop1
(as expected).  (i.e. "var a = myobj.prop_one;", a ends up with the value 0)
> >        The value returned from JSGetProperty is "prop_two" when
accessing prop2 (should return 1 as per the enum and property definitions).
(i.e. "var b = myobj.prop_two;", b ends up with the value "prop_two")
> >
> >
>
> What version of the engine are you using?
>
> >I am missing something obvious I think, I just need some more eyes to
look at it.
> >
> >Here is the code for the class:
> >
> >
>
> This seems based directly on the docs at
> http://sourceforge.net/docman/display_doc.php?docid=10853&group_id=50913
> as you say.  Cc'ing Franky at the last address I have for him, so he can
> make corrections per below.
>
> >class JSMyObject
> >{
> >public:
> > JSMyObject() {
> >  m_CMyObject = new CMyObject();
> > }
> >
> > ~JSMyObject() {
> >  delete m_CMyObject;
> >  m_CMyObject = NULL;
> > }
> >
> > static JSClass MyObjectClass;
> >
> > static JSBool JSConstructor(JSContext *cx, JSObject *obj, uintN argc,
> >jsval *argv, jsval *rval);
> > static void JSDestructor(JSContext *cx, JSObject *obj);
> >
> > static JSBool JSGetProperty(JSContext *cx, JSObject *obj, jsval id,
jsval
> >*vp);
> > //static JSBool JSSetProperty(JSContext *cx, JSObject *obj, jsval id,
jsval
> >*vp);
> >
> > static JSObject *JSInit(JSContext *cx, JSObject *obj, JSObject *proto);
> >
> > static JSPropertySpec MyObject_properties[];
> > static JSFunctionSpec MyObject_methods[];
> >
> > enum {
> >  prop1,
> >  prop2
> > };
> >
> >
>
> Giving tinyids negative values, starting from -1 and decreasing, is
> traditional, and allows the object to handle non-negative integer
> property ids (AKA array indexes) for different properties than these
> tinyid-named ones defined via the JSPropertySpec array.
>
> >protected:
> > CMyObject *getCMyObject() {
> >  return m_CMyObject;
> > }
> >
> >private:
> > CMyObject *m_CMyObject;
> >};
> >
> >JSObject *MyObject::JSInit(JSContext *cx, JSObject *obj, JSObject *proto)
> >{
> > JSObject *newObj = JS_InitClass(cx, obj, proto, &MyObjectClass,
> >     JSMyObject::JSConstructor, 0,
> >    NULL, JSMyObject::MyObject_methods,
> >    NULL, NULL);
> > JS_DefineProperties(cx, newObj, JSMyObject::MyObject_properties);
> >
> >
>
> This is silly, the JSMyObject::MyObject_properties array should be
> passed to JS_InitClass instead of the first NULL actual parameter, for
> the |ps| formal parameter.  That will define the properties, just as if
> you called JS_DefineProperties on the return value (the prototype object
> for the class).  There is no need for callers to do this work.
>
> > return newObj;
> >}
> >
> >JSBool JSMyObject::JSConstructor(JSContext *cx, JSObject *obj, uintN
argc,
> >                                     jsval *argv, jsval *rval)
> >{
> > JSMyObject *p = new JSMyObject();
> > JS_SetPrivate(cx, obj, p);
> >
> >
>
> This code should check for errors.
>
> More important, it must set *rval = OBJECT_TO_JSVAL(obj); in order that
> 'myobj = new MyObject' to work correctly).
>
> > return JS_TRUE;
> >}
> >
> >void JSMyObject::JSDestructor(JSContext *cx, JSObject *obj)
> >{
> > JSMyObject *p = (JSMyObject *)JS_GetPrivate(cx, obj);
> > delete p;
> > p = NULL;
> >
> >
>
> There's on point in nulling p, as it is about to go out of scope.
>
> I'm not sure what else is wrong, but please correct the above and let us
> know how things go.
>
> /be
>

.