RFR: 6260652: (coll) Arrays.asList(x).toArray().getClass() should be Object[].class

[Martin Buchholz]

On Tue, Jun 30, 2015 at 3:02 AM, Paul Sandoz <paul.sandoz at oracle.com> wrote:

>
> On Jun 26, 2015, at 11:54 PM, Martin Buchholz <martinrb at google.com> wrote:
>
> > 10 years later ... still asking for approval to commit.
> >
> > https://bugs.openjdk.java.net/browse/JDK-6260652
> >
> http://cr.openjdk.java.net/~martin/webrevs/openjdk9/Arrays.asList.toArray/
>
> +1.
>
> This is probably why there is still the following code in ArrayList:
>
> public ArrayList(Collection<? extends E> c) {
>     elementData = c.toArray();
>     if ((size = elementData.length) != 0) {
>         // c.toArray might (incorrectly) not return Object[] (see 6260652)
>         if (elementData.getClass() != Object[].class)
>             elementData = Arrays.copyOf(elementData, size, Object[].class);
>     } else {
>         // replace with empty array.
>         this.elementData = EMPTY_ELEMENTDATA;
>     }
> }
>

I recall also being the author of that comment.

I suspect we cannot remove this check,


Agreed.


> but we could update the comment referring to JDK-external collection
> implementations.
>
>
The comment remains correct even if 6260652 is fixed.
I can't think up a clearly better one.


> I trawled through the JDK code and found one other violation of the
> toArray contract in:
>
>   com.sun.java.util.jar.pack.ConstantPool.Index:
>
>   public Entry[] toArray() {
>       return toArray(new Entry[size()]);
>   }
>

Agreed.  I'm unfamiliar with that code - it should probably be fixed in
another change.