ArrayCreate should use the default [[DefineOwnProperty]] internal method instead of Array's

Yusuke Suzuki utatane.tea at gmail.com
Sun Jun 24 08:06:56 PDT 2012


Thanks for your reply.

I filed this issue to bugs.ecmascript.org
https://bugs.ecmascript.org/show_bug.cgi?id=415

Regards,
Yusuke Suzuki

On Sun, Jun 24, 2012 at 11:59 PM, Allen Wirfs-Brock
<allen at wirfs-brock.com>wrote:

> this also should be reported to bugs.ecmascript.org
>
> This is a very good catch.
>
> Allen
>
>
>
> On Jun 24, 2012, at 6:45 AM, Yusuke Suzuki wrote:
>
> Hello everyone,
>
> In 15.4 ArrayCreate algorithm step 7, we use [[DefineOwnProperty]] of A.
>
>  Call the [[DefineOwnProperty]] internal method of A with arguments
>> "length", Property Desciptor {[[Value]]: length, [[Writable]]: true,
>> [[Enumerable]]: false, [[Configurable]]: false}, and false.
>
>
> ArrayCreate set A's [[DefineOwnProperty]] to 15.4.5.1 method in step 4, so
> step 7 calls 15.4.5.1 Array's [[DefineOwnProperty]].
>
> Array's [[DefineOwnProperty]] assumes that 'length' property is always
> set. Seeing 15.4.5.1 step 1
>
> Let oldLenDesc be the result of calling the [[GetOwnProperty]] internal
>> method of A passing "length" as the argument. The result will never be
>> undefined or an accessor descriptor because Array objects are created with
>> a length data property that cannot be deleted or reconfigured.
>
>
> But, in ArrayCreate phase (step 7), A's 'length' property is not set yet.
> Then assertion in 15.4.5.1 step 1 always fails.
>
> So we should use the default [[DefineOwnProperty]] internal method instead
> of Array's.
> I suggest modifying ArrayCreate step 7,
>
> Call the default [[DefineOwnProperty]] internal method (8.12.9) on A with
> arguments "length", Property Desciptor {[[Value]]: length, [[Writable]]:
> true, [[Enumerable]]: false, [[Configurable]]: false}, and false.
>
> Regards,
> Yusuke Suzuki
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20120625/939a36f0/attachment.html>


More information about the es-discuss mailing list