Re: [External] Re: Problem with object properties/hasOwnProperty() in Spidermonkey 78

On Tue, Feb 2, 2021 at 8:41 PM Miles Thornton <[email protected]>
wrote:

> Could it be something to do with the tiny IDs or perhaps the JSPROP_SHARED
> flag (which no longer exists in Spidermonkey 78)?
>

Ah! There used to be an old hack where properties that were both
JSPROP_SHARED and JSPROP_PERMANENT (= non-configurable) acted like 'own'
properties, exactly what you're seeing here. This was fixed a long time ago
(2011, Firefox 7), not too long after 1.8.5. See these bugs for more info:

https://bugzilla.mozilla.org/show_bug.cgi?id=637994
https://bugzilla.mozilla.org/show_bug.cgi?id=575997

Pretty unfortunate for your use case, where code depended on this :/

(Great work updating from 1.8.5 all the way to 78! That must have been very
painful..)

Jan



> Miles
>
>
>
> *From:* Jan de Mooij <[email protected]>
> *Sent:* 02 February 2021 17:26
> *To:* Miles Thornton <[email protected]>
> *Cc:* [email protected]
> *Subject:* [External] Re: Problem with object properties/hasOwnProperty()
> in Spidermonkey 78
>
>
>
> The cookbook example uses getters + JS_SetReservedSlot, I just realized
> you're probably following that part too. In that case the getter lives on
> n.__proto__ (in your example JS code) and it returns a value stored in a
> slot on |n|. Question then is what the old code was doing differently,
> maybe it did a JS_SetProperty/JS_DefineProperty somewhere?
>
>
>
> Jan
>
>
>
> On Tue, Feb 2, 2021 at 6:00 PM Jan de Mooij <[email protected]> wrote:
>
> On Tue, Feb 2, 2021 at 4:55 PM Miles <[email protected]> wrote:
>
> However, for some reason I don't understand the properties that I define
> for my class do not return true for Object.prototype.hasOwnProperty() in
> Spidermonkey 78 but they did in Spidermonkey 1.8.5.
> For example I define a Node class with properties x,y,z (and lots more...)
>
>
>
> The properties in the JSPropertySpec that you pass to JS_InitClass (the
> 7th argument?) are defined on the prototype chain. Looking at Firefox 3 era
> code that hasn't changed and the SpiderMonkey 78 behavior is what I'd
> expect.
>
>
>
> Are these getters? If not, how do you assign the 1.1/2.2/3.3 properties in
> your constructor? Can you post all the relevant code for one of these
> properties?
>
>
>
> Thanks,
>
> Jan
>
>
>
>
> To do the upgrade I have been using all sorts of macros/pre-processor
> logic so that I can compile using either the old 1.8.5 version or the new
> 78 version of Spidermonkey until we are sure everything is working.
> With the old 1.8.5 engine if I run the following code
>
> var n = new Node(1.1, 2.2, 3.3);
> for (a in n)
>         Message("  Property "+a+": "+n[a]);
> Message("  n.hasOwnProperty('x') returns "+n.hasOwnProperty('x'));
>
> I get the output
>
>   Property x: 1.100000023841858
>   Property y: 2.200000047683716
> ...
>   n.hasOwnProperty('x') returns true
>
> However, in the new Spidermonkey 78 engine I get
>
>   Property x: 1.100000023841858
>   Property y: 2.200000047683716
> ...
>   n.hasOwnProperty('x') returns false
>
> i.e. In the new Spidermonkey 78 engine I can still enumerate over the
> properties but some some unknown reason the properties are not defined in
> this class. Presumably the engine thinks they are somehow being defined in
> the prototype chain somewhere else...
> There are differences as to what is exactly being executed in the
> different engines due to my macros but I'm running the same basic code with
> JS_InitClass etc.
> My class stores private data and I am setting JSCLASS_HAS_PRIVATE
> My properties are defined with the flags JSPROP_ENUMERATE|JSPROP_PERMANENT
>
> No doubt I'm (yet again) being stupid and missing something obvious but I
> can't for the life of me see what the problem is.
> Can anybody help?
>
> Many thanks in advance for any assistance
>
> Miles
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