Bugs in java.util.ArrayList, java.util.Hashtable and java.io.ByteArrayOutputStream

[Martin Buchholz]

On Fri, Apr 16, 2010 at 03:17, David Holmes <David.Holmes at oracle.com> wrote:
> Hi Martin,
>
> Martin Buchholz said the following on 04/16/10 16:09:
>>
>> I recently discovered another place to handle huge arrays better - in
>> AbstractCollection.
>> I've put those changes into
>> http://cr.openjdk.java.net/~martin/webrevs/openjdk7/ArrayResize2/
>
> I don't understand what you are doing here:
>
> 194      * The maximum size of array to allocate.
> 195      * Some VMs reserve some header words in an array.
> 196      * Attempts to allocate larger arrays may result in
> 197      * OutOfMemoryError: Requested array size exceeds VM limit
> 198      */
> 199     private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
>
> On 32-bit you can't get anywhere near this limit. On 64-bit Hotspot
> currently allows you to allocate the entire array up to Integer.MAX_VALUE
> elements for types <= 32-bit; and MAX_VALUE-3 for 64-bit.
>
> Regardless this is VM specific and I don't see what purpose this serves.
> ???

I'm trying to avoid OOME due to exceeding the MAX_VALUE-3 limit
on a 64-bit VM,
when the number of actual elements is far smaller,
say 75% of MAX_VALUE.

Yes, you can think of this as a VM-specific bug workaround.

Martin