812146 - Javascript doesn't honor values set via Foo.prototype.bar

Status: RESOLVED DUPLICATE of bug 783396

(Core :: JavaScript Engine, defect)

Description

[Raimar Falke]

Attachment: test.html

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20100101 Firefox/16.0
Build ID: 20121024073032

Steps to reproduce:

Execute the script


Actual results:

hhh.align should have the value 'left'.


Expected results:

Property has undefined value.

Comment 1

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

http://software.hixie.ch/utilities/js/live-dom-viewer/saved/1914

Uncommenting the this.__proto__ line fixes the issue.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Ms2ger, is this a regression?  Regression range?

Comment 3

[Loic]

m-c
good=2012-06-05
bad=2012-06-06
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=a7a905fd70d5&tochange=6338a8988917

m-i
good=2012-06-04
bad=2012-06-05
http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=778ba119ded6&tochange=f56e2197d9cd

Comment 4

[Boris Zbarsky [:bzbarsky]]

Possibly a regression from bug 759978?

Comment 5

[Boris Zbarsky [:bzbarsky]]

Hmm.  My 2012-10-28 nightly shows correct behavior.  So does the 2012-11-14 nightly.  I do see the problem in Firefox 16.

Is this fixed on trunk?

Comment 6

[Loic]

Yes, it's fixed in the latest Nightly too (Win 7). So it's likely a dupe. I should have to test the latest nightly... :/

Comment 7

[Shu-yu Guo [:shu]]

The test is also misleading in that it hard codes the 'undefined':

    alert("Expected 'left'; get 'undefined' in FF 16; result="+hhh.align);

Anyways, this was fixed by bug 767961 (this particular case was reported in bug 783396). Is it a matter of backporting the patch?

Comment 8

[Boris Zbarsky [:bzbarsky]]

Nope.  That bug is fixed in 17, so unless we plan to backport to a 16 chemspill we're all set.  Thanks!