1170216 - When using the slow-and-standard path in js::SetIntegrityLevel, don't manually call setNonwritableArrayLength afterwards

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jason Orendorff [:jorendorff]]

We have this hack:

    // Ordinarily ArraySetLength handles this, but we're going behind its back
    // right now, so we must do this manually.  Neither the custom property
    // tree mutations nor the DefineProperty call in the above code will do
    // this for us.
    //
    // ArraySetLength also implements the capacity <= length invariant for
    // arrays with non-writable length.  We don't need to do anything special
    // for that, because capacity was zeroed out by preventExtensions.  (See
    // the assertion before the if-else above.)
    if (level == IntegrityLevel::Frozen && obj->is<ArrayObject>()) {
        if (!obj->as<ArrayObject>().maybeCopyElementsForWrite(cx))
            return false;
        obj->as<ArrayObject>().getElementsHeader()->setNonwritableArrayLength();
    }

This is no longer necessary in the case where we go through DefineProperty, because with bug 1125624, DefineProperty now has standard behavior. That is: the part of the comment quoted above that refers to DefineProperty is now wrong.

Comment 1

[Jason Orendorff [:jorendorff]]

Attachment: When using the slow-and-standard path in js::SetIntegrityLevel, don't manually call setNonwritableArrayLength afterwards

Comment 2

[Jason Orendorff [:jorendorff]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/822901f56c1f

Comment 3

[Pulsebot]

Backout:
https://hg.mozilla.org/integration/mozilla-inbound/rev/ed587a5aaecf

Comment 4

[Carsten Book [:Tomcat]]

sorry had to back this out in https://treeherder.mozilla.org/#/jobs?repo=mozilla-inbound&revision=65e6e21a4725 i think that something in this push caused test failures like https://treeherder.mozilla.org/logviewer.html#?job_id=10872015&repo=mozilla-inbound

Comment 5

[Jason Orendorff [:jorendorff]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/81cc971ff1d1

Comment 6

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/81cc971ff1d1