This is awesome Hannes! Thanks for getting to the bottom of this. +1
/M
> On 15 Dec 2016, at 11:48, Hannes Wallnöfer <hannes.wallnoe...@oracle.com>
> wrote:
>
> Please review:
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8171219
> Webrev: http://cr.openjdk.java.net/~hannesw/8171219/webrev/
>
> This fixes a number of bugs around the Array.prototype.shift on sparse array
> data (and its underlying dense data). Unlikely as it may seem, all these
> issues where exposed by the short test script included in this webrev:
>
> - UntouchedArrayData did not convert to a real ArrayData instance when
> ensuring place for first element (index 0)
> - Dense array data did not check their size before trying System.arraycopy in
> shiftLeft
> - Dense array data did not set the new length in shiftLeft, thereby leaving
> empty slots
> - Sparse array data did not ensure space in the underlying dense array when
> moving elements from sparse to dense in shiftLeft
> - Sparse array data did not delete new in-between elements when moving
> elements from sparse to dense in shiftLeft
> - Sparse array data did not set the length after shrinking underlying dense
> data in shiftRight, thereby creating new empty slots
> - DeletedRangeArrayData could not return the underlying data if it turned
> empty in shiftLeft, causing problems later on.
>
> I also moved the invocation of ensure() on the underlying dense array from
> SparseArrayData.ensure() to where it is actually required, which is cleaner
> and safe since underlying is a private field.
>
> Thanks,
> Hannes
